Atomic Rockets

Introduction

If you want to get an intuitive feel for how interplanetary combat is likely to be, there are a few simulation games that can help. Otherwise, read on:

For supplementary information, please read Rick Robinson's Rocketpunk Manifesto. Specifically:

What Will It Be Like?

What's its going to be when space combat finally arrives?

Is it going to be like WWI aircraft? That is, rickety ships with a few crude weapons bolted on as afterthoughts, flown by a few aces who are familiar with the eccentricities of their craft? (Imagine a Space 1999 Eagle Transporter as a futuristic "Sopwith Camel") Or will it be more sophisticated?

Watching the evolution of space warships will be interesting as well. In the movie THE ENEMY BELOW (the movie that the ST:TOS episode "Balance of Terror" was based on) the German U-Boat commander was reminiscing. He said that in WWI, when you submerged in a U-Boat, you were never quite sure that the cantankerous submarine would surface again. The captain would eyeball the target through the periscope with no gauges, do some arithmetic in his head, and order the torpedo fired verbally. If you were lucky, it would make it out of the tube.

But now, the captain moans, it is all mechanized. He looks through the periscope with cross-hairs, which relays the settings to the plotting table and the automatic firing calculator. The captain thinks it is terrible that they've taken the men out of war.

So in the future one can imagine a Belter pilot, crying over her beer-bulb at Ceres Bar. She'll bend your ear about the good-old-days during the Asteroid War of Independence, figuring vectors and delta-vs by the seat of your pants, early mornings on the Cosmodrome with your leather jacket and anti-nuke goggles, flying for Duquesne's Flying Circus.

Nowadays, she'll complain that pilots just zip up into the acceleration tank and let the computer fight the ship. They've taken the men out of war...

Try to imagine what would it be like on the deck of an escort class interplanetary craft, shepherding a convoy of logistic hulls and on the lookout for convoy raiders. The signals officer will be alert on his ladar scope, trying to burn through the stealth of the wolf packs.

But then there is scientific reality to consider. Unfortunately, it seems that the more accurate you make it, the less interesting it becomes. Having said that, keep in mind that much of the following is speculative and controversial. If you don't like it, ignore it. Just try to be self-consistent and work out the ramifications of anything you postulate. Go to The Tough Guide to the Known Galaxy and read the entries "SPACE WARFARE" and "WARFARE"

Details, Details...

And SF authors should use Heinlein's technique of adding an odd detail or two in order to remind the reader that this is taking place in the future (his favorite example: "The door dilated"). For instance, World War I aircraft pilots wore silk scarves, everybody who enjoys Snoopy knows that. What most people don't know is the reason behind the scarves. The early rotary engines would spew a steady mist of castor oil lubricant into the pilot's faces. The scarves were a handy towel for the pilot to clean their goggles, and to keep the castor oil from running down their neck.

SF authors are advised to do their own thinking about the day-to-day life of their star pilots, and attempt to identify odd practical habits that would turn into identifying hallmarks. In his Known Space novels, Larry Niven's asteroid miners have a habit of not making hand gestures when they talk. In the cramped control cabins a gesture might accidentally hit a switch, with dire results.

Master Artist Rhys Taylor is working on some images of hypothetical but scientifically accurate Orion drive warships battling it out around the Jovian moon Callisto.

The Targeting Problem

Frank Chadwick of Game Designer's Workshop created a starship combat game called Star Cruiser. In his analysis, developments in tactical combat can largely be viewed as attempts at better solutions to the targeting problem. That is, the trouble is not with the destructive potential of the weapons, they are quite potent enough. The trouble is getting the weapons to reliably hit the target.

This can be done two ways: increase the precision of each shot (precision of fire), or keep the same precision but increase the number of shots fired (volume of fire). Obviously it is preferable to increase the precision of fire. For starters a volume fire version of a weapon will generally be much larger than a precision fire version.

There are three main elements to precision of fire:

Enemy positionThe location of the enemy when your shot arrives.
Weapon performanceThe actual flight path of your shot as affected by the physical characteristics of the weapon itself and the environment through which the shot passes.
Weapon controlThe degree to which you can precisely control the aiming of the weapon.

Note that you can trade precision for increased range, that is, if you can increase the precision of your weapons, you can chose to target a hostile spacecraft at a greater range at the old precision.

Naturally your target is going to be trying to decrease your chance of hitting. They will be trying to decrease your precision of fire and decrease your effective volume of fire.

Precision of fire is decreased by interfering with the three factors listed above (obviously). The easiest is their position, by evasive maneuvers, by interfering with your targeting sensors, and by reducing their target signature.

