Space Combat Techniques Discussion

[Urwumpe]

I really hate to be so cruel sometimes but you obviously never thought about such terrible mundane things like accuracy. In a perfect world, everything is easy. A spacecraft is easily visible because nothing obstructs the emissions. And a rectangular pulse remains one regardless what happens.

In the real world, everything is only as easy as you can fulfill the demands it has in terms of accuracy. It isn't that hard to understand. if you want to drill a few holes into the wall to screw your network stuff to it, even being a few mm off the marks means you have ruined the wall for nothing.

Radar pulses don't reflect back from a target as nice rectangular pulses, but as a sum of multiple smaller echos. I have a radar photo here, that shows a French satellite, taken with a 30m antenna, while the satellite is illuminated by a 110m antenna a few hundred kilometer away from the receiver (bistatic radar). You can imagine the shape, but the actual image is a sum of many basketball sized pings. And the intensity of the pings does not tell you anything about the spacecraft except, that this part was especially good reflector for the radar waves used.

Stealth in space is very hard to even think of accomplishing. Way I see it is stealth materials, and holding in the heat. But that means the ship becomes a time bomb, heating up until the crew can take it no more. So, stealth is right outta there. Lasers would be used at long "range" because of their superior accuracy to kinetic weaponry. Hubble is an old telescope, likely better cameras will be used capable of identifying weaponry and point defense.

What is stealth? Stealth is not about not being seen at all, but about making it as hard as possible to be seen. A stealth fighter is still pretty visible and too loud to be overheard, but it won't appear on radar until it is too late.

It is just the modern form of camouflage. If you would paint a ship ocean blue and paint tiny waves on it, it would stick out of the ocean visually and shout "hit me" at you. make it in different shades of gray, and it becomes harder to spot it, especially if you are in hurry.

Stealth in space isn't different. Of course you can't hide. But you can pretend to be a harmless plush bunny. Or, at least an unknown pulsar. Or reflections. or sensor glitches. And if you have enough stuff around you radiating electro-magnetics, you can still pretend to be not there, or just not more important than other things in the cloud of spacecraft.

Essentially, to tell point defense apart from weapons, if its pointed at the missiles, its point defense. If its pointed at YOU, its a weapon. Lasers will damage those while the missiles close in, and kinetic weaponry is of course last because its the least accurate. Even with the fanning of lasers, they're still more accurate than a kinetic weapon at those ranges.

Again, think about accuracy once more: How can you tell that something is NOT pointed at you?

Just as example: If you hear a shot nearby, how much time does it take if you to tell where the shot came from and that this shot was not going into your direction?

Of course, that you still ask that question, would mean that the shot was not going in your direction, did it? Sure?

In Sci-Fi series, it is always easy, the sensors easily spot that weapons are getting armed and a female computer voice tells you that the shot came from behind. In reality, no such thing exists and will never exist. Simply because of accuracy. There are limits to it. And you can't push accuracy beyond hard-coded limits of the universe.

For example, you need a larger aperture of optical telescopes for resolving finer details. Three 10m mirrors can maybe resolve the direction of a spot of visual light within 0.01 seconds of arc by interferometry, but what does that mean in combat? One light-second away, the smallest object you can see is 14 m large - as long as it is much brighter as the background.

All you can see from that distance is a blur. and now imagine telling what happens inside this blur. The only way to tell that a weapon is not pointing at you, is that you still exist when you ask that question. otherwise, you are either dead or the weapon to weak to become anything prominent in the radiation signature of the object.

 

[ZombiezuRFER]

Okay, elaborate on how you think the typical sequence of events in space combat would go. Sorry if that sounded flamey.

 

[Eagle1Division]

Okay, thread's a bit old, but I was doing a search and it really got my attention... I read the little don't Necropost message and with good conscious said that I was adding relevant information....

Space Combat is a huge interest of mine, and I'd love to have some say in the combat mod being developed, so here's my thoughts on it...

