Atomic Rockets

Antimatter

Any Star Trek fan can tell you that when it comes to the most bang for your buck, you can't beat antimatter (sometimes called "Contra-terrene" or "Seetee"). How much bang? Well, in theory if you mix one gram of matter with one gram of antimatter you should get 1.8e14 joules of energy or about 43 kilotons.

Why 1.8e14 joules? Surely you remember Einstein's famous E = Mc2. c is the speed of light which is 299,792,458 meters per second. Squared it is 89,875,517,900,000,000 or about 9.0e16. M is mass in kilograms and E is energy in joules. So 0.002 kilograms (2 grams) times 9.0e16 equals 1.8e14 joules. QED.

Once more, to get some idea of the amount of damage represented by a given amount of Joules, refer to the Boom Table.

And remember from the discussion about nuclear weapons that there are 4.184e12 joules in a kiloton and 4.184e15 joules in a megaton. So simply:

Ekt = M * 42961.6

Emt = M * 43.0

where:

  • Ekt = total annihilation energy (kilotons)
  • Emt = total annihilation energy (megatons)
  • M = mass of antimatter (kilograms) Please note that M is the mass of antimatter, NOT the mass of the matter + the antimatter.

If you are interested, 42961.6 is from (9.0e16 * 2) / 4.184e12 where 9.0e16 = c2, 4.184e12 = joules in a kiloton, 2 = 1 unit of matter + 1 unit of antimatter.

Efficiency

But in practice it ain't gonna be anywhere near that much. The trouble is trying to use this as a bomb. It is much easier to extract all the energy from a matter-antimatter reaction if you do it in a slow controlled fashion, say in a power plant or a propulsion system. An antimatter particle beam is more difficult. Making an explosion (in vacuum) is downright hard.

Consider two bricks, one of matter and one of antimatter. Watch as they hit each other. The atoms and antiatoms just on the surface will come into contact and annihilate each other. This creates an explosion. Which is perfectly placed to push the two bricks apart with incredible force, preventing the rest of the atoms and antiatoms from coming into contact. (Actually it will probably vaporize the bricks and blow the vapor away, which amounts to the same thing.)

You may get close to 100% of the antimatter reacting if you, say, drop the antimatter chunk onto a planet, but getting that efficiency with a warhead exploding in the matter-less depths of deep space is much more difficult. You may be lucky to get 10%. Naturally as the state-of-the-art of antimatter warhead design advances, this percentage will rise.

The second problem is that not all the energy from the blast is dangerous. Some of it is in the form of neutrinos, which are utterly harmless (you know, those slippery little customers who can fly through one light year of solid lead like nothing is there).

First off, a particle will only annihilate with the corresponding anti-particle. This means if an electron hits an anti-proton, they will just bounce off each other (actually, protons and antineutrons sometime annihilate, and vice versa).

The good news for antimatter bomb makers is that electron-positron annihilations create flaming death in the form of a pair of deadly gamma rays. However, this is tempered by the unfortunate fact that electrons and positrons are approximately 1/1836 the mass of protons and other nucleons, and there are about 2.5 times as many nucleons as electrons. This means we can more or less ignore the energy contribution from electron-positron annihilation.

The trouble is with proton-antiproton annihilations. This produces (on average) two neutral and three charged pions. The neutral pions cooperate by almost instantly decaying into gamma rays.

The charged pions though, are a pain in the posterior, er, ah, behave most inconveniently. Assuming that they are zipping along at about 0.94c, they will on average only make it to about 21 meters from ground zero before decaying into mostly harmless muons and neutrinos. If the intended target is farther away than that, the blast energy that is composed of charged pions is totally wasted. Accurate figures are hard to come by, but from what I've managed to dig up, something like 30% of the energy from proton-antiproton annihilation is going to be wasted as harmless muons and neutrinos. At worst, 4/9ths of the energy (44.4%) will be deadly (3/9ths are the helpful neutral pions decaying into gamma rays, 1/9th are muons decaying into electrons). At best, 100% of the energy will be deadly. My expert said that the deadly energy percent will normally be over 70%. So conservatively one can take 70% as the deadly percent, or optimistically take 85% (the average of 70% and 100%) as the percent. You can read all the gory details here.

Putting it all together, our new (conservative) formulae will be:

EktB = M * 42961.6 * 0.7 * Rf

or

EktB = M * 30073.1 * Rf

EmtB = M * 43.0 * 0.7 * Rf

or

EmtB = M * 30.1 * Rf

where:

  • EktB = deadly blast energy (kilotons)
  • EmtB = deadly blast energy (megatons)
  • M = mass of antimatter (kilograms)
  • Rf = reaction factor, percentage of the matter and antimatter that manages to annihilate before the rest is blown apart. 1.0 if you are an optimist, 0.1 if you are a pessimist, or a point in between that varies according to the technological level of the bomb-maker.
Example

Given a warhead with one gram of antimatter, an optimist will say it will blow up with a force of 0.001 * 30073.1 * 1.0 = 30.1 kilotons and a pessimist will say 0.001 * 30073.1 * 0.1 = 3.0 kilotons.

Also note that, for the most part, antimatter particle beam weapons are a waste of good antimatter.

As a side note, SF Author Colin Kapp often had ships armed with "Diffract Meson" warheads, presumably based on an as-yet undiscovered scientific principle. I always thought that there was some room for a warhead type in between the 10% efficient thermonuclear warhead and the 100% efficient antimatter warhead. Say Diffract Meson warheads are 50% efficient.

Annihilation Notes

The gamma-ray flux from an antimatter annihilation can be strong enough to transmute some elements into radioactive isotopes. This happens by the photoneutron process. The cross-section of this is quite low, but the gamma-ray flux can be quite high. And I am also informed that the charged pions may be short-lived, but they have a high cross-section and will do all sorts of interesting things to atomic nuclei. Apparently the higher the mass of the element transmuted, the longer lived it is as a radioisotope. I will get back to you when I manage to find some hard numbers.

As a side note, electron-positron annihilation produces two gamma rays with precisely an energy of 511 keV. Which means this is a dead giveaway for antimatter use. As you zip along in your antimatter powered rocket, everybody within a couple of light-years will be able to see a fool broadcasting the fact that their rocket contains militarily significant amounts of antimatter. If you head towards an alien race's home planet, you may inadvertently frighten them into giving you a very hot reception.

Containment

Unsurprisingly, it is very difficult to safely contain antimatter. Earnshaw's theorem proves that no set of static charges can be used to create a stable trap. The best you can do is metastable, and the vast majority of configurations are actively unstable. You need to cheat with nonstationary fields, as in a 'Paul Trap'.

Dr. Robert Forward spoke of storing antimatter in the form of a frozen snowball of anti-hydrogen at temperatures below two Kelvin, levitated in a magnetic field to avoid contact with the chamber wall. In a vacuum, of course. The cold temperature is to keep the blasted stuff from sublimating any anti-atoms from the surface and starting an annihilation reaction with the chamber. There will be some infrequent annihilation events caused by stray cosmic rays, but these should not be a problem.

If you are using your ball of antimatter as a fuel source instead of a bomb, Dr. Forward suggests extracting antimatter fuel from the chamber by using ultraviolet lasers. The lasers ionize a bit of anti-hydrogen from the snowball, which is captured by tailored electrostatic fields and piped to the engine. To insure the snowball's mass is not removed asymmetrically (which would destabilize the magnetic levitation), it is spun on its axis while under the laser.

Current particle accelerators are horribly inefficient at generating antimatter, but Dr. Forward says this is because they were designed by physicists, not industrial engineers. He is of the opinion that a dedicated antimatter factory built with current technology could approach 0.01% efficiency (which isn't good but is still about 6000 times better than Fermilab). The theoretical maximum is 50% efficiency due to the pesky Law of Baryon Number Conservation (which demands that when turning energy into matter, equal amounts of matter and antimatter must be created).

Relativistic Weapons

For relativistic combat between Bussard Ramjet starships, go here.

Relativistic weapons are kinetic-kill weapons where the projectile moves faster than 14% the speed of light (42,000 kilometers per second or so) although the real fun doesn't start until about 90% the speed of light. Refer to the gamma chart. They are sometimes called "R-bombs." Such weapons do incredible amounts of damage, but by the same token they require absurd amounts of energy (refer to second equation below). They are very likely to remain science-fictional for centuries to come.

Even more so than kinetic-kill weapons, an actual warhead adds very little to the total damage inflicted. Note that at 86.6% the speed of light the amount of kinetic energy is equal to the rest mass, which means that the projectile will inflict upon the target the same energy as if it was composed of pure antimatter. Well, actually it will just contain that much energy, as Ken Burnside mentions about kinetic penetrator effects, in many cases the projectile will penetrate the target and exit the back of the ship while still containing joules of damage it failed to inflict on the target.

At such speeds, the kinetic kill equation is no longer accurate. Instead, the following equation is used. Remember that this not only tells how much kinetic damage the projectile will do to the target, it is also the minimum amount of energy the weapon will consume when it fires a round.

Again, to get some idea of the amount of damage represented by a given amount of Joules, refer to the Boom Table.

Ker = ((1/sqrt(1 - (V2/C2))) - 1) * M * C2

Ker = ((1/sqrt(1 - (V2/9e16))) - 1) * M * 9e16

Ker = ((1/sqrt(1 - P2)) - 1) * M * 9e16

where:

  • Ker = relativistic kinetic energy (Joules)
  • M = mass of projectile (kg)
  • V = velocity of projectile relative to target (m/s)
  • P = velocity of projectile relative to target (percentage of c, e.g., three quarters lightspeed = 0.75)
  • C = speed of light in m/s = 3e8

And as before

Wp = Ker * (1 / We)

where:

  • Wp = power required by weapon to fire one projectile (Joules)
  • Ker = kinetic energy of one weapon projectile (Joules)
  • We = efficiency of the weapon (0.0 = 0%, 1.0 = 100%)
Example

How much damage would the 7 kilograms of used kitty litter from Sneaky the cat's litterbox inflict if it was traveling at a velocity of 90% c?

