This section is for attacking a planet from orbit. The next section is for attacking a planet by ground assault.

After all the interplanetary battles are over, and the defender's space fleets have been reduced to ionized plasma or fled in panic, the pendultimate stage is entered. The defenders orbital and planetary fortresses have to be neutralized, or at least neutralized enough so that ground troops can be inserted to set up a beachhead.

But please understand that bombing a planet back into the stone age is something that makes more sense in simplistic space operas, not in realpolitik.


A consideration for this:

If warfare is about causing the maximum destruction, these space siege scenarios make sense.

If warfare is about achieving political objectives by other means, you need to either leave someone to negotiate the surrender with, or leave something worth occupying.

If you're looking for numbers of boots on the ground to do occupation, look at the rules in Squadron Strike, which I had vetted by people who teach the US Army occupation duty and body counts.

One of the problems with wargames on this scale is that they're usually divorced from realpolitik.

A good way to illustrate this is that if the real world worked like most space gamers think planetary conquest worked, we'd'v'e given India a northern coast by making sure that Afghanistan had a mean altitude of 200 meters below datum...

Ken does have a good point. The motivation of the invaders puts limits on the allowed invasion techniques. If the invaders want slaves, it is counterproductive to kill every living thing on the defending planet. If the invaders want real estate, it is counterproductive to dust the planet with enough radioactive material to render it uninhabitable for the next ten thousand years. And so on.


The further underlying problem is: what do the aliens want? What is there that's easier to get by invading than by mining elsewhere in the solar system/local group/galaxy? The objective drives the means of invasion. Political domination is most easily achieved through infiltration — many politicians are easily bought or controlled through a combination of threats and gifts. (As Winchell posted while I typed!) Objectives beyond that seem like more trouble than they are worth.

James Sterrett

The lack of a logical reason for invasion is up to the author to devise a solution for. Some of the motivational questions can be side-stepped by assuming the invasion is not an alien one, but instead a hypothetical human interstellar empire attempting to invade a human colony world. The motivation of the empire can be something stupidly human like "gotta collect 'em all!". This is actually the motivation in Larry Niven and Jerry Pournelle's The Mote In God's Eye. In that novel, there once was a loosely allied human interstellar empire that collapsed in a bloody secession war. The new imperium rose from the ashes, grimly determined that such wars will not happen ever again, and all human worlds must be incorporated into the empire with no exceptions.

If one must have aliens invading because they want some crucial resource, I like to use an analogy. Ordinary resources are not worth it. I don't care what you saw in the TV show V, Markus Baur points out that aliens invading Terra to steal our water makes about as much sense as Eskimos invading Central America to steal their ice. The same goes for gold, uranium, or our women. But what if we hand-wave an unknown resource, something that our scientists have not even discovered yet? (Wow, Zzazel! Their planet is incredibly rich in polka-dotted quarks!)

Then us poor humans will find ourselves in the same spot as a primitive African tribe who does not understand why these Western stranger want to bulldoze their village in order to dig up the dirt. The westerners tell the tribesmen that the dirt is called "Coltain", from which they can extract something called "Tantalum", which is absolutely vital for something called a "Cell Phone." But to the tribesmen, it looks just like the same dirt that is everywhere else, and more specifically, in places that are not under their beloved village. This causes hard feelings, but unfortunately the westerners have something else called "automatic rifles".

Orbital Bombardment

For an in-depth look at the topic, go to the indispensable Future War Stories.

If the concept of a huge cannon indirectly attacking targets over the horizon is "artillery", the concept of attacking planetary ground targets from orbit is "ortillery." (term was invented by Game Designer's Workshop)

While it is possible to target the enemy even if the only friendly observers are in orbit, accuracy will be much improved if there is a human or robot on the ground close to the target giving target coordinates. These are called artillery observers, spotters, forward observer, fire support specialist, or fister. Though I suppose in this case they will be called ortillery observers instead.

Of course ortillery shares with artillery the ever-present danger of "friendly fire. If your army units are on the planet battling enemy units, and you have ortillery assets in orbit, often you will need to call down ortillery strikes on hostile positions. But there are many assorted failure modes that will result in the strike hitting your units instead. Weapon malfunctions, ortillery operator mistakes, inaccurate target coordinates, there are many opportunities for things to go badly wrong.

At the basic level one drops nuclear warheads. Next one uses kinetic energy weapons such as Project Thor or The Moon is a Harsh Mistress. Next is Colony Drop. Next is Asteroid Bombardment. Next is Relativistic Weapons. Finally there is the Planetary Nut-Cracker.


“You’re Liiriani, yes?” The recruiter eyed the tattered uniforms on those crowding into his prefab. “Ex-military. Wait… you’re Temple Guard? The ones left behind after the fall of Mantaniir?”

“Yeah. I was at Mantaniir. We all were.” The scarred veteran’s lip curled, and he spat. “Proud Mantaniir. Glorious Mantaniir. Mantaniir the Unfallen, Guardian of the Holies, all of that. Well, it didn’t fall, or we’d be dead. It was swept aside like it was nothing.”

“The first day could have been the last day. We —“

…were prepared, we were ready, we were the last line of defense for Iliir itself, and we knew they were coming at dawn. They’d told us that much. But we heard nothing. Saw nothing. Not until dawn.

We’d never fought a space war before. No-one understood what it meant that we’d lost the high orbitals. Not until the k-rods started falling, and then it was too late to help us. The minefields down-valley went in the first wave — to give us time to see what was killing us. The flak towers went in the next, along with communications and sensors. Then they started drunkwalking their shots around the valley, blasting walls, barracks, everything left of the fortress flat. What was left of us had run for the bunkers by then, and down through them into the deep tunnels. Couldn’t so much as get a shot off. We were down there for days — any time someone made a run for it, or poked so much as a nose-tip above ground, they dropped a k-rod on them. We had no power — if any generators started up, that bunker got a k-rod within minutes. Just hiding in the dark.

And then the machines hit us, wolves and spiders. From both sides — we heard later that their stormtroopers bypassed us and dropped on Iliir directly. Wolves, the little ones, ‘bots that run in packs, wall, ceiling, or floor, see in the dark, spit bullets or tear a man’s leg off themselves. And then the spiders, big eight-legged bastards with fire and cutting torches and rockets. All howling to each other like the gods below. And they wouldn’t die! Enough explosive might stop one, but if it wasn’t torn apart, it’d fix itself — or the rest of them would — and come after you again.

So we surrendered. The spiders herded us outside again, up among the craters, and fenced us in with electrowire. A couple of us tried to make a break for it. They didn’t get past the perimeter. Spiders didn’t care — they just sat there watching us, day and night. A couple of days later, one of their armor boys came by to look us over, and left us a crate of rat-bars and a medkit. Then he left us there with just the spiders to watch us. That was the only enemy we saw in the entire battle.

Two weeks later, we got word that the war was over, the Council had been captured, surrendered, were killed, one of those. The spiders all marched back into a shuttle and left us alone, then, so we scavenged what we could, tried to stay alive. A week after that, the new Council had all of us who’d let Iliir fall through our ‘heretical incompetence’ shoved aboard an old ore freighter and dumped us on this craphole planet.

“— are what’s left of the Liirian Temple Guard, yeah. Seventh Fist Ileer, commanding. And me an’ the boys’ll fight for you. Nothing else left for us now. But only if we’re fighting men. Nothing that don’t bleed and won’t die.”

— Sagivv’s Company recruitment interview, Márch, eight months after the Liir Conflict


The entire cost analysis raises the question of the alternative to invasion.  The basic strategy is to destroy the planet’s orbital defense and force the defender to surrender under threat of bombardment.  If the defender refuses, the attacker can land forces with impunity and support them with orbital bombardment.  The options for bombardment are the same as for normal space warfare: lasers and kinetics.

Lasers have a number of excellent qualities for attacking surface targets.  First, they respond at the speed of light, so troops on the ground don’t have to wait very long for fire support, and any potential target can’t move out of the way.  Second, their accuracy is very good, which is useful when attacking targets that are in a populated area.  However, lasers also have their drawbacks.  First and foremost, the atmosphere absorbs frequencies above the visible spectrum quite effectively, preventing lasers operating in those frequencies from attacking surface targets.  As such frequencies are the most efficient for attacking other spacecraft, it is entirely possible that specialized bombardment craft would be required.  While some lasers (such as FELs) can alter their frequency, the same does not apply to the optics involved, making such capability superfluous.  Secondly, the laser is a line-of-sight weapon, and is affected by the distance it must travel, both in total and through the atmosphere.  This sets tradeoffs between accuracy and time on station.  A laserstars in low orbit will obviously have the smallest spot sizes and best pointing accuracy, but it only sees the target for a few minutes on each pass.  Even when it can see the target, its low altitude means that for a significant portion of its orbit it will be shooting through a lot of the atmosphere.  Furthermore, the planet’s rotation will ensure that the next pass will have a groundtrack well away from the target (unless it is located on the equator or at the poles), which limits availability to a pass or two a day.  

Higher altitudes have lower accuracy due to increased range, but greater availability per pass, thanks to the higher angle.  Moreover, the orbit can be made elliptical, which ensures that more of the orbit can be spent over the target.  The theoretical optimum, ignoring the effects of range, is a geostationary orbit, which keeps the ship directly over the area of interest.  The angle of fire through the atmosphere is a potential problem when shooting at higher latitudes.  This can be partially solved through the use of Molniya orbits, which give improved coverage in such areas.  Targets near the pole do not suffer the normal problems of groundtrack movement, as the target is close to the groundtrack no matter what.

The use of multiple laser platforms can solve many of these problems, and the question then becomes finding the balance between coverage and the minimum number of platforms.  As a first approximation, somewhere between 12 and 24 bombardment platforms will be required for constant global coverage, although less could be used if stationed in very high orbit.  However, coverage itself might not be sufficient, particularly in hotly-contested areas, where multiple platforms would likely be required at all times.  Significant study has already been done in this area (although done with respect to missile defense instead of planetary bombardment, many of the underlying principles apply) and the author will not investigate that topic further.

Before a discussion of kinetic bombardment, a basic treatment of the projectiles used (orbit-to-surface kinetics, or OSKs) is in order.  A general rule for OSKs is that the area density will need to be at least 10 tons/m (strictly speaking, the area density needs to be at least that of the atmosphere of the target body, and the numbers given are for Earth).  If the area density is below this threshold, the object will reach the ground at low velocity, while objects with area densities higher than 10 tons/m2 will still be moving quickly at impact, making them potential weapons.  To put that into perspective, an OSK made of iron will need to be about 1.27 m long to achieve the required area density (independent of diameter) while one made of tungsten will only need to be .52 m long.  This length in turn sets the minimum feasible diameter to avoid buckling, and ratios of 20 or 30 to 1 are probably feasible, giving a minimum mass on the order of 5 kg for the tungsten rod and 14 kg for the iron.  Buckling is unlikely to be a design driver, however, as a shape with a flared base is more stable on entry.  A larger OSK will, all else being equal, be more efficient than a smaller one, retaining more of its mass and velocity on impact.

Another potentially serious problem is entry heating.  An OSK depends upon retaining as much of its velocity as possible, which in turn means that it will be receiving large heat loads when it is low in the atmosphere.  When dealing with the heat loads present in OSKs, ablation will occur, and the projectile must be carefully designed to avoid having said ablation destroy its aerodynamic characteristics.  This problem could also occur if the projectile was damaged, which would ease the problem of surface defense.  If the projectile successfully impacts the target, it will tend to penetrate and bury itself in the target, limiting damage to the surrounding area.  In fact, this effect has been compared to a shaped charge.

All of the above applies mostly to OSKs that are long in proportion to their diameter.  If the projectile is instead about equal in length and diameter, it will tend to produce a crater and do more damage to the surrounding area.  The problem, however, is that this requires a large projectile.  For tungsten, the OSK will need to mass approximately 2.7 tons for cratering to occur, while an iron projectile will need to be 16.1 tons and a typical rocky projectile (3 g/cc) will be about 110 tons.  It should be noted that even for cratering kinetics, the damage is still downwards and outwards, which is not optimal for area effects such as attacking troops.  

It appears that the best way to achieve area effects with OSKs is to intentionally break up the OSK near the ground, producing something akin to a meteor airburst.  The best-known example of this phenomena is the Tunguska Event of 1908, but similar meteor “explosions” occur frequently.  The Chelyabinsk Meteor in February of 2013 is another excellent example of a projectile producing bomb-like effects when it breaks up, although it was much larger than would be practical for military use.  What occurs is that the sudden transition from a single, low-drag object to a large number of small, high-drag objects dumps a large amount of energy into the atmosphere in the form of heat, which produces effects akin to an explosion.  The exact form and magnitude of this effect is uncertain, but it appears that a fireball would be formed and would continue on the course of the OSK.  There would also be some blast, but the exact dynamics of the outcome are currently unknown to the author.  Either the blast or the fireball would be useful against area targets such as troops or light vehicles, which traditional OSKs are largely ineffective against.

While the OSK is in the lower atmosphere, it will be sheathed in plasma due to its velocity.  This prevents both the use of onboard sensors and communication with the outside world (although there have been suggestions that communications could be made possible).  This renders traditional OSKs useless against maneuvering targets, as they are, at best, inertially guided for the last few minutes of their flights.  It is possible that the plasma sheathe will provide protection against lasers, but the magnitude of the effect is unknown.

This raises another option, an OSK that intentionally dumps most of its energy and finishes its flight at only 2 km/s or so.  This actually increases penetration, and allows guided projectiles to be used.  Some form of heat shield would be required, but that is a fairly simple matter to build.  This sort of kinetic would be useful against targets like tanks, particularly if deployed from an “Orbital Death Pod” of some sort.  Other types of conventional munitions could also be carried in the ODPs, such as cluster munitions, nuclear weapons (although most OSK research is based on ICBM RVs) or even autonomous UAVs.  The main drawback to this type of OSK is that it is somewhat more vulnerable to planetary defenses, as it sheds most of its speed before impact, which potentially puts it in the kill envelope of many SAMs.  They are, however, less vulnerable than manned drop pods, as they can decelerate much more quickly, and thus hold their velocity lower in the atmosphere.

The deployment of OSKs is subject to some of the same constraints of orbital mechanics as are laser bombardment platforms, but there are significant differences in the effects of said constraints.  First off, OSKs, unlike lasers, do not have instant response times.  Times as low as 12 minutes have been cited, but these require large numbers (40-150) of satellites in low orbit to achieve continuous coverage, and the projectiles will enter the atmosphere at low velocity, reducing lethality.    A requirement for continuous coverage obviously does not apply for strategic bombardment, but it does suggest that small sub-busses might be used for ground support.  If the launching platform is at an altitude of 6000 km, the flight time will be approximately 75 minutes, while a geostationary launcher will have a flight time of about 12 hours, although these can be reduced somewhat with more delta-V.  The delta-V requirements for deployment vary significantly, depending on range and entry angle.  A high entry angle is desirable, to minimize the distance traversed in the lower atmosphere, but requires more delta-V than a shallow trajectory.  

Crossrange is another serious concern, and would require yet more delta-V.  The exact magnitudes involved vary significantly with the initial orbit and the time between launch and impact.  See Appendix B of Space Weapons, Earth Wars for more details.

All of this suggests that large rail/coilguns might be the weapons of choice for general planetary bombardment, massive concentrations of projectiles might not be necessary and the savings over missiles could be substantial.  The delta-V requirements (generally somewhere between 10 and 15 km/s) are well within the capabilities of coilguns, and the logistics advantages would be substantial.

The tactics required to neutralize planetary defenses (see Section 4) will vary based on the type of defense.  While a number of systems are fixed, and thus can be dealt with via massive firepower, mobile systems are a much tougher target to handle.  Hunting mobile targets is quite likely the only place where any sort of ground forces have a place.  These would be small teams, similar to the LRRPs (Long Range Reconnaissance Patrols) of Vietnam, tasked with locating hidden missile launchers (likely the truck-mounted missiles discussed in Section 4) and reporting their location to the bombardment forces.  It has been suggested that these teams instead be used to attack the launchers directly, but there are three major drawbacks to this.  The first is that the logistics burden of moving people is significantly higher than that of moving kinetics, and lasers have very low logistical requirements.  Even with low casualty rates, the mass economy of this strategy is dubious in the extreme.  Secondly, even if the mass efficiency is slightly better, the fact that human casualties are part of this scheme is likely to doom it.  Lastly, it is impossible to directly tell what gave a position away from a kinetic strike, but a ground raid is quite obvious.  The countermeasure is thus to move hunter-killer teams to the area and guard the other launchers.  If a kinetic strike takes out a platform, the defender has to decide between looking for LRRPs (or UGVs), looking for UAVs, putting more camouflage up, trying for better indirect camouflage (operational patterns and radio discipline, for instance), or hunting for spies.  It should be noted, however, that such teams more or less require low-orbit fire support, given the time lag in kinetic drops from high orbit.  

There might be an occasional target that cannot be killed directly from orbit, but there are several ways of dealing with such targets.  One possibility is a weapon similar to the W54Davy Crocket” atomic rocket launcher of the Cold War.  This has the advantage of operating outside the envelope of most defensive systems deployed against orbital attack.  The team operating it would still have the difficult task of getting it in place and getting away, but the chances of doing so are probably fairly good.  Another option is a cruise missile dropped well away from the defenses, which then flies in on its own.  Some versions of the Tomahawk cruise missile have ranges as long as 2,500 km, while the AGM-129 ACM has a range of 3,700 km.  These are significantly larger than the danger zone of even long-range SOMs, giving the missile more or less free entry into the atmosphere.  The warhead could be either nuclear or conventional, as required by the nature of the target.  Such missiles would remain vulnerable to air defenses, but their small size, relatively low cost, and lack of need to return to orbit make them an attractive proposition.  It has also been suggested that commando teams could be used directly against certain strategic targets, generally command and control, but the ease with which these can be defended against such attacks makes them a dubious proposition compared to orbital or remote bombardment.

Redirected asteroids are often proposed as a means of attacking planetary targets.  The usual logic goes that they are “free” and thus the cheap way of destroying a planet.  From a military point of view, however, asteroids are nearly useless.  First off, small asteroids are not suitable for use in this manner.  While purpose-built kinetics can be used to hit targets with minimal collateral damage, any natural asteroid of comparable size will either slow down to the point of uselessness or disintegrate in the upper atmosphere.  Larger asteroids (>1 km) are useless except for ecocide.  While this might occasionally be the goal, it falls outside the scope of this paper.  A medium-sized asteroid, such as the aforementioned Chelyabinsk Meteor, might have some uses, but it would be unreliable, and difficult to use, as that meteor is estimated to have mass 11,000 tons.  The damage mechanism would be the same as that proposed above for airbust kinetics, except for a lack of precise control and a much higher lower size limit.  (Oddly enough, when RAND studied this issue for Space Weapons, Earth Wars, they noted the use of asteroids for airbust, but neglected to apply it to man-made kinetics.)

The biggest problem with asteroids is their ease of use relative to nuclear weapons.  Hauling an asteroid from the belt is quite difficult, and truly silly.  More plausibly, there are a significant number of earth-crossing asteroids which might be suitable for this use.  The number available (and thus the minimum lag time) is based upon the amount of delta-V that can be applied, and when.  For example, 10-meter iron asteroids (about the minimum size that can be considered as a useful weapon) hit the Earth about 3 times a century.  If one is diverted that passes within 1.35 light-seconds (the distance of the moon), there are about two a week available.  Larger objects will pass by less often, although stony asteroids become viable weapons as the size increases.  These types of asteroids probably have windows of a few months.  Particularly in the case of smaller asteroids, the primary delay driver will be the diversion process.

The diversion itself will not take that long.  With a few months lead time, the delta-V required is generally in the tens or hundreds of m/s, which given projected mass driver technology would involve the use of 30% of the object as remass at the upper end.  The power requirements will likely force this acceleration to be made over a fairly long period, pushing the lag even higher.  If the asteroid is diverted later, the delta-V requirements skyrocket.  At one month out, 1 km/s is passed, at which point about half of the asteroid is being used as remass.

The time lag is the greatest drawback to the use of asteroids for any sort of bombardment.  Assuming that the defender is somewhere near technological parity, he will be able to deflect away any asteroid you can send towards him given enough time.  Depending on the exact nature of the asteroid in question, the time he has available could vary significantly.  If the incoming asteroid is intended to take out a city, even a small deflection quite late would send it over rural or uninhabited territory, greatly reducing damage.  This forces the attacker to guard the asteroid for months while it is moved into position, and the logistics costs of doing so are quite high.  There is a significant economy of scale in bigger asteroids, however.  They require the same protection as the smaller ones, and the cost scaling of the mass driver will be negligible compared to the cost of the naval forces deployed to protect it.  Furthermore, the asteroid itself cannot be deflected as easily at the last instant, either through a last-ditch effort to break through the fleet guarding it or after the fleet has pulled off to avoid following it into the atmosphere.

The above concepts are often associated with the name ‘Project Thor’, which is believed to be the Air Force’s original study of the idea of orbital bombardment.  However, the author has found no reason to believe this to be the case.  There was an official Project Thor, but it was a study of fragmentation ballistics, and had nothing to do with orbital bombardment.  Moreover, research has been unable to turn up any official studies of orbital kinetic bombardment that are above the level of that done in Space Weapons, Earth Wars.  The name Project Thor appears to have originated with Jerry Pournelle, who thought of the concept while working in operations research, and appears to have popularized the term.  The author believes it was his personal term, and in no way official.

The primary alternative for destroying strategic ground targets is nuclear weapons.  The cost of a comparable nuclear weapon is almost certain to be no greater than that of the asteroid-deflection operation, particularly when the fleet operations costs are factored in, and depending on the technologies involved, it is very likely to be significantly less.  The nuclear weapons are also more accurate and predictable, and have none of the lag problems associated with asteroids.  The only area where an asteroid wins over a nuclear weapon is in dealing with terminal defenses.  While a nuclear weapon (which would almost certainly resemble an ICBM RV) can be engaged and destroyed by ABM-class weapons, an asteroid would be virtually unaffected by any defenses after it entered the atmosphere.  A nuclear weapon fired at it might be able to disrupt it and cause it to dump its energy high in the atmosphere, but that might still have serious climatic effects, as well as the possibility of some damage on the surface, and the damage done by the nuclear weapon itself.

All in all, the disadvantages in redirecting even NEOs are likely to outweigh any possible cost advantages.  The only practical reason to do so might be for purposes of psychological effects.  The defenders would know exactly how difficult it is to use an asteroid as a weapon, and the fact that it was done anyway would send a very clear message.  Another vaguely possible cause would be a total ban on the use of nuclear weapons, but given that such a ban shows no signs of happening today, and would be next to impossible to enforce, and that nuclear-electric drives are assumed throughout this paper, this is unlikely.  As Space Weapons, Earth Wars put it: “Because much cheaper, more responsive weapons of mass destruction are readily available, this one is likely to remain safely in the realm of science fiction.”  For a more irreverent treatment of the issue, Google “Rocks are not free”.

A related issue that deserves a brief mention is the use of spacecraft as weapons against ground targets.  This is unlikely, to say the least.  As mentioned above, a sectional density of 10 tons/m2 is required to make it through the atmosphere with a reasonable amount of velocity remaining.  While common ships might reach this threshold, they are almost certain to fail structurally long before impact.  When they break up, the pieces are unlikely to retain sufficient sectional density to reach the ground.  The result is a high-altitude airburst, which, given expected vessel sizes, is unlikely to do significant damage.  It has even been suggested that vessels be intentionally designed to break up on atmospheric entry to reduce the risk to people on the ground.  Even if the ship was theoretically capable of doing damage to ground targets, there still remains the issue of actually hitting the target, and the prospects on that front are dubious at best.

The basic strategy of the attacker during a planetary invasion is to destroy enough of the surface defenses by bombardment to be able to dictate terms to the defender, or support troops should that be necessary.  The mechanism by which to do this is more or less that of moving into range and dueling with them.  This in turn reveals the locations of the fixed defenses, and forces the mobile ones to either fire their missiles (which then renders them ineffective for the rest of the siege) or risk revealing their location.  The weapons can be forced to fire to protect targets on the ground, as the spacecraft will have to fight them instead of conducting its bombardment mission.  The attacker would continue to do so until he had reduced the defenses to a point that he could seriously consider landing troops. This would not be the point at which all of the defenses had been eliminated, but the point at which the attacker could provide cover for a landing from his fleet, and do so with confidence that he could protect both his fleet and the drop pods.

Before the actual landing, the attacker would probably call the defenders and offer good terms for them if they were to surrender at this time, and tell them that the terms would become much worse if the landing went through.  Most defenders would probably surrender at this time, as they can no longer expect to resist with hope of long-term success.  If they refuse, they either consider death better than capitulation, or believe that they can defeat the landing.  At this juncture, a reputation for honesty and honor would greatly help the attacker.  Conversely, if the defender waits until the attacker begins to land and opens fire, the attacker will probably show no mercy and destroy the defender’s cities.  This holds the leaders hostage to the people, ensuring they go through with their side of the bargain.

It has been suggested that in some cases, the attackers cannot offer terms, primarily due to unreasonable political leadership.  This situation is outside the scope of this paper, but the other side of the same problem, an unreasonable defender, is not.  In this case, clearing as much of the orbital defenses as possible is vital, so that the ground troops can have access to continuous space support.  This should serve as a massive force multiplier, allowing a reasonable amount of troops to capture the world.  Occupation is likely to be a much bigger problem, but it is one that lies outside the scope of this paper.

by Byron Coffey (2016)

(ed note: this game is a sequel to the tabletop game StarForce: Alpha Centauri. Due to the odd background universe, literally the only valuable thing a planet has to offer is the colonists. Therefore in the game StarSoldier, the soldiers have to avoid causing civilian casualties at all costs.)

"Teleships" are starships, their faster-than-light movement is called "shifting". A "StarGate" is a sort of orbital fortress defending the planet from invading Teleships. The "Heissen Field" is a weapon that allows starships in orbit to render everybody on the planet unconsious. Everybody that is unprotected, defending StarSoldiers are unaffected.)



Undisputed control of local space is a doctrinal prerequisite to any attempt by a StarForce to induce a Heissen Field and land StarSoldiers on an unfriendly planet. It is therefore usually the case that only one side—the side attacking, in the strategic sense—that will be able to call upon off-surface support. And being extremely destructive, Orbital Ground Support is only utilized in extreme circumstances. In any event, the provision of support bombardment by even "unopposed" StarForces is somewhat problematic, as the presence of automated and StarSoldier manned defensive missile batteries and laser banks on the surface of the planet has the capacity to make things difficult for orbiting Teleships. A StarForce may not move or defend itself telesthetically within the proximity of the gravity fields which characterize solar systems, and so is dependent upon "conventional" kinetic drive (Energy Modulation Packs) and computer-directed laser interception for those tasks. Faced with a powerful surface defense utilized to capacity, Teleships generally adopt variable geometary orbits, which allow them to approach closely to the planet for brief and unpredictable passes. At least two StarForces (eight TeleShips) are required to provide effective ground support under such circumstances.


The rest of the city seemed to have died of neglect rather than violence. It certainly hadn't been bombed out. Harkaman thought most of the fighting had been done with subneutron bombs or Omega-ray bombs, that killed the people without damaging the real estate. Or bio-weapons; a man-made plague that had gotten out of control and all but depopulated the planet.

From SPACE VIKING by H. Beam Piper (1962)

The Gravity Gauge

This is sort of the outer space equivalent of holding the high ground.

Two people throwing rocks at each other is pretty much a fair fight. If one person is on a hill, they have an advantage. And if one person is at the bottom of a well, that's not fair at all. By analogy, it is beyond unfair if one person is in orbit. The lucky one in orbit does not need to use bullets, missiles or nuclear weapons; a nice selection of rocks and boulders will do. Nudge a rock hard enough to de-orbit it, and it will strike with most of the kinetic energy difference between orbit and the ground. The poor slob on the ground, however, has to use huge rockets just to boost weapons up to the level of orbital person. This is called the gravity gauge.

Please note that "unfair" does NOT mean "impossible".


     "Have you ever wondered why the Patrol consists of nothing but officers—and student officers, cadets?"
     "Mmm, no, sir."
     "Naturally you wouldn't. We never wonder at what we grow up with. Strictly speaking, the Patrol is not a military organization at all."
     "I know, I know—you are trained to use weapons, you are under orders, you wear a uniform. But your purpose is not to fight, but to prevent fighting, by every possible means. The Patrol is not a fighting organization; it is the repository of weapons too dangerous to entrust to military men.
     "With the development last century of mass-destruction weapons, warfare became all offense and no defense, speaking broadly. A nation could launch a horrific attack but it could not even protect its own rocket bases. Then space travel came along.
     "The spaceship is the perfect answer in a military sense to the atom bomb, and to germ warfare and weather warfare. It can deliver an attack that can't be stopped—and it is utterly impossible to attack that spaceship from the surface of a planet."
     Matt nodded. "The gravity gauge."
     "Yes, the gravity gauge. Men on the surface of a planet are as helpless against men in spaceships as a man would be trying to conduct a rock-throwing fight from the bottom of a well. The man at the top of the well has gravity working for him.
     "We might have ended up with the tightest, most nearly unbreakable tyranny the world has ever seen. But the human race got a couple of lucky breaks and it didn't work out that way. It's the business of the Patrol to see that it stays lucky.
     "But the Patrol can't drop an atom bomb simply because some pipsqueak Hitler has made a power grab and might some day, when he has time enough, build spaceships and mass-destruction weapons. The power is too great, too awkward—it's like trying to keep order in a nursery with a loaded gun instead of a switch.
     "The space marines are the Patrol's switch."

(ed note: of course the gravity gauge isn't quite as much of a problem when the planetary defenses include huge laser weapons. Lasers had not been invented yet when the novel was written. But as Heinlein observes below, lasers are pretty worthless if you are being bombarded by house-sized bolders.)

From SPACE CADET by Robert Heinlein (1948)


Back in the 1950s, Robert Heinlein and others made a rather startling observation:

Robert Heinlein 1950
The most important military fact of this century is that there is no way to repel an attack from outer space.
General Thayer: The reason is quite simple. We are not the only ones who know that the Moon can be reached. We're not the only ones who are planning to go there. The race is on — and we'd better win it, because there is absolutely no way to stop an attack from outer space. The first country that can use the Moon for the launching of missiles… will control the Earth. That, gentlemen, is the most important military fact of this century.
Robert Heinlein 1965
I flatly stand by this one. True, we are now working on Nike-Zeus and Nike-X and related systems and plan to spend billions on such systems—and we know that others are doing the same thing. True, it is possible to hit an object in orbit or trajectory. Nevertheless this prediction is as safe as predicting tomorrow's sunrise. Anti-aircraft fire never stopped air attacks; it simply made them expensive. The disadvantage in being at the bottom of a deep "gravity well" is very great; gravity gauge will be as crucial in the coming years as wind gauge was in the days when sailing ships controlled empires. The nation that controls the Moon will control the Earth—but no one seems willing these days to speak that nasty fact out loud.
Robert Heinlein 1980
I have just heard a convincing report that the USSR has developed lasers far better than ours that can blind our eyes-in-the-sky satellites and, presumably, destroy our ICBMs in flight. Stipulate that this rumor is true: It does not change my 1950 assertion one iota. Missiles tossed from the Moon to the Earth need not be H-bombs or any sort of bomb—or even missile-shaped. All they need be is massive… because they arrive at approximately seven miles per second. A laser capable of blinding a satellite and of disabling an ICBM to the point where it can't explode would need to be orders of magnitude more powerful in order to volatilize a house-size chunk of Luna. For further details see my THE MOON IS A HARSH MISTRESS.

However, it might not be quite as bad as Heinlein thought.

Orbiting a string of nuclear weapons aimed at Earth would be an easy way of conquering the world. Or a Lunar missile base. This was why it was outlawed in the SALT II treaty of 1979. Robert Heinlein wrote about this in his novel Space Cadet and the short story "The Long Watch".

Or maybe it wasn't such a good idea in the first place. The blog Tales Of Future Past points out that neither the Moon nor Earth orbital bases turned out to offer any sort of advantage over surface-based missiles. Lunar bases are easy to target, require missiles with huge amounts of delta-V to deliver the nuclear weapon to the target on Earth, and will take days of transit time. Orbital bombs have utterly predictable orbits and can be seen by everybody (unlike ground based missiles), can only be sent to their target at infrequent intervals (unlike ground based missiles), and will require a deorbiting rocket with pretty much the same delta-V as a ground base missile. So what is the advantage? Please note that not all of these drawbacks apply to enemy spacecraft laying siege to Terra.

Attacking spacecraft dropping nuclear weapons would be somewhat like the situation faced by nations threatened by enemy intercontinental ballistic missiles except that in this case the weapons have no boost phase. The discredited Strategic Defense Initiative had all sorts of ideas of how to deal with the problem. For our purposes, ignore any solution that depends upon the boost phase (since there isn't any), space-based programs are "orbital fortresses", and ground-based programs are "planetary fortresses".

Rick Robinson is of the opinion that the gravity gauge is not quite as one-sided as it appears. In an essay entitled Space Warfare I - The Gravity Well he makes his case. The main point is that the orbiting invading spacecraft have nowhere to hide, while the defending ground units can hide in the underbrush.

Ah, Luke Campbell points out that I'm wrong, there will be a boost phase.


Another detail — munitions will have a boost phase, otherwise they will just end up drifting next to the spacecraft that released them. So either the spacecraft boosts the munition using a gun or cannon or coilgun or something that can impart enough delta-V to de-orbit it, or the munition de-orbits itself in a similar fashion using a rocket.


One of the great arguments for selling the space programme to the American People was that if they didn't conquer space, then someone else would and that someone would use space to start lobbing atomic bombs back at the Free World. Collier's magazine ran a major series on World War III that warned of the danger of Soviet missile bases on the Moon attacking a defenceless Earth, and the film Destination Moon claimed that the Moon had to be conquered because the nation that controls the Moon controls the world.

It wasn't just speculation either. Back in the 1950s, the prospect of an atomic Pearl Harbour from space was taken seriously by the Eisenhower administration and was one of the reasons why the launch of Sputnik in 1957 was so harrowing. It wasn't just that the Soviets had stolen a march on the West, but that they might have gained the nuclear high ground first.

At first glance, the idea of space-based weapons, whether on the Moon or in Earth orbit, seems logical enough. The bomber had revolutionised warfare; allowing armies to launch assaults out of sight of one another and made cities vulnerable to massive attacks. Space, by extension, should provide an even greater advantage. Weapons could be set above their targets indefinitely and attacking one's enemy would be like dropping stones down a well. By contrast, attacking an orbital or lunar base would require fighting against the full force of the Earth's gravity and the vagaries of the weather.

Fortunately, neither the Moon nor Earth orbital bases turned out to offer any sort of advantage over surface-based missiles, which could strike targets quickly and accurately from silos or submarines yet were easily protected or hidden. Moon bases, on the other hand, were easily targeted, required very large rockets to deliver their bombs with any speed, and an attack took many hours or even days to execute. Orbital bombs were just as bad. Low orbiting bombs only passed over their targets occasionally and predictably, and being over target in a satellite is not like being in a bomber. The bomb still had to be got to Earth and that meant either a rocket engine as large as that of a surface-based missile or having your bomb spiral gently in with all the delays and problems that involves.

By 1967, the military of the superpowers had reached the conclusion that though space might be ideal for reconnaissance and communication, it was a dud as a staging area for nuclear attack and a treaty was signed banning nuclear weapons from a place where no one wanted to put them anyway; rendering the opening space scenes of 2001: a Space Odyssey with its orbital bombs obsolete before the prints even came back from the chemists.


Luke Campbell

The case of attackers in orbit and defenders on the ground is not nearly so one-sided as one might think.

Remember — the attackers are in orbit, so their missiles and gun shells are also in orbit. the attacker needs to cancel most of their orbital velocity to put them on a highly elliptical orbit that will intersect the desired point on the planet. This can use up quite a bit of delta-V.

On the other side, the defender does not have to put munitions in orbit. He merely needs to loft them up on a sub-orbital hop that just happens to have the attacker's spacecraft smacking into it at orbital speeds. This does not always require much delta-V.

The closer the attacker is orbiting the planet, the harder it is for him and the easier it is for the defender to use kinetics. Distant orbits will be harder for the defender to reach and allow the attacker to de-orbit munitions easier — but it also gives the defender a lot of time to respond and makes the munitions hit the atmosphere faster (which tends to badly ablate away the munitions, making it more difficult for them to cause damage at the ground). Close orbits are likely to be death traps for the attacker — easy for the defender to launch munitions on sub-orbital intercept trajectories, not much time for the attacker to react to them, and expensive for the attacker to bring his own munitions to bear.

Isaac Kuo

Luke Campbell, there's no orbit from which it costs more delta-v to send munitions planet-ward than the delta-v required to send munitions on an intercept path. The situation is roughly symmetric, but the atmosphere reduces delta-v to go "downward" while increasing delta-v to go "upward".

Luke Campbell


In close orbit, if the orbiting spacecraft sends its munitions on a minimum energy trajectory to intercept the planet, it will take much longer to reach its target than a surface-launched missile will take to reach the spacecraft. In addition, this minimum energy missile can only hit things on the other side of the planet from where it is launched, so you will not have the bombarding spacecraft doing its own spotting. One might argue that this is not likely to be the case anyway, but it does detract from the usual trope of the orbiting spacecraft seeing its target and launching missiles at it.

Here are some details, assuming a 200 km altitude circular orbit around an airless Earth. A minimum energy orbit will have an apoapsis at the point of launch and a periapsis at the opposite side of the planet. It will take 43 minutes to reach its target, and will require about 1 km/s of delta-V. This gives plenty of time for the target to either move out of the way or shoot down the missile.

A surface launched missile will take 3.4 minutes to reach the spacecraft at a 200 km altitude, on a minimum energy boost of just under 2 km/s delta-V. Evasion or point defense may be possible within this time, but will be more difficult.

To match the performance of the surface missile, the orbiting spacecraft must cancel its orbital velocity of 7.8 km/s, and thus requires 7.8 km/s of delta-V. This is also roughly what it will take if the spacecraft is doing its own spotting and targeting.

Since ground launched missiles could reasonably be expected to have 4 to 5 km/s of delta-V even with chemfuel propellant, you are looking at the ability to track the target at something like 1 to 1.5 g of evasion acceleration, or reduce the time to intercept by launching faster.

Isaac Kuo

Luke Campbell, it's not necessary for the LEO spacecraft to launch with minimum energy. Like I said, the situation is roughly symmetrical. It can shoot a missile "directly" downward—that is, with the thruster pointed straight up.

In the rotating reference frame of the orbit, the spacecraft is shooting a missile straight downward fighting against 1 gee of centrifugal force. In this rotating reference frame, it's like shooting a suborbital missile downward.

Of course, the atmosphere in this case helps rather than hurts.

Luke Campbell


I will compute the orbital parameters later when I have a bit more time, but I will note that the situation you describe will not work on a world with a significant atmosphere. On Earth, for example, the projectile will slice through the exosphere and hit the mesosphere at a steep angle, rapidly getting to regions of air dense enough for the shock heating to incinerate the projectile while the ram pressure disintegrates it. Here, the atmosphere does not help. To get the atmosphere to help you need to enter at a shallow angle, where you can stay in the upper reaches of the mesosphere for long enough to let drag do its work without incinerating you. This would be something like the minimum energy solution I described earlier - or more likely an orbit with a periapsis at an altitude of 100 to 150 km or something similar.

Alternately, you can kill off much of your orbital velocity so the projectile enters the atmosphere at a much lower speed - similar to the method I described earlier, with the projectile dropping straight down.

For what it is worth, a projectile given 2 km/s delta-V straight down from a spacecraft in a circular 200 km altitude orbit above airless Earth will have a surface track distance of 781 km before impact, and will take 100.25 seconds for impact. It will hit with a speed of 8.275 km/s.

With an atmosphere, of course, it disintegrates long before reaching the ground.

Isaac Kuo

Luke Campbell, ICBM warheads reenter the atmosphere at steep angles at orbital speeds. This lets them reach their targets more quickly, which was considered important for trying to take out enemy launch sites before the enemy had time to react (by launching their nukes).


On March 1, Russian President Vladimir Putin provided details, mostly in the form of artist’s impressions, on a variety of provocative weapon systems under development. One of them, the RS-28 Sarmat, was depicted as placing a nuclear weapon into a presumably orbital trajectory that could strike targets by traveling the long way around the globe (in this case, with fictionalized land masses, but later depicted as descending on Florida).

The US State Department condemned the development of Russia's new weapon systems as violations of the Intermediate-Range Nuclear Forces (INF) Treaty but did not allege a violation of Article IV of the UN 1967 Outer Space Treaty (OST).1 Why?

The answer may be in part because, 50 years ago, the Johnson Administration set the precedent that testing such a weapon system would not be a violation when it stated publicly that the Soviet Union’s “Fractional Orbital Bombardment System (FOBS),” based on the predecessor to the RS-28, did not violate the treaty. Before and after the treaty’s signing, the administration internally debated the activities it would permit and their ability to verify compliance, ultimately concluding that the treaty was intended to prohibit a different type of weapon system.

A binding prohibition

Article IV requires signatories “not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner,” among other prohibitions. The US and USSR had already publicly stated their intention not to station nuclear weapons in space, on the Moon, or on other celestial bodies in 1963 through UN Resolution 1884, but because the 1963 statement was not legally binding, the US was not obligated to verify that the USSR was honoring the agreement. By contrast, in preparation for the legally binding 1963 Partial Nuclear Test Ban Treaty, which prohibited exo-atmospheric nuclear testing, the US deployed the Vela surveillance satellites to detect the characteristic radiation from exo-atmospheric (and later, atmospheric) nuclear explosions.

In fact, the Soviets only agreed to the 1963 proposal on the condition that measures such as pre-launch inspection of payloads would not be required, and that the US would be satisfied by using its own national technical means for verification. However, elevating the 1963 statement to a legally binding instrument raised questions about the US ability to verify that other countries were in compliance, and events soon after the signing forced them to consider what would constitute a violation.

Establishing a threshold for violation

Two incidents in 1967 forced the Johnson Administration to establish a threshold for violation of the treaty that hinged on the interpretation of placing nuclear weapons in orbit around the Earth or stationing such weapons in outer space.

The first incident was in response to a June 1967 New York Times article reporting alleged Pentagon plans to develop a nuclear-tipped orbital ABM system. The State Department, who was generally tasked with interpretation of the treaty, stated internally that such a system would violate the treaty because it permanently stationed nuclear weapons in orbit, and it would be impossible to differentiate offensive from defensive orbiting nuclear weapons.2 The explicit inclusion of nuclear weapons in Article IV in addition to weapons of mass destruction prevented the introduction a loophole that the Joint Chiefs of Staff had sought in the 1963 statement in order to allow developing just such an ABM system.3

The second incident was in November 1967—a month after Congress ratified the treaty--when Secretary of Defense McNamara announced that the Soviets had tested a FOBS. The weapon consisted of a modified R-36 missile (the R-36ORB) that placed a two- to three-megaton warhead into an orbital trajectory over the southern hemisphere in order to evade US early warning radar (and possibly ABM) systems by flying lower and approaching from the south, using a retrorocket to de-orbit itself.4 When Secretary McNamara announced the tests, he argued that they did not violate the treaty because 1) they did not involve a warhead, so no nuclear weapon entered orbit; 2) the test vehicle was de-orbited before it achieved a full orbit; and 3) weapon development was not prohibited by the treaty.5

Yet Secretary McNamara’s interpretation angered some members of Congress, who argued that the FOBS represented a violation and questioned Soviet commitment to the treaty. US allies also privately raised concerns, and US the intelligence community suggested it could presage development of a multi-orbit bombardment system. State Department officials, who had not been notified in advance about Secretary McNamara’s announcement, argued internally that nothing in the treaty limited it to full orbits. This internal discord was picked up and reported by the famous Murrey Marder at the Washington Post in a pointed piece titled “Orbital Bomb Rationalizing Jolts Officials.”6

But the State Department was overruled and subsequently adopted the administration’s position, later noting that even if the tests had involved a nuclear weapon, they would not be considered a violation because a “true” orbital bombardment system was imagined to station nuclear weapons in orbit on a more permanent basis.7 Even the name, FOBS, was carefully employed to ensure that the weapon would not be considered a violation.

So it was that the Johnson administration set the bar in 1967: violation would need to entail space-based nuclear weapons, not ground-based systems that temporarily placed prohibited weapons into orbit. This interpretation owed more to the administration’s other needs—in particular, the need for Soviet cooperation to finalize the far more consequential Nuclear Non-proliferation Treaty—than to a close reading of the text or concern about space-based weapons. However unlikely it was that space-based nuclear weapons would be deployed, government officials nevertheless dutifully prepared for verifying compliance with this prohibition.

Inferring the right to inspect satellites

The treaty does not include an explicit permission for inspection of spacecraft to ensure compliance. During negotiations in 1966, the US delegation pushed for all facilities on celestial bodies to be open to all parties, akin to the 1958 Antarctic Treaty, but the Soviets resisted on the grounds that such access could be unsafe, and that access should only be permitted on a pre-arranged, reciprocal basis. The US delegation eventually accepted this limitation under the belief that any effort to evade inspection on these grounds would be obvious.8

Neither the US nor the USSR proposed requiring or even allowing access to spacecraft in orbit, and no such measure was included in the treaty—and in fact, US negotiators were instructed to abandon the talks if access to satellites became a requirement.

As a result of this omission, the US had to establish that the treaty did not prohibit inspection of spacecraft for the purpose of verifying treaty compliance. Consequently, Johnson administration officials argued that the treaty implicitly permitted the use of national technical means to verify compliance:

Thus, provided the close inspection does not involve “potentially harmful interference with activities of other States Parties in the peaceful exploration of outer space,” there is no prohibition against such action. In this context, visual inspection would not be considered as “potentially harmful.” Furthermore, a “bomb-in-orbit” would not be regarded as peaceful and therefore there would be no restraints against inspecting it.9

A more detailed interpretation reasoned that while the treaty did not generally permit physical access to satellites, it “does not contain any provision prohibiting steps to ascertain whether there has been a violation... If any presumption against a right of inspection is raised... this would be overcome if there were strong reason to believe that an orbiting space vehicle was carrying a prohibited weapon,” at which point other rights afforded to states under international law, such as self-defense, would take precedent. Any state would be entitled to challenge a state suspected of violating the treaty, and if doubts could not be addressed, “to take appropriate steps to protect itself against the effects of a Treaty violation.”10

Looking for “bombs-in-orbit”

The administration maintained publicly that the US possessed capabilities for verifying compliance with the treaty that were “sufficient for national security.”11 But the Joint Chiefs of Staff dissented in 1966, noting that while they accepted the treaty, “the United States does not now have the capability to verify the presence of weapons of mass destruction in orbit. The Joint Chiefs of Staff are seriously concerned about this lack of verification capability, and they believe that continued effort should be expended toward its attainment.”12 Although the Air Force did possess a system for the visual inspection of satellites known as Project 437 available by at least 1965, as Dwayne Day has pointed out it had limited capabilities and was cancelled soon after.13 Their dissent may have been due in part to a belief that a binding treaty presented opportunities to advocate for systems such as the Air Force’s planned Manned Orbiting Laboratory (MOL).

A February 1967 memo to prepare for questions from Congress noted that the US could detect all satellites, including a “bomb-in-orbit,” very easily at low orbits, and that higher orbits such satellites would have comparatively long time de-orbiting times. They also noted that they had “a very high confidence of being able to detect a satellite when it is launched” and that a number of ground-based radar and laser facilities under development would add to this capability.14

The memo added, however, that distinguishing nuclear weapon-carrying satellites still posed a significant technical challenge and a disguised weapon could be impossible to be identify. As a contingency, capabilities for physical inspection of spacecraft and facilities were evaluated. The Department of Defense reported that Gemini spacecraft had demonstrated the capability to rendezvous with satellites, and proposed that the MOL could be called on to conduct inspection missions within its limited delta-V. NASA did not volunteer any specific systems but noted many difficulties if it was called on to inspect satellites, including “the availability of ‘booby trap’ devices in the spacecraft to be inspected,” and concluded that “it appears that inspection capabilities in space could be limited.”15

Interestingly, NASA also considered their ability to inspect facilities on the lunar surface, since they were the only agency with the means to do so, even though they had not yet landed astronauts on the Moon. In the extremely unlikely scenario that they would be called on to inspect lunar facilities, NASA noted that: “for the present our manned inspection capabilities are essentially limited to the equatorial plane of the moon but with an accuracy to target area which is expected to be some hundreds of feet and an extravehicular range up to one-half mile. The basic capability through lunar orbiter photographic reconnaissance seems very good, with resolution of one foot and the ability to cover any spot on the moon.”16

Despite technical limitations, the administration concluded in 1966 that they maintained capabilities sufficient for national security because ultimately:

A single weapon in space would not upset the [strategic] balance. “Bombs in Orbit” are complex weapons systems which to be practicable involve large numbers of weapons and associated supporting activities. It would be extremely difficult to conceal such a program. When viewed in this light, it is clear that our national capabilities will provide us the necessary information for protecting our security interests. The real verification question hinges on our ability to know of an adversary’s space activities in sufficient depth to take the necessary actions prior to his attaining any strategic advantage through the weapons-in-space route. This is clearly within U.S. capabilities.17

A later memo to the Secretary of Defense asserted more directly that national capabilities would ensure that compliance with the treaty could be effectively monitored and admitted that while a small number of nuclear weapons could be orbited without detection, a large number could be easily detected.18

Does the Johnson Administration’s interpretation of 50 years ago still stand? No action taken so far after Putin’s address suggests that the current administration has adopted a more restrictive stance. But how this interpretation may have changed in the intervening half century, particularly in relation to some of the proposals of the Strategic Defense Initiative, and with the emergence of new actors and technologies (and artist’s impressions), awaits further research.


  1. State Department. Department Press Briefing - March 1, 2018.
  2. Leonard Meeker to Paul Warneke, ‘Outer Space Treaty and ABM Systems,’ 7 June 1967, Legislative Background Outer Space Treaty History Box 2, Folder “The Senate Considers the Treaty and Gives its Advice and Consent,” LBJ Library.
  3. Raymond Garthoff, A Journey through the Cold War: A Memoir of Containment and Coexistence, Brookings Institution Press: Washington, DC, 2001, p. 162.
  4. Asif Siddiqi, “Cold War in Space: A Look Back at the Soviet Union,” Spaceflight vol. 40, February 1998.
  5. ‘News Conference of Secretary of Defense Robert S. McNamara at Pentagon,’ 3 November 1967, National Security File, Files of Charles E. Johnson, Box 11, Folder 4 “Bombs in Orbit – General (Ballistic missiles in orbit, FOBS, MOBS, etc),” LBJ Library.
  6. Murrey Marder, “Orbital Bomb Rationalizing Jolts Officials,” Washington Post, November 5, 1967.
  7. Dean Rusk to US mission NATO, November 1967, National Security File, Files of Charles E. Johnson, Box 11, Folder 4 “Bombs in Orbit – General (Ballistic missiles in orbit, FOBS, MOBS, etc),” LBJ Library.
  8. Arthur Goldberg to State Department, 4-7 October 1966, LBJ Library.
  9. John S. Foster, “Memorandum for the Assistant Secretary, ISA,” February 2, 1967, Legislative Background Outer Space Treaty History Box 1, Folder 12, “The Treaty is Open for Signature and Goes to the Senate for Advice and Consent,” Folder #2, LBJ Library.
  10. “Memorandum of the Legal Adviser,” April 13, 1967, Box I:46, “The Papers of Arthur Goldberg,” Folder 3, Library of Congress.
  11. No title, January 16, 1967, Legislative Background Outer Space Treaty History Box 1, Folder 10, “The Treaty,” LBJ Library.
  12. “Talking Paper for the Chairman, JCS, fur [sic] use at a meeting of the National Security Council on 15 September 1966,” September 15, 1966, “Legislative Background Outer Space Treaty History Box 1, Folder 9, “The Second and Final Negotiations,” LBJ Library.
  13. Day, Dwayne. “Close encounters of the top secret kind.” The Space Review, October 20, 2014.
  14. Foster, “Memorandum for the Assistant Secretary, ISA,” LBJ Library.
  15. “Inspection,” undated, Folder, “Outer Space Treaty (1962) – NASA response and comments to Proposed Treaty, 17368,” NASA History Office archives.
  16. “Inspection,” NASA History Office archives.
  17. “Verification of the ‘No bombs in Orbit’ Portion of the Space Treaty,” December 28, 1966, Legislative Background Outer Space Treaty History Box 1, Folder 10, “The Treaty,” LBJ Library.
  18. “Memorandum for the Secretary of Defense,” February 9, 1967, Legislative Background outer Space Treaty History Box 2, Folder “The Senate Considers the Treaty and Gives its Advice and Consent,” LBJ Library.

Project Thor

Back before he was a science fiction author, Dr. Jerry Pournelle was working in operations research at Boeing. There he came up with the concept for Project Thor, aka "Rods from God". The USAF calls them "hypervelocity rod bundles.

(so it is not true that Project Thor was "invented by a science fiction writer", Dr. Pournelle had not yet started his writing career when he created it)

The weapons are rods of tungsten, ranging in size from that of a crowbar to that of a telephone pole (about 12 meters for all you young whipper snappers who have never seen a land-line phone). Each one has a small computer in the rear and control fins on the nose, i.e., they are dirt cheap and can be mass produced. Boost them into orbit, and each one can be deorbited to strike a specific target anywhere on Earth in a few minutes, striking it at about 3 to 9 kilometers per second. This is equal to 1 to 3 Ricks worth of damage, which means the unfortunate target will be on the receiving end of the equivalent of 3 kilograms of TNT for each kilogram of tungsten rod from god. Not bad for a crowbar. Especially since they are not covered under the SALT II treaty.

A 2003 USAF report describes rods that are 6.1 m × 0.3 m tungsten cylinder The report says that while orbital velocity is 9 kilometers pre second, the design under consideration would have slowed down to about 3 kilometers per second by the time it hit the target. The report estimates that the rod will impact with a force of 11.5 tons of TNT. The back of my envelope says that a cylinder that size composed of pure tungsten will have a mass of 8.3 metric tons, but the figures in the USAF report imply that the rod has a mass of 8.9 metric tons. Which is close enough for government work.

11.5 tons of TNT per rod is pretty pathetic, you might as well use a conventional bomb. This is because 3 kilometers per second is 1 Rick, which means each kilogram of rod is equal to one kilogram of TNT, so why not just drop TNT from a conventional bomber?

An article in Popular Science breathlessly suggests that the rods will strike the target at 11 kilometers per second. This is 13.4 Ricks, which will give the rod an impact of 120 metric tons of TNT. That's more like it, now we are getting into tactical nuclear weapons levels of damage. But the article does not explain how the rod is suppose to start at 9 km/s and strike at 11 km/s after being slowed by atmospheric friction. Popular Science left that as an exercise for the reader. Or as proof of questionable research.

The rod is admittedly quite difficult for the enemy to defend against. It is moving like a bat out of hell, er, ah, has a very high closing velocity, and it has a tiny radar cross section.

The trouble is, the "plasma sheath" created by atmospheric re-entry prevents remote control of the rod. Radio cannot pass through the plasma, so the bar has to be inertially guided. Or not. A Russian scientist thinks they have found the key to allowing radio signals to pass through the plasma sheath. A related problem is that anything on the rod that is not made of tungsten is going to want to burn up in re-entry. Things like the guidance computer, sensors, and hypothetical remote control radio.

The main drawback to Project Thor is the prohibitive cost of boosting the rods into their patrol orbits. Of course if you have a space-faring civilization, the rods can be manufactured already in orbit, thus eliminating the boost cost. Which means any planetary nation without a presence in space is going to be at a severe disadvantage, but that is always true.

Another problem is maintaining the rods in orbit. Things are going to break down, so you either have to have a budget to boost replacements or have assets in orbit that can do maintenance.

Finally, no, this is not the same as the Magnetic Accelerator Cannon from the Halo games. That is a coil gun, Project Thor is more like a weaponized version of dropping a penny from the top of the Empire State building.

Predictably, some maniac made a "Rods from God" mod for the game Kerbal Space Program.


The basic weapon system consists of an orbiting element some 20 to 40 feet long. It requires a GPS receiver to locate itself; a means of taking it out of orbit; an atmospheric guidance system, such as a means of changing its center of gravity (moving weights, small fins, etc.), and a communication system to give it a target and activate the system. No warhead is wanted or needed. Thor will impact a target area at about 12,000 feet per second (3.7 km/s); that is sufficient kinetic energy to destroy most hard targets, with minimum collateral damage and of course no fall-out. Achievable accuracy has been estimated at ten to twenty feet CEP.

ed note: CEP is Circular Error of Probablility. It is the radius of a circle inside of which 50% of the missiles will fall.


A kinetic bombardment or a kinetic orbital strike is the hypothetical act of attacking a planetary surface with an inert projectile, where the destructive force comes from the kinetic energy of the projectile impacting at very high velocities. The concept originated during the Cold War.

The typical depiction of the tactic is of a satellite containing a magazine of tungsten rods and a directional thrust system. When a strike is ordered, the satellite would brake one of the rods out of its orbit and into a suborbital trajectory that intersects the target. As the rod approaches periapsis and the target due to gravity, it picks up immense speed until it begins decelerating in the atmosphere and reaches terminal velocity shortly before impact. The rods would typically be shaped to minimize air resistance and maximize terminal velocity. In science fiction, the weapon is often depicted as being launched from a spaceship, instead of a satellite.

Kinetic bombardment has the advantage of being able to deliver projectiles from a very high angle at a very high speed, making them extremely difficult to defend against. In addition, projectiles would not require explosive warheads, and—in the simplest designs—would consist entirely of solid metal rods, giving rise to the common nickname "Rods from God". Disadvantages include the technical difficulties of ensuring accuracy and the prohibitively high costs of positioning ammunition in orbit.

The Outer Space Treaty is designed to prohibit weapons of mass destruction in orbit or outer space; however, its text does not formally define what constitutes a weapon of mass destruction. Since the most common form of kinetic ammunition is inert tungsten rods, it is uncertain if kinetic bombardment is not prohibited by treaty.

Real life concepts and theories

During the Vietnam War, there was limited use of the Lazy Dog bomb, a steel projectile shaped like a conventional bomb but only about 25.4 mm (1") long and 9.525 mm (3/8") diameter. A piece of sheet metal was folded to make the fins and welded to the rear of the projectile. These were dumped from aircraft onto enemy troops and had the same effect as a machine gun fired vertically. Observers visiting a battlefield after an attack said it looked like the ground had been 'tenderized' using a gigantic fork. Bodies had been penetrated longitudinally from shoulder to lower abdomen.

Project Thor is an idea for a weapons system that launches telephone pole-sized kinetic projectiles made from tungsten from Earth's orbit to damage targets on the ground. Jerry Pournelle originated the concept while working in operations research at Boeing in the 1950s before becoming a science-fiction writer.

The system most often described is "an orbiting tungsten telephone pole with small fins and a computer in the back for guidance". The system described in the 2003 United States Air Force report was that of 20-foot-long (6.1 m), 1-foot-diameter (0.30 m) tungsten rods, that are satellite controlled, and have global strike capability, with impact speeds of Mach 10.