Volume of fire is decreased by rendering harmless shots that actually hit. This is done by armor, point defense, and science-fictional force fields.

Cherrypicking for Effect

Much of the details the space combat for your science fiction novel or game are driven by the initial assumptions. So if the author desires to write about a certain style of interplanetary warfare, they can cherry-pick the initial assumptions to allow that style.

For example: if your initial assumptions include incredibly powerful lasers and incredibly precise aiming technology, you going to have a problem if the desired warfare style includes a pitched battle between spacecraft of the Lunar Revolutionary Navy and the Terran Royal Fleet occurring halfway between Terra and Luna. The two fleets will be shooting their opponents to pieces while in orbit around their respective worlds. If they try to fly to your desired battleground at midway point, the battle will be effectively over long before any of the surviving ships reach it.

When Ken Burnside was creating his starship combat game Attack Vector: Tactical (AV:T) he cherry-picked the laser ranges in order to allow the warships to maneuver. If the range is too huge, maneuver is pointless. In the following quote, it is interesting to see the various implications and trade offs.

One AV:T armor point is approximately 35 mm RHA. One AV:T damage point is ~50 Mega-Joules (MJ) delivered to a spot size of 8 cm square. Most AV:T lasers have conversion efficiencies of 20% to about 5%, with efficiencies dropping as wavelengths decrease. The waste heat in a laser is dissipated/transferred at about 600 MJ/game-segment; when the waste heat is dissipated, the laser can fire again. Flash coolers allow you to expend coolant to do this faster, heat exchangers do this faster, but without expending a limited resource.

AV:T lasers were cherrypicked to make interesting game ranges; a 200 nm laser table does exist for AV:T, but weapons that are that long ranged tend to minimize the tactical decisions of maneuver, which wasn't the game I wanted to write.

One AV:T energy point is one GJ in a superconducting adductor. AV:T batteries range in generation from 1st (1 Giga-Joule per battery) to 6th (6 GJ per battery) with the most common being 2nd generation batteries.

One AV:T defensive damage point is roughly 4.167 MJ, or about a kilo of TNT in round numbers.

I don't worry about dwell time for the lasers, because it happens in time frames of less than one segment, which is my atomic unit of time in the game.

Some things you can change to make a radically different setting:

  1. Lengthen laser ranges (by shorter wavelengths). AV:T lasers start in the near infrared.
  2. Improve laser cycle times by improving their conversion efficiencies — if you could make a laser with about 40-50% conversion efficiency, you'd have one that would operate continuously for around 2-5 points of damage per segment for as long as you could power it. Hook it to a dedicated reactor system, and you get a very different feel.
  3. Improve the efficiency of the missile propulsion systems; this one gets tricky and works better for a novel series than a game. AV:T missiles have Isp in the low 300s and are conventional solid fuel rockets; this is done for maintenance reasons. You want something that can be stored and handled with the minimum of hazards for an oops. Hypergolics, cryogenic fuels and nuclear fuels all increase the hazards of routine operations, and in my universe, that outweighs their performance benefit; it may not in yours. (I generally try to keep in mind that the majority of the missile techs you'll meet are 19-20 year old kids who joined the Navy because their grades or finances wouldn't take them to college. Klutz and "E1-proofing" are at a premium.)

The better question about your ships is this:

Who's paying for them, and why?

Naval architecture can be seen as a tax on shipping; the total naval budget will be seen as some percentage of the total monetary value of the commerce they're protecting.

Who are they protecting it from?

This sort of question is one of the thorniest ones in making a space travel setting. In order to determine the size of a navy, you need to determine launch costs, shipping costs and shipping volumes of a pair of blue jeans from point A to point B.


We've done this for Ten Worlds, and it sorta kinda works...but Ten Worlds, with 10 planets and a carefully undefined number of systems with can cities (orbital habitats), has a total population of ~67 million as of 2267.

Even then, there are things carefully not mentioned in the background (heavily automated factories and the like) to keep industrial civilization running; we deliberately set up the planets for economic specialization, and there are STILL things that nobody makes that people just do without.

For comparisons on your ranges:

Gunboats = 625 to roughly 1250 tonnes. Dedicated rider craft. The (somewhat blurry) categorization between "Gunboat" and "System Defense Corvette" is "Does it generate its own onboard power?"

Corvettes = 2250 to about 3250 tonnes. 2500 tonnes or below, they're usually dedicated rider craft.

Frigates = Roughly 4750 to 5500 tonnes. This is usually the smallest range of ship that is fully FTL capable with substantial cruise endurance. In many ways, the parlance of frigates is that they're the smallest (and thus, cheapest) ship that can be sent independantly somewhere to do something useful. Naval treaties and general force projections refer to "frigate equivilants".