Ker = ((1/sqrt(1 - P2)) - 1) * M * 9e16

Ker = ((1/sqrt(1 - 0.92)) - 1) * 7 * 9e16

Ker = 8.2e17 Joules, about 195 megatons.

Not bad, for kitty litter.

But a civilization that does gain the ability to create relativistic kinetic-kill weapons becomes a deadly threat to any and all alien civilizations in range.

Poor Man's R-Bomb

Iain Paterson did some calculations which produced some surprising results.

I had this image of putting a relatively small payload on top of a bloody massive conventional booster and firing it of -- the poor mans R-bomb i guess -- but after looking at some calculations this doesn't look likely.

From the kinetic energy equation and Tsiolkovsky's equation you get:

E = 1/2 * Mpayload * (Vexhaust * ln(R))2

E = 1/2 * (Mtotal / R) * (Vexhaust * ln(R))2

Differentiating with respect to R and setting equal to zero gives the mass ratio that gives the maximum energy. Canceling terms gives that:

R = E * 2

Vfinal_Ideal = 2 * Vexhaust

This is rather surprising to me though I suppose it makes sense: at higher velocities there is a greater kinetic energy per mass but it requires a huge amount of fuel to get to that velocity. After reaching this velocity any additional acceleration REDUCES the energy impacted on the target so you might as well shut off the engines and let it coast.

I worked it out for other cases as well, for 2 ships that are approaching each other before one fires a missile you get

R = e(2-γ)

where γ (gamma) is the ratio of the approach velocity to the exhaust velocity although this again gives that the missile should impact with a relative velocity of twice its exhaust velocity.

The final case is for relativistic velocities (although being fired from ships that are stationary with respect to each other otherwise the maths is really nasty!) and you get:

R = ((c + Vexhaust) / (c - Vexhaust))2

Vfinal_ideal = 2 * Vexhaust / (1 + (Vexhaust / c)2)

note that for V«c, Vf = 2 * Vexhaust. And for V~c, Vf = c.

So is it just me or does this completely defy the concept of the poor-mans R-bomb so that instead it requires some sort of some handwavium total-conversion drive?

Also this shows that to be effective a kinetic-missile must have a high exhaust velocity, not just a lot of fuel. While I suppose in order to evade point defense they need to be going faster but every extra second of thrust would reduce the damage inflicted to the target.

Iain Paterson

Mr. Paterson is optimizing a more plausible scenario. His "poor man's R-bomb" is constrained by a particular exhaust velocity, and the question is how to squeeze the maximum kinetic energy into the payload. I'm not sure whether his analysis is correct, but it seems plausible.

The optimum energy efficiency would actually be reached at an terminal velocity equal to the exhaust velocity. But that doesn't seem to be the objective of the poor man's R-bomb. The poor man's R-bomb seems to be limited by loaded mass rather than energy budget. You don't use any sacrificial propellant at all, you just use pure fuel at the maximum exhaust velocity you can manage all the way.

Mr. Paterson writes: So is it just me or does this completely defy the concept of the poor-mans R-bomb so that instead it requires some sort of some handwavium total-conversion drive?

His conclusion is essentially correct, if we assume the poor man's R-bomb must be internally powered.

Still, this is nothing new to those of us who have seriously considered the problem of fast interstellar propulsion. We gave up on the idea of internal power for fast interstellar propulsion years ago, on the pretty obvious grounds that no fuel has a sufficient (usable) energy density. If you want to reach high relativistic speeds, you should use external power--either in the form of a laser beam or particle beam or "runway" track or relativistic kinetic impactors.

Isaac Kuo

The Killing Star

From The Killing Star by Charles Pelligrino and George Zebrowski (you really should read this book):

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

Space Hackers

Spacecraft in a war zone had better have military-grade firewalls on their internal computer networks. Space hackers can try to crack the network through a radio link and issue a variety of computer commands. Such as vent the atmosphere, scram the reactor, or induce the warheads in the magazine to detonate. Not to mention uploading all the classified information in the data banks. This is an old trick, seen in such movies as The Wrath of Khan (where Admiral Kirk uses the "prefix code" to turn off the deflectors on Khan's ship), Independence Day, TV shows like the latest incarnation of Battlestar Galactica (where the Galactica's computers are NOT networked since the Cylons are just a little too good at hacking), and in novels such as Vernor Vinge's A Fire Upon The Deep, Ken MacLeod's The Cassini Division and James P. Hogan's Giant's Star.

Paul Zimmerle points out that Battlestar Galactica does get the threat slightly wrong. It is not networked computers per se that are at risk, it is computers with some kind of data connection to the outside world that is the threat. Removing the network connection just slows the rate of contagion.

The strain on the Command Deck of the Shapieron had been hovering around breaking point for days. Eesyan was standing in the center of the floor gazing up at the main display screen, where an enormous web of interconnected shapes and boxes annotated with symbols showed the road map into JEVEX that ZORAC had laboriously pieced together from statistical analyses and pattern correlations of the responses it had obtained to its probe signals. But ZORAC was not getting through to the nucleus of the system, which it would have to penetrate if it was going to disrupt JEVEX'S h-jamming capability. Its attempts had been repeatedly detected by JEVEX'S constantly running self-checking routines and thwarted by automatically initiated correction procedures. The big problem now was trying to decide how much longer they could allow ZORAC to try before the tables of fault-diagnostic data accumulating inside JEVEX alerted its supervisory functions that something very abnormal was happening. Opinions were more or less evenly divided between Eesyan's scientists from Thurien, who already wanted to call the whole thing off, and Garuth and his crew, who seemed willing to risk almost anything to pursue what was beginning to look, the more Eesyan saw of it, like some kind of death wish.

"Probe Three's function directive has been queried for the third time," one of the scientists announced from a nearby station. "Header response analysis indicates we've triggered a veto override again." He looked across at Eesyan and shook his head. "It's too dangerous. We'll have to suspend probing on this channel and resume regular traffic only."

"Activity pattern correlates with a new set of executive diagnostic indexes," another scientist called. "We've initiated a high-level malfunction check."

"We have to shut down on Three," another, standing by Ecsyan, pleaded. "We're too exposed as it is."

Eesyan stared grimly up at the main screen as a set of mnemonics unrolled down one side to confirm the warning.

"What's your verdict, ZORAC?" he asked.

"I've reduced interrogation priority, but the fault flags are still set. It's tight, but it's the nearest we've come so far. I can try it one more time and risk it, or back off and let the chance go. It's up to you."

Eesyan glanced across to where Garuth was watching tensely with Monchar and Shilohin. Garuth clamped his mouth tight and gave an almost imperceptible nod. Eesyan drew a long breath. "Give it a try, ZORAC," he instructed. A hush fell across the Command Deck, and all eyes turned upward toward the large screen.

In the next second or two a billion bits of information flew back and forth between ZORAC and a Jevienese communications relay hanging distantly in space. Then, suddenly, a new set of boxes appeared in the array. The symbols inside them were etched against bright red backgrounds that flashed rapidly. One of the scientists groaned in dismay.

"Alarm condition," ZORAC reported. "General supervisor alert triggered. I think we just blew it." It meant that JEVEX knew they were there.

Eesyan looked down at the floor. There was nothing to say. Garuth was shaking his head dazedly in mute protest as if refusing to accept that this could be happening. Shilohin moved a step nearer and rested a hand on his shoulder. "You tried," she said quietly. "You had to try. It was the only chance."

Garuth was staring around him as if he had just awakened from a dream. "What was I thinking?" he whispered. "I had no right to do this."

"It had to be done," Shilohin told him firmly.

"Two objects a hundred thousand miles out, coming this way fast," ZORAC reported. "Probably defensive weapons coming to check out this area." It was serious. The screen hiding the Shapieron would never stand up to probing at close range.

"How long before we register on their instruments?" Eesyan asked hoarsely.

"A couple of minutes at most," ZORAC replied...

..."So this is our ultimatum to you: either you withdraw from Thurien now, and agree to place your entire military command under our jurisdiction unconditionally, or the Thuriens will transfer through to Jevlen a combined Terran force that will blow you to stardust - you, your whole planet, and that laughable aggregation of scrap that you call a computer network."

Somewhere deep inside JEVEX something hiccupped. A million tasks that had been running inside the system froze in the confusion as directives coming down from the highest operating levels of the nucleus redefined the whole structure of priority assignments to force an emergency analysis of the new data. And in the middle of it all, the routines that had been scanning for inquisitive probes through h-space faltered. It was only for a few seconds, but...

..."It's busy," ZORAC's voice answered. "Don't ask me what's happened, but yes it was. Something deactivated the self-checking functions, and I've switched off the jamming routine. We're through to Thurien."

While ZORAC was speaking, VISAR decoded the access passwords into JEVEX's diagnostic subsystem, erased a set of data that it found there, substituted new data of its own, and reset the alarm indicators. Inside the Jevienese Defense Sector Five control center, a display screen changed to announce a false alarm caused by a malfunctioning remote communications relay. Far off in space, the two destroyers turned away to return to their stations and resume routine patrolling. Already VISAR was pouring volumes of information into JEVEX that it had not time to explain, not even to ZORAC. At the same time it broke its way into JEVEX's communications subsystem and gained control of the open channel to Earth.

From Giant's Star by James P. Hogan (1981)

And never lose sight of the reason for haste: the frigate. It had switched to rocket drive, blasting heedless away from the wallowing freighter. Somehow, these microbes knew they were rescuing more than themselves. The warship had the best navigation computers that the little minds could make. But it would be another three seconds before it could make its first ultradrive hop.

The new Power had no weapons on the ground, nothing but a comm laser. That could not even melt steel at the frigate's range. No matter, the laser was aimed, tuned civilly on the retreating warship's receiver. No acknowledgement. The humans knew what communication would bring. The laser light flickered here and there across the hull, lighting smoothness and inactive sensors, sliding across the ship's ultradrive spines. Searching, probing. The Power had never bothered to sabotage the external hull, but that was no problem. Even this crude machine had thousands of robot sensors scattered across its surface, reporting status and danger, driving utility programs. Most were shut down now, the ship fleeing nearly blind. They thought by not looking that they could be safe.