First: lasers.
I think heat would play a huge part in space combat, and I want to divide laser range into "near" and "far"...
The "near" range of a laser would be the distance where you're focused enough that it will vaporize a layer of the enemy hull and cause an explosive decompression, shockwaves, and general explosive mayhem on your target.

Then there's "far" range. At far range, you don't vaporize anything, but you add heat to the enemy ship. This is still combat-effective. Essentially, you hit them again and again with the laser until they're heated to a point that they can't radiate it as quickly as you're heating them. At that point, they put that heat into heat sinks, and once those are full they're forced to start shutting down critical systems, and are out of the fight, at which point they surrender or die.

Then, there's out of range... There is a solid barrier where it's not effective to fire any more. That's when your target is so far away, they receive a small fraction of the heat your laser fires at them. When you're heated up more by waste heat from the laser than they are by being hit, you're out of range. As soon as you're imparting more thermal energy on them then you're getting from firing the laser, you're in range.

This is for a long-range interplanetary scenario, since those are really the scales that "far" will be more significant.

Now, when it comes to shooting down missiles, the only effective thing to do (mostly because they have such a small cross-section and no need to stay cool enough to keep people alive inside) is to fire at "near" ranges.

And might I say, the most effective thing missiles might ever do in long-range combat is make the enemy fire lasers and heat themselves up. A good laser needs only a few seconds to shoot down a missile. How many seconds does it take for a chemical rocket (or any other kind of rocket) to reach a target at long range?
And I seriously doubt there would be any difficulty at all detecting a missile. Rocket-missiles (since missile could also mean any projectile, I mean a rocket-powered missile...) would be firing their main engines, shining nice and bright for any even partially decent IR sensor to see.
Any non-rocket powered missile, I.E. railgun round, guass round, bullet, would not have nearly enough accuracy to even be a concern at thousands, or even hundreds of KM, just from things like imperfect reaction mass burn rates for a bullet (Gunpowder is reaction mass), imperfect strength and location of EM fields, etc. etc. Even microvibrations caused by the momentum imparted on the weapon from firing (err... Recoil! That's it!) would make un-guided weapons useless at any practical range. And anything that IS guided will have to use engines which will be easily detectable. If they're cold gass or small enough to not be detected, they'll undoubtably be far too weak to adjust the projectiles' course enough to hit the target.

That's not to say there won't be missiles. They're extra mass, sure, but when your enemy fires his weapons and produces heat, that's as good as hitting him with a laser at long range. Maybe the missiles have a nuclear-powered laser and don't even need to get close.
(Imagine, a nuclear explosion in the warhead. A telescope focuses all the thermal radiation on the enemy ship, in the thousandth of a milisecond before it's vaporized by the warhead.)

Another type of warhead that I like was mentioned way earlier. It's a hollow cone, nuclear warhead inside, with some flaK-like fragments on the open end of the cone. Although the cone is vaporized, for a few moments before then all of the nuclear explosion is focused out that cone, blasting the fragments at the enemy vessel in a narrow cone. I think he called it a "nuclear claymore" (sorry I was too lazy to look back and find your name )

The counter argument some people mentioned was that radiation would be better. Well, I respectfully disagree. If I have claymore nukes and you have radiation, you may hit me, but I'm still in the fight for hours or days. If you're hit with a claymore nuke, you're out of action the second it goes off and turns your ship to swiss cheese, or even worse, damages your radiators and the heat transfer systems, damaging your ability to cool off, and thus destroying your ability to use any of your weapons other than missiles.

Look up Neutron bombs, there's a reason they were never pursued, and that's that radiation doesn't really work well as a weapon. If you're going to pound them with radiation, it's just as easy to hit them with any other weapon which is far more sure to take them out instantly, and doesn't have a chance to turn them into berserkers (There's a sweet-spot in flash radiation exposure where you're certain to die in a number of days, and you know it, but you're perfectly fine until then. Psychological effect: Take every risk, making them far, far more combat-effective psychologically), or even something that has a high chance of taking a very long time to kill them (in an astro-spaceship firefight, hours is a very long time).

Now, what if you had heat storage that you could eject? Say, like a heat sink, except when it's full you just flush it into space to get rid of the heat instead of the slow process of using your radiators.