The time between deorbit and impact would only be a few minutes, and depending on the orbits and positions in the orbits, the system would have a worldwide range. There would be no need to deploy missiles, aircraft or other vehicles. Although the SALT II (1979) prohibited the deployment of orbital weapons of mass destruction, it did not prohibit the deployment of conventional weapons. The system is not prohibited by either the Outer Space Treaty or the Anti-Ballistic Missile Treaty.

The idea is that the weapon would naturally contain a large kinetic energy, because it moves at orbital velocities, at least 8 kilometers per second. As the rod would approach Earth it would necessarily lose most of the velocity, but the remaining energy would cause considerable damage. Some systems are quoted as having the yield of a small tactical nuclear bomb. These designs are envisioned as a bunker buster. As the name suggests, the 'bunker buster' is powerful enough to destroy a nuclear bunker. With 6–8 satellites on a given orbit, a target could be hit within 12–15 minutes from any given time, less than half the time taken by an ICBM and without the launch warning. Such a system could also be equipped with sensors to detect incoming anti-ballistic missile-type threats and relatively light protective measures to use against them (e.g. Hit-To-Kill Missiles or megawatt-class chemical laser).

In the case of the system mentioned in the 2003 Air Force report above, a 6.1 m × 0.3 m tungsten cylinder impacting at Mach 10 has a kinetic energy equivalent to approximately 11.5 tons of TNT (or 7.2 tons of dynamite). The mass of such a cylinder is itself greater than 9 tons, so the practical applications of such a system are limited to those situations where its other characteristics provide a clear and decisive advantage—a conventional bomb/warhead of similar weight to the tungsten rod, delivered by conventional means, provides similar destructive capability and is far more practical and cost effective.

The highly elongated shape and high mass are to enhance sectional density and therefore minimize kinetic energy loss due to air friction and maximize penetration of hard or buried targets. The larger device is expected to be quite effective at penetrating deeply buried bunkers and other command and control targets.

The weapon would be very hard to defend against. It has a very high closing velocity and small radar cross-section. Launch is difficult to detect. Any infrared launch signature occurs in orbit, at no fixed position. The infrared launch signature also has a much smaller magnitude compared to a ballistic missile launch. One drawback of the system is that the weapon's sensors would almost certainly be blind during atmospheric reentry due to the plasma sheath that would develop ahead of it, so a mobile target could be difficult to hit if it performed an unexpected maneuver. The system would also have to cope with atmospheric heating from re-entry, which could melt non-tungsten components of the weapon.

The phrase "Rods from God" is also used to describe the same concept. An Air Force report called them "hypervelocity rod bundles".

In science fiction

In the mid-1960s, popular science interest in orbital mechanics led to a number of science fiction stories which explored their implications. Among these was The Moon Is a Harsh Mistress by Robert A. Heinlein in which the citizens of the Moon bombard the Earth with rocks wrapped in iron containers which are in turn fired from an electromagnetic launch system at Earth-based targets.

In the 1970s and 1980s this idea was refined in science fiction novels such as Footfall by Larry Niven and Jerry Pournelle (the same Pournelle that first proposed the idea for military use in a non-fiction context), in which aliens use a Thor-type system. During the 1980s and 1990s references to such weapons became a staple of science fiction roleplaying games such as Traveller, Shadowrun and Heavy Gear (the latter game naming these weapons ortillery, a portmanteau of orbital artillery), as well as visual media including Babylon 5's "mass drivers" and the film Starship Troopers, itself an adaptation of a Heinlein novel of the same name.

The re-purposing of space colonies for use in kinetic bombardment (referred as a "colony drop") is a frequent element of the Gundam franchise and is central to the plots of Mobile Suit Gundam: Char's Counterattack and Mobile Suit Gundam 0083: Stardust Memory.

A smaller "crowbar" variant is mentioned in David's Sling by Marc Stiegler (Baen, 1988). Set in the Cold War, the story is based on the use of (relatively inexpensive) information-based "intelligent" systems to overcome an enemy's numerical advantage. The orbital kinetic bombardment system is used first to destroy the Soviet tank armies that have invaded Europe and then to take out Soviet ICBM silos prior to a nuclear strike.

In Neal Stephenson's Anathem a kinetic bombardment weapon is deployed from orbit to trigger the eruption of a dormant volcano.

From the mid-1990s, kinetic weapons as science fiction plot devices appeared in video games. Appearing in Bullfrog Productions' 1996 Syndicate Wars as a player-usable weapon, it also featured prominently in the plot of Tom Clancy's Endwar, Mass Effect 2 and Call of Duty: Ghosts, to name some.

The Warren Ellis comic Global Frequency (issue #12, "Harpoon", August 2004) featured the threat of kinetic spears, weapons designed to be dropped from satellites, heat up on re-entry, and strike the ground with the force of a tactical nuke, and as hot as the edge of the sun. Rather than being a weapon of war they were depicted as part of a 'die-back' protocol designed to reduce Earth's human population to a sustainable level.

In Daniel Suarez's book Freedom, a suborbital version of Thor is used composed of many small arrows or spikes for anti-personnel use.

In James S. A. Corey's The Expanse series, a radical group from within the Belter movement bombards Earth with high-speed asteroids, killing billions.

In 2013 a kinetic weapon bombardment system consisting of tungsten rods in an orbiting platform, codenamed Project: Zeus, was featured in the movie G.I. Joe: Retaliation, where it destroys London. However, the movie misrepresented physics by claiming the rod would not be "launched" or "fired" but merely "dropped". If it were released without force it would orbit the Earth in the same manner as the platform itself. In order for a rod to fall straight toward the center of Earth it would need to be launched away from the station with a tangential velocity equal in magnitude and opposite in direction from the orbiting station. This velocity would be in the range of approximately 7–8 km/s for satellites in low earth orbit, however, the actual velocity change needed to merely deorbit within half an orbit would be much less. Likely a few hundred m/s For a low-orbiting satellite, if even that much.

In John Birmingham's Stalin's Hammer (a part of his Axis of Time series), Soviet scientists use 21st century technology obtained from a fleet thrown back to World War II to create a satellite capable of launching tungsten rods from orbit and launch it in early 50's.

In David Weber's Honorverse series, kinetic strike weapons are a standard armament of all space navies that conduct orbit-to-ground operations. The version used by the Royal Manticoran Navy is a six-hundred-kilogram iron slug equipped with a small gravitic drive, capable of variable yields ranging from that of a large artillery shell to an intermediate-yield nuclear device, and packaged in six-shot satellites that are deployed from starship counter-missile tubes.

An episode of Justice league featured a satellite based weapon that combines this with a rail gun which used magnetic coils to attract and then launch meteors toward the earth's surface.

In Peter F. Hamilton's The Night's Dawn trilogy, "kinetic harpoons" are being used to bombard the surface of a planet. The book in which the event occurs also specifies how the staggering of the harpoons impact caused the shockwaves from the impacts to resonate and result in an artificial earthquake.

From the Wikipedia entry for KINETIC BOMBARDMENT

antigravite: Chinese scientists also took an interest in this advanced technology and patented some sort of a similar device as CN106052482B filed on 20160602 but granted on 20171020. The single patent title I found by chance (spent not too much time on it) roughly translates as: "A return to orbit deployment method for space-based kinetic energy weapon strikes area" and is downloadable from here.

Scott Lowther: No doubt. But physics isn't any different for them than for American scientists. It is certainly possible to launch telephone poles of tungsten into orbit, but the same problems remain. Getting them back *down* is no trivial feat. Unlike how these systems are generally portrayed in the movies (like the second "GI Joe" movie), you don't simply "drop" them. You have to *propel* them down from orbit. And given their great mass, adding a few kilometers per second of delta V to them is no trivial feat.

Additionally, the claims that these things pack the punch of nukes is exaggerated to the point of being outright lies. They would hit the ground at less than orbital velocity (how much less is down to trajectory options... if you slow it down only a little bit to get it to de-orbit, it will hit the ground at a relatively shallow angle; if you drop it straight down, then you had to have dumped most of the orbital velocity). LEO circular orbit velocity is about 7,800 m/sec. The density of tungsten is 19.3 grams/cubic centimeter. So a rod 20 cm in diameter and ten meters long would have a volume of 3.14159*(10^2)*1000 = 314,159 cubic cm => 6,063 kg. Having six metric tons whack you upside the head at 7.8 km/sec would be harsh, but is it nuke-like? The kinetic energy is 1/2 M*V^2 = .5* 6063 * 7800^2 = 184,436,460,000 joules (184.4 gigajoules). One metric ton of TNT releases 4.184 gigajoules, so this six-ton rod has the equivalent yield of 44.1 metric tons of TNT, a multiple of 7.35.

Keep in mind: in order to drop that six ton rod of tungsten on the other guy, you had to expend a de-orbit stage of unknown mass, as well as a whole lot of tons of rocket propellant to boost the system into orbit in the first place. The Falcon 9 Full thrust can put 22.8 tons into orbit (equivalent to 3.75 rods, not counting de-orbit it three rods), burning through 410.9 tons of propellant in the first stage and 107.5 tons of propellant in the second => 518.4 tons of propellant expended to deliver the equivalent of 3X44.1 tons (132.3 tons) of TNT onto the enemy.

An entire Falcon 9 delivers a maximum of 0.13 kilotons of destructive potential upon the enemy using "Thor." Alternatively, you could load up that Falcon Nine with a couple hundred megatons of thermonuclear sunshine.

Avimimus: (i.e. it isn't that impressive an idea).

Scott Lowther: Actually it would be an impressive weapon. Someone on the ground would have very little time to react to it if they detected it at all (if it begins entry-heating to incandescence at 100 km altitude and it's coming in at a shallow angle so it has to cross 200 kilometers and it maintains, say, 7 km/sec, an observer could potentially see it as an incoming glowing spark for about 29 seconds), and even if it was detected there's not a lot that could be done to stop it: hit-to-kill smart rocks would likely just spang off the side of the thing. And when it hit it would make a hell of a mess. Claims of being able to penetrate deeply are generally overblown, but one of these things bullseying a battleship would like to cut it in half.

It's just a terribly impractical weapon. The cost is immense, and the tactical utility is poor: how many times in a day would the thing be anywhere near the target?

Avimimus: tungsten would allow a higher terminal velocity I suppose.

Scott Lowther: The high density and high temperature would allow a tungsten rod to punch deeper, faster. The drag would be the same as for a rod of the same size and geometry made out of concrete, but the density increase means increased mass but with the same cross-sectional area.

Avimimus: The main benefit compared to your 'couple hundred megatons' is, well... considerably reduce fallout? Right? That is a thing?

Scott Lowther: A tungsten rod would produce no fallout, since there are no radiologicals involved. Unless it's targeting a nuclear site of some kind.

Avimimus: Also, I suppose one could get more power from the tungsten stick if it was in a highly elliptical orbit, right?

Scott Lowther: Correct. As well as a more perpendicular strike on the surface, assuming that the de-orbit burn was carried out much further out.

If you manufactured it further out in space you wouldn't have to climb the gravity well either.

In all likelihood, well-developed asteroid mining processes will simply chew up space rocks and separate the resulting fine powders by the elemental compositions (rather than following veins of material through the asteroid, since those are unlikely to exist as such). So metallic asteroids might give you X tons of iron, Y tons of nickel, and Z kilograms of uranium and tungsten in separate bins.

The problem with Thor weapons in deep space is that Thors are meant to take out reasonably precise targets... ships, tanks, bunkers. The likelihood of targeting such systems from beyond the moon is low. Deep-space kinetic bombardment is more likely to take the form of big rocks. Instead of six tons of precisely aimed tungsten you'll get six million tons of meh-aimed metal-rich rock. Put a ten-mile crater in the ground and not only are you reasonably well assured of taking out the target, you also have deniability. "Gee whiz, me? Naw, musta just been one of them Tunguska sort of things. Sad, really..."

kcran567: The ultimate rock throw would be controlling (adding some type of propulsion and guidance) to space rocks/asteroids the bigger the better. Mountain sized. And then parking it over the enemy whoever that would be. Could destroy an entire continent if possible? But also start an ice age for the entire planet?

Scott Lowther: The point of dropping rocks on people is deniability. Rocks fall on their own, perfectly naturally, as Tunguska and Chelyabinsk showed. If you are going to park a rock in orbit and use it as a threat, you'd be better advised to simply invest in Really Powerful H-bombs in the gigaton range. Because de-orbiting a mountain to drop in within half a hemisphere of the target would be a monumental challenge, and you wouldn't be fooling anyone.

That said: parking a mountain in high orbit is good idea. But to chew it up for resources, rather than as a hammer. You could always mount mass drivers to it to chuck ten-ton bricks of asteroidal nickel/iron at anyone who ticks you off.

Charlesferdinand: Would these tungsten rods lose a lot of their mass through friction by the atmosphere?

Scott Lowther: Not if designed correctly. The nose would probably have an ablative cap.

Charlesferdinand: Also, why rods? Obviously it looks cooler, but wouldn't balls be more convenient and ballistically more effective?

Scott Lowther: Nope. The point is to retain as much velocity as possible, to lose as little of it as possible due to drag. And one simplistic way to look at the drag of ballistic objects is the mass per cross sectional area. So... look at a tungsten rod shaped like a pencil. Each square inch of frontal area might be backed up by ten, fifteen, twenty feet of tungsten. A sphere of the same mass would be considerably larger in diameter, with much less mass per cross sectional area. This is related to why bullets these days are relatively long compared to their diameter... and not musketballs.

From Secret Projects Forum TOPIC: RODS FROM GOD / "PROJECT THOR"

     "One more thing, Mr. President," Curtis said insistently.
     "Today's attack. I suppose you'll be sending in lots of armor."
     The President looked puzzled.
     "We'll do it right, Doctor," General Toland said. He turned to leave. "And I'd like to get at it."
     "Thor," Curtis said.
     Toland stopped. "What's that? It sounds like something I've heard of—"
     "Project Thor was recommended by a strategy analysis group back in the eighties," Curtis said. "flying crowbars." He sketched rapidly. "You take a big iron bar. Give it a rudimentary sensor, and a steerable vane for guidance. Put bundles of them in orbit. To use it, call it down from orbit, aimed at the area you're working on. It has a simple brain, just smart enough to recognize what a tank looks like from overhead. When it sees a tank silhouette, it steers toward it. Drop ten or twenty thousand of those over an armored division, and what happens?"
     "Holy sh*t," Toland said.
     "Are these feasible?" Admiral Carrell asked.
     "Yes, sir," Anson said. "They can seek out ships as well as tanks—"
     "But we never built them," Curtis said. "We were too cheap."
     "We would not have them now in any case," Carrell said. "General, perhaps you should give some thought to camouflage for your tanks—"
     "Or call off the attack until there's heavy cloud cover," Curtis said. "I'm not sure how well camouflage works. Another thing, look out for laser illumination. Thor could be built to home in that way."

ed note: "Anson" is Robert Anson Heinlein. "Curtis" is Jerry Pournelle.

From Footfall by Larry Niven and Jerry Pournelle (1985)

Strategic Nuclear Weapons

As mentioned in the Space War section, nuclear weapons behave quite differently in airless space (and airless planets) than they do in a planetary atmosphere.

On a planet with an atmosphere the x-rays are absorbed by the atmosphere and become thermal radiation and atmospheric blast. The duration of thermal pulse increases with yield from about 1 second for 10 kilotons to 10 seconds for 1 megaton.

In space it is just x-rays and neutrons.

Percentage of total energy
In Atmosphere
Blast40% to 50%
Thermal Radiation30% to 50%
Ionizing Radiation
(Prompt Radiation)
(unless this is a neutron bomb)
(Residual Radiation)
5% to 10%
In Space
Soft x-rays80%
Gamma rays10%

Thermal Radiation

In the tables below the range between the detonation point and the affected target is called the "slant range." If the weapon detonates on the ground this is just the ground distance between the target and the explosion. However, nuclear weapons are commonly detonated at some height above the ground to increase their effect. Given the ground range and the detonation height, the slant range can be calculated by using the Pythagorean theorem:

Thermal Radiation Graph

from Physics and Nuclear Arms Today edited by David Hafemeister (1991)
  • Explosion Yield is the yield of the nuclear weapon in kilotons. 1,000 kilotons = 1 megaton
  • Slant Range is the distance between the target and the detonation point of the weapon, in miles.
  • Curves are thermal flux in calories per square centimeters.

The vertical red line is for 1 megaton (1,000 kilotons). Remember these have a pulse duration of 10 seconds.

  • 5 to 6 cal/cm2 for 10 seconds will cause second degree burns. (green line)
  • 8 to 10 cal/cm2 for 10 seconds will cause third degree burns. (blue line)
  • 20 to 25 cal/cm2 for 10 seconds will ignite clothing. (violet line)

The equation is:

Q ≈ 3000 * ( ƒ * τ * Y / D2 )


Q = thermal flux (cal/cm2)
ƒ = thermal energy fraction ( from 0.35 to 0.40 for air bursts, 0.18 for ground bursts)
τ = atmospheric transmission factor (0.6 to 0.7 at 5 miles, 0.05 to 0.1 at 40 miles. Even lower if foggy)
Y = nuclear weapon yield (megatons). Please note the graph above uses kilotons, not megatons
D = slant range (miles)
EffectsExplosive yield / detonation height
1 kt / 200 m20 kt / 540 m1 Mt / 2.0 km20 Mt / 5.4 km
Thermal radiation—ground range (km)
Third degree burns0.62.51238
Second degree burns0.83.21544
First degree burns1.14.21953
from Wikipedia article Effects of nuclear explosions
Note the table is using ground range, not slant range.


A bit less than half the nuclear weapon's energy becomes atmospheric blast. This has two effects: a sharp increase in atmospheric pressure ("overpressure"), and incredibly strong winds. The overpressure crushes objects and collapses buildings. The wind turns lightweight objects into dangerous projectiles.

In the complicated equations for figuring the area that suffers from a given overpressure, the area is proportional to Y2/3 (where Y is the weapon's yield). This is called the "equivalent megatonnage" of a nuclear weapon. Why do we care? The point is that the combined equivalent megatonnage of several low-yield weapons is greater than that of a single weapon with the same total yield. In other words five warheads (2 megatons each) will do more damage to a city than a single warhead (10 megatons).

OverpressurePhysical Effects
20 psiHeavily built concrete buildings are severely damaged or demolished.
10 psiReinforced concrete buildings are severely damaged or demolished.
Small wood and brick residences destroyed.
Most people are killed.
5 psiUnreinforced brick and wood houses destroyed.
Heavier construction severely damaged.
Injuries are universal, fatalities are widespread.
3 psiResidential structures collapse.
Serious injuries are common, fatalities may occur.
1 psiLight damage to commercial structures
Moderate damage to residences.
Window glass shatters
Light injuries from fragments occur.

Note that the same source says you need 40 psi before lethal effects are noted on people, which contradicts the 10 psi entry above. I don't know which to believe.

Peak overpressureMaximum Wind Velocity
50 psi934 mph
20 psi502 mph
10 psi294 mph
5 psi163 mph
2 psi70 mph
Tables from Atomic Archives

The x-axis is the slant range in feet, divided by the weapon yield in megatons rasied to the 1/3 power. Trace upward to intersect the curve, then to the left to find the peak overpressure in PSI.

The curve can be traced approximately by the formula:

z = Y1/3 / D

p = (22.4 * z3) + (15.8 * z3/2)


z = scaled yield (megatons1/3/mile)
Y = weapon yield (megatons)
D = slant distance (miles)
p = overpressure (lb/in2 or PSI)

EffectsExplosive yield / detonation height
1 kt / 200 m20 kt / 540 m1 Mt / 2.0 km20 Mt / 5.4 km
Blast—ground range (km)
Urban areas completely levelled
(20 psi or 140 kPa)
Destruction of most civilian buildings
(5 psi or 34 kPa)
Moderate damage to civilian buildings
(1 psi or 6.9 kPa)
Railway cars thrown from tracks and crushed
(62 kPa)
(values for other than 20 kt are extrapolated
using the cube-root scaling)
from Wikipedia article Effects of nuclear explosions
Note the table is using ground range, not slant range.

Things are more complicated when the detonation point is some distance above ground level.

The primary shock wave expands outward as a sphere from the weapon detonation point. If this is not a ground-burst, at some point the sphere will expand until it hits the ground. The shock wave is reflected upward from the ground. Since the shocked region inside the sphere is hotter and denser than the rest of the atmosphere, the reflected shock wave travels faster than the primary shock wave. For certain geometries, the reflected shock wave catches up with the primary shock wave and the two shock fronts merge. This is called the Mach Stem. The overpressure at the stem is typically twice that of the primary shock wave.

The area the Mach stem passes over is called the Mach reflection region. The area from ground zero to the start of the Mach reflection region is called the Regular reflection region. It only suffers from the passage of two separate shock waves with the standard overpressure. The Mach reflection region suffers the double overpressure caused by the Mach stem.

The chart below plots the regular reflection region and Mach reflection region, given the detonation distance from the ground. To use, you divide the burst height and the distance from ground zero by weapon kilotons raised to the 1/3 power.

For instance, if the weapon had a yield of 1,000 kilotons (1 megaton) and the weapon burst 2,000 feet above ground level, 2000 / (10001/3)

Scaled Height of Burst = burstHeight / yield1/3
Scaled Height of Burst = 2000 / 10001/3
Scaled Height of Burst = 2000 / 10
Scaled Height of Burst = 200

so on the plot for the vertical scale you would use the tick-mark at 200. By the same token, for the horizontal scale, the tick mark for 800 corresponds to 800 * 10 = 8,000 feet (where 10 = 10001/3).

The dotted line shows where the regular reflection region stops and the Mach reflection region begins.

The bulges in the overpressure curves show where you can optimize the height of burst for a given overpressure. For instance, look at the 15 lb/in2 curve. Find the point on the curve that gets the farthest to the right. Trace a line horizontally to the vertical scale and you'll see this happens at a scaled height of burst of 650 feet. For a 1,000 kiloton weapon this is a burst height of 6,500 feet.

In other words, a weapon bursting at 650 scaled feet of altitude will throw 15 PSI of overpressure out to 1,200 scaled feet from ground zero. But a weapon doing a ground burst with 0 scaled feet of altitude will only throw 15 PSI out to 800 scaled feet from ground zero.

from Physics and Nuclear Arms Today edited by David Hafemeister (1991)

Prompt Radiation

EffectsExplosive yield / detonation height
1 kt / 200 m20 kt / 540 m1 Mt / 2.0 km20 Mt / 5.4 km
Effects of instant nuclear radiation—slant range (km)
Lethal total dose (neutrons and gamma rays)
Total dose for acute radiation syndrome1.
from Wikipedia article Effects of nuclear explosions
"Lethal" is defined as a dose of 10 grays. "Acute radiation syndrome" is defined as a dose of 1 gray.

Residual Radiation

This is the radioactive fallout, radioactive dust that falls from the sky in a long plume extending downwind.

As a general rule, the fallout is dangerous for about one to six months after the bomb blast.

Unless it was a salted bomb, then you are probabably looking at a hundred years or so. A salted bomb whose fallout emitted a dosage of 10 sieverts per hour would need about 25 half-lives to decay to safe levels (i.e., to a dosage below natural background radiation). For example, a salted bomb producing Cobalt-60 would have fallout with a half life of 5.2714 years. 25 half-lives would be 131.785 years. Tantalum-182 has a half-life of only 114.4 days, it would be safe in about 7.8 years.

Air bursts tend to produce lesser amounts of fallout, but which travel at high altitudes and can scatter itself all over the entire planet.

Ground bursts tend to produce more severe levels of fallout, but which only travel relatively short distances from the detonation site (several hundred kilometers). The Castle Bravo 15 megaton nuclear test made a plume about 500 kilometers downwind with a maximum width of 100 kilometers.

Water surface bursts are sort of in-between.

The Wikipedia article stated that the crater of a ground burst would have fallout emitting radiation at a dosage rate of 30 grays per hour, but failed to specify the yield of the weapon.

Specialized Nuclear Weapons

Enhanced Radiation Weapon
Also known as a "neutron bomb." This is a bomb optimized so most of the energy comes out as neutrons. In conventional nuclear weapons most of the energy comes out as x-rays. The idea is for the weapon to kill enemy troops and civilians while doing minimal damage to buildings and equipment.
Details are classified but the best I've found is the theoretical maximum for a neutron bomb is 80% of the energy is neutrons and 20% x-rays. For conventional nuclear weapons it is 80% soft X-rays, 10% gamma rays, 10% neutrons.
Salted Bomb
Also known as a "cobalt bomb." This is a bomb optimized to produce huge amounts of radioactive fallout in order to render large areas uninhabitable.
This is done by encasing the weapon in a jacket composed of some element that will easily be transmuted into a radioactive isotope by the weapon's neutron flux. Proposed elements for the jacket include cobalt-59, gold-198, tantalum-182, zinc-65, and sodium-24.
A conventional nuclear weapon typically generates fallout that will decay to safe levels in one to six months. A cobalt bomb whose fallout caused a dose rate of 10 sieverts per hour would take about 130 years (25 half-lives) to decay to safe levels (safe levels being defined as "less than natural background radiation").
The name "salted" comes from the expression "sowing the earth with salt".
Dirty Bomb
This is not a military weapon, it is an ineffectual terrorism device. It is a stick of dynamite or other small chemical explosive inside a container of powdered radioactive material. The only reason it is mentioned here is because it is sometimes confused with a salted bomb.
A dirty bomb might spread a bit of mildly radioactive dust over a building or two.
A salted bomb will spread highly radioactive fallout across half a continent.
The dreaded Nuclear Electromagnetic Pulse. A conventional nuclear weapon of several megatons yield is detonated at a high altitude (commonly mentioned as 400 kilometers). The resuling EMP does damage to every device using electricity within a huge range. The details are sketchy because they are still classified. For best results a planetary atmosphere is required.
The linked Wikipedia article has an overview of the convoluted details, including a useful quote from a 2010 Oak Ridge National Laboratory report on common EMP misconceptions.

Project Pluto

This is mostly from THE PLUTO PROGRAM and Aerospace Projects Review Volume 2, Number 1. Some additional material from Spaceship Handbook.

This is an old favorite among fans of nuclear weapons, the one everybody shakes their head over and says WHAT THE FLAMING FRACK WERE THEY THINKING??!? You often see it under such names as Project Pluto, Flying Chernobyl, S.L.A.M., The Flying Crowbar, Nightmare Missile, Flying Death Factory, and Armageddon Cruise Missile From Hell.

Technically the entire weapon was called Supersonic Low Altitude Missile or SLAM. Project Pluto was just the engine.

The original idea was a 1955 version of what we now call a cruise missile. Seeing that this was going to be a part of mutually assured destruction, perhaps even a possible replacement for the Strategic Air Command, the designers wanted SLAM to be long ranged. Very long ranged. Circle-The-Globe-Four-And-A-Half-Times long ranged.

Chemical fuel couldn't possibly fill the bill, the only thing with enough power was nuclear energy. Alas, cruise missiles share the same problem that aircraft and spacecraft have with atomic drives. The three vehicles all suffer from the Every Gram Counts limit so they want to be as light as possible. But anti-radiation shields are the opposite: the heavier the better. If the crew cabin was located far enough away from the reactor, you might be able to get away with using an anti-radiation shadow shield light enough so that the aircraft could actually get off the ground. It is a pity that anybody on the ground the aircraft flew over would be bathed in deadly radiation.

Then some cold-hearted genius in the research department saw how to turn the liability into an asset.

Understand that the SLAM reactor, like all reactors, are not very radioactive. Until the first time they are powered up, then they will emit torrents of radioactive death for centuries.

If the nation goes to DEFCON 1 you launch the SLAM using non-radioactive chemical rockets. These get the nightmare missile out to sea far enough so that no (United States) person was endangered. Then the totally unshielded reactor was powered up. Since the monster had a range of 182,000 km (x4.5 the circumference of Terra) it wasn't going to run out of fuel anytime soon. Especially since it didn't have to lug around a heavy radiation shield. It could fly in a circular holding pattern until nuclear war was initiated or called off, killing nobody with radiation except sea life and any fishermen unfortunate to be underneath.

Somebody figured that radiation in the defense of liberty is no vice. Somebody on Twitter remarked: "So it does fly without core containment, that is some serious Reaver sh*t."

If the war was called off, the SLAM(s) would abort by quenching their reactors and ditching into the (hopefully) deep ocean. Anybody with bright ideas about salvaging US weapons from the sunken SLAMs will have to deal with the radiation from its neutron-activated structure. The SLAM designers might deliberately incorporate cobalt or something similar into the structure as a rude surprise.

5,500 pound thermonuclear weapons payload
Can be divided as:
x126 megatons
x51.3 megatons
x91.1 megatons
x14750 kilotons
x16200 kilotons
x3650 kilotons
x425 kilotons

But if war is declared, the SLAMs will drop to a stealth wave-hugging altitude and proceed at supersonic velocity toward their designated Soviet targets, with a weapons loadout of 1 to 42 thermonuclear bombs (1@26 megatons, 42@5 kilotons each). 25 megatons is considered to be a "city-killer", though a single bomb that big tends to be a waste of nuclear energy. Since there are no skyscrapers a mile in the air or a mile underground, the most of the spherical nuclear fireball is wasted. It is more efficient to use a pattern of kiloton devices with a fireball about one skyscraper-height in radius.

The SLAM will cross the ocean at an altitude of 35,000 feet, but when it approached the Soviet air detection system it would drop below "radar detection altitude". One source said that was 500 to 1,000 feet, another said 50 feet.

Traveling at Mach 3 at treetop level (15 meters or 50 feet) means that any person standing underneath will be instantly killed by the sonic shockwave alone (they will also be made deaf by the 150 dB sound and given cancer, but these things matter not to a dead person). The thing is also white-hot so there will be a bit of thermal pulse as well, to add insult to injury.

The same cold-hearted genius also figured that after a given SLAM had dropped all its H-bombs it could still do damage by leisurely flying a criss-cross pattern over Soviet territory, irradiating the croplands and people with deadly radiation from the totally unshielded reactor (sowing the ground with salt, radioactive-style). This also meant that the SLAM designers didn't have to worry about preventing radioactive fission fragments from escaping out the exhaust, since it would give you bonus enemy fatalities out of each gram of fission fuel. Which means they didn't bother putting any cladding on the nuclear fuel elements, they are in direct contact with the air.

And if the Soviets managed to shoot down a SLAM, it would auger into the ground at Mach 3, pulverizing the entire reactor and spreading a plume of radioactive fallout rendering the impact region uninhabitable for about the next ten-thousand years. If they fail to shoot it down, it is programmed to crash anyway. Only after it has finished its sterilization criss-cross. The hot reactor elements will mix with the white hot vaporized forward vehicle structure to create a very fine smoke of radioactive uranium oxides. That is, of a fineness to extend the length of the fallout plume. As Scott Lowther puts it: "It'd make Chernobyl look like Three Mile Island."

The mechanical designer faces a challenge. The pressure drop in the direction of the air stream creates a force of several hundreds of thousands of kilograms trying to suck the reactor out the nozzle, which is a bad thing. The materials available to make supporting structures are limited in volume and nature because of neutronic requirements (too much structural metal and the reactor can go critical while it is being assembled) and high temperatures (standard metals will melt).

SLAM Missile
ParameterEarly Tech
(Tory II-C)
Advanced Tech
(Tory III)
Payload compartment dia (in)5558
Payload compartment len (in)213300
Total Vehicle Length (ft)8488
Hot reactor dia (in)5746
Hot day design Mach
1,000 ft above sea level
Hot day design Mach
30,000 ft above sea level
Reactor wall temp (°F)25,0003,000
Max number of warheads18-2426
Payload weight (lb)14,00015,000
Missile weight (lb)55,80060,779
Booster weight (lb)61,38067,465
Expected missile range (nm)
1,000 ft above sea level
Expected missile range (nm)
30,000 ft above sea level

It is unclear if the expected range is limited by the nuclear fuel elements becoming clogged with neutron poisons, or because the ceramic reactor core crumbled. If the former, there are modern ways around that problem.


I was curious about the radiation dose the SLAM would inflict upon a person on the ground. It was traveling at 50 feet (15 meters) above the ground, near where the lethal dose was absorbed in about 5.76 seconds. But on the other hand the SLAM is traveling at about 1,000 meters per second (Mach 3) so exposure time is very short. I could not intuit whether the person would get a lethal dose or not. This calls for higher math, probably calculus. Unfortunately I failed to learn calculus (Bad Winchell! No rocket for you!). Therefore I used the old Tom Sawyer Whitewash technique.

On Google Plus I poised the question (please pardon the Imperial units):


For lack of a better source, the word problem below was created by me, unqualified though I am. Be told that it may contain unwarrented assumptions and misunderstood numerical values for which I take sole responsibility. Particularly I am assuming that the diagram above is accurate. Use the analysis below at your own risk.

     Say there is a Project Pluto nuclear ramjet cruise missile in the area.
     Say that forty feet away from it's center the radiation dose is 5×108 Röntgen/hour of gamma rays. Say that 35 feet away from the center the radiation dose is 5×106 Röntgen equivalent physical/hour of neutrons. The radiation falls off as per the inverse square law. Figure that the maximum range that the radiation has effect is about 15,300 feet, or the distance to the horizon.
     It is traveling along line A-B where the line is at a constant altitude of 50 feet (tree-top level), at a speed of Mach 3 (which I think is about 3,350 feet per second since that altitude is practically sea level).
     Somewhere near that line is point X, on the ground directly underneath line A-B. A poor hapless person is standing there.
     At some point the Project Pluto nightmare missile will appear on the horizon, flash overhead at 3,350 ft/s, and vanish on the far horizon. Emitting deadly gamma-rays and neutrons all the while.

     Question: What radiation dosage will the poor person at point X suffer?

Remember neutrons Röntgens equivalent physical have an average quality factor of 10.0 so equals an average of 0.096 Sievert. Gamma rays Röntgens have a quality factor of 1.0 so each equals 0.0096 Sievert (one-tenth that of neutrons).

Two kindly educated people came to my rescue, Peter Schmidt and Simon Smith.


I believe you need to integrate 1/(x-35)^2 * 5*10^6 from x=50 to x=15300, then multiply by 2 (to cover its approach and departure). Wolfram Alpha says ~6.7*10^5 REP/hr neutrons (6,400 Gray/hr and 64,000 Sievert/hr) .

(see WolframAlpha results here).

To sanity check, it will travel 15,300*2 feet in 9.13 s. (15,300*2 / 3,350 = 9.13)

At t = 1/2 * 9.13, using the inverse square law, the dose from 50 ft away is 2.45*10^6 Röntgen/hour, while at the horizon, it is a mere 26 Röntgen/hour.

Halfway from the horizon, it is 100 Röntgen/hour. If you average those three points (which is a linear, not inverse squared relation, so will be high), you get 1.6*10^6 REP/hr, which is 10x high, so I'm buying the Wolfram result.

If that's the dose rate, in 9.13s, dose will be about 1,700 Röntgen (6.7 * 10^5 Röntgen/hr / 3600 s/hr * 9.13 s) (16 Grays and 163 Sieverts of neutron radiation)

This website says "A short-term dose of 600 Röntgen (5.8 Grays) would probably be fatal" so RIP bystander…


I got the same ballpark as Peter. The neutron dose is about 1,700 R (16 Gy and 163 Sv) but the gamma dose is 254,000 R (2,440 Gy and 2,440 Sv). This is a death rocket that kills pretty much everybody within a 3/4 of a mile (1,200 meter) radius of its flight path.

Winchell Chung, your gamma dose is given as 5x10^8 R/hr at 40 feet whereas the neutron dose is only a measly 5x10^6 R/hr at 35, so the gamma dose will be more than 100x greater.

3/4 mile is the radius where the gamma Röntgen dose is the 600 Röntgen figure Peter used. You get that if the range varies from 15,000 ft ⇒ 4,000 ft ⇒ 15,000 ft (4,000 ft = 3/4 mile)

That Wolfram formula's very handy.

Thank you very much, Peter Schmidt and Simon Smith! Even if the figures and assumptions I supplied you with were incorrect, the technique revealed will be useful elsewhere. I really have to buckle down and learn calculus, and master Wolfram Alpha.

The Acute Radiation Chart says that 5.8 Grays is at the "Death probable within 3 weeks" level, 16 Gy is "Certain death in one week or less" along with the cruel Walking Ghost period, and 2,440 Gy is about thirty times the 80 Gy "Instant coma and certain death in 24 hours".

Peter Schmidt's formula is:

integrate 1/(x-35)^2 * 5*10^6 from x=50 to x=15300, then multiply by 2


35 = distance from SLAM of the reference dosage rate
5*10^6 = Röntgen/hour reference dosage rate value
x=50 = closest distance SLAM comes to person (altitude from ground)
x=15300 = farthest distance SLAM recedes from person (vanishes over horizon)
1/(x-35)^2 = inverse-square law, how radiation intensity varies with distance

which was derived from the word problem stating: Say that 35 feet away from the center the radiation dose is 5×106 Röntgen equivalent physical/hour of neutrons and Figure that the maximum range that the radiation has effect is about 15,300 feet, or the distance to the horizon and at a constant altitude of 50 feet. The units used for distance do not matter, as long as you use the same units for all three variables. The units used for absorbed dose do not matter, the answer will be in the same units.

This is fed into WolframAlpha as value of integral of 1/(x-35)^2 * 5 * 10^6 from x=50 to x=15300, times 2

Let's try it out. For gamma-rays it was 40 feet away from the center of radiation had a dose of 5×108 Röntgen/hour. So we feed into WolframAlpha value of integral of 1/(x-40)^2 * 5 * 10^8 from x=50 to x=15300, times 2 and it returns 1.0 * 10^8 Röntgen/hr.

1.0 * 10^8 Röntgen/hr / 3600 sec/hr * 9.13 sec = dose of 254,000 Röntgen. Which is the figure Simon Smith calculated, so we are golden.

Higher Altitude

The above figures are for a SLAM flying at 50 foot tree-top level altitude. Other sources suggest it may fly at up to 1,000 foot altitude. This will drastically reduce the radiation dosage on the ground, but how much?

I used Mr. Schmidt's handy formula, substituting "1000" for "50".

It reduces the neutron dose from a death-in-minutes 163 Gy (1,700 R) to a fighting-chance 50%-fatality 2.5 Gy (26 R).

Sadly for the person on the ground the gamma dose went from an instant-death 2,440 Gy (2.54×105 R) only to a death-in-two-days 25 Gy (2,642 R). Immediate disorientation, coma in seconds to minutes, convulsions, and certain death within 48 hours.

Using Ms. Smith's technique if you adopt a certain death dosage of 10 Gy (394,300 R/hr for 9.13 seconds) as your trigger level, this means the SLAM kills pretty much everybody within a half mile (790 meters) radius of the flight path (15,300 ft ⇒ 2,600 ft ⇒ 15,300 ft). And doesn't do the topsoil any good either. Yes, this is narrower than 3/4 of a mile, but it is only a 30% reduction. After all a half mile radius means the SLAM is laying down a path of scorched dead earth one mile wide and thousands of miles long.

The SLAM may fly at a 500 foot altitude instead of 1,000 feet, which will just increase the dosage. I leave the math as an exercise for the reader.

Hold everything. A gentleman named Giorgio Tiburzi contacted me, and has noted some flaws in the above analysis. Please note that the error appears to be me mis-reading the diagrams, it is not the fault of Mr. Schmidt and Ms. Smith. Apparently I gave them incorrect data and incorrect assumptions. Mr. Tiburzi's analysis is below:


First, I have noted a discrepancy between the values you quote for the gamma dose rate. The first graph on your webpage has units of rads per hour, and indicates a gamma flux of slightly less than 107 R/h at 30 feet. The second one quotes 109 erg/g per hour at the same range, which you have equated to rads — but in fact, the rad "was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter" [source]

The second graph, then should also be read as 107 R/hr at 30 feet, resolving this incoherence — unfortunately, in your question on Google Plus you used 5×108 R/hr at 40' for the γ dose rate (my bad).

The second problem I noticed is that the dose integral suggested by Peter Schmidt is not dimensionally correct. The dose rate we have from the graphs has units of [rads/time], and so we need to integrate it over a time interval to get a radiation dose. The inverse square law factor has to be non-dimensional, since we don't want units of meters squared at the denominator.

The correct way to approach this calculation is writing the instantaneous dose rate as a function of time, then integrating it over the time period when the missile is over the horizon.

If we define R as the dose rate at distance x0, v as the missile speed, h as the flight altitude i.e. the minimum distance to the missile, tf as the time of flight above the horizon, and t=0 at overflight,

is the slant range to the missile at each time t

the inverse-square-law scaling factor is

and the total dose for each point on the ground overflown by the missile is

The dimensions of the above equation, then are

and we get the correct unit on the left-hand side after the other factors simplify with each other. This formula is valid in a vacuum, and substituting the values R=2777 rad/sec, x0=30 ft, tf=5s or above, and v=3350 ft/sec, for a range of altitudes we obtain the following results:

Actually though, for flight altitudes just a bit above the "frying chicken in the barnyard" level, absorption of γ-rays by the intervening air becomes quite significant; there is then a second attenuation term we should be considering, besides the inverse square law.

Most prompt gamma rays from a reactor (those emitted immediately after fission, by relaxation of the daughter nuclei) have energies lower than 1 MeV. My source for this is "Prompt fission γ-ray spectra characteristics - a first summary" - Oberstedt, Wilson et al, Physics Procedia 64

I don't have a similarly clean picture for the spectrum of secondary gammas (those from fission fragment decay), but Table II of "Fission Product Gamma Spectra" by E.T. Jurney et al. seems to report an average energy of, again, 1 MeV.

Figure 8.106 of Glasstone-Dolan, The Effects of Nuclear Weapons reports a γ spectrum for a 20 kT nuclear explosion (fission) at 2 kilometers, with 70% of the energy below 750 keV. There is no data for very short distances, but since lower energy photons are absorbed quicker, hard gammas should be overrepresented in that figure compared to shorter range exposures.

I will then use 1 MeV as the average energy of gamma rays: Glasstone and Dolan, again, give an absorption coefficient μ=0.8×10-4 cm-1 for air at sea level in Table 8.96, equivalent to a halving distance of 90 meters (300 feet).

The complete dose formula for gamma rays then becomes

where the exponent is again a non-dimensional, scaled distance: the slant range multiplied the attenuation factor (i.e. the inverse of the air thickness that reduces the dose by a factor 1/e).

The new results including atmospheric shielding are then

I must admit that it's surprising to find a completely negligible value at the relatively short distance of 1 km: but after all, a dose rate of 107 R/hr at 10 meters is reduced 10,000-fold by the inverse square law and about 1,000-fold by the absorption, down to just 1 R/hr.

This is certainly an underestimate for the longer ranges, since e.g. secondary photons will be generated in the air and accounting for those would substantially change the result (source) but the general picture should hold.

I don't know how to make a similarly clean estimate for the neutron dose: I could not find any data on attenuation of neutrons through air, and neutron transport is a notoriously complex topic. If we just take the total dose rate to be 6×107 REM/hr at 30 feet (multiplying 5×106 by a quality factor of 10 for the neutrons) and use the vacuum equation, the new upper bound for exposure at 50 feet minimum distance is 280 REM, down to 10 REM when h=1400 ft. We do recover a lifethreatening exposure, then, but only for the lowest possible altitude.

Looking for some sort of external confirmation of these calculations, I turned to Alex Wellerstein's NUKEMAP, a web tool that simulates the effects of nuclear explosions with open-source models, mostly based as usual on the Glasstone-Dolan.

A 10 kiloton explosion at 1000 meters altitude, according to the model, inflicts a prompt dose of 2000 REM at ground zero (from all types of radiation). A yield of 10 kilotons corresponds to 40 TJ, and the Tory-IIc reactor — with a power of 560 MW — takes about 20 hours to generate the same amount of energy from fission.

I think that it's reasonable, then, to take 100 REM/h as a ballpark estimate for the dose rate from a Tory-IIc at 1 km.

Another similar back-of-the envelope estimate has been proposed by Scott Manley, who I suppose you are familiar with, in his recent Youtube video about Project Pluto. He quotes the lethal radius for radiation effects of the Davy Crockett mini-nuke at a quarter of a mile, and states that the Tory-IIc takes 100 seconds to yield the same amount of fission energy as the blast of that device. Source [time: 3m10s]

From this data, he also concludes that a lethal dose from a fly-by of a SLAM would not be possible. (He assumes h = 1000 ft)

by Giorgio Tiburzi (2018)

Project Pluto Reactor
Diameter57.25 in.
Fissionable Core47.24 in.
Length64.24 in.
Core Length50.70 in.
Critical Mass of Uranium59.90 kg.
Avg. Power Density10 MW/cubic foot
Total Power600 MW
Avg. Element Temperature2,330° F

Orion Bomber

This is from material from the Fourth Symposium on Advanced Propulsion Concepts parts i, iii, iii and from Aerospace Project Review Issue Volume 1, Number 5. As always, in the datablocks you see in on the edges of this page the values in black are from the source documents but the values in yellow are not. Yellow values are ones that I have personally calculated, sometimes using questionable assumptions. Yellow values are not guaranteed to be accurate, use at your own risk.

In March of 1965 the Orion program was pretty much over. Nobody was interested in a spacecraft powered by hundreds of atom bombs. In a frantic attempt to keep it alive, General Atomic released a report describing several potential military applications. Hey, Pentagon, here are some great serving suggestions for an Orion! Please don't let the program die.

It didn't work but you can't blame them for trying.

Reference Orion Configurations
Pusher Diameter (m)81012
Length (m)22.125.729.7
Thrust (N)2,360,0003,470,0004,320,000
Isp (sec)2,7203,3003,670
Exhaust Velocity (m/s)26,70032,40036,000
Weight (kg)81,700109,000172,000

The applications used all three of the standard Orion engines: eight, ten, and twelve meter pusher plate sizes. Since a nuclear launch was pretty much out of the question, each proposal used a stage of quick-and-dirty solid rocket clusters to loft the Orion to an altitude of 76,200 meters before the nukes started. The liftoff thrust-to-weight (T/W) ratio was 1.8 for all three Orion sizes. The solid rockets got the spacecraft up to 76,200 meters and 2,900 m/sec, the Orion drive kicked it the rest of the way into a 370 km orbit. The back of my envelope says the Orion has to expend 8,300 m/s of delta-V, some of that is aerodynamic drag and gravity drag.

8-meter Orion spacecraft would be lofted by a cluster of seven 120-inch solid rocket boosters, developed from the strap-on solid rockets used on the Titan III launch vehicle. They would have been more powerful than the Space Shuttle solid rocket boosters.

10-meter Orion spacecraft would be lofted by a cluster of four 156-inch solid rocket boosters. These were studied in the 1960s as possible strap-ons for the Saturn V, and as a cluster to replace the first stage of the Saturn Ib.

12-meter Orion spacecraft would be lofted by a cluster of seven 156-inch solid rocket boosters.

When the Orion drive started up at 76,000 m, its T/W was only 0.55. This meant a very ugly gravity tax, but the total payload delivered to orbit was maximized. Who cares about gravity tax, the Orion has delta-V to spare.

From a military standpoint, the Orion drive is attractive not only because of its high thrust and specific impulse. The drive is also resistant to damage. Fussy delicate chemical engines can be disabled with a handgun. Orion drives are built to be tough enough to withstand hundreds of impacts by nuclear explosions at close proximity. A handgun bullet will just bounce off. The enemy will have to use massive weapons in order to dent one of those babies. This is not as big a selling point for NASA, who generally does not have to worry about enemy spacecraft taking pot-shots at them.

For the same reason such drives are very easy to maintain and repair. You don't need needle-nosed pliers and micro-screwdrivers. A sledge hammer and a cold chisel will do. It helps that the engine is made of good ol' simple to fix steel, instead of cantankerous titanium or aluminum.

And unlike nuclear thermal rockets, Orions have very low residual radioactivity. It is safe to go out and work on an Orion drive only a few minutes after the last nuke exploded. Nuclear thermal rockets on the other hand will be unsafe to go near for a few thousand years.

Some of the applications had the Orion spacecraft stationed in space, others had them based on the ground. The former was basically using the Orion drive to loft an outrageously huge military space station into permanent orbit, in one piece. Applications stationed in space could be launched at leisure. Applications stationed on the ground on the other hand were a reaction force. The Orions would sit in their silos "on alert", ready to launch at a moment's notice. For space based system the primary concern is maneuverability and survivability. For ground based systems the primary concern is readiness.

The minor drawback of the Orion spacecraft's titanic mass is there was no practical way to land them back on Terra (short of lithobraking). Once they were launched into space, they stayed there. The crew was rotated by space shuttles or small reentry vehicles. Trying to land under Orion drive power is a very bad idea, especially on a planet with an atmosphere. The ship will be entering the center of each raging nuclear fireball with lamentable results.


  • Command/Control
  • Strategic Weapon Delivery ("Bomber")
  • Surveillance-reconnaissance
  • Space Defense
  • Orbit Logistics
  • Lunar Base Support
  • Space Rescue and Recovery
  • Satellite Support
  • R&D Laboratory


  • Emergency Command/Control
  • Space Interceptor
  • Damage Assessment
  • Space Rescue and Recovery
  • Satellite Support


ECCS Orion
Stage 2 Orion Engine
Pusher dia8 m
Isp2,720 sec
Exhaust Vel26,700 m/s
Thrust2,400,000 N
Stage 2
Payload Mass91,000 kg
Orion Engine Mass82,000 kg
Dry Mass172,700 kg
Pulse Units Mass290,300 kg
Wet Mass463,000 kg
Mass Ratio2.678
Total ΔV26,300 m/s
Reserve ΔV in LEO18,000 m/s
Stage 1 Chemical Engine
Exhaust Vel?
Stage 1
Payload Mass463,000 kg
Engine Mass?
Dry Mass?
Propellant Mass?
Wet Mass2,540,000 kg
Total ΔV3,100 m/s
Stack Height64 m
Stack Max Dia9.1 m

In case NORAD gets taken out by a dastardly nuclear first strike on the United States, the ECCS Orion was designed to survive in its secret armored launch silo. It would boost into orbit and take over NORAD's functions, coordinating the nuclear retaliation.

Actually the plan was to launch before the enemy bombs actually hit the ground. NORAD can probably predict it will be unlikely to survive an incoming nuclear strike long before the bombs actually arrive.

The ECCS was housed in an 8-meter Orion. The surface geometry was smooth to avoid creating shot-traps, since an enemy would target an ECCS with lots of hostile weapons fire. After expending all those extra nukes to obliterate NORAD the enemy will be obligated to destroy all the ECCS NORAD-back-ups, otherwise they will have wasted all those warheads and have nothing to show for it.

Since the ECCS would operate beyond Terra's magnetosphere, the crew would need radiation shielding from galactic cosmic rays. Not to mention enemy nuclear warheads, possibly including enhanced radiation weapons.

The wet mass was 2,540,000 kg (5,600,000 lbs), of which 91,000 kg (200,000 lbs) was payload (apparently "payload" is the dry mass of the Orion spacecraft, without any nuclear pulse units. At least that's what my calculation suggest). Stack height with solid rocket boosters was 64 m (210 ft) (cluster of seven 120-inch solid rockets) and a maximum diameter of 9.1 m (30 ft). The boosters loft the Orion to an altitude of 76.2 km (250,000 ft). Then the 8-meter Orion engine uses its 2,400,000 N (530,000 lbf) of thrust and 2,750 seconds of Isp to get the rest of the way to a 370 km (200 nautical mile) circular orbit. At this point it would still have a delta-V reserve of 18,000 m/sec (60,000 ft/sec) for further maneuvers. The reserve can be used to provide orbit altitude and plane changes to provide the most effective surveillance coverage and to evade hostile weapon interceptions.

The ECCS will require a silo only slightly larger than a standard ATLAS or TITAN ICBM silo.

The ECCS would carry a crew of from ten to twenty, with lots of advanced surveillance and communication equipment. Average mission was 30 days, with provisions for up to 60 days. Radiation shielding on the order of 244 kg/m2 (50 lb/ft2) would be around all command/control and crew operating station, to protect against galactic cosmic rays and possible hostile enhanced radiation weapons. The structure, life support systems, and attitude jet fuel will provide an additional 244 kg/m2 for a total of 488 kg/m2 (100 lb/ft2). By way of comparison, a storm cellar protecting the crew from a significant solar storm should have at least 5,000 kg/m2.

Several ECCS would be on constant standby in their silos. If nuclear war was immanent one would be launched as a show of force, demonstrating that the US was "not unprepared to defend itself." Along with a diplomatic reminder that there are more ECCS where that came from.

One would NOT be launched if it was only a time of crisis instead of immanent war. That would be provocative, and could precipitate matters. It is difficult to convince the enemy to stand down from DEFCON 2 when you are massing troops on their boarder, so to speak.

Deployed in low orbit allows immediate surveillance coverage of enemy territory and maximum image resolution. Deployed in remote orbits provides broader coverage of the planet's surface and also allows early warning of incoming hostile weapons fire aimed at the ECCS.


Stage 2 Orion Engine
Pusher dia10 m
Isp3,300 sec
Exhaust Vel32,900 m/s
Thrust3,500,000 N
Stage 2
Payload Mass136,000 kg
Orion Engine Mass110,000 kg
Dry Mass246,000 kg
Pulse Units Mass354,000 kg
Wet Mass600,000 kg
Mass Ratio2.439
Total ΔV29,300 m/s
Reserve ΔV in LEO21,000 m/s
Stage 1 Chemical Engine
Isp294 sec
Exhaust Vel2,880 m/s
Stage 1
Payload Mass600,000 kg
Engine Mass936,000 kg
Dry Mass1,536,000 kg
Propellant Mass2,964,000 kg
Wet Mass4,500,000 kg
Mass Ratio2.930
Total ΔV3,100 m/s
Stack Height96 m
Stack Max Dia10 m

This is similar to the ECCS but with important differences. It is stationed in space. It is intended for permanent operations, not just for 30 days. It is larger, requiring a 10-meter Orion engine.

Three of these would be placed in geosynchronous orbit to provide constant global surveillance. They would augment their coverage via inter-ship relay. This will allow the ships to randomly change their positions and frustrate enemy weapons interceptions, yet still maintain coverage. One ship will be the "flagship" but others could take over if the flagship is disabled.

The wet mass was 4,500,000 kg (10,000,000 lbs), of which 136,000 kg (300,000 lb) was payload. Stack height with the stage 1 solid rocket boosters was 320 feet (cluster of four 156-inch solid rockets) and a maximum diameter of 96 m (33 ft). The solid rocket booster has a mass of 3,900,000 kg (8,500,000 lbs). At an altitude of 76.2 km (250,000 ft) the 10-meter Orion engine uses its 3,500,000 N (780,000 lbf) of thrust and 3,300 seconds of Isp to get the rest of the way to a 42,162 km (22,766 nautical mile) geosynchronous orbit. At this point it would still have a delta-V reserve of 21,000 m/s (70,000 ft/sec) for further maneuvers, though in theory it is in its forever home.

Actually, since the SSCCS will be launched in leisurely times of peace instead of under the urgent pressures of impending nuclear armageddon, solid rocket boosters are not needed. Instead the more sophisticated (but more time consuming) liquid-fueled Saturn V's S-IC stage could be used. Especially if NASA ever manged to make the S-IC recoverable, which as SpaceX has demonstrated drastically lowers the launch cost. Such a stack would have a wet mass of 3,300,000 kg (7,200,000 lbs).

The SSCCS will require about 3 megawatts with a peak of 9 MW or so for the surveillance and communication systems. This can be provided with RTG or other advanced power source. The crew will number from 20 to 30, with six-month tours of duty. The SSCCS will stay on location for their operational lifetimes, 15 to 20 years. The long lifetimes are due to the fact that upgrading obsolete surveillance and comm systems is a snap when you are using Orion drive cargo ships. No matter how much the replacements weigh. The communication/surveillance section is basically a chassis accepting plug-in replaceable modules.


Stage 2 Orion Engine
Pusher dia12 m
Isp3,670 sec
Exhaust Vel36,000 m/s
Thrust4,300,000 N
Stage 2
Payload Mass136,000 kg
Orion Engine Mass170,000 kg
Dry Mass306,000 kg
Pulse Units Mass424,000 kg
Wet Mass730,000 kg
Mass Ratio2.386
Total ΔV31,300 m/s
Reserve ΔV in LEO23,000 m/s
Stage 1 Chemical Engine
Exhaust Vel?
Stage 1
Payload Mass730,000 kg
Engine Mass?
Dry Mass?
Propellant Mass?
Wet Mass6,800,000 kg
Mass Ratio?
Total ΔV3,100 m/s
Stack Height88 m
Stack Max Dia12 m

Strategic Weapon Delivery AKA raining nuclear warheads onto the nation that attacks us.

This would require a full blown 12-meter Orion engine, because nuclear missiles are very heavy. And because you want to carry as many as you possibly can.

The wet mass was 6,800,000 kg (15,000,000 lbs), of which 136,000 kg (300,000 lbs) was payload. Stack height with the solid rocket boosters was 88 m (290 ft) (cluster of seven 156-inch solid rockets). At an altitude of 76.2 km (250,000 ft) and a speed of 3,100 m/s (10,000 ft/sec) the 12-meter Orion engine uses its 4,300,000 N (970,000 lbf) of thrust and 3,670 seconds of Isp to get the rest of the way to its patrol orbit. At this point it would still have a delta-V reserve of 23,000 m/s (75,000 ft/sec) for further maneuvers.

  • At A the SSSWD boosts into LEO (370 km) with solid rockets and Orion drive. The crew does a systems checkout.
  • At B burns into a Hohmann transfer (blue arc)
  • At transfer apogee C it burns to circularize the orbit. SSSWD is now in a 190,000 km circular orbit (green circle)
  • At D burns to enter Patrol orbit (red ellipse). Orbit has a perigee of 190,000 km and apogee of 410,000 km (a 190,000-410,000 km Terran orbit). The orbital period is 18.9 days

The crew will number 20 or more. A semi-closed ecological system will be used to permit a six-month tour of duty, with an emergency capacity of one year. It would require about 1 megawatt of onboard power for ship systems.

The interesting details about the weapons loadout are either not defined or classified. They are not in the report at any rate. Drat!

Defensive weapons include decoys and antimissile weapons. Defensive weapons are carried because bombers are the enemy's prime targets. The enemy knows that every single strategic weapon a SSSWD carries is a mushroom cloud with their name on it.

The strategic nuclear weapons were to be carried internally to allow easy access for maintenance. That way the technician wouldn't have to wear a space suit. The weapons are probably either megaton-range "city-killer" nukes, or MIRVs of deci-megaton-range. For reference, the original Minuteman-II ICBM carried a 1.2 megaton W56 thermonuclear warhead. The Minuteman-III had a MIRV bus carrying three 0.17 megaton W62 thermonuclear warheads (170 kilotons). Scott Lowther's recreation of the SSSWD carries 25 MIRVs, each with three warheads.

The nukes could be launched in either of two ways. [1] warheads could be mounted on missiles, launched from deep space, and guided to their targets. [2] the Orion bomber could use its 23,000 m/s of delta-V to enter a close hyperbolic flyby of Terra and release the warheads when near Terra.

On the one hand, the first option means the Orion does not have to get close to the target and be exposed to hostile weapons fire. On the other hand the missiles will have very limited delta-V because you cannot cram a full sized ICBM into the Orion bomber. True, the missiles will start with the Orion's orbital velocity but still. Since the paper cites enemy interceptor missiles requiring a day or two to reach the Orion bomber, presumably any missile the SSSWD launched will require a similar amount of time to reach the enemy cities.

