Space Combat

Space Combat by Trevor Calder

23 September 1996

Having seen a couple of articles touching on space combat (specifically ship to ship) I thought it might be time for me to put my $0.02:-)

First, it's important to understand what it isn't. It isn't air to air combat, or even submarine combat. It has elements of both, but is so different that knowing about either of those two won't help much. Both air to air and underwater combat have an element of height (or depth) in them, but planes and submarines have limits which they can't exceed. So it isn't true 3D, but 2D+.

Combat, anywhere, boils down to 2 things - staying alive, and stopping the enemy doing what you don't want them to. For the first you need 2 things. A way of stopping the enemy finding you, and a way of stopping them hurting you. In space, not being found means not being found electronically. At the distances combat would occur, the Mk 1 eyeball isn't very useful. So ignore any scene in any show where ships are within sight of each other. So how do you do it? Anti-radar technology, with radar absorbent materials, angular surfaces (to reflect radar away from the sender). And also the more esoteric stuff like thermal masking (to fool infra-red), or even anti-laser tech. Lasers wouldn't be very useful weapons but may well find a role as detection devices (Hmmm....I'm getting some of my own laser light reflected back at me. Must be something there...)

Of course, if the enemy do find you, you will need ECM to jam their detection systems temporarily. Temporarily? Sure. If they can lock on for an instant, you'll be dead. But, since locking onto you will also give away their position, they'll be dead too.A good way to see in the dark is with a flashlight. But this also means everyone else can see you. It's the same principle with radar, or other detection systems.

So, despite your best efforts, the enemy knows where you are, and fires the only effective space weapon I can conceive of. It's on its way, you can't hide, run away, or dodge. A modern air to air missile travels about 10 miles in 15 seconds. I wouldn't expect space missiles to be slower. You sit and hope (trying to run or dodge maybe) that the EMP shielding will work.

Because when that nuke blows, you'll need every piece of it.

Weapons will be nuclear projectiles - fired at targets up to about 50 miles away. Not with the object of atomising the enemy ship, but of crippling the control mechanisms via the EMP produced. (For those that don't know, EMP = electromagnetic pulse. It fries electronic systems.) Which also means the weapons will be high yield - 50 Mtons or more. Not designed to explode on impact, or via proximity fuse, but at a specific point as close as possible to where your target is, was, or might be. You don't know where the enemy is, but where they were. You could allow for possible course changes etc. but it comes down to a guess. So you need as big an EMP as possible, in case they're not where you guessed, but a few miles away.

So you're out there, you've found the enemy (via a remote sensor system, maybe), and lobbed a nuke tipped rock at them. It goes BOOM nicely, and you've scored a kill. Cost to your side - one expensive nuke. Cost to their side - one cheap ship, or maybe one expensive ship, or (more likely) one very cheap decoy.

So how do you win? By sending lots and lots of decoys, lots of cheap computer controlled ships, numbers of cheap manned (personned, or whatever the PC term is) ships, and a very, very few large expensive ships with big crews and huge numbers of nukes to bomb planetary targets.

How do you stop the enemy winning? By searching out the decoys, computer controlled ships and the small manned ships, and then blowing the crap out of the big, expensive ships. Not that you can ignore the others - after all, even a decoy ship can hold a nuke. For those that don't know, you can fit a nuclear weapon into a briefcase. A really big one (one of 50Mton yield) would need a freezer sized box. So you'll need a huge number of small 'fighters' to take care of the other side's small 'fighters'. And a few large, well armed, well defended ships to take out the enemy 'capital' ships.

And so, finally, the B5 tie-in. Where there are battles with lots of small fighters, and a few big battleships.

Except they don't use nukes, but very inefficient beam weapons. But, in the interests of looking better on TV, I forgive them:-)

Space Combat by Thorfinn

29 September 1996

Space combat is 3 dimensional in fundamentally different ways to either aerial combat or submarine warfare. Aerial combat is 3 dimensional, but is *extremely* concerned with aerobatics and gravity related effects. Submarine warfare is *generally* anti-surface ship warfare, which is nothing like space combat at all. In both cases, you have both an operational ceiling and an operational floor.

In space warfare, you're much more concerned with relative velocities, and the *changing* of your relative velocity with relation to your enemy. You can happily turn off your main engines, rotate your ship, then fire up the main engines again in the direction you wanted to go.