Taking this another step, why not intergrate this with the heat sinks? Heat sinks to allow you to keep going even when radiators are at full capacity, and when the heat sink is full you could just vent the plasma into space to get rid of all the heat at once, if you must keep producing heat.


Now, on another page, someone mentioned from military experience how things travel down the chain of battlefields (air, land, etc.). In my interplanetary warfare scenario, one planet is at war with another. The first step in any conflict is to take that highest part of the chain and work it down. First, an analogy to modern warfare. Since it's two planets, I'll play this scenario as two continents at war.

1. First, get air superiority. Once you have that, it's safe to move in with naval assets, 'cause they wont get hit from the sky.

2. Once you have naval assets, and have neutralized the enemy naval assets with air support, you can move in with your ground vehicles, since you're capable of transporting them there.

3. Once you have ground vehicles, you can neutralize enemy ground vehicles with air support. With enemy ground vehicles KO'd, you can move in with infantry without them getting mowed down.

4. Once you have infantry on the ground, and have neutralized enemy infantry with assitance from vehicular ground assets, you are now in control of your enemy.

Now, the actual planetary warfare scenario:

1. Get control of interplanetary space. This means neutralizing the enemies' ability to interfere with your transport operations, i.e., get rid of their space fleet so they can't attack your transports as they land. This is analogous to the Battle of Britain trying to gain Air Supremacy before Operation Sea Lion could advance.

2. Gain safe access to enemy LEO. You can't get shot up just “off-shore” of the enemy. This means neutralizing ground-based defenses, ASAT missile sites, laser installations, etc. This could be done from a higher orbit with a specialized high-powered weapon. Perhaps an IR laser or MAC gun. Any particle cannon uses a gas, which would lose a lot of energy in the atmosphere. Atmospheres also reflect +90% of UV light, so UV lasers are out.

(A note here, Submarines may have a major role in this. Since their position is uknown, they could deploy a missile pod, and, like mines, stay completely undetected until the enemy transport fleet arrives. Then they fire ASATs or single-shot lasers to disable the transports' ability to re-enter atmospheres. (Single-shot lasers would be a laser that operates at a temperature far higher than a regular one. Example: Nuclear laser missile mentioned earlier.) Because they're platforms detached from the submarine, the submarine is able to continue fighting despite any retaliation that could follow.)

3. Create an orbital Anti-Air network. Your ground forces will get clobbered by cruise-missiles or laser-carrying aircraft if you don't have this. A network of platforms in high orbit with IR lasers to shoot down anything the enemy puts in the air.

4. Wage a ground war and win. Once you've done this with support from high above, you control your enemy and victory is yours.


Now, Stealth: Possible, IMO. The idea of redirecting your heat in one direction works. Why not take it to the logical extreme? My idea is to take all of your heat into a heat sink, and like a fusion reactor keep it from melting your craft by keeping it off the walls with magnets. This turns it into a super-effective radiator because it's so hot it's radiating very intensely.
You encase it in a chamber of mirrors, and direct all the radiation into a narrow beam, very similar to a laser.
As a whole, this cooling system is incredibly complicated, risky to use, and far less effective than relatively simple cooling systems, BUT, the chances of an enemy vessel, or even a sensor probe, even if they'd launched thousands, crossing the path of your beam would be astronomically low. There are 148,510,660 square arcminutes in a full sphere. Restrict the beam to even less (but make it more intense to compensate) and you decrease your chances of being detected by the square.
I really don't care how many sensor probes you can launch. You can't launch enough. It would be significantly easier to find a single nuclear submarine SOMEWHERE in the North OR South Atlantic using a helicopter with a MAD sensor only (assuming the MAD has 1 full square kilometer of search area.). And you can't refuel, either. The flight time of your helicopter with the MAD is an analogy for the time it takes for the stealth spacecraft to complete it's mission. You don't have forever to find it. After all, it's going to be detected when it fires it's weapons, but then it will be too late.