The second option means the Orion bomber has to go into harms way. The up side is it can use its awesome amount of delta-V to deliver the MIRVs ballistically. And it probably can deliver the warheads to the target much quicker than any missile. One can just imagine the enemy generals freaking out at the sight of a three-hundred-ton spacegoing ICBM-farm dive-bombing you at hyperbolic speeds on a trail of freaking nuclear explosions while machine-gunning your continent with city-killer nukes.

According to the paper, a fleet of about 20 spacecraft would be deployed. Presumably this will ensure that there will always be several bombers close enough so that the MIRVs travel time will be short enough to give the enemy a major strategic problem. If my slide-rule is not lying to me, a 190,000 km-410,000 km orbit has an orbital period of 1,635,282 seconds or 18.9 days. With 20 SSSWD evenly spaced, that would have a bomber passing through perigee every 81,764 seconds or every 22.7 hours. I picked 410,000 km as a nice round value "beyond Luna" since the report did not give a precise figure. They might have selected an apogree figure to make a bomber pass through perigee once a day.

Siteing strategic nuclear weapons in deep space would be a major escalation of the nuclear arms race. Such Orion bombers are much more difficult to attack, compared to ICBMs in silos or nuclear submarines. It would require entirely new strategic planning and weapons systems. The high orbits mean that enemy weapons would require a day or more to reach the orbiting Orion bombers. If the enemy wishes to take out the Orion bombers simultaneously with the US ICBM silos and nuclear missle submarines, they will be forced to give the US a day or more of warning time. This sort of spoils the surprise of a first strike. In addition the long warning gives the Orion bombers ample time to take evasive action and/or deploy decoys and antimissile weapons.

On the minus side, such a drastic escalation may panic the enemy into starting a nuclear war before the Orion Bomber network was fully established. If the enemy is only half-panicked, they will probably start a crash-priority project to make their own Orion bomber network.

Asteroid Bombardment

If the attacker wants to just destroy the defender's civilization but does not want to necessarily make the defenders extinct or render the planet uninhabitable, asteroid bombardment might be just the thing. Now there is the chance of disrupting the ecosystem and rendering the planet temporarily uninhabitable, but at least it won't be radioactive.

Most solar systems have enough asteroids so the ammo is mostly free. All you have to supply is the delta-V to send them at the besieged planet at high velocity.

In a balkanized solar system, this is the reason for each space-faring nation to have their own Spaceguard. The idea is to prevent unauthorized changes in asteroid orbits. The idea for several independant national spaceguards is to keep all the spaceguards honest. Quis custodiet ipsos custodes? and all that.


     "What we're afraid of is a massive meteorite impact, something of asteroid size."
     The alien was silent for a time. Reynolds busied himself at the bar. Suddenly the alien said, "Thuktun Flishithy—Message Bearer—was docked to a moonlet of the ringed planet for many years. This many." The alien's trunk emerged from the mud, and he flexed a clump of four digits, three times. "Pushing. We were not told why. I once heard officers call the mass chaytnf."
     "What does it mean?"
     "It means this part of a fi." The alien rolled (and Sherry shied from a wave of mud). One broad clawed foot emerged.
     The sci-fi types all seemed to freeze in place; but Jenny didn't need their interpretation. Her hand closed painfully on Jack's arm. "My God. It's real. Of course, the Foot, they're planning to stomp us—"
     "They're talking too damn much."
     "Huh? The alien's talking a lot more than they are."
     The blurry voice from the TV set was saying, "It was not so large as many of the—asteroids—at the ringed planet. I think 8 to the 12th standard masses—"
     "Standard mass is your mass? About eight hundred pounds . . . Curtis took a pocket calculator out of his bush jacket. "Jesus! Twenty-seven billion tons!"
     Nat Reynolds said, "At . . . ten to twenty miles per second, that could—Harpanet, where are they going to drop it?"

(ed note: if I have not made a mistake in math, this will strike with force of about 1.25 x 1022 joules or 3,000,000 megatons. See boom table. Final crater diameter: 40.4 km, final crater depth: 901 meters, The volume of the target melted or vaporized is 78.2 km3. Roughly half the melt remains in the crater, where its average thickness is 144 meters. The novel says 4,000 megatons, so I'm only off by three orders of magnitude.)

     Commander Anton Villars stared through the periscope and tried to look calm. It wasn't easy. An hour before the message had come to USS Ethan Allen. The long-wave transmitters were reliable but slow. The message came in dots and dashes, code tapped out and taken down to be put through the code machines. It couldn't be orders to attack the Soviet Union. There was no Soviet Union. Villars had been prepared to launch his Poseidon missiles against an unseen enemy in space. Instead:
     Safe? From four thousand megatons? There wasn't any safety. Villars' urge was to submerge and flee at flank speed.
     Off to starboard, the island of Rodriguez blazed with the colors of life. Jungle had long since given way to croplands. In the center bare rock reared sharply, a peak a third of a mile high. Waves broke over a surrounding coral reef. That reef would provide more cover when the tsunami came, but it was a danger too.
     Fishing boats were straggling in through the reef. Probably doomed. There was nothing Villars could do for them.
     It was just dusk. Clouds covered the sky. It would be difficult to see anything coming. Four thousand megatons. Bigger than any bomb we ever dreamed of, much less built.
     The crew waited tensely. John Antony, the Exec, stood close by.
     "About time," Antony said.
     "If their estimate was on."
     "If their time was off, so were their coordinates."
     I know that. I had the same instructor at Annapolis as you did.
     Somebody laughed and choked it off. The news had filtered through the ship, as news like that always did.
     The cameras were working. Villars wondered how many would survive. He peered through the darkest filter available. Four thousand megatons . . .
     Suddenly the clouds were blazing like the sun. "First flash at 1854 hours 20 seconds," he called. "Log that." Where? Where would it fall?
     All in an instant, a hole formed in the clouds to the northeast, the glare became God's own flashbulb, and the cameras were gone. "Get those other cameras up," Villars bellowed at men who were already doing that. His right eye saw nothing but afterimage. He put his left to the periscope.
     He saw light. He squinted and saw light glaring out of a hole in the ocean. A widening hole in the ocean, with smoothly curved edges; wisps of mist streaming outward, and a conical floodlight beam pointing straight up. The beam grew wider: the pit was expanding. Clouds formed and vanished around a smoothly curved wall of water sweeping smoothly toward the sub.
     The rim of a sun peeped over the edge.
     "I make it about forty miles east northeast of present position. Okay, that's it." Villars straightened. "Bring in the cameras. Down periscope. Take us to ninety feet." How deep? The further down, the less likely we'll get munched by surface phenomena, but if those tsunamis are really big they might pile enough water on top of Ethan Allen to crush us. "Flank speed. Your course is 135 degrees." That leaves us in deep water and puts Rodriguez between us and that thing, for whatever good it'll do.
     So we've seen it. A sight nobody ever saw—well, nobody who wrote it down, anyway. Now all I have to do is save the ship.
     Ethan Allen was about to fight the biggest tsunami in human history—and just now he was broad on to it. He glanced at his watch. Tsunamis traveled at speeds from two hundred to four hundred miles an hour. Call this one four. Six minutes . . .
     "Left standard rudder. Bring her to 85 degrees."
     "Bring her to 85, aye, aye," the quartermaster answered.
     "Warn 'em," Villars said.
     "Now hear this. Now hear this. Damage control stations. Stand by for depth charges."
     Might as well be depth charges . . .
     The ship turned.
     It surged backward. Villars felt the blood rushing into his face. Somewhere aft, a shrill scream was instantly cut off, and the Captain heard a thud.
     Minutes later: "There's a current. Captain, we're being pulled northeast."
     "Steady as she goes." Goddam. We lived through it!

     The contorted moonlet dropped away, dwindled, vanished. Earth grew huge. A flashbulb popped above the Indian Ocean, and was replaced at once by a swelling, darkening fireball. Ring-shaped shadows formed and faded in and around it. Far from the central explosion, new lights blinked confusingly in points and radial streaks.
     The Earth's face streamed past, terrifyingly close but receding now. A wave in the cloud cover above the Indian Ocean raced outward, losing its circular shape as it traveled. Northward, it took on a triangular indentation, as if the edge of a blanket had snagged on a nail.
     "India," Dawson said. "How fast are you running this tape?"
     "Thirty-two times normal," Tashayamp answered.
     "What is . . . that?" Alice asked.
     "Land masses. The tsunami distorts the clouds," Arvid said.
     "So does the ocean floor," Dawson amplified, "but not as much. That's India going under. Those flashes would have been secondary meteors, debris, even water from the explosion thrown out to space and reentering the atmosphere."
     That's India going under. Good-bye, Krishna, and Vishnu the elephant god. Jeri shuddered. "Dave took me to India once. So many people. Half a billion."
     Arvid stood near. She felt his warmth and wanted to be closer to him.
     Tashayamp said, "Number?"
     Arvid said, "Eight to the eighth times eight times three."

(ed note: 402,653,184)

     "Human fithp in India? Where the wave goes now?"
     "Yes." ...
     ...The distortion in the clouds swept against Africa, then south. Here was clear air, and a ripple barely visible in the ocean . . . but the outline of the continent was changing, bowing inward.
     "Cape of Good Hope," Jeri muttered. She watched the waves spread into the Atlantic. Recorded hours must be passing. She found herself gasping and suspected she had been holding her breath. The waves were marching across the Atlantic, moving on Argentina and Brazil with deceptive slowness and a terrible inevitability.
     Cloud cover followed, boiling across the oceans, reaching toward the land masses. "My God," Jeri said. "How could you do this?"
     "It is not our choice," Raztupisp-minz said. "We would gladly have sent the Foot safely beyond your atmosphere, but your fithp would not have it so."
     "Look what you made me do," Alice said in a thick, self-pitying whine. Her voice became a lash. "All the sickies say that—the rogues say that when they've done something they're ashamed of. It was somebody else's fault."
     "They can say all they like," Carrie Woodward said. "We know. They came all the way from the stars to ruin the land."
     "You should not say such things," said Takpusseh. "You do not want this to happen again. You will help us."
     "Help? How?" Dawson demanded.
     "You, Wes Dawson, you tell them. More come."
     Dmitri spoke again in Russian. Arvid shuddered.
     The screen changed again. Clouds moved so unnaturally fast that Jeri thought they were still watching a tape until Takpusseh said. "That is now. Winterhome."
     Earth was white. The cloud cover was unbroken.
     "Rain. Everywhere," Nikolai said. "The dams are gone. There will be floods."

From FOOTFALL by Larry Niven and Jerry Pournelle (1985)

Laser Bombardment

First off, laser weapons used for ship-to-ship combat in the vacuum of space can use whatever laser wavelength they feel like. But things change if you are using laser cannons on ground targets of a planet with an atmosphere.

Wavelengths shorter than 200 nanometers (ultraviolet, x-rays, and gamma rays) are absorbed by Terra's atmospheric gases (so they are sometimes called "Vacuum frequencies"). Note that once a section of atmosphere has been heated into a plasma by the laser (or whatever) things change. Plasma is transparent to vacuum frequencies while non-vacuum frequences are absorbed.

Understand that a tunnel of plasma is only going to last for a fraction of a section so if you want to put a second laser bolt down it you'd better hurry.

And some wavelengths of infrared are absorbed by water vapor in the air. On Terran type habitable planets, moist air is everywhere. Naturally once the water vapor has been heated into plasma, it isn't water vapor any more. Just oxygen and hydrogen ions. Sadly plasma also absorbs infrared.


In the past, I have advocated for using "cyan" (bluish-green) lasers for orbital bombardment of Earth, mainly because of graphs like this:

This image basically plots how much light of a given frequency reaches the ground. E.g. 1m-wavelength radio waves aren't absorbed at all, visible light is absorbed a little bit, and 10nm UV is completely absorbed. We want a frequency that is not absorbed very much, and as high as possible so that we don't suffer diffraction losses.

Cyan is a sweet spot in this image: it's the furthest-left trough (i.e., highest-frequency, and therefore lowest-diffraction, band that doesn't get outright absorbed), and it's the bottom of that trough (i.e., the least-absorbed within that band).

Well, lately I got flustered with this graph for being too coarse. This graph looks like a cartoon sketch! I went looking for a better source and, well, it turns out not to exist. I mean, I can find tons of graphs that look like this, but none that have reasonable resolution (and preferably, data, so that I could reproduce it myself).

In-fact, the only detailed data that people seem to have even collected is in certain frequency ranges, notably the IR bands (ref. HITRAN, GEISA, etc. datasets, and the many projects that use them). In-particular, I played with HITRAN's buggy API for a while until I figured out they don't actually have data on the whole spectrum. However, I did find a graph:

It's basically the interesting section of the previous graph (inverted since it is transmittance rather than absorbance). It goes to 150nm, shorter than which we can be fairly confident will be absorbed by the atmosphere (such are called "vacuum frequencies" for a reason. You can still get sunburned by UV, so I assume that's basically the 300nm-400nm section of the last image that's still UV, but also nonzero transmission).

Now let's consider diffraction. To first order:

(divergence half angle) = (wavelength) / (π (aperture radius))
(spot radius) = (distance) (divergence half angle)
(irradiance) = (transmittance) (laser power) / (π (spot radius)²)
(damage rate) ∝ (irradiance)
(damage rate) ∝ π (transmittance) (laser power) ( (aperture radius) / ( (distance) (wavelength) ) )²

Considering distance, aperture radius, and available power to be constants with respect to the wavelength we choose, we can see that:

(damage rate) ∝ (transmittance) / (wavelength)²

To maximize damage rate, we simply have to take that graph and divide it by the x-axis-squared. Since the data was not available, I digitized the chart using WebPlotDigitizer, copied the approximate data out, and plotted it myself. In the graph below, you can see the original data in blue, and the effect of the division in orange.

The graph's peak says that a wavelength of about 400nm is optimal for orbital bombardment!

We can see that cyan (about 480nm) is close, at about 92% relative effectiveness. At least it's a better recommendation than green (which I also see bandied about: 532nm, 83% effectiveness).

400nm is pretty much the border between violet and ultraviolet, but in human perceptual terms it's not a binary cutoff. Under well-lit viewing conditions, the human eye sees best at about 555nm. At 400nm, a light source appears about 0.04% as bright—which might sound small, but the human visual system is logarithmic, and anyway a typical orbital-bombardment laser would use extremely high powers. As another reference: I've myself have 405nm lasers (expected 0.065% as bright) and they're plenty visible.

How general is this? Technically, it applies to surface-to-orbit/orbit-to-surface bombardment at a 70° surface-to-horizon angle. The main optical variation in the atmosphere is moisture content, but it turns out that water's transmission (for liquid or vapor) is actually coincidentally near-maximum at 400nm, so if anything more moisture will make every other wavelength even worse.

One thing that doesn't generalize is firing lasers from points on the surface to other points on the surface. In the first case, the exact height of the orbit didn't matter (it's orbital bombardment; one assumes you're above nearly all the atmosphere), but here, the path length within the atmosphere varies, meaning that the amount of absorption that you suffer at a given wavelength does too.

Given a particular range, one could measure/compute a graph like the above and get the optimal wavelength. Longer ranges will absorb more, making having a higher transmission coefficient (lower absorption coefficient) more important. But, because the Beer-Lambert law is nonlinear, there's little we can say else generally about such a graph.

Note: after the fact, I noticed that "MODTRAN", named on the source graph, is the name of a software package that computes such spectra. If it didn't cost $1800+, it'd be perfect. Of course, I could also wonder why no one hasn't just uploaded a reasonable-quality graph ever.

From a Google+ post by Ian Mallett (2018)


The US Navy is exploring the feasibility of using a high energy laser weapon as a ship-borne self-defense system against sea-skimming cruise missile attacks. Since the attenuation of laser energy by the atmosphere is the highest at low altitudes and varies with frequency, the selection of appropriate wavelengths becomes critical for a laser weapon to be effective. A high energy free electron laser (FEL) is suitable for employment in the envisaged role because it can be designed to operate at any desired frequency and, to a degree, is tunable in operation. This study aims to determine the optimal atmospheric windows for high energy, pico second, short pulse lasers.

Suitable wavelength windows were selected from either the Jan 1 or July 1, 2004 spectra for the date with a narrower transmittance window by meeting the following two criteria:

  1. Transmittance value of at least 90%, 95% and 99% respectively over a 10 km long, 10 m high horizontal path.
  2. Absorption coefficient value of less than 0.02 per km.

Table 5 summarizes the suitable wavelengths. The first four bands from 0.95 μm to 2.5 μm were able to meet the criteria of at least 90% transmittance and absorption coefficient of not more than 0.02 per km. However, there are no wavelengths in the 3.45 to 4.16 μm band that can meet the two specified criteria. The best wavelength window for this band is chosen for 70% transmission and absorption coefficient less than 0.04 per km.

From Table 5, the optimal wavelength windows for molecular atmospheric absorption are between 1.03 μm and 1.06 μm, and around 1.241 and 1.624 μm. This band provides a transmittance of more than 99%. However, as noted earlier, the main drawback of operating in a lower wavelength band is the strong extinction of energy from aerosol scattering.

Table 5.
Suitable wavelength windows for various values of T(z) in μm
T(z) > 90%
αabs < 0.01/km
T(z) > 95%
αabs < 0.005/km
T(z) > 99%
αabs < 0.001/km
T(z) > 70%
0.95 to 1.11 μm0.990 - 1.0750.992 - 0.998
1.002 - 1.006
1.01 - 1.067
1.030 - 1.060N/A
1.11 to 1.33 μm1.230 - 1.260
1.271 - 1.283
1.235 - 1.2561.241N/A
1.47 to 1.82 μm1.530 - 1.6801.535 - 1.565
1.58 - 1.595
1.610 - 1.660
2 to 2.5 μm2.125 - 2.140
2.220 - 2.245
3.45 to 4.16 μmN/AN/AN/A3.91 - 3.94

Summary of suitable wavelength bands for FEL operation for a 10 km horizontal path, 10 m above the ocean with no aerosol extinction.

(ed note: 400 nm equals 0.4 μm)


The possibility of using a laser beam as a ship-borne self-defense weapon has become more feasible with recent advancements in laser technology. The advantages of a high energy laser as a weapon are its key attributes of speed-of-light response, ability to handle fast maneuvering and crossing targets, deep magazine capacity, minimal collateral damage, target identification and adaptability for lethal to non-lethal employment. The attenuation of laser energy by the atmosphere is a result of molecular attenuation and scattering. Atmospheric scattering mainly disperses the energy of the laser beam but molecular absorption heats the atmosphere, reducing the index of refraction and thereby creating thermal blooming. The FEL has potential as a shipborne weapon system because it can be designed to operate at any desired frequency and, to a degree, is tunable in operation. The ability to select an operating frequency greatly enhances the successful propagation of the laser beam through the relatively dense air at low altitudes.

The objective of this thesis was to determine optimal operating wavelength bands for a high energy FEL weapon between 0.6 μm and 4.2 μm using the US Air Force PLEXUS Release 3 Version 2 program to set up MODTRAN 4 Version 2 and FASCODE 3 atmospheric transmission programs. Since PLEXUS and its user interface are export limited, this thesis was restricted to processing the MODTRAN and FASCODE output files. These codes allow for complex atmospheric transmittance and radiance calculations based on absorption and scattering phenomena for a variety of path geometries. The input parameters chosen for the simulation runs are meant to represent likely operational scenarios for ship self defense against a cruise missile attack. The main consideration was a 10 m altitude horizontal transmission path. Korea, Taiwan and the Persian Gulf were the three geographical areas chosen for the study. The effect of a short FEL laser pulse was modeled by convolving a normalized Gaussian frequency spectrum with the MODTRAN and FASCODE transmission and absorption coefficient spectra. The result of the convolution operation averages the transmittance values over a number of wavenumbers. The amount of averaging increases as the length of the FEL pulse decrease.

2. FASCODE Results

The higher resolution 0.1 cm-1 FASCODE was used to conduct further analysis on five selected bands or “windows” found from the MODTRAN results. Using the FASCODE aerosol extinction output file results, absorption coefficients for each wavenumber (or spectral frequency) were calculated. The molecular absorption coefficient is a key parameter for thermal blooming calculations. Data for the absorption coefficient were also used to compute the transmission spectrum for molecular absorption only. Using the transmission spectrum and absorption coefficient graphs, the optimal wavelength bands for employment of FEL at low altitudes were identified and summarized in Table 5. The four main bands of 0.95 to 1.11 μm, 1.11 to 1.33 μm, 1.47 to 1.82 μm, and 2 to 2.5 μm contain quite a number of suitable wavelengths that allow transmittance of at least 90% for a 10 km path and have absorption coefficient values of 0.02 per km or less. For a more stringent requirement of at least 99% transmittance, the suitable wavelength windows are between 1.03 to 1.06 μm and around 1.241 and 1.624 μm. However, the main concern for laser transmission through the atmosphere in the 1 μm region is the strong aerosol extinction.

Burning Glass

This is a ludicrous orbital bombardment weapon popular in science fiction in the early previous century. Presumably some cruel little boy incinerated some ants on a sunny day using their magnifying glass, and when they grew up to write science fiction they figured scaling it up would be a good idea. Upscale the ants into enemy cities, and upscale the magnifying glass into a titanic parabolic mirror. In space.

TV Tropes calls it the Solar-Powered Magnifying Glass

The main drawback is the mirror would be a hard-to-miss kilometer wide target possessing all the tensile strength of aluminium foil. One nuclear missile and months of work instantly frizzles up like, well, ants under a magnifying glass.

This material is presented here mostly for its entertainment value.


Heat ray

Archimedes may have used mirrors acting collectively as a parabolic reflector to burn ships attacking Syracuse. The 2nd century AD author Lucian wrote that during the Siege of Syracuse (c. 214–212 BC), Archimedes destroyed enemy ships with fire. Centuries later, Anthemius of Tralles mentions burning-glasses as Archimedes' weapon. The device, sometimes called the "Archimedes heat ray", was used to focus sunlight onto approaching ships, causing them to catch fire. In the modern era, similar devices have been constructed and may be referred to as a heliostat or solar furnace.

This purported weapon has been the subject of ongoing debate about its credibility since the Renaissance. René Descartes rejected it as false, while modern researchers have attempted to recreate the effect using only the means that would have been available to Archimedes. It has been suggested that a large array of highly polished bronze or copper shields acting as mirrors could have been employed to focus sunlight onto a ship.

A test of the Archimedes heat ray was carried out in 1973 by the Greek scientist Ioannis Sakkas. The experiment took place at the Skaramagas naval base outside Athens. On this occasion 70 mirrors were used, each with a copper coating and a size of around five by three feet (1.5 by 1 m). The mirrors were pointed at a plywood mock-up of a Roman warship at a distance of around 160 feet (50 m). When the mirrors were focused accurately, the ship burst into flames within a few seconds. The plywood ship had a coating of tar paint, which may have aided combustion. A coating of tar would have been commonplace on ships in the classical era.

In October 2005 a group of students from the Massachusetts Institute of Technology carried out an experiment with 127 one-foot (30 cm) square mirror tiles, focused on a mock-up wooden ship at a range of around 100 feet (30 m). Flames broke out on a patch of the ship, but only after the sky had been cloudless and the ship had remained stationary for around ten minutes. It was concluded that the device was a feasible weapon under these conditions. The MIT group repeated the experiment for the television show MythBusters, using a wooden fishing boat in San Francisco as the target. Again some charring occurred, along with a small amount of flame. In order to catch fire, wood needs to reach its autoignition temperature, which is around 300 °C (570 °F).

When MythBusters broadcast the result of the San Francisco experiment in January 2006, the claim was placed in the category of "busted" (or failed) because of the length of time and the ideal weather conditions required for combustion to occur. It was also pointed out that since Syracuse faces the sea towards the east, the Roman fleet would have had to attack during the morning for optimal gathering of light by the mirrors. MythBusters also pointed out that conventional weaponry, such as flaming arrows or bolts from a catapult, would have been a far easier way of setting a ship on fire at short distances.

In December 2010, MythBusters again looked at the heat ray story in a special edition entitled "President's Challenge". Several experiments were carried out, including a large scale test with 500 schoolchildren aiming mirrors at a mock-up of a Roman sailing ship 400 feet (120 m) away. In all of the experiments, the sail failed to reach the 210 °C (410 °F) required to catch fire, and the verdict was again "busted". The show concluded that a more likely effect of the mirrors would have been blinding, dazzling, or distracting the crew of the ship.

From the Wikipedia entry for ARCHIMEDES


But like any other technical achievement the space mirror could also be employed for military purposes and, furthermore, it would be a most horrible weapon, far surpassing all previous weapons. It is well known that fairly significant temperatures can be generated by concentrating the sun's rays using a concave mirror (in a manner similar to using a so-called "burning glass"). Even when a mirror has only the size of the human hand, it is possible to ignite a handheld piece of paper or even wood shavings very simply in its focus (Figure 95).

Imagine that the diameter of a mirror of this type is not just 10 cm, but rather several hundreds or even thousands of meters, as would be the case for a space mirror. Then, even steel would have to melt and refractory materials would hardly be able to withstand the heat over longer periods of time, if they were exposed to solar radiation of such an enormous concentration.

Now, if we visualize that the observer in the space station using his powerful telescope can see the entire combat area spread out before him like a giant plan showing even the smallest details, including the staging areas and the enemy's hinterland with all his access routes by land and sea, then we can envision what a tremendous weapon a space mirror of this type, controlled by the observer in orbit, would be!

It would be easy to detonate the enemy's munitions dumps, to ignite his war material storage area, to melt cannons, tank turrets, iron bridges, the tracks of important train stations, and similar metal objects. Moving trains, important war factories, entire industrial areas and large cities could be set ablaze. Marching troops or ones in camp would simply be charred when the beams of this concentrated solar light were passed over them. And nothing would be able to protect the enemy's ships from being destroyed or burned out, like bugs are exterminated in their hiding place with a torch, regardless of how powerful the ships may be, even if they sought refuge in the strongest sea fortifications.

They would really be death rays! And yet they are no different from this lifegiving radiation that we welcome everyday from the sun; only a little "too much of a good thing." However, all of these horrible things may never happen, because a power would hardly dare to start a war with a country that controls weapons of this dreadful nature.

(ed note: The above section, translated into English appeared in Science Wonder Stories September 1929)

(The Problem of Space Travel: The Rocket Motor) by Hermann Noordung (1929)

In the question of the material of this reflector, it is clear that 1) no oxygen mst be present, and 2) it must heat up but little itself. It will remain colder if we leave the back side rough or even paint it black. As material, I would suggest sodium which, under the respective conditions, has a specific weight of 1, considerable tensile strength, and a silvery lustre. It can be taken along in large pieces by the shigle rockets and, since it still has the usual temperature up above, can there be rolled out to sheeting or pressed out as wire or strap from the rocket. Joining of the single pieces as well as polishing can be done by men in divers' suits. If the reflecting plate is 0.005 mm thick and the wires, etc., have the sane mss as the plate, the whole weighs 10 g per square metre or 100 kg per hectare. With regular rocket traffic to the observer station, the ascent of one rocket, which, beside all else, can carry up 2,000 kg of sodium, costs 8,000 to 60,000 Mark all told. Thus, one hectare of reflector costs at the most 3,500 Mark altogether. If we figure that 1 hectare of reflector surface could make 3 hectares of polar land arable, we see that a time my come when this reflector and the whole invention becomes a paying proposition.

In this way, a reflector 100 km in diameter would, at the most, cost 3 billion Mark and, if 100,000 kg of sodium were taken a loft every week, it would require ca 15 years to build it. Since such a reflector could, unfortunately, also have high strategic value (munitions factories can be exploded with it, tornadoes and thunderstorms produced, marching troops and their reserves destroyed, whole cities burned, and generally the greatest of damage done) the possibility is not excluded that one of the civilized states will make use of this invention in the foreseeable future, the more so since a large part of the invested capital could also bear interest in peace time.

(Ways to Spaceflight) by Hermann Oberth (1929)

On our back cover this month artist Julian S. Krupa has painted his conception of the most powerful weapon that could ever be devised. He has envisioned an artificial satellite that could be built in space and set to circling the earth just as the moon does, on an orbit perhaps 10,000 miles above the surface, well out of the atmosphere, and at a height best calculated to make it effective over a wide radius. Its potency is manyfold.

First, and primarily, it is a sun power machine. It utilizes the rays of the sun in a very simple manner, yet an extremely powerful one. We all have used a small magnifying glass, or a concave mirror to concentrate the rays of the sun. We all know how easy it is to burn a piece of paper, or wood with a mirror only an inch or two in diameter. Therefore, all these giant mirrors, concentrating sunlight on a single spot, would create a heat ray far beyond the imaginings of any science fiction writer in its deadly effectiveness.

In the accompanying illustration, Krupa has shown the space devastator in operation, sending a ravaging beam of terrible heat down upon a defenseless city 10,000 miles below. With such a threat hanging over it, what nation could afford to become a belligerent? It would be forced to settle its differences in a peaceful manner, according to the dictates of the committee, country, or police force placed in control of the space devastator. War would be impossible with such a potent "big stick" to hold over ambitious warlords and dictators. (note the blind assumption that ambitious warlords and dictator would never be in control of the space devastator. Or that the committee, country, or police force would never be controlled by some evil corporation that purchases politicians.)

Second, and perhaps more important, is the use of this artificial satellite in peaceful pursuits. There are numberless tasks it could perform. It could provide daylight in a normal manner, impossible to differentiate from the real thing. It could provide daylight illumination on any area, during times of flood, disaster, storm, or tragedy where daylight would be a vast help in rescue work.

It could control weather to a great degree, breaking up storm formations, cloud areas, or stopping blizzards. Conversely, it could create cloud formations by drawing up ocean moisture. It could provide aid to crops needing sunlight. It could melt snow from storm-bound cities. (yes indeed it could warm the globe…)

Imagine a destructive hurricane, sweeping in from the sea, toward the large cities of Florida. It could be driven like a herd of helpless cattle before the intense heat of the rays from the space devastator. It could even be destroyed, dissipated, halted in its progress.

Even the tremendous cost of this artificial satellite would be a mere trifle beside the savings it could effect, and the wealth it could create. As a guardian angel in the prevention and lessening of disaster, its value would be inestimable.

The savings in electrical power in lighting a great city would be enormous. Also, power could be generated in enormous amounts through the building of giant steam generators in isolated areas. Heat from a concentrated sunbeam would provide steam to operate giant turbines. Sun power stations would supplant water power stations, at a much cheaper original cost and upkeep.

Other strange uses, of great practicality, would be numerous. Icebergs could be melted and destroyed as a menace to shipping. A northern shipping route could be kept open the year around. Arctic ship travel could be made possible. Jungle lands could be cleared by the simple expedient of burning away the jungle, leaving a rich ashy loam of great agricultural value (actually cleared jungle land is almost totally agriculturally worthless. And it is too bad if you render extinct some rare herb that contains a cancer cure or something).

Areas of disease and plague could be cleared of germs by constant sunlight. Malaria zones could be freed of mosquitoes. Health centers of constant sunshine could be operated.

The livable areas of the earth could be increased by thirty percent, by moderation of climate, control of ice and snow, and of rain. Deserts could be made livable through artificially induced rainfall. The Sahara, the Gobi, the American deserts could be made fruitful. Tobacco, cotton, corn crops could be controlled (very telling the relative ranking of crops there). Disastrous droughts, excess and ruinous rainfall could be prevented.

Third, assuming the foregoing to apply directly to the present, the future value of such a space machine can easily be imagined. Interplanetary travel would be vastly benefited by the facility of such stations as a means of communication between planets and space ships in the void. Signals would be sent by code light flashes, and range would be unlimited. Weather or static conditions would have no effect on communication by light rays between worlds.

Also, this machine would act as a spacial lighthouse, guiding incoming space ships to the proper landing areas. Ships not actually landing on the planet could also use the space devastator as a way station, discharging passengers or freight, to be relayed to earth in small rocket ships (oh yes, let's make the ultimate weapon into grand central station with zillions of people of all nations passing through. What could possibly go wrong? The only thing saving the situation is the zillions of spies and secret agents from various nations would be constantly tripping over each other.).

The problem of building such a space machine as this is not as complicated as it would seem. Once space travel is an actuality, materials could be transported to the orbit selected for the space devastator, and once placed in this position, would remain there. Workmen could assemble them in space, and the machine would be built on the "site." Once completed, it would be firmly anchored in its place, its course mathematically computed by astronomers, and its every function thereafter subject only to mathematical calculation. Not one, but many, serving humanity.

From SPACE DEVASTATOR by Julian Krupa (1939)

Here is the story of a future war; a war between Mars and Earth. Artist Paul has shown a possible weapon.

MODERN aviation, and the great success of aerial blitzkrieg warfare, has shown us that in the future, the rocket ship, and the space ship, will play a very important part in the wars of the future. We all hope that there will be no such wars, but judging from past experience, it seems as inevitable as the present war.

Let us try to imagine what a raid from space, say from Mars, would be like. First, let us picture the New York of the year 2000. It is a vast city, with tremendous skyscrapers, and it is Earth’s largest city. It is logical to assume that a smashing blow against such a gigantic metropolis as the city of that era will be, would play a great part in determining the outcome of such a future war. So, let us say that at high noon, we are flying over New York in our sport model racing plane. We have no thought of war in our mind, and all seems peaceful below.

But suddenly, above us, we hear a growing roar, and down from space dart three huge space ships. Space ships are not unusual, because in this world of the year 2000, space travel is an accomplished fact, and space liners ply the void just as airliners cross the oceans today. Therefore, we aren’t surprised.

But we are puzzled when the three ships take up position above the city, rather than landing at the space port. They form a ring, and begin to speed about in a huge circle.

From each ship a tiny beam breaks out, to meet in the middle. We see that some change is taking place in the atmosphere. By some electrical magic, a gigantic whirlpool, in disc-shape, is being formed out of the air. This disc is heated by electrical discharges, and to our amazement it grows until it becomes, in effect, a giant atmospheric lens, just as capable of concentrating the sunlight as a lens of glass would be.

As the atmospheric lens suddenly begins to send its ray of fiery sunlight down in concentrated fury, we realize the truth. New York is being raided by the Martians. And they are using the most horrible weapon ever devised.

Whole blocks of New York burst into flame, turn black as charcoal under the terrific heat. The city rapidly becomes overhung with a pall of smoke, and we realize that immense destruction is going on. This is terrible. New York is helpless beneath such a weapon.

Now, up from the city’s airports come the battle planes of our air force. But they are flying against the most powerful creations of the aviation industry. They are flying against atomic powered space ships.

Like deadly lances, the electrical rays leap out, catching our fighting planes, and explode their gasoline tanks. Down they go, flaming funeral pyres for the men in them.

What can we do?

But, as we hover in helpless horror, our own space-fighting craft arrive, speedy ships armed with powerful atomic cannons. But strangely, they do not attack the heavier armed battleships of space, with their deadly rays. Instead, as we wonder what is happening, they dart higher, up above the deadly lens, and from their bellies they loose a cloud of smoke. Back and forth they weave, forming a cloud blanket that cuts off the source of the great atmospheric lens’ potency, the ordinary noon-day sunlight.

Here we have the Martians at a disadvantage. Due to their circular formation, and the necessity of maintaining it, they cannot move swiftly in a horizontal direction. They have one recourse, and that is to break formation, and dart away.

But now, like deadly hawks, the Earth ships dart down through the smoke screen, dive-bombing as no modem bomber could, and firing streams of atomic shells.

Down go the Martian ships, blasted to bits. But the war has begun. Mars has lost three battleships. Earth has had its greatest city devastated. Where will it all end? War grows constantly more horrible. What will the next attack be? Only the future, and the science of aviation can tell.

(For the purposes of illustration, artist Paul has shown the sunlight beam above as well as below the atmospheric lens. Actually, there would be no beam visible above it, and it would not be visible directly below the lens, but would become brighter as it concentrated, until at the ground, it would be hot enough to melt steel instantly —Ed.)

From NEW YORK INVADED by Henry Gade (1941)

The sun gun or heliobeam is a theoretical orbital weapon, which makes use of a concave mirror mounted on a satellite, to concentrate rays from the sun on to a small area of the Earth's surface, destroying targets or killing through heat.


The Scottish mathematician John Napier proposed such a device. In his book Secrete Inventionis (1596), he published details of a giant mirror to burn enemy ships by focusing the sun's rays on them.

In 1929, the German physicist Hermann Oberth developed plans for a space station from which a 100-metre-wide concave mirror could be used to reflect sunlight onto a concentrated point on the earth.

Later during World War II, a group of German scientists at the German Army Artillery proving grounds at Hillersleben began to expand on Oberth's idea of creating a superweapon that could utilize the sun's energy. This so-called "sun gun" (Sonnengewehr) would be part of a space station 8,200 kilometres (5,100 mi) above Earth. The scientists calculated that a huge reflector, made of metallic sodium and with an area of 9 square kilometres (900 ha; 3.5 sq mi), could produce enough focused heat to make an ocean boil or burn a city. After being questioned by officers of the United States, the Germans claimed that the sun gun could be completed within 50 or 100 years.

Uses in popular culture

In the film Die Another Day, the twentieth installment in the James Bond series of films, the primary antagonist of the film, fictional British billionaire Gustav Graves (in reality the alias of the assumed-to-be-dead North Korean Colonel Tan Sun-Moon), constructs an orbital sun gun code-named "Icarus" for the use of cutting a path through the Korean Demilitarized Zone and allowing North Korean troops to invade South Korea. The device was disabled after its control console is destroyed.

A similar concept is used in the Resident Evil: Revelations video game. In the game, a special satellite code-named Regia Solis is used to provide a city with clean energy but at full capacity it is powerful enough to destroy said city or other targets.

In the TV series Scorpion episode "Sun of a Gun", Walter O'Brien's fictional alter ego and his team are sent alongside their friend Sylvester Dodd's estranged father to an African dictator's country to investigate his discovery of a Nazi World War II sun gun project.

In the Star Wars Legends book Wedge's Gamble, Rogue Squadron commandeers an orbital solar reflector (used for power generation) is used to boil ocean water in an effort to generate a large enough storm to knock out power on the planet (Coruscant) below.

From the Wikipedia entry for SUN GUN


Nazi men of science seriously planned to use a man-made satellite as a weapon for conquest.

In Germany last month U.S. Army technical experts came up with the astonishing fact that German scientists had seriously planned to build a “sun gun,” a big mirror in space which would focus the sun's rays to a scorching point at the earth's surface. The Germans, the Army reported, hoped to use such a mirror to burn an enemy city to ashes or to boil part of an ocean. Many U. S. newspaper readers, remembering the eerie success of V-1 and V-2. swallowed nervously.

Plausible schemes to build a station in space were engineered on paper long before the war. European rocket enthusiasts, including Dr. Hermann Oberth, who may have been the designer of V-2 (no, it wasn't him), had planned to use the space station not as a weapon but as a refueling point for rockets starting off on journeys into space. The station would revolve around the earth like a tiny man-made moon, obeying the gravitational laws of all heavenly bodies. The centrifugal force of its motion would exactly balance the earth's gravitational pull. Men would live inside the station, breathing an artificial atmosphere. The only major obstacle: constructing a rocket powerful enough to reach a point where a space station could be built. If the modern German scientists had been able to make such a rocket, they might have been able to set up their sun gun. Whether the sun gun would have accomplished what they expected, however. is another matter.


The German idea of using the sun as a military weapon is not new. There is an ancient legend that Archimedes designed great burning mirrors which set the Roman fleet afire during the siege of Syracuse, in which Archimedes later died. This legend. and the German plan for huilding a sun gun, may be proved physically impossible by a simple axiom of optics. This is that light cannot he brought to a sharp, pointed focus with lenses or mirrors unless it comes from a sharp, pointed light source. Since the sun appears in the sky as a disk and not as a point, the best any optical system can produce is an image of this disk. At very short focal lengths the image is small and hot but as the focal length is increased the image becomes progressively bigger and cooler. At the distance the Germans proposed to set up their mirror (5,100 miles) the image of the sun cast on the earth would he about 40 miles in diameter and not hot enough to do any damage.

From THE GERMAN SPACE MIRROR Life Magazine July 23, 1945

(ed note: this is a bit of over-the-top space opera for entertainment purposes. No, it doesn't work that way in the real world. But it makes just enough sense for space opera.

E. E. "Doc" Smith's LENSMAN series pioneered the problem of the Lensman Arms Race. The readers were thrilled at the super-colossal gee-whiz super-weapon that was invented in the last book. But the author is stuck with the "how do you top that?" conundrum. Can't disappoint the readers or they will stop buying your books.

In the last novel the valiant members of the Galactic Patrol found that the overwhelming battle fleets of the evil Boskonians were too much to handle. So they mounted huge faster-than-light drives on planets, and used two such planets to crush the enemy planet like a cosmic-scale hammer and anvil. They gave it the picturesque name of "Nutcracker." The novel ends with the hero thinking that it is Miller Time.

At the start of the next novel (taking place about ten seconds after the end of the prior novel), the hero's Mentor slaps him alongside his head and tells him to use his brain. The hero thinks a few seconds, and comes to the horrible realization that the evil Boskone empire will reproduce the mobile planet weapon in a few months. Terra will die under the nutcracker treatment unless our hero can come up with an even more super-colossal weapon.)

Kinnison went. And, wonder of wonders, he took Sir Austin Cardynge with him.

From solar system to solar system, from planet to planet, the mighty Dauntless hurtled at the incomprehensible velocity of her full maximum blast; and every planet so visited was the home world of one of the most cooperative—or, more accurately, one of the least non-cooperative—members of the Conference of Scientists. For days brilliant but more or less unstable minds struggled with new and obdurate problems; struggled heatedly and with friction, as was their wont. Few if any of those mighty intellects would have really enjoyed a quietly studious session, even had such a thing been possible.

Then Kinnison returned his guests to their respective homes and shot his flying warship-laboratory back to Prime Base. And, even before the Dauntless landed, the first few hundreds of a fleet which was soon to be numbered in the millions of meteor-miners' boats began working like beavers to build a new and exactly-designed system of asteroid belts of iron meteors.

And soon, as such things go, new structures began to appear here and there in the void.

Comparatively small, these things were; tiny, in fact, compared to the Patrol's maulers. Unarmed, too; carrying nothing except defensive screen. Each was, apparently, simply a power-house; stuffed skin full of atomic motors, exciters, intakes, and generators of highly peculiar design and pattern. Unnoticed except by gauntly haggard Thorndyke and his experts, who kept dashing from one of the strange craft to another, each took its place in a succession of precisely-determined relationships to the sun.

Between the orbits of Mars and of Jupiter, the new, sharply-defined rings of asteroids moved smoothly. Most of Grand Fleet formed an enormous hollow hemisphere. Throughout all nearby space the surveying speedsters and flitters rushed madly hither and yon. Uselessly, apparently, for not one needle of the vortex- detectors stirred from its zero-pin.

Kinnison was even less easy in his mind. He was not afraid of negaspheres (giant spheres of antimatter), even if Boskonia should have them; but he was afraid of fortified, mobile planets. The super-maulers were big and powerful, of course, but they very definitely were not planets; and the big, new idea was mighty hard to jell. He didn't like to bother Thorndyke by calling him—the master technician had troubles of his own—but the reports that were coming in were none too cheery. The excitation was wrong or the grid action was too unstable or the screen potentials were too high or too low or too something.

Sometimes they got a concentration, but it was just as apt as not to be a spread flood instead of a tight beam. To Kinnison, therefore, the minutes fled like seconds—but every minute that space remained clear was one more precious minute gained.

Then, suddenly, it happened. A needle leaped into significant figures.

Relays clicked, a bright red light flared into being, a gong clanged out its raucous warning. A fractional instant later ten thousand other gongs in ten thousand other ships came brazenly to life as the discovering speedster automatically sent out its number and position; and those other ships—surveyors all—flashed toward that position and dashed frantically about. Theirs the task to determine, in the least number of seconds possible, the approximate location of the center of emergence (of the enemy fleet).

Flotillas, squadrons, sub-fleets flashed smoothly toward their newly-assigned positions. Super-maulers moved ponderously toward theirs. The survey ships, their work done, vanished. They had no business anywhere near what was coming next. Small they were, and defenseless; a speedster's screens were as efficacious as so much vacuum against the forces about to be unleashed. The power houses also moved.

Maintaining rigidly their cryptic mathematical relationships to each other and the sun, they went as a whole into a new one with respect to the circling rings of tightly-packed meteors and the invisible, non-existent mouth of the Boskonian vortex (the opening of the Boskonian stargate where their fleet and nutcracker planets will emerge).

Planets. Seven of them. Armed and powered as only a planet can be armed and powered; with fixed-mount weapons impossible of mounting upon a lesser mobile base, with fixed-mount intakes and generators which only planetary resources could excite or feed. Galactic Civilization's war-vessels fell back. Attacking a full-armed planet was no part of their job. And as they fell back the super-maulers moved ponderously up and went to work. This was their dish; for this they had been designed. Tubes, lances, stillettoes of unthinkable energies raved against their mighty screens; bouncing off, glancing away, dissipating themselves in space-torturing discharges as they hurled themselves upon the nearest ground. In and in the monsters bored, inexorably taking up their positions directly over the ultra-protected domes which, their commanders knew, sheltered the vitally important Bergenholms (FTL drives) and controls. They then loosed forces of their own. Forces of such appalling magnitude as to burn out in a twinkling of an eye projector-shells of a refractoriness to withstand for ten full seconds the maximum output of a first-class battleship's primary batteries!

The resultant beam was of very short duration, but of utterly intolerable poignancy. No material substance could endure it even momentarily. It pierced instantly the hardest, tightest wall-shield known to the scientists of the Patrol. It was the only known thing which could cut or rupture the ultimately stubborn fabric of a Q-type helix.

Hence it is not to be wondered at that as those incredible needles of ravening energy stabbed and stabbed and stabbed again at Boskonian domes every man of the Patrol, even Kimball Kinnison, fully expected those domes to go down.

But those domes held. And those fixed-mount projectors hurled back against the super-maulers forces at the impact of which course after course of fierce-driven defensive screen flamed through the spectrum and went down.

     "Back! Get them back!" Kinnison whispered, white-lipped, and the attacking structures sullenly, stubbornly gave way.
     "Why?" gritted Haynes. "They're all we've got."
     "You forget the new one, chief—give us a chance."
     "What makes you think it'll work?" the old admiral flashed the searing thought. "It probably won't—and if it doesn't…"
     "If it doesn't," the younger man shot back, "we're no worse off than now to use the maulers. But we've got to use the sunbeam now while those planets are together and before they start toward Tellus (Terra)."
     "QX, ("OK")" the admiral assented; and, as soon as the Patrol's maulers were out of the way:
     "Verne?" Kinnison flashed a thought. "We can't crack 'em. Looks like it's up to you—what do you say?"
     "Jury-rigged—don't know whether she'll light a cigarette or not—but here she comes!"

     The sun, shining so brightly, darkened almost to the point of invisibility.
     War-vessels of the enemy disappeared, each puffing out into a tiny but brilliant sparkle of light.
     Then, before the beam could effect the enormous masses of the planets, the engineers lost it. The sun flashed up—dulled—brightened—darkened—wavered. The beam waxed and waned irregularly; the planets began to move away under the urgings of their now thoroughly scared commanders.
     Again, while millions upon millions of tensely straining Patrol officers stared into their plates, haggard Thorndyke and his sweating crews got the sunbeam under control—and, in a heart-stopping wavering fashion, held it together. It flared—sputtered—ballooned out—but very shortly, before they could get out of its way, the planets began to glow. Ice-caps melted, then boiled. Oceans boiled, their surfaces almost exploding into steam. Mountain ranges melted and flowed sluggishly down into valleys. The Boskonian domes of force went down and stayed down.

     "QX, Kim—let be," Haynes ordered. "No use overdoing it. Not bad-looking planets; maybe we can use them for something."
     The sun brightened to its wonted splendor, the planets began visibly to cool—even the Titanic forces then at work had heated those planetary masses only superficially.

The battle was over.

     "What in all the purple hells of Palain did you do, Haynes, and how?" demanded the Z9M9Z's captain.
     "He used the whole damned solar system as a vacuum tube!" Haynes explained, gleefully.
     "Those power stations out there, with all their motors and intake screens, are simply the power leads. The asteroid belts, and maybe some of the planets, are the grids and plates. The sun is—"
     "Hold on, chief!" Kinnison broke in. "That isn't quite it. You see, the directive field set up by the…"
     "Hold on yourself!" Haynes ordered, briskly. "You're too damned scientific, just like Sawbones Lacy. What do Rex and I care about technical details that we can't understand anyway? The net result is what counts—and that was to concentrate upon those planets practically the whole energy output of the sun. Wasn't it?"
     "Well, that's the main idea," Kinnison conceded. "The energy equivalent, roughly, of four million one hundred and fifty thousand tons per second of disintegrating matter."
     "Whew!" the captain whistled. "No wonder it frizzled 'em up."

From SECOND STAGE LENSMAN by E. E. "Doc" Smith (1941)

Relativistic attack

If the invaders are attacking the planet using relativistic weapons, it is more or less game over. There really is no realistic defense, unless the defenders are a Kardashev type II civilization. The problem is light-speed lag. Since the r-bombs are traveling so near the speed of light, they are only a little bit behind the wave of photons announcing their presence. In other words, you only see where they were, not where they are now. From the target's point of view, they would suffer from the optical illusion of the r-bomb apparently moving faster than light. Before you had time to react, the r-bombs would hit with all their devastating effects.

The thing to keep in mind is that all the energy the r-bomb releases has to be put into it in the first place. It takes an astronomical amount of energy to accelerate an object up to 92% lightspeed. If your civilization has managed to anger another civilization who has access to that much energy, you already know you are in deep trouble.

Bombardment in Fiction


      In parks and open spaces, overcrowding problems had forced the erection of hideous, ten-storey tenements. They filled every square and open space like brown, untidy bricks.
     “You think that bad?” Hengist seemed to be reading Duncan’s thoughts, or perhaps his expression. “You didn’t see it as it was, when I was a kid …” He stopped and flicked the spent cigarette into the disposal slot “That was a long time ago. Maybe it was a dream, but you should see the DA.”
     “Devastated areas. The Vrenka got into the system twice. Know what pin-wheels are?”
     “They’re a type of revolving firework, aren’t they ?”
     “Correct. The Vrenka had a weapon like that. Imagine a pin-wheel a mile in diameter spinning and slithering around a bare two feet above ground. It left a trail of grassy slag behind, a glowing pathway a mile on either side—pouf! Heat rushed out at head level, doors crashed in and upper windows blew out. The roofs and upper stories of even the highest buildings suddenly went bam, geysered upwards as if a tornado had started on the ground floor and howled its way out at the top …” He let the sentence trail away and shook himself as if suddenly awakening. “There are worse things than Vrenka spinners, however.”

     “Not cheerful. I have never been there but I’ve seen pictures. Thousands of miles of graveyard is not an inspiring subject for study, and there is an unpleasant story about it, too.”
     “Hengist told me they got through with what he called spinners.”
     “Spinners and other things, mostly heat-generating weapons. The worst part is, although it is not generally known, the Vrenka had never tried for the home planet until one of the suicide vessels got through and clobbered theirs. As you will see, there were no half measures. I don’t know what the solar bombs did to Vrenka but they certainly hit back fast and hard.”
     Duncan looked down and suppressed a gasp. It was far worse than Gaynor had suggested.
     Below, the torn and blackened land was pitted, cratered and twined with unnatural canals. They were still too high for details but here and there were piles of jagged ruins which might once have been cities. White strips, terminating abruptly on the lips of craters, marked the beginnings and ends of what might once have been major highways.
     The vessels were still descending slowly and the two men began to distinguish details.
     Craters, which in the course of years had filled with water had become lakes, and the whole area twisted and twined with unnatural canals.
     Cities appeared to have fallen in on themselves and flown together liquidly like wax models exposed to a hot sun.
     Duncan saw one immense building, bent or melted into a huge arch, its upper storey resting in the glazed ruins on the opposite side of what had once been a main street. It had been golden once but it was now a muddy, discoloured brown. It looked like a huge and dirty half-melted candle into which someone had cut the shapes of windows.
     Across the channel the destruction was even worse. Canals and winding areas of glassy slag crossed and re-crossed like the silvery trails of giant snails. The few buildings which had not melted to shapelessness were jagged and hooked like black fingers reaching from the earth and clutching desperately at nothing.

From THE PRODIGAL SUN by Philip E. High (1964)

There was no sign of the wolverines. Thorvald moved along the pocket southward, and Shann followed him. Once more they faced a dead end. For the crevice, with the sheer descent to the river on the right, the cliff wall at its back, came to an abrupt halt in a drop which caught at Shann's stomach when he ventured to look down.

If some battleship of the interstellar fleet had aimed a force beam across the mountains of Warlock, cutting down to what lay under the first layer of planet-skin, perhaps the resulting wound might have resembled that slash. What had caused such a break between the height on which they stood and the much taller peak beyond, Shann could not guess. But it must have been a cataclysm of spectacular dimensions. There was certainly no descending to the bottom of that cut and reclimbing the rock face on the other side. The fugitives would either have to return to the river with all its ominous warnings of trouble to come, or find some other path across that gap which now provided such an effective barrier to the west.

From STORM OVER WARLOCK by Andre Norton (1960)

Canyon (p Eridani A II) does not quite follow the usual rules for planets.

The planet is not much bigger than Mars. Until a few hundred years ago its atmosphere was just dense enough to support photosynthesis-using plants. The air held oxygen, but was too thin for human or kzinti life. The native life was as primitive and hardy as lichen. Animal had never developed at all.

But there were magnetic monopoles in the cometary halo around Canyon's orange-yellow. sun, and radioactives on the planet itself. The Kzinti Empire swallowed the planet and staffed it with the aid of domes and compressors. They called it Warhead, for its proximity to the unconquered Pierin worlds.

A thousand years later the expanding Kzinti Empire met human space.

The Man-Kzin wars were long over when Louis Wu was born. Men won them all. The kzinti have always had a tendency to attack before they are quite ready. Civilization on Canyon is a legacy of the Third Man-Kzin War, when the human world Wunderland developed a taste for esoteric weapons.

The Wunderland Treatymaker was used only once. It was a gigantic version of what is commonly a mining tool: a disintegrator that fires a beam to suppress the charge on the electron. Where a disintegrator beam falls, solid matter is rendered suddenly and violently positive. It tears itself into a fog of monatomic particles.

Wunderland built, and transported into the Warhead system, an enormous disintegrator firing in parallel with a similar beam to suppress the charge on the proton.

The two beams touched down thirty miles apart on Canyon's surface. Rock and kzinti factories and housing spewed away as dust, and a solid bar of lightning flowed between the two points. The weapon chewed twelve miles deep into the planet, exposing magma throughout a region the size and shape of Baja California on Earth, and running roughly east and west. The kzinti industrial complex vanished. The few domes protected by stasis fields were swallowed by magma, magma that welled higher in the center of the great gash before the rock congealed.

The eventual result was a sea surrounded by sheer cliffs many miles high, surrounding in turn a long, narrow island.

Other human worlds may doubt that the Wunderland Treatymaker ended the war. The Kzinti Patriarchy is not normally terrified by sheer magnitude. Wunderlanders have no such doubts.

Warhead was annexed after the Third Man-Kzin War, and became Canyon. Canyon's native life suffered, of course, from the gigatons of dust that dropped on its surface, and from the loss of water that precipitated within the canyon itself to form the sea. In the canyon there is comfortable air pressure and a thriving pocket-sized civilization.

From RINGWORLD ENGINEERS by Larry Niven (1979 )

(ed note: The Ulant aliens are attacking Terra. The Terran planet of Canaan was bracing for the attack, when the alien fleet contemptuously by-passed the planet as beneath its notice. This injured the pride of the president of Canaan.

The president ordered the entire planet onto a war footing, devoting their entire industrial output to producing arms and supplies for the Terran war fleet. Canaan also became the staging base for Terra's fleet of raider starships, who prey upon the Ulant's logistics chain.

The Ulants are in a bind. If they ignore Canaan, their logistics convoys are decimated and the Terran fleet becomes well supplied. But if they attack Canaan, this will stall the attack on Terra and could end the entire war. So they try to split the difference and only do limited planetary attacks on Canaan.

The protagonist is a soldier turned war correspondant who wants to witness the action first hand. He has the misfortune of being sent to his warship right at the same time the Ulants schedule a major planetary attack.)

      The personnel carrier lurches through the ruins under a wounded sky. The night hangs overhead like a sadist’s boot, stretching out the moment of terror before it falls. It’s an indifferent brute full of violent color and spasms of light. It’s an eternal moment on a long, frightening, infinite trail that loops back upon itself. I swear we’ve been around the track a couple of times before.
     I decide that a planetary siege is like a woman undressing. Both present the most amazing wonders and astonishments the first time. Both are beautiful and deadly. Both baffle and mesmerize me, and leave me wondering, What did I do to deserve this?
     A twist of a lip or a quick chance fragment can shatter the enchantment in one lethal second.
     I look at that sky and wonder at myself. Can I really see beauty in that?