Light Cruiser = 6750 to about 8300 tonnes. This, at the lower range, is a "super frigate" — something that does a frigate mission, but with better armor and bigger guns, possibly at the cost of maximum thrust. At the higher end, there's a definite opportunity cost in terms of maximum thrust, but it's usually made up for with increased endurance, increased armor, and increased firepower. At least until it has to dodge incoming kinetics...

Heavy Cruisers = 8750 to 10500 tons. It's possible to make a light cruiser that has comparable thrust rates to a frigate — past about 8500 tons or so, you can't do that, and that's the usual demarcation point for a heavy cruiser. These tend to have facilities for command and control, and firepower that's meant to kill frigates in short order. The problem is you can't have them everywhere, they're expensive to build and expensive to maintain.

Within this size range, we have missions. Common nomenclature is that a frigate designed to work within a battlegroup is called a destroyer. One optimized for longer independant patrol missions is called a frigate or patrol frigate. Corvettes can be FTL capable, but most are limited FTL, and some are lugged around by freighters to guard important systems.

Doctrinally, some nations put freighter style cargo pod attachment points on their ships to extend cruising range by adding fuel or cargo or both; these get dropped off before you enter the fight. Some also put gunboat docking ports on (which are fairly similar, all things told) Some don't like the idea that dropping a cargo pod means that the enemy COULD make a spoiler attack by killing it when you're retreating. Some nations eschew offensive gunboats, because the life expectancy of a gunboat crew is fairly short. Others do it because it's the best way to get an overwhelming throw weight of missiles on a target. Still others do a mix and match approach...

Freighters don't carry weapons; they can replace a "life support rated" pod with a gunboat or two. This is used by pirates to conduct piracy; it's also used by ships worried about piracy to defend themselves...and sometimes it's rather difficult to tell the difference between the two. (This also has the benefit that a gunboat crew is small enough to make an interesting Role-Playing-Game party...)

In AV:T, there's an attribute for a drive called "Generation", which is a measure of drive efficiency. Lower generation drives have less fuel efficiency than higher generation ones; there is another attribute called "Maximum Drive Output" — for the same MDO, a lower efficiency drive will generate more thrust, but require a larger fraction of the ship's mass be fuel to get the same total delta V.

From thread in sfconsim-l forum (5/14/2006)

Miscellaneous Notes

"Vesta acquisition."

In response to the verbal from the autopilot, Dieter Ulans flipped his datavisor in front of his eyes and prepared to take direct command of the massive ring of lasers and reaction engines that was Hercules. He hit the juicer button and felt the rush as the drugs began to wash into his veins. "Com'monn jockey juice!" he whispered and then began to croon: "All my thoughts of you, you, you -- all that I've sought is you, you, you." The tiny green symbols on the datavisor began to zip past his eyes at an increasing speed.

His subconscious easily absorbed and processed the information even as his conscious mind took in the blue numbers and symbols on the main screen that showed the gross situation as Hercules and five other ships of the Martian battlefleet began their final approach to Vesta Main Station. "Joey Kolnichok, I know you're here and I'm going to personally fry your tender little parts." The ship thrummed as the main three o'clock engine cut in and changed vector in response to a movement of Dieter Ulan's right ring finger. It was his former classmate he sought -- Josip V. Kolnichok - the one who had beaten him out his bid for a cushy transport command and who had also cast aspersions on his loyalty to the company. This had cost Ulans two points on his profit sharing plan and that was a deficit he intended to make up by turning J.V. Kolnichok and the Des Jardin into a bright, glowing gas.

"80-80. Ready track. Ready main. On my mark FC to you and...mark!"

A second green line began streaming across the datavisor as Ulans took control of the main laser fire control systems. Every time he blinked, the little green symbols paused. Every time he squinted his eyelids, a bright blue bullseye magically appeared where he looked on the main screen. Just tap your foot when your buddy shows, he thought, and you'll make him a star. He began to click his teeth together. His finger tips sweated in the close-fitting control caps. Only eighteen k-k's from Vesta and still no Company. What had they done -- written the station off? The entire ship reached into his heightened awareness. The awesome engines designed to hurl inert cargo on multi-million-kilometer tracks through space. The heavy mining laser converted into a terrifying main weapon now slung in the cargo grapples. The thousands of bits of information from the ship's computers and sensing radars. Where the hell were they? "Come on, you Company fish, swim out into the pan."

Violently the ship executed a maximum burn maneuver with her nine and twelve o'clock engines. Some of the datastream elements were now glowing red. "Damage report: two mike hit on plates 1023/24 negative critical. Integrity 80-80."