As for firing the engines, this could simply be done when in LEO from behind the planet, out of view of any telescopes or other sensors.
Do it in a very low orbit to keep ground-based spies from spotting it with backyard telescopes.
To keep the hull from heating you use a re-usable booster, separate the booster once you're done accelerating and you don't even have to use your complicated radiator to get rid of the waste heat from the engines.

Because of the complexity of the mission and design of a stealth spacecraft, it would not make sense as your main fleet vessel, instead, it would be the equivalent of a Sea Wolf attack submarine. Very expensive and complicated compared to surface vessels, but pays for every penny if you get a free kill on a key enemy asset, even if you lose the sub in the process.


More to come, certainly. Sorry if I'm a bit hard to follow at times, some of these ideas I either forgot and remembered as I wrote, or came up with on the fly. (Like using submarines for a last-ditch defense, for instance.)

A lot of the ideas are somewhat far-fetched, I realized. But more or less they seem pretty solid to me, though they do depend somewhat on advances in technology. Which, if you're fighting an interplanetary war, you undoubtably have...
(My first post and probably one of the longest ones I'll do :lol: )

Maybe my next big post will be the Arsenal of war for this interplanetary scenario. Mars V.S. Earth, Martians versus Earthlings (All human), in a war for independence from the Interplanetary Fleet (Did I really put a smiley for war? Ah heck, it space war, it's too cool to not smile at, even if it is war. Plus, it's not like people are actually dying, it's not real... yet.)

 

[Sky Captain]

A problem with chemical drive missiles is they are very delta v limited, likely ~10 km/s will be the limit for tyipical missile unless you accept your missiles being huge 4 - 5 stage beasts. A futuristic space warship likely would have some sort of high thrust high ISP nuclear drive with hundreds of km/s delta v that is very expensive and don't scale down well so it would be relatively easy to avoid such delta v limited missiles, especially if they are fired from light seconds away. Maybe if missiles are cold launched with big coilgun and they stealthy drift toward the enemy and fire their engines only for final few hundred km high acceleration speed burst toward the enemy vessel then a chance of hit would appear. But that would work only if enemy vessels don't change the course too much while missiles drift unpowered.
A standoff bomb pumped laser warhead would massively increase the chances of kill because the missile could avoid crossing the most lethal point defense range.

 

[T.Neo]

Building a bomb-pumped laser would be... difficult, I'd imagine... possible, yes. Maybe some sort of directed blast weapon would be better? We know the idea exists, but a weaponised version is still classified. Spooky stuff.

Do lasers disperse with the inverse-square law? I thought laser photons were 'collimated' or something, and that they disperse at a different rate... but they still disperse.

I would also vouch for cold-launching a projectile. The amount of mass needed for large missiles would probably be quite prohibitive, a spacecraft with a large complement of them would be extremely large.

Still, you also have problems actually propelling an object... the whole system has to feed that energy into the projectile. Such a projectile might not be that large though... the smaller the projectile the easier it would be to propel, obviously a nuke and its associated guidance system, would be more mass than a simple KKV, but obviously far more effective.

I am weary of the '100s of km/s' drive. Remember that there are three definitions of 'speed' in space:

1. Acceleration.
2. Transit velocity.
3. Overall dV capacity- which can also be regarded as 'range'.

A combat spacecraft needs high levels of all three. Problem is, 2 and 3 don't go along very well with 1. Maybe if you have some sort of super-delicate, super-expensive ship... you can pull it off.

Another option is some sort of bimodal propulsion, or an engine that can have its ISP 'throttled' at the expense of thrust, like VASIMR. This has the best of two worlds, but unfortunately not both together.

 

[Eagle1Division]

A combat spacecraft needs high levels of all three. Problem is, 2 and 3 don't go along very well with 1. Maybe if you have some sort of super-delicate, super-expensive ship... you can pull it off.