     Tonight’s raids are really showy.
     Moments ago the defensive satellites and enemy ships were stars in barely perceptible motion. You could play guessing games as to which were which. You could pretend you were an old-time sailor trying to get a fix and not being able because your damned stars wouldn’t hold still.
     Now those diamond tips are loci for burning spiders’ silk. The stars were lying to us all along. They were really hot-bottomed arachnids with their legs tucked in, waiting to spin their deadly nets. Gigawatt filaments of home-brew lightning come and go so swiftly that what I really see is afterimages scarred on my rods and cones.
     Balls of light flare suddenly, fade more slowly. There is no way of knowing what they mean. You presume they are missiles being intercepted because neither side often penetrates the other’s automated defenses. Occasional shooting stars claw the stratosphere as fragments of missile or satellite die a second death. Everything consumed in this holocaust will be replaced the moment the shooters disappear.
     I hear the Commander’s chuckle and look his way. He’s a dim, golden-haired silhouette against the moonlight. He’s watching me. “They’re only playing tonight,” he says. “Drills, that’s all. Just training drills.” His laugh explodes like a thunderous fart. (demonstrating his low opinion of the morons who told him the Ulants were just going do small training drills, instead of a major offensive push)
     There is a big explosion up top. For an instant the ruins become an ink-line drawing of the bottommost floor of hell. Forests of broken brick pillars and rusty iron that present little resistance to the shock waves of the attackers’ weapons. Every single one will tumble someday. Some just demand more attention.
     “We looked Turbeyville over on our way here,” I say, and Yanevich nods. “I saw enough.”
     The Fleet’s big on-planet headquarters is buried beneath Turbeyville. It gets the best of the more serious drops.
     The Commander and I had looked around while the dust was settling from the latest. The moons had been in conjunction nadir the previous night. That weakens the defense matrix, so the boys upstairs jumped through the hole with a heavy boomer drop. They replowed several square kilometers of often-turned rubble. They do it for the same reason a farmer plows a fallow field. It keeps the weeds from getting too tall.
     The Commander says it was a tease strike. Just something to keep the edge on their boys and let us know our upstairs neighbors may come to stay someday.
     The abandoned surface city lay immobilized in winter’s tight grasp when we arrived. The iron skeletons of buildings creaked in bitter winds. All those mountains of broken brick lay beneath a rime of ice. In the moonlight they looked as though herds of migrating slugs had left their silvery trails upon them.
     A handful of civilians prowled the wastes, hunting dreams of yesterday. The Old Man says the same ones come out after every raid, hoping something from the past will have worked to the surface. Poor Flying Dutchmen, trying to recapture annihilated dreams.
     A billion dreams have already perished. This conflict, this furnace of doom, will consume a billion more. Maybe it feeds on them.
     The Pits are another popular target. The boys upstairs can’t resist. They’re the taproot of Climber Command’s logistics tree, the point where the strength of Canaan coalesces for transfer to the Fleet. The Pits spew men, stores, and materiel like a full-time geyser.
     All they ever reclaim is leave-bound Climber people (crews of raider starships) wearing the faces of concentration camp escapees.
     Now I can feel the earth tremors generated by departing lifters. They leave at ten-second intervals, ‘round Canaan’s! twenty-two-hour and fifty-seven-minute clock. They come in varying sizes. Even the little ones are bigger than barns. They are simply gift boxes packed with goodies for the Fleet.
     The Commander wants me. He’s leaning toward me, wearing his mocking grin. “Three klicks to go. Think we’ll make it?”
     I ask if he’s giving odds.
     His blue eyes roll skyward. His colorless lips form a thin smile. The gentlemen of the other firm are playing with bigger firecrackers now. The flashes splatter his face, tattooing it with light and shadow.
     Something is going on upstairs. It makes me nervous. The aerial show is picking up. This isn’t any drill. The interceptions are taking place in the troposphere now. Choirs of ground-based weapons are testing their voices. They sing in dull crackles and booms. The carrier’s roar and rumble only partially drown them.
     Halos of fire brand the night.
     A violin-string tautness edges Yanevich’s words as he observes, “Drop coming down.”
     I want to see, too. “How long before the dropships arrive?”
     I’ve seen the tapes. My seat harness feels like a straitjacket. Caught on the ground, in the open. The enemy coming. A Navy man’s nightmare.
     They don’t bother with my question. Only the enemy knows what he’s doing. That adds to my unease.
     Marines, Planetary Defense soldiers, Guardsmen, they can handle the exposure. They’re trained for it. They know what to do when a raider bottoms her drop run. I don’t. We don’t. Navy people need windowless walls, control panels, display tanks, in order to face their perils calmly.
     Even Westhause has run out of things to say. We watch the sky and wait for that first hint of ablation glow.
     Turbeyville boasted a downed dropship. It was a hundred meters of Stygian lifting body half-buried in rubble. There is a stop frame I’ll carry a long time. A tableau. Steam escaping the cracked hull, colored by a vermilion dawn. Very picturesque.
     That boat was pushing mach 2 when her crew lost her, yet she went in virtually intact. The real damage happened inside.
     I decided to shoot some interiors. One look changed my mind. The shields and inertial fields that preserved the hull juiced its occupants. Couldn’t tell they had been guys pretty much like us, only a little taller and blue, with mothlike antennae instead of ears and noses. Ulantonids, from Ulant, their name for their homeworld. “Those chaps got an early out,” the Commander told me. He sounded as if he envied them.
     “Looks like we’ll get in ahead of them,” Yanevich says.
     I check the sky. I can’t fathom the omens he’s reading.
     The surface batteries stop clearing their throats and begin singing in earnest. The Commander gives Yanevich a derisive glance. “Seems to be sh*t flying everywhere, First Officer.”
     “Make a liar out of me,” the Lieutenant growls. He flings a ferocious scowl at the sky.
     Eye-searing graser flashes illuminate the rusting bones of once-mighty buildings.
     The first dropship whips in along the carrier’s backtrail, taking us by surprise. Her sonic wake seizes the vehicle, gives it one tremendous shake, and deafens me momentarily. Somehow the others get their hands to their ears in time. The dropper becomes a glowing deltoid moth depositing her eggs in the sea.
     “There’s some new lifters that’ll need to be built,” Westhause says. “Let’s hope what we lost were Citron Fours.”
     My harness is suddenly a trap. Panic hits me. How can I get away if I’m strapped down?
     The Commander touches me gently. His touch has a surprisingly calming effect. “Almost there. A few hundred meters.”
     The carrier stops almost immediately. “You’re a prophet.” It’s a strain, trying to sound settled. That damned open sky mocks our human vulnerability, throwing down great bolts of laughter at our puniness.
     A second dropper cracks overhead and leaves her greetings. A lucky ground weapon has bitten a neat round hole from her flank. She trails smoke and glowing fragments. She wobbles. I missed covering my ears again. Yanevich and Bradley help me out of the carrier.
     Bradley says, “Bad shields on that one.” He sounds about two kilometers away. Yanevich nods.
     “Wonder if they’ll ever get her back up.” The First Watch! Officer commiserates with fellow professionals.

     Half a hundred production and packaging lines chug along below us. Their operators work on a dozen tiers of steel grate. The cavern is one vast, insanely huge jungle gym, or perhaps the nest of a species of technological ant. The rattle, clatter, and clang are as dense as the ringing round the anvils of hell. Maybe it was in a place like this that the dwarfs of Norse mythology hammered out their magical weapons and armor.
     Jury-rigged from salvaged machinery, ages obsolete, the plant is the least sophisticated one I’ve ever seen. Canaan became a fortress world by circumstance, not design. It suffered from a malady known as strategic location. It still hasn’t gotten the hang of the stronghold business.
     “They make small metal and plastic parts here,” Westhause explains. “Machinedparts, extrusion moldings, castings. Some microchip assemblies. Stuff that can’t be manufactured on TerVeen.”
     The boomer drop was rough for me. I could see and hear Death on my backtrail. It was personal. Those droppers were after me.
     Navy people seldom see the whites of enemy eyes. Line ships are toe to toe at 100,000 klicks. These men are extending the psychology of distancing.
     The Commander says the TerVeen go was a holiday junket. Like taking a ferry across a river. The gentlemen of the other firm were busy covering their dropships.
     TerVeen isn’t a genuine moon. It’s a captive asteroid that has been pushed into a more circular orbit. It’s 283 kilometers long and an average 100 in diameter. Its shape is roughly that of a fat sausage. It isn’t that huge as asteroids go.
     The support system wakened us when the lifter entered TerVeen’s defensive umbrella. There’re no viewscreens in our compartment, but I’ve seen tapes. The lifter will enter one of the access ports which give the little moon’s surface a Swiss cheese look. The planetoid serves not only as a Climber fleet base, but also as a factory and mine. The human worms inside are devouring its substance. One great big space apple, infested at the heart.
     The process began before the war. Someone had the bright idea of hollowing TerVeen and using it as an industrial habitat. When completed, it was supposed to cruise the Canaan system preying on other asteroids. One more dream down the tubes.
     I ask one of my questions. “Why doesn’t the other firm bring in a Main Battle Fleet? It shouldn’t be that hard to scrub Canaan and a couple of moons.”
     “They’re stretched too thin trying to blitz the Inner Worlds. The guys bothering us are trainees. They hang out here a couple of months, getting blooded, before they take on the big time. When we get out there it’ll be a different story. The reps on those routes are pros. There’s one Squadron Leader they call the Executioner. He’s the worst news since the Black Death.”
     I’m getting tired of Westhause’s voice. It takes on a pedantic note when he knows you’re listening.
     “Suppose they committed that MBF? It would have to come from inside. That would stall their offensive. If we carved it up, they’d lose the initiative. And we might cut them good.
     “Climbers get mean when they’re cornered.” A hint of pride has crept in here.
     “Meaning they can’t afford to take time out to knock us off, but they can’t afford to leave us alone, either?”
     “Yeah. Containment. That’s the name of their game.”
     “The holonets say we’re hurting them.”
     “Damned right we are. We’re the only reason the Inner Worlds are holding out. They’re going to do something…”
     Westhause continues to explain. “What they did was drill the tunnels parallel to TerVeen’s long axis. They were cutting the third one when the war started. They were supposed to mine outward from the middle when that was finished. The living quarters were tapped in back then, too. For the miners. It was all big news when I was a kid. Eventually they would’ve mined the thing hollow and put some spin on for gravity. They didn’t make it. This tunnel became a wetdock. A Climber returns from patrol, they bring her inside for inspections and repairs. They build the new ones in the other tunnel. Some regular ships too. It has a bigger diameter.”
     In Navy parlance a wetdock is any place where a ship can be taken out of vacuum and surrounded by atmosphere so repair people don’t have to work in suits. A wetdock allows faster, more efficient, and more reliable repairwork.
     “Uhm.” I’m more interested in looking than listening.
     “Takes a month to run a Climber through the inspections and preventive maintenance. These guys do a right job.”
     I try to watch the work going on out in the big tunnel. So many ships! Most of them are not Climbers at all. Half the defense force seems to be in for repairs. A hundred workers on tethers float around every vessel. No lie-in-the-comer refugees up here. Everybody works. And the Pits keep firing away, sending up the supplies.
     Sparks fly in mayfly swarms as people cut and weld and rivet. Machines pound out a thunderous industrial symphony. Several vessels are so far dismantled that they scarcely resemble ships. One has its belly laid open and half its skin gone. A carcass about ready for the retail butcher. What sort of creature feeds on roasts off the flanks of attack destroyers?
     Gnatlike clouds of little gas-jet tugs nudge machinery and hull sections here and there. How the devil do they keep track of what they’re doing? Why don’t they get mixed up and start shoving destroyer parts into Climbers?
     A Climber appears. It looks clean. Very little micrometeorite scoring, even. “Doesn’t look like there’s anything wrong with that one.”
     “The critical heat-sensitive stuff gets replaced after every patrol. The laser weaponry, too. Takes too long to break it down and scan each part. Somebody back down the tube will get ours. We’ll get something that belonged to somebody who’s on patrol already.”
     A whole, combat-ready Climber looks like an antique spoked automobile wheel and tire with a ten-liter cylindrical canister where the hub belongs. Its exterior is fletched with antennae, humps, bumps, tubes, turrets, and one huge globe riding high on a tall, leaning vane reminiscent of the vertical stabilizer on supersonic atmosphere craft. Every surface is anodized a Stygian black.
     There are twelve Climbers in the squadron. They cling to a larger vessel like a bunch of ticks. The larger vessel looks like the frame and plumbing of a skyscraper after the walls and floors are removed. This is the mother, the command and control ship. She’ll carry her chicks into the patrol sector and scatter them, then pick up any patrolling vessels that have expended their missiles and need rides home.
     Though a Climber can space for half a year and few patrols last longer than a month, Command wants no range sacrificed getting to the zone, nor any stores expended. Stores are a Climber’s biggest headache, her Achilles’ heel. By their nature the vessels pack a lot of hardware into tightly limited space. There’s little room left for crew or consumables.
     Our mother ship is one of several floating in a vast bay. The others have only a few Climbers suckered on. Each is kept stationary by a spiderweb of common rope. The ropes are the only access to the vessel. “They don’t waste much on fancy hardware.” Tractors and pressors would stabilize a vessel in wetdock anywhere else in the Fleet. Vast mechanical brows would provide access.
     “Don’t have the resources,” Westhause says. “‘Task-effective technological focus,’” he says, and I can hear the quotes. “They’d put oars on these damned hulks if they could figure out how to make them work. Make the scows more fuel-effective.”
     A mother-locked Climber can be entered only through a hatch in the “top” of its central cylinder. The hatch isn’t an airlock. It’ll remain sealed through the vessel’s stay in vacuum. The ship’s only true airlock is at its bottom. That’s connected to the mother now. Surrounding it is a sucker ring through which the Climber draws its sustenance till it’s released for patrol. Power and water. And oxygen. Through the hatch itself will come our meals, though not prepared. Through that hatch, too, will come our orders, moments before we’re weaned.
     Westhause is explaining the airlock system. “The only reverse flow consists of wastes,” he concludes.
     “And you give that any significance you want,” the Commander mutters. “Sh*t for sh*t, I say. Down the hatch, men.”

From PASSAGE AT ARMS by Glen Cook (1985)

Londo Mollari: Refa, any force attempting to invade Narn would be up to its neck in blood—its own!

Lord Refa: We have no intention of invading Narn. Flattening it, yes—but invading it? We will be using mass drivers. By the time we are done their cities will be in ruins, we can move in at our leisure!

Londo Mollari: Mass drivers? They have been outlawed by every civilized planet!

Lord Refa: These are uncivilized times.

Londo Mollari: We have treaties!

Lord Refa: Ink on a page!

Capt. John Sheridan: Any news?

Cmdr. Susan Ivanova: Just rumors. They say the Centauri are using mass drivers. I can't believe they'd resort to planetary bombardment!

Capt. John Sheridan: Right now I'd believe just about anything.

From Babylon 5: The Long, Twilight Struggle by J. Michael Straczynski (1995)

The Moon Is A Harsh Mistress

In the novel, the lunar colony is fed up with the yoke of Terran oppression and stages their very own war of independence. Among their assets is a large external mass driver (called a "catapult") ordinarily used to send shipments of grain back to Terra. The colonists weaponize it, firing cannisters of steel-belted solid rock as orbital bombardment weapons.

(ed note: "Mike" is the supercomputer that controls and maneuvers the cannisters from the catapult. The text is the internal dialog of the main character, who is a native Russian speaker. This explains his broken English. "F.N." is the Federated Nations, the world government and "owner" of the lunar colony and all the inhabitants. TANSTAAFL is an acronym for There Ain't No Such Thing As A Free Lunch)

     LuNoHoCo was an engineering and exploitation firm, engaged in many ventures, mostly legitimate. But prime purpose was to build a second catapult, secretly.

(ed note: colonists know that once they start lobbing cannisters as weapons, their catapult will become the priority military target)

     Operation could not be secret. You can’t buy or build a hydrogen-fusion power plant for such and not have it noticed. (Sunpower was rejected for obvious reasons.) Parts were ordered from Pittsburgh, standard UnivCalif equipment, and we happily paid their royalties to get top quality. Can’t build a stator for a kilometers-long induction field without having it noticed, either. But most important you cannot do major construction hiring many people and not have it show. Sure, catapults are mostly vacuum; stator rings aren’t even close together at ejection end. But Authority’s 3-g catapult was almost one hundred kilometers long. It was not only an astrogation landmark, on every Luna-jump chart, but was so big it could be photographed or seen by eye from Terra with not-large telescope. It showed up beautifully on a radar screen.
     We were building a shorter catapult, a 10-g job, but even that was thirty kilometers long, too big to hide.

(ed note: the shorter the catapult, the higher the gravities of acceleration required)

     So we hid it by Purloined Letter method.

(ed note: workers know catapult is at the end of the subway line, but have no idea where exactly that is.)

     What we needed was something else. Needed steel at new catapult and plenty—Prof asked, if really necessary to put steel around rock missiles; I had to point out that an induction field won’t grab bare rock. We needed to relocate Mike’s ballistic radars at old site and install doppler radar at new site—both jobs because we could expect attacks from space at old site.

     “A maximum of instructive shrecklichkeit with minimum loss of life. None, if possible”—was how Prof summed up doctrine for Operation Hard Rock and was way Mike and I carried it out. Idea was to hit earthworms so hard would convince them —while hitting so gently as not to hurt. Sounds impossible, but wait.
     Would necessarily be a delay while rocks fell from Luna to Terra; could be as little as around ten hours to as long as we dared to make it. Departure speed from a catapult is highly critical and a variation on order of one percent could double or halve trajectory time, Luna to Terra. This Mike could do with extreme accuracy—was equally at home with a slow ball, many sorts of curves, or burn it right over plate—and I wish he had pitched for Yankees. But no matter how he threw them, final velocity at Terra would be close to Terra’s escape speed, near enough eleven kilometers per second as to make no difference. That terrible speed results from gravity well shaped by Terra’s mass, eighty times that of Luna, and made no real difference whether Mike pushed a missile gently over well curb or flipped it briskly. Was not muscle that counted but great depth of that (gravity) well.
     So Mike could program rock-throwing to suit time needed for propaganda. He and Prof had settled on three days plus not more than one apparent rotation of Terra—24hrs-50min-28.32sec—to allow our first target to reach initial point of program. You see, while Mike was capable of hooking a missile around Terra and hitting a target on its far side, he could be much more accurate if he could see his target, follow it down by radar during last minutes and nudge it a little for pinpoint accuracy.
     We needed this extreme accuracy to achieve maximum frightfulness with minimum-to-zero killing. Call our shots, tell them exactly where they would be hit and at what second—and give them three days to get off that spot.
     North America had struck me as horribly crowded, but her billion people are clumped—is still wasteland, mountain and desert. We laid down a grid on North America to show how precisely we could hit—Mike felt that fifty meters would be a large error. We had examined maps and Mike had checked by radar all even intersections, say 105° W by 50° N—if no town there, might wind up on target grid … especially if a town was close enough to provide spectators to be shocked and frightened.
     We warned that our bombs would be as destructive as H-bombs but emphasized that there would be no radioactive fallout, no killing radiation—just a terrible explosion, shock wave in air, ground wave of concussion. We warned that these might knock down buildings far outside of explosion and then left it to their judgments how far to run. If they clogged their roads, fleeing from panic rather than real danger—well, that was fine, just fine!
     But we emphasized that nobody would get hurt who heeded our warnings, that every target first time around would be uninhabited—we even offered to skip any target if a nation would inform us that our data were out-of-date. (Empty offer; Mike’s radar vision was a cosmic 20/20.)
     But by not saying what would happen second time around, we hinted that our patience could be exhausted.
     In North America, grid was parallels 35, 40, 45, 50 degrees north crossed by meridians 110, 115, 120 west, twelve targets. For each we added a folksy message to natives, such as:
     “Target 115 west by 35 north—impact will be displaced forty-five kilometers northwest to exact top of New York Peak. Citizens of Goffs, Cima, Kelso, and Nipton please note.
     “Target 100 west by 40 north is north 30° west of Norton, Kansas, at twenty kilometers or thirteen English miles. Residents of Norton, Kansas, and of Beaver City and Wilsonville, Nebraska, are cautioned. Stay away from glass windows. It is best to wait indoors at least thirty minutes after impact because of possibility of long, high splashes of rock. Flash should not be looked at with bare eyes. Impact will be exactly 0300 your local zone time Friday 16 October, or 0900 Greenwich time—good luck!

     But our attitude was conciliatory—“Look, people of Terra, we don’t want to kill you. In this necessary retaliation we are making every effort to avoid killing you… but if you can’t or won’t get your governments to leave us in peace, then we shall be forced to kill you. We’re up here, you’re down there; you can’t stop us. So please be sensible!”
     We explained over and over how easy it was for us to hit them, how hard for them to reach us. Nor was this exaggeration. It’s barely possible to launch missiles from Terra to Luna; it’s easier to launch from Earth parking orbit—but very expensive. Their practical way to bomb us was from ships.

     Came Friday with no answer from F.N. News up from Earthside seemed equal parts unwillingness to believe we had destroyed seven ships and two regiments (F.N. had not even confirmed that a battle had taken place) and complete disbelief that we could bomb Terra, or could matter if we did—they still called it “throwing rice.” More time was given to World Series.

     My worries had to do with Mike. Sure, Mike was used to having many loads in trajectory at once—but had never had to astrogate more than one at a time. Now he had hundreds and had promised to deliver twenty-nine of them simultaneously to the exact second at twenty-nine pinpointed targets.
     More than that— For many targets he had backup missiles, to smear that target a second time, a third, or even a sixth, from a few minutes up to three hours after first strike.
     Four great Peace Powers, and some smaller ones, had antimissile defenses; those of North America were supposed to be best. But was subject where even F.N. might not know. All attack weapons were held by Peace Forces but defense weapons were each nation’s own pidgin and could be secret. Guesses ranged from India, believed to have no missile interceptors, to North America, believed to be able to do a good job. She had done fairly well in stopping intercontinental H-missiles in Wet Firecracker War past century.
     Probably most of our rocks to North America would reach target simply because aimed where was nothing to protect. But they couldn’t afford to ignore missile for Long Island Sound, or rock for 87° W x 42° 30’ N—Lake Michigan, center of triangle formed by Chicago, Grand Rapids, Milwaukee. But that heavy gravity makes interception a tough job and very costly; they would try to stop us only where worth it.
     But we couldn’t afford to let them stop us. So some rocks were backed up with more rocks. What H-tipped interceptors would do to them even Mike did not know—not enough data. Mike assumed that interceptors would be triggered by radar —but at what distance? Sure, close enough and a steelcased rock is incandescent gas a microsecond later. But is world of difference between a multi-tonne rock and touchy circuitry of an H-missile; what would “kill” latter would simply shove one of our brutes violently aside, cause to miss.
     We needed to prove to them that we could go on throwing cheap rocks long after they ran out of expensive (milliondollar? hundred-thousand-dollar?) H-tipped interceptor rockets. If not proved first time, then next time Terra turned North America toward us, we would go after targets we had been unable to hit first time—backup rocks for second pass, and for third, were already in space, to be nudged where needed.
     If three bombings on three rotations of Terra did not do it, we might still be throwing rocks in ‘77—till they ran out of interceptors… or till they destroyed us (far more likely).
     For a century North American Space Defense Command had been buried in a mountain south of Colorado Springs, Colorado, a city of no other importance. During Wet Firecracker War the Cheyenne Mountain took a direct hit; space defense command post survived—but not sundry deer, trees, most of city and some of top of mountain. What we were about to do should not kill anybody unless they stayed outside on that mountain despite three days’ steady warnings. But North American Space Defense Command was to receive full Lunar treatment: twelve rock missiles on first pass, then all we could spare on second rotation, and on third—and so on, until we ran out of steel casings, or were put out of action… or North American Directorate hollered quits.
     This was one target where we would not be satisfied to get just one missile to target. We meant to smash that mountain and keep on smashing. To hurt their morale. To let them know we were still around. Disrupt their communications and bash in ommand post if pounding could do it. Or at least give them splitting headaches and no rest. If we could prove to all Terra that we could drive home a sustained attack on strongest Gibraltar of their space defense, it would save having to prove it by smashing Manhattan or San Francisco.
     Which we would not do even if losing. Why? Hard sense. If we used our last strength to destroy a major city, they would not punish us; they would destroy us. As Prof put it, “If possible, leave room for your enemy to become your friend.”
     But any military target is fair game.

     Got into shade of shed and peeked around edge at Terra.
     She was hanging as usual halfway up western sky, in crescent big and gaudy, three-plus days past new. Sun had dropped toward western horizon but its glare kept me from seeing Terra clearly. Chin visor wasn’t enough so moved back behind shed and away from it till could see Terra over shed while still shielded from Sun—was better. Sunrise chopped through bulge of Africa so dazzle point was on land, not too bad—but south pole cap was so blinding white could not see North America too well, lighted only by moonlight.
     Twisted neck and got helmet binoculars on it—good ones, Zeiss 7 x 50s that had once belonged to Warden.
     North America spread like a ghostly map before me. Was unusually free of cloud; could see cities, glowing spots with no edges. 0837—
     At 0850 Mike gave me a voice countdown—didn’t need his attention; he could have programmed it full automatic any time earlier.
     0851—0852—0853… . one minute—59—58—57 … . half minute—29–28—27 … . ten seconds—nine—eight— seven— six—five—four—three—two—one—
     And suddenly that grid burst out in diamond pinpoints!

     Prof looked puzzled. “I am confused by that, too. This dispatch so alleged. But the thing that puzzled me is that we could actually see, by video, what certainly seemed to be atomic explosions.”
     “Oh.” I turned to Wright. “Did your brainy friends tell you what happens when you release a few billion calories in a split second all at one spot? What temperature? How much radiance?”
     “Then you admit that you did use atomic weapons!”
     “Oh, Bog!” Head was aching. “Said nothing of sort. Hit anything hard enough, strike sparks. Elementary physics, known to everybody but intelligentsia. We just struck damnedest big sparks ever made by human agency, is all. Big flash. Heat, light, ultraviolet. Might even produce X-rays, couldn’t say. Gamma radiation I strongly doubt. Alpha and beta, impossible. Was sudden release of mechanical energy. But nuclear? Nonsense!”

From THE MOON IS A HARSH MISTRESS by Robert Heinlein (1965)

Destructive Potential of Lunar Rocks

If the catapults were able to fire stuff at velocities comparable to Earth's escape velocity, the lag time issues would favour Terrestrial catapults (mounted on moving vehicles, these might be called 'MBT cannons'). This means the energy content of the incoming rocks is something like 6x10^7 J/kg. For comparison, fission peace enhancement devices are good for about 9x10^12 J/kg, ims, and fusion PED for 8x10^14 J/kg. It still compares well to TNT's 4.6x10^6 J/kg but note we are not talking the five to seven orders of magnitude between atomic and chemical but one order of magnitude.

If some arcane method could be found to focus the energy in a chemical explosive into a smaller massed projectile, it seems possible terrestrial chemically driven projectiles could compete with Lunar> ones in terms of EK/kg or alternatively one might use 15x as many shots.


Crater diameter scales roughly according to the cube root of the delta energy. Barringer is ~1 km across and was formed by a 15 MT (~6x10^16J) event. Diamter/depth ~6 is not a bad general rule.

Say our lunar impactor is a 2 kt event. The crater would be 1 km x [8.4x10^12 J/6x10^16 J]^1/3 or ~50 m diamter x 8 m deep.

Cheyenne is destroyed in TMISHM by the impact of many rocks from the Moon. Call it a cone of r = 1000 m and h = 1000 m, for a Volume of about 10^9 m^3. Given the crater volumes (rouhly) 5300 m^3 it would take very roughly 200,000 shots or at least 67+ days if they can fire one shot every 30 seconds or so.

Note: a 2 kt device in this case is also a 140 tonne ingot, because you are getting atomic weapon yields out of something with an energy density only an order of magnitude better than chemical. An iron package would be about 18 m^3 (a 3.2 m diameter sphere). An osmium one would be but 6.2 m^3 (a 2.3 m diameter sphere).

NASA tracks orbital debris as small as 10 cm, and current radar technology (which is to say, of an era earlier than the Lunar Catapult) can track items as small as 3 mm, albeit below 600 km altitude at present.

Incoming ingots are therefore likely to be noticed fairly early.

Wave formation:

Stolen without attribution from _Hazards Due to Comets & Asteroids_

Wave height, impact in shallow water:

h = 1450 m [d/r] [y/gigatons]^1/4

h = wave height
d = water depth
r = range to impact
y = yield

ditto, impact in deep water:

h = 6.5 m [y/gigaton]^0.54 [1000km/r]

Wave run in:

Xmax ~ 1.0 km [h/10 meters]^4/3

And this really is a very rough general rule. Consider what happens to a 10 meter wave hitting the cliffs of Dover vs Bangladesh (with 17 million people roughly 1 meter above high tide, IIRC).

RAH is unfortunately specific about the UK offshore impacts, which is what led to the conclusion that the wave height at Margate was 7 cm. Even more unfortunately, _The Effects of Nuclear Weapons_ would led one estimate this and it was available when TMIAHM was written.

Small ingots make tiny waves. Large ingots are, well, large and attract early detection and countermeasures.


One of the attractive things about Lunar catapults is that they led you leverage your input: most of the Ek comes from falling 380,000 km rather than directly from the capapult [After all, if the catapult could fire things at 11/km, you could just put it on the Earth and lob objects at semiorbital velocities around the planet]. You do have to get the objects off the Moon, though.

Say this is an investment of 2.5 km/s. Each ingot masses 140,000 kg, so the Ek is 4x10^11 Joules. At ten gees, that's 25 seconds, or a power output of 16 gigawatts. This catapult needs Pickering sized nuclear reactor or its equivelent to power it.

This raises more stealth issues. If 90% of the power goes into Ek and 10% into heat, this is generating about 1.8 GW of heat for half a minute. This is a serious problem because the heat flare lets the targets know a shot has been fired. It also lets them know where the radiators are, inviting attacks on them.

This is another reason why stealthy attacks are hard with the catapult. The reason I mention stealth is because of

Time to Target:

A low energy orbit to Earth takes 3 - 5 days (Or even longer, for other solutions). A Lunar Bombard begins by announcing each launch with a flare of heat, then a large trackable object slowly orbits to Earth, where it experiences a lithobraking phase at least 72 hours later.

By comparison, a 1 km/s projectile fired from 100 km away arrives in about 2 minutes (Hastily checks to make sure 100 km is within the range of a 1 km/s ballistic object).

A Standard Wheelchair Bound Grandmother [SWBG] is assumed to be able to procede over paved road at 2 km/hr and 100 m/hr on broken ground. In 72 hours, assuming 8 hours of rest in every 24, a SWBG can procede 96 km on paved road and 4.8 km in rough terrain. A SWBG could therefore evade most of the effects of a 2 kt groundburst.

By comparison, a SWBG could only move 70 meters on paved ground (the best case scenario), if the 2 kt event package was sent at 1 km/s from a source 100 km away. 70 m is within the fireball of a 2 kt event. Most SWBGs will not survive being in a fireball.

Lunar bombards are therefore only good against static targets. And we already have weapons just as effective on static targets that don't take half a week to arrive. Therefore Lunar bombards are not competitive for targets on Earth with weapons we already have.

Burnt Off

If the interstellar conflict in question is all about extermination, with none of that realpolitik nonsense, there is no point in a limited orbital bombardment. Assuming you do not want the planet as a possible colony site, then you might as well nuke the place until it is a black glassy sphere that will glow radioactive blue for the next million years or so. The result will be a cemetery planet object lesson for future alien civilizations to come that the inhabitants really pissed you off (or were some hideous species that was far too dangerous to live).

Have your interstellar bomber dump a hellburner, a planet-wrecker nuclear bomb, a planet-sterilizing torch warhead, a planet-cracker antimatter warhead, or a planet-buster neutronium-antimatter warhead. Or take a bit more time to simply carpet-bomb the planet with old-school nuclear warheads.


SLAG. To effectively destroy a PLANET, rendering it totally non-HABITABLE by melting the surface into slag. This need not require a particularly high TECHLEVEL; bumping a handy asteroid into a collision orbit will do it nicely. The ease with which Planets can be Slagged introduces a fundamental problem in WARFARE, equivalent to the nuclear balance of terror that prevailed on Earth during the second half of the 20th century CE.

     If Warfare is to be an effective means of settling political differences, some way has to be found to keep everyone from just Slagging each other, and most of the KNOWN GALAXY, into oblivion. Judging from historical experience, the natural solution is to refrain from large-scale regular Warfare, resorting instead to terrorism or fomenting guerilla wars on third-galaxy Planets. Neither of these solutions seems to be widespread, though. They lack the glamour of real stand-up Warfare, and at least for Americans the idea of guerilla wars still evokes the dismal Spectre of Vietnam.

     Universal peace is no solution — that would be as boring as vegetarianism, and everyone would wander off to read fantasy trilogies or Tom Clancy knockoffs instead. So instead an unwritten agreement seems to prevail, in all eras and throughout the Known Galaxy. Warfare can and will be fought a l'outrance, with frequent stand-up clashes of battlefleets in Space and armored divisions on Planets, but everyone will almost always refrain from Slagging Planets.

     Violators, one must presume, get Slagged.


For myself and my setting, I concluded that at least some aspects of the “kill it with nuclear fire” school are going to be more or less inescapable because of, as you point out, how good the planetary defenders have it.

What the Ley Accordsthe Eldraeverse equivalent of the Geneva Convention, essentially – actually says is that you can’t use planetary bombardment indiscriminately on civilian populations or to make terror strikes, and once you’ve disabled the orbital defenses and “own the high orbitals”, you’re supposed to ask for their surrender before you start firing on the legitimate military targets…

…because once you’ve started dropping heavy enough hellflowers (air-burst antimatter sterilization/EMP weapons), stoneburners (sub-ground-burst anti-bunker burrowing antimatter shaped-charges), and plain old k-rods (Rods From God) to take out deep-running submarines, crust-embedded fortresses, giant planetary lasers, etc., etc., there’s no way not to do major damage to the planet even if you’re not trying to, or indeed if you’re trying not to. If you’re lucky, you’ll get away with a few dozen simultaneous earthquakes/tsunamis/wildfires/hurricanes/massive radiation events/etc. worth of damage. If you’re unlucky, you throw enough debris into the air to give you a particle winter and a major extinction event. And either way, depending on how careful the planetary government is to keep its military facilities in the middle of nowhere, you’ve got megadeaths to gigadeaths.

The polities that are both (a) established galactic citizens, and (b) halfway civilized, all understand this, and that you’re supposed to surrender the planet when you lose the orbital defenses, because while you might not be able to take it back, you definitely can’t un-wreck it.

(Even if you intend to fight a guerilla war groundside afterwards and are willing to absorb the damage from that, you may still find it worthwhile to surrender any formal planetary defenses you invested in. At least that way they’re only going to be dropping tactical k-rods on you…

…but there’s no upside to engaging in a pissing contest with starship-class weapons and their planet-mounted equivalents when the planet is going to take all the collateral damage, and the fleet in orbit doesn’t have to worry about that.)

Thus, Imperial admirals hate having to fight galactic newbies (who might be under the impression that you can fight and win an orbit/ground battle without taking horrific collateral damage), or worse, the kind of fanatics who don’t mind taking their population and ecology along with them when they go. (Although, in practice, there’s usually someone in the latter’s command structure willing to introduce their leader to a bullet rather than let him initiate Ragnarok.) Even Caliéne “the Worldburner” Sargas-ith-Sargas, the IN’s mostly-tame sociopath, thinks it’s a little messy and inelegant.

From SLAG THEM! by Alistair Young (2015)

(ed note: the Grand Alliance of Terrans, Orions, Gorm and Ophiuchi have their backs against the wall. They are sore beset by the Arachnid Omnivoracity. These are aliens who resemble huge spiders, are too alien to communicate with, and who consider all other intelligent races to be food sources. They are fond of eating alive human beings, especially children. As more and more Alliance planets are captured and eaten by the bugs, the Terrans implement General Directive 18. Genocide has been ordered on any planet in the Arachnid Omnivoracity.)

      "It worked, Admiral! We're in, and there's no indication that they've detected our emergence!"

     "Thank you, Commander," Prescott acknowledged quietly. He didn't really want to deflate the spook's enthusiasm, but at times like this the most useful thing an admiral could do was project an air of imperturbable calm and confidence.

     And, after all, it wasn't so surprising that Sixth Fleet had succeeded in entering the Bug system undetected. This was a closed warp point of which the Bugs knew nothing, little more than a light-hour out from the primary. The "vastness of space" was a hideously overused cliche, and like most cliches it tended to be acknowledged and then promptly forgotten.

     Prescott stood up from his command chair and stepped to the system-scale holo display, already alight with downloaded sensor data. As per convention, the system primary was a yellow dot at the center of the plot. Just as conventionally, Prescott's mind superimposed the traditional clock face on the display. Warp points generally, though not always, occurred in the same plane as a system's planetary orbits, which was convenient from any number of standpoints. The closed warp point through which they'd emerged was on a bearing of about five o'clock from the primary. No other warp points were shown—they hadn't exactly been able to do any surveying here—but planets were. The innermost orbited at a six-light-minute radius, but at a current bearing of two o'clock. The second planet's ten-light-minute-radius orbit had brought it to four o'clock. An asteroid belt ringed the primary at fourteen light-minutes, and other planets orbited still further out, but Prescott ignored them. Planets I and II were the ones Sixth Fleet had come to kill.

     A display on this scale wasn't set up to show individual ships or other astronomical minutiae. In a detailed display, those two planets would have glowed white hot from the neutrino emissions of high-energy technology and nestled in cocoons of encircling drive fields. This system was almost certainly one of the nodes of Bug population and industry that Marcus LeBlanc's smartass protégé Sanders had dubbed "home hives." It would have been a primary target even in a normal war—and this war had ceased to be normal when the nature of the enemy had become apparent. The Alliance had reissued General Directive Eighteen, which had lain dormant since the war with the Rigelians. For the second time in history, the Federation and its allies had sentenced an intelligent species to death.

     Sixth Fleet comprised two task forces. Prescott commanded TF 61, which held the bulk of the Fleet's heavy battle-line muscle: forty-two superdreadnoughts, including both Dnepr and Celmithyr'theaarnouw, from which Zhaarnak was flying his lights, accompanied by six battleships, ten fleet carriers, and twenty-four battlecruisers. Force Leader Shaaldaar led TF 62, and the stolidly competent Gorm's command was further divided into two task groups. TG 62.1, under 106th Least Fang of the Khan Meearnow'raaalphaa, had twelve fast superdreadnoughts and three battlecruisers, but those were mainly to escort its formidable array of fighter platforms: twenty-seven attack carriers and twelve fleet carriers. In support was Vice Admiral Janet Parkway, with the forty-eight battlecruisers that made up TG 62.2.

     It was strictly a fighting fleet. There was no fleet train of supply ships, no repair or hospital ships, no assault transports full of Marines. None were needed, for the objective was not conquest and occupation, but pure destruction.

     All expanses of deep space are essentially alike, even when they possess a sun for a reference point. It takes the curved solidity of a nearby planet to create a sensation of place. Depending on the planet, it can also create a psychological atmosphere.

     The planet ahead did that, in spades.

     Prescott told himself that there were perfectly good practical reasons to view that waxing sphere with apprehension. Planet I was the primary population center of this system, and its defenses were commensurate with its importance: twenty-six orbital fortresses, each a quarter again as massive as a monitor and able to fill all the hull capacity a monitor had to devote to its engines with weaponry and defenses. But the space station that was the centerpiece of the orbital installations dwarfed even those fortresses to insignificance. They were like nondescript items of scrap metal left over when that titanic junk sculpture had been welded together.

(ed note: the Bug orbital fortresses are caught by surprise with their defensive force fields down. After a furious battle, all the fortresses are destroyed. But the Bug surface defenses are now fully active)

     But as the last of those gunboats died, Prescott met Zhaarnak's eyes in the com screen, and neither needed to voice what they both knew. Planet I had no defenders left in space.
     "And now," Zhaarnak said quietly, "we will carry out our orders and implement General Directive Eighteen."
     The Bugs, it seemed, didn't favor massively hardened one-to-a-continent dirtside installations like the TFN's Planetary Defense Centers. Instead, the planet's whole land surface was dotted with open-air point defense installations. But even though they might be unarmored, there were scores of them, and each of them was capable of putting up a massive umbrella of defensive fire against incoming missiles or fighters.
     And they'd gotten that point defense on-line. That became clear when the first missile salvos went in.
     Zhaarnak and Prescott looked at the readouts showing the tiny percentage of the initial salvo which had gotten through. Then they looked at each other in their respective com screens.
     "The task force doesn't have enough expendable munitions to wear down anti-missile defenses of that density," Prescott said flatly.
     "No," Zhaarnak agreed. "We would run out of missiles before making any impression. But … our fighter strength is almost intact."
     At first, Prescott said nothing. He hated the thought of sending fighter pilots against that kind of point-defense fire. And, given the fact that TF 61's fighter pilots were Orions, it was possible that Zhaarnak hated it even more.
     "I did not want to be the one to broach the suggestion," the human finally said in the Tongue of Tongues.
     "I know. And I know why. But it has to be done." Steel entered Zhaarnak's voice, and it was the Commander of Sixth Fleet who spoke. "Rearm all the fighters with FRAMs—and with ECM pods, to maximize their survivability. And launch all of them. This is not the time to hold back reserves."

     "Aye, aye, Sir," Prescott responded formally, and nodded to Commander Bichet. The ops officer had recognized what would be needed sooner than his admiral had made himself accept the necessity, and he'd worked up the required orders on his own initiative. Now they were transmitted, and more than four hundred fighters shot away toward the doomed planet's nightside.

     It helped that the Bugs initially made the miscalculation of reserving their point defense fire for missiles. Perhaps they expected the fighters to be armed with standard, longer-ranged fighter missiles. Or perhaps they even believed that the fighter pilots were acting as decoys, trailing their coats to deceive the defenders into configuring their point defense to engage them instead of the battle-line's shipboard missiles in hopes of helping those missiles to sneak through. But then the defenders realized they were up against FRAMs, against which no tracking system could produce a targeting solution during their brief flight, and they began concentrating on the fighters that were launching those FRAMs.

     A wave of flame washed through the Orion formation, pounding down upon it in a fiery surf of point defense lasers and AFHAWK missiles. It glared like a solar corona, high above the night-struck planetary surface, and forty-one fighters died in the first pass.

     But despite that ten percent loss ratio, the remaining fighters put over two thousand antimatter warheads into the quadrant of Planet I which was their target on that pass.

     The darkened surface erupted in a myriad pinpricks of dazzling brightness. From those that were ocean strikes, complex overlapping patterns of tsunami began to radiate, blasting across the planetary oceans at hundreds of kilometers per hour like the outriders of Armageddon. More explosions flashed and glared, leaping up in waves and clusters of brilliant devastation, and as he watched, a quotation rose to the surface of Raymond Prescott's mind. Not in its original form—classical Indian literature wasn't exactly his subject. No, he recalled it at second hand. Four centuries earlier, one of the fathers of the first primitive fission bomb, on seeing his brain child awake to apocalyptic life in the deserts of southwestern North America, had whispered it aghast.

     And now Raymond Prescott whispered it, as well.
     "I am become Death, the destroyer of worlds."
     Amos Chung was close enough to hear.
     "Uh … Sir?"
     "Oh, nothing, Amos," Prescott said, without looking up from the display on which he was watching a quarter of a planet die. "Just a literary quote—a reference to Shiva, the Hindu god of death."

     Zhaarnak and Prescott didn't know that at first, of course, given the communications lag. What they did know, as they drew away from Planet I an hour and ten minutes after launching their first missile at it, was that they had killed at least ninety-five percent of its population outright, and that the few survivors were too irradiated to live long enough to experience nuclear winter on that dust-darkened surface.

From THE SHIVA OPTION by David Weber and Steve White (202)

     Shus and his staff watched the screens and instruments, but nothing happened. Finally the moment came and the tension ebbed away. The fleets were in position—it was time to begin the last battle of the Terra-Sparta War.
     "So be it," said Shus, staring at the screens devoid of the enemy. He no longer felt any sympathy for these people; they had had their chance to come out and die fighting. Now they would be slaughtered like cowering animals. "Commence bombardment!"
     The order flashed nearly instantaneously through the fleets in close orbits around the planet. Knobs were spun and buttons pushed. Smoothly, on near-frictionless hinges, the bomb-bay doors of the battle wagons opened out like the petals of a flower seeking the sun—or in this case, the planet Earth. Then, as naturally as plants releasing millions of spores, the cargoes of bombs were carried away as if by an unseen wind.
     The number of bombs grew, increased incredibly. It seemed that they would never cease spewing forth from the bomb-bays. Swarm upon swarm fell toward Earth in the grip of gravity.

Shus shook his head as he watched the bombs fall away from his ships. He had conducted many a siege against hostile planets, but he had never undertaken anything like this before. Short of using outlawed megatons, this was the ultimate. It was against the rules of space warfare to reduce a planet to ashes with one bomb. He was circumventing those rules by using a million bombs. Never before had it been tried, and he guessed it would never be again, for there was no other race quite like Man. Never had a race been so dreaded.
     The bombs touched the Earth's atmosphere like drops of rain on a roof. The whole sky was darkened with their sinister forms. And even as those in the vanguard struck the atmosphere, still more issued forth from the bellies of the battleships.
     The bombs hurtled down like a thundering deluge, their heat shields glowing red from the friction of the air. Here and there flaws in the heatshields of the hastily mass-produced weapons caused them to burn up. These appeared as colorfully spectacular shooting stars to awed viewers on the Earth.
     The defenders had long ago picked up the falling bombs. Instruments and computers had tracked them diligently. Suddenly the Earth erupted with scintillating light. It was the flickering of the energy beams of Earth filling the heavens.
     Shus smiled grimly. They were trying to shield the planet. The attempt was doomed to failure. There were too many bombs. The Terran defensive fire was unbelievable, incredible. An ordinary bombardment would have been nearly neutralized. Dane Barclay had prepared well, but not even he could defend against a bombardment on this scale.
     Thousands of bombs were hit and exploded high in the atmosphere, turning night into day and day into eye-searing brightness. But for every bomb hit, ten others fell unmolested. And still more were coming from the bomb-bays of the ships above. The laser batteries stabbed desperately and with clever efficiency, but they could not stop all the bombs or even a tenth of them.
     The bombs struck.
     They smashed down everywhere, wiping out laser batteries and cities, homes and roads. Mushrooms sprouted on the Earth as if the planet were one huge mushroom farm. The atmosphere and the surface of the planet became a virtual hell. All the things Man had worked for and built were vaporized, smashed flat, obliterated within seconds.
     The tall buildings were flattened, shattered or blown apart. Like falling dominoes they toppled to lie in ruin. Flames leapt up and the once proud structures, despite their supposed fireproofness, burned like logs casually thrown upon a fire.
     Blinding flashes, coming almost continuously, seared earth and rock. Metals melted and stone bubbled. Lava flowed where no volcanos existed. Land quaked and trembled. Forests burned everywhere, huge seas of flame. Small lakes and rivers dried up instantly, leaving only barren beds to mark their former presence.
     Mountains gained dazzling halos as the bombs sought to reduce them.
     Even underground, no one was safe, for the bombs fell and blasted their way through with terrible violence. Hastily constructed bunkers caved in, burying the occupants dead and alive.
     The bombs spared nothing. They fell everywhere.
     The seas boiled. Fish died by the billions. Mighty tidal waves raced across the land, battling each other and attempting blindly to batter whatever got in the way. Shus had been right; never in galactic history, since the rules of civilized warfare had been set down, had such destruction been visited upon a planet. One bomb was against the rules—a million were not.
     Doomsday was upon the Earth.

     As the scout ships moved through the death-shroud atmosphere of Earth, their instruments and equipment sent data and pictures back to the command ship. In the control room Shus and his staff studied the data and viewscreens intently.
     There was no doubt that Earth had been ravaged as no other planet in the annals of space war. The cities were gone. They had been leveled, pulverized, vaporized. In some places mounds of rubble were visible. In others, where the bomb concentration had been greater, only deep craters remained. The entire planet bore the pock marks of the bombardment. The atmosphere was a nightmare of storm and hurricane, of thunder and lightning, of typhoons and tornados, of monsoons and gigantic fires that turned rain to steam. Upon the heels of the cataclysmic bombs had come condensation of moisture and the creation of huge rainfalls. Drops of rain large as fists drenched the land. The tormented atmosphere reacted by sending killer winds hundreds of miles per hour over the leveled land, uprooting, sweeping all with it.
     While the wind blew and the rain pelted heavily, the world burned. Forests, buildings, parks, vehicles, all burned. Anything that could burn, did. Smoke filled the air. Never had there been anything like it before. Even where the noon-day sun shone fiercely upon the Earth, all was in darkest gloom.
     Shus watched the angered sea batter and beat the land, watched it send towering waves to submerge the land. Tens of thousands of miles of seacoast were overrun and claimed by the water.
     The huge planetary lasers that might have cost him dearly in ships and Spartans were gone—blasted out of existence by the saturation bombardment. Of the battle fleets of Terra there was no sign.
     As he looked at the overwhelming devastation visited upon the planet below, he wanted to believe that those fleets had perished in the bombardment, that the planet was defenseless, that the battle had already been won, but he could not. He knew otherwise. Bitter experience told him that beneath that ravaged outer crust there were fleets, laser batteries, soldiers and cities. But the bombardment, beyond anything they could possibly have expected, must surely have dealt their remaining forces and plan of defense a staggering—if not fatal—blow.
     "There is little point in continuing the bombardment," he said to his officers. It would be a case of diminishing returns, and the remaining bombs would best be of service against specific targets as they were uncovered.
     "Phase One, I would say, is an overwhelming success. We have destroyed the static defenses, leveled the cities and no doubt killed most of the population.
     "We will move to Phase Two now: the removal of surviving defensive forces. Let's go down and get this over with."
     The Spartan fleets descended into the dark gloom, seeking the surviving forces of once proud Earth.

From SIEGE OF EARTH by John Faucett (1971)

All the energy put into achieving that velocity had transformed the Intruder into a kinetic storage device of nightmarish design. If it struck a world, every gram of the vessel's substance would be received by that world as the target in a linear accelerator receives a spray of relativistic buckshot. Someone, somewhere, had built and was putting to use a relativistic bomb — a giant, roving atom smasher aimed at worlds...

The gamma-ray shine of the decelerating half was also detectable, but it made no difference. One of the iron rules of relativistic bombardment was that if you could see something approaching at 92 percent of light speed, it was never where you saw it when you saw it, but was practically upon you...

In the forests below, lakes caught the first rays of the rising Sun and threw them back into space. Abandoning the two-dimensional sprawl of twentieth-century cities, Sri Lanka Tower, and others like it, had been erected in the world's rain forests and farmlands, leaving the countryside virtually uninhabited. Even in Africa, where more than a hundred city arcologies had risen, nature was beginning to renew itself. It was a good day to be alive, she told herself, taking in the peace of the garden. Then, looking east, she saw it coming — at least her eyes began to register it — but her optic nerves did not last long enough to transmit what the eyes had seen.

It was quite small for what it could do — small enough to fit into an average-sized living room — but it was moving at 92 percent of light speed when it touched Earth's atmosphere. A spear point of light appeared, so intense that the air below snapped away from it, creating a low-density tunnel through which the object descended. The walls of the tunnel were a plasma boundary layer, six and a half kilometers wide and more than 160 deep — the flaming spear that Virginia's eyes began to register — with every square foot of its surface radiating a trillion watts, and still its destructive potential was but fractionally spent.

Thirty-three kilometers above the Indian Ocean, the point began to encounter too much air. It tunneled down only eight kilometers more, then stalled and detonated, less than two-thousandths of a second after crossing the orbits of Earth's nearest artificial satellites.

Virginia was more than three hundred kilometers away when the light burst toward her. Every nerve ending in her body began to record a strange, prickling sensation — the sheer pressure of photons trying to push her backward. No shadows were cast anywhere in the tower, so bright was the glare. It pierced walls, ceramic beams, notepads, and people — four hundred thousand people. The maglev terminal connecting Sri Lanka Tower to London and Sydney, the waste treatment centers that sustained the lakes and farms, all the shops, theaters, and apartments liquefied instantly. The structure began to slip and crash like a giant waterfall, but gravity could not yank it down fast enough. The Tower became vapor before it could fall half a meter. At the vanished city's feet, the trees of the forest were no longer able to cast shadows; they had themselves become long shadows of carbonized dust on the ground.

In Kandy and Columbo, where sidewalks steamed, the relativistic onslaught was unfinished. The electromagnetic pulse alone killed every living thing as far away as Bombay and the Maldives. All of India south of the Godavari River became an instant microwave oven. Nearer the epicenter, Demon Rock glowed with a fierce red heat, then fractured down its center, as if to herald the second coming of the tyrant it memorialized. The air blast followed, surging out of the Indian Ocean -- faster than sound — flattening whatever still stood. As it slashed north through Jaffna and Madurai, the wave front was met and overpowered by shocks rushing out from strikes in central and southern India.

Across the face of the planet, without warning, thousands of flaming swords pierced the sky...

Then out of no where — out of the deep impersonal nowhere — came a bombardment that even the science fiction writers had failed to entertain.

Just nine days short of America's tricentennial celebrations, every inhabited planetary surface in the solar system had been wiped clean by relativistic bombs. Research centers on Mars, Europa, and Ganymede were silent; even tiny Phobos and Moo-kau were silent. Port Chaffee was silent. New York, Colombo, Wellington, the Mercury Power Project and the Asimov Array. Silent. Silent. Silent.

A Valkyrie rocket's transmission of Mercury's surface had revealed thousands of saucer-shaped depressions where only hours before had existed a planet-spanning carpet of solar panels. The transmission had lasted only a few seconds — just long enough for Isak to realize there would be no more of the self-replicating robots that had built the array of panels and accelerators, just long enough for him to understand that humanity no longer possessed a fuel source for its antimatter rockets — and then the transmission had ceased abruptly as the Valkyrie disappeared in a silent white glare.

Presently, most of the station's scopes and spectrographs were turning Earthward, and Isak found it impossible to believe what they revealed. The Moon rising over Africa from behind Earth was peppered with new fields of craters. The planet below looked like a ball of cotton stained grayish yellow. The top five meters of ocean had boiled off under the assault, and sea level air was three times denser than the day before — and twice as hot...

The sobering truth is that relativistic civilizations are a potential nightmare to anyone living within range of them. The problem is that objects traveling at an appreciable fraction of light speed are never where you see them when you see them (i.e., light-speed lag). Relativistic rockets, if their owners turn out to be less than benevolent, are both totally unstoppable and totally destructive. A starship weighing in at 1,500 tons (approximately the weight of a fully fueled space shuttle sitting on the launchpad) impacting an earthlike planet at "only" 30 percent of lightspeed will release 1.5 million megatons of energy -- an explosive force equivalent to 150 times today's global nuclear arsenal... (ed note: this means the freaking thing has about nine hundred mega-Ricks of damage!)

The most humbling feature of the relativistic bomb is that even if you happen to see it coming, its exact motion and position can never be determined; and given a technology even a hundred orders of magnitude above our own, you cannot hope to intercept one of these weapons. It often happens, in these discussions, that an expression from the old west arises: "God made some men bigger and stronger than others, but Mr. Colt made all men equal." Variations on Mr. Colt's weapon are still popular today, even in a society that possesses hydrogen bombs. Similarly, no matter how advanced civilizations grow, the relativistic bomb is not likely to go away...

From THE KILLING STAR by Charles Pelligrino and George Zebrowski

Planetary Nut-Cracker

If the enemy planet has gotta go, but the rest of the enemy solar system might be of some use, and you the capability of moving planets, it may be time for a Nut-Cracker.

You take a sizeable planet which you can spare, somehow transport it into the enemy's solar system, then fly the planet on a collision course with the enemy world. If you really want to splatter the enemy homeworld, you fly in two planets on diametrically opposed courses with the enemy in the middle. Sort of like a hammer and anvil. A cosmic-scale sledge-o-matic.

This is a strictly handwavium space-opera style weapon. Very cinematic but nohow nowhere scientifically possible.


      "Let us all sit down and be comfortable," he continued, changing into the Kondalian tongue without a break, "and I will explain why we have come. We are in most desperate need of two things which you alone can supply—salt, and that strange metal, 'X'. Salt I know you have in great abundance, but I know that you have very little of the metal. You have only the one compass upon that planet?"
     "That's all—one is all we set on it. However, we've got close to half a ton of the metal on hand—you can have all you want."
     "Even if I took it all, which I would not like to do, that would be less than half enough. We must have at least one of your tons, and two tons would be better."
     "Two tons! Holy cat! Are you going to plate a fleet of battle cruisers?"
     "More than that. We must plate an area of copper of some ten thousand square miles—in fact, the very life of our entire race depends upon it."

     "It's this way," he continued, as the four earth-beings stared at him in wonder. "Shortly after you left Osnome we were invaded by the inhabitants of the third planet of our fourteenth sun. Luckily for us they landed upon Mardonale, and in less than two days there was not a single Osnomian left alive upon that half of the planet. They wiped out our grand fleet in one brief engagement, and it was only the Kondal and a few more like her that enabled us to keep them from crossing the ocean. Even with our full force of these vessels, we cannot defeat them. Our regular Kondalian weapons were useless. We shot explosive copper charges against them of such size as to cause earthquakes all over Osnome, without seriously crippling their defenses. Their offensive weapons are almost irresistible—they have generators that burn arenak as though it were so much paper, and a series of deadly frequencies against which only a copper-driven ray screen is effective, and even that does not stand up long."
     "How come you lasted till now, then?" asked Seaton.
     "They have nothing like the Skylark, and no knowledge of intra-atomic energy. Therefore their space-ships are of the rocket type, and for that reason they can cross only at the exact time of conjunction, or whatever you call it—no, not conjunction, exactly, either, since the two planets do not revolve around the same sun: but when they are closest together. Our solar system is so complex, you know, that unless the trips are timed exactly, to the hour, the vessels will not be able to land upon Osnome, but will be drawn aside and be lost, if not actually drawn into the vast central sun. Although it may not have occurred to you, a little reflection will show that the inhabitants of all the central planets, such as Osnome, must perforce be absolutely ignorant of astronomy, and of all the wonders of outer space. Before your coming we knew nothing beyond our own solar system, and very little of that. We knew of the existence of only such of the closest planets as were brilliant enough to be seen in our continuous sunlight, and they were few. Immediately after your coming I gave your knowledge of astronomy to a group of our foremost physicists and mathematicians, and they have been working ceaselessly from space-ships—close enough so that observations could be recalculated to Osnome, and yet far enough away to afford perfect 'seeing,' as you call it."

     "But I don't know any more about astronomy than a pig does about Sunday," protested Seaton.
     "Your knowledge of details is, of course, incomplete," conceded Dunark, "but the detailed knowledge of the best of your Earthly astronomers would not help us a great deal, since we are so far removed from you in space. You, however, have a very clear and solid knowledge of the fundamentals of the science, and that is what we need, above all things."
     "Well, maybe you're right, at that. I do know the general theory of the motions, and I studied some Celestial Mechanics. I'm awfully weak on advanced theory, though, as you'll find out when you get that far."
     "Perhaps—but since our enemies have no knowledge of astronomy whatever, it is not surprising that their rocket-ships can be launched only at one particularly favorable time; for there are many planets and satellites, of which they can know nothing, to throw their vessels off the course.

     "Some material essential to the operation of their war machinery apparently must come from their own planet, for they have ceased attacking, have dug in, and are simply holding their ground. It may be that they had not anticipated as much resistance as we could offer with space-ships and intra-atomic energy. At any rate, they have apparently saved enough of that material to enable them to hold out until the next conjunction—I cannot think of a better word for it—shall occur. Our forces are attacking constantly, with all the armament at our command, but it is certain that if the next conjunction is allowed to occur, it means the end of the entire Kondalian nation."'
     "What d'you mean 'if the next conjunction is allowed to occur?'" interjected Seaton. "Nobody can stop it."
     "I am stopping it," Dunark stated quietly, grim purpose in every lineament. "That conjunction shall never occur. That is why I must have the vast quantities of salt and 'X'. We are building abutments of arenak upon the first satellite of our seventh planet, and upon our sixth planet itself. We shall cover them with plated active copper, and install chronometers to throw the switches at precisely the right moment. We have calculated the exact times, places, and magnitudes of the forces to be used. We shall throw the sixth planet some distance out of its orbit, and force the first satellite of the seventh planet clear out of that planet's influence. The two bodies whose motions we have thus changed will collide in such a way that the resultant body will meet the planet of our enemies in head-on collision, long before the next conjunction. The two bodies will be of almost equal masses, and will have opposite and approximately equal velocities; hence the resultant fused or gaseous mass will be practically without velocity and will fall directly into the fourteenth sun."

     "Wouldn't it be easier to destroy it with an explosive copper bomb?"
     "Easier, yes, but much more dangerous to the rest of our solar system. We cannot calculate exactly the effect of the collisions we are planning—but it is almost certain that an explosion of sufficient violence to destroy all life upon the planet would disturb its motion sufficiently to endanger the entire system. The way we have in mind will simply allow the planet and one satellite to drop out quietly—the other planets of the same sun will soon adjust themselves to the new conditions, and the system at large will be practically unaffected—at least, so we believe."