"Beautiful, Dee, You saved our jewels with that cut."

Ulans tapped his foot reflexively. On the blue cross hair showing on the main screen, a yellow dot bloomed. Six thousand kilometers distant, several people died.

"Gotum! Gotum!" Jacklin screamed in the interphone. "You're writin' the book, Dee baby! Writin' the book!"

What would you know about books Jacklin, thought Dieter -- besides which I do not feel well and have not the faintest idea of what I'm doing. The rest of the crew was shouting over the phones, estatic with victory. Bystanders he thought. Goddamned passengers. Me -- I'm doing it and I don't know it until I've done it.

"17 to main power...16" Jacklin began to recite the seconds remaining until the main laser had built itself a new charge. No sound, mused Ulans, no bang. They should put sound effects on these things so that you could hear a bang when you made a shot. The slight vibration and the glow on the screen wasn't enough. No real way to relate to that. Should be some noise.

Once again, the crew was slammed by heavy G-force as the ship responded to the almost automatic commands of Ulans' fingers. A loud whanging started up in some distant part of the Hercules. He could actually feel the deck rippling under his feet. Not so lucky this time.

"Damage report. Nine mike frontal hit on super B. Partial dislocation on six o'clock. Six isolated. Explosive decom in cell four, five, six, and F-2. Randalls and Chung do not respond. Losing power on three o'clock and associated vanes. Looks bad, Dee."

"What's happening with the rest of the task force?"

"They're 180 on the other side of Vesta doing a job on the remaining Company element. We're being tracked by a triple-A Company police ship -- most likely the transport Des Jardin."

"Can we run for it, Dee?"

Ulans looked through the datavisor at the blue figures on the main screen even though he already knew the answer.

"No chance. We've got maybe one shot as Kolnichok closes. Maybe I'll get fancy and burn him off. At worst, we'll wind up in the Company Can -- after all they don't want to blow up this ship -- they think they own it!" he lied. He knew he was going to die, but the rest of the crew was even more helpless than he so why burden them with reality?

Three little orange dots appeared on the screen. Look at him -- blowing out decoys even though he knows we're out of maneuver -- that Kolnichok, grinned Dieter. So which one is you, Joey, and which are the aluminum balloons? (Seven dots grew on the screen, all had slightly different vectors.) Now you know my heater can take you in one flash and you also know that one zap is all I'm going to get. And if I take it you've got a perfect excuse to blow me up for the honor of the company rather than recapture valuable property for the accountants. So what's it going to be? I think you shot off too many balloons too early Joey -- cause the other ones aren't making the course correction you just did. Ain't that you, Joe?

Ulans squinted and tapped his foot.

From the introduction to the wargame BATTLEFLEET MARS by Redmond Simonsen

Once, when man first took to the air, the waiting was short, the combat long. The biplanes and tri-planes, with turning circles half the length of Polar Star, could stay in contact till fuel ran out, with never more than five minutes between firing runs.

Then came World War II, and combat sprawling over countries and states while speeds lunged toward a thousand kilometers per hour and time between action doubled, tripled as the pilots, fighting to turn their planes around, swept miles beyond the field of battle before inertia could be bucked enough for return.

And then man broke the sound barrier. The MacDonald Phantom closing on the Mig, radar contact at sixty miles, the pilot inactive, his plane fighting for him as minutes drag, then contact, a shock of missiles, a blaze of fire, and he's fighting the rudder and ailerons, trying to make it around one hundred and eighty degrees of a turn before sliding into Chinese airspace a hundred miles away. A fistful of seconds for an armload of time.

And then into space. Forty minutes' wait while we watch those two fluorescent blue blotches converging across a quarter of the sky, our computers tracking, our nerves tensing, waiting for the five-second explosion, the reflexive punch at the missile control, and then empty sky ahead again, the enemy fading five hundred kilometers back and losing fast, your forward thrusters blazing to slow you down, to allow you to turn at a dead stop, to overcome inertia and rebuild the G-force to send you screaming back to the fray, the time between contact ten, twenty incredible minutes.

And every moment of waiting, while the heat of battle subsides around you, gives you time to think of the dangers you are in, of the dangers just survived, of the dangers you are plunging toward once again. For just a minute between battles, on less! For something to keep the mind a blank till it's needed to handle the stick! But it can't be done, and for ten minutes, twenty minutes, forty minutes, eyes riveted to the screens, you stagger beneath your load of fear. This is where battles are lost and won; this is where our battle was being fought, as the distance between us and the Tars narrowed and the minutes made their slow way by.

From Common Denominator by David Lewis (1972)