Another thought is personally I don't think armor or the ability to take blows belongs in space combat, so being delicate wouldn't matter.
The reasoning is this: Everything on a spaceship is vital. You don't add anything that isn't, because of tight mass restrictions. Any armor system would cost a huge amount of Delta-Vee, and that means you don't control the battlefield.
(Higher Dv is perhaps one of the most important things to have. This is why Aircraft are at the top of the battlefield today - they are so much faster than anything else. If you're faster, you decide when to engage, where to engage, and on who's terms, as well as the ability to run away (though in space combat you'd need about twice the enemies' Dv to run away, not likely.) Heck, with increased mobility, you can even sidestep enemy forces that are less mobile - That's what the Germans did to the French defensive line in WWII.)
And even the idea of the ice shield - that's your reaction mass! If that gets chopped into pieces, shattered, destroyed, etc. then you're drifting helplessly. Armor that can't get destroyed doesn't really help much...

So, the idea would be to go all offensive. About the only defensive measure you should probably take would be a whipple shield - it serves a second purpose of acting like a shadow shield from the enemies' laser blasts. If they have a longer effective range than you do, then you can use the shield to hide behind until you're in range. It'll also act like a large radiating surface, for a third useful purpose.
Other than that, the only sturdiness or survivability a spacecraft would need is a PDS to avoid being hit, and a large armament to keep the enemy from shooting.

Hmm, now that I think about it, that's lot like aircraft combat today. Aircraft rely on offense rather than defense, if you're hit, you're out of the fight. They're just too lightweight to carry armor and be aircraft.
Spacecraft will be too lightweight to carry armor and be spacecraft.

As for fuel, if it's far enough in the future I would say Antimatter. (When they discover some much more effective breeding technique is at the roll of dice, no way to really know...) It's heck to store, meaning very expensive fuel tanks, but they're more than worth it for what's by far the most potent fuel.
Sure, if they penetrate your tanks you're dead; but that's true with any fuel. The engagement will almost surely happen before you do a capture burn around the enemy homeworld, so if you lose your reaction mass, you'll drift off forever and chances are military ships will be the only ones that can pull a Brachistochrone, so my guess is no civilian ships will have enough Dv to go pick you up.
Well, to be fair, though, a tank full of Deuterium could be compartmentalized (Which my design by nature is...), and you'd probably be saving a lot of Delta-V for maneuvering anyways. But there's a counterargument for that, too. Anything that rips a hole in your tank is probably going to do much more than just that.

Cold-launching is an interesting idea... Dunno if it'd work, though. A lot of heat is produced even with just using magnets - waste heat. And dropping a missile's temperature to have the thermal signature of empty space after launching through a coilgun would be quiet an engineering challenge. Not impossible, but would it be cost effective?

And I still think carrying missiles would be cost-effective. Keep in mind you could plan the ship to have fired them before doing the capture Delta-V burn, so it would only effect the mass ratio needed for the initial Dv burn. And I say they'd be cost effective because they both distract enemy lasers, cause the enemy to put waste heat on themselves, and have a chance of damaging the enemy directly, kinetically or by adding heat.

Now that I think of it again... Deuterium fuel (Fusion drive) sounds better and better, while it may not offer the Brachistochrone flight paths and insane Delta-Vee of an antimatter drive, it's safer, it doesn't take power to contain it, and aside from that - if you're doing really bad in a thermal firefight and your heat sinks are full - you can vent them and re-fill the heat sinks with gas from your fuel tank - so your heat sink is up and running again within a minute of being vented. It costs a small amount of Delta-V, but like I said earlier, you should be saving some anyways for maneuvering and for this purpose.

Do lasers disperse with the inverse-square law? I thought laser photons were 'collimated' or something, and that they disperse at a different rate... but they still disperse.