     Seaton's eyes narrowed as his thoughts turned to the quantities of copper and "X" required and to the engineering features of the project; Crane's first thought was of the mathematics involved in a computation of that magnitude and character; Dorothy's quick reaction was one of pure horror.
     "He can't, Dick! He mustn't! It would be too ghastly! It's outrageous—it's unthinkable—it's—it's—it's simply too horrible!" Her violet eyes flamed, and Margaret joined in:
     "That would be awful, Martin. Think of the destruction of a whole planet—of an entire world—with all its inhabitants! It makes me shudder, even to think of it."
     Dunark leaped to his feet, ablaze. But before he could say a word, Seaton silenced him.
     "Shut up, Dunark! Pipe down! Don't say anything you'll be sorry for—let me tell 'em! Close your mouth, I tell you!" as Dunark still tried to get a word in, "I tell you I'll tell 'em, and when I tell 'em they stay told! Now listen, you two girls—you're going off half-cocked and you're both full of little red ants. What do you think Dunark is up against? Sherman chirped it when he described war—and this is a real he-war; a brand totally unknown on our Earth. It isn't a question of whether or not to destroy a population—the only question is which population is to be destroyed. One of them's got to go. Remember those folks go into a war thoroughly, and there isn't a thought, even remotely resembling our conception of mercy in any of their minds on either side. If Dunark's plans go through the enemy nation will be wiped out. That is horrible, of course. But on the other hand, if we block him off from salt and 'X,' the entire Kondalian nation will be destroyed just as thoroughly and efficiently, and even more horribly—not one man, woman, or child would be spared. Which nation do you want saved? Play that over a couple of times on your adding machine, Dot, and let me know what you get."
     Dorothy, taken aback, opened and closed her mouth twice before she found her voice.
     "But, Dick, they couldn't possibly. Would they kill them all, Dick? Surely they wouldn't—they couldn't."
     "Surely they would—and could. They do—it's good technique in those parts of the Galaxy. Dunark has just told us of how they killed every member of the entire race of Mardonalians, in forty hours. Kondal would go the same way. Don't kid yourself, Dimples—don't be a child. War up there is no species of pink tea, believe me—half of my brain has been through thirty years of Osnomian warfare, and I know precisely what I'm talking about. Let's take a vote. Personally, I'm in favor of Osnome. Mart?"

From SKYLARK THREE by E. E. "Doc" Smith (1930)

(ed note: in the far future of space opera, all nine worlds of the solar system have been colonized. But one fine day the sun starts to cool off. To avoid a frozen death, the planets resolve to place gigantic atom-blasts on each world, fly the planets out of the solar system, and find a warm young star.

They pass several unsuitable stars, but disaster strikes at the star Antolia. The star is going to go nova. And the natives are rather upset at that. The Antolians attempt to capture the passing Solar planets but are beaten off. However, the copy-cat Antolians put atom-blasts on their planets and set off in hot pursuit. The Solar planets finally find a new home star, but the Antolian planets are coming to invade. What to do?)

      WE STARED, our triumph frozen. In the telescopes the four Antolian planets were plainly visible, passing Walaz and moving on with mounting speed toward us.
     "We must do something!” Hurg cried. "If those Antolian worlds reach this sun and take up orbits around it, it means endless war with them, war that may result in our destruction!”
     "We can not stop them from coming on,” Julud said sadly. "I had hoped they would stop their worlds at Walaz, but they are coming on.”
     "If there were only some way to stop them before they get here!” Runnal exclaimed.
     An idea seared across my brain. "There is a way of stopping them!” I cried. "I can stop them with my world, with Mercury!

     "Don’t you understand?” I said. "All of Mercury’s inhabitants can be transferred to other of our worlds and then I’ll take Mercury out and crash it head-on into those four oncoming worlds!”
     "Good, and I’ll go with you, Lonnat!” cried Hurg.
     "And I too!” said Tolarg, eyes gleaming.
     Immediately Julud ordered the transfer of Mercury’s people to other worlds as I requested. All our worlds’ ships swarmed to Mercury and engaged in transporting Mercury’s people to the other planets. It was so tremendous a task that by the time Tolarg and Hurg and I with my assistants in the control-tower were the only people left on Mercury, the four oncoming worlds of the Antolians had almost reached Vira.

     Quickly I opened up Mercury’s propulsion-blasts and sent the little planet hurtling out from Vira, back along the way we had come toward the four nearing worlds. Tensely I and Tolarg and Hurg held it toward them. Outside the control-tower were our waiting ships.
     Toward each other, booming through space with immense speed, thundered Mercury and the four oncoming worlds. The Antolian worlds loomed larger and larger before us. Then they veered to one side.
     "They’re veering! 'They’re trying to escape the collision!” cried Hurg. "It’ll do them no good!” I exclaimed. I swung Mercury aside in the same direction to meet them.
     Again the column of four planets veered as they rushed closer, seeking desperately to escape the oncoming doom. Again I swung Mercury to meet them. Then the foremost of the oncoming Antolian worlds loomed immense in the heavens before our rushing planet.
     "They’re going to crash!" I cried. "Up and away before they meet!”
     "Up and away!” yelled Tolarg and Hurg as we threw ourselves from the control-tower into the ships.
     Our ships darted up like lightning. The rushing globe of Mercury was almost to the oncoming sphere of the first Antolian world. And then as we shot away from them into space, they met!

     There was no sound in the soundless void, but there was a blinding, dazing glare of light that darkened even the great sun behind us for the moment, and then the two worlds became glowing red, molten, blazing with doom! A wave of force struck through space that rocked our fleeing ships.
     And behind the first Antolian world the other three of the column came on and crashed into that glowing mass! One by one they crashed and were destroyed; and then the four worlds were one white hot mass that veered oflF into space at right-angles to Vira and away from it. The four colliding worlds had become a new small sun!
     I stared after that receding, dazzling mass. There were tears in my eyes as I watched it move away, with the remains of Mercury in it. Mercury, my world, that I had piloted across the great void through the suns only to hurl it at the last into doom.
     Hurg was grasping my arm excitedly. "We’ve won, Lonnat!” he cried. "The Antolians and their worlds destroyed, and Vira ours now for our eight remaining worlds!”
     Tolarg held out his hand to me, all mockery gone from his face now. "What you said was right, Lonnat,” he said. "It’s not the size of a planet that measures its importance. Yours has saved us all.”

From THUNDERING WORLDS by Edmond Hamiltion (1934)

      "Be seated, friends," said Andar Minot, rising, the ceremonial greeting over. "We have called on you again. Our plans are more exact, and an exact plan requires an exact answer.
     "First: By careful measurement of effects of known forces, we have been able to determine with accuracy the mass of each of our moons. We now know with exactitude the load that the driving engines must move.
     "Second: astronomers have been observing and calculating, and the plan is made exactly according to their results. The smaller of our missiles, Ma-ran, will be used first. This will be torn from its orbit at a time when it is advantageously situated, and the acceleration of its orbital velocity will tear it loose in the exact direction we wish. It will then be projected—"
     Carefully the plan was discussed, and the movements of each of the moons considered. Ma-ran would be equipped with a huge driving engine that would tear it loose from its orbit, to hurl down on Teff-el and Teff-ran, and the orbital forts. Ma-ran, though far lighter than Ma-kanee, would have a driving engine of equal power, because it would be expected to be mobile and capable of real motion, and be forced to pursue and catch the not entirely helpless orbital forts.
     Ma-kanee, on the other hand, would merely hurl its quintillions of tons of mass on the planet— The plan was made, and the work well under way. That same day Aarn and Spencer went out to Ma-kanee where the work was being done.

     The cavern was being expanded in two dimensions, the floor and the ceiling already determined. Artificial gravity plates had been installed in the place to make work easier, but the gravity had been reduced to only one-half normal for Magyans. The men, trained, soldier-mechanicians every one of them, were working under the commands of their officers, and rapidly setting up new racks of power machinery. Huge converters for the strange momentum oscillators were going in now. Bank after bank of oscillators.
     "We have to drive conductors for miles through the rock in every direction to make certain we'd get perfect distribution of the momentum waves. That's the only reason we can move these moons, of course. If we'd had to depend on the space-drive disks, it would have been impossible. Just torn the thing to pieces."
     Here and there they could see dark tunnels still unfilled, borings where Shal torpedo after Shal torpedo had burrowed its way on and on. The borings were less than six inches in diameter and hollow rods of aluminum had been thrust deep into them, to spread the momentum waves through the planetoid.

     A sudden, dull, humming note sounded twice. Carlisle started, and the other two stiffened. "First warning," said Aarn softly, relaxing. "That's the warning from the astronomers on Ma-kanee. They sent the first warning and they'll begin accelerating now, in about thirty-two and a half minutes. They're starting the oscifiator tubes, warming them up."
     Unconsciously, Aarn looked down. Two enormous glass tanks loomed thirty feet high, two tanks filled with metal plates, and huge heaters, grids and screens—the oscillator control tubes. Beside them loomed two cold tubes with a sprinkling of mercury over them, about ten feet high, and some five in diameter. They were the "chopper" tubes which were designated to chop the current off abruptly at an enormous frequency—
     Again the two dull humming notes. "The choppers!" said Aarn softly. His eyes shifted to the great hulking lumps of the momentum drive itself. "That comes next—run direct current through them for a while to warm them. Then when they break that current the oscillation is started—"
     Three notes. "Let's go below." Aarn led the way down. In the control room there was quiet confusion. Men were rapidly walking back and forth. Seven different radio positions were occupied. Three more television control positions, and, finally, the great panel where the main controls were, with the three television screens and the selector dials which would throw any part of space on the screen, or into any one of the telescopes.

     A low, powerful throbbing hum sounded. As Aarn threw a switch, the television disk before him lighted up suddenly, as the beating note ceased, and the face of the controller on Ma-kanee appeared. His face was drawn and intent as he threw a switch. Suddenly an enormous cat began to whine, its whine mounted, and steadied to a great, gentle purr. Another—another—another—
     "Gyroscopes," said Aarn. "They have to stop the spin of the moon first. They have small momentum controls that are controlled by the big gyroscopes. They'll hold it firm."
     There was a steady, grumbling roar sounding now from the speaker. Ma-kanee was being stopped in her age-long rotation. Only slight disturbance was caused, because every particle was being decelerated, but there was a certain amount of oblateness, and this was flattening out, or rounding out, with groaning protest.
     The controller started, and turned to someone behind and to one side of him. "All proceeding as directed. The main tubes and apparatus are warm now, ready for operation if necessary."
     The man behind him made some inaudible answer, and the controller, Hirun Theralt, checked all the dials before him.

     Quickly the time passed. All the men on Ma-kanee were busy, working frantically as the moment of the start approached. Finally the controller spoke directly into his microphone.
     "To the Council of Astronomy: My rotation shows zero. Is this correct?"
     A voice answered metallically from a concealed speaker. "That is correct. Read off your coordinates, and we will give you the correct axes."
     "X-543-27. Y-732-45. Z-982.38."
     "Set the controllers at: X-234-31, Y-135-52, Z-64-32. Let the master controls rest at this, and watch only your deviation axes readings. Keep these as directed in further messages. Are they now reading zero?"
     "They are zero, and are holding. The automatic antirotation apparatus has been attached, and standardized."
     "Continue as instructed, with acceleration along X at the rate of 752,000 units. At the second signal, increase to 1,435,000 units, and continue except as directed."
     The controller repeated the instructions, his voice trembling a trifle.
     Minutes dragged. Then finally came a soft buzz. Another, another— "At the tenth," said Aarn softly, "he will start—"
     Eight-nine-ten- A groan echoed softly from the loudspeaker, and a great snarling vibration echoed instantly, and died in a shrillness. A blue light glowed down from above, where the great mercury tube boiled in sudden activity.
     "Acceleration at seven-five-two," said the controller.
     "That means," explained Aarn, "seven hundred and fifty thousand millions tons of force. The plan to increase it by steps—"

     On the screen, a sudden blankness came, a shift, then the image of an elderly, gray-haired man. "The view we will send now, is a model map of the actual, and the correct theoretical position of Ma-kanee. This will show the deviation from her normal orbit"
     The screen was black, save for a green circle, Magya, two red and blue dots. The dots were points on great ellipses. Slowly, slowly, they could see the red dot near Magya creeping along. The others seemed almost motionless.
     Hours later, the inner red dot had made a complete circuit, and now there were three red dots, and two blue. Ma-kanee's dot had split in two. One of the Ma-kanee dots was slowly circling on a greater, and ever-growing orbit More and more power was being applied. The slow acceleration was increasing gradually.
     Again Ma-ran swung about in her orbit—and now Makanee was hundreds and thousands of miles from her assigned orbit. She was struggling mightily now, with increasing momentum and centrifugal force to pull herself free of the bonds of Magya. Her orbit was lengthening more and more toward a straight line. She was on the night side of Magya now, soon she would fly off on the day side—and escape toward Anrel. Then the acceleration that was being applied would change in direction, change to bend the normal orbital speed about Anrel toward the sun, instead of at right angles. The centrifugal force no longer acting against it, Anrel's pull might drag the moon even faster toward Teffel.

     The screen was showing many different scenes now. At length it showed a scene that was relayed from a ship far away—a ship hanging off Teff-el! An investigator, one of those that still had not been found, was showing the streets of Cantak.
     Teff-el had seen and understood, when Ma-kanee started her movement. Not fully understood, for they believed it only a great weapon—a great battleship that no battleship could fight. A battleship that would come down and ray them out of existence—destroy every ship, every orbital fort—and finally the forts on Teff-ran. Then Ma-kanee, they feared, would set up in an orbit about Teff-el, and never again would a Tefilan ship be able to reach the surface! Every city isolated—till tunnels could be dug to connect them!
     There was panic, and excitement. Tremendous loads of supplies were being rushed out to Teff-ran, that she might defend the planet, perhaps conquer even the mobile moon!
     Aarn smiled grimly. "Futile," he said. "Nothing could help. They might carry some of their people away—but the Magyan fleet is already waiting just off Teff-el. They can't get away. There are almost no ships near here."
     "What if the Tefilans attack?" asked Carlisle.
     Aarn lighted a cigarette carefully. There were few left now. "If they did, what would they attack? The moon? Much good that would do them. Magya? Where? How? There's nothing on the surface, and they couldn't reach the cities before our fleet could start in on one of their orbital forts, and start cleaning up thoroughly. They'd have to be called home."

     It took days, and long before the process was finished, Tefflan ships of war were circling viciously off Ma-kanee- and occasionally there was a flash of instantaneous blue incandescence as the inconceivable coils of the moon ship were shorted by a mere cruiser.
     But finally Ma-kanee sailed proudly free, and bent her orbit more and more toward Teff-el.
     And then, one day, there was further stirring among Magya's children, and Teff-el was stricken by horrible panic.
     Aarn, his iron nerves alone subduing the trembling that crept into them, pressed a series of controls. And huge oscillator tubes glowed dull-red. The power board sprang into life across the way, and Aarn read its warnings and its story, and returned to his own control board.
     The tremendous transformers hummed suddenly and the great chopper tubes glowed green-blue, great arcs roared as tumbler switches snapped across. Then the shrill snarl of speeding gyroscopes. The enormous power plant that was Ma-ran, was waking to life. Huge cables that spread out like the threads of a three-dimensional spider web began to glow softly as a low power oscillated through them, and gently, but swiftly, the spin of Ma-ran was slowed. There were no observatories outside here. Ma-ran was to be far more active and far more destructive than her larger sister as she ran amuck.
     On Ma-kanee, observatories had been dismounted. There were no more machines, no lenses—only the transpon-projectors that bit into the feeble attacking moths of the cruisers. The apparatus had been carried away, and already, as the great coils were exhausted in accelerating the ship that was a world, they were being recharged again. Then, when these were again discharged, the great supply ships would take them on. Before Ma-kanee finally struck Teff-el, it would be little more than a hollow moon. The machinery would be salvaged. But Ma-ran was to be an active deadly thing all her short life as a ship; there would be no salvaging of machinery here. Every coil was to be emptied not once, not twice, but four times.
     And as the final signal came, Aarn was on his own. He had only a ship. Carefully he had worked out the course he wanted to follow, and now, with his enormous craft, he turned in the tremendous power. A shrill whine built up, the moon trembled and chattered with the fall of rocks outside, loose material suddenly sliding as the planetoid trembled, started—and moved!

     "I THINK OUR course will be X-235-89," Aarn said. His voice was low, and tense. Ma-kanee was thousands of miles behind now—but in the forward televisor disk, Teff-el showed a huge, round disk. And about the little moon, traveling now with a velocity of thousands of miles an hour, but slower now than Ma-kanee, a fleet of great battleships wove a constant pattern. An angry, threatening halo of destruction, strengthened and widened by the heavy cruisers, and light cruisers, and destroyers. Almost the entire navy was here, for Ma-kanee needed no protection now. Ma-kanee was deserted. There was no apparatus, save for two or three televisors, and a small crew of men to observe. Ma-kanee was a hollow hulk, seven hundred miles in diameter, driving down on a doomed world.
     Teff-el was under no delusions now. They knew that Ma-kanee was not intended to capture forts, and their moon— they knew what it meant. And that was the reason for the heavy protection that was offered Ma-ran. The Tefflans knew that Ma-kanee had no driving engine, that they had no possible weapon capable of turning it. Their only hope lay in capturing Ma-ran, and using it to batter Ma-kanee aside.
     The buzz saw of circling, deadly ships was not revolving unhindered. Scout ships of the Tefflan fleet kept darting in, hoping to launch an unsuspected torpedo, or some weapon which might pierce the magnetic and antigravity shields.

     “Orbital fort,” said Spencer, pointing to a sudden, unfocused, black shadow that swam leisurely across the view. “Will they be dangerous?”
     Aarn shrugged his shoulders. “Probably. They may be able to reach us with the new death-ray projectors. We will know sooner or later.”
     “Two hours and thirty-one minutes,” said Spencer.
     The planet was growing rapidly now. Far off to the left loomed Teff-ran, sweeping rapidly nearer. Teff-ran would not cross their path in this first circuit. “I hope they calculated the mass of those orbital forts right,” sighed Aarn. “It will ruin our plans, if they don’t give the right reaction.”
     “We’re supposed to hit three of them in this first swing, five in the next—if the thing works. We’re going above orbital speed. Those collisions, with loss of momentum, or better, increase of mass, are counted on to slow us for an exceedingly elliptical orbit. The five, next time, will round out our orbit again, act as a resisting medium—molecules in a supergas to slow us down."

     "I've been wondering—won't the shock of the tremendous mass of those forts be enough to split this moon wide open, split it, anyway, so that the momentum drive won't operate? Or so the apparatus here is smashed?"
     Aarn shook his head slowly. "They'll mainly bury them selves in this. We have fifty miles of solid rock above us. A fort—even one as huge as they are—will be of no great consequence. Remember, the rate of collision, the additive velocities, will make the relative velocities practically thirty-five miles a second. The result will be volatilization for the first fort, and for some of our rocky layer, the lower rate of collision of the second, will make it slightly less severe. The main thing, though, is that the rock won't transmit the shock at all!"
     "Why not, it certainly isn't dough?"
     "No, but—it can't transmit any shock, any push, at speed greater than the speed of sound through it. That speed of collision is greater than the speed of sound. Ergo, it won't be transmitted as a push. It will simply reduce the rock it hits to powder, expend its energy smashing the rock, breaking it, demolishing it—and not on moving."
     "Also—why don't those orbital forts get out of the way?" asked Spencer
.      "Combination of reasons. They could get part way out of the way at our present speed. That is, they could escape us once, but actually, this moon has greater mobility than they have. They were carried out by supply ships in pieces, and built up. They have motive power enough to turn around, and to straighten out their orbits so they won't tangle, but they can't flee. The main thing is that those Tefflans have courage. They will hope that the greater power of the forts may be able to do something against this moon, in the way of stopping it."

     As the Sunbeam swept up, the view Aarn had was, for the first time, as an outsider. The majesty of the scene came to him suddenly—the great dark sphere, rugged and cold in the sunlight, the dust motes of the Tefflan freighters daring to oppose it, and, further away, the great mass of Teff-ran.
     And now, away from the moon, he saw at last Ma-kanee. Deserted, uncontrolled, and uncontrollable, she was plunging straight for Teff-el. And Teff-el was already drawing her. Seas on Teff-el were rising, tides appearing, for already the swift-moving moon was within 1,000,000 miles of the planet There had been no attempts to divert it. That was frankly impossible. Further attempts to escape from Teff-el had been made, but there was a great ring now, of far-flung spy ships, each with a tremendous magnetic atmosphere thrown out, and the first touch of a ship attempting to escape made itself very evident And the fields overlapped.
     Minutes passed swiftly. And now the mass of Tefflan ships ahead, deserted, had separated to individuals. Minutes more passed, and at last the terrific process that had been going on within Ma-ran became evident A dull glow began to appear in the rocks below. It was growing swiftly— The first great Tefflan freighter plowed into Ma-ran. It was swallowed up like a pebble sinking into water—and with the same splashing of liquid. Almost instantly, a tremendous fountain of white-hot lava snapped out—and impaled a second freighter that was almost in line with the first. Both tumbled to the mad moon. A dozen were falling—a hundred— In seconds Ma-ran was sweeping on though a clear space.
     Every one of the great Tefflan ships had been absorbed. One of them had barely grazed the world, but been caught, and lay a pool of lighter, molten stuff on the rock pool. Great hot bubbles of air were oozing slowly up from the ships.
     "Velocity fell only one point. That was good enough. We reach Teff-ran now in thee quarters of an hour," said Aarn at last.

     The minutes dragged. The two great bodies seemed to move with infinite weary slowness. They seemed to know doom was upon them, and were going to it with the slow steadiness of men who welcomed doom, but accepted it philosophically and without hurry.
     Further and further the Sunbeam and her escort drew away, now. She raced ahead to a position in line with the final meeting, and watched as the two great balls of matter moved leisurely toward each other.
     Ma-ran looked like an orange drifting gently toward a grapefruit. Ma-ran was at last the smaller as she approached the end of her mad career. And beyond the great crescent of Teff-el, and the approaching disk of Ma-kanee, Tefflan ships swarmed up from Teff-ran—-and a swarm of heavy Magyan cruisers fell on them instantly, and cut them to pieces.
     Ma-ran bulged slowly, seemed to lengthen, and hastened her wild pace as she neared Teff-ran. Glowing red with the liberated energy of her coils, she stretched, became a blunt ended cylinder—and slowly became two great balls of red-hot matter as she began to turn visibly.
     "Gyroscopes went—the impact of the ships—" muttered
     Aarn uneasily. "That may have some unlooked-for effect—" Soundlessly, softly, with a sudden increased blaze of light, the two masses met, and spattered. Ma-ran coalesced with Teff-ran, and stopped. Tell-ran split. Slowly, majestically, they saw chasms open and run about the world. The sides fell away, and kept on going. The second half of Maran struck, and spread like a drop of melted lead on a hard surface—and the slipping sides of Teff-ran were snared, and melted in the flaming blue-white heat of the collision. In a quarter of an hour both bodies were one, and the mass was white-hot, flames spurting out angrily.

     Hours passed, as Aarn hung grimly beside the glowing mass. Finally he was satisfied with his observations, and made his calculations. "Six hours. Ma-kanee will get there in about six hours, two minutes and thirty seconds. This will get there at almost the same time. My calculations aren't quite accurate. I can't allow for the displacement of Tell-el for one thing."
     The new mass was dropping. Slowly—steadily. Wildly, small ships were shooting up from Teff-el, vindictively heading toward a cruiser or battleship with all its power, hoping to smash through the great wall even as a pilot died. They flamed briefly in a great transpon beam, and died— unsuccessful.
     Ma-kanee moved steadily downward. Tefflans were out on the surface of the planet, black masses of them, moving and surging, as they watched the two great bodies falling out of the skies on two exactly opposite sides.

     Three hours. Four hours. Five hours. The heat of the new mass, glowing red, had driven the black masses to other parts of the world. Cracks were appearing in Tell-el now. The new mass was only slightly distorted.
     "Tell-el's gravitational field declines slowly in strength— mass is so great—doesn't pull the near side much harder than the far side, so they don't fall apart, as Ma-ran did." But Tell-el began to fall apart. Great cracks appeared, smoke began to curl up, and over the great cavern system of Cantak, the ground sank suddenly, and an abrupt fault line appeared that sectioned the city with the precision of a knife. And slowly Tell-el turned under the baleful glare of the new, red-hot menace.
     Five hours and a half. The red-hot mass was nearing the outer fringes of the atmosphere. It was falling swiftly, now, still circling the planet a bit, so that its contact would not be a center blow, but a gouging scrape. An entire fleet of battleships was pulling at it now with traction beams, but there was practically no effect. The mass was too great, the beams almost totally useless.
     At the end of six hours, Ma-kanee entered the atmosphere. The atmosphere instantly compressed under it, a great bubble of air, and simultaneously, for the thee seconds it took the planet to traverse the atmosphere, everything beneath that place was compressed under a stupendous air pressure. It mounted like a solid wave; the air could not move away in time— Ma-ran-Tell-ran struck the other side. The atmosphere flamed below, and the planet caught fire from the terrible, glowing coal. Almost simultaneously, with a precision that was astounding, two bodies struck Tell-el.

     And the planet burst like a rotten tomato. Spurts of liquid stuff shot suddenly out of mighty chasms. Bursts that were cold, and solidified instantaneously into weird shafts of solid, grainless, incredible rock. Jets of rock, then great sections of rock, then a great jet of flying, gleaming metal, that squirted out like water from a hose, and solidified as the rock had, and in a bar ten miles through and a hundred and fifty long.
     And then only parts, and broken splinters that began to stop flying apart, remained. They were glowing, and some of them struck, and stuck together, and the force of their striking made them glow more, and cemented them. All three bodies were utterly destroyed, but the heat of Ma-ran-Tell-ran remained, and seemed to act as a binding agent.

     "Well—the ancient enemy is gone. Destroyed after some forty thousand years of trying."
     "And Tell-el is destroyed."
     "But while Tefflans can never reform, Teff-el is already reforming. See how the parts are falling together. It will be centuries, milleniums, before it is a planet again. But Tell-el is not destroyed. An incident in its life has taken place." Aarn gazed at the planet's distintegrating parts.

From THE MIGHTIEST MACHINE by John W. Campbell jr. (1934)

(ed note: in the LENSMAN universe, they have gadgets called "Bergenholms." These allow faster-than-light travel by removing a object's inertia. Small units can make a space-suited person inertialess. Medium units are for starships. And arrays of titanic units can make entire planets move faster than light.

All real-world object have a velocity, called a "intrinsic velocity" in the LENSMAN novels. Once the Bergenholm is turned on, the intrinsic velocity temporarily vanishes. The object can be moved FTL or remain motionless. The important point is, when the Bergenholm is turned off, the intrinsic velocity suddenly reappears.

As the scene opens, protagoinist Gray Lensman Kimball Kinnision is walking with Port Admiral Haynes.)

      "QX, Kim?" the Port Admiral asked. He was accompanying the Gray Lensman on a last tour of inspection.
     "Fine, chief. Couldn't be better—thanks a lot."
     "Sure you're non-ferrous yourself?"
     "Absolutely. Not even an iron nail in my shoes."
     "What is it, then? You look worried. Want something expensive?"
     "You hit the thumb, Admiral, right on the nail. But it's not only expensive—we may never have any use for it."
     "Better build it, anyway. Then if you want it you'll have it, and if you don't want it we can always use it for something. What is it?"
     "A nut-cracker. There are a lot of cold planets around, aren't there, that aren't good for anything?"
     "Thousands of them—millions."
     "The Medonians put Bergenholms on their planet and flew it from Lundmark's Nebula to here in a few weeks. Why wouldn't it be a sound idea to have the planetographers pick out a couple of useless worlds which, at some points in their orbits, have diametrically opposite velocities, to within a degree or two?"
     "You've got something there, my boy. Will do. Very much worth having, just for its own sake, even if we never have any use for it. Anything else?"
     "Not a thing in the universe. Clear ether, chief!"

(ed note: the valiant Lensmen and the starship armada of the Galactic Patrol have discovered the location of the dread planet Jarnevon, the capital planet of the evil Boskone empire {or so they think, but I digress} There the sinister alien Eich lead by Eichmil have been busy fortifying it strong enough to repel any attack)

     Into the Second Galaxy the scarcely diminished armada of the Patrol hurtled—to Jarnevon's solar system—around it. Once again the crimson sheathing of Civilization's messengers almost disappeared in blinding coruscance as the outlying fortresses unleashed their mighty weapons; once again a few ships, subjected to such concentrations of force as to overload their equipment, were lost; but this conflict, though savage in its intensity, was brief. Nothing mobile could withstand for long the utterly hellish energies of the primaries, and soon the armored planetoids, too, ceased to be.

     "Maneuver fifty-nine—hipe!" and Grand Fleet closed in upon dark Jarnevon.
     "Sixty!" It rolled in space, forming an immense cylinder; the doomed planet the mid-point of its axis.
     "Sixty-one!" Tractors and pressors leaped out from ship to ship and from ship to shore.
     The Patrolmen did not know whether or not the scientists of the Eich could render their planet inertialess, and now it made no difference. Planet and fleet were for the time being one rigid system.
     "Sixty-two—Blast!" And against the world-girdling battlements of Jarnevon there flamed out in all their appalling might the dreadful beams against which the defensive screens of battleships and of mobile citadels alike had been so pitifully inadequate.
     But these which they were attacking now were not the limited installations of a mobile structure.

     The Eich had at their command all the resources of a galaxy. Their generators and conductors could be of any desired number and size. Hence Eichmil, in view of prior happenings, had strengthened Jarnevon's defenses to a point which certain of his fellows derided as being beyond the bounds of sanity or reason.
     Now those unthinkably powerful screens were being tested to the utmost.
     Bolt after bolt of quasi-solid lightning struck against them, spitting mile-long sparks in baffled fury as they raged to ground. Plain and encased in Q-type helices they came: biting, tearing, gouging. Often and often, under the thrust of half a dozen at once, local failures appeared; but these were only momentary and even the newly devised shells of the Patrol's projectors could not stand the load long enough to penetrate effectively Boskone's indescribably capable defenses.
     Nor were Jarnevon's offensive weapons less capable.
     Rods, cones, planes, and shears of pure force bored, cut, stabbed, and slashed. Bombs and dirigible torpedoes charged to the skin with duodec sought out the red-cloaked ships. Beams, sheathed against atmosphere in Q-type helices, crashed against and through their armoring screens; beams of an intensity almost to rival that of the Patrol's primary weapons and of a hundred times their effective aperture. And not singly did those beams come. Eight, ten, twelve at once they clung to and demolished dreadnought after dreadnought of the Expeditionary Force.
     Eichmil was well content. "We can hold them and we are burning them down," he gloated. "Let them loose their negative-matter bombs! Since they are burning out projectors they cannot keep this up indefinitely. We will blast them out of space!"

     He was wrong. Grand Fleet did not stay there long enough to suffer serious losses. For even while the cylinder was forming Kinnison was in rapid but careful consultation with Thorndyke, checking intrinsic velocities, directons, and speeds. "QX, Verne, cut!" be yelled.
     Two planets, one well within each end of the combat cylinder, went inert at the word; resuming instantaneously their diametrically opposed intrinsic velocities of some thirty miles per second. And it was these two very ordinary, but utterly irresistible planets, instead of the negative-matter bombs with which the Eich were prepared to cope, which hurtled then along the axis of the immense tube of warships toward Jarnevon. (the nut-cracker) Whether or not the Eich could make their planet inertialess has never been found out. Free (inertialess) or inert, the end would have been the same. (The tube of galactic patrol warships are using tractor beams on the planet Jarnevon to prevent it from becoming inertialess and running away)
     "Every Y14M officer of every ship of the Patrol, attention!" Haynes ordered. "Don't get all tensed up. Take it easy, there's lots of time. Any time within a second after I give the word will be p-l-e-n-t-y o-f t-i-m-e... CUT!"
     The two worlds rushed together, doomed Jarnevon squarely between them. (an inertialess object cannot be harmed unless it is either anchored by a tractor beam, or if the damage is applied equally on opposite sides. That's why the nut cracker needs two planets)

     Haynes snapped out his order as the three were within two seconds of contact; and as he spoke all the pressors and all the tractors were released. The ships of the Patrol were already free (interialess)—none had been inert since leaving Jalte's ex-planet—and thus could not be harmed by flying debris.
     The planets touched. They coalesced, squishingly at first, the encircling warships drifting lightly away before a cosmically violent blast of superheated atmosphere.
     Jarnevon burst open, all the way around, and spattered; billions upon billions of tons of hot core-magma being hurled afar in gouts and streamers. The two planets, crashing through what had been a world, met, crunched, crushed together in all the unimaginable momentum of their masses and velocities.
     They subsided, crashingly. Not merely mountains, but entire halves of worlds disrupted and fell, in such Gargantuan paroxysms as the eye of man had never elsewhere beheld. And every motion generated heat. The kinetic energy of translation of two worlds became heat.
     Heat added to heat, piling up ragingly, frantically, unable to escape!
     The masses, still falling upon and through and past themselves and each other melted—boiled—vaporized incandescently. The entire mass, the mass of three fused worlds, began to equilibrate; growing hotter and hotter as more and more of its terrific motion was converted into pure heat. Hotter! Hotter! HOTTER!
     And as the Grand Fleet of the Galactic Patrol blasted through intergalactic space toward the First Galaxy and home, there glowed behind it a new, small, comparatively cool, and probably short-lived companion to an old and long-established star.

From GRAY LENSMAN by E. E. "Doc" Smith (1939)

Nicoll-Dyson Laser

if your budding "Weakly Godlike civilization" wants to graduate to Kardashev Type II, they have to harness all of the power available from a single star. Presumably the primary around which their homeworld orbits. The obvious technique is to surround the entire blasted star with solar power collectors so not a single solar photon wastefully escapes into deep space. The concept was invented by Olaf Stapledon in Star Maker (1937) and later popularized by Freeman Dyson in his 1960 paper "Search for Artificial Stellar Sources of Infrared Radiation" (abstract). Due to the second law of thermodynamics some of the power is going to show up as waste heat, making the "Dyson Sphere" resemble a red giant star. If astronomers do not look closely they may dismiss an observation of an alien megastructure as "just another boring red giant." Naturally science fiction authors fell in love with the concept so there is no shortage of examples in the literature.

But now that your ultra-civilization has access to around 400 yottawatts of power, what are you going to do with it?

Noted science fiction personage James Davis Nicoll had the answer. He brainstormed the concept of the dreaded Nicoll-Dyson Laser. Take the most practical variant, the so-called Dyson Swarm. Equip each of the swarm satellites with a phased array laser. Now you can emit a planet-frying death ray capable of ending all life on any world within a range of anywhere in the Local Group of Galaxies. Timelag is going to be a huge issue, but anyone who can build a Dyson swarm ought to be able to deal with it.

Naturally, as is always the case with any arms race, things get complicated if a second civilization builds one of these planet-pasteurizers. Or several thousand for that matter. Here on Terra we reacted to a similar situation with the doctrine of Mutual Assured Destruction. I'm sure the ultra-civilizations will cosmically sophisticated interlocking strategies far beyond our mental keen.

Such a beam does have non-military applications. For instance it can turn a humble laser-sail spacecraft into a relativistic starship.



Large time-domain surveys, when of sufficient scale, provide a greatly increased probability of detecting rare and, in many cases, unexpected events. Indeed, it is these unpredicted and previously unobserved objects that can lead to some of the greatest leaps in our understanding of the cosmos. The events that may be monitored include not only those that help contribute to our understanding of sources astrophysical variability, but may also extend to the discovery and characterization of civilizations comprised of other sentient lifeforms in the universe. In this paper we examine if the Large Synoptic Survey Telescope (LSST) will have the ability to detect the immediate and short-term effects of a concave dish composite beam superlaser being fired at an Earth analog from an alien megastructure.

III. Blast Modeling

     We investigate the activity and immediate aftermath of a planet-destroying laser blast with a series of approximations. We consider our target to be an Earth-analog, and so we use the properties in Table 1 for this planet, with values from Kite et al. (2009). We additionally use approximations of the average temperature of the core and mantle as 6000K and 1270K, respectively. Previous work has already examined the question of the energy needed to destroy a planet in this way, and we use their value of 2 × 1032 J in order to destroy an Earth-like planet (Boulderstone et al., 2011). However, it would not be realistic to treat the superweapon as fully efficient, and so we use values based off of nuclear explosions, where 50% of the energy goes into the kinetic energy of the planet, 35% into thermal radiation that raises the temperature of the planetary material, and 15% into an immediate, short-duration flash of electromagnetic radiation2. The observable energy from the explosion then comes from two components, the immediate release of energy during the explosion (what we refer to as the ’flash’) and the long-term thermal radiation from the debris of the planet (what we refer to as the ’remnant’). For the flash, we treat this as a blackbody with a surface of the Earth that will release all of the energy of this component in 2 seconds, or the equivalent of blackbody radiation for a surface at 106 K. We consider the debris of the planet to be well-mixed and be of a single temperature, and when this is calculated for the total energy, we find it to be a blackbody with a temperature of 29,000K. As this is occurring while the planet is being destroyed, the radius will be increasing, however as the escape velocity is 11 km/s we treat this object as consistent with earth-sized for the immediate aftermath. A more time-dependent examination would require accounting for the debris cloud growing in size, as well as the cooling of the debris (a time scale on order of 100 days if approximated as linear cooling) and changes to the optical depth of the debris cloud.

Table 1: Earth Properties
Earth mass5.97 × 1024kg
Earth radius6.37 × 106m
Core mass fraction0.325
Specific heat capacity, mantle914J K-1 kg-1
Specific heat capacity, core800J K-1 kg-1

     We show the blackbody curves for the flash and the remnant in Figure 2. We also include a blackbody curve for a Sun-like star at 5800K for comparison. We then convolve each of these blackbody curves with the filter throughputs for LSST. Unsurprisingly considering the high temperatures involved, we see that the most significant contributions from both the flash and the remnant will occur in the bluer bands. We treat the solar-mass star as our reference for calibrating the absolute magnitudes by using the method for determining the absolute magnitude in each band using the method that was outlined in Lund et al. (2015). We then compare the total flux in each bandpass for the Sun and for the flash and remnant in order to get relative magnitudes, followed by absolute magnitudes. An important consideration here is that the radius of the planet must be included in these calculations, and so the remnant is a close analogue of a white dwarf in radius and temperature. The absolute magnitudes that we determine are listed in Table 2. It becomes readily apparent that the remnant is generally no more than 1% of the brightness of a solar-mass star, and the flash is only brighter than a solar-mass star in the u band.

Table 2: Absolute Magnitudes

     These results are even more constraining than they may appear at first glance. The simulated flash duration is 2 seconds, however LSST will have exposures that are 15 seconds in duration. To correctly get the measured apparent magnitude, this difference in duration has to be accounted for, and the flash will look on order of 2 magnitudes fainter in the 15-second exposures of LSST, meaning that it will be slightly fainter than the star. As an inhabited Earth-analog planet (and, therefore, any planet likely worth destroying) would be expected to be around a solar-mass star, the light from the flash and remnant would have to be of considerable brightness with respect to the host star to be observed, and it does not appear that this is the case.

     There are, however, three scenarios that may result in the destruction event still being detectable. The first is if the star and planet are close enough to our Solar System that the planet’s destruction can be angularly resolved. Given that LSST will saturate at 16th magnitude, however, it seems extremely unlikely that any geometry exists where this would be possible. The second is if the planet is orbiting a smaller star. A red dwarf, for example, will be several magnitudes fainter, particularly on the bluer end of the LSST filter set. In this case, the flash, and possibly the remnant, will be brighter than the host star. While red dwarfs have not been the typical stars searched for planets in the past, there is no reason to think that an inhabited planet could not orbit around a red dwarf. Finally, the flash in the u band is still brighter than a solar mass star if it is observed instantaneously. In the case of LSST or other survey, this could also be accomplished by having a shorter exposure time, and so an exposure of 2-3 seconds would mean that any flash from a planetary explosion will be significantly brighter than the host star. In the case of LSST, however, the costs of this change to the observing schedule greatly outweigh this benefit as it would significantly curtail the observations that LSST will be able to make of fainter objects.


      The power of a collimated beam is limited by the focus of the beam when it reaches a distant target. One way to improve this focus is to increase the effective aperture of the emitter; a very large object, such as a Dyson Swarm, represents a very large effective aperture if it is used to emit such a beam.
     Dyson Swarms collect considerable amounts of energy from the stars they contain; if some of that energy can be stored, then directed towards a target in a different planetary system, considerable damage can result. In practice the outermost elements of the swarm, or the outer surface of a dynamically supported Dyson Shell (if present) become a phased array emitter. This allows a powerful beam to be focused on a distant target in another planetary system. This concept was first suggested by James Nicoll in the Information Age, and is known as a Nicoll-Dyson Beam for this reason.
     Nicoll-Dyson beams are routinely used to propel laser-sail craft at interstellar distances, and have been used to send messages to distant locations. Several messages have been sent by Nicoll-Dyson arrays to locations outside the Terragen Sphere, particularly to the closest High-energy emitting civilisations which have been detected in the Milky Way galaxy.
     Nicoll-Dyson arrays can also be used as weapons; severe damage can be inflicted on a planet's surface or on a megastructure at great distances. They have, however, rarely been used destructively; a number of beams were fired during the Oracle War, for instance, but they are regarded as weapons of last resort. If a beam is fired, this results in significant destruction in a distant system many years later — during the intervening period wars may have ended, treaties may have been signed, and the political landscape may have changed- but still the beam is on its way and cannot be recalled.
     Using powerful telescopes including the Argus Array, evidence of high-energy conflict has been observed in several distant galaxies; the use of Nicoll-Dyson beams has been confirmed in a number of cases, and is suspected in others.
     There are today many Dyson swarms and similar constructs in the Terragen Sphere, many of which are not part of the Sephirotic Empires such as those built by the Panvirtuality and the Efficiency Maximisation Paradigm. If interstellar relations ever decay to the point where Nicoll-Dyson beams are used en masse, the Orion's Arm Civilisation could be damaged or even destroyed in a very short time.
     Some commentators relate this to the mystery of the Great Toposophic Filter and the disappearance of so many xenosophont empires in the past.

From NICOLL-DYSON BEAMS by Steve Bowers (2009)


In the novel Ringworld, our heroes are exploring the eponymous megastructure. At one point their ship is moving on a vector close to a collision course with the Ring. That's when they find out the hard way that the Ringworld has a meteor defense system. A large X-ray laser fires upon their ship. They only survive because the ship is equipped with a stasis field for defense. Later, Louis Wu figures that the x-ray laser is mounted on the shadow squares.

He's wrong.)

      From a thousand miles up, one could see a long way before the blanket of air blocked the view. And for most of that distance, there wasn't a single island! The contours of sea bottom showed, and some of that was shallow enough. But the only islands were far behind, and those had probably been underwater peaks before Fist-of-God distorted the land.
     There were storms. One looked in vain for the spiral patterns that meant hurricane and typhoon. But there were cloud patterns that looked like rivers in the air. As you watched them, they moved: even from this height, they moved.
     The kzinti who dared that vastness had not been cowards, and those who returned had not been fools. That pattern of islands on the starboard horizon — you had to squint to be sure it was really there — must be the Map of Earth. And it was lost in all that blue.

     A cool, precise contralto voice eased into his thoughts. (an alien Puppeteer named Hindmost said) “Louis? I have reduced our maximum velocity to four miles per second.”
     “Okay.” Four, five — who cared?
     “Louis, where did you say the meteor defense was located?”
     Something in the puppeteer's tone ... “I didn't say. I don't know.”
     “The shadow squares, you said. You're on record. It must be the shadow squares if the meteor defense can't guard the Ringworld's underside.” No overtones, no emotion showing in that voice.
     “Do I gather I was wrong?”

     “Now, pay attention, Louis. As we passed four point four miles per second, the sun flared. I have it on visual record. We didn't see it because of the flare shielding. The sun extruded a jet of plasma some millions of miles long. It is difficult to observe because it came straight at us. It did not arch over in the sun's magnetic field, as flares commonly do.”
     “That was no solar flare that hit us.”
     “The flare stretched out several million miles over a period of twenty minutes. Then it lased in violet.”
     “Oh my God.”
     “A gas laser on a very large scale. The earth still glows where the beam fell. I estimate that it covered a region ten kilometers across: not an especially tight beam, but it would not normally need to be. With even moderate efficiency, a flare that large would power a gas laser beam at three times ten to the twenty-seventh power ergs per second (3×1020 joules/sec), for on the order of an hour (total 1.08×1024 joules or about 3 dinosaur-killer asteroids).”

     “Give me a minute. Hindmost, that is one impressive weapon.” It hit him, then: the secret of the Ringworld engineers. “That's why they felt safe. That's why they could build a Ringworld. They could hold off any kind of invasion. They had a laser weapon bigger than worlds, bigger than the Earth-Moon system, bigger than ... Hindmost? I think I'm going to faint.”
     “Louis, we don't have time for that.”
     “What caused it? Something caused the sun to jet plasma. Magnetic, it has to be magnetic. Could it be one function of the shadow squares?”
     “I wouldn't think so. Cameras record that the shadow square ring moved aside to allow the beam to pass, and constricted elsewhere, presumably to protect the land from increased insolation. We cannot assume that this same shadow-square ring was manipulating the photosphere magnetically. An intelligent engineer would design two separate systems.”

(ed note:the magnetic system is a series of titanic superconducting magnets embedded in the Ringworld floor)

From THE RINGWORLD ENGINEERS by Larry Niven (1979)

Cirys superzorcher (n.): A hypothetical weapons system in which the various elements of a Cirys swarm (q.v.) are equipped to function as the radiative elements of a phased-array laser. Such an array, with an effective aperture equal to the diameter of the swarm, would theoretically be able to deliver a substantial portion of the total solar output of the contained star in a single beam against targets located at interstellar distances.

Occasional peaceful uses for such beams have been mooted, including laser sail propulsion (although it should be noted that there is little call for such craft on a larger scale than existing propulsion arrays – which have the advantage of being mobile – can handle, and the ability to build a laser-sail craft capable of surviving such propulsion is questionable), long-distance, including extragalactic, communications (a matter of great interest to the Elsewhere Society), and even remote power generation and delivery.

However, while condemned by Cirys Aendyr himself – who is said to have wept when this application of his concept was brought to his attention – the most common proposal is to use the Cirys superzorcher as the weapons system implied by its name. The ability to place so much power on target (a figure of the order of 108 exawatts for a Hearth-class star) across interstellar distances, capable of vaporizing lithic worlds and severely damaging gas giants and stars, is peculiarly attractive to certain types of mentality, especially when it is considered that the purely photonic beam of a superzorcher is substantially more difficult to detect than a typical RKV, and cannot be practically intercepted or recalled.

As such, while the Cirys superzorcher requires a high degree of technological advancement and autoindustrialism to produce (a potential currently limited to the Empire and certain other Core Markets) and is in any case a prohibited weapons system (classified as a Tier I star-killer under the Ley Accords), an informal consensus exists among the Presidium powers that the construction of such a device by any polity, within or without the Worlds, may be reasonably interpreted as notice of intent to commit gigacide, and as such is a legitimate cause for preemptive defense of the highest order.

– A Star Traveler’s Dictionary

Nova Bomb

When merely burning off a planet is not violent enough, pulp science fiction loves to turn the volume up to 11 with the Nova Bomb. None of this fooling around carpet bombing with nuclear weapons, just induce the primary star to explode and incinerate the entire enemy solar system. Use this when the alien species is so horribly dangerous that it absolutely, positively has to be exterminated 100% overnight. You will be sure none of the enemy species escapes (unless they have one of those pesky "jump-type" faster-than-light starships that are immune to your military blocade).


      “To start with, have you ever heard of Earth?”
     “Which one? There are a couple of planets in this sector by that name, and another one in near the Hub somewhere. I can’t say I know much about any of them.”
     “The Earth I'm talking about is the original one. Over in the Sirius sector. The birthplace of the human race, millions of years ago.”
     “You mean such a place actually exists? I thought it was nothing more than a legend, a myth for children." Zim shook his head in puzzlement, then took another long drink from the glass in front of him.
     “No, I assure you it isn’t a myth. Earth, old Earth, actually exists, and it is really the original home of mankind. Let me fill you in a little on the background.
     “As near as we can determine from the records, something like seventeen hundred years ago man was confined to that one system, Sol. Space travel had developed slowly, until the invention of the inertialess drive, which opened up the stars. Over the next several hundred years, the men of Earth went out, colonizing uninhabited planets and contacting other species.
     “That outward surge of explorers and colonists almost killed the home planet. The best of their young men left for the stars, never to return. The resources of the entire system were looted to build the many ships required, all in the hope that eventually the colonies would begin to ship back to the home system raw materials that Earth vitally needed. Earth wished to evolve into a governmental center of an interstellar empire. The member planets would provide the material goods while Earth provided the direction.
     “Unfortunately, it didn’t work out quite that way. A pattern emerged. A colony would be founded and it would take several generations to become self-sufficient. Once the colony developed to the point where it had sufficient materials to send the surplus off-planet, it began an expansion policy of its own, establishing daughter colonies rather than sending the surplus back to Earth.
     “The situation soon became intolerable for Earth, and the central government attempted to enforce its policy. The reaction was predictable: the colonies revolted. At first Earth countered with blockades and confiscation of shipping; but eventually she resorted to weapons, and the war was on.
     “Several of the older colonies formed a loose confederation and attacked Earth. They assumed that they were getting involved in nothing more than a police action, considering the state of Earth’s resources, but they forgot one very important fact. At that time, poor as she may have been in military-minded young men and the raw materials needed to support an interstellar war machine, Earth still had the greatest concentration of technical know-how and scientific development potential in the known universe.
     “The confederation of rebel planets ringed the Earth system—the Solar System—with warships, then bombed the colonies on the fourth planet to rubble as a demonstration of its powers. Then it sat back and waited, two years, for Earth’s surrender. When the reaction finally came it was nothing they could have expected. In those two years Earth developed weapons of such fantastic power that no colonial fleet, no matter how large, could stand against her ships. Unfortunately, Earth could not possibly maintain exclusive use of those new weapons. Ships were occasionally captured and their weapons copied. Scientists of the colonies also came up with some new weapons of their own, but Earth had a commanding lead. In no way could the Earth fleets be stopped—only slowed, dragging out the war. Then Earth came up with a weapon that has never been copied since.
     “Out of the laboratories of the home world came a bomb capable of exploding a sun! A nova bomb, that could erase every trace of life from a system and leave it completely uninhabitable. With that weapon the Earth government completely destroyed every one of the colonies that had made up the confederation, ringing the section of space around the Solar System with a swath of burned-out suns.
     “Over one hundred billion people died in that war. There’s no telling what eventually might have happened if the people of Earth, common citizens and government officials alike, hadn’t recoiled in horror at what was being done. The reaction destroyed the government that had planned to rule the stars; Earth, with the threat of the nova bomb to back her words, closed the space around her system, renouncing the stars forever. For twelve hundred years Earth has been all but completely cut off from that part of human civilization that eventually evolved into the Hub Federation. Not more than one ship a century has visited Earth, and as far as we know, in all that time only two Earth ships have ventured into the galaxy beyond the ring of dead stars.”
     “With the end of the war a tremendous religion revival swept over Earth. Science and technology weren’t eliminated, but they stagnated, and science was eventually replaced by mechanics. All the benefits of a highly technological society were kept, but advancement ended. Over the centuries, the religion was replaced by a philosophical orientation, that continued to develop until last year.
     “By Federation standards, the population Earth chooses to maintain is small; but even within a population measured in the hundreds of millions, a fairly large number are bound to be dissatisfied with the calm and unhurried pace of a contemplative society. Most of them found outlets for their energy in the mechanical trades, which allowed the society of thinkers to exist without material effort, and it was assumed that the social situation was stable.
     “Then, last year, one of the mechanics, actually a botanist, made a revolutionary discovery after he accidentally irradiated a culture of mutant bacteria he had discovered growing on some yeast cakes. He found a way to synthesize antiagathics.
     “Even after twelve hundred years, the memory of what they had done to those billions of colonists burned in the consciences of the men of Earth. With this discovery, the Earth government, sort of an ethical technocracy, saw a way to wipe out at least a part of their guilt and shame, Their leader—his title is President—and a few aides took one of their carefully preserved starships and came to the Hub to make arrangements for a scientific team to be sent to Earth. While the President was establishing relations with the Hub Federation, a major political change took place on Earth. In effect, the mechanics revolted and took over the government. This faction is led by a former computer design engineer who our psychology service has tentatively identified as a Messiah-type. He apparently plans to make Earth central ruling planet of the empire of man.”
     “And I suppose he has the nova bomb,” Zim commented quietly.
     “He has. When the original Earth government fell, every bomb in existence was dismantled and the components put into solar-impact orbit. Every set of plans, every textbook description, every thesis on the subject was confiscated and destroyed. And everyone who knew anything about the construction of the bomb was sworn to secrecy.”
     “After the fact, suppression of scientific advances seldom seems to work, though,” Zim commented.
     “It worked for twelve hundred years. And probably would have worked even longer, except that the University of Earth maintains a history data bank in which a complete description of the nova bomb lay forgotten. The leader of the revolt came across those plans, and researching the history of the use of the bomb probably triggered the Messiah complex in him. He started with the conviction that he was right, gained political support, and now he has revived the nova bomb as the weapon needed to achieve his ultimate goal. All that stands in his way is a technicality—his election to the presidency of Earth, an event he is sure to engineer before long.

From VOYAGE TO A FORGOTTEN SUN by Donald Pfeil (1975)

      Rolf came out of the ship, with Jommor and Tharanya. They began to walk across the plain, the fresh breeze lifting their hair and tugging at their garments.
     Banning's face contracted as though with some deep agony. He went on again, toward the Hammer. It towered up, reared high on a platform as big as Manhattan Island—or at least it seemed so, to Banning's dazed eyes. It was shaped in some ways like a cannon, and in others like—no, not like anything else. Like itself alone. There had only been one Hammer. And it was the first, the beginning, the experiment carried out in the lost and secret place where there was ample material for the Hammer to crush, from whence it could reach out to—
     A ladder led him up onto the platform, a ladder made of some wizard joining of ceramic and metal that would outlast the land it stood on. The platform, too, was built of a substance that had not weathered or corroded. A door of cerametal led inside, to a chamber underneath, and there were controls there, and mighty dynamos that drew power from the magnetic field of the planet itself. Banning said harshly to Sohmsei, “Keep them out."
     The Arraki looked at him—was it love and trust, or a loathing terror that showed in his eyes? Banning's own gaze was uncertain, his breath painful in his throat, his hands shaking like those of an old man with the palsy.
     Now, now! Which was it to be, the Old Empire and the throne of the Valkars, the banner blazened with the sunburst? Or surrender to the mercy of Tharanya and Jommor, not only himself but Rolf and Behrent and all the others?
     Banning put his hand on the breast of his tunic, and felt the symbol there, the sunburst bright with jewels. And suddenly he sprang forward in the silent room, toward the levers, the sealed imperishable mechanisms that held within them the coiled might of the Hammer.
     He remembered. He remembered the tradition handed down from father to son, and the things that were written in the ancient books among the archives. Ambition had burned them into his mind, and greed had fixed them there with an etching of its own strong acid. He remembered, and his hands worked fast. Presently he went out of the chamber and down the ladder, to where Jommor and Tharanya and Rolf were waiting with the two Arraki, five grim shapes at the end of the world. Rolf started to ask a question, and Banning said, “Wait."
     He looked up.
     From the colossal pointing finger of the Hammer, there leapt up a long lightning-stroke of sullen crimson light. A giant stroke that darted toward the yellow sun in the heavens, that flared and glared—and then was gone.
     There was nothing more.
     Banning felt his bones turn to water. He felt the horror of a supremely impious action. He had done a thing no man had done before—and be was afraid.
     Rolf turned toward him, his face wild and wondering. The others were staring puzzledly, disappointedly.
     "Then—it doesn't work?” said Rolf. “The Hammer—it does nothing—" Banning forced himself to speak. He did not look at Rolf, he was looking at the growing sunspot that had appeared on the yellow star, a blaze of greater brightness against the solar fires. His horror at himself was mounting.
     "It works, Rolf. Oh, God, it works—"
     "But what? What—"
     "The Hammer,” said Banning thickly, “is a hammer to shatter stars." They could not take that knowledge into their minds at once, it was too vast and awful. How could they, when his own mind had recoiled from it for all these terrible hours?
     He had to make them believe. Life or death hung upon that now.
     "A star,” he said painfully, “nearly any star—is potentially unstable. Its core a furnace of nuclear reactions, from which hydrogen has been mostly burned away. Around that core a massive shell of much cooler matter, high in hydrogen content. The trapped, outward-pushing energy of the central furnace keeps the cooler shell from collapsing in upon it."
     They listened, but their faces were blank, they could not understand and he must make them understand, or perish.
     Banning cried, “The Hammer projects a tap-beam—a mere thread compared to stellar mass, but enough to let that pushing energy of the nuclear core drain out to the surface. And without that push of radiation to hold out the shell—"
     Understanding, an awful understanding, was coming into Jommor's face. “The shell would collapse in upon the core,” he whispered.
     "Yes. Yes—and you know what the result is when that happens." Jommor's lips moved stiffly. “The cooler shell collapsing into the super-hot core—it's the cause of a nova—"
     "Nova?” That, at least Rolf could comprehend, and the knowledge struck a stunned look into his eyes.
     “The Hammer could make any star a nova?"

From STARMAN COME HOME by Edmond Hamilton (1954)

      The captain watched him speculatively. It struck York that were Hull Earth-born, he undoubtedly would be commanding an N-ship instead of a destroyer at the ragged fringes of space. True, the Draco carried long-range lasers, cobalt warheads, nucleonic bolts—all the conventional weapons—but not the dread N-bomb. By unwritten Empire law, only a born Earthling could command an N-ship. In short, the Draco couldn’t nova a sun.
     “Empire Intelligence.” Hull murmured the words quietly, yet somehow his voice betrayed doubt and wonder.
     “That is in confidence.” York contemplated the captain calmly. If the Empire’s galactic Navy were the instrument that kept over two thousand inhabited planets living in controlled harmony, it was the shadowy Empire Intelligence that nipped discord in the bud, kept the Empire intact. Without E.I., as it was called, the restless worlds of the Alphan suns would long since have challenged the Empire’s yoke, N-bomb or no N-bomb. Prince Li-Hu of the Alphan world Shan-Hai, who traced his ancestry back in an unbroken line to the emperors of the ancient Earth nation of China, had both feet planted squarely in the middle of the captain’s present emergency, even though Hull didn’t know that.
     “Authority that’s residual in a card?” snapped Hull. “How do I know that you’re Daniel York?”
     “By my knowledge.”
     “What knowledge?”
     “Your rush to push the Draco into space,” replied York. “You were slated to remain on Upi for another week. Now you’re rushing under secret orders.”
     “Keep talking, Mr. York, and you might wind up on a detention world.”
     “No, thanks.” York leaned forward and said deliberately, “The N-bomb cruiser Rigel is missing. First Level picked up a distress call from the region of Ophiucus. That was two days ago. Since then there hasn’t been a word. Lost—one N-cruiser. That’s your emergency.”
     “That knowledge is restricted to First Level—”
     “And to the captain of the Draco because you happen to be nearest the scene,” cut in York.
     “You know too much. Tell me, Mr. York, just who are you?”
     York grinned and said, “E.I.”
     “I don’t know that.”
     “You also don’t know that the Rigel was sabotaged,” York boldly challenged.
     “No …” Hull breathed the word slowly, a startled look crossing his face. Abruptly he straightened. “There hasn’t been a case of sabotage in over three centuries.”
     “The record just fell,” declared York.
     “I can’t believe that!”
     “The Rigel was sabotaged—captured, if you will—and forced to land somewhere in the Ophiucus region for the purpose of stealing the N-bomb. And Prince Li-Hu is in back of it, Captain. Make no mistake about that.”
     “I would have agreed with you last week,” York said calmly, “but that’s last week.” He spread his hands. “The Empire is maintained only through sole possession of the N-bomb. Its existence—monopoly, if you will—is the Empire’s guarantee of solidarity. No world is apt to rebel against a power which could nova its sun, Captain.”
     “You don’t sound particularly sympathetic.”
     “Practical,” answered York. “We live by the sword, but we don’t want to perish by it.”
     “What you say amounts to an accusation, York.”
     “It does,” he answered.
     “No planetary government would dare use the bomb. That’s if they could steal it, which they couldn’t.”
     “Correct, but neither would the Empire use it—not if the ability to retaliate existed.” York heard the sound of closing hatches and restrained his impatience. “Once the bomb is out of Empire hands, its power is negated. You can see what that means, Captain. With that fear removed, you’d see a dozen revolts overnight.”
     “I fail to see that, Mr. York.”
     “You are a military man, Captain. To you war means laser beams, nucleonic bolts, the burst of cobalt bombs.”
     Hull asked coldly, “What does it mean to you?”
     “Plotting, espionage, murder—men in high places conniving for power.” He held the captain’s gaze. “A knife in the back can win or topple an empire as quickly as a cobalt bomb, and with far less mess. History’s filled with such fallen empires,” he finished.
     “You make a dramatic case of it,” the captain observed.
     “Dramatic? Presto”—York snapped his fingers—“and one N-cruiser is gone. Yes, I believe you might call it dramatic.”