One more second and the frigate would attain interstellar safety.

The laser flickered on a failure sensor, a sensor that reported critical changes in one of the ultradrive spines. Its interrupts could not be ignored if the star jump were to succeed. Interrupt honored. Interrupt handler running, looking out, receiving more light from the laser far below... a backdoor into the ship's code, installed when the newborn had subverted the human's groundside equipment...

...and the Power was aboard, with milliseconds to spare. Its agents - not even human equivalent on this primitive hardware - raced through the ship's automation, shutting down, aborting. There would be no jump. Cameras in the ship's bridge showed widening of eyes, the beginning of a scream. The humans knew, to the extent that horror can live in a fraction of a second.

There would be no jump. Yet the ultradrive was already committed. There would be a jump attempt, without automatic control a doomed one. Less than five milliseconds till the jump discharge, a mechanical cascade that no software could finesse. The newborn's agents flitted everywhere across the ship's computers, futilely attempting a shutdown. Nearly a light-second away, under the gray rubble at High Lab, the Power could only watch. So. The frigate would be destroyed.

So slow and so fast. A fraction of a second. The fire spread out from the heart of the frigate, taking both peril and possibility.

From A Fire Upon the Deep by Vernor Vinge (1992)

EMP Weapons

These are designed to create strong electro-magnetic pulses designed to fry electronics and electrical equipment. Many e-bomb designs are not nuclear, they use a conventional high-explosive charge in an armature to generate the pulse. These tend to be short range, on the order of hundreds of meters, and they do obey the inverse square law. The defense is enclosing all electrical devices in Faraday cages. It is amusing to note that vacuum tube technology is much less vulnerable to EMP than are transistors.

Fiber optic cables are immune to EMP, unfortunately they are not shock tolerant. Specifically they have poor shear tolerance. Fiber can withstand a certain amount of flex, but it's resistance to "instantaneous flex" (like you'd see with a conventional missile hit) is not good. Ordinary twisted pair wires will stretch with the displacement from the explosion (assuming a hit close enough to warp the local supports but far enough not to directly break the cables) but are vulnerable to EMP. A sharp strike, bend or flex to fiber optic cable will shatter the individual strands across the grain, and destroy the cable.

Conventional nuclear weapons will also produce an EMP under certain circumstances.

Propulsion Systems

If your spacecraft's exhaust is pumping out a few terawatts, it might occur to you that your enemy would be real unhappy if you hosed them with your tail flame.

This is called "The Kzinti Lesson", from a Larry Niven short story called "The Warriors". Most science fiction fans have the mistaken belief that Niven first came up with the idea, even though E. E. "Doc" Smith invented the concept six years earlier in 1960, in a chapter of his novel Masters of the Vortex entitled Driving Jets Are Weapons.

The Kzinti Lesson states:

Kzinti Lesson

A reaction drive's efficiency as a weapon is in direct proportion to its efficiency as a drive.

Larry Niven

The warlike Kzinti invaded the solar system, figuring that humanity would be a pushover since the pacifist humans of the time had no weapons. Humans showed the Kzin the error of their ways by annihilating Kzinti warships with laser arrays used for solar sails, multi-million degree fusion exhausts, and photon drives that were basically titanic lasers. The humans did indeed have no weapons, technically. But any machine with that much energy at its disposal can be re-purposed.

So keep in mind that the higher the exhaust velocities of the rocket engine, the more damage it will do to anything unfortunate enough to be in the path of the exhaust.

Having said that, realize that as a general rule propulsion exhaust is poorly collimated, which means after a very short range it will have expanded and dissipated into harmlessness.

For examples of this in science fiction, consult the ever informative TV Tropes under Weaponized Exhaust.

This is a more general concern. As propulsion systems get more powerful, the more energy they contain, and the worse the damage if an accident occurs. How would you like to have the captain of the Exxon Valdez skippering a tramp freighter with an antimatter drive? That brilliant mushroom cloud you see marks the former location of Clinton-Sherman spaceport. The more devastation a propulsion system can wreck, the shorter the leash the captains will be on. If they are too powerful, there won't be any colorful tramp freighters or similar vessels. This is known as Jon's Law.

Any army man can tell you it is an extraordinarily bad idea to stand directly behind an MLRS or any other rocket-propelled weapon. The backblast will cook you. And a soldier firing a man portable rocket weapon had better not have a wall close behind, or the wall will reflect the flaming backblast all over the stupid soldier.

Sometimes it works the other way. If you are attacking an Orion drive spacecraft with nuclear warheads, they will just point their pusher plate at the missiles and laugh at you. Though come to think, any propulsion system that uses a stream of detonating nuclear warheads should be easy to weaponize. In Larry Niven and Jerry Pournelle's Footfall they use the x-ray bursts from nuclear propulsion charges to pump x-ray lasers. TV Tropes calls that "Exhaustized Weapons".

In The Outcasts of Heaven's Belt by Joan Vinge, warships attacking a visiting Bussard Ramjet starship get a rude surprise when the starship shows them its tail. The starship's fusion drive is quite deadly at close range. Things are more extreme in the anime Space Battleship Yamato (later watered down and made politically correct for viewers in the US under the name Star Blazers). The battleship's propulsion system is the incredibly powerful "wave-motion engine". But if attacked, the thrust is vectored out the nose of the ship to create the equally incredibly powerful "wave-motion cannon".

In the Space 1999 episode "Voyager's Return" the hapless inhabitants of Moonbase Alpha are alarmed to see the infamous Voyager One space probe approaching. The probe's propulsion system is the dreaded "Queller Drive", which uses a deadly radioactive stream of fast neutrons. The first test of the Queller drive accidentally killed everyone at a lunar colony. Lucky for the Alphans the inventor of the drive is actually hiding in Moonbase Alpha in a version of the witness protection program, since everybody who had relatives at the dead colony wants to kill him. Dr. Queller manages to turn Voyager off before it can fry everybody in Alpha.

But things go from bad to worse when they notice three alien warships following Voyager. As it turns out the aliens are seeking vengeance for millions of their citizens who were killed when the incompetently programmed Voyager One came blundering through their empire. Voyager One was programmed to turn off the Queller drive so as to avoid torching any inhabited planets, but Dr. Queller's software had a few bugs.

Anti-Kzinti Lesson

Jonathan Cunningham notes that sometimes the opposite is true as well.

Anti-Kzinti Lesson

A weapon's output is in direct proportion to its potential as a maneuvering thruster.

Jonathan Cunningham

The effect is strongest with kinetic kill weapons of course, but will still be noticeable with particle beam weapons or even lasers. It will be less of an issue for missile launchers, assuming the missile don't begin full thrust until after they've left the tubes.

Any force acting through the center of a body affects the movement of that body. Any force acting anywhere else on a body will affect its rotation. The more powerful the beam, the stronger the thruster effect. The further away from the center of mass, the greater the lever arm, and the greater the rotational effect.

So when the Space Cruiser Virtuous has X turret cuts lose with a high energy broadside against the flagship of the Insidious Empire, the ship starts spinning until it comically slices its own escorts in half. The Despicable Lord cackles and returns fire from one of several fixed mounted emplacements, each one aligned through the center of mass, likes quills on a porcupine. Foolish humans...

TV Tropes calls this concept "Exhaustized Weapons".

Of course, if the weapon has low power compared to the mass, or fires in a short enough burst the effect is minimized. But not removed. During the Apollo 13 mission, NASA was mystified as to why the powerless craft kept drifting off course. It turns out that normal, periodic venting of water was enough to strike panic in the hearts of distant controllers who gasped, "Now what?"

Space Fighters

I know all you Battlestar Galactica fans are not going to want to hear it, but looking from a cost/benefit analysis, space fighter craft do not make any sense. Go to the Future War Stories blog and read the post Hard Science Space Fighters, read the entry in the The Tough Guide to the Known Galaxy "SPACE FIGHTERS", and the essay in Rocketpunk Manifesto Space Fighters, Not. You might also want to review the section on Respecting Science. On the TV Tropes website there is a nice analysis of possible situations where space fighters might just possibly make sense.

Fighters substantially outperforming big ships can be justified, though. Big ships (presumably) need crew habitability for extended voyages, fuel for same, usually an FTL gizmo, and crew including maintenance types, etc. All of which are mass penalties. A fighter is pretty much just drive engine, enough delta v for its mission profile, minimal habitability for a minimal crew, and ordnance carried.

Being a spoil-sport, I said:

The question then becomes why doesn't the designers replace the minimal habitability crew space with some electronics and turn the fighter into a missile bus.

Mr. Robinson answered with:

What a rude question. {grin}

But then he got me, by invoking Burnside's Zeroth Law of Space Combat. SF fans don't want to read about the life and times of a nuclear missile, therefore space fighters will exist.

In the 1970's, DARPA was looking into a crude spacecraft called the "High Performance Spaceplane" that looked suspiciously like a space fighter, you can read about the details here and here. However, it was more like a manned missile than it was a Viper from Battlestar Galactica.

Four things have triggered a growing interest in the real possibility of a space fighter:

  • The NASA Space Transportation System, otherwise popularly known as the space shuttle, proved once and for all that it was possible to orbit a manned winged space vehicle and return it safely to an aircraft-type landing for re-use.
  • The Lockheed SR-71 Blackbird Mach-3 high-altitude spy plane has since 1962 shown that such high-speed high-altitude manned reconnaissance vehicles had utility beyond what could be accomplished by unmanned orbiting recon satellites.
  • The Soviet Union began testing a small winged reuseable "spaceplane" in about 1976. (ed note: the MiG-105 "Spiral". Cancelled in 1978)
  • The development of the simple "space cruiser" concept by Fred W. "Bud" Redding, an aerospace designer with the DCS Corporation, caught the eye of the United States Air Force because of an article about it by this author in the November 1983 issue of Omni magazine. (ed note: the DARPA "High Performance Spaceplane" mentioned above)

These things are leading to the impending birth of the space fighter. Quite apart from the utility of a space fighter in outer space itself, the vehicle has a definite series of missions it can perform in close proximity to the Earth. Students of aviation history as well as military history knew that early airplanes co-opted the role of the horse cavalry in scouting as well as general harassment of the enemy's rear because of mobility and use of the principle of surprise. Only later did aircraft also assume the role of load-carriers, vehicles capable of delivering either cargoes or bombs over ranges far beyond those of ground vehicles or artillery guns. Helicopters have taken over the tactical scouting and harassment roles today on the battlefields of Earth, but aircraft have kept the art of scouting, harassment, and load delivery alive by doing these things at higher and higher altitudes and faster and faster speeds. The space fighter concept extends them into space itself, but a space fighter must not be considered a load-carrier like the space shuttle orbiter.