It seems to me that tactical operations for space battles (Note: tactics = how you use what units you've got in battle, strategy = decisions involving what sort of things to put into what battle, how to get them there, what that does to your various battlefronts, etc) are rather similar to standard 2 dimensional tactical warfare, but translated into 3 dimensions. This gives the following incomplete table, for examples.

---------------------------------
phalanx      square      cube
tortoise     circle      sphere
wedge        triangle    cone
line         line        sheet
---------------------------------

In B5, there appears to be directly canonical evidence for a few points. No 'shield' technology. This means advanced materials technology is used to protect ships of all kinds. Lasers do not appear to be used, presumably because of power generation problems. Plasma weapons appear to dissipate with range, hence are close range fire weapons. Anti missile systems appear to be highly effective. Jump points take energy to generate, and appear to be easily detectable at range *prior* to formation. Jump point generators take time to re-generate.

Also postulated, is that there is some sort FTL-technology based detection system, that is better than radar type systems at detecting the location of masses in the area (whether they're enemy or friendly or whatever).

Given all of this, it seems that a few battle tactical and strategic points become logically clear:

There are two basic types of fighter (really small) craft. Anti-large craft fighters (call them Type A - equivalent to WWII torpedo/dive bombers), and anti-small craft fighters (call them Type B - equivalent to WWII fighter craft).

Type A fighters are 'necessary', because torpedoes (missiles) launched at a distance will likely be destroyed by anti-missile systems. Hence, one needs to get reasonably close before firing a missile that'll be effective.

Type B fighters are necessary for two reasons, one being that you have to shoot down any Type A fighters in the vicinity, and fighters are probably better at shooting them down than the defence grid is, and the other being that you want to shoot down as many Type B fighters around as you can, 'cos they're bad for your Type A fighters. :)

A bunch of properly escorted (by Type B) Type A fighters should be able to happily take out most other shiptypes at a materials/resource (pilot cost included) cost of much less than the losses involved.

Hence, you don't want to bother building light and medium sized craft (no cruisers, destroyers etc), because they are too small to provide effective support. However, you *do* want to build *large* ships, capable of carrying a few hundred fighters, that are jump-point generation capable, and that carry some pretty heavy weapons.

Space battles then would consist of firing up those jump-point generators, jumping into the target enemy system at a reasonably high relative velocity, then launching all your fighters and starting to fire your weapons as soon as you turn up in system.

You want to spread your forces out, *probably* into a 'cone' of ships, which you then use to happily charge through the enemy, firing all weapons as you go through. :)

Energies, Speeds and Detection of Weapons and Crafts
by Jeremy Lee

7 October 1996

This is the first of two posts. In this one I'll look at finding some numbers we can bandy about in any future calculations.

My biggest interest is in the trade-offs between beam, projectile, and missile weapons. In order to do this, we need a starting point of the kind of energies involved.

WARNING: What follows is extreme technobabble, although all is provable from standard textbook physics and sources that I have accumulated. I assume little in the way of future tech.

Let's postulate a few things for our theoretical beam weapon.

First, energy availability and power plant size:

Looking at the parameters of shot 80539 of the Tokamak Fusion Test Reactor, we see they generated 10.7MW of power in 0.21 of a second. This gives a possible sustained output of 50.95MW/s.The PPPL predicts that an operating reactor will produce 1000-3000MW of power. (1.21 gigawatts? Hmmm.) Take a midrange on that and we have a reactor output of 2000MW.

Let's assume that 50% of that is available for weapon use, and that we have an 90% efficiency rate at transferring that. (An ion beam would be the best bet. We could probably tap plasma straight out of the fusion core and channel that into a beam, but we will assume losses along the way). We have 900MW/s of power left in our energy beam.

A tokamak reactor of this size will probably weigh about 1000 tonnes.

Second, craft sizes and speeds.

Starfuries look to be about 10 tonnes of craft. It seems to be 5 times bigger than a car, and they weigh a tonne each and are mostly empty.

A capital ship will weigh somewhere in the order of 20,000 to 200,000 tonnes, depending on size. Let's take a midrange and call it 60,000t.

A missile? Make it half the size of a starfury, 5t.