From THE PROGRAMMED MAN by Jean Sutton and Jeff Sutton (1968)

It might also be just as well to restrict sharply the technical information the city passed out in this star system. If the Hamiltonians—or the Hruntans—suddenly blossomed out with Bethe blasters, field bombs, and the rest of the modern arsenal (or what had been modern the last time the city had been able to update its files, not quite a century ago), the police would be unhappy. They would also know whom to blame. It was comforting to know that nobody in the city knew how to build a Canceller, at least. Amalfi had a sudden disquieting mental picture of a mob of Hruntan barbarians swarming out of this system in spindizzy-powered ships, hijacking their way back to an anachronistic triumph, snuffing out stars like candle flames as they went.

From EARTHMAN, COME HOME by James Blish (1955)

The only exception to the general picture of Telesthetic star faring races as relatively temperate, pragmatic, and ultimately cooperative peoples is the Xenophobe Experience. In their manic incursions into Pan Sentient space, planting conversion triggers in stars to murder whole planetary populations, the Xenophobes severely strained the image of the Telesthetic as the pacific influence upon the wilder elements of any race. Seven billion sentients on Triplet were incinerated by induced nova because the crew of their Gate couldn't believe that the unidentifiable Star Force Tac-Shifting towards their sun was capable of such a hideous act.

It was, as they say "a pearl harbor" that mobilized the wrath of 280 billion sentients and sent the Combined Pan Sentient Star Wing to smash the Xenophobes back into their own Volume after the First Incursion. After the Second Incursion, the PSL forsook all temporizing and launched the Expedition of Punishment and Retribution into Xenophobe space. Thirty-seven Xeno systems were "purified" of that hateful life-form, using Conversion bombs, focused Heissen fields at lethal intensities, Rame killer swarms, and finally kilometer-by-kilometer extermination sweeps by Human / LChal-Dah Star Soldiers. The Xenophobe home system was reduced to a population of one billion, all of whom were Blanked and gene-washed. The planet was sealed with a standing discontinuity net tied to a conversion trigger orbiting the star.

The Star Gate called "The Lid" was placed in trans-system orbit to monitor the net, maintain the trigger, and to "pull the plug" should the Xenos ever so much as attempt to lift out of the atmosphere again. The Expedition took 1.7 Standard Years to complete at a cost in PSL life of 3.7 million battle deaths, 21 Teleships destroyed, 803 Telesthetics were permanently dysfunctional (Blanked). The Xenophobes lost 127 billion sentients, 98 Teleships destroyed via Telesthetically implanted conversion warheads, 34 Teleships destroyed by Rame Sacrifice Teams, 28 Gates destroyed by Rame Sacrifice Teams, 9 by Human/ LChal-Dah Star Soldier assault groups using low-energy approach. Eleven Xenophobe Teleships remain unaccounted for (assumed lost in fragmented randomization).

Total PSL civilian deaths in the First and Second lncursions:41.315 billion sentients.



After two and one-half centuries of generally pacific conduct and gradual terraforming of all the depicted star systems, the PSL (Pan-Sentient League) sphere was invaded by a rabid species known only as the "Xenophobes". They began inducing novas in PSL stars (causing them to explode) incinerating the inhabitants. Not knowing where they were coming from, and the thought pattern being so alien as to be largely undetectable, the PSL StarForces were forced to search the periphery of its Known Volume for the Xenophobe "base camp" StarGates. The Xenophobes were inhibited by smaller shifts due to unfamiliarity with the PSL Volume.


Scenario continues until all Xeno StarGates have been destroyed or all PSL Home Systems stars (Sol, Sigma Draconis, and 70 Ophiuchi) have gone nova. At that time, Victory is determined according to the number of Victory Points, the Player with the higher total winning.



After the First Incursion of the Xenophobes had been driven off by the PSL, a watchful peace ensued. Approximately 30 billion PSL sentients died in the First Incursion, creating a shortage of telesthetics and forcing a reduction in the number of PSL StarForces. 10 years after the First Incursion, the Xenophobes returned.


The Xenophobe murderers use the star of the system as a weapon. By planting a Conversion Trigger in the heart of the sun they cause it to nova (greatly accelerate its energy output) in order to scorch the orbiting planets and destroy all life. In order to perform this triggering successfully, the StarGate defending the system must be dealt with first. The following cases simulate this:

[31.51] Nova Inducement: In the Basic Game, if the Xenophobe Player has one or more StarForces present in the PSL LiteZulu (hexagon at a given altitude above the surface of the 3D strategic game map, each hex is 1 light-year in diameter) in which the StarGate has been eliminated (neutralized) he may cause the star to go nova in any Combat Segment following the elimination of the StarGate. One Xeno StarForce must be assigned to task of triggering the star, and it must be plotted to break-off in the Combat Segment in which the star is triggered. If it is randomized (by enemy weapons fire) before it can break-off, the star is not triggered. If it successfully breaks-off, the star is triggered and the StarGate is destroyed permanently. Remaining opposing StarForces may remain behind to fight (but the outcome is academic, since the system has been destroyed).

[31.52] Nova Inducement in the Advanced Game: In order to plant the Conversion Trigger in the star, at least one Xeno StarForce must spend an entire Tac- Turn in the star's MiniLiteZulu (3D hexagon on the tactical map. Each minihex is 1/3rd of a light-day in diameter or 0.0009 light-years). It must be in Stellar Mode (as opposed to Battle Mode) and assign half its TelePoints to the task of planting the trigger (which actually is completed in the Position Revelation Phase of that Tac-Turn).

If the Xeno StarForce is disrupted (or randomized) before that time (by hostile weapons fire), the trigger is not considered planted and the star will not go nova. The PSL StarGate must be in a disrupted (or neutralized) state during the planting of the trigger. In the Tac-Turn following the successful planting of the trigger, the Xeno StarForce must Tac-shift out of the MiniLiteZulu containing the star and attempt to execute a break-off maneuver in the Second Execution Phase. The star goes nova during the Combat Cast Segment of the First Execution Phase (After successful planting of the trigger) and any StarForces in the MiniLiteZulu with the star are destroyed in the Results Application Phase. Any remaining StarForces may still contest the LiteZulu but they may not enter the MiniLiteZulu containing the star. The StarGate is not permanently destroyed until the resolution of the Tactical Sequence.


For several thousand years, Green Companion of Antares had been known as a tempestuous stellar bastard, constantly filling all space around it with radiation clouds and fouling up communications. It had several dozen planets which could be very pleasant in the sun were calmed down somewhat, so the Hubley University extension at Antares Vert had been established in 6200 to seek ways of controlling the star. Shortly before the war, they found the first major advance of macro-mechanics, how to blow a star into a nova. It worked as well on stable, main-sequence stars as on the huge, wasteful monsters like Rigel, upon which it was demonstrated. The TOSS now realized that the League could seed their stars through Critter's Universe and blow them all to perdition before anything could be done. Hastily withdrawing their forces from the Gateway, the TOSS began cultivating good feelings with forced urgency.

From THE WARBOTS by Larry Todd (1968)

Orbital Fortress

The defenders remaining spaceborn assets will be in orbit around the planet. If the defender is fortunate enough to have a moon or two these can also be armed with defensive bases and weapons.

Orbital fortresses have far more punch than the equivalent combat spacecraft, kilogram for kilogram. This is because the spacecraft has to use part of its mass for propulsion, while the orbital fortress can use that mass allocation for more weapons instead. However orbital fortresses do have problems with heat radiators and supply.

Supporting the fortresses, the planet's orbit will probably be full of defensive assets such as small but deadly weapons designed to mission-kill invading spacecraft and any ortillery they drop. In the Strategic Defense Initiative, two concepts looked into were "Space-Based Interceptor" and "Brilliant Pebbles" (the latter were the heirs to "smart rocks")

When it comes to defending a space colony instead of a planet, you can attach weapons and defenses so the thing becomes sort of an orbital fortress that people live inside. On Babylon 5 this was called the "defense grid".

In Long Shot for Rosinante, Alexis Gilliland points out there are military implications. If you have several unarmed space colonies you will need a fleet of warships roving around to defend the colonies. If the colonies are then retrofitted with weapons so they can defend themselves, oh my! You suddenly have a spare fleet of warships that can be repurposed to military adventurism! Enemy colonies will become alarmed.

However the politicians of the nation which established the colonies may be unenthusiastic about the idea. For one thing it makes it harder to collect taxes from the colonies, since they can shoot at the tax collectors. It also makes it harder for the politicans to control the military, since the latter will be eager for some delicious military adventurism. Regardless of what those cowardly civilian politicans back home have to say.

The indispensable Future War Stories blog makes the point that there is a big difference between a Battle Station (orbital fortress) and a Military Space Station.

A battle station, mobile assault platform, or orbital fortress is basically a huge warship armed to the teeth that has no engine. It has lots of offensive weapons. Much like the Death Star from Star Wars, but used more to defend planets instead of blowing them up.

A military space station is a military base that just happens to be in orbit instead of on the ground. It is used to support troops, house spacecraft, administer logistical aid, and the like. Generally it only has defensive weapons, but may be protected by a space navy task force. They are much like the U.S. military bases located in the continental United States.


We who have grown up with the bomb can hardly imagine a world without the Sword of Damocles hanging over our heads by a thread. Strategic warfare has been dominated by offense for over 30 years.

Even though it might take 20-50 years, advances in space might swing the balance back toward defense. Here are some wild speculations, hopefully based on engineering realities.

Don’t be surprised if the Department of Defense picks up the slack in NASA funding of mass drivers and solar sails. A mass driver is just what you need to bring most of an asteroid to the vicinity of the Earth by throwing away part of the asteroid for reaction mass. Solar sails would bring them back piecemeal. A million-ton asteroid in high Earth orbit would solve a number of problems such as providing hardening for certain advanced weapons systems and their heat sinks.

"Hardening" is the capacity to take a beating and remain functional.

Heat sink" is an engineering term which can mean anything from a tiny clip on a transistor to the Mississippi river. It's whatever is used to get rid of waste heat. On Earth, waste heat is mostly carried off by water or air and eventually radiated from the vast area of the planet into the cold (three degrees above absolute zero) universe. Some of you may remember the story by Poul Anderson about a rogue planet (Satan) that was thawed out by a close pass near a star and then kept warm as it sailed back into the dark by industrial waste heat on a grand scale.

Getting rid of waste heat without a planet isn’t hard, but it isn't cheap either. Waste heat radiators are a major factor in the design of space industrial facilities, habitats, farms and military bases. For all of these, including, in the long run, military bases, the Stefan-Boltzman law relating temperature and radiation rate and the fact that people and their machines function best around “room temperature" implies that the radiator surface area will be about four square meters for every kilowatt of waste heat.

Military fact #1: in the size we need, waste heat radiators will be very large. Radiators must be filled with something (substitutes for wind and water) to carry the heat. For both physical and economic reasons radiators should have walls no thicker than required to contain the filling material.

Military fact #2: radiators are unavoidably fragile. Something both large and fragile would make a lousy military heat sink. Nobody can cheat on physical laws, but with an asteroid, you would be able (for a while) to use the "Alice's Restaurant" method of waste-heat disposal. (Alice lived in the belfry of a deserted church and put the garbage downstairs.) Two weapon systems, particle beams and lasers, have the potential to end the current offense-dominated Mexican stand-off known as "Mutual Assured Destruction," or MAD. Lasers are getting about $200 million per year development money in this country, and particle beams are believed to be better supported in the U.S.S.R.

Both particle beams and lasers are line of sight, speed of light weapons. This could make for some mighty short wars! They are very similar in needing millions of kilowatts of power and large heat sinks (because they are not very efficient) and both work better in space. Either method, with enough power behind it and a good enough aiming system, could make short work of ICBMs, submarine launched ballistic missiles and perhaps even bombers and cruise missiles, thereby eliminating all three of the U.S. "triad" at one stroke.

Skip for a moment the moral and geopolitical implications: how does an asteroid fit into this picture?

First, it's by far the easiest way to get a hardened site into space. Hardening is absolutely essential if the opposition has a similar installation. Otherwise, all the advantages go to "he who shoots first," a much worse situation than MAD. An actively defended fort could most likely stop missiles, but there is no way to shoot down a laser beam. However, you need not worry about lasers if you are inside a multimillion-ton asteroid. An MIT study some years ago concluded that even to slightly deflect an asteroid (e.g. Icarus) would take a lot of the very largest hydrogen bombs people make. A laser that could wipe out missiles would just blow little pock marks in the surface of an asteroid.

Second, to keep the laser cool you need a monster heat sink that a hostile laser won't cut to confetti. Radiators are just too vulnerable, (see above) so the waste heat will have to be stored till the war is over and that means an asteroidal sized mass to store the heat. Even if the laser gasses only make one pass through the laser and then are discharged into space, a substantial heat sink would be needed for the auxilliary equipment and such things as cooling the laser mirrors. For the same reason, all the energy to fight a war will have to be stored inside.

How much energy storage and heat sink capacity would be needed to fight a hypothetical war between the major powers with space-based lasers zapping all the missiles? Unless you complicate things by having the forts try to fight each other to the finish, a few gigawatt hours of beam energy is sufficient to wipe out the warhead delivery systems inventory of the entire world. Altogether there are less than 5000 ICBM's and submarine-launched ballistic missiles. Five gigawatt hours of beam energy would give a little less than a ton of explosive effect for each one. Because lasers are only about 20% efficient,* and allowing for some safety margin, energy storage might be ten times the beam energy and heat sink capacity about eight times the beam energy. To get a feel for this amount of energy in standard military terms, one gigawatt hour is equivalent to about 900 tons of TNT.

(*If you believe in higher efficiency, plug in your own numbers. Free electron lasers might reach 50%.)

The next question is how big an asteroid do you need in order to absorb, say, 40 gigawatt hours? A simple general rule is that a kilowatt second will heat a kilogram of rock about one degree C. Forty gigawatt hours is 14.4 x 109 kilowatts, which means this much energy would heat a million ton asteroid 14.4 degrees C. Thermal stress rather than absolute temperature rise may turn out to be a determining factor. To keep a fort ready, you keep it cold.

How would an asteroid fort be constructed that could take considerable pounding from lasers and missiles and still be able to zap ICBM's. The best type, to start, would be the solid nickel-iron variety found in science fiction stories. Unfortunately, that may be the only place to find them. The processes (hotly argued over) that formed these objects may have left fracture-prone weak zones of silicate material between large blocks of solid metal.

For iron asteroids with fracture zones of stony iron (lumps of iron mixed with rock) the first job will be some outside shaping followed by drilling a lot of holes through the asteroid and stringing it together with steel cables. This would probably work with any asteroid that had as much compressive strength as concrete.

Next, a maze of coolant channels would be drilled through the rock or iron. Iron would provide an advantage here because of its much better conductivity. Either rock or iron would be fairly easy to drill through, but a mixture would be more difficult. The laser, control system and power storage would be installed in cavities dug out of the center of the asteroid. My guess is that energy would be stored in flywheels or fuel cells. Primary power could be nuclear reactors or solar cells. Either the solar cells or heat radiators for the reactor would hang outside and you could expect them to be shot off right at the start of any action.

Lastly, the surface would be covered many meters deep with foamed metal to soak up energy from a close nuclear blast or a short laser pulse. Much of the energy from a nuclear blast in space arrives in the form of X-rays which heat the outside surface so fast that a shock wave causes pieces to fly off the inside wall (spallation). A substantial layer of something crushable takes care of this problem.

To track targets and control the aiming of the laser would require a dispersed phased array radar too spread out to knock out with missiles and too hard to take out quickly with a laser. Verification of target destruction and some tracking would be done optically or with infrared. The radar information would be transmitted over redundant channels to a very large, fast computer in the fort. This part is within the capacity of present day electronics.

Like the Death Star in Star Wars, a space fort would have a vulnerable spot. It could be knocked out by a beam that went in where its beam went out. To protect its “Achilles Heel" each one might be surrounded with a flotilla of actively controlled mirrors: a fort could take bank shots with a diffuse beam at the other forts, while avoiding looking directly at them. (A fully focused beam would be so energetic that it would not be reflected, but would just vaporize the bank-shot mirror. The bank-shot mirror would refocus the beam more tightly.)

There are many counter and counter-counter strategies including shooting lasers at the forts from the ground, trying to disable all the enemy's reflector flotilla, hardening the bank shot reflectors, and slinging rocks at the forts. None look very promising. Attacking from the ground with lasers looks like it would bankrupt the country that tried it.

Why? Missiles can be destroyed by the energy equivalent of a few kilograms of TNT. A bomber can be wrecked by the equivalent of a few hundred kilograms. But an asteroid would take hundreds of megatons of TNT or millions of gigawatt hours. Not counting laser inefficiency, or the cost of the laser, a million gigawatt hours at one cent per kWh is $100 billion. The lasers would cost a thousand to a million times this much. Hitting a fort with another asteroid would be effective, but would take years due to celestial mechanics considerations. Also, it isn't easy to do secretly. Even the slightest ability of a fort to dodge would make it vastly more difficult to hit.

And a shoot-out between forts of similar size looks to be a real idiot's delight: “this hurts me more than you" really applies to space forts because four times as much energy as is in the laser beam must be dumped internally, and the vast majority of energy delivered by the laser beam would be reradiated; the remainder would do very little heating. Even with limitless energy available, an attacker using lasers would cook itself long before doing much damage to a target fort.

For the same reason, a small amount of hardening would protect a ground installation from attack by a space-based laser. The total energy available within a fort due to laser energy storage is equivalent to only a few hundred to a few thousand tons of TNT.

Schemes to put forts out of action would be less attractive if many countries owned several forts each. If only two countries owned one fort each, a fort being put out of action would leave the owner of that fort in a very bad fix, exposed to ICBM's without any way to retaliate. If a dozen countries owned several forts each, there would be very little point in keeping ICBM's active at all. Of course, some countries would still keep ICBM's around just to force others to spend money on defense. (A major effect of the U.S. bomber fleet is to force the U.S.S.R. to spend a bundle on air defense—money that would otherwise be spent on other military projects.)

Whether or not asteroid forts and very large lasers in space would have a major effect on ground warfare is a good question. I am sure tanks would be much more difficult to take out of action than cruise missiles or bombers. However, if the problems of shooting down through the atmosphere can be solved, it might accelerate the current trend, started by precision guided munitions, to quickly remove large, expensive objects from the battlefield. I don't think the troops will go back to swords and horses, but automatic rifles, hand-held rocket launchers and motorcycles might be the most expensive items practical on a year 2000 battlefield.

May the force be with you!


Belchar’s World, Battle of: The Battle of Belchar’s World – a term referring to Fourth Belchar’s, 6882 – while in most respects another of the minor squabbles endemic to the Shadow Systems, has attained a degree of fame through being taught in the majority of the Worlds’ military academies as an example of the problems that can result from close-orbital combat operations.

The battle was the last gasp of the Vile-Born Imperium’s attempted invasion of the freesoil Belchar’s World (Torgu Wilds). While a technical victory for the organized Vile-Born fleet against the irregular forces of the freesoil world, the majority of the battle took place in mid-to-low planetary orbit, resulting in extensive destruction of not only military craft, but also of civilian stations and other elements of orbital infrastructure – most significantly, the self-destruction of the orbital starport twenty-two minutes after Vile-Born boarding parties forced the docking bays.

Inevitably, the introduction of so much debris into this area caused a full-blown cascade catastrophe, resulting in mutual disengagement. After a number of attempts to penetrate the cascade zone with landing craft, all of which were lost with all hands, the Vile-Born fleet retreated from the system in good order.

(This was not to last: much of the fleet was subsequently destroyed in the Osquina Mutiny, instigated by a coalition of sub-admirals who preferred not to return to Vileheim and suffer the traditional sky-bath prescribed for failed naval officers.)

Winchell Chung: Would the "traditional sky bath prescribed for failed naval officers" include sky-diving without a parachute?

Alistair Young: Different kind, in this case: the Torgu Wilds are located uncomfortably close to a stellar nursery and other things contributing to an unpleasant radiation environment. The "sky-bath" involves being staked out under the open sky until the rads get you.

From PYRRHIC by Alistair Young (2019)

(ed note: the Munditos are L5 colonies set in the asteroid belt (paired spinning habitats about 50 kilometers long, set inside conical mirrors). They are owned by their founding nation and must pay taxes. They are protected by military ships from their founding nation. Mundito Rosinante becomes independent, and decides to build a huge laser, energized by sunlight from the mirrors. Later they use the laser to power a large high-deltaV laser thermal rocket.)

     “Suppose we are preparing to defend against a future missile attack, like the one just past. Have you any ideas? I mean it's a little late to be brainstorming once the missile is on its way."
     "We might build a big laser,” he said at last. “I mean a really big laser, Governor, say 50 meters by 10,000 meters, or even 20,000. Nothing ultra-hot like the Navy uses, but continuous, you know? Pump it with the big mirrors."
     "Navy weapons doctrine calls for a power source to generate light, the hotter the better. We have the big arrays of mirrors for light. No need to use a middleman, as it were. We just build a cool, continuous gas laser, but very, very big. It ought to have an effective range of maybe 200,000 kilometers, and it could pick off a missile like nothing, don't you know?"

(ed note: Yes, lasers have to be pumped with monochromatic light and sunlight is polychromatic. Mundito Rosinante has a Japanese "dragon-scale mosaic mirror array" composing the two conical frustrums. The dragon-scale array is composed of tens of thousands of little mirrors, of three types. One type only reflects red light, one only blue, one only green. The mirrors are transparent to other colors. They coat the laser body with red and blue reflecting mirrors so only the monochromatic green light can enter the laser cavity. They also only use the green reflecting mirrors on the frusturms to send light to the laser.

Non-Japanese munditos use a monolithic aluminum mirror which reflects all colors of sunlight, and thus cannot be used to pump a huge laser. Monolithic aluminum mirrors are much cheaper. So Japanese munditos can have these lasers but others cannot.)

     "What about your idea to maximize the light density by using only one of the three colors of light our mirrors reflect?"
     "We've worked out the system for the green light best,” said Ilgen, running his hand over his crew cut. “We have that stack of mirrors—the red and blue mirrors left over from the quality-control work on making the big array—could we use them? How many do we have?"
     "The red and blue combined? Maybe 60 or 70 hectares,” said Skaskash. “That would give us a working length of maybe 16 kilometers. I think we really need 21 or 22."
     "Yes, 22 would take all the green light from one of the frustrums on the Don Q array-if we patched it up. But what about the cooling?"
     “Hey! Skaskash! If we built a pressurized jacket, oh, say one kilometer in diameter, the laser would be air-cooled except for the face, which would be silica! Then we could run a higher light-density and 16 kilometers would be enough! Hell! We could do it with 10!"

     "After the event, I ordered high-resolution pictures taken from Laputa."
     "This is the double frustum of Don Quixote during the cleanup,” she said, turning the print over. “This is almost the same view taken on January 20, showing the construction in the right-hand frustum in the interim. The technicians call it the Purple Shaft. Notice the support system, which can rotate the shaft in two planes. I imagine that if it was aimed at an object on the other side of the mirror array, a few of the mirrors could be removed."
     "This is an enlarged view of the same scene. It shows the Purple Shaft very clearly. We estimate that it is 1020 meters in diameter, 17,230 meters long. The outer surface is made of salvaged purlin tile mounted in salvaged purlin frames. The faint diamond pattern shows quite clearly."
     "It doesn't look purple at all,” said Hulvey. “Why do they call it the Purple Shaft?"
     "This is the device in operation,” she said. “A very short exposure time shows the inner structure vividly. It is a tube twelve or thirteen meters in diameter running the length of the structure. It is evidently covered with red and blue layered mirrors, so that it reflects purple light and passes green light into the gas mixture which the inner tube contains. In effect, you are looking at a huge gas laser pumped by an array of mirrors having an area of thousands of square kilometers."
     "The radiation data is consistent with methyl isopropyl mercury and carbon dioxide,” she replied, “but we don't know.”
     "Is it using the full power of the mirror array?” Hulvey asked.
     "No, on that shot they were using 30 percent,” she said. “We took a picture of the mirror, and had the computer calculate the angle of each mirror in the array. It gave us a false-color developed picture.” She pulled a print out of the pile. “Yellow is aimed at the laser, the red and red-purple are not. The little green rectangle was probably being used for something else."
     "Could they use the full power of the array to pump the laser?” asked Admiral Vong.
     "They've had it as high as 80 percent,” she said. “That is, we've seen them take it as high as 80 percent. It is a formidable weapon."

(ed note: the colony of Rosinante makes a treaty with Japan, and gives them the blueprints for the giant laser. The Japanese politicians are unhappy, since buiding lasers on their space colonies will make both the colonies and the the Japanese space navy harder to govern)

      "Rosinante has honored their agreement,” said Shinaka. “We have received their technical data for building the heat ray.
     "This heat ray,” said Shinaka, gesturing with his chopsticks, “it is a most troublesome thing. Why couldn't we have invented it ourselves so we could have suppressed it?"
     "It is implicit in the design of the Dragon Scale Mirror,” said Kogo. “I expect the reason we didn't invent it was because we consciously decided not to.” He ate a piece of tuna.
     "I was with the Dragon Scale Mirror project as a senior team manager back in ‘23 when it was getting started,” Kogo went on, “and the feature that most troubled the Admiralty at that time was the capability to use the mirror array as a defense against docking ships."
     "A short-range defense only,” said Shinaka. “Why were they troubled?"
     "A city wall is a short-range defense,” replied Kogo, wishing he could light up a cigar, “but when a city builds such a wall it may suddenly become more adventuresome in its foreign policy. The Admiralty feared the drift away from the Central Government. The habitats lend themselves to autarky very naturally. If they also become defensible, like castles, how will we be able to collect our taxes? The big laser was considered in that context, and we never went ahead with it because the Admiralty was afraid that such a powerful weapon in the hands of the habitat managers would make them impossible to control. That is what bothers you now, isn't it?"
     "Yes,” said Shinaka, eating a piece of octopus. “It diminishes our warships, also. Perhaps that bothers me even more."
     "It does not matter,” said Kogo, “the heat ray is there. Either we use it to advantage or we do not, but we cannot make it disappear. Consider that to use it one must have the Dragon Scale Mirror—which is standard on Japanese habitats, while only a small number of non-Japanese habitats have them. If we use it, we will have a significant military advantage for a significant length of time.” He smiled, showing his lower teeth. “I say build it!"
     "It is true,” conceded Shinaka, taking a fresh slice, “we would achieve a transient advantage with the device. What did you have in mind?"
     "Use it to free our Navy from defending fixed and scattered points,” said Kogo, “so that we can concentrate our forces for a decisive victory!"
     "The last time we did that was when we developed the Zero fighter plane at the beginning of World War II,” said Shinaka. “What happens afterward?"

     So,” said (Admiral) Kogo, puffing smoke. “Has any decision been reached about building the large lasers in our own habitats?"
     "We have reached an informal consensus,” replied (poltician) Seto. “If it were possible to return the engineering details to Rosinante and withdraw diplomatic recognition, we would do so."
     "That is unfortunately impossible,” said Kogo. “Have you decided yes or no?"
     "No,” said Seto. “That is, we have made no decision at this time."
     "Ah, so,” said Kogo, letting the smoke flow from his nose. “Once again our politicians temporize and waver. Does it not strike you as advantageous that if we fitted our habitats with the big laser, our navy would not be tied to their defense?"
     "That point has been discussed at length,” said Seto. “The admirals and the younger generals felt it was exciting and useful, and were outspokenly in favor. The civilians and the older generals felt it would encourage military adventurism."
     "Oh, come now,” protested Kogo. “This is the twenty-first century, after all."
     "You are in favor of producing the big lasers?” asked (Japanese intelligence service) Sumidawa. “Then please tell us against whom you would concentrate the might of the Japanese Navy."
     "We wouldn't have to concentrate it."
     "So sorry, Admiral Kogo,” replied Sumidawa. “We would at one stroke have achieved a significant but temporary military superiority in space. Which the admirals would urgently wish to exploit. Against whom? Against the North American Union (NAU), our major trading partner, here on Tellus?"
     "It is increasingly difficult to retain control of events in space,” said Seto. “The admirals, in particular, have shown a disturbing independence. You say this is the twenty-first century. How is it then that the Navy is seeking to capture the NAU base on Ceres against the wishes of the Diet?"
     "We have done far less than we might,” replied Kogo, flicking cigar ash into a sculptured bronze ashtray. “Indeed, Mr. Seto, the Navy has shown admirable restraint in the face of the NAU's provocations."
     "What provocations!” barked Seto.
     "The (NAU fleet) mutiny and the profound weakness which it revealed,” said Kogo. “We could reach out our hand and take Ceres. Instead, we piddle around with commerce raiding—piracy, if you like—because the Diet does not want us to upset the trading partners of our bloated merchants!"
     Seto flushed angrily. The House of Seto was one of the largest grain importers in Japan.
     "Stop trading and see children bloated with hunger, instead,” he said. “We depend for our life on the grain the NAU sells!"
     "They would not stop trading if we took Ceres,” Kogo commented mildly. “They need to sell the grain as much as we need to buy it."
     "You seem very willing to contemplate war with the NAU,” said Colonel Sumidawa. “What could we gain in space that would match our losses on Tellus?" (Terra)
     "We would not be starting a war,” said Kogo, “the NAU would merely have to accept our military superiority as a fact of life. On Tellus, it might lower the price of grain by ... oh, six or seven percent."
     "We can not win a war with the NAU!” said Seto. “Do you think we can win such a war?"
     Admiral Hideoshi Kogo sat back in his chair and blew a perfect smoke ring.
     "I am very sorry, Mr. Seto,” he said, “but as it happens I do think we can win such a war."

     "Right now I am concerned that the Japanese are building big laser prototypes at (Japanese asteroid colonies) Eije-Ito and Tanaka-Masada."
     "Defensive weapons, pure and simple,” Lady Dark said. “How can you worry about them?"
     "Up till now it was the Japanese Navy that provided the de facto protection,”
said Corporate Susan. “Being released from that detail, they are now free to roll around the Solar System like loose cannon. I wouldn't be surprised to find (our home) Rosinante in their path."

     "Perhaps you do not know, Captain. Please do not take offense, but Premier Ito felt that civilian control of the Imperial Japanese Navy would be weakened by building the big lasers. So in pursuit of this policy, what was done? The hijacking of the Foxy Lady was arranged, to prevent the completion of the Dragon Scale Mirror at NAU-Ceres I. Why? The NAU might build a big laser there, and then Japan would also have to build big lasers.” The image of Corporate Hulvey smoothed its slate-blue kimono. “Perfectly logical. If we did, then you must. You might call it prophylactic piracy. Why do you suppose that the NAU might want the big lasers at NAU-Ceres I?"
     "To protect their gold shipments against piracy,” Norigawa said, sipping his tea. “I, myself, have taken over two million ounces. In time, we would have taken the mines."
     "Quite so,” the computer said. “Premier Ito was already unable to control his navy. And to execute his policy, a policy designed to avoid losing still more control, on whom must he rely? That same navy, of course. It has taken time, but I have learned that the order to hijack the Foxy Lady came from the office of Admiral Hideoshi Kogo. Would it surprise you to learn that Admiral Kogo is the leading proponent of building big lasers on Japanese space stations?"

From LONG SHOT FOR ROSINANTE by Alexis Gilliland

STARGUARD (brev'tal bir, against the cold) The opposite of a Starcruiser (monolithic gargantuan dreadnought. Three were a match for an enemy solar system), since the diffusion of thousands of discrete members initially lacks any significant target. A Starcruiser might cut for hours through this jungle of tiny ships, mines, etc., until suddenly there were more targets than fire control could handle. Once such a ship began to take damage, the Starguard units quickly stung it to death. Total spherical complement about 4 million; mass 40 million tons; length about 100 km.

From Metagaming microgame HOLY WAR by Lynn Willis (1979)

The record began with a close up of one of the foldpoint fortresses. This was obviously library footage tacked on by the Sandarians for Altan benefit. The screen showed a great sphere that bristled with weapons and sensors. The dark snouts of several hundred laser ports dotted the surface of the sphere, as did a like number of missile launchers. Other features included thick layers of ablative shielding, power plant exhaust ports, and vast radiators to rid the fortresses of internal heat. A destroyer cruised past the fortress in the foreground of the picture, giving a sense of scale to the scene. The battle station was as large as a small asteroid, and brimming with destructive power.

“My God, what a behemoth!” Bethany said.

Drake nodded. “It’s even more impressive when you realize how much ship volume is normally taken up by photon engines and foldspace generators. That monster was designed to deliver its punch to the target without worrying about maneuvering. I’d estimate its power at about five blast ships, maybe more!”

From ANTARES DAWN by Michael McCollum (1986)

Space Superiority Platform

A variant on the orbital fortress is the Space Superiority Platform. Instead of defending the planet from invading spacefleets, this is an armed military station keeping an eye on the planet it is orbiting.

If a planet is balkanized, the platform will watch military ground units belonging to hostile nations, and bombard them if required. Militarily they have the high ground.

If the planet is a conquered one, or the government is oppressing the inhabitants, the platform will try to maintain government control and deal with revolts. By bombarding them if required.

Many early SF stories fret about the military advantage an armed space station confer upon the owning nation. Heinlein says trying to fight a space station (or orbiting spacecraft) from the ground is akin to a man at the bottom of a well conducting a rock-throwing fight with somebody at the top. One power-crazed dictator with a nuclear bomb armed station could rule the world! Space faring nations would need space scouts for defense.

But most experts nowadays say that turns out not to be the case. A nation can threaten another with nuclear annihilation far more cheaply with a few ICBMs, no station is required. And while ground launching sites can hide in rugged terrain, a space station can hide nowhere. Pretty much the entire facing hemisphere can attack the station with missiles, laser weapons, and propaganda.

In the real world, such platforms are currently limited to spy satellites. Orbiting nuclear bombing satellites are frowned upon. Or even things like the Strategic Defense Initiative.

Phil Shanton points out that you don't need a huge missile to destroy an orbiting space station, either. In 1979, the U.S. Air Force awarded a contract to the Vought company to develop an anti-satellite missile. It was not a huge missile from a large launch site. It was a relatively small missile launched by an F-15 Eagle interceptor in a zoom-climb. Vought developed the ASM-135 Anti-Satellite Missile (ASAT), and on 13 September 1985 it successfully destroyed the solar observatory satellite "P78-1". This means that an evil-dictator world-dominator nuke-station not only has to worry about every ground launch site, but also every single fighter aircraft.

It has also been modeled that the U.S. Navy could take out a satellite with a Standard Missile 3.

Things are different, of course if the situation is an extraplanetary fleet that remotely bombs the planet to destroy all the infrastructure. The fleet can construct a space superiority platform while the planet is struggling to rebuild its industrial base. Then the platform can bomb any planetary site that is getting too advanced in rebuilding. This is known as "not letting the weeds grow too tall.


      "It‘s getting bad, isn‘t it?" he asked.
     Heinemann sighed. "Worse than you might think, Hauptmann. Even the ranks of the Peace Enforcers are not immune to these internecine squabbles that have broken out all over the face of the Earth. If it is not the North Americans against the South, then it is the Australians versus Indonesia, or Japan against China and West Russia. I tell you the whole world is going to Satan in a hand trolley."…

     …Wing Commander Livingston was on detached service from the RAF. His powder blue uniform looked out of place next to Stassel‘s silver and black. Stassel sat in an aluminum chair and took notes as Livingston reeled off figures in his clipped, Oxford accent.
     " … Your area of responsibility will include Longitudes 100 West to 120 West, Captain. Your satellite will be in an alternating synchronous orbit with Beta-Nine, of course, and you will have prime responsibility in the Northern Hemisphere during even watch periods and Southern Hemisphere during the odd. Luckily, south of the equator there is only empty ocean between 100 and 120 West, so you‘ll be able to get some rest.
     "You are hereby directed to pay especially close attention to the situation around the US-Mexican border..." Livingston looked up, the podium light casting shadows on his face. "Watch your a** on that one, Fred. It is a tinderbox. The Mexicans are bound to try a raid between now and the Security Council vote on Friday."…

     …The second development was the formation of the UN Peace Enforcers following the twenty-day scare of the Misfire War. The Peace Enforcers were a multinational force with a single mission: To stop any aggressor who struck against any UN member state. Their unofficial motto was, "You start the war and we‘ll finish it!"
     In theory, any act of aggression by one nation against another would be met instantly by the orbital lasers and Peace Enforcer fusion rockets. However, in practice there was a threshold level of violence, a tripwire effect, below which the cumbersome Security Council machinery would fail to respond.…

     …The lift whooshed him upward toward the station axis. The familiar, ever changing Coriolus force as he approached the axis clamped his stomach muscles in a familiar vise. At the zero gravity axis, Stassel kicked off and floated to the docking port at the north pole of the station and through a flexible tube to the shuttle.
     The shuttle was a standard orbit-to-orbit supply bus — three spherical sections assembled as though they had been skewered onto a shish-kabob sword with a hydrogen-fueled rocket at one end and the personnel cabin at the other. The shuttle was used to transfer personnel and consumables from the mid-Atlantic Space Station (and her mid-Pacific counterpart) to the orbiting Peace Control Satellites.
     The station was in synchronous orbit 37,000 kilometers above the equator so that it hung perpetually over thirty degrees west longitude. The Peace Control Satellites also orbited 37,000 kilometers out, but in two separate orbits, each inclined sixty degrees from the plane of the equator and from each other. Each satellite thus described a figure eight over a stationary strip of land, taking one day for the full traverse across the face of the planet. The satellites climbed to the latitude of Hudson‘s Bay in the north and dropped to the northern tip of Antarctica in the south. Spaced every ten degrees of longitude — or 7500 kilometers apart — in their orbits, the satellites passed over every industrialized and developing nation on Earth four times daily. The seventy satellites and two space stations in orbit gave the UN‘s hundred gigawatt lasers overlapping fields of fire against any conceivable opponent. War was impossible.
     At least, that was the theory.…

     …The pilot cleared his throat. "Uh, get your things ready for transfer. We‘ll be coming up on Alpha-Nine in about twenty minutes."
     Peace Control Satellite Alpha-Nine floated into view fifteen minutes later. Like all such, it was constructed in two pieces. The thirty-meter long cylinder that housed the hydrogen-fluorine gas dynamic laser and its fuel tanks was attached by a hundred meter long umbilical to a sphere painted in a haphazard pattern of light and dark checks. The ten-meter sphere was festooned with antennas, telescopes, and the more arcane paraphernalia of a dozen different kinds of information sensors and communications devices. The doghouse, as the sphere was called, was crammed solid with hardware that acted as the satellite‘s eyes and ears and brains. The umbilical — floating limply in space as the shuttle moved in slowly for a hard dock — connected the two halves of the satellite together and isolated the laser module with its sensitive aiming mechanisms from extraneous perturbations. For instance, the force of a hundred-ton shuttle coming to rest in the doghouse‘s docking collar, or the effect of the satellite commander doing his morning calisthenics.
     The satellite living quarters were located at the end of the doghouse arbitrarily labeled 'top'. They were tiny, consisting of a control center, shower bath, and combination galley and recreation-bunk room. The crew quarters of a PCS did not have to be large. The satellite commander was the only crewmember. Even so, the UN had a perennial problem keeping seventy satellites manned with reliable people on a one-week rotation schedule. What the satellite commander lacked in numbers, he more than made up for in firepower. At his fingertips were the controls to a hundred-gigawatt laser, powerful enough to strike down any opponent. Moreover, if needed, he would be backed up by the power of the space fleet.

Interdiction Platform

This is a sort of combination of Space Superiority Platform and Planetary Defense. The idea is that the station is to prevent anything unauthorized from entering or leaving the planet it is orbiting.

  • A planet might be invested, meaning that the planet is under siege from whoever owns the space station. The station does not want planetary inhabitants escaping, nor does it want blockade runners entering.
  • A planet might be interdicted because they contain something very dangerous (Xenomorphs, thionite, the City on the Edge of Forever, replicators, or 100% lethal plagues).
  • A planet might be interdicted because it has something very valuable and the station owner does not want poachers sneaking in and stealing any.

Planetary Fortress

After the invaders have neutralized the defenders orbital fortresses, the only thing left stopping the invaders from carpet-bombing the vulnerable planet are the defending planetary fortresses. Orbital fortresses do have problems with heat radiators and supply. Planetary fortresses on the other hand have practically no radiator or supply problems, since they have an entire planet for support. In the Strategic Defense Initiative, concepts looked into included "Extended Range Interceptor", "Homing Overlay Experiment ", and "Exoatmospheric Reentry-vehicle Interception System"

In space opera, "force fields" are generally spherical. So a planetary fortress (or civilian city) protected by such a field will have a circular boarder. Anything outside of the circle will also be outside of the force field, and thus vulnerable to bombardment. If the force field prevents defending weapons from firing out along with preventing attacking weapons from firing in, the fortress might have weapon emplacements outside of the boundary of the force field. In many space operas, invaders will deal with planetary fortresses under a force field by constantly using weapons on the ground around the fort. The land will eventually become a sea of lava, which will put the fort at a disadvantage.

In Larry Niven and Jerry Pournelle's classic The Mote In God's Eye, some times Imperial task forces would find the Langston Field defense over the cities on a rebel planet too difficult to crack. If the task force was under a severe time limit, they would be forced into the draconian option of using nuclear weapons to take out all the agriculture on the planet, then leaving. The rebels would then mostly starve to death, since it is impossible to ship food for millions of people over insterstellar distances. The imperials would have fullfilled their mission, since the rebels would cease to be a threat, eventually.


Rod Blaine scowled at the words flowing across the screen of his pocket computer. The physical data were current, but everything else was obsolete. The rebels had changed even the name of their world, from New Chicago to Dame Liberty. Her government would have to be built all over again. Certainly she'd lose her delegates; she might even lose the right to an elected assembly.

He put the instrument away and looked down. They were over mountainous country, and he saw no signs of war. There hadn't been any area bombardments, thank God.

It happened sometimes: a city fortress would hold out with the aid of satellite-based planetary defenses. The Navy had no time for prolonged sieges. Imperial policy was to finish rebellions at the lowest possible cost in lives—but to finish them. A holdout rebel planet might be reduced to glittering lava fields, with nothing surviving but a few cities lidded by the black domes of Langston Fields; and what then? There weren't enough ships to transport food across interstellar distances. Plague and famine would follow.

From THE MOTE IN GOD'S EYE by Larry Niven and Jerry Pournelle (1974)

And Alistair Young points out that if the spaceports of the planet use laser launchers they are also planetary fortresses.


It is a truism of celestial warfare that among the most valuable targets to seize in the course of a major planetary assault operation is the primary planetary starport or local starports close to the intended target(s) of the operation. Starports, for all the obvious reasons, make perfect orbitheads, offering existing facilities eminently suitable for the landing and disembarkation of troops and materiel in quantity. (Orbital elevators, by contrast, are usually considered too fragile and susceptible to sabotage for this purpose, if the enemy are willing to absorb the ensuing damage to their own planet, until the orbitals and the continental area surrounding the elevator have been entirely secured.)

Why, then, are combat drops rarely, if ever, targeted at the vicinity of starports?

Again, it is important to remember that which is unseen. The popular image of starports is heavily biased towards the facilities for ground-landing starships — understandably, since the giant launch/landing pads built to handle nucleonic-thermal ships, with their blast-deflecting berms, “hot” shafts, and motile structures are some of the most impressive structures ever built — and towards the shuttleport terminals used by commuters and starship passengers alike. Nonetheless, the majority of cargo in the developed Worlds is carried by dedicated spacecraft incapable of atmospheric landing, to and from which cargo is transported in high volumes using suitably cheap methods: either laser-launch/deceleration facilities, mass drivers, or both, in which case the former handles light or delicate cargo and the latter hardbulk.

What this means in military terms is that, any other defense grid aside, the majority of starports in the developed Worlds have at their disposal a multi-gigawatt-range phased-array laser system, and/or a pair of mass drivers capable of accelerating a solid slug the size of a shipping container (or, equally effective, a shipping container packed with rubble or cheap heavy-metal ingots) to orbital velocities — both, admittedly, equipped with safety systems designed to prevent them from being used in exactly the manner which is desirable for military purposes, but that is something usually corrected readily enough by a software change — along with all the high-resolution traffic-control sensor equipment needed to target them effectively.

It is also a truism of warfare in general that one shouldn’t stab a heavily-armed man in the front. That is doubly relevant when the things they’re using as weapons are also the value that you want to capture.

— Elementary Principles of Orbit-to-Ground Maneuver Plans, pub. INI Press


However, it should not be assumed that any space colony will be totally defenseless.  Depending on the configuration and environment of the colony, it is possible that the colony will have some form of anti-meteor system in place, which could easily be repurposed to serve as a ground-based defense laser.  The problem with the idea of such a system is that it’s relatively easy to put a colony underground, and being underground also provides protection from radiation.  Meteors large enough to be a threat to the buried colony are likely to be too large for a practical laser system to deal with, but should also give enough warning to be deflected by other methods.

A much more plausible source for some sort of fixed ground-based defense is a laser propulsion system.  This would either be used to boost spacecraft into orbit, or to propel them between planets.  In either case, the biggest issue is likely to be setting up the system to target non-cooperative spacecraft.  On the other hand, the fact that such a system is fixed removes its value as an offensive weapon, and such capability might be standard.  In either case, the existence of such a system will make the possibility of a direct attack even more remote, limiting warfare to skirmishing between the colonies involved.  A ground invasion is remotely plausible, but the defender must either be taken totally by surprise or be faced with overwhelming force, both of which are unlikely in the sort of conflict described here.  Farther problems are the requirement for overland movement, and the difficulty posed by the defender’s orbital bombardment.

by Byron Coffey (2016)

“We’ve had time to map the planet rather extensively over the last thirty hours. In the process, we have spotted numerous large installations built on the polar ice caps. Our experts have tentatively identified them as a network of planetary defense centers. To judge by their number, this may well be the best defended planet in human space!”

Sandarian Military Headquarters was a truncated pyramid that had been built on an island of bare rock in the middle of an ocean of ice. At first, the structure was a tiny patch of brown on the horizon amid an endless panorama of white. Then, as the aircar carrying Duke Bardak, Richard Drake, and Argos Cristobal closed the distance, the true size of the building became increasingly apparent with each passing second.

“Big building,” Drake said to Bardak.

“Big enough,” the Sandarian nobleman replied. “It measures one kilometer to a side and rises half-a-kilometer above bedrock. The sides are armor plated to a depth of two meters, and screened by anti-rad fields.”

“Wouldn’t it have been more convenient to build it near Capital?” Drake asked. It had taken the aircar some three hours to fly from Capital to Military Headquarters, and for virtually the whole of that time, the car had droned above a seemingly endless expanse of ice.

“More convenient, yes. Safer, no. Military Headquarters doubles as a planetary defense center. You no doubt saw many of our PDCs from orbit.”

Drake nodded.

“An operational planetary defense center requires a lot of power and generates a considerable quantity of waste heat. In a prolonged engagement, the waste heat from a single fixed mount laser can raise the temperature of even a medium size river by several degrees. Were we to build our PDCs in the temperate zone, we would trigger a massive fish kill every time we tested the weapons. The polar ice cap, on the other hand, has a heat carrying capacity that is virtually infinite. You cannot see it, but the ice fields around Military Headquarters are honeycombed with heat rejection piping. Theoretically, we could fire every fixed mount laser in the battery continuously for days before we would have to worry about overheating problems.

“Then, of course, there are the strategic considerations. By spreading our installations evenly over Sandar’s surface, we avoid blind spots while also dispersing our military assets. Lastly, should the Ryall ever get this far — highly unlikely considering the power of our foldpoint fortresses — we hope to draw their fire to the PDCs and away from the cities.”

As Bardak talked, the aircar circled Military Headquarters to give the Altans a good look at the manmade mountain below. The sides of the pyramid were studded with phased array radar elements, as well as a variety of less identifiable sensors. Around the base, the business ends of several dozen fixed mount lasers poked skyward.

From ANTARES DAWN by Michael McCollum (1986)

(ed note: this was written before the invention of the laser. The fortress is called Project Thor, no relation to Rods From God, and is located on the Moon near Pico crater. It is about to be attacked by three spacecraft. Dr. Steffanson has invented a technobabble "ray screen" that reflects electromagnetic radiation. Jamieson and Wheeler are hiding in a crevasse several miles away near their crippled tractor. The description is so cinematic that it is just begging for an SF artist to depict it.)

EVEN TODAY, little has ever been revealed concerning the weapons used in the Battle of Pico. It is known that missiles played only a minor part in the engagement. In space warfare, anything short of a direct hit is almost useless, since there is nothing to transmit the energy of a shock wave. An atom bomb exploding a few hundred meters away can cause no blast damage and even its radiation can do little harm to well-protected structures. Moreover, both Earth and the Federation had effective means of diverting ordinary projectiles.

Purely non-material weapons would have to play the greatest role. The simplest of these were the ion-beams, developed directly from the drive-units of spaceships. Since the invention of the first radio tubes, almost three centuries before, men had been learning how to produce and focus ever more concentrated streams of charged particles. The climax had been reached in spaceship propulsion with the so-called "ion rocket," generating its thrust from the emission of intense beams of electrically charged particles. The deadliness of these beams had caused many accidents in space, even though they were deliberately defocused to limit their effective range.

There was, of course, an obvious answer to such weapons. The electric and magnetic fields which produced them could also be used for their dispersion, converting them from annihilating beams into a harmless, scattered spray.

More effective, but more difficult to build, were the weapons using pure radiation. Yet even here, both Earth and the Federation had succeeded. It remained to be seen which had done the better job—the superior science of the Federation, or the greater productive capacity of Earth.

Less than a million kilometers away, Carl Steffanson sat at a control desk and watched the image of the sun, picked up by one of the many cameras that were the eyes of Project Thor. The group of tired technicians standing around him had almost completed the equipment before his arrival; now the discriminating units he had brought from Earth in such desperate haste had been wired into the circuit.

Steffanson turned a knob, and the sun went out. He flicked from one camera position to another, but all the eyes of the fortress were equally blind. The coverage was complete.

Too weary to feel any exhilaration, he leaned back in his seat and gestured toward the controls.

"It's up to you now. Set it to pass enough light for vision, but to give total rejection from the ultra-violet upward. We're sure none of their beams carry any effective power much beyond a thousand Ångström. They'll be very surprised when all their stuff bounces off. I only wish we could send it back the way it came."

"Wonder what we look like from outside when the screen's on?" said one of the engineers.

"Just like a perfectly reflecting mirror. As long as it keeps reflecting, we're safe against pure radiation. That's all I can promise you."

(ed note: 1000 Ångströms = 100 nanometers = extreme ultraviolet)

There was no warning of any kind. Suddenly the gray, dusty rocks of the Sea of Rains were scorched by a light they had never known before in all their history. Wheeler's first impression was that someone had turned a giant searchlight full upon the tractor; then he realized that this sun-eclipsing explosion was many kilometers away. High above the horizon was a ball of violet flame, perfectly spherical, and rapidly losing brilliance as it expanded. Within seconds, it had faded to a great cloud of luminous gas. It was dropping down toward the edge of the Moon, and almost at once had sunk below the skyline like some fantastic sun.

"We were fools," said Jamieson gravely. "That was an atomic warhead—we may be dead men already."

"Nonsense," retorted Wheeler, though without much confidence. "That was fifty kilometers away. The gammas would be pretty weak by the time they reached us—and these walls aren't bad shielding."

"I can just see the dome," he said with some satisfaction. "It's quite unchanged, as far as I can tell."

"It would be," Jamieson replied. "They must have managed to explode that bomb somehow while it was miles away."

"Perhaps it was only a warning shot."

"Not likely! No one wastes plutonium for firework displays. That meant business. I wonder when the next move is going to be?"

It did not come for another five minutes. Then, almost simultaneously, three more of the dazzling atomic suns burst against the sky. They were all moving on trajectories that took them toward the dome, but long before they reached it they had dispersed into tenuous clouds of vapor.

From somewhere beyond Pico, six sheaves of flame shot up into the sky at an enormous acceleration. The dome was launching its first missiles, straight into the face of the sun. The Lethe and the Eridanus were using a trick as old as warfare itself; they were approaching from a direction in which their opponent would be partly blinded. Even radar could be distracted by the background of solar interference, and Commodore Brennan had enlisted two large sunspots as minor allies.

Then he saw that something was happening to the dome. It was no longer a gleaming spherical mirror reflecting only the single image of the sun. Light was splashing from it in all directions, and its brilliance was increasing second by second. From somewhere out in space, power was being poured into the fortress. That could only mean that the ships of the Federation were floating up there against the stars, beaming countless millions of kilowatts down upon the Moon. But there was still no sign of them, for there was nothing to reveal the track of the river of energy pouring invisibly through space.

The dome was now far too bright to look upon directly, and Wheeler readjusted his filters. He wondered when it was going to reply to the attack, or indeed if it could do so while it was under this bombardment. Then he saw that the hemisphere was surrounded by a wavering corona, like some kind of brush discharge. Almost at the same moment, Jamieson's voice rang in his ears.

"Look, Con—right overhead!"

He glanced away from the mirror and looked directly into the sky. For the first time, he saw one of the Federation ships. Though he did not know it, he was seeing the Acheron, the only spaceship ever to be built specifically for war. It was clearly visible, and seemed remarkably close. Between it and the fortress, like an impalpable shield, flared a disk of light which as he watched turned cherry-red, then blue-white, then the deadly searing violet seen only in the hottest of the stars. The shield wavered back and forth, giving the impression of being balanced by tremendous and opposing energies. As Wheeler stared, oblivious to his peril, he saw that the whole ship was surrounded by a faint halo of light, brought to incandescence only where the weapons of the fortress tore against it.

It was some time before he realized that there were two other ships in the sky, each shielded by its own flaming nimbus. Now the battle was beginning to take shape; each side had cautiously tested its defenses and its weapons, and only now had the real trial of strength begun.

The two astronomers stared in wonder at the moving fireballs of the ships. Here was something totally new—something far more important than any mere weapon. These vessels possessed a means of propulsion which must make the rocket obsolete. They could hover motionless at will, then move off in any direction at a high acceleration. They needed this mobility; the fortress, with all its fixed equipment, far out-powered them and much of their defense lay in their speed.

In utter silence, the battle was rising to its climax. Millions of years ago the molten rock had frozen to form the Sea of Rains, and now the weapons of the ships were turning it once more to lava. Out by the fortress, clouds of incandescent vapor were being blasted into the sky as the beams of the attackers spent their fury against the unprotected rocks. It was impossible to tell which side was inflicting the greater damage. Now and again a screen would flare up, as a flicker of heat passes over white-hot steel. When that happened to one of the battleships, it would move away with that incredible acceleration, and it would be several seconds before the focusing devices of the fort had located it again.

Both Wheeler and Jamieson were surprised that the battle was being fought at such short ranges. There was probably never more than a hundred kilometers between the antagonists, and usually it was much less than this. When one fought with weapons that traveled at the speed of light—indeed, when one fought with light itself—such distances were trivial.

The explanation did not occur to them until the end of the engagement. All radiation weapons have one limitation: they must obey the law of inverse squares. Only explosive missiles are equally effective from whatever range they have been projected: if one is hit by an atomic bomb, it makes no difference whether it has traveled ten kilometers or a thousand.

But double the distance of any kind of radiation weapon, and you divide its power by four owing to the spreading of the beam. No wonder, therefore, that the Federal commander was coming as close to his objective as he dared.

The fort, lacking mobility, had to accept any punishment the ships could give it. After the battle had been on for a few minutes, it was impossible for the unshielded eye to look anywhere toward the south. Ever and again the clouds of rock vapor would go sailing up into the sky, falling back on the ground like luminous steam. And presently, as he peered through his darkened goggles and maneuvered his clumsy periscope, Wheeler saw something he could scarcely believe. Around the base of the fortress was a slowly spreading circle of lava, melting down ridges and even small hillocks like lumps of wax.

That awe-inspiring sight brought home to him, as nothing else had done, the frightful power of the weapons that were being wielded only a few kilometers away. If even the merest stray reflection of those energies reached them here, they would be snuffed out of existence as swiftly as moths in an oxy-hydrogen flame.

The three ships appeared to be moving in some complex tactical pattern, so that they could maintain the maximum bombardment of the fort while reducing its opportunity of striking back. Several times one of the ships passed vertically overhead, and Wheeler retreated as far into the crack as he could in case any of the radiation scattered from the screens splashed down upon them. Jamieson, who had given up trying to persuade his colleague to take fewer risks, had now crawled some distance along the crevasse, looking for a deeper part, preferably with a good overhang. He was not so far away, however, that the rock was shielding the suit-radios, and Wheeler gave him a continuous commentary on the battle.

It was hard to believe that the entire engagement had not yet lasted ten minutes. As Wheeler cautiously surveyed the inferno to the south, he noticed that the hemisphere seemed to have lost some of its symmetry. At first he thought that one of the generators might have failed, so that the protective field could no longer be maintained. Then he saw that the lake of lava was at least a kilometer across, and he guessed that the whole fort had floated off its foundations. Probably the defenders were not even aware of the fact. Their insulation must be taking care of solar heats, and would hardly notice the modest warmth of molten rock.

And now a strange thing was beginning to happen. The rays with which the battle was being fought were no longer quite invisible, for the fortress was no longer in a vacuum. Around it the boiling rock was releasing enormous volumes of gas, through which the paths of the rays were as clearly visible as searchlights in a misty night on Earth. At the same time Wheeler began to notice a continual hail of tiny particles around him. For a moment he was puzzled; then he realized that the rock vapor was condensing after it had been blasted up into the sky. It seemed too light to be dangerous, and he did not mention it to Jamieson—it would only give him something else to worry about. As long as the dust fall was not too heavy, the normal insulation of the suits could deal with it. In any case, it would probably be quite cold by the time it got back to the surface.