The operational requirements for a space fighter, especially the ones we're likely to see in the next 25 years, are simple to set forth and not technically as difficult to achieve as might be assumed. A space fighter should be capable of being launched on a few minutes' notice from the surface of Earth, from an airborne platform, or from a space facility such as the space shuttle or a space base. It should be capable of entering any orbit and making several changes of orbital altitude and inclination. It should have suitable aerodynamic characteristics—primarily a high ratio between lift and drag—so that it can maneuver in the upper atmosphere of the Earth by means of aerodynamic controls, primarily stubby delta wings.

Thus, the space fighter should be able to appear suddenly in the high atmosphere over any nation at any time moving in any direction at a wide variety of speeds. A system of defense against such a space fighter will be extremely expensive in comparison to the cost of the space fighter. In fact, even the detection system necessary to find one and track it will be costly. For operations in the near-Earth orbital region, a capability to change its velocity ("delta-vee") of about 2,500 feet per second (760 m/s) is necessary. For operation in the Earth-Moon system, a delta-vee of 20,000 feet per second (6000 m/s) would be more than adequate.

The space fighter should be a completely self-contained manned vehicle with a life support capability of at least 24 hours. Finally, the space fighter should be able to return to a number of bases or landing sites and terminate its mission in a reusable condition.

In 1965, these requirements were technologically difficult if not impossible. Now they are "state of the art" if clever engineering is used. It looks as though the Soviet Union has already embarked on a "spaceplane" if not a space fighter program with its small shuttle. France is considering the development of the "Hermes," a delta-winged mini-shuttle intended to be launched into low Earth orbit by the Eurospace "Ariane" rocket. And the United States Department of Defense has embarked upon at least two admitted spaceplane or space fighter programs.

An excellent example of this is Fred W. "Bud" Redding's space cruiser or spaceplane, which is being funded by Defense Advanced Research Projects Agency (DARPA) as a research vehicle. The Redding space cruiser is delightfully simple and brings out the machismo in hot fighter pilots. A slender cone about 24 feet long with a base diameter of about five feet, the vehicle is a scaled-up version of the proven Mark 12 Minuteman re-entry vehicle. The aerodynamic characteristics of this shape are very well known and understood. It's a hypersonic and supersonic airframe shape with good lift-to-drag ratio and therefore good maneuverability. And small delta wings, and it becomes highly maneuverable. It's large enough that a single pilot clad in a pressure suit can sit in an unpressurized cockpit in the aft end just ahead of a ring of rocket motors. A hatch that can be opened allows him to stand up in the cockpit to look around. In this "open cockpit" space vehicle, the pilot "owns space" around him.

The nose of the conical spaceplane can be folded back to permit it to become a "pusher" or space tug for shifting larger loads in orbit. With a Centaur underneath it as a lower stage, it is capable of taking its pilot around the Moon and back.

The simplicity of the Redding spaceplane comes from its lack of design compromises. One of the things that makes the space shuttle orbiter so complex is the requirement that it fly well at subsonic, supersonic, and hypersonic speeds. This was a difficult and expensive technological feat requiring many compromises that didn't contribute to low cost and design simplicity. If a spaceplane is designed to fly at only supersonic and hypersonic speeds, it can be greatly simplified. But how can it be landed if it won't fly at subsonic speeds?

The Mark 12 re-entry vehicle is a fine supersonic and hypersonic airframe but a streamlined anvil at subsonic speeds. The Redding spaceplane is the same. But rather than compromise the design by giving it a good subsonic lift-to-drag ratio to permit a horizontal landing, Bud Redding opted to use another simple and straightforward method: a parachute. Not the simple circular parachute used on early Mercury, Gemini, and Apollo space capsules that dropped the capsule into the ocean in an uncontrolled fashion. Instead, Redding suggests the use of the steerable, flyable "parasail" used by thousands of sports parachutists every weekend. Once the spaceplane gets into the atmosphere and its speed slows to subsonic where it becomes a brick, a parasail chute is deployed, allowing the pilot to steer the slender cone to a soft landing inside a fifty-foot circle. It could be landed even on the deck of a ship at sea.

The Redding DARPA spaceplane is almost a technological reality today. But coming down the line very quickly is something the United States Air Force calls the "transatmospheric vehicle" (TAV). This is not a space fighter or a space cruiser. It's conceived as a vehicle larger and more complex than the Redding spaceplane but smaller and simpler than the NASA space shuttle. The TAV would take off horizonally from the runway of any Air Force base, fly into orbit using wings for lift and a combination of turbo-ramjet and rocket engines for propulsion, operate in low Earth orbit, and return at will to land horizonally on the runway of any Air Force base. The TAV may be operation in the 1990s. The Redding spaceplane could be flying in the 1980 decade. Neither of these space fighter-like vehicles will look anything like what anyone thought a space ship would in the annals of science fiction. They won't look like X-wings, Y-wings, TIE fighters. Vipers, Starfighters, or anything else conceived to date in the minds of authors or illustrators. There is one thing for certain: When their appearances become unclassified (like the appearance of the Redding spaceplane already is), artistic interpretations based upon their designs will quickly come to grace not only science fiction book and magazine covers, but also the beautiful full-color institutional ads of aerospace companies—product ads proudly announcing that "HyperTech's Mark Three Solar Powered Laser Gizmoscope was chosen above all others to provide essential on-board services," and numerous backgrounds for national newsmagazine covers.

Beyond the 1999 space fighter, however, the technological crystal ball becomes cloudy. This is not to say that the wildest hallucinations of a Hollywood art director are a better indication of what futuristic space fighters would look like. Probably not, because such concepts are based solely on what looks good and appears to be futuristic. The actual space fighters of the twenty-first century will not only look "right," they will be beautiful in their own way because they'll be designed with a full understanding of the mission requirements of a space fighter based upon realistic military doctrines of space. They will be difficult to operate, dangerous to life and limb, and push human capabilities to their utmost limits just as has every scouting and fighting vehicle (including the horse) throughout history. Far more important in the long run is the inevitable spin-off of space fighter technology into the technology of civilian and commercial spacecraft. Just as the airliners and general aviation aircraft of 1984 use the engines, electronics, aerodynamics, and other technologies pioneered for military aircraft, so the military spacecraft will also contribute toward the accompanying commercial and private use of space. And that possibility is perhaps far more exciting than space fighters themselves. Move over, science fiction. Another of your dreams is about to become reality!

from Afterword: Space Fighers by G. Harry Stine, collected in THE TORCH OF HONOR by Roger MacBride Allen (1985)

The above was written in 1985. Alas no "space fighters" have made an appearance. And unfortunately with current technological advances, it seems more likely that a space fighter developed today will be an unmanned drone, not a Starfury.

Culture

Jack Staik has some further observations:

It is true that in a universe governed by hard-headed practicality and realism, a missile bus or an Honorverse-style missile pod would make more sense. However, there is one factor that would allow manned space fighters to proliferate and even prosper - Cultural Bias!

Practical and realistic concerns have often been swept aside in real life by cultural conditioning - look at Japan's centuries of refusal to modernize or adapt until the fact of their utter vulnerability was shoved down their throats by Admiral Perry.

An aristocratic culture with a leaning toward individual heroism (i.e. Arthurian or Samurai theme) would love the idea of manned space-fighters. Noble warriors with the blood of kings firing up their fighters to challenge the Evil Alien Hordes, one man's courage and missiles against the onslaught ... it's a primal image. The fighters themselves would probably be very individualistic, instead of mass-produced identical, to reflect their aristocratic pilot. And since the space-fighter would be the provenance of only the high-caste persons, the cultural conditioning could keep manned space-fighter a viable concept for generations in even a hyper-realistic scenario.

Of course, in time raw practicality will sweep aside the manned space-fighter, much as it did the armored knight on horseback, but the fighters will still be the emblem of a bygone age of chivalry and romance. And a Don Quixote-type character, pulling an ancestor's old space-fighter out of storage, to take up arms against a threat from the heavens, has lots of storytelling potential.

Jack Staik

However, culture only goes so far. Currently (2012) in Afghanistan, the US Air Force is used to attack partisan forces. But more and more the attacks are carried out by remotely piloted drones, not by valiant Top Gun piloted fighter aircraft. The Air Force pilots are quite angry about this. They are angry that their role is shrinking, they are angry that their chances of flying exciting missions grow slim, they are angry that fat-bottomed desk-jockys controlling a drone from an office in New Mexico are called "fighter pilots" just like them, they are just angry. But culture or no, in 2011 the Air Force said it trained more drone pilots than fighter and bomber pilots combined.

A Cultural Divide

Until recently, most drone operators were regular Air Force pilots. Now, the service is reaching out to people who've never even flown before. And that has caused friction within the Air Force as it tries to redefine what it means to be a pilot.

"There's a cultural divide," says Kelly, a 46-year-old Air Force reservist from Texas who is now a student at Holloman. Kelly grew up wanting to be a fighter pilot, but his vision is not good enough for that job. But he can fly drones. And he says that irks fighter pilots who see themselves at the top of the Air Force pyramid.

"Part of it is an ego ... I hate to say an ego trip, but it is," he says.

The Air Force has been working to bridge the divide between these two groups of fliers. First off, drone operators are called pilots, and they wear the same green flight suits as fighter pilots, even though they never get in a plane. Their operating stations look like dashboards in a cockpit.