I've done some amount of work just going to post this, and here's what I've found...
For heating:
Fraction of beam heat on target (if apparent diameter of target is smaller than angle of beam divergence.)
= At/Ab
At = Area of target in Line-of-sight of the beam. I.e. along the axis of the beam.
Ab = Area of the beam
"At" would have to be done by a computer since it relies on a 3-d shape (a new mesh for modellers to make!).
Ab = (d * Sin(Theta))^2 * pi
Theta is 1/2 the angle of beam divergence (making the radius of the circle, angle in-between middle and outer edge of beam.)
d is, of course, distance.
If the apparent diameter of the target is larger than the diameter of the beam's circle, the area outside the radius of the beam will have to be subtracted, of course...
E / Ab = intensity, where E is the energy in the beam and Ab is the area of the beam.
Sin(Theta)^2 is a constant, since Theta (1/2 divergence) is fixed with the design of the laser. Let's call this number "D" (big D) for divergence, distance is little d.
E/Ab
Substitute Ab = (d * Sin(Theta))^2 * pi
= E / ((d * Sin(Theta))^2 * pi)
= E / (d^2 * D * pi)
Pi and D are constants, so they can be expressed as a single term. I'll call them multiplier K,
E / (d^2 * K) = intensity
Hmm. That looks like a sort of the inverse-square law, doesn't it? that was neat.

What I wrote about "(if apparent diameter of target is smaller than angle of beam divergence.)" gets me thinking - at some point it might actually be beneficial to increase divergence of the beam if the target has an apparent diameter larger than the beam divergence, so the max possible target area is "under the spotlight". It'll lower intensity, so you wouldn't do it if you're in near range, but depending on the shape of the target might actually increase heat on target for far-range attacks.
For a beam with changing divergence, you'll need to calculate a new K for every time you change divergence.
K = Sin(Theta)^2 * pi

Is this impressive enough to get me into the design team for the combat mod WIP? :lol:

 

[T.Neo]

The whole 'lightweight' thing isn't about making ships into battleships, it's about just... making ships. Already the same rule can apply to civillian passenger liners. Once your ship becomes filled with all sorts of fancy, advanced, top-of-the-line technology to a large enough extent, it can become technologically, logistically, and economically prohibitive.

Essentially: When your engine components are designed to barely operate, at 2000 C, and your propellant tanks are made of fractically folded tinfoil... then things are too shaky.

I would like to point out that armor on a spacecraft does not have to be heavy and robust. [ame="http://en.wikipedia.org/wiki/Whipple_shield"]Whipple shields[/ame] are already in use on many spacecraft, to defend against micrometeoroids and orbital debris. And you could potentially devise a sort of whipple shield against lasers and nukes as well.

The idea with the ice shield, is that it is a large amount of armor, and a large amount of propellant... so even if you have a relatively large amount of the shield blasted away, you still have considerable dV left. The other advantage is that even if your ship can't get home right away, at least you still have a ship- the ice shield is the simple, less expensive bit... but the engines, the cryogenic tanks, the weapons systems, the crew, the guidance... that is all still intact infrastructure.

The problem is that the ice shield I had, would equate to such a heavy spacecraft that it'd need petawatt-strong thrusters. Maybe I went somewhere wrong there and I can correct, though.

Antimatter for the propulsion of combat spacecraft is a really bad idea. Antimatter should be reserved only for very high velocity interstellar spacecraft, or in low amounts in lower-velocity spacecraft, for initiating fission and/or fusion (such as in the ICAN-II concept).

If your propellant tank is filled with LH2... and it fails... you can have catastrophic damage. If your propellant tank is filled with antimatter, then your ship disappears in a blindling flash.

Since antimatter isn't found anywhere in any large amounts (in nearby space, anyway), you have to make it. Disregarding the huge problems with making large amounts of antimatter, you need a huge amount of power to make the stuff. And you will never get efficiency of over 50%, because of baryon conservation, or something (which means that a particle has to be created for every antiparticle). With a 50% efficient antimatter producer magic-thing, you have to have something like 70 gigawatts of power input. Considering that you want many kilograms of antimatter, in fact, you want many tons of antimatter, this power consumption goes up and up. And a real antimatter production facility will be far less efficient than this. One can imagine how attractive a target such an object would be.

A 1000 ton spacecraft with a dV of 1000 km/s would need only around 5 tons of antimatter propellant, but still... that is darn frackin' antimatter! We've only made... paultry amounts up till now.