The tenuous and temporary atmosphere round the dome was producing another unexpected effect. Occasional flashes of lightning darted between ground and sky, draining off the enormous static charges that must be accumulating around the fort. Some those flashes would have been spectacular by themselves—but they were scarcely visible against the incandescent clouds that generated them.

Wheeler never knew why the fortress waited so long before it used its main weapon. Perhaps Steffanson—or whoever was in charge—was waiting for the attack to slacken so that he could risk lowering the defenses of the dome for the millisecond that he needed to launch his stiletto.

Wheeler saw it strike upward, a solid bar of light stabbing it the stars. He remembered the rumors that had gone round tie Observatory. So this was what had been seen, flashing above the mountains. He did not have time to reflect on the staggering violation of the laws of optics which this phenomenon implied, for he was staring at the ruined ship above his head. The beam had gone through the Lethe as if she did not exist; the fortress had speared her as an entomologist pierces a butterfly with a pin.

Whatever one's loyalties, it was a terrible thing to see ho the screens of that great ship suddenly vanished as her generators dies, leaving her helpless and unprotected in the sky. The secondary weapons of the fort were at her instantly, tearing out great gashes of metal and boiling away her armor layer by layer. Then, quite slowly, she began to settle toward the Moon, still on an even keel. No one will ever know what stopped her, probably some short-circuit in her controls, since none of her crew could have been left alive. For suddenly she went off to the east in a long, flat trajectory. By that time most of her hull had been boiled away and the skeleton of her framework was almost completely exposed. The crash came, minutes later, as she plunged out of sight beyond the Teneriffe Mountains. A blue-white aurora flickered for a moment below the horizon, and Wheeler waited for the shock to reach him.

And then, as he stared into the east, he saw a line of dust rising from the plain, sweeping toward him as if driven by a mighty wind. The concussion was racing through the rock, hurling the surface dust high into the sky as it passed. The swift, inexorable approach of that silently moving wall, advancing at the rate of several kilometers a second, was enough to strike terror into anyone who did not know its cause. But it was quite harmless; when the wave-front reached him, it was as if a minor earthquake had passed. The veil of dust reduced visibility to zero for a few seconds, then subsided as swiftly as it had come. When Wheeler looked again for the remaining ships, they were so far away that their screens had shrunk to little balls of fire against the zenith. At first he thought they were retreating; then, abruptly, the screens began to expand as they came down into the attack under a terrific vertical acceleration. Over by the fortress the lava, like some tortured living creature, was throwing itself madly into the sky as the beams tore into it.

The Acheron and Eridanus came out of their dives about a kilometer above the fort. For an instant, they were motionless; then they went back into the sky together. But the Eridanus had been mortally wounded, though Wheeler knew only that one of the screens was shrinking much more slowly than the other.

With a feeling of helpless fascination, he watched the stricken ship fall back toward the Moon. He wondered if the fort would use its enigmatic weapon again, or whether the defenders realized that it was unnecessary.

About ten kilometers up, the screens of the Eridanus seemed to explode and she hung unprotected, a blunt torpedo of black metal, almost invisible against the sky. Instantly her light-absorbing paint, and the armor beneath, were torn off by the beams of the fortress. The great ship turned cherry-red, then white. She swung over so that her prow turned toward the Moon, and began her last dive. At first it seemed to Wheeler that she was heading straight toward him; then he saw that she was aimed at the fort. She was obeying her captain's last command.

It was almost a direct hit. The dying ship smashed into the lake of lava and exploded instantly, engulfing the fortress in an expanding hemisphere of flame. This, thought Wheeler, must surely be the end. He waited for the shock wave to reach him, and again watched the wall of dust sweep by—this time into the north. The concussion was so violent that it jerked him off his feet, and he did not see how anyone in the fort could have survived. Cautiously, he put down the mirror which had given him almost all his view of the battle, and peered over the edge of his trench. He did not know that the final paroxysm was yet to come.

Incredibly, the dome was still there, though now it seemed that part of it had been sheared away. And it was inert and lifeless: its screens were down, its energies exhausted, its garrison, surely, already dead. If so, they had done their work. Of the remaining Federal ship, there was no sign. She was already retreating toward Mars, her main armament completely useless and her drive units on the point of failure. She would never fight again

"What puzzles me most of all," Wheeler concluded, "is the weapon the fort used to destroy the battleship. It looked like a beam of some kind, but of course that's impossible. No beam can be visible in a vacuum. And I wonder why they only used it once? Do you know anything about it?"

"I'm afraid not," replied Sadler, which was quite untrue. He still knew very little about the weapons in the fort, but this was the only one he now fully understood. He could well appreciate why a jet of molten metal, hurled through space at several hundred kilometers a second by the most powerful electromagnets ever built, might have looked like a beam of light flashing a for an instant. And he knew that it was a short-range weapon designed to pierce the fields which would deflect ordinary projectiles. It could he used only under ideal conditions, and it took many minutes to recharge the gigantic condensers which powered the magnets.

(ed note: there is no reason for the metal to be molten. It is better to be solid, which would make the weapon a species of mass-driver)

From EARTHLIGHT by Arthur C. Clarke (1955)

(ed note: This is pure space opera with zero scientific accuracy. This is probably where Sir Arthur C. Clarke got the idea of the sea of lava around Project Thor. In the following, they use a handwaving method to turn copper into pure energy with all the might of e=mc2, for electricity and explosives. The transparent material is pure handwavium that is several thousand times as strong as steel.)

"There, we can see what they're doing now," and DuQuesne anchored the vessel with an attractor. "I want to see if they've got many of those space-ships in action, and you will want to see what war is like, when it is fought by people, who have been making war steadily for ten thousand years."

Poised at the limit of clear visibility, the two men studied the incessant battle being waged beneath them. They saw not one, but fully a thousand of the globular craft high in the air and grouped in a great circle around an immense fortification upon the ground below. They saw no airships in the line of battle, but noticed that many such vessels were flying to and from the front, apparently carrying supplies. The fortress was an immense dome of some glassy, transparent material, partially covered with slag, through which they saw that the central space was occupied by orderly groups of barracks, and that round the circumference were arranged gigantic generators, projectors, and other machinery at whose purposes they could not even guess. From the base of the dome a twenty-mile-wide apron of the same glassy substance spread over the ground, and above this apron and around the dome were thrown the mighty defensive ray-screens, visible now and then in scintillating violet splendor as one of the copper-driven Kondalian projectors sought in vain for an opening. But the Earth-men saw with surprise that the main attack was not being directed at the dome; that only an occasional ray was thrown against it in order to make the defenders keep their screens up continuously. The edge of the apron was bearing the brunt of that vicious and never-ceasing attack, and most concerned the desperate defense.

For miles beyond that edge, and as deep under it as frightful rays and enormous charges of explosive copper could penetrate, the ground was one seething, flaming volcano of molten and incandescent lava; lava constantly being volatilized by the unimaginable heat of those rays and being hurled for miles in all directions by the inconceivable power of those explosive copper projectiles—the heaviest projectiles that could be used without endangering the planet itself—being directed under the exposed edge of that unbreakable apron, which was in actuality anchored to the solid core of the planet itself; lava flowing into and filling up the vast craters caused by the explosions. The attack seemed fiercest at certain points, perhaps a quarter of a mile apart around the circle, and after a time the watchers perceived that at those points, under the edge of the apron, in that indescribable inferno of boiling lava, destructive rays, and disintegrating copper, there were enemy machines at work. These machines were strengthening the protecting apron and extending it, very slowly, but ever wider and ever deeper as the ground under it and before it was volatilized or hurled away by the awful forces of the Kondalian attack. So much destruction had already been wrought that the edge of the apron and its molten moat were already fully a mile below the normal level of that cratered, torn, and tortured plain.

Now and then one of the mechanical moles would cease its labors, overcome by the concentrated fury of destruction centered upon it. Its shattered remnants would be withdrawn and shortly, repaired or replaced, it would be back at work. But it was not the defenders who had suffered most heavily. The fortress was literally ringed about with the shattered remnants of airships, and the riddled hulls of more than a few of those mighty globular cruisers of the void bore mute testimony to the deadliness and efficiency of the warfare of the invaders.

From SKYLARK THREE by E. E. "Doc" Smith (1930)

(ed note: again, pure space opera. Again lava is a factor)

To such good purpose did every Valeronian do his part that at dawn of The Day everything was in readiness for the Chloran visitation. The immense fortress was complete and had been tested in every part, from the ranked batteries of gigantic converters and generators down to the most distant outlying visiray viewpoint. It was powered, armed, equipped, provisioned, garrisoned. Every once-populated city was devoid of life, its inhabitants having dispersed over the face of the globe, to live in isolated groups until it had been decided whether the proud civilization of Valeron was to triumph or to perish.

Promptly as that sunrise the Chloran explorer appeared at the lifeless mine, and when he found the loading hoppers empty he calmly proceeded to the nearest city and began to beam it down. Finding it deserted he cut off, and felt a powerful spy ray, upon which he set a tracer. This time the ray held up and he saw the immense fortress which had been erected during his absence; a fortress which he forthwith attacked viciously, carelessly, and with the loftily arrogant contempt which seemed to characterize his breed.

But was that innate contemptuousness the real reason for that suicidal attempt? Or had that vessel's commander been ordered by the Great Ones to sacrifice himself and his command so that they could measure Valeron's defensive power? If so, why did he visit the mine at all and why did he not know beforehand the location of the fortress? Camouflage? In view of what the Great Ones of Chlora must have known, why that commander did what he did that morning no one of Valeron ever knew.

The explorer launched a beam—just one. Then Quedrin Radnor pressed a contact and out against the invader there flamed a beam of such violence that the amoebus had no time to touch his controls, that even the automatic trips of his zone of force—if he had such trips—did not have time in which to react. The defensive screens scarcely flashed, so rapidly did that terrific beam drive through them, and the vessel itself disappeared almost instantly—molten, vaporized, consumed utterly. But there was no exultation beneath Valeron's mighty dome. From the Bardyle down, the defenders of their planet knew full well that the real attack was yet to come, and knew that it would not be long delayed.

Nor was it. Nor did those which came to reduce Valeron's far-flung stronghold in any way resemble any form of space ship with which humanity was familiar. Two stupendous structures of metal appeared, plunging stolidly along, veritable flying fortresses, of such enormous bulk and mass that it seemed scarcely conceivable for them actually to support themselves in air.

Simultaneously the two floating castles launched against the towering dome of defense the heaviest beams they could generate and project. Under that awful thrust Valeron's mighty generators shrieked a mad crescendo and her imponderable shield radiated a fierce, eye-tearing violet, but it held. Not for nothing had the mightiest minds of Valeron wrought to convert their mechanisms and forces of peace into engines of war; not for nothing had her people labored with all their mental and physical might for almost twoscore days and nights, smoothly and efficiently as one mind in one body. Not easily did even Valeron's Titanic defensive installation carry that frightful load, but they carried it.

Then, like mythical Jove hurling his bolt—like, that is, save that beside that Valeronian beam any possible bolt of lightning would have been as sweetly innocuous a caress as young love's first kiss—Radnor drove against the nearer structure a beam of concentrated fury; a beam behind which was every volt and every ampere that his stupendous offensive generators could yield.

The Chloran defenses in turn were loaded grievously, but in turn they also held; and for hours then there raged a furiously spectacular struggle. Beams, rods, planes, and needles of every known kind and of every usable frequency of vibratory energy were driven against impenetrable neutralizing screens. Monstrous cannon, hurling shells with a velocity and of an explosive violence far beyond anything known to us of Earth, radio-beam-dirigible torpedoes, robot manned drill planes, and many other lethal agencies of ultrascientific war—all these were put to use by both sides in those first few frantic hours, but neither side was able to make any impression upon the other. Then, each realizing the other's defenses had been designed to withstand his every force, the intensive combat settled down to a war of sheer attrition.

Radnor and his scientists devoted themselves exclusively to the development of new and ever more powerful weapons of offense; the Chlorans ceased their fruitless attacks upon the central dome and concentrated all their offensive power into two semicircular arcs, which they directed vertically downward upon the outer ring of the Valeronian works in an incessant and methodical flood of energy.

They could not pierce the defensive shields against Valeron's massed power, but they could and did bring into being a vast annular lake of furiously boiling lava, into which the outer ring of fortresses began slowly to crumble and dissolve. This method of destruction, while slow, was certain; and grimly, pertinaciously, implacably, the Chlorans went about the business of reducing Valeron's only citadel.

The Bardyle wondered audibly how the enemy could possibly maintain indefinitely an attack so profligate of energy, but he soon learned that there were at least four of the floating fortresses engaged in the undertaking. Occasionally the two creations then attacking were replaced by two precisely similar structures, presumably to return to Chlora in order to renew their supplies of the substance, whatever it was, from the atomic disintegration of which they derived their incomprehensible power.

And slowly, contesting stubbornly and bitterly every foot of ground lost, the forces of Valeron were beaten back under the relentless, never-ceasing attack of the Chloran monstrosities—back and ever back toward their central dome as ring after ring of the outlying fortifications slagged down into that turbulently seething, that incandescently flaming lake of boiling lava.

Valeron was making her last stand. Her back was against the wall. The steadily contracting ring of Chloran force had been driven inward until only one thin line of fortified works lay between it and the great dome covering the city itself. Within a week at most, perhaps within days, that voracious flood of lava would lick into and would dissolve that last line of defense. The what of Valeron?

All the scientists of the planet had toiled and had studied, day and night, but to no avail. Each new device developed to halt the march of the encroaching constricting band of destruction had been nullified in the instant of its first trial.

"They must know every move we make, to block us so promptly," Quedrin Radnor had mused one day. "Since they certainly have no visiray viewpoints of material substance within our dome, they must be able to operate a spy ray using only the narrow gravity band, a thing we have never been able to accomplish. If they can project such viewpoints of pure force through such a narrow band, may they not be able to project a full materialization and thus destroy us? But, no, that band is—must be—altogether too narrow for that."

Stirred by these thoughts he had built detectors to announce the appearance of any nongravitational forces in the gravity band and had learned that his fears were only too well founded. While the enemy could not project through the open band any forces sufficiently powerful to do any material damage, they were thus in position to forestall any move which the men of Valeron made to ward off their inexorably approaching doom.

Far beneath the surface of the ground, in a room which was not only sealed but was surrounded with every possible safeguard, nine men sat at a long table, the Bardyle at its head.

" ... and nothing can be done?" the coordinator was asking. "There is no possible way of protecting the edges of the screens?"

"None." Radnor's voice was flat, his face and body alike were eloquent of utter fatigue. He had driven himself to the point of collapse, and all his labor had proved useless. "Without solid anchorages we cannot hold them—as the ground is fused they give way. When the fused area reaches the dome the end will come. The outlets of our absorbers will also be fused, and with no possible method of dissipating the energy being continuously radiated into the dome we shall all die, practically instantaneously."

From SKYLARK OF VALERON by E. E. "Doc" Smith (1934)

(ed. note: still more space opera)

A WAILING signal interrupted the conversation and every Vorkul in the vast fleet coiled even more tightly about his bars, for the real battle was about to begin. The city of the hexans lay before them, all her gigantic forces mustered to repel the first real invasion of her long and warlike history. Mile after mile it extended, an orderly labyrinth of spherical buildings arranged in vast interlocking series of concentric circles—a city of such size that only a small part of it was visible, even to the infra-red vision of the Vorkulians. Apparently the city was unprotected, having not even a wall. Outward from the low, rounded houses of the city's edge there reached a wide and verdant plain, which was separated from the jungle by a narrow moat of shimmering liquid—a liquid of such dire potency that across it, even those frightful growths could neither leap nor creep.

But as the Vorkulian phalanx approached—now shooting forward and upward with maximum acceleration, screaming bolts of energy flaming out for miles behind each heptagon as the full power of its generators was unleashed—it was made clear that the homeland of the hexans was far from unprotected. The verdant plain disappeared in a blast of radiance, revealing a transparent surface, through which could be seen masses of machinery filling level below level, deep into the ground as far as the eye could reach; and from the bright liquid of the girdling moat there shot vertically upward a coruscantly refulgent band of intense yellow luminescence. These were the hexan defences, heretofore invulnerable and invincible. Against them any ordinary warcraft, equipped with ordinary weapons of offense, would have been as pitifully impotent as a naked baby attacking a battleship. But now those defenses were being challenged by no ordinary craft; it had taken the mightiest intellects of Vorkulia two long lifetimes to evolve the awful engine of destruction which was hurling itself forward and upward with an already terrific and constantly increasing speed.

Onward and upward flashed the gigantic duplex cone, its entire whirling mass laced and latticed together—into one mammoth unit by green tractor beams and red pressors. These tension and compression members, of unheard-of power, made of the whole fleet of three hundred forty-three fortresses a single stupendous structure—a structure with all the strength and symmetry of a cantilever truss! Straight through that wall of yellow vibrations the vast truss drove, green walls flaming blue defiance as the absorbers overloaded; its doubly braced tip rearing upward, into and beyond the vertical as it shot through that searing yellow wall. Simultaneously from each heptagon there flamed downward a green shaft of radiance, so that the whole immense circle of the cone's mouth was one solid tractor beam, fastening upon and holding in an unbreakable grip mile upon mile of the hexan earthworks.

Practically irresistible force and supposedly immovable object! Every loose article in every heptagon had long since been stored in its individual shockproof compartment, and now every Vorkul coiled his entire body in fierce clasp about mighty horizontal bars: for the entire kinetic energy of the untold millions of tons of mass comprising the cone, at the terrific measure of its highest possible velocity, was to be hurled upon those unbreakable linkages of force which bound the trussed aggregation of Vorkulian fortresses to the deeply buried intrenchments of the hexans. The gigantic composite tractor beam snapped on and held. Inconceivably powerful as that beam was, it stretched a trifle under the incomprehensible momentum of those prodigious masses of metal, almost halted in their terrific flight. But the war-cone was not quite halted; the calculations of the Vorkulian scientists had been accurate. No possible artificial structure, and but few natural ones—in practice maneuvers entire mountains had been lifted and hurled for miles through the air—could have withstood the incredible violence of that lunging, twisting, upheaving impact. Lifted bodily by that impalpable hawser of force and cruelly wrenched and twisted by its enormous couple of angular momentum, the hexan works came up out of the ground as a waterpipe comes up in the teeth of a power shovel. The ground trembled and rocked and boulders, fragments of concrete masonry, and masses of metal flew in all directions as that city-encircling conduit of diabolical machinery was torn from its bed.

A PORTION of that conduit fully thirty miles in length was in the air, a twisted, flaming inferno of wrecked generators, exploding ammunition, and broken and short-circuited high-tension leads before the hexans could themselves cut it and thus save the remainder of their fortifications. With resounding crashes, the structure parted at the weakened points, the furious upheaval stopped and, the tractor beams shut off, the shattered, smoking, erupting mass of wreckage fell in clashing, grinding ruin upon the city.

The enormous duplex cone of the Vorkuls did not attempt to repeat the maneuver, but divided into two single cones, one of which darted toward each point of rupture. There, upon the broken and unprotected ends of the hexan cordon, their points of attack lay: theirs the task to eat along that annular fortress, no matter what the opposition might bring to bear—to channel in its place a furrow of devastation until the two cones, their work complete, should meet at the opposite edge of the city. Then what was left of the cones would separate into individual heptagons, which would so systematically blast every hexan thing into nothingness as to make certain that never again would they resume their insensate attacks upon the Vorkuls. Having counted the cost and being grimly ready to pay it, the implacable attackers hurled themselves upon their objectives.

Here were no feeble spheres of space, commanding only the limited energies transmitted to their small receptors through the ether. Instead there were all the offensive and defensive weapons developed by hundreds of generations of warrior-scientists; wielding all the incalculable power capable of being produced by the massed generators of a mighty nation. But for the breach opened in the circle by the irresistible surprise attack, they would have been invulnerable, and, hampered as they were by the defenseless ends of what should have been an endless ring, the hexans took heavy toll.

The heptagons, massive and solidly braced as they were, and anchored by tractor rays as well, shuddered and trembled throughout their mighty frames under the impact of fiercely driven pressor beams. Sullenly radiant green wall-screens flared brighter and brighter as the Vorkulian absorbers and dissipators, mighty as they were, continued more and more to overload; for there were being directed against them beams from the entire remaining circumference of the stronghold. Every deadly frequency and emanation known to the fiendish hexan intellect, backed by the full power of the city, was poured out against the invaders in sizzling shrieking bars, bands, and planes of frenzied incandescence. Nor was vibratory destruction alone. Armor-piercing projectiles of enormous size and weight were hurled—diamond-hard, drill-headed projectiles which clung and bored upon impact. High-explosive shells, canisters of gas, and the frightful aerial bombs and radio-dirigible torpedoes of highly scientific war—all were thrown with lavish hand, as fast as the projectors could be served. But thrust for thrust, ray for ray, projectile for massive projectile, the Brobdingnagian creations of the Vorkuls gave back to the hexans.

The material lining of the ghastly moat was the only substance capable of resisting the action of its contents, and now, that lining destroyed by the uprooting of the fortress, that corrosive, brilliantly mobile liquid cascaded down in to the trough and added its hellish contribution to the furious scene. For whatever that devouring fluid touched flared into yellow flame, gave off clouds of lurid, strangling vapor, and disappeared. But through yellow haze, through blasting frequencies, through clouds of poisonous gas, through rain of metal and through storm of explosive the two cones ground implacably onward, their every offensive weapon centered upon the fast-receding exposed ends of the hexan fortress. Their bombs and torpedoes ripped and tore into the structure beneath the invulnerable shield and exploded, demolishing and hurling aside like straws, the walls, projectors, hexads and vast mountains of earth. Their terrible rays bored in, softening, fusing, volatilizing metal, short-circuiting connections, destroying life far ahead of the point of attack; and, drawn along by the relentlessly creeping composite tractor beam, there progressed around the circumference of the hexan city two veritable Saturnalia of destruction—uninterrupted, cataclysmic detonations of sound and sizzling, shrieking, multi-colored displays of pyrotechnic incandescence combining to form a spectacle of violence incredible.

But the heptagons could not absorb nor radiate indefinitely those torrents of energy, and soon one greenishly incandescent screen went down. Giant shells pierced the green metal walls, giant beams of force fused and consumed them. Faster and faster the huge heptagon became a shapeless, flowing mass, its metal dripping away in flaming gouts of brilliance; then it disappeared utterly in one terrific blast as some probing enemy ray reached a vital part. The cone did not pause nor waver. Many of its component units would go down, but it would go on—and on and on until every hexan trace had disappeared or until the last Vorkulian heptagon had been annihilated.

From SPACEHOUNDS OF IPC by E. E. "Doc" Smith (1931)

      Major General Eunan Charles Gorman looked up as another incoming gravitic round struck the perimeter shields with piercing thunder. The deck of the headquarters dome rocked with the impact, and both lights and display monitors dimmed and flickered as the screens strained to dissipate the surge of energy grounding out of the sky. It wouldn’t be long before the screens overloaded; when that happened, the defense of Mike-Red would come to an abrupt and pyrotechnic end.
     The large three-view in the center of the HQ dome currently showed the Marine beachhead—a slender oval five kilometers long and perhaps two wide, sheltered beneath the shimmering hemisphere of an energy shield array six kilometers across. They were well-situated on high, rocky ground, but the terrain offered few advantages at the moment. The enemy was attempting to burn them out, pounding at the shield with nukes and heavy artillery, some fired from space, some fired from emplacements surrounding the beachhead and as far as a hundred kilometers away. All of the ground immediately around the Marine position was charred and lifeless, the sand fused into black, steaming glass. Incoming fire was so heavy the Marines could not lower the screen even for the instant required for a counter-battery reply.
     That was the worst of it—having to sit here day after day taking this hammering, unable to shoot back.

     Commander Marissa Allyn brought her gravfighter into a flat, high-speed trajectory, hurtling low above the surface. The orange ground cover gave way in a flash of speed-blurred motion to bare rock. The surface for fifty kilometers around the Marine perimeter was charred black or, in places, transformed into vast patches of fused glass. Over the past weeks, since the Turusch had brought the Marine base under attack, hundreds of nuclear warheads had detonated against the Marine shields, along with thousands of charged particle beams. The equivalent of miniature suns had burned against that landscape, charring it, in places turning sand to molten glass.

     Energy screens and shields were three-dimensional projections of spacial distortion, an effect based on the projection of gravitational distortion used in space drives. Shields reflected incoming traffic, while screens absorbed and stored the released energy.
     While screens were useful in relatively low-energy combat zones, they could be overloaded by nukes, and they weren’t good at stopping solid projectiles like missiles or high-energy KK rounds. With shields, incoming beams, missiles, and radiation were twisted through 180 degrees by the sharp and extremely tight curvature of space. Warheads and incoming projectiles were vaporized when they folded back into themselves, beams redirected outward in a spray of defocused energy. Warheads detonating just outside the area of warped space had both radiation and shock wave redirected outward.
     As the ground around the outside of the perimeter became molten, however, some heat began leaking through at the shield’s base faster than heat-sink dissipaters could cool the ground. When the projectors laid out on the ground along the perimeter began sinking into patches of liquid rock, they failed. The enemy’s strategy in a bombardment like the one hammering Mike-Red was to overload the dissipaters and destroy the projectors.
     The Marines were using shields and screens in an attempt to stay ahead of the bombardment, with banks of portable dissipater units running nonstop in the ongoing fight to keep the ground solid.

     It was a fight they were losing.

     One reason the beachhead had been set up on a rocky ridgetop was that molten rock tended to flow downhill, not up into the perimeter and the shield projectors. Repeated shocks against the lower slopes of the ridge, however, were threatening to undermine the perimeter. Gorman had already given orders to set out two replacement projectors, for number five and number six, placing them back a hundred meters as the ground sagged and crumbled beneath the originals.

     Eventually, enemy fire would eat away the entire hill.

From EARTH STRIKE by William H. Keith, Jr. (under pseudonym Ian Douglas) (2010)


Planetary Attack may occur when one player has warships in a star hex which contains another player's colonized planet and that colony possesses Planetary Missile Bases (MB) and/or Advanced Missile Bases (AMB). Planetary Attack may occur only after all Ship/Ship Combat in a player's turn has ended. A colony is conquered when all of its defenses (missile bases) cease to exist and the attacker has a warship occupying that star hex. Warship barrage fire and missile base fire is considered to occur simultaneously. All warships and missile bases existing at the beginning of a Fire Turn may fire in that Fire Turn. A colony with a PFS is unconquerable. Any ship attacking a Planetary Force Screen (PFS) is automatically destroyed.

7.14 The colonist player may now announce the destruction of Industrial Units and/or Robotic Industrial Units (RIU) that are in excess of the Population/Industry ratio of one million population to one IU. The colonist player does this to prevent industrial capacity from falling into enemy hands. It is a last resort if the colonist player does not expect to re-conquer the colony in a reasonable amount of time. The colonist player may declare excess industrial capacity destroyed only if some colony missile bases still exist at this point in the Fire Turn sequence. If the colony has been conquered during this Fire Turn, as defined next, he may not exercise this option.

7.1.5 Planetary Attack on the contested colony is over for this Fire Turn if all the attacking players' warships are destroyed, or if all colony missile bases have been destroyed, and the colony conquered, or the attacking player declares the attack ended. The colony is not conquered if all remaining warships and missile bases were destroyed during the same Fire Turn. If there is more than one colonized planet in the con tested star hex, the attacking player may attack them separately or together or alternate his attacks at will. Planetary Attack is ended in the contested star hex if the above stated conditions apply to all colonies and warships in that star hex.

7.2.8 The Conqueror may destroy the population and Industrial Units of a conquered colony on a one to one basis. The population and industry destruction occurs during the Planetary Attack step of a Player Turn. Each type of warship the conquering player has in the conquered planet's star hex may destroy on the following basis:

  • For each Escort warship (ESC), 1 million population and 1 IU.
  • For each Attack warship (ATK), 3 million population and 3 IU.
  • For each Dreadnought warship (DN), 5 million population and 5 IU.

Each warship may destroy the above amounts only once during the Planetary Attack step of a Player Turn.

7.2.9 If a colonized planet's population consisting of 10 million or more colonists has been destroyed by an opponent's warships, that planet is rendered uninhabitable by any means for the rest of the game and is so marked on the Player Record Sheet. This uninhabitable Planet does not count any points toward winning, regardless of its original habitability type.

From game STELLAR CONQUEST by Howard Thompson (1975)

Deep Down Defenses

If the inhabitants of the planet lack handwavium force fields, and the besiegers have no shortage of bombardment weapons, sooner or later the planet people are going to have to resort to living underground. The more frightful the bombardment, the deeper they will have to dig.

This is why in the real world the US NORAD Cheyenne Mountain Complex is built under six hundred meters of solid granite. Proof against EMP, and the blast doors are rated to withstand a 30 megaton thermonuclear explosion as close as two kilometers.

In the 1955 movie This Island Earth, the planets Metaluna and Zagon are at war. Metaluna's surface has been laid to waste by Zagonian asteroid bombardment. The Metaluna's cities are now all underground, but even then they are planning to seize and relocate to Planet Terra before Metaluna becomes totally uninhabitable.

In the 1974 anime series Space Battleship Yamato the warlike Gamilas have devastated Terra by a continual asteroid bombardment. But these asteroids are radioactive. Even though the people of Terra have retreated underground, the radiation is slowly seeping downward. The people of Terra have about one year left to live before the radiation kills them. Lucky for them they receive help from a certain Queen Starsha of the planet Iscandar in the Greater Magellanic Cloud.

The queen offers a wonderful machine that will cleanse Terra of all the radiation. The catch is that the Terrans have to travel to the GMC go fetch it. Starsha hopefully gives them blueprints for a faster-than-light-drive/unreasonably-powerful-Kzinti-Lesson, but the Terrans have to build the drive and the ship to house it.

Lucky for them, the asteroid bombardment has conveniently evaporated the seven seas, exposing all the historical shipwrecks in general, and the wreck of the 1940 battleship Yamato in particular. There is not enough underground space to build a huge spacecraft, but the Yamato is reasonably large and strong enough to be converted. The Terran secretly tunnel underneath it and covertly rebuilt it, so as to not tip off the Gamilas.


While any Eddorian-could, if it chose, assume the form of a man, they were in no sense manlike. Nor, since the term implies a softness and a lack of organization, can they be described as being amoeboid. They were both versatile and variant. Each Eddorian changed, not only its shape, but also its texture, in accordance with the requirements of the moment. Each produced extruded members whenever and wherever it needed them; members uniquely appropriate to the task then in work. If hardness was indicated, the members were hard; if softness, they were soft. Small or large, rigid or flexible; joined or tentacular — all one. Filaments or cables; fingers or feet; needles or mauls — equally simple. One thought and the body fitted the job.

They were asexual: sexless to a degree unapproached by any form of Tellurian life higher than the yeasts. They were not merely hermaphroditic, nor androgynous, nor parthenogenetic. They were completely without sex. They were also, to all intents and purposes and except for death by violence, immortal. For each Eddorian, as its mind approached the stagnation of saturation after a lifetime of millions of years, simply divided into two new-old beings. New in capacity and in zest; old in ability and in, power, since each of the two “children” possessed in toto the knowledge and the memories of their one “parent”.

And if it is difficult to describe in words the physical aspects of the Eddorians, it is virtually impossible to write or to draw, in any symbology of Civilization, a true picture of an Eddorian’s — any Eddorian’s mind. They were intolerant, domineering, rapacious, insatiable, cold, callous, and brutal. They were keen, capable, persevering, analytical, and efficient. They had no trace of any of the softer emotions or sensibilities possessed by races adherent to Civilization. No Eddorian ever had anything even remotely resembling a sense of humor.

While not essentially bloodthirsty—that is, not loving bloodshed for its own sweet sake—they were no more averse to blood-letting than they were in favor of it. Any amount of killing which would or which might advance an Eddorian toward his goal was commendable; useless slaughter was frowned upon, not because it was slaughter, but because it was useless and hence inefficient.

And, instead of the multiplicity of goals sought by the various entities of any race of Civilization, each and every Eddorian had only one. The same one: power. Power! P-O-W-E-R!!

Since Eddore was peopled originally by various races, perhaps as similar to each other as are the various human races of Earth, it is understandable that the early history of the planet while it was still in its own space, that is, was one of continuous and ages-long war. And, since war always was and probably always will be linked solidly to technological advancement, the race now known simply as “The Eddorians” became technologists supreme. All other races disappeared. So did all other forms of life, however lowly, which interfered in any way with the Masters of the Planet.

Then, all racial opposition liquidated and overmastering lust as unquenched as ever, the surviving Eddorians fought among themselves: “push-button” wars employing engines of destruction against which the only possible defense was a fantastic thickness of planetary bedrock.

From TRIPLANETARY by E. E. "Doc" Smith (1948)

      Now they had reached the border of a great sea, where a huge mountain range seemed to run off into the water in a series of islands. Their escort had taken the lead, and was hovering over one of the islands now.
     Suddenly Aarn gasped, for the tiny blazing sun and the deep violet sky was obscured by a mist that grew more and more dense, a rapidly rising, vapory cloud that swept up from the sea. In a minute the entire district was veiled in an impenetrable fog. Even the television was badly hampered, so badly it could show but a few hundred feet ahead as they followed the leading ship closely. Auto Rayl was silent, intently watching the screen.
     The destroyer ahead was making straight for the largest of the near-by islands. And, as they neared it, a peninsula a quarter of a mile long slid silently out to sea and sank beneath the waves. A great metal-lined bore was revealed, and instantly the destroyer dropped into it. The Sunbeam was directly behind. That bore was an oval cylinder, five hundred feet wide, and two hundred long, and extending down beyond sight, curving into the bowels of the planet.
     The lighted bore was suddenly darkened by the settling of the great rocky lid back in place.
     The tunnel had straightened out. Now, suddenly, they came upon a great factory, a huge, brightly lighted under ground workshop. Gigantic forms were in construction off across the big, pillared cavern.

From THE MIGHTIEST MACHINE by John W. Campbell jr. (1934)

      “That big sea,” said Warren briefly. “There’s a city under it!” exclaimed Putney. “That’s the place for a city! No heat rays would ever reach them there, no bombs even. Why aren’t all the cities under water?”
     “Not enough room probably. Also not all their eggs in one basket. This is probably the capital.”
     The planes were slowing now, and as they neared a low range of mountains that ran down to the lake, they stopped. They hovered in tight circles above the mountains for a few moments, then suddenly one entire hill, nearly a half-thousand feet in height, and fully 1000 long, slid serenely out into the lake, seemingly floating on the water. Beneath it was a vast cavern opening. The giant ships sank into it three abreast, while the smaller ships sank down whole fleets side by side.
     Warren was already in the cavern. It led straight down for half a mile, turned back toward the lake for a mile, then straight down for another mile. At the bottom were titanic lock gates of solid metal at least fifty feet thick set in great grooves cut in the living rock. The surface toward the city did not, at present, touch the surface of the grooves. Both were lined with thick layers of some dark substance, evidently similar to rubber. A quarter of a mile further on was a similar titanic set of gates. And with the first gates the lighting began. Heretofore great searchlights on the ships had illuminated the passages, for scarcely had they passed the mouth of the cavern when the mountain began moving back into place.
     “There’s one sure thing — these fellows have some source of power that beats anything earth had two years ago. Earth could never have dug this channel, they could never have moved that mountain around, and they’d have been plumb out of luck if anything like those ships came after them. Wonder what it is?”
     The ships ahead began slowing to an even lower rate, turned an abrupt corner, and the Terrestrians suddenly came into a blaze of brilliant. lights. A huge cavern widened out from the tunnel, a gigantic place with a dozen levels of metal floors on which, one by one, the planes began to settle. Thaen touched Warren’s shoulder and pointed to the topmost one. “Yuarn,” he said.
     Warren nodded. “I don’t see why this doesn’t fall in on them.”
     “I’m beginning to. Don’t go near those columns of light. I think the light just marks out the beam of force — yes, look at that magnetometer. A powerful beam. Probably they have projectors on the cavern floor, and on the various floors, and on the roof, that distribute the pressure. Look — see how that beam there widens at the middle — I’ll be willing to bet anything that’s how they drive their ships. Nasty weapon it would make too, if you didn’t have any magnetic defense field. Just touch one of those beams with a weak field and see what happens.”
     Warren set some controls, and pulled a lever back gently. The surrounding columns of light swayed gently away from the ship, then gently toward him, bending at the joints. “Magnetic,” he nodded.

     A picture of an arid, dry plain swam into being on the screen of mist (movie projector screen). Unlike an earthly moving picture it grew swiftly from a spiral till it filled the entire screen with a round picture with a peculiar suggestion of depth.
     There was nothing but the level plain, and the clear violet sky with occasional clouds floating high in it. But somewhere a faint, heavy hum began to come into being; it grew till it was a majestic, full-throated roar echoing through all space.
     As they watched, a fleet of giant battle planes swam into view from somewhere behind, moving onward and upward at an unbelievable speed. They climbed at an angle of forty-five degrees, yet their wings tilted back no more than thirty degrees. Some force other than pure air-lift was raising them. So swiftly they mounted that in moments they were out of sight.
     Suddenly the ground cracked, broke, and a ring of squat, hemispherical metal domes pushed their way up through the sand. Several seconds passed, then from one, then another, broke a great flare of electric-blue fire that reached fanshaped to the sky, bent, and intermingled in a dome of solid fire above all. It fluctuated, wavered, twisted, and then steadied after a moment to a solid, motionless sheet. A constant, steady hum echoed through the great cavern.
     Something materialized on the screen, a black dot high, high in the violet sky. It grew with accelerating speed, expanding rapidly to a torpedo-shaped body ten feet long, three in diameter, ending in a finned tail that kept it whirling with terrific speed, a gyroscopic missile that would maintain its orientation against any deflecting force. Half a mile from the ground a stream of fire issued from it, and the giant bomb leapt forward with speed that must have reached miles a second.
     At the last instant it swerved violently, landing finally in the exact center of the dome of blue fire. A single stupendous flash of light, a titanic explosion sharp as the crack of a rifle, and it was gone.
     It was merely a sighting shot. A hundred black dots appeared magically, and as they came into being, and grew from somewhere in the far reaches of that violet sky, blue-glowing cones of dim radiance reached up to them. They staggered, twisted in their paths as the beams touched them. Some jerked violently aside. All slowed visibly, and became red, many released their explosive energies harmlessly on the air, but a majority rained down on the protecting dome of fire.
     Strangely, none seemed directed at the center of the dome, the force beams seemed engaged in directing them there. Most fell toward the edge of the protecting ring.
     Other dots were appearing far above now. The planes were descending again, and now accompanied with long, slim ships, shaped like pencils pointed at each end. Lashing beams smashed out between them. The faintly glowing force-beams from the ships, long tubes of hazy light, some other beam, twin pipes of brilliant light that started from each other, and curved inward to meet at their object in a constant, terrific display of lightning. A dozen planes attacked each ship, the ships seemed content to sink slowly downward, dropping their gigantic bombs, and firing tiny, explosive shells toward the dodging planes.
     The planes were not dodging successfully apparently, for a constant and growing rain of broken metal began to fall. From each of the hundred pencil-ships a ray reached out presently, something dim and half seen that exploded into a point of incredible incandescence if it touched a plane.
     As at a signal, the giant attacking planes winged over suddenly, pointed their noses toward the planet, and descended in a terrific, shrieking power drive that must have raised their speed to nearly a mile a second. Their wings were folded into the ships in some manner, till only a knife edge projected from the fuselage. The great planes twisted and weaved as they shot downward, avoiding rays that sliced after them. They turned, leveled off, and streaked across the plain in a dodging course at a rate that carried them beyond the horizon in seconds.
     The pencil-ships were not left to come on unhindered, for each great plane ship had spewed forth a great fleet of tiny midges that swarmed in darting, flitting motion about the ships, discharging brief bursts of that twin explosive electric ray. But somehow the ray always seemed to explode just short of the ships, leaving them unscathed.
     Some signal was given. The hundreds of tiny ships all darted suddenly toward one of the pencil-ships, every ray burst forth simultaneously in a single blinding sheet of flame — and the pencil-ship was falling, white-hot wreckage. The midges scattered themselves as though fragments of an exploding bomb. Vengeful heat-rays lashed across the sky where they had been seconds before. The score must have been half a hundred — but by far the greater number escaped.
     The battle was progressing on a level now, nearly fifty miles above the city evidently, for some telescopic device had been attached to the camera. Ships and midges circled steadily for the advantage.
     Again the concerted rush — again white-hot wreckage descended streaming from the pencil-ship, and two score more of the midges followed it.
     “The ships have some sort of screen — if the planes can get enough power over, the screen fails — when the ships don’t have to use power for their screen, they can work those heat-rays,” said Warren hastily. “The ships will win — too many.”
     There was a sudden shift in the position of the pencil-ships. One rose half a mile above the rest, while the others set up a barrage of their heat rays about it, protecting it. The midges seemed suddenly to concentrate on attacking that ship, for fully a third of them rose to it, and poured their weapons against it — most of them to fall mangled wreckage.
     For an instant the ship seemed unguarded. Then, from bow and stern, broke two new rays. They moved in a curve if the ship spun rapidly, their range was less than a quarter of a mile, but they seemed to stretch a web of force between them and around them that swept the midges from the sky like some gigantic broom. Only near the enemy ships were the planes safe, from this weapon, and there the heat-rays reached them.
     The midges folded their wings and, like the giant planes, shot planet-ward with terrific speed. Not a full hundred reached the surface. The pencil-ships descended in massed, close-packed formation, majestically and slowly, toward the glowing dome of fire. At ten miles the forts went into action. For a single second, every one of the fan beams snapped out, to snap on as concentrated pipes of radiance smashing their way to the massed enemy ships. A wave of fire washed over the formation, it flowed like some squirted liquid, striking a solid glass plate. But it was like an acid, for it began eating holes that showed red against the blue flame, holes that expanded as some half dozen beams concentrated instantly on it — and a ship disappeared in flaming destruction beyond.
     But presently this eating of holes stopped, the holes grew fewer, and smaller, ships avoided them in the meantime, and they hung motionless over the city.
     Hours must have passed. The scene was at night, suddenly, and the ships showed brilliantly outlined by the wash of electric fire, the heavens were illuminated by the great, bright stars of this world, but they were overcast now, clouds were gathering.
     The ships were no longer massed, their formation was a circle with a hub and spokes. But only half the ships were so engaged. The rest seemed moving about freely behind this shield. They began to concentrate above the hub, and the ships of the hub rose to join them. Blue beams began to reach from one to another, till all the ships were linked in a single network of power beams.
     The center ship hovered over the center of the shield. A mistiness grew suddenly before it, a spinning misty globe of blue light. It attained size, then suddenly broke free, and went spinning erratically downward. It ate a hole through the shield. It drank up the blue electric flame on the other side, and grew fat on it. It jerked its way down and to one side. It acted like a light ball suspended in a jet of air. Suddenly a particularly violent jerk led it into one of the great beams. Instantly, with the speed of light, it followed that beam back to its source, puffed softly as it struck the dome-fort, and bounced aloft. The fort was a heap of powdery ash.
     Frantic magnetic beams were jerking at it; they could deflect it when it moved, but only served to make its erratic motion more so. And another sphere was falling, jerking about like the first.
     In minutes the last of the forts were gone. The enemy ships came slowly downward, cautiously. The spheres seemed repelled by them, and rolled swiftly away, out across the plane, moving erratically as ever, and every touch left a great, powdery scar, but every touch made them smaller.
     The ships were pouring their heat beams into the rock. It was day once more, and a cauldron of molten rock half a mile across bubbled gently. It was night again — the cauldron of rock was three miles across. Day found it fully four, and bubbling gently.
     The scene on the screen of mist vanished. It was replaced by a scene in a great subterranean city. Men, women, and children were hurrying about on moving ways, suspended on spidery bridges that spanned the great lighted tunnels. Each wall of the tunnel here was a great apartment house, and the great tunnels must have been a hundred and fifty feet tall, and fifty wide. The scene was at a “cube” — the three-dimensional equivalent of a city square, where four great tunnels intersected. Everyone seemed to be leaving. The reason was obvious. Above the spider-work bridges, above the glowing magnetic columns that supported the rock pressure above, a slow smoke was originating, and falling downward. The rock became dull red while they watched. The last hurrying people looked back over their shoulders with frightened faces.
     Suddenly one of the great magnetic columns began to wobble erratically. It twisted, the upper section broadened, and seemed to be trying to slide off the lower. It did, its beam a cone that sharply deflected the four surrounding beams till they too began to wobble. The dull red rock was brightening. The beams were all spreading now; the first to fail suddenly went out as an explosion wrecked the projector. A great crack appeared in the rock, and with a terrific roar of sound the whole roof split wide. A river of molten rock came pouring through. The spider-work bridges and ways vanished in a puff of smoke and a brief sparkle of fire. A wall of white-hot rock moved rapidly toward the screen. The camera swayed, the picture went out of focus, and suddenly a plume obscured the screen.
     An instant later the camera was looking down the tunnel from a distant station. The wave of rock was moving more slowly, cooled by surrounding rock, and by the great refrigerating plants that must have been cooling the city. A huge line of pipe had been hastily laid, and was spouting a sparkling blue liquid that hissed instantly into invisibility as it struck the rock — which cooled it. A dike was being built, a dike of frozen rock.
     It was useless. The roof of the tunnel itself began to glow, and the pipes were turned on it. The Niagara of lava still flowing in from the original break overflowed the dike, and rolled on.
     The city was doomed.
     The screen went blank in a burst of flame at that moment, and stayed blank.

From THE SPACE BEYOND by John W. Campbell, Jr. (1976)

(ed note: Alakars are Warbots, soldiers wearing ultra-high-tech powered armor mostly made out of forcefields and nanotechnology. Steel pimples are free flying auxiliary units of the armor, about the size of a golf ball. Amorphoid is what we now call "programmable matter", smart materials constructed out of nanotechnology which can alter its forms and functions on command. Most machines and tools are made out of amorphoid.)

Antares, who had always seemed to have the last thing to say insofar as weapons advances were concerned, finally sent a squad of Ultimate Alakars onto the field of war.

The Alakar himself wore no weapons, though he carried a few hand weapons of negligible presence (mostly fashioned from Link), wore no helmet and had six steel pimples, which performed all the functions of the helmet, as well as being able to operate as battlecrafts. The Alakar, upon landing on a planet, which had not been invaded, would immediately alert the civilians to go to the public shelters hundreds of miles beneath the planetary crust and take all personal valuables with them. They were given twenty-four hours, but during this time, since the Alakar was almost sure to be under attack, he would certainly be occupied. His steel pimples would head for the nearest masses of amorphoid, often automobiles and private spacecraft, and perform virus-function. Whatever the amorphoid had been previously would be erased; the pimples would realign and combine all available amorphoid into great robot fortresses, fleets of battlecrafts and orbiting platforms, and would infect normal metals with amorphic domain, causing entire communications networks to start converting into amorphoid weapons. If it went on mainly unchecked, within fifty hours of commence-attack, the military command centers buried in the centers of the planets could expect their control panels to swim like quicksilver and turn into atomic bombs.

The planetary defenses would initiate their own amorphic conversions, trying to fight back, and would cause the comm networks to fight back at ground level. Flotillas of planetary steel pimples would commandeer as much amorphoid as possible, until the entire war began to resemble the attack of a viral disease upon a protoplasmic organism. If the planetary defense won, the Alakar was killed or forced to retreat, and the mass-computer would return every bit of registered amorphoid on the surface to its original state (unregistered amorphoid, such as kitchen appliances, generally kept firing away until told to desist. Registered amorphoid, which had a certain key-pattern built in, instantly reverted).

If the Alakar won, the same thing would be done, except that he would now control the planet and invite his forces into orbit. Since the governments of Antares and the TOSS were very similar, in basic policies, the civilians rarely cared too much who held the upper hand, so long as they were not too often changed.

Naturally, this being a war, damage was done. A wrecked city stayed quite wrecked, though there was rarely any loss of life. But recovery from an attack took several years, and when Antares finally bested the TOSS, they found that they had a tremendous financial responsibility to rebuild what they had undone.

From THE WARBOTS by Larry Todd (1968)
Note that the GALAXY magazine and the Bodyarmor 2000 articles have totally different artwork

Surface Defenses

In addition to large planetary forts, there may be scattered anti-spacecraft weapons sited all over the planet. The main difference is these have no real protection except being very good at hiding. Instead of armor or magic force fields, they are either one-shot sacrificial weapons or capable of frantically scuttling away after they give away their position. Or they are weaponized spacecraft launching facilities that the enemy wants or needs to capture intact so they are loath to damage it.

Because as soon as a ground (or sea) based gun opens fire on an enemy ship in orbit, the enemy is going to plaster the entire area with ortillery.

If you have sufficient stealth technology, it might be a good idea to put some planetary defensive weapons inside submarines. This made good sense back in the days of Mutual Assured Destruction, but nowadays orbital observation satellites have made it much harder for submarines to hide. Be aware though that their stealth is destroyed the instant they fire their weapons, and the attackers in orbit will lob a nuclear depth-charge that will crush the submarine like an eggshell. US Navy Ohio-class submarines carry 24 missiles, a planetary defense submarine would probably be carrying a similar amount. The PD sub would be well-advised to launch all of its missiles at once, and preferably the sub should be a remotely controlled drone.

In the 1955 Operation Wigwam test, the US military discovered that a 30 kiloton nuclear depth charge could kill a modern submarine with a radius of a bit more than a mile.

Like planetary fortresses, surface defences are at a disadvantage with respect to hostile spacecraft in orbit due to the gravity gauge.

Rick Robinson is of the opinion that the gravity gauge is not quite as one-sided as it appears. In an essay entitled Space Warfare I - The Gravity Well he makes his case. The main point is that the orbiting invading spacecraft have nowhere to hide, while the defending ground units can hide in the underbrush.

Of course it is a bit easier to inflict damage on orbital person now that lasers have been invented. Keep in mind that if the planet in question has an atmosphere similar to Terra some laser wavelengths should be avoided.

And keep in mind that the defender's anti-orbit rocket also does not need a warhead, a bursting charge surrounded by nails and other shrapnel will do. The relative velocity between the more or less stationary cloud of shrapnel and the orbital speed of orbital person will do the rest. Orbit person will be riddled by shrapnel traveling at about 27,500 kilometers per hour (7,640 m/s) relative.


Twenty-three hundred kilometers to the west at Allansport, Sergeant Sherman White slapped the keys to launch three small solid rockets. They weren't very powerful birds, but they could be set up quickly, and they had the ability to loft a hundred kilos of tiny steel cubes to a hundred and forty kilometers. White had very good information on the Confederate satellite's ephemeris; he'd observed it for its past twenty orbits.

The target was invisible over the horizon when Sergeant White launched his interceptors. As it came overhead the small rockets had climbed to meet it. Their radar fuses sought the precise moment, then they exploded in a cloud of shot that rose as it spread. It continued to climb, halted, and began to fall back toward the ground. The satellite detected the attack and beeped alarms to its masters. Then it passed through the cloud at fourteen hundred meters per second relative to the shot.

Four of the steel cubes were in its path.

From SWORD AND SCEPTER by Jerry Pournelle (1973)

Traditionally, spacecraft attacking targets on a planetary surface are assumed to have a high-ground advantage, referred to by Heinlein as the “gravity gauge”.  This assumption, like many about space warfare is wrong for several reasons.  Firstly, a spacecraft in orbit is very vulnerable to ground-launched kinetics, which only need to intercept it to do lethal damage, as described in Section 8.  Second, the ground-based defenders are able to use the clutter of the planetary surface to hide their actions, while the attackers are clearly visible.  Lastly, the planet itself offers advantages in the construction of defenses that serve as a very powerful force multiplier for the defender.

The thought experiment that underlies the gravity gauge is two men, one at the bottom of a well, the other at the top, having a fight with rocks.  The man at the top has an obvious advantage.  However, like many analogies, this one has deep flaws.  The largest is a misunderstanding of orbital mechanics.  Because of the motion of the orbital craft, any projectiles that it launches must slow down before they can leave orbit, and in low orbit, the delta-V requirement can be significantly higher than is required for a defender’s projectile to reach the attacker.  The requirement depends heavily on the geometry of the situation, but it is outside the scope of this section.  For more details, see Section 12 and Space Weapons, Earth Wars.  A warhead is unnecessary for the defender’s weapons, as the target’s orbital velocity provides all the kinetic energy required for the job.  Another issue is that the rocket necessary for this type of mission is quite small.  An R-17 Scud-B can reach a maximum altitude of approximately 150 km with a warhead of 985 kg and a launch weight of 5,900 kg, providing a marginal capability against targets in very low orbit.  Another version, the Scud-C, is capable of reaching about 275 km, with a warhead of 600 kg, and a total launch weight of 6,400 kg.  The MGM-31A Pershing has an apogee of about 370 km, a warhead of 190 kg, and a launch weight of 4,655 kg.  All of these missiles date back to the 1960s or before, but, with the proper seeker systems, should be capable of engaging targets in low orbit.  Their warheads are rather heavier than would be optimal for engaging orbiting vessels, and lighter warheads could result in somewhat higher altitudes.  For higher-orbit engagements, something like the Pershing II (altitude ~885 km, warhead 400 kg, launch weight 7,490 kg) is probably called for.  Above that, the various ICBM-type systems would take over, with apogees in the range of 5,000 km.  

Note that all of these missiles have warheads which are far heavier than are required for direct-hit kill on any practical spacecraft.  There are two ways this fact can be exploited.  First, the warhead could be replaced by another stage carrying a smaller warhead and achieving a greater altitude.  This should be good for another few hundred kilometers altitude, depending on the size of the warhead available and the previous burnout velocity.  Second, the unitary warhead could be replaced by a bursting warhead, as described in Section 8.  A detailed treatment of this concept with regards to planetary defense can be found in the Appendix to Section 12 of Physics of Space Security.

The two extant missiles that most closely approximate what would be required of a low-altitude surface-to-orbit missile (SOM) are the THAAD (Terminal High-Altitude Area Defense) and the SM-3.  The current model of THAAD, the block 4, has a launch weight of 640 kg, a warhead of approximately 40 kg, and a maximum altitude between 150 and 200 km.  Later (and presumably heavier) models could improve the maximum altitude to as much as 500 km.  The SM-3, which is currently ship-launched, has a launch weight of 1500 kg, a warhead of 23 kg, and a maximum altitude of as much as 500 km.  Later versions are reported to be capable of 1000 km, and have launch weights of approximately 2600 kg.  Both missiles use the same sensor system, which is reportedly able to acquire targets (presumably ballistic missile warheads) at ranges above 300 km.

 The above missiles are listed to demonstrate that the basic physical requirements for an SOM are quite simple, and well within the grasp of current technology.  All of the listed missiles are fired off of trucks of some sort or another (with the exception of the SM-3, which does have a fixed land-based version).  THAAD itself is launched from a vehicle the size of a semi.  If a system was designed explicitly for the SOM role, it should be very easy to conceal the missiles in trucks until the time of launch, preventing the attackers from detecting and destroying them.  Even if the attackers can see everything clearly, if the trailer is self-contained and built to look like an ordinary semi-trailer, the attacker won’t be able to tell it apart from the millions of others in use.  

Extensive tracking and control stations will be unnecessary, as the ship in question will be moving in a more-or-less predictable orbit, and the missile will have enough homing capability to compensate for the imprecision.  Orbit determination is a well-established science.  All that is needed are a few measurements of time, observer’s position, and target bearing.  These sensors are even easier to hide then the missiles themselves, as they could be as simple as a sextant at dusk or dawn.  At night, it should be possible to detect the vessel, probably through radiator glow.  During the day, it is somewhat more difficult.  This suggests that a sun-synchronous orbit might be ideal for an attacking spacecraft, as dawn and dusk occur over the poles which are (presumably) largely uninhabited.  However, the same could be said of any polar orbit, and other conditions are likely to play a large part in attack orbit selection. The advantage of a sun-synchronous orbit is that the illumination angle beneath the spacecraft is nearly constant, but for a long-period orbit, the inclination is likely to be fairly low, potentially placing dawn over an inhabited area.  Geographical conditions are as likely to dictate the orbit as astrodynamical conditions, although the astrodynamic effects of attacking a non-Earth planet should not be discounted.  In some cases a sun-synchronous orbit will place the attacker over territory that he would rather avoid.  For example, a 24-hour sun-synchronous attack orbit aimed at a target in North America will spend a large amount of time over South America, a situation that is hardly idea.  For optimal results, attacks would be made in daylight, which gives the best conditions for the attacker’s sensors and the worst for those of the defender.

The obvious counter to the visibility of spacecraft is for the spacecraft to maneuver regularly, hopefully spoiling any shots the defender may take.  A burn of approximately 3 m/s in the prograde or retrograde direction in a 150 km Earth orbit will change the period of the orbit by 2 seconds and the semi-major axis by about 5 km.  What this means is that the spacecraft will arrive on the opposite side of the orbit either a second late or early respectively, and will be either 10 km above or 10 km below where it was supposed to be depending on which direction the burn was made in.  However, this is unlikely to be enough to spoil the attack.  If the missile seeker locks on 30 seconds out, a 330 m/s delta-V would be sufficient to compensate for the divergence, and it is quite likely that SOMs will be designed to frustrate such tactics.  So long as the change remains relatively small, the results above can be linearized, with a 12 m/s delta-V producing a 4-second change in arrival time, and a 40 km change in altitude.  Note that the divergence in position only occurs in the orbital plane.  The plane itself can be changed by a burn half an orbit away, but the spacecraft will still pass through a point opposite the location of the burn.  For out-of-plane dodging, it is best to burn a quarter-orbit away (three-quarters of an orbit will produce identical results).  Moving the ground-track 10 km in our 150 km Earth reference orbit will require 12.25 m/s of delta-V, significantly more than an equivalent amount of in-plane dodging.  To a first approximation, the dodge delta-V for a quarter-orbit burn will be approximately twice that required for a half-orbit burn.  All of this assumes the initial orbit is circular, and the delta-V is fairly small.  Finding values for larger burns will require elaborate computations, which are beyond the scope of available data.  The requirements for a given amount of miss distance will be somewhat lower at higher altitudes, but this must be balanced against the fact that at higher altitudes, the missile will probably have significantly more time between lock-on and impact, reducing the delta-V required to compensate.

Of course, this does not address the practicality of using regular maneuvers to frustrate missile attacks.  For a ship with a high-thrust drive, the limiting factor is delta-V, and this dodging scheme will require something like 0.4 m/s/km/hr. for half-orbit burns, or 0.8 m/s/km/hr. for quarter-orbit burns.  Over the long term, this would add up, needing 10 to 20 m/s/km/day.  This is vaguely practical for small miss generation, but small miss generation is easily compensated for by the missile.  Even a minimal estimate of a required miss distance of 10 km would need 100 to 200 m/s/day, which will get expensive if the siege drags on more than a few days. Low-thrust systems might be more effective, although the achievable miss distance will be limited by the acceleration of the spacecraft.