But all of that has made tensions worse. Aaron is another Holloman student. He used to fix military communications equipment; now he's training to operate drones.

"There's still a lot of animosity. You see people in a conventional aircrew that wonder why we get to wear the flight suits even though we don't leave the ground, why do we need flight physicals, why do we get incentive pay — stuff like that," he says.

Efficacy

But if you want cold, hard, unglamorous reality, Ken Burnside has plenty of it for you:

The other deciding factor is this: A "fighter" needs to be recovered (ed note: Otherwise it is some kind of manned kamikaze missile).

That means you need delta v to get to the objective, then delta v to cancel out your inbound vector, then delta v to get to a rendezvous point, plus delta v for maneuvering in the thick of things.

A rough estimate was that you needed delta v equal to about four times that of a comparable mass missile that just needs to do a drive-by shooting.

Four times the delta v means that your fuel fraction just went up by a factor of something around four (depends on your Isp).

Now put in the life support compartment, and the payload mass, and it gets even worse; rocket performance is the red queen's race, and you rapidly hit declining efficiencies.

If you could build a TLAM that had the operational range of an F-18, you could probably get more of them packed onto a comparable size ship than a comparable mass of F-18s.

TLAMs require lots of data on the target and the terrain and have to fly "over the horizon". A lot of opposition to the TLAM was that it took away the offensive strike mission from carrier aviation.

In space, there's no horizon to hide behind.

Ken Burnside

On a later occasion, in a discussion on space combat game design, Mr. Burnside went into more detail:

The basic argument for fighters is that people think they're fun and cool.

The basic argument against fighters is horizon distance.

Fighters make sense in surface naval operations because a fighter can go to places where the carrier or cruiser can't. The fighter can also go to places where the big ships can't see, because of the curvature of the earth.

Unfortunately, there's no horizon for targets to hide behind in space. Even if you have something short of everyone sees everyone, it's hard(er) to justify fighters seeing things their carriers can't, just because carriers can carry bigger sensors, and space is a very sensor friendly environment.

Fighters do make sense in an orbital reference frame context, where, well, curvature of the earth matters, and where going into atmosphere matters. But this turns fighter carriers into "brown water" vessels that work in the tide pools of planetary gravity wells, which isn't the role you see them doing in fiction, which tends to take WWII carrier ops or modern USN carrier ops and apply an SFnal veneer.

Note that that's all mission specific, and only mildly tech related.

What do fighters do better than, or exclusively related to, larger ships? Answer this, and you get a reason for fighters in a setting.

In terms of pure offensive firepower, there's very little you can do with a fighter that a cruise missile can't do better in a space game context.

Of course, the best reason to have fighters is because they make your game more funnerer. But it does kind of help to figure out what mission they're doing.

Ken Burnside

Role

Given the popularity of space fighters in such mass media shows as Star Wars, Battlestar Galactica, Buck Rogers in the 25th Century, Babylon 5, and others, they obviously appeal to people. I'm in the minority, but I think they are missing the point. Here's my reasoning:

It seems to me that the space fighter is nothing more that people taking a dramatic and comfortable metaphor (sea-going aircraft carriers and combat fighter aircraft) and transporting it intact into the outer space environment. But if you think about it, interplanetary combat is highly unlikely to be like anything that has occurred before.

Imagine a speculative fiction writer back in the Victorian era, such as Jules Verne. Say they wanted to write a novel about the far future, when heavier than air flight had been invented, and the age of Aerial Combat had arrived.

They might take the dramatic and comfortable metaphor of sea-going frigates and battleships and transporting it intact into the aerial environment. Held aloft by dozens of helicopter blades, the battleships of the air would ponderously maneuver, trying to "cross the T" with the enemy aerial dreadnoughts.

See how silly it sounds? Well, combat spacecraft behaving like fighter aircraft is just as silly. In both cases a metaphor is being forced into a situation where it does not work.

In reality, when the Wright brothers invented heavier-than-air flight and Fokker Triplanes started dog-fighting Sopwith Camels, it was totally unlike anything that had occurred before. Biplanes never ever tried to cross the T, and a sea-going battleship had never ever performed an Immelmann turn.

Therefore, by analogy, when interplanetary combat arrives, it too will be totally unlike anything that has occurred before.

As Ken Burnside puts it:

On the other hand - Winch's analogy to victorian era fiction about flying dreadnoughts and the "Who the hell thought of an Immelmann turn?" question sort of underscores why I want to model how space combat works using known physics as a gameable experience.

It won't be WWII in space. It won't be the Iraq war in space, it won't be subs in the North Atlantic in space. It will be its own unique thing.

To figure out what that unique thing is, you need to understand the environment of space, how it differs from a planetary environment, and once you have those differences modeled, you need to work out the tactics for this new environment, much the same way WWI biplane pilots had to work out the tactics of air to air combat.

Now, it's certain that I've got things wrong with the Attack Vector: Tactical model. When they get pointed out, I fix them. On the other hand, to the best of my knowledge and belief, it's the first serious attempt at trying to model what the tactical environment looks like.

World War II/Battleships/Fighters in space is about as likely to be an accurate model of space combat as, modeling jet air-to-air combat with pike square formations. Attack Vector: Tactical is probably akin to saying that jet fighters behave like World War I biplanes, only faster. It's still likely wrong, but it's probably much LESS wrong.

Ken Burnside

In Fiction

Night Killer II was not a beautiful vessel. Satarii fighters are sleek, polished for planetary re-entry, but a space-based interceptor need not be aesthetic. Had I attempted to land on Lot I would have reached the surface in ashes. Night Killer carried her missiles outside the hull in two cylindrical bundles. Radar sweeps and communication aerials were all exposed. Her drive was set on un-streamlined pylons spaced about her stern while the cockpit glass bulged beyond the curvature of her skin, ostensibly for wider vision with less distortion; the effect on the casual observer was that of a mutated hornet's head. And added to this were bundles of thrusters placed strategically about the hull to aid maneuvering. But regardless of her ungainliness, she remained an effective fighting unit, equal and in some ways more than equal to the darting black war craft of the Satarii.

From Common Denominator by David Lewis (1972)

"Pursuit fighters," I told the Ship. "Easily fast enough to catch one of our boats, if they can do it within their limited range. It's limited because they're the only kind of craft designed for dogfight tactics. They're just enormous multidirectional motors in a spheroid hull with one pilot in the centre and a few missile tubes scattered between the motor vents. Fast maneuvering in space means killing momentum one way as well as building it up in another, so there's murderous acceleration and deceleration every few seconds, with the motor blasting in all directions, eating up hydrogen and putting incredible stress on the pilots. Even with all the aids - liquid suspension cocoons, special suits, body reinforcement, field-shields, the lot - it takes years of training to stand it for more than a few minutes at a time. The American call fighter pilots Globetrotters, for some old game where you had to bounce a ball all the time. I've been in a fighter simulator once - I came out black and blue, and they say the real thing's worse. And that's our hope - that Liang can hold them off, make them maneuver so much they'll have to give up, or just outrun them. That's what he's trying to do now, but he's got to be careful. They mustn't box him in and stop him maneuvering, that'd let them swarm over him like hornets, killing the boat or crippling it till the gunships catch up -"

From Run To The Stars by Michael Scott Rohan (1982)

Alien Technology

If samples of alien technology are encountered, the first thought is that they will be very very valuable. It shouldn't matter if the samples are paleotechnology from an archeological dig of a ten thousand year old Forerunner alien empire site or fragments of an alien warship that survived the most recent border skirmish.

The second thought is that such technology can be very very dangerous. Especially if the aliens seem more technologically advanced that you are. Even if the items are not deliberately booby-trapped, monkeying around with, say, alien nanotechnology could result in the lab and most of the surrounding terrain melting into grey goo.

As an analogy, imagine an 1850's Victorian Era scientist dismantling a live nuclear reactor trying to figure out how it works. Radioactivity hadn't been discovered yet, much less nuclear fission. So they would be at a loss trying to explain the disaster that happened after they removed all the nuclear damper rods for closer examination.

Karellen paused, and the silence grew even deeper.

"There has been some complaint, among the younger and more romantic elements of your population, because outer space has been closed to you. We had a purpose in doing this: we do not impose bans for the pleasure of it. But have you ever stopped to consider -- if you will excuse a slightly unflattering analogy -- what a man from your Stone Age would have felt, if he suddenly found himself in a modern city?"

"Surely," protested the Herald Tribune, "there is a fundamental difference. We are accustomed to Science. On your world there are doubtless many things which we might not understand -- but they wouldn't seem magic to us."

"Are you quite sure of that?" said Karellen, so softly that it was hard to hear his words. "Only a hundred years lies between the age of electricity and the age of steam, but what would a Victorian engineer have made of a television set or an electronic computer. And how long would he have lived if he started to investigate their workings? The gulf between two technologies can easily become so great that it is -- lethal."

From Childhood's End by Arthur C. Clarke (1953)

The legendary Gharlane of Eddore opined some precautions:

Since you're dealing with an unknown technology, and artifacts/lifeforms potentially engineered for purposes you're not aware of, you'd have to be REAL danged careful how you handled them. A special-purpose handling lab with a gigaton-nuke auto-destruct and remote-control handling gear would seem to be a minimal safe procedure, and you'd also have to dope out some way of picking up the pieces with no risk, and preferably no physical contact with your own ships and artifacts. Remote-control handling ships that scoop up parts, deliver them to the analysis lab, and then dive into the nearest sun, might be a good approach.

David G. Potter

In the TV show Babylon 5, there was a corporation called Interplanetary Expeditions or "IPX". It was dedicated to researching the ruins of advanced civilizations that are now extinct, in the quest to find new technologies that they can patent and profit from.

Plasma Weapons

Silly as they are, plasma weapons are a popular SF concept that just won't go away. They are encountered in such diverse places as the original Star Trek TV series, the Traveler role playing game, and the Babylon 5 TV series. They play the role of a futuristic flame-thrower.

Their main draw-back is that they won't work.