Starfuries have accelerations of up to 8G (what human pilots can stand) and capital ships are likely to have half that. We'll be generous and give missile 20G acceleration rates.

NOTE: Jet fighter planes get their 'G-Forces' from turning manoeuvres, not from their engines. There is no atmosphere in space, thus the high G's that planes get for 'free' in their turns does not apply in space. Every G of acceleration has to be earned.

How much energy does each of these craft take to accelerate at 1 G? From F=ma we deduce Missile: 50KW Starfury: 100KW Capital Ship: 600MW

Using one decent sized fusion reactor, a Capital ship can probably maintain a 4-5G burn indefinitely. However, unless they can build fusion engines less than a tonne in weight, starfuries and missiles are going to be rather shortchanged. So, let's make our first MAJOR assumption : We can build a 'micro-fusion reactor', that weighs only 1t. Scaling down the tokamak, this gives a 50KW reactor. Let's assume another half a tonne of materials to build a mythical 'Plasma Storage' tank, which lets us burst that 50KW. The tokamak gets power densities in the range of 2MW per m^3 in the plasma core, so let's give the plasma storage tank a 1 cubic metre capacity. Thus, we have 2MW of power on burst standby for the engines, and/or guns in the case of the 'fury.

That means, the Starfury can do 0.5G continuous burn, or a 8G burn for 2.6 seconds before depleting the tank. It then needs to idle for 40 seconds to refill the tank.

The missile fares little better. It can sustain a constant 1G burn with the same reactor/tank configuration, and can do it's maximum of 20G for only 2.08 seconds.

Let's be generous to the 'fury and give it an increased tank. Make it 2 litres. That scales all our figures up to that it can do an 8G burn for 5.3 seconds, giving it double the ability to manoeuvre.

In terms of fuel, E=mc^2 says that the rector chews up only 2X10^-8 grams of material an hour in direct mass->energy. A plasma engine of advanced design can probably expel material at Mach 10. This means that 16g of fuel will be expended a second. Given 1t of fuel, the engines can run at peak rate for 17 hours. (This would be unusual, however)

One last important calculation: a missile, having expended it's entire fuel compliment on acceleration in a straight line, can be travelling at 9,216Km/s. (or, 33.1 million KPH, over 3% of light speed)

Now: Detection instruments.

We already have instruments that can detect, using gravity alone, the movement of a human fist at a few (call it three) metres. We also have the ability to boost that measurement 10,000 times using another existing (but probably incompatible) technology. [The gravity instrument detects micron-sized movements in a wire. Tunnelling probes in STM microscopes detect atomic features nanometres in size. This is 10,000 times smaller]

This means, using near-existing tech, we can detect a capital ship at 3.28Mkm, a Starfury at 13,400km, and a missile at 3,000km. I think it's fair to extrapolate the future tech such that we can crank that up the sensitivity of our instruments by 100, giving a x10 increase to those ranges. Making it:

Capital ship: 32 million km Starfury: 134,000km Missile: 30,000km.

For a future in which we can build 1t fusion reactors.

Note that this is detecting essentially an idle mass through gravitation alone. If the spacecraft actually has it's engines firing, then it's going to be much, MUCH more detectable. The exhaust emitted by our theoretical plasma engine above will be at a temperature of 3 Million degrees Kelvin.

I don't know enough about plasma radiation to say how visible this will be. At a rough guess, if the plasma were putting out 1% of it's energy in infrared light, That's about 10^22 photons a second. CCD's can detect individual photons, so assume a 10cm radius telescope, and a need to get one photon a second to allow for proper detection. This means that the plasma exhaust of a missile or starfury would be visible at 42,000 million kilometres. Or, 2 light minutes. To put that in perspective, we can still receive signal from Voyager, which is transmitting on an 8 watt radio, even though it's well over a light hour away.

In the example above, an array of 100 or so individual detectors would probably be used to correlate photons and identify 'near' sources of IR radiation. Of course, as the missile got progressively closer, the ease of resolving it will increase to the third power of it's reducing distance.

In other words, with its engine burning, a missile is 140 million times more detectable than using gravity alone.

Beam Weapons by Jeremy Lee

7 October 1996

On beam Weapons - My SF imagination comes up with a few different types, listed below. Your choice as to what the various races are using. I personally think the line-up goes:

Earth: Laser/Ion
Narn: Laser/Ion
Centauri: Ion (Cannon, not beam)
Minbari: Antiparticle/Interaction
Vorlon: I don't think we've seen their real weapon yet.
Shadows: Interaction/Quark.