The exact altitude requirements for an SOM are actually quite difficult to figure out.  A missile will only be able to attack a target at its maximum altitude if the target in question passes directly over the launch site.  All of the numbers posted above are estimated maximum altitudes, and in practice the maximum altitudes will be some fraction of those listed.  The one use of the SM-3 for ASAT purposes was at an intercept altitude of about 250 km, and used an early model, putting the interception at about half of the theoretical maximum.  The missile used in the Chinese ASAT test has a theoretical altitude of somewhere between 1350 km and 1500 km, and was used against a target at an altitude of approximately 860 km.  All of these indicate that the maximum practical altitude for a missile is probably not much more than half of the maximum theoretically achievable, though 75% might be possible for a battery positioned close to an important target, where the enemy will pass almost directly overhead.  Air-launched ASAT systems, such as the ASM-135, are theoretically capable of achieving much more nearly 100% due to better positioning of the launching platform, although the only known air-launched ASAT test, the ASM-135 shot at the Solwind P78-1, occurred at an altitude of 555 km out of an apogee altitude of 1000 km.  The question then becomes what sort of altitudes will be required of an SOM system.  The ISS orbits at approximately 400 km, while most recon satellites orbit between 250 and 600 km.  These put the requirements clearly into the SM-3 category.  Seapower and Space contained an interesting note on ASAT envelopes.  The Thor of Program 437 was apparently capable of engaging targets at 200 nm (370 km) at slant rages of up to 1,500 nm (2,778 km) (and higher targets at shorter ranges), while the Nike-Zeus was demonstrated up to 150 nm (278 km).  Encyclopedia Astronautica credits the Thor in question with an apogee of 500 km, and the Nike-Zeus with somewhere between 200 and 280 km, depending on the variant.  It therefore seems prudent to assume that the altitude given for Nike-Zeus was in fact the maximum altitude the weapon could reach.

Another factor controlling the altitude requirements of missiles is the necessity to hold down flight time.  Table 2 gives values for times of flight and view times for missiles fired at spacecraft at various altitudes, with the missiles having an apogee equal to the spacecraft altitude.  The missiles were assumed to be ballistic throughout, which is not a good assumption, but one that must be accepted for purposes of analysis.  Clear view was assumed to begin at 75 km, to account for the fact that defensive fire and sensors may not be fully effective through the atmosphere.  In this case, view time and rise time are very similar, and neither is likely to be strictly dominant.  The fact that view time is normally very close to rise time actually means that given the slowing a missile would experience during passage through the atmosphere, the target might not be able to see it during its burn, or would only be able to see it through a great deal of atmosphere.  If the missile is relatively stealthy during the unpowered portion of the ascent, the spacecraft might not have a good track until it is quite close.

Table 2
Altitude (km)1001502002503005007501000
Rise Time (sec)142.8174.9201.9225.8247.3319.3391.0451.5
View Range (km)1,122.11,369.91,576.81,757.31,919.02,447.02,952.13,359.4
View Time (sec)145.3179.4208.9235.5260.1346.6441.2528.7
Clear Rise Time (sec)71.4123.7159.6188.9214.2294.4371.0434.3
Clear View Range (km)567.1979.11,260.01,486.21,679.92,280.42,831.03,266.1
Clear View Time (sec)72.6126.8165.0196.8225.0319.3418.2508.1

It is obvious that even at the lowest altitudes, the missiles are vulnerable for a considerable period before impact. The obvious solution is to fire a missile that has an apogee considerably above the altitude of the target, minimizing this vulnerability. Table 3 shows the effects of apogee above that of the target.

Table 3
Altitude (km)100100100150150150200200
Missile Apogee (km)150200250200300500400800
Rise Time (sec)73.959.150.9101.072.452.283.654.1
View Range (km)1,122.11,122.11,122.11,369.91,369.91,369.91,576.81,576.8
View Time (sec)145.3145.3145.3179.4179.4179.4208.9208.9
Clear Rise Time (sec)22.716.914.058.739.327.255.534.7
Clear View Range (km)567.1567.1567.1979.1979.1979.11,260.01,260.0
Clear View Time (sec)72.372.372.3125.3125.3125.3161.9161.9
Vertical Velocity (km/s)0.9901.4011.7160.9901.7162.6201.9813.431
Impact Energy Factor1.
Altitude (km)30030050050075075010001000
Missile Apogee (km)40060075010001000150015002500
Rise Time (sec)142.8102.4165.3132.2225.8162.0233.7160.9
View Range (km)1,919.01,919.02,447.02,447.02,952.12,952.13,359.43,359.4
View Time (sec)260.1260.1346.6346.6441.2441.2528.7528.7
Clear Rise Time (sec)114.679.9145.2115.0208.5148.0219.7150.1
Clear View Range (km)1,679.91,679.92,280.42,280.42,831.02,831.03,266.13,266.1
Clear View Time (sec)217.4217.4299.6299.6378.6378.6444.4444.4
Vertical Velocity (km/s)1.4012.4262.2153.1322.2153.8363.1325.425
Impact Energy Factor1.

In most cases, the rise times and particularly clear rise times have been dramatically reduced, meaning shorter engagement times for the target.  The vertical velocity at impact will also increase the damage the warhead does (although the impact energy is not increased significantly unless the excess apogee is very large).  The impact energy factor is the KE of the warhead with the vertical velocity divided by the KE the warhead would have if it were stationary in front of the target.  The biggest drawback is that it is likely to make the missile and launch site easier for the target to locate.  This may not be a major concern if the attacker has a large number of deployed sensors, which could accurately locate the launch site and ascending missile no matter when it is fired.  Another potential problem is that it obviously requires a significantly larger missile to engage a given target with a given warhead.

ICBM-class weapons are less likely to be useful, due to the longer flight times involved.  This gives the target significantly more time to dodge the missile or shoot it down, moving the warhead into the realms described in Section 8.  The size of the weapon is also a serious hindrance to its operational use.  Even the Midgetman mobile ICBM’s launcher was an incredibly large vehicle, which would make it difficult to camouflage as a civilian vehicle.  Even if it could be successfully camouflaged, the number of vehicles of such size is relatively small, and it might be possible to simply destroy all of them.  A more plausible alternative would be to use immobile camouflaged silos.

Other launch platforms are possible as well.  THAAD is somewhat smaller than a BGM-109 Tomahawk cruise missile, which is launched from a variety of platforms, including submarines.  Early SM-3s are of a very similar size and shape to the Tomahawk.  Submarines have the advantage of being able to hide and maneuver in the sea, and are quite difficult to attack from orbit, even if an initial location is known.  The Ohio-class ballistic/guided missile submarines make excellent candidates for this analysis.  Originally built with 24 tubes for the Trident missile, four of them have been modified since the end of the Cold War to carry 7 Tomahawks each in 22 of those tubes, the other 2 being reserved for special operations equipment.  With a dedicated SOM submarine, it would likely be possible to switch out THAAD-class missiles, SM-3-class missiles, and ICBM-class missiles at the dock, giving the vessel capability against various types of targets.  

The single largest issue with submarine-based missiles is targeting.  A submerged submarine obviously cannot use most sensors, and it is unlikely that it will be capable of independently targeting, launching, submerging, and escaping, all before it is destroyed, either by nuclear depth charge or homing torpedo.  Transmissions to submerged submarines are usually made on the ELF (Extremely Low Frequency) and VLF (Very Low Frequency) bands.  The practical issues are the large size of the antennas required to transmit the signals, and the low bandwidth (a few minutes per character to a few characters per second).  The low bandwidth renders it virtually impossible to transmit the targeting data to a submerged submarine, while the size of the antenna sites makes them very vulnerable to attack from orbit.  It might be possible to harden one of these sites, as the US Navy proposed to do with Project Sanguine, or to use an airborne transmitter, such as the E-6B Mercury.  Both present practical difficulties.  The E-6 must orbit such that the trailing antenna is near vertical, while the expense of hardening is considerable, and can be defeated with a sufficiently large number of hits.  In both cases, the problems of bandwidth still remain.  The VLF/ELF systems are usually used to order the submarine to the surface for further orders.  That remains the most likely solution, but hardly the only one.  VLF communication might be able to provide rough orbit parameters, and a sufficiently advanced guidance/sensor system would be able to take that information and home in independently.  Another option is to make a burst transmission to the missiles as they clear the water.  This has the advantage of not requiring the submarine to come close to the surface. Coming to the surface (which is not the same thing as surfacing) is quite likely anyway, given that most submarine-launched missiles are fired at periscope depth, around 18 m (depth of keel).  The Tridents on the Ohio, however, can be fired from at least 40 m.

The effectiveness of the entire submarine-based system assumes that, as is the current situation, it is very difficult to detect submarines from orbit unless they are very close to or on the surface.  This may be changing, most likely due to blue-green lidar, which has been reported to have depth capabilities of 200 m.  The US has used similar systems to detect mines, starting with the Kaman Magic Lantern of the mid-90s, and continuing to the current AN/AES-1 Airborne Laser Mine Detection System (ALMDS).  A system of that type would significantly hinder if not defeat the operation of SOM-carrying submarines.  However, recent blue-green lidar systems have proven ineffective at finding submarines, due to the required dwell time.  They are excellent for searching a confined area for targets that do not move, but less effective as a wide-area search sensor.  

Nor is lidar the only option for orbital detection of submarines.  There have been rumors about programs involving the use of orbital radar platforms to detect submarines since the early demise of Seasat, which many allege was because it was detecting US submarines.  In theory, submarines produce several distinct features on the surface, including a Bernoulli Hump (a bulge in the sea surface) and a Kelvin Wake with a characteristic angle that distinguishes it from that of surface ships.  It also changes the surface wave spectrum, an effect the Soviets attempted to detect with a laser shortly before the end of the Cold War, along with other attempts involving detecting changes in the ocean structure as a result of the submarine’s passage.

A submarine should produce a detectable thermal wake, both because of the onboard heat and because of the disturbance in the ocean’s structure.  The Soviets attempted energetically to exploit this effect, but their IR detectors proved best suited to distinguishing between land and water.  Another possibility is the detection of the chemical wake, either the chemicals that come from the submarine’s hull or possible transmutation products produced by the radiation from the submarine’s reactor.  Attempts were even made to detect the electromagnetic effects caused by the submarine and its wake.  This involved using a laser to detect certain changes in atomic structure that should be caused by the submarine.  Bioluminescence was also investigated, but absorption of light by water appears to have frustrated this in most places.  There are, however, a few places where it is reportedly an effective means of submarine detection.

Unclassified accounts indicate that all of the concepts have been difficult to put into practice, because the signals are very weak unless the submarine is moving very fast very close to the surface, and because there are lots of objects that tend to produce signatures similar to submarines.  In theory, increased computational power and improved sensors should make detecting these features easier, but improved knowledge of the oceans will also be required.  This might be a problem when working with different planets.  The author is not an oceanographer, and does not know how much of the knowledge will be generalizable to other planets, and thus available to an invader, and how much will not. 1

If nonacoustic methods are infeasible, then the attacker must fall back on the old standby, sonar.  This would probably involve the use of what are essentially very large passive sonobuoys, which listen for submarines, and report back to the ships in orbit.  It might be wise to give them some mobility and the ability to submerge temporarily as well.  They would obviously have to run the gauntlet of the existing defenses to make it down, but once down, they would be extraordinarily difficult for the defender to deal with.  Provided that they landed a reasonable distance away from any defenders, they would have to be hunted like mines, and minesweeping in the open ocean is nearly impossible.  (Minelaying in the open ocean is nearly futile, so this is not something the Navy spends a lot of time worrying about).  How effective such a system would be is a matter of conjecture, made worse by the fact that anything to do with sonar performance is highly classified.

As depth increases, launching missiles becomes more difficult, and the communications problems increase.  A towed buoy would solve the communications problem, but it also runs the risk of revealing the submarine’s position.  There are several systems currently in service that use this principle, but all of them impose serious limitations on the depth and speed of the submarine, and most are intended to communicate with satellites, a possibility not available to the defender in this scenario.

In fact, the lack of satellite communications for the defender raises a serious problem.  Direction-finding on radio traffic was and is a major concern for military forces the world over, particularly navies.  One of the solutions to this has been the use of satellite communications, because the uplink from the ground to the satellite is very difficult to direction-find unless a satellite is directly in the uplink beam.  The downlink can be intercepted, but the satellite can be detected by other means as well, and a sufficiently wide beam means that the intercept gives no information on the location of the recipient.  With this capability denied, the defender would be forced to return to older means of communication, which are less reliable, slower, and vulnerable to direction-finding.  Obviously, the use of wired communications would eliminate this vulnerability, but that imposes restrictions on the location of the units, and is totally unsuitable for submarines.

One solution to the communications issues proposed today is a blue-green laser on a satellite.  The problem with that solution is twofold.  First, the defender can be assumed to no longer have any satellites.  Secondly, the defender must be tracking the submarine to a fair degree of accuracy, which is very difficult by definition, and any steps taken to make it easier would probably also make it easier for the attacker to detect the submarine.  It might be possible to avoid this problem by limiting the amount of information transmitted by the laser, and sweeping it over a vast area of the sea instead, to ensure that the target submarine receives it.  While the laser could be mounted on an airplane, communicating with a submarine by that method could give away the submarine’s general location.

Another option is the perennial darling of submarine communications, sonar.  There have been dozens of attempts over the years to use sonar to allow submarines to talk like surface ships.  All have failed for a variety of reasons, including limited range or bandwidth, and multipath scrambling, although the biggest problem has always been that a submarine is inherently stealthy, and announcing its presence to communicate defeats this.  It has been suggested that computers can deal with the multipath problem, and careful system design might allow adequate bandwidth.  The link can probably be made one-way, removing the problem of the submarine announcing its presence.  For that matter, if the attacker has not constructed a sonar net on the planet (as described above), the submarine could talk back without fear of being detected.  This alone might be a reason to deploy some form of sonar system, even if it is not capable of locating the submarines passively.

Attacking a submarine from orbit is likely to be just as difficult as finding it.  Proposed options for this task include homing torpedoes, nuclear depth charges, and dropping minisubmarines.  All of these weapons have issues.  Homing torpedoes suffer from short ranges, somewhere under 15 km for modern air-launched torpedoes.  At a submarine speed of 30 knots, from detection, it will take the vessel a little over 15 minutes to clear that radius.  The minimum time for a kinetic weapon drop, per Space Weapons, Earth Wars, is 12 minutes, although this requires between 40 and 150 satellites for constant worldwide coverage.  This is not as big of a problem as it seems at first.  Submarines are only likely to be detected when a ship is overhead, and the 12-minute time is for a projectile dropped straight down (which does require a large amount of delta-V).  The actual practical range of the homing torpedo is likely to be considerably shorter, as it has to acquire the target and chase it down.  This might also be less of a problem than it appears on the surface, as the projectile would probably be able to be steered after it is dropped.  While the projectile will be blinded by plasma for long periods during the drop (see Section 12), it must slow down to enter the water, giving a window during which it can receive commands.  The logical extension of this idea is fitting the torpedo into a miniature UAV, remotely steered onto the target in a manner similar to the Australian Ikara system.  This assumes, of course, that the target is still in sight, which depends on the altitude of the launching spacecraft and the technology used to detect the submarine.  While the physical range of the torpedo might be improved by advances in technology, the difficulty of the torpedo’s own seeker acquiring a target is unlikely to decrease by a significant amount.  Nuclear depth charges have radii that are likely to be on the order of 10 km, which means that the attacking spacecraft has to be in low orbit for them to reach the target in time to be effective, or the above-mentioned mini-UAV must be used.  Dropping a manned minisubmarine requires a fairly large gap in the defenses, and once it is in the water, it must deal with defensive submarines.  UUVs commanded by blue-green lasers are a better option, although they would likely suffer from limited armament and the possibility of being killed by the defender.  Both of these can be dealt with by making the UUV expendable, which would also eliminate the need for a nuclear power plant.  At the extreme, an expendable UUV would look quite similar to a long-range torpedo taking command guidance from orbit.  Some combination of those and orbital weapons would be the best way to deal with the submarine problem.

One practical issue with submarines is deployment time.  Modern US SSBNs patrol for 90 days at a time, and this seems to be a fairly hard limit based on human factors.  It might be stretched slightly in wartime, but submarine bases would be a priority target for any attacker.  On the other hand, it is also possible that the human factors issues will have been solved due to the demands of long-term spaceflight, which has many similarities to submarine operations.  Other operational issues would then limit the deployment time, such as food (although this could probably be resupplied by boat when there is cloud cover) and maintenance (which is the ultimate limiter in any case).

Another major option for planetary defense is lasers.  These lasers differ from those for deep-space use, both in the fact that they do not have to deal with the weight and heat restrictions of space-based systems, but they (and any bombardment lasers) must be of wavelengths that can penetrate the atmosphere.  This limits the range that said lasers can achieve due to diffraction.  Adaptive optics and other techniques can compensate for most of the various phenomena that occur when a high-powered laser is fired through an atmosphere, as can siting the laser at high altitude.  The largest weakness of ground-based lasers is that they are immobile, and thus can be targeted by high-velocity kinetics.  This is compounded by the fact that when a laser is fired it immediately reveals its position to the target.  The attacker can then pull back to an orbit out of reach of the laser and bombard it at his leisure.  

There are numerous factors involved in determining the viability of such an installation, including the vulnerability of such installations to bombardment, the effectiveness of the laser, the cost of the laser, and the difficulty of intercepting the bombardment projectiles.  The first is a difficult question to answer.  How effective is a deep bunker against kinetic bombardment?  While the projectile is unlikely to penetrate deep enough to be a threat to a Cheyenne Mountain-type installation (unless the projectile is very large), the shock wave from the impact could damage the laser machinery.  Shock mounting might mitigate this, although a full treatment of such matters is outside the scope of this discussion.  However, the main mirrors themselves must be located near the surface, and would be the points attacked anyway.  It would be entirely feasible to have one generator feeding multiple mirrors, but that tactic is unlikely to be used unless the mirror in question costs significantly less than the generator.  Such a ratio is significantly below the theoretically optimum ratio for mirrors and generators, as shown in Section 7.  The effectiveness of the laser is another question.  It has been suggested that a ground-based laser might be capable of attacking targets as far out as geosynchronous orbit, and could also be used to detect incoming kinetics, giving the laser as much as 12 hours to attack them.  If this is the case (which assumes a 10 meter mirror) the laser system might be intended for use in the defense of the higher orbits, the lower orbits being defended by missiles.

There is also the potential for submarine-based lasers.  It is theoretically possible to create a laser that can be mounted and fired from a submarine, probably using some combination of superhydrophobic surfaces and high-strength windows in front of the mirror that can take the shock of water on them being vaporized.  The problem is that the submarine itself does not make a good laser platform.  Modern submarines are optimized for underwater operation, which tends to mean poor stability on the surface, and mounting the mirror is not a trivial task when one remembers that the submarine as a whole has to be waterproof.  However, such a submarine is not entirely unprecedented.  The USS Triton (SSRN-586) was designed as a radar picket, and built to perform well on the surface.  This had significant drawbacks, most notably in making the submarine very noisy underwater.  On one hand, Triton was designed before the beginning of serious emphasis on submarine silencing.  On the other, a large portion of the noise problem is likely to be inherent in the hull form required for surfaced performance.  On the gripping hand, sonar detection is likely to be somewhat less important in planetary defense.

A laser launch system would also serve as an effective planetary defense station, provided with the proper targeting systems.  The drawback is that the laser itself is in a known location, denying it the element of surprise even for its first shot. Depending on the geometry of a planetary invasion (discussed in section 12) it might or might not be capable of firing on incoming enemies before it is destroyed.

Other means of intercepting the bombardment projectiles have been proposed, as well.  Most of these rely on the fact that a kinetic projectile is vulnerable to disruption during its entry into the atmosphere.  These proposals have ranged from nearby explosions to barrage balloons to some form of hit-to-kill CIWS.  All would disrupt the projectile enough for it to disintegrate, dumping almost all of its kinetic energy into the atmosphere.  The presence of effective defenses of some sort would greatly reduce the vulnerability of ground targets, particularly dug-in ones.  A similar concept was the ‘Dust Defense’ proposed during SDI, which involved using buried nuclear weapons to throw dust high into the atmosphere to destroy incoming warheads.  However, only limited information on the concept is available, precluding further analysis.  

A potential use for smaller, portable lasers is a dazzle system.  Smaller, lower-powered lasers are used to blind the attackers, allowing the defender to escape observation for a short time.  However, this is easily defeated by the use of multiple networked sensors, some of them on small, unmanned satellites that are essentially impossible to detect passively from the ground.  In some ways the best use of such lasers might be as a distraction from something important going on elsewhere.  Both optics and processing power make it impossible to monitor an entire hemisphere in high detail and in real time.

The last option the defender has is cannon of some kind.  When first proposed, this solution was questioned, as firing a cannon up a couple hundred kilometers runs into the problem of firing through the atmosphere.  It was later realized that Project HARP had done exactly that in the early 1960s.  Using a modified 16-inch gun, sub-caliber projectiles were fired to altitudes of up to 180 kilometers.  Obviously the HARP launcher would be unsuited to planetary defense roles, but it has been proved possible to fire ballistic projectiles from sea level (the HARP test site was on a beach in Bermuda) to significant altitudes.  However, these altitudes alone are insufficient to reach a target in most orbits.  The muzzle velocity for the high-altitude tests was approximately 2100 m/s.  This can be compared to 2500 m/s for the Navy’s railgun project.  For comparison, the early models of the SM-3 had a delta-V of about 4 km/s, while the later models are about 6 km/s.  If increases in velocity due to a switch to electromagnetic launching prove insufficient, then there is the option of using a rocket-boosted projectile.  This would require significantly less delta-V than a conventional rocket, preserving many of the advantages of the purely ballistic system.

Ballistic defense shares advantages and disadvantages with both lasers and missiles.  Any installation will almost certainly be fixed, as it requires a long barrel, though advanced coil/railguns might not have to be.  However, unlike lasers, a ballistic system does not by definition give away its position with each shot.  It is likely that the enemy could spot the muzzle flash if a chemical cannon is used, but railguns and coilguns do not have this problem.  The projectile would have to be guided, but it is possible to acceleration-harden a projectile, and aerodynamic effects could be used for minor course changes while low in the atmosphere, reducing required delta-V and preventing backtracking to the launch site.  At the same time, intense surveillance and intelligence efforts could probably locate the launch site eventually, and unlike lasers, all of the machinery must be close to the surface.

One advantage of cannons over missiles is that the projectile is much harder to detect during the climb.  The projectile lacks the exhaust signature of the missile, and is also smaller, both contributing to lower detection ranges and engagement times.  Also, it can be presumed that shells are cheaper than missiles. There have been some real-world investigations of electromagnetic suborbital launch systems, most notably by the ESA 2. Their investigation concluded that it would indeed be possible to use a railgun to replace sounding rockets, firing a 3 kg payload through a 22 m barrel at a velocity of 2,158 m/s.  The maximum altitude of the system was expected to be 120 km.  While this is a bit lower than would be necessary in a planetary-defense system, it does show the feasibility of such a system, and there is even the potential that it could be truck-mounted.  The largest problem with such a mounting would probably be power, although ultracapacitors could be used to store and transport power generated by deeply-buried reactors to the launch trucks.

In the absence of effective laser bombardment capability, aircraft become a viable defensive platform.  They are nearly impossible to target with kinetics, although some form of autonomous antiaircraft missile might be effective. The use of aircraft for planetary defense has some precedent.  The US ASM-135 ASAT missile was air launched, and had a ceiling of approximately 560 km.  The greatest advantage of air launch is that the launch platform can rapidly move to cover a vulnerable area.  The greatest disadvantage is the facilities required to base a conventional aircraft, which are immobile and vulnerable to bombardment.  VTOL aircraft would make this more practical, but the support facilities (and landed aircraft) would still be capable of being targeted.  However, it might be possible to use point defenses to secure an aircraft base, and deploy the aircraft as mobile missile platforms at need.

Lasers could also be mounted on aircraft, much like the YAL-1.  Aerodynamic limitations on the size of the mirror make it doubtful that an aircraft could successfully duel a spacecraft, and it is hard to see a set of technical assumptions under which aircraft-mounted lasers are practical but spacecraft-mounted ones are not.  Among other things, the physical environment of an aircraft is rather less well-suited to precise control of a laser than is a properly-designed spacecraft.  The aerodynamic forces on the aircraft will tend to produce vibration, which is undesirable when using lasers, and absent in spacecraft.  Crew, fluids, and thrust will also contribute, and are likely to be larger in magnitude than those found on spacecraft.  The atmosphere does provide a slight advantage in terms of cooling, and the fact that an aircraft can be presumed to be operating near a base increases the practicality of chemical lasers.  On the other hand, aircraft can successfully use clouds to protect themselves against lasers, which require gigawatt levels of power to burn through fast enough to track an aircraft.  

        While not technically surface defenses in the conventional sense, fortifications on moons could be vital for planetary defense.  Luna is a bit far out from earth for it to make a really effective fortress, but Phobos and Deimos would make excellent bases for large lasers.  The mass of the moon gives lots of places to dump vibration and heat to, and Phobos orbits in 7 hours 40 minutes, while Deimos takes 30.3 hours.  Even Luna could be strategically important, depending on the scenario.  Ignoring possible infrastructure present on Luna that would make it worth defending in its own right, there are several reasons that a defender would desire to deny it to an attacker.

        The most likely reason to land on Luna would be remass, although the practicality of that depends on the remass used by the fleet.  That in turn depends on the type of thruster used.  The standard cases used throughout this paper are chemfuel, nuclear-thermal, and electric of some kind.  Availability of remass for chemfuel and nuclear-thermal engines obviously depends upon the type of remass.  Some chemful mixtures, like aluminum-oxygen, are readily available anywhere on the lunar surface.  Others require much scarcer and more valuable elements, particularly hydrogen.  While the LCROSS mission did confirm the presence of large amounts of water at the poles, this water is likely to be too valuable for life-support purposes to be used as remass feedstock during normal times.  A potential attacker, however, might not care.  An NTR can theoretically use just about anything as remass, with exhaust velocity varying based on temperature, it is incredibly difficult to build one that will run with both oxidizing remass, such as oxygen, carbon dioxide and water, and reducing remass, such as hydrogen, ammonia, and methane (See Section 14 for more details on this).  Of these, only oxygen is truly readily available from lunar sources.  While there is water, the quantity is limited enough that using it for remass is questionable.  Also, the high molecular mass of the water makes it a less-than-ideal candidate for NTR usage.

        Electric thrusters are less likely to be able to get remass from Lunar sources (due to lack of information about both thruster propellants and body composition, the author refuses to speculate about other celestial bodies).  On the other hand, electric thrusters have much higher exhaust velocities, so less remass in total is required for a campaign.  In fact, the availability of a given remass is likely to play a significant factor in its selection for use on a vessel.  Most modern Hall Thrusters and other ion thrusters use Xenon for remass.  While Xenon is basically ideal for use as remass, it is far too rare to support the level of interplanetary trade that would be a prerequisite for any sort of serious war.  Krypton is the next best choice, but it is also too rare.  Argon is less effective, but probably the best among the noble gasses from an operational and engineering standpoint.  Some early ion thrusters were tested with Cadmium and Mercury, but both of these have had serious operational issues during tests, and are not notably abundant on or off Earth.  Possibly the best option is colloidal thrusters.  These use some form of hydrocarbon fuel, which has the advantage of being no less abundant than the other options throughout the solar system, and significantly more abundant on Earth.  However, the technical advantages of one of the other designs might well outweigh the logistical ones of the colloidal thruster, and the author does not know enough about the issue to be sure one way or the other.

1 Seapower and Space by Norman Friedman provided most of the information on attempts to detect submarines from space, along with information on the importance of satellite communications. It also pointed out that some stories of US nonacoustic detection might have been the result of deceptions intended to trick the Soviets into spending money in an attempt to match them."

2 Electromagnetic Railgun Technology for the Deployment of Small Sub-Orbital Payloads.

by Byron Coffey (2016)

Laser-equipped nuclear-powered submarines are the perfect last line of defense against an attacking force in orbit.

The situation

You don't win every fight. Eventually, there will come a time in space warfare where a fleet of space warships has defeated all your mobile forces and your immobile defenses. They will bear down on you from above with lasers, missiles and kinetic projectiles and you will have to find a way to prevent their forcing of an unconditional surrender.

We will refer to the opponents as the 'attackers' and to you as the 'defenders'. The first step to devising an effective defense is to understand the situation.

So what is the situation?

An attacking warship will start out in high orbit. This is an altitude of 2000km or above. Whether it has just arrived from an interplanetary voyage or has recently destroyed your remaining warships, it will go to high orbit to maximize the effectiveness of its space superiority. Space superiority, borrowing from the term 'air superiority', is when a force has complete dominance over all the orbits around a planet. No space-borne forces can oppose this superiority and no reserve forces can challenge them without being quickly destroyed.

What does losing space superiority mean for defenders?

The most important consequence is that enemy warships have free reign to change orbits, maneuver into favorable positions and receive re-supplies. Their mobility is unconstrained.

Attackers in high orbit can make optimal use of their laser weaponry. They can get clear lines of sight onto any spot on the surface, and the long distances between objects forces travel times to length with the secondary effect of giving lasers plenty of time to shoot down targets. Laser effectiveness is generally dependent on how far they are from a target and how much 'dwell time' a beam can spend on a target.

De-orbiting objects from high altitude is inexpensive in terms of deltaV. This works in favour of missiles sent down from orbit by allowing them to use very little propellant to strike ground targets, which makes them lightweight and cheap to send by the hundreds. Additionally, falling towards Earth gives them a big boost to the velocities they achieve before impact.

The same applies to kinetic projectiles, a fact applied in the Rods From God concept of orbital bombardment.


So you want to shoot back at the attackers.

Missiles can do the job. They are currently our only method of delivering weapons into orbital space. Something like an ICBM with an additional stage can reach LEO. Reaching higher orbits will require either a very large rocket, a high Isp engine for the upper stage or a launch system such a laser launch or ram accelerator.

However, each of these solutions have major issues when trying to shoot down an opponent in high orbit.

Large rockets are easy to target and shoot down. A chemical-propellant rocket that needs to minimize its dry mass to achieve the necessary deltaV capacity will have very good acceleration but will end up being very fragile. Nuclear-thermal or nuclear-powered rockets can be much smaller and more durable, but getting sufficient acceleration out of them implies a very high power requirement, which might make them very expensive to throw at the enemy.

Regular launches take tens of minutes and cannot be disguised from the attackers. Shortening this window of vulnerability can be done by using a launch system that powers the rocket or accelerates it externally. However, the infrastructure for the launch systems will in turn become a priority target for the attackers. Massive, hard to hide and immobile, they will receive a lot of firepower. Some launch systems are practically impossible to shield from damage, such as a laser launch system that needs thousands of exposed laser optics, and others reveal their positions as soon as they fire a rocket. Building underground is also a very expensive endeavour when considering that all the work can be undone by a single 'bunker buster'-type weapon.

The logistics of launching missiles against attackers sitting in orbit works against the defenders. The attackers can de-orbit a missile by expending only a few tens to hundreds of meters per second of deltaV. A defender must equip each missile with tens of thousands of meters per second of deltaV. It might be easier to build more missiles and create rocket fuels on the ground at the start of the war, but after an orbital bombardment campaign by attackers with space superiority, it is unlikely to be the case.

Kinetics that can be shot all the way to high orbit need to handle hundreds to thousands of Gs of acceleration, traverse the lower atmosphere at dozens of kilometers per second, survive laser fire for several minutes with minimal capacity to dodge and take out a target with a very short window of interception. This is a tall order!

So, what are the defender's options?

They need to retaliate with something that cannot be shot down, from a platform that can avoid counter-fire and can maintain functionality after infrastructure and services have been disabled world-wide.

One option that fits the bill is laser submarines.

Lasers cannot be shot down and hit their target instantly. They can be used so long as electrical power is supplied. Submarines operate underwater, an environment that can hide them until they surface and protects them from high-velocity projectiles and lasers while submerged. The can protect themselves this way for months on end, and if they employ the same life support systems as on spaceships, then it can add up to years.

For the same reason that today's submarine fleets are considered an unbeatable means of retaliating against a foe after nuclear armageddon has wiped out the homeland, laser submarines will be able to operate and remain dangerous even after orbital attacks destroy all support infrastructure.

Let us now look at how a submarine can be used to retaliate against attackers in orbit.

The Challenges

Submarines are already equipped with a high electrical power generation. Large modern nuclear submarines are already able to produce over 100MW for years on end. In a futuristic setting with common space travel and space wars, power generation technology developed for interplanetary travel will allow submarines to produce gigawatts or more.

The most likely generators for space travel will be nuclear due to their high power density. The biggest limitation to generating power from nuclear reactors is waste heat capacity: It is easy to heat up the reactor core but much harder to remove the heat. Submarines will have an entire ocean as a heatsink so will be able to produce more watts compared to a spacecraft with a reactor of the same mass and volume.

All of this electrical power can be used to power a laser generator.

Three elements determine a laser's effectiveness: wavelength, radius of focusing optics and beam power.

We have already determined that laser submarines will likely be able to produce more electrical power than a similar laser space warship, so laser submarines will also have the advantage in beam power.

The radius of the focusing optics will depend on the specific arrangement of the laser weapon's components and how they are deployed. We will look into the possible designs down below.

The wavelength however is not a variable laser designs have much control over. Submarines operate in an aquatic environment, on top of which is a hundred kilometers of Earth's atmosphere. At the interface of the ocean's surface is sea mist and suspended droplets of water in fog or clouds. The ocean's surface is not flat either, with waves of a few centimeters to a few hundred meters rolling over it endlessly. A beam emitted by a submarine will have to penetrate all of this environment and still travel the hundreds of thousands of kilometers' distance separating it from a target in high orbit.

The optical properties of water are therefore the determinant factor for which wavelengths the laser should produce.

Here is the absorption spectrum of water:

The lower the 'Relative Absorption value', the less the wavelength's energy is absorbed. We can clearly see that the lowest values are for the 'optical window' that corresponds to the 400-700nm visual spectrum. The highest absorption is for 100nm ultraviolet wavelengths and 3000nm infrared wavelengths.

Here is the absorption spectrum for our atmosphere:

The atmospheric attenuation of electromagnetic radiation has similar features to that of water: short wavelengths such as X-rays cannot go through while long wavelengths such as radio penetrate easily.

It might be easier to consider the laser beam as being fired from space and coming down to the surface.

A 100nm ultraviolet laser beam will traverse the vacuum of space with ease, but will stop short of reaching the upper atmosphere. A 400nm blue laser will go through the atmosphere and through 460 meters of water before being reduced to less than 1% of its initial power. A 1000nm infrared laser will lose 20% of its power to the atmosphere and be completely absorbed by half a meter of water. A 100m radio wavelength just bounces off the ionosphere.

While shorter wavelengths are preferred for laser weapons, as they allow a beam to be focused to destructive intensities over longer distances, a laser submarine should use 400nm wavelength lasers to penetrate water and the atmosphere without losing a lot of beam power.

The equation for how much of a beam's energy is retained after traversing a medium is given by:

Percentage transmitted: e^( -1 * Attenuation coefficient * Depth) * 100

The attenuation coefficient is usually given in cm^-1, so the depth should be converted into cm units.

For example, near-infrared light at 800nm wavelength has an attenuation coefficient of 0.01cm^-1. We want to know what percent of a near-infrared laser's energy remains after passing through one meter of water.

One meter equals 100 cm. Per our equation, we find the percentage to be approximately e^(-0.01*100)*100: 36.8%. Just over a third of the beam gets through.

Here is a table of values for how much beam power is lost if the blue wavelength laser submarine fires its weapon at different depths, using an attenuation coefficient of 0.0001cm^-1:

We see that to maintain a good percentage of laser power getting through the water, a laser submarine would have to fire at rather low depths. According the the table above, a 10 meters depth using blue laser light looks like a good compromise: deep enough to escape orbital surveys and strikes, with at least 90% of the laser power going through.

So is a laser being fired at 10 meters depth a good idea?

The table gives an incomplete picture. While laser power being absorbed is an important factor to consider, there is a large number of other elements that affect how effective a laser is. One such element is thermal blooming. That 90% power transmission rate implies that 10% of the laser power is absorbed and goes into heating the water. If the laser power is rated in megawatts, the heat absorbed by the water becomes significant. Hot water has different optical properties compared to colder water - it will work as a lens in reverse, effectively de-focusing the laser.

Another significant issue is the water/gas interface. When light travels between two mediums of significantly different density, like seawater and atmospheric gasses, it is bent by refraction. Even worse, the sea's surface is constantly disturbed by waves, tides and other movements. Instead of a smooth surface, which angling the laser can compensate for, it is continuously changing and bending light in different and hard to predict direction. Here is a familiar example of the effect:

This effect is familiar to astronomers trying to gaze at stars through the moving atmosphere, and adaptive optics are used to compensate for the deviations in light traversing the atmosphere.

Adaptive optics cannot be employed as effectively when used underwater. While the atmosphere's movements are already difficult to detect and correct, trying to effectively measure how light moves through two mediums with a complex and moving interface is much harder. Guide lasers are used for measurement, with the light reflecting off the ionosphere creating an artificial 'guide star' for astronomers to calibrate their instruments. A guide laser placed underwater would submit to the same chaotic disturbances as the weapon laser and would be unusable. They would also have to work much harder. Refraction means that inaccuracies are multiplied once they pass through the water/air interface.

Finally, there's the problem of reflection. While water is decently able to let higher wavelength visible light penetrate, the massive difference in density between the water and the air (x1000) above it means that it is a good reflector. Laser light would travel from the submarine to the water/air interface, and just be bounced back below the surface. For sea water, less than 6% of the laser light would be reflected at angles below 30 degrees.

While the above table might not give any large figures, remember that the angle is measured against the rippling, swelling and rolling waves. A nominal angle of 10 degrees against the water's surface might transition between -20 and 100 degrees as a wave moves over a laser. This is the difference between 3% and 45% of the laser not going through the ocean's surface.

The principal advantage of staying underwater is that the submarine will be protected from high velocity strikes and retaliatory laser fire. However, if it cannot return fire from this position, then it cannot serve as a perfect last line of defense.

The Solutions

So, based on the previous section, we can affirm that attempting to shoot a laser while underwater provides unequalled benefits but also significant challenges.

We can either tackle the problems a laser submarine faces directly or attempt to circumvent them.

-Long wavelengths

Previously, we considered that blue wavelengths were optimal for shooting while underwater as they were absorbed the least. The reduced absorption would have allowed a submarine to transmit over 90% of the laser power to the ocean's surface from a depth of 10 meters. However, the distortion at the water/air interface rendered this option impractical.

How about using a wavelength that is less efficient at penetrating water, but is less affected by distortion?

Looking at the absorption spectrum of water, we notice that wavelengths longer than 100 micrometers are absorbed less and less as the wavelength increases. At 1m wavelength, the laser would traverse water as easily as blue light. This corresponds to a frequency of 300MHz. This is the radio band.

Not coincidentally, frequencies of lower than 300MHz are used to communicate with submarines. At 3 to 30kHz, which is wavelengths of 10 to 100km, can penetrate the seas to a depth of several hundred meters. Using even lower frequencies further increases penetration depth, but would require impractically large lens to focus onto a target in high orbit. Another factor working against longer wavelength radio is that the ionosphere can reflect signals back down to the surface at frequencies below 30MHz.

A 1m wavelength radio laser will be able to traverse the atmosphere mostly undisturbed and go through the ionosphere without refraction. The features of waves are too small to cause it to wobble chaotically at the sea/air interface. The beam would bend coming out of the sea, but it is a single predictable deviation that can be corrected.

A radio-wavelength coherent beam or 'raser' can be generated by a Free Electron laser or inductive output tubes with an efficiency exceeding 70%.

The advantages of a radio-based anti-orbital system is that it allows a submarine to fire upon targets while deep underwater. Even at 20 meters depth, the radio beam would transmit 82% of its power through water and lose less than 1% going through the atmosphere. It is much less affected by small waves and other turbulence in the water, and mostly immune to above-surface weather effects.

There are several downsides however. Such a large wavelength makes it impossible to focus the beam down to destructive intensities without a very large radio dish - this might get impractical when you also want the submarine to move quickly while underwater. Another issue is that the beam won't interact with the target in a consistent manner.

Lasers, for example, are absorbed by the outermost layers of the materials the target's surface is made of. The heating is concentrated in the 'skin' of the target. Sufficiently intense laser beams heat this skin layer to very high temperatures, causing the material to boil away or even explode.

Radio beams would use wavelengths a million times longer that do not interact with the target's materials at an atomic level. They are much more sensitive to the conductivity of the materials they are striking. Good conductors such as steel or aluminium efficiently reflect radio waves and are not heated. Good insulators such as ceramics or glass are mostly transparent to radio waves and do no absorb the beam's energy as it passes through them. Radio absorbing materials have to be neither good conductors or insulators, such as (sic)

This is bad news if the targets are space warships with an external metallic hull and an internal structure based on advanced carbon-composite and ceramic materials. Large propellant tanks will let the radio waves pass straight through. Small features of 10cm or smaller are completely invisible to the radio waves too.

However, there will still be ways to deal damage.

Openings in the metallic hull would allow radio waves to enter and then bounce around on the internal surface. Like a microwave oven, the trapped radiation will pass through radio transparent materials thousands to millions of times before being fully absorbed. A human is mostly composed of salted water. He or she would absorb about between 0.1 and 1% of a radio beam going through their body. If the radio beam stays inside a 10m diameter hull for just 76 microseconds, 2300 bounces are possible and the percentage of beam energy absorbed rises to 90%. When the beam power is measured in tens to hundreds of megawatts, this has dire consequences for a human crew.

Another effect is induced current. If even a few watts manage to circulate in microcircuitry, it is enough to short-circuit or even melt down computers, avionics and delicate sensors. RF Shock and Burn is a serious issue for electricians and engineers working on conductive structures near a high frequency radio source. At the power levels radio-laser submarines will pump into targets, induced current is enough to melt steel.

Modern submarines are not powerful enough to compensate for the diffraction of a 1m wavelength radio beam. With 100MW of available electrical power, 30% of which is lost in an inductive output tube and another 10% to seawater and atmospheric absorption, less than 63MW will reach space. Even the largest submarines, such as the Ohio-class SSBN, have a hull diameter (beam) of 13m. Mounting an internal dish to focus a radio beam up to this diameter will create a very low performance laser.

Targets at 10km distance will receive about 22W/m^2 - a great radio signal, but a terrible weapon. Targets in low orbit and high orbit will receive milliwatts of power.

What is needed is much more power and an externally mounted radio dish. Thankfully, a 300MHz beam can be focused by a dish with holes up to a tenth of the wavelength in size. A radio dish for this wavelength can is very lightweight and easily collapsible, with conductive spars spaced by 10cm lengths. The spars can be made hollow to have neutral bouyancy, allowing them to support themselves without many structural elements. At 10m depth and below, there are few disturbances in the surrounding water.

Dish diameters of 100 meters or more are envisageable, massing less than 1kg per m^2. Tension wires hold the shape and serve as the mechanisms for adaptive optics to act on the dish.

A group of submarines using space-grade nuclear reactors might be able to put together 500GW of power with a combined reactor mass of only 2500 tons. Between them, they can hold up a dish 1km in diameter, as follows:

This arrangement allows the submarines to focus a 315GW beam to an intensity of 67kW/m^2 at an altitude of 1000km. For low orbit targets, the intensity is 1.67MW/m^2. These intensities are far from enough to melt or physically damage the structure of a spaceship. However, the beam is large and entirely envelops the target. Any hole through a metallic exterior or any cavity lined by a radar reflector will turn the spaceship into a microwave oven receiving megawatts of heating over time. At high altitudes, the intensity is lower by the targets orbit much slower, giving the Rasar beam time to boil crews to death and melt components directly or indirectly.

-Interface lens

The biggest trouble with optical wavelengths is the chaotic distortions and reflections created by the sea/air interface. They would allow submarines to physically damage targets with relatively small lens and shoot on the move, but aiming though the interface seems impossible...

... unless an interface lens is used.

It is an optical array that floats on the ocean's surface, serving to handle the beam's transition from underwater to atmospheric mediums. Glass can be made to have a refractive index similar to that of water. A laser beam traversing a sea/glass interface would not suffer any distortion. This is the reason why some transparent objects disappear completely while underwater - our eyes cannot make out any distortions that reveal their presence.

The interface lens can also serve to focus the laser. It can be made much larger than whatever the submarine can carry, as it is not confined by hull dimensions or hydrodynamics.

One primary advantage of these floating structures is that they can be deployed before firing commences, and each is much cheaper than a submarine. When a target passes overhead in orbit, a laser submarine can rise to firing depth and start shooting. It only needs to equipment to focus the beam from the laser generator to the interface lens, a distance of ten meters or so. The floating lens receives the beam, corrects the angle and aims at the target overhead. If the target is not destroyed, it can trace the laser back to its origin and initiate a retaliatory strike.

An interface lens is not very mobile and needs to stay on the surface, so it cannot protect itself by diving. There is a good chance it will be destroyed... at which point the laser submarine switches to firing through another interface lens and so on.

Although the lens will have to be rather large and heavy to receive a laser beam from a wide variety of angles underwater, and re-focus it in a moving target hundreds of kilometers above, which makes it expensive, it must be considered as an expendable asset when compared to cost and size of a nuclear submarine. Also, the lens can be covered by an isothermal sheet and made out of materials transparent to radar, making it hard to detect from orbit until it starts firing.

Using a 10m diameter interface lens, even a modern submarine with 100MW of available output will be able to deal serious damage to targets in low orbit. About 40MW of the submarine's power will reach the target using a diode laser generator at 400nm wavelength, but at an intensity of 133GW/m^2 at 200km altitude. This is enough to rip through 14.8 meters (!) of aluminium per second, or even 6.5m/s of carbon armor. Any target caught by this beam for even a second will be cut in half. At 1000km, its performance is still a respectable 52mm/s through carbon.

More advanced submarines can get away with smaller lens that are harder to counter-attack and still deal devastating damage to high orbit targets. A 10GW laser beam focused through a 4m wide interface lens can blast away targets at a rate of 837mm/s at 1000km.

Disadvantages of this system is the cost of 'expendable' large adaptive mirrors and possibly the inability to use floating structures in severe storms with large waves rocking the optics.

-Towed Lens

This fixes the problem with floating optical arrays. The laser is focused by towed apparatus that can be held underwater until firing starts, and then moved around after an initial volley to avoid counter-fire.

The towed lens can be lighter and cheaper than a fully independent floating lens. Electrical power, computing operations and other functions can be provided by the submarine towing the lens, with only the actuators and suspension retained.

Lasers have been carried through optical fibres with nearly zero losses of beam energy over distance. This is because internal reflection of the beam is done at grazing angles within the optic fibre. In other words, laser beams of megawatts to gigawatts power levels can be transported by optic fibres without any significant losses and no special provisions against heating.

Optical fibres can carry a laser generated by a submarine to the towed lens, and they can run parallel to the load bearing cables attaching the lens to the submarine. This method of delivering the beam to the lens bypasses the losses and complications of having the beam penetrate several meters of water to reach the surface.

To these advantages come some downsides. The submarine becomes more vulnerable that if it relies upon fully independent floating lens. If an enemy target locates a floating lens, it might correctly assume that the much more valuable submarine is very close to the lens. When a target spaceship in orbit sends down counter-fire before the submarine is ready, the latter would be forced to cut loose the lens and dive... this breaks the optical fibre cable and renders the lens useless.

Tactics using towed lens might involve dragging along a fleet of lenses and rotating them to the surface and back. Longer fibre optic cables gives the submarine more freedom to move, while a mix of decoys and intermittent and random firing patterns reduces the disadvantages of the design.

-Optical phased array floater.

Do away with the submarine!

A specialized vehicle can be built solely for the purpose of hiding a laser weapon underwater and surfacing for short bursts of fire. Since this weapon only attacks from above the water and does not have to worry about hydrodynamics, nifty solutions such as an optical phased array can be used. The laser generator's size is equal to the lens diameter and if it received damage, it will only suffer reduced output.

The more delicate components such as the power generator can remain submerged, only transporting electricity to the phased array on the surface through cables. A reactor embedded in the sea floor can be a very difficult target to locate and destroy.

-Supercavitating platform.

If submarines have access to gigawatts of power, they can also use it for propulsion.

This level of power output can enable submarines to reach supersonic speeds through supercavitation through water. If they can rise to the surface, fire, dive and relocate in a matter of seconds, then they can evade counter-fire through sheer agility.

It might be best in this case to mount a set of optical phased array lasers tailored to trans-atmospheric wavelengths to be used once a submarine surfaces. Gigawatts of power means gigawatts of heating: the local atmosphere can be cleared of moisture and mist that distorts the beam most heavily.

A 1GW laser at 400nm focused by even a relatively small 4m diameter lens can blast past 23.7m/s of aluminium or 10.4m/s of carbon at 200km, and remains deadly at 1000km with 83mm/s of carbon penetration. This allows for short bursts of laser fire to take down any target.

Advanced techniques such as thermal lensing using the Kerr effect is being developed in programs such as the Laser Developed Atmospheric Lens (LDALs) by DARPA. LDALs can allow high-power submarines to extend their effective range to tens of thousands of kilometers while reducing the effectiveness of laser counter-fire.


Lasers and underwater environments don't mix well, but there are many solutions to gain the protection a submarine enjoys while attacking instantly and repeatedly with direct energy weapons.

Once these solutions are applied, a defending planet with deep oceans can hope to maintain an effective last line of defense against invading spaceships.

From ANTI-ORBIT LASER SUBMARINES by Matter Beam (2017)

One of Rand’s soldiers addressed him.

“I’m getting a yellow on Miss B*tch, Mirror 6,” said Private Tim Yancey. Miss B*tch was the affectionate name for one of Rand’s three cannons. (Alpha Dawg and California Girl were the others.) “Think it’s stuck, or at least moving slowly. Might be some gunk in the way.”

Some officers didn’t like to swear in front of their people. Rand was not one of those officers. When he was finished, he said, “All right, I’ll go look at it. Get Smith and Ekkers to meet me down there.”

Rand walked half a klick through an extinct underground lava tube to reach Miss B*tch, buried beneath 20 meters of earth to protect it from bombardment.

His laser cannon looked nothing like the compact guns mounted on warships; with the earth stripped away, the entire contraption would appear as a giant, overturned spider. The beams were generated in the spider’s head, powered by batteries that drew energy from a fission plant buried underneath Fort Patton. A rotating emitter fired the beam down the spider’s “legs,” eight long, hollow corridors that angled toward the surface. When the cannon was fired, the beam would be directed down a random tube.

Mirrors directed the beams at each turn; a final mirror, mounted on an armored cupola that rose above the surface, directed the beam toward any target in Sequoia’s sky. This last mirror was “deformable;” with every shot, thousands of tiny actuators inside the mirror would subtly alter its shape, preventing distortion from Kuan Yin’s atmosphere from defocusing Rand’s beam. (The level of distortion was gleaned from a second, low-power laser that fired from atop the cupola a fraction of a second before the primary blast.)

After a shot, the cupola would drop beneath the surface, and a camouflaged hatch would close above it, more or less concealing it, at least to a spaceship hundreds or thousands of klicks away.

The whack-a-mole rig was a design of necessity; ground-based laser cannon were too large and heavy to safely operate on a planet’s surface or in its atmosphere. A 480-megawatt laser capable of drilling a hole in a starship 5,000 klicks distant needed a lot of batteries, it was simply too big a target to mount on wheels or turbofans.

     One of the nice things about the artillery was you got the best telescopes. Rand had a terrific view of the battle, and early on, it seemed to be going well, despite China’s superior numbers. The Chinese ships had formed a two-dimensional diamond, with one flat face to the main body of the American squadron. The American commander had elected to split his fleet and was coming at the Chinese from two directions, about 90 degrees off from one another. He was gunning for the Han assault carriers, which were hanging well back from the battle. The Chinese responded by concentrating their fire on only one group of American ships, leaving a flank exposed.
     At least two small Han vessels had suffered catastrophic failures in their fusion candles; their explosions were visible to anyone looking up from Kuan Yin’s surface. At least one American destroyer was badly damaged, drifting away on a vector that would take it out of the battle.
     Then, all at once – it was impossible from Rand’s vantage to tell what exactly happened – the battle came apart for the Americans. The senior captain’s flagship, the Puerto Rico, vanished in a fusion-fueled fireball. The light cruiser Norfolk died moments later. The surviving American ships – two frigates and an escort – turned and fled for the only American keyhole (stargate) in the system. A final barrage of missiles aimed at the Han troopships was shot down, their destruction showing up as pinpoint flickers on Rand’s monitor. The Han fleet then quickly disposed of the American surveillance and communications satellites in all but the lowest orbits over the planet.
     Major Montaño was on the comms a few minutes later. “Space Force did what they could. We’re up next. The Han formation will be in range in four-zero minutes. Out.”
     Rand’s platoon was in four separate locations in the underground complex, one crew at each gun in addition to his command center staff. Rand could control all three lasers from here, but the teams were stationed near each cannon in case communications were cut, and to perform any repairs that might be needed during a battle.
     He switched over to his platoon’s network. Time to say something inspiring.
     “Space Force had its shot,” he said. “They made sure the battle was over our heads rather than the other side of the planet, so we owe them one for that. It will be our turn in a little more than half an hour. They’ll shoot at our guns first, so everybody get in your armor. Primary target is their assault carriers, secondary is their bombardment ships. And for god’s sake, protect your mirrors! Good luck. Time for the artillery to shine. Castillo out.”
     It actually took an hour; the Hans were careful in forming up for their bombardment runs on Sequoia. They could either bunch up their fleet and do a massive strike on the surface every three hours, or spread out and keep up continuous fire, never giving the Americans on the surface a breather.
     They chose to concentrate their force.
     “Han ships moving in range,” said the battalion sensor officer over the comms net.
     Half the Chinese ships, including the assault carriers, hung back above 10,000 kilometers. The rest moved to a 6,000-klick orbit and kept descending. At that range, the artillery’s firepower far exceeded that of the Hans; the Chinese needed to get closer to use their bombardment lasers effectively.
     “All guns, target Bandit-3 and fire at will,” Montaño transmitted. “Two second duration.” Bandit-3 was the Wuhan, a battlecruiser, likely the Chinese flagship. Rand relayed the command to his gun crews, heard acknowledgements from all four.
     Sixteen of the battalion’s 18 cannon fired (two had been down for service when the battle started); their invisible, infrared beams were joined by shots from the other laser cannon buried across the continent. Several had to burn through overhead clouds, and the thunder of scorched air rolled across the surface of Sequoia.
     Almost all of the beams struck the Wuhan in the nose; a few, betrayed by faults in their targeting software or mirror-control machinery, simply missed. The Wuhan was well-armored, but the beams drilled multiple holes in her. Giant sparks of plasma exploded outward from the point of impact; at the same time, a second set of sparks exploded on the ship’s starboard rear quarter – at least one laser had burned all the way through.
     Cheers resounded. One of Rand’s operators shouted over them.
     “Counterbattery fire coming in!” A nervous pause as weak beams played across the Sequoia, aiming for mirrors even as they descended beneath the surface. “All guns reporting nominal. No damage.”
     More cheers. Rand watched his screen as his guns cooled for the next shot. Ten seconds, and a second barrage punished the Wuhan again. One laser touched part of her cooling system; an explosion of superheated lithium punched outward through the hull. The ship’s nose looked like Swiss cheese. The ship tumbled end over end.
     A kill! We might actually win this, Rand thought. Somebody called out over the comms net that the ship was burning out of control and would likely break up in Kuan Yin’s atmosphere.
     Then, “Vampire! (military brevity code for "Hostile antiship missile") Radar shows multiple kinetics inbound to our position from orbit!”
     Montaño’s voice: “Target on the kinetics.”
     That’s their plan, Rand thought. They must have launched missiles from high up, and timed their assault so we’d have to deal with them. Their timing wasn’t perfect, or else we wouldn’t have nailed that battlecruiser as well as we did.
     Scores of missiles entered the atmosphere above Sequoia. Battle computers analyzed their trajectories and noted their likely targets: the spaceports, government offices, and the bases of the 33rd Brigade.
     The artillery made a good accounting of itself, wiping out most of the missiles high above the surface. Some debris rained to the planet below, crashing into houses and lighting vast fires. Three missiles got through and destroyed the remote railway junction connecting Cottonwood to the other cities on the continent.
     But the weapons had also provided the necessary cover for the Han fleet; its orbit took it to the far side of the planet, where the few surviving U.S. satellites spotted it lowering its altitude preparing for a bombardment pass.
     During the respite, Rand let his crews take breaks in turns, allowing them to stretch, go to the bathroom and score some food, but he did not rise from his seat, even as the Vampire call came yet again.
     The Hans had timed their second bombardment pass with another wave of descending missiles. The ships and missiles “rose” over the far side of Sequoia first, leaving Rand and his guns to wait until they were higher in his sky.
     Reports came in from the other side of the continent, and the news wasn’t good. The Hans now had a good track on the locations of the American artillery stations, and bombarded them relentlessly. Lasers pounded mirrors as soon as they rose from the ground; missiles with penetrators burrowed into surface, seeking and finding the cannons emitters and batteries. The fire from the surface of Sequoia slackened …
     … and suddenly Rand’s unit was targeted. The lasers came first, burning across the landscape, aiming at known points where mirrors had surfaced thus far in the battle. Several bombardment beams found their targets, digging through the cupola armor and wrecking the mirrors below. The battalion’s radar also took a hit; computer-run telescopes would have to manage targeting going forward. Miss B*tch lost three mirrors; California Girl lost two.
     Rand, angry, tapped his handheld, called Alpha Dawg’s commander. “I’m taking your gun off defensive fire,” he told the junior sergeant. “I want to kill some Hans.” He looked over the list of ships in his sky and targeted a vulnerable-looking frigate that was contributing to the fire above him.
     The gun got two one-second shots off in thirty seconds. Laser fire from the frigate stopped, but two other ships targeted Alpha Dawg. The gun lost half its mirrors in a minute.
     Rand’s boss, Captain Groves, was in another underground control center 20 klicks away, but her shout came through crystal clear over the comms system.
     “Castillo, put your guns back on the designated target matrix, now! And don’t deviate from it again!”
     Rand knew better than to argue. He’d gotten his lick in …
     A corner of his screen started flashing. A moment later, the battery targeting officer called him.
     “Rand, several inbound kinetics are changing course toward your location. I think you p*ssed them off.”
     Groves’ voice, low with frustration: “Updating target priority matrix.”
     The battery’s remaining lasers targeted the inbound missiles, but it was clear that the defenses were wearing down. Several missiles dropped decoys, further complicating the defenders’ efforts. Chinese lasers took out more and more mirrors; missiles were still dying, but they were getting closer to the surface before being shot down. After a few minutes, California Girl was completely offline, her octet of mirrors shattered. Alpha Dawg had three mirrors left; Miss B*tch had two – Rand was bizarrely pleased to note that the mirror at the just-repaired hatch was among them. Most of the other gun platoons were in the same shape or worse.
     Rand hoped the guns would hold on until the Han fleet set over the planet; then his crews would have time to replace some of the damaged mirrors.
     Then the call came in: “More missiles inbound!”
     There weren’t enough lasers to stop them all.
     A penetrator warhead slammed into the ground just above Alpha Dawg, which was about 50 meters from Rand’s control room. It dug into the earth below. The earth collapsed into the cannon’s emitter, burying it under tons of dirt and rock.
     A roar filled Rand’s ears. In the control room, computer screens died, and everything went dark, save for the small blue glow from self-powered handhelds. A cloud of dust washed over him.


Boots On The Ground

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Deploying To Planet

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Exotic Attacks

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Divide and Conquer

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Internal schism

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Biological Warfare

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Von Neumann Machine

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Killer SETI

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The Web of Hercules

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