Plasma is the so-called "fourth state of matter", and is basically hot air. That is, it is a gas heated to temperatures comparable to the interior of a star or the center of a thermonuclear explosion so that all the atoms are ionized. Unfortunately, according to the virial theorem, the plasma wants to equalize its internal pressure with the external, i.e., it wants to expand into a diffuse cloud of nothing.

Dr. Rodolphe D'Inca is a physicist and researcher of fusion energy at the Max Planck Institute for Plasma Physics. He was kind enough to answer a few questions on the topic for me. Looking at the concept, it was his understanding that a plasma weapon is a gun that ejects a ball of plasma, a plasmoid, at high velocity to destroy the target through kinetic impact.

I asked him if the plasma would expand and dissipate its energy due to Coulomb repulsion, the same problem suffered by charged particle beams. Rodolphe explained:

Most plasmas are neutral: you have a Debye shielding where the cloud of electrons screen the effect of the ions: above a given length called the Debye length, the plasma can be considered neutral. So unlike a charged beam, the Coulomb repulsion doesn't play a role. That's why plasmas a relatively insensitive to electrical fields except for the boundary layer (which is of course of one Debye-length thick).

The Debye length is about 10-4 meters for a Tokamak fusion container (0.1 millimeters) down to about 10-11 meters for solar core plasma (0.01 nanometers). Which means if your plasmoid is larger than a speck of dust you do not have to worry about Coulomb repulsion.

I asked him about Ideal gas laws. Since the plasmoid was basically a hot gas in a vacuum, would it expand and dissipate its energy like, well, a hot gas in a vacuum. Rodolphe explained that yes indeed, due to the virial theorem a plasmoid with no external forces would expand at the Alfven velocity or the ion acoustic velocity due to internal plasma (fluid) and magnetic (electromagnetic) pressures. The Alfven velocity depends upon things like magnetic field strength and total mass density of the charged plasma particles, it is typically something like 500 km/s to 5000 km/s.. This means that after the plasmoid travels for one second, its diameter will be approximately five thousand kilometers, i.e., it has dissipated into nothing.

Well, you might ask, what about adding some external forces to prevent this? Sorry. If you use matter, you are basically trying to make an armored shell capable of containing a thermonuclear explosion in its interior, and having it somehow break apart when it hits its target. This is more or less impossible. And if it was somehow possible using some kind of Handwavium, there is nothing preventing your opponents from armoring their combat spacecraft with the exact same thing. It would be much simpler to just use a missile with a thermonuclear warhead.

And if you try to use energy, in the form of a magnetic field or something, you have the same problems. Plus the new problem of somehow making a self-sustaining magnetic ball powerful enough to contain a thermonuclear explosion.

Rodolphe did note that things were different if you were shooting plasmoids inside an atmosphere. In the lab next to his office they are trying to create ball-lightning (page is in German, use Google Translate).

Finally I asked him if the thermal glare from the hot, brightly energetic gas would interfere with tracking your target. Rodolphe explained:

Aiming at the target through a plasmoid shouldn't be too difficult: it will have an average thermal signature which can easily be discriminated from the target.

Dr. Rodolphe D'Inca

He went on to say:

Plasmoids are a very interesting topic and we see that the question of the plasma weapon is not as trivial as expected. I was thinking of two other examples relating plasmas and kinetic energy: the nozzle of the VASIMR engine where you have a magnetic detachment and conversion of plasma pressure into kinetic energy. And the laser-ablation propulsion where a plasma is created at the back of a capsule and, through its expansion, exerts a force on the capsule.

Dr. Rodolphe D'Inca

So there you have it.

For further analysis of the worthlessness of plasma weapons with a focus on Star Wars and Star Trek, I refer you to Stardestroyer.net.

And please note that the jet from a Casaba Howitzer, while it is a plasma, it is not a plasmoid. In any event, it is a very short-ranged weapon.

Tractor Beams

These more or less totally science fictional (if you disregard things like using microscopic laser beams as optical tweezers to move microbes around). Tractor Beams are like super-duper electromagnets, but much better. Electromagets can only attract ferrous objects, while tractor beams can both attract and repel objects made of any material. Electromagnets attraction strength falls off as 1/r4, while tractor beams tend to have absurdly long ranges (with the exception of the Geegee fields in Poul Anderson's TALES OF THE FLYING MOUNTAINS. They had a range of a few centimeters, so ships had to touch hulls in order to grapple each other).

Young readers may believe that tractor beams were invented by the writers of the original Star Trek (1966). Even younger readers may believe it made its first appearance in the movie Star Wars: A New Hope (1977). I've got news for you, the first example I found was the "Attractive Ray" featured in Edmund Hamilton's Crashing Suns, published in 1928!. "Attractor" and "Pressor" beams appear in E. E. "Doc" Smith's The Skylark of Space (1929). The term "tractor beam" appears to originate in E. E. "Doc" Smith's Spacehounds of IPC (1931). Attractor beams pull the target closer to your ship, while pressor beams push the target way. Pressors are also called "repulsors" or "repellors."

Newton's Laws

In any event, pretty much all of the depictions of tractor beams totally ignore the fact that they must obey Newton's Third Law (i.e., the law of action and reaction). There are only two exceptions I am aware of. One exception is in TOM SWIFT AND THE RACE TO THE MOON, where the intrepid teenage inventor Tom uses his repelatrons for the propulsion system of his amazing spacecraft Challenger. Another is in the wargame Vector 3. In that game, your ship can use tractor beams to impose x, y, and z acceleration vectors on the enemy ship. However, due to Newton, your ship receives the same vectors in the opposite direction (e.g., if you give the enemy a +4 z acceleration, your ship receives a -4 z acceleration). Note that this only works if the two ships are of equal mass.

Anyway, Newtons says that if the starship Enterprise uses a tractor beam to reel in a Klingon battle cruiser, the Enterprise will also move towards the Klingon. Both will move towards the point called the Barycenter of the two ship system. In the same way if the Enterprise pushes away the Klingon, the Enterprise will also be pushed away from the barycenter.

The acceleration each ship will experience towards or away from the barycenter depends upon each ship's mass. Simply put: if ship Alfa has twice the mass of ship Bravo, it will be accelerated half as fast as ship Bravo. If an Imperial Star Destroyer tractors the Tantive IV, it will be accelerated about 1/110th as fast as the Tauntive. And if the Death Star tractors the Millenium Falcon, its acceleration will be so tiny as to be difficult to detect.

The actual equation is from Newton's Second Law:

a = F / m

where:

  • a = ship's acceleration (m/sec)
  • F = tractor beam energy (Newtons)
  • m = ship's mass (kg)

If you want relative acceleration, use 1 for F and measure m in terms of the other ship's mass.

Example

If the ship in question has a mass of 3.5 times the mass of the other ship, it will experience an acceleration of 1 / 3.5 = 0.29 times as much as the other ship. If the ship has a mass of 1/4 times the mass of the other ship, it will experience an acceleration of 1 / (1/4) = 1 / 0.25 = 4 times as much as the other ship.

Calculating Movement

If you want to open up a real can of worms, you can try calculating what happens if the two ships are moving when the tractor beam is turned on. I am not going to try and calculate the minute to minute effects (because it is way above my pay grade) but the final results after the two ships come into contact can be approximated by the mathematics of a completely inelastic collision. This is the equivalent of figuring the trajectory of two balls of clay that collide and stick together. I will show the equations for figuring this in two dimensions, since I am unsure of my ability to expand it to three dimensions.

Given two spacecraft with masss of M1 and M2, velocities of V1 and V2, and vector directions angles of θ1 and θ2; when they are tractor beamed and drawn together into contact, calculate the combined ships velocity Vf and vector angle θf.

Step 1: Calculate each ship's x and y coordinate displacement
  • V1x = V1 * cos(θ1)
  • V1y = V1 * sin(θ1)
  • V2x = V2 * cos(θ2)
  • V2y = V2 * sin(θ2)
Step 2: Calculate each ship's momentum
  • O1 = V1 * M1
  • O2 = V2 * M2
Step 3: Calculate each ship's momentum in the x and y axes
  • O1x = O1 * cos(θ1)
  • O1y = O1 * sin(θ1)
  • O2x = O2 * cos(θ2)
  • O2y = O2 * sin(θ2)
Step 4: Calculate the combined ship's momentum in the x and y axes
  • Ofx = O1x + O2x
  • Ofy = O1y + O2y
Step 5: Calculate the combined ship's mass
  • Mf = M1 + M2
Step 6: Calculate the combined ship's momentum
  • Of = sqrt( Ofx2 * Ofy2 )
Step 7: Calculate combined ships velocity
  • Vf = Of / Mf
Step 8: Calculate combined ships vector angle
  • θf = arc tan( Ofx / Ofy )

In James White's novel Star Surgeon (1963) we find a weaponized version of the tractor-pressor beam, the so-called "Rattler." These weapons attract then repel the target at 80 gravities, several times a minute. When used on an entire ship, the hapless crewmembers are shaken like the dried beans in a baby's rattle. If focused down to just affect a small spot on the target's hull, the shear forces can rip the hull like it was wet cardboard. This was also used on C.C. MacApp's nearly forgotten and definitely underrated novel Recall Not Earth.

In the Exordium series by Sherwood Smith and Dave Trowbridge, "ruptors" fire unpolarized gravitons to shake their target to pieces. Polarize the gravitons, and you have a tractor beam.

In E. E. "Doc" Smith's Lensman series, tractor beams are used to anchor the inertialess target so it can be damaged by weapon beams. In response, the enemy developed "tractor beam shears", which were planes of energy capable of "cutting" a tractor beam. Of course if your ship had more tractor beam projector than the target had tractor shears, the target was out of luck.

Also in Doc Smith's Skylark series, the Osnomian hand guns are very silent, since bullets are propelled not with gunpowder, but by "force-field projection." So logically if one has tractor beams, one also has the equivalent of a railgun or coilgun. In MacApp's Recall Not Earth, tractor beams are used to launch torpedoes out of their tubes.

If you want some nice technobabble, attractor beam can be hand-waved as a sort of laser using gravitons instead of photons.