Lasers
Method: A medium is 'Pumped' with energy, creating a coherent light beam. When focused on a target, it will heat/vaporize material at that site.
Advantages: easy to produce, tight collimation giving a long, stable beam. Speed of light giving minimal interception time. Large range of available light frequencies make it an unpredictable weapon.
Disadvantages: Can be reflected/deflected, low energy transfer, relatively poor energy efficiency.
Defence: Cover your ship with mirrors.

Ion particle beams
Method: Use a particle accelerator to speed up heavy ions to a sizeable fraction of the speed of light, and then hurl them a target. The resultant energy transfer will (a) heat/vaporise the target site, and (b) cause lots of nasty radiation which will fry those inside.
Advantages: VERY energy efficient. Higher transfer rate than lasers.
Disadvantages: Uses depletable 'fuel' for the beam, beams will disperse from mutual repulsion between particles.
Defence: A powerful magnetic field can deflect the beam

Neutron beam
Method: Same as Ion beam, but with neutron
Advantages: Cannot be deflected with magnetic field, does not disperse.
Disadvantages: MUCH harder to generate and control, since you can't bend or accelerate a neutron with electric fields. (you would need to use gravity)
Defence: None known.

Antiparticle beam
Method: Same as Ion beam, but using antiparticles. This changes the impact result from a relatively straightforward kinetic energy transfer to a particle/antiparticle annihilation, releasing a LOT more energy. The target site would actually explode, rather than heat/vaporize.
Advantages: Immensely greater energy transfer for beam size. Energy transfer is not dependant on beam speed.
Disadvantages: Antimatter is hard to generate. Dispersion is similar to Ion beam. If you're close enough, you could get fried by the radiation.
Defence: Same as for Ion beam.

All of the above are thoroughly understood, and we could build them today with enough funding. The next one is a weapon type that is possible, from what we understand of physics, but is a thousand years away in technical ability.

'Interaction' beams
Method: Streams of 'force carrying' leptons or bosuns. They would begin affecting the way which matter worked, causing spontaneous decomposition. For example, a stream of W+ bosuns would affect the weak force, causing relatively stable atoms to break up as in ordinary atomic decay.
Advantages: Unstoppable by a lesser technology. Would probably affect the entire cross-section of a target at once, rather than just the surface. No dispersion if the right particles are chosen.
Disadvantages: Low interaction rates means you need to generate a lot of particles.
Defence: None known.

The next set are pure imagination, and are impossible from what _we_ know of physics.

Free Quark beam
Method: Create a beam of free quarks. Don't know how. A free quark would probably combine with a proton/neutron to produce two Leptons. The atom would self destruct as the nucleus lost it's charge. Unimaginable energy would be released from the quark interaction, making the Antiparticle beam look like a match.
Advantages: ?
Disadvantages: Opposite problem from Ion beams: The beam would tend to self-combine.
Defence: Don't be there.

Graviton Beams
Method: Create a beam of gravitons. Such a beam would do weird and bad things to matter, probably ripping it apart.
Advantages: Speed of light. Good collimation.
Disadvantages: ?
Defence: Stay at home.

Tachyon beam
Method: ?
Advantages: Faster than speed of light - a distant target cannot dodge, and you can point the beam at where they appear to be now, as the beam goes back in time.
Disadvantages: Paradoxes cause destruction of the universe? If you miss, you could end up hitting yourself last week.
Defence: Don't get born.

Focusing of Beam Weapons

8 October 1996

Russell Coker wrote:
If the beam stays focused it could keep going. However it would be impossible to make a laser which has perfect focus (as it is impossible to do anything perfectly) even if this was desirable. So after some reasonable distance the beam would be diffuse enough that it wouldn't cause any damage.

NB  When designing a laser weapon it might be desirable to control the focus, eg if you wanted to attack an enemy from both sides then you could setup the lasers so that they wouldn't be focussed enough to cause friendly-fire problems. Or have a focus control on the laser which would allow the beam to be focused on a point at the estimated distance of the enemy. That way if one of your guys flys in front of you or if the beam over-shoots the good guys won't sustain a lot of damage.