Medusa Weapons

This is totally utterly science fictional with no basis in reality, but it is too amusing not to mention. Remember the Greek myth about the Medusa? Anyone unfortunate enough to look at the Medusa was turned into stone, such was her extreme ugliness. The science fictional version is an image on a monitor or a sound over a headphone that can kill.

The general idea is a person suffering physical or mental damage merely by experiencing what should normally be a benign sensation.

The closest thing to this in the real world are the flashing lights that can trigger a seizure in a person suffering from photosensitive epilepsy. But that is not quite the same thing as a medusa weapon. You may have read about the Denno-Senshi Porygon episode of the TV show Pokémon, where the cartoon flashed the TV screen in such a manner that several viewers had seizures. Mention of such a seizure-inducing flash can be found in the novel and movie of The Andromeda Strain. In 2008 there was a photosensitive epilepsy attack on the on-line forum for the nonprofit Epilepsy Foundation.

Examples

Blit

In the story "Blit" and others by David Langford, some scientist, who should know better, invents a graphic pattern called a "basilisk" that will cause the viewer's brain to lock-up, killing the viewer instantly. It works much like a computer virus, crashing the brain's operatining system.

As the FAQ puts it:

...the human mind as a formal, deterministic computational system -- a system that, as predicted by a variant of Gödel's Theorem in mathematics, can be crashed by thoughts which the mind is physically or logically incapable of thinking. The Logical Imaging Technique presents such a thought in purely visual form as a basilisk image which our optic nerves can't help but accept. The result is disastrous, like a software stealth-virus smuggled into the brain.

David Langford
A Scenario

An atomic rocketship of the valiant Space Patrol fires a warning shot across the bow of the sinister black spaceship belonging to the dreaded Necroscientist of Titan. A signal for parlay is sent, and the foolish Patrol captain accepts a videophone message from the Necroscientist in order to discuss terms. Everybody on the bridge within eyeshot of the videophone monitor keels over dead with the Parrot burned into their visual cortex, as the Necroscientist makes good his escape.

The Cassini Division

In the novel by Ken MacLeod, one of the weapons is the so-called "Langford Visual Hack" (an obvious tip-of-the-hat to David Langford). As a defense, all computer monitors on the ship are designed to contain enough visual static to prevent the visual hack from working.

War Against The Rull

In the novel by A.E. van Vogt, the alien Rull can draw the "lines-that-could-seize-the-minds-of-men". Any human who looks at such a diagram is instantly hypnotized, and will just stand there in a trance.

The Black Cloud

In the novel by Fred Hoyle, a helpful intelligent interstellar nebula attempts to teach a human being its native language with remote controlled audio-visual equipment. This proved to be fatal the the person. The trouble is that humans know to be true too many things that actually are not true. They have to un-learn too much in order to learn the alien language, and the cognitive dissonance is fatal (it causes an inflammation of brain tissue).

Macroscope

In the novel by Piers Anthony scientists discover an alien interstellar broadcast that is sort of a galactic library. Unfortunately for the scientists, the broadcast is overlayed with the "Destroyer Sequence." This is a visual sequence that forces the brain to think certain thoughts it is not able to think, which burns out the brain leaving the hapless victim mentally a vegetable.

Kaleidoscope Century

In the novel by John Barnes, a rogue artificial intelligence can call a person up on a telephone, then use rapidly changing audio signals to reprogram the person's brain, turning them into a brainwashed zombie.

Battlefleet Mars

In the wargame by Redmond Simonsen, a top executive of the Ares corporation is assassinated by a sonic pulse over the telephone.

Nanotechnology

Nanotechnology (and it's extension nanorobotics) is the concept of molecule sized machine. The idea is attributed to Richard Feynman and it was popularized by K. Eric Drexler. It didn't take long before military researchers and science fiction writers started to speculate about weaponizing the stuff. A good science fiction novel on the subject is Wil McCarthy's Bloom.

There are many ways nanotechnology could do awful things to a military target. One of the first hypothetical applications of nanotechnology was in the manufacturing field. Molecular robots would break down chunks of various raw materials and assemble something (like, say, an aircraft), atom by atom. Naturally this could be dangerous if the nanobots landed on something besides raw materials (like, say, an enemy aircraft). However, since they are doing this atom by atom, it would take thousands of years for some nanobots to construct something (and the same thousands of years to deconstruct the source of raw materials).

But using nanobots for manufacturing suddenly becomes scary indeed if you make the little monsters into self-replicating machines (AKA a "Von Neumann universal constructor") in an attempt to reduce the thousands of years to something more reasonable. Suddenly you are facing the horror of wildfire plague spreading with the power of exponential growth. This could happen by accident, with a mutation in the nanobots causing them to devour everything in sight. Drexler called this the dreaded "gray goo" scenario. Or it could happen on purpose, weaponizing the nanobots.

Drexler is now of the opinion that nanobots for manufacturing can be done without risking gray goo. And Robert A. Freitas Jr. did some analysis that suggest that even if some nanotech started creating gray goo, it would be detectable early enough for countermeasures to deal with the problem.

What about nanobot gray goo weapons? Anthony Jackson thinks that free nanotech that operates on a time frame that's tactically relevant is in the realm of cinema, not science. And in any event, nanobots will likely be shattered by impacting the target at relative velocities higher than 3 km/s, which makes delivery very difficult. Rick Robinson is of the opinion that once you take into account the slow rate of gray goo production and the fragility of the nanobots, it would be more cost effective to just smash the target with an inert projectile. Jason Patten agrees that nanobots will be slow, due to the fact that they will not be very heat tolerant (a robot made out of only a few molecules will be shaken into bits by mild amounts of heat), and dissipating the heat energy of tearing down and rebuilding on the atomic level will be quite difficult if the heat is generated too fast.

Other weaponized applications of nanotechnology will probably be antipersonnel, not antispacecraft. They will probably take the form of incredibly deadly chemical weapons, or artificial diseases.

Some terminology: according to Chris Phoenix, "paste" is non-replicating nano-assemblers while "goo" is replicating nano-assemblers. Paste is safe, but is slow acting and limited to the number of nano-assemblers present. Goo is dangerous, but is fast acting and potentially unlimited in numbers.

"Gray or Grey goo" is accidentally created destructive nano-assemblers. "Red goo" is deliberately created destructive nano-assemblers. "Khaki goo" is military weaponized red goo. "Blue goo" is composed of "police" nanobots, it combats destructive type goos. "Green goo" is a type of red goo which controls human population growth, generally by sterilizing people. "LOR goo" (Lake Ocean River) nano-assemblers designed to remove pollution and harvest valuable elements from water, it could mutate into golden goo. "Golden goo" are out-of-control nanobots which were designed to extract gold from seawater but won't stop (the "Sorcerer's Apprentice" scenario). "Pink goo" is a humorous reference to human beings.

ACE Paste (Atmospheric Carbon Extractor) designed to absorb excess greenhouse gasses and covert them into diamonds or something useful. Garden Paste is a "utility fog" of various nanobots which helps your garden grow (manages soil density and composition for each plant type, controls insects, creates shade, store sunlight for overcast days, etc.) LOR paste: paste version of LOR goo. Medic Paste is a paste of nanobots that heals wounds, assists in diagnosis, and does medical telemetry to monitor the patient's health.

Hafnium Bomb

Consider an electron buzzing around an atomic nucleus. If it is as close as it can get to the nucleus (i.e., it is in the lowest unoccupied energy band structure) it is in its base energy state. This means it is "at rest", or at least as close as an electron gets to being at rest.

Anyway, if the electron absorbs some energy, from a photon or something, it can no longer occupy the base energy state. It has to rise to a higher energy state. In scientific terms, the electron has become "excited." This is not a stable situation, eventually the electron spits out the extra energy (generally in the form of a photon) and falls back into its base energy state.

Nuclear physicists immediately wondered if the protons and neutrons in the atomic nucleus could also become excited. As it turns out, indeed they could. When a nucleon becomes excited, the nucleus becomes a nuclear isomer.

Most nuclear isomers decay back into the base state in a fraction of a second. However, one or two can stay excited for years. Tantalum's isomer Ta-180m has a half-life of 1015 years, which is much longer than the age of the universe. But then there is Hafnium's isomer hafnium-178m2, which has a half-life of 31 years.

Storing Energy

By now you are thinking "So what?"

Well consider this. Excited electrons contain the energy of chemical reactions. For example: a stick of dynamite. Excited nucleons contain the energy of nuclear reactions. For example: a nuclear weapon. Not so boring now, are they?

So converting ordinary hafnium into hafnium-178m2 would be the equivalent of revving up a rechargeable battery with nuclear energy.

One gram of pure hafnium-178m2 (the same mass as a paperclip) contains about 1330 megajoules of energy. This is the equivalent of 317 kilograms of TNT, about the same as the warhead on a Tomahawk cruise missile (TLAM-C). Now you know why people started to talk about a "nuclear hand grenade." (as Alan Bellows puts it: "the most appealing aspect of isomer triggering was its potential to shoehorn yet more death and destruction into convenient 'fun size' packages")

There was also speculation about using hafnium-178m2 as a power source. A suggested application was a nuclear isomer powered airplane. The popular term was "quantum nucleonic reactor".

What was even better is the fact that the energy emerges not as visible light photons, not as ultraviolet photons, not even as x-ray photons. This stuff spits out freaking gamma rays! In other words, it just might be the key to constructing a gamma-ray laser.

The US military was also interested in the fact that hafnium-178m2 could be used to circumvent the Nuclear Non-Proliferation Treaty. Tremendous energy release, intense gamma rays, but it ain't a nuke.

The Problem

The trouble is that it is a worthless weapon if it takes thirty one years for half of the energy to slowly leak out. For a weapon you want it all to burst forth instantly. Therein lies the rub, nobody knew how.

That is where the controversy started.

Enter Dr. Carl B. Collins of the university of Texas. He figured that hafnium-178m2 could be triggered to release its energy by irradiating it with carefully tuned x-rays. The process is called induced gamma emission.

In January of 1999, Dr. Collins lead a team to explore this possibility. They put a tiny smear of hafnium-178m2 on the top of a styrofoam coffee cup, and used a scavenged dental x-ray machine to bombard the sample. After several weeks, the team studied the results. They concluded that there was a teeny-tiny increase in gamma rays measured in the data, which they interpreted as proof positive that they had succeeded. Or at least opened the possibility that there might be some magic frequency which would make the hafnium-178m2 create the desired explosion.

As always in science, if one has extraordinary claims, one had better have extraordinary evidence. And the sad fact of the matter is that Dr. Collins' evidence was pretty pathetic. Many scientists were uncomfortable with his outlandish claims and his experiment's large margin for error. Indeed, his findings were somewhat at odds with the laws of physics given that nuclei are thought to be practically unaffected by electromagnetic radiation.

The US military didn't want to provide funding to a crack-pot, but didn't want to miss out on nuclear hand grenades either. So they asked the Jason Defense Advisory Group (a panel established in 1960 to advise the government in matters of scientific controversy) to make an assessment. The Jasons concluded that the results fell into the former category: the data did not prove that induced gamma emission had occured, and even if it had a successful triggering event would not start the necessary chain reaction due to energy dissipation.

Meanwhile the Argonne National Laboratory used their own powerful x-ray machine in an attempt to reproduce Dr. Collins results. They failed: no induced gamma emission was recorded. Dr. Collins said it must be because your machine is too powerful. The skeptical Argonne scientists tried again using Dr. Collins' specifications. Still nothing was seen. Collins again ascribed the problem to experimental minutia, but by now the Argonne scientists had better things to do with their time.

Dr. Collins' work is more or less totally discounted nowadays, but there is a small group of true believers that still dreams of nuclear hand grenades.

Meson Accelerator

In the science fiction role-playing game Traveller, the most potent starship weapon of all is the dreaded Meson Accelerator (MA). Before MA technology is developed, warship designs have lots of armor to protect them from hostile missile, laser, and particle beam weapon fire. After MA, warship designs omit armor in favor of more weapons, because armor is utterly worthless against MA fire. There is also a tendency to make lots of small warships instead a few large ones, in the pious hope this will prolong the life of your fleet. Or at least prolong it longer than the life of the enemy fleet.

As with all powerful Traveller starship weapons, MA are typically installed as a "spinal mount". MA are also marvelous as a planetary defense weapon. You can put MAs several kilometers below the planetary surface and still shoot at hostile orbiting spacecraft. The spacecraft will not be able to shoot through several kilometers of solid rock (unless they too are armed with MAs).

Later a star nation can develop the technology for the meson screen, which renders MA powerless (much like Kryptonite's all-or-nothing effect on Superman). Then warship design goes back to normal, except all designs must include a meson screen.

Why are meson accelerators so deadly? Because their method of action is so sneaky.


Some background. Nuclear physicists love to play with atom-smashers, particle accelerators, cyclotrons, and the like. These create subatomic particles (i.e., the component particles that atoms are made out of) and make them move really really fast in beam form. Yes, if you weaponize this, you have a particle beam weapon. Anyway, some kinds of particles are unstable, they have a short life-span. After a few nanoseconds they decay into other particles, radiation, or both.

Einstein's relativity, besides forbidding faster-than-light starships, also says that at speeds close to that of light, time will slow down. At about 90% the speed of light (0.9 c), the slowdown is about 2 (called the "gamma factor"). So if a particle has a life-span of 10 nanoseconds when sitting still (relative to you), when the particle is travelling at 0.9 c (relative to you) you will time it as having a life span of 20 nanoseconds or twice what it should be. At 0.95 c the life span will be 30 nanoseconds, at 0.98 c it will be 50 nanoseconds, and so on (see table here). This is yet another bit of weirdness from the screwy world of Einstein's relativity. Thanks, Albert.

Now in physics 101, you'll learn that distance equals rate time time. Our particle moving at 0.9 c has a rate of 269,813,212 meters per second. It has a time (life-span) of 20 nanoseconds or 0.00000002 seconds. Multiplying will show you that the particle will move a distance of about 5.396 meters before it decays. At 0.95 c, it will move 8.544 meters. At 0.98 c it will move 14.690 meters.

Your eyes are probably glazing over by now. The point is by altering the speed of the particle you alter the point in space where it decays.


So how do we weaponize this? Say we have a particle that easily passes through most matter in general (and starship armor in particular) but will eventually decay into a spray of deadly radiation. You aim your particle accelerator at the enemy starship, calculate the range between the accelerator and the enemy, then adjust the speed of the particles such that the point where they decay into deadly radiation is inside the center of the enemy starship. It is like teleporting a burst of radiation into the enemy ship's guts.

Now you see why the meson accelerator is so deadly.

Why the "meson" in "meson accelerator"? Because the people who wrote the Traveller RPG figured that the particle called the neutral pi-meson (pions) would work. They have a mean lifetime of 0.000000084 nanoseconds, and decay into a splendidly nasty spray of gamma rays, electrons and antimatter electrons.


Unfortunately, the meson accelerator shares the same problem with plasma weapons: they won't work. Anthony Jackson points out:

  • Pions are stopped by armor (because they are affected by the strong nuclear force)
  • Pions do not have a life span of exactly 0.000000084 nanoseconds. That is the half life. This means along the entire beam pions are decaying, by the time you reach 0.000000084 nanoseconds half of the pions in the beam have decayed. So there is not a pin-point dot where the pions decay, it is a gradual decay along the whole beam.
  • If you can accelerate pions to such high velocities that the "decay point" is in a ship several million meters away, the particles will have so much energy that you don't have to use pions. At that energy, a beam of garden variety electrons will instantly vaporize any armor that is made out of matter. The gamma factor will be about 1016. This means every single one of the zillions of subatomic pions will have a blast energy of 2.16 × 105 joules. That's right, each single subatomic particle will have the energy of an antipersonnel land mine.

In defense of the authors of Traveller, much of this nuclear science had not been discovered at the time Traveller was written. Later version of the Traveller game try to retcon this by saying the meson accelerator was invented by George Meson, and it actually works by some hand-waving way, and has nothing to do with pions at all.

To amplify what Antony said:

Pions interact via the nuclear forces. A beam of pions traveling through a material will have a chance of hitting an atomic nucleus. A nucleus has an effective cross sectional "size" of about 1 × 10-30 m2 for high energy particles. A cubic meter of solid or liquid matter with atoms spaced about 0.1 nm apart (a typical atomic spacing) will contain 1 × 1030 nuclei. The total combined cross sectional "area" for the beam to interact with is thus about 1 × 10-30 m2/nucleus * 1 × 1030 nuclei = 1 m2 — the same cross sectional area as our cubic meter of matter. Thus, a beam of particles interacting only via nuclear forces can expect to hit a nucleus after going through about 1 meter of solid or liquid matter (or about 1000 meters of gas at atmospheric density, since gas is about 1000 times less dense). Note that this distance is not affected by relativistic time dilation — there are just as many nuclei in your path no matter how fast you go.

When a pion hits a nucleus at these energies, the nucleus will either have a chip knocked off — a proton, neutron, alpha particle, deuteron, or triton — or shatter into fragments. These nuclear pieces will have considerable energy of their own, hit other nuclei, cause more fragmentation, and so on, while those pieces that are charged will also lose energy to ionization. The pion may or may not be captured when it interacts. If it is not captured, it keeps going (although with less energy) and can knock into more nuclei.

Note that these nuclear interactions are not tunable to some precise distance — they occur throughout the path of the beam as pions and fragments encounter nuclei.

Also, the time to decay is random. A pion might live on average 8.6 × 10-17 seconds in its own rest frame, but this means that half of your pions will have decayed before 8.6 × 10-17 seconds is up, and half are still around. After 17.2 × 10-17 seconds, you still have one quarter of your original number of pions still waiting around to decay, and one-eighth of the pions after 25.8 × 10-17 seconds. If you turn these into a beam of relativistic particles to delay their decay time, you still get them decaying at random all along their beam path, not at one specific point.

Now there is one possible retro-fit justification to this conundrum. At the time Traveler was written, particle physics was still figuring out a lot of the stuff we know about today. Today, meson means a particle composed of a quark and an anti-quark, but back then a meson was a particle with a mass significantly more than an electron but significantly less than a proton or neutron. One of the "mesons" was the "mu-meson," which we now categorize as a sort of heavy electron and not a meson at all. Muons, as they are now called, do not interact via the strong nuclear force but they are charged. Charged particles lose energy at a well defined rate as they go through matter (depending on the particle's charge and speed, the density of the matter, and some details on the chemical and electronic properties of the matter like how hard it is to knock electrons off). Since all the particles in the beam are losing energy at the same rate, they all have nearly the same energy at any point along the beam as they go through matter. In particular, this means they all come to a stop at more or less the same point. If it is a muon, it will decay after it stops into a highly energetic electron plus a couple of neutrinos. The highly energetic electron will dump all its energy into the surrounding material very rapidly. Meanwhile, muons themselves are extremely penetrating — muons from cosmic rays have been known to penetrate not only the entire atmosphere but over a kilometer of rock. By tuning the energy of a beam of muons, and with a good estimate of how thick your target is and a rough idea of its density and composition, you can choose an energy so that all the muons come to a stop in the middle of the target due to ionization losses and then dump a lot of energy there with their decays. You can only do this because muons do not interact via the strong nuclear force, so they do not hit nuclei like mesons or neutrons or protons would — this makes muons far more penetrating.

Alas, muons have a lifetime of about 2 microseconds. If you are tuning the energy to choose how deeply into the target the muons decay, you can't boost the muons up to ultra-relativistic energies to give them enough time dilation to reach distant targets (that would give them so much energy that they would seriously overpenetrate). With a maximum time dilation of maybe 10 for practical purposes, this gives a muon gun a maximum range of around 6 km — less for thinner targets that need lower energy muons if you want the beam to stop in the middle (more precisely, you will have lost half your muons at 6 km with a time dilation of 10 — the beam still goes on a bit further with diminished intensity, but after a few multiples of 6 km, the beam will have been attenuated so much that it will not do anything significant).

Luke Campbell