And if you want to do high thrust, by the time you get to using antimatter, your exhaust velocity is so high, that your thrust power will be absolutely enormous. For a 10 meganewton thruster, 500 terawatts thrust power. To put that into context, that is more than 30 times the total power consumption of the human race today. That isn't the real problem, though... the real problem is dealing with the waste heat. And it is even worse when this waste energy is all in gamma radiation.

A fusion engine would probably use hydrogen as reaction mass, with deuterium/helium 3/whatever as fusion fuel; i.e. energy storage. Use only the fusion fuel and direct the plasma products, and you'll likely get pretty good ISP... but lousy thrust.

A fusion drive can also do brachistochrones, but such a high performance drive has the issues discussed above... though perhaps in a less severe form. A brachistochrone, is pretty darn difficult to do.

I would not discount fast civillian ships, since passengers want to get where they want to go as fast as possible. Maybe they will not be as fast as military ships, or have as high acceleration, or they will dedicate most of their dV to their transit velocity, but they could still be pretty fast.

Deuterium is probably the easiest fusion fuel to get hold of (and indeed, probably the easiest fuel in general, considering places like the Moon only have low concentrations of uranium, etc), but D-D fusion produces neutron radiation, which can harm your crew, your ship, and also lose some of your energy. D-He3 is aneutronic, but there are still some neutrons from the side reactions. He3 is He3 though. Maybe elsewhere- such as on the Moon- it would be relatively easy to get hold of, though.

We shouldn't bother with stealth in space- i.e. trying to make oneself invisible, or to 'blend in' with the supercold background radiation of space. The best thing to do is camoflage yourself to look like something nondescript- such as an asteroidal or cometary fragment. Or even try to lose yourself against the face of a planet, for example. For example if you are only a blur on enemy sensors, you may only need paint that reflects the spectral qualities of an asteroid, to be ignored.

Even a good distance from the Sun, the sunlight you reflect would probably make you stick out like a sore thumb. If you decide to go dark and absorb sunlight instead, you'll probably heat up quite a bit, which will also make you stick out like a sore thumb.

Though you're right; with an internal rail/coilgun, waste heat has to be dealt with onboard. But it is still more advantageous, if the gun infrastructure and the open cycle coolant/heatsink mass needed is less than that of a missile with propellant.

 

[Urwumpe]

Do lasers disperse with the inverse-square law? I thought laser photons were 'collimated' or something, and that they disperse at a different rate... but they still disperse.

Still inverse square law. you just have a higher "gain" because the energy of the laser is better focused. After it left the laser optics, the beam behaves like any ray of light.

 

[fsci123]

I personally believe that very few craft will be made for combat... And most that will be used will most likely be retrofitted or adapted for combat... A possible combat craft with a mass driver could be used to bombard targets or other spacecraft but will probably be used for sending small payloads to the moon or a space station in case a toilet breaks...

Wait i thought antimatter could be found in solar wind and cosmic rays and the van allen belts...

 

[Urwumpe]

I actually already experience such logic problems with the Black Dart project - aside of reconnaissance and typical space taxi missions, its only good combat role is as brain of a complete body of sensor USVs, kill vehicles and cruise missiles. For all the alternatives, something can be found that is better at it. Even bombing runs make little sense with it, though dropping stuff with precision is something the Black Dart can do really good.

It doesn't even need non-navigation sensors at all, drones are better for that. What it needs is being able to be part of the network. All the rest then, is pretending to be just harmless space.

 

[T.Neo]

Wait i thought antimatter could be found in solar wind and cosmic rays and the van allen belts...

I've heard that it is, yes... but not in such high quantities.

I personally believe that very few craft will be made for combat... And most that will be used will most likely be retrofitted or adapted for combat... A possible combat craft with a mass driver could be used to bombard targets or other spacecraft but will probably be used for sending small payloads to the moon or a space station in case a toilet breaks...

Well, I can already see parts from civillian spacecraft adapted into military ones... but I think pure civillian spacecraft would be pretty poor for military tasks... for example an offensive mass driver would not have much use on a civillian ship.

 

[fsci123]

I've heard that it is, yes... but not in such high quantities.



Well, I can already see parts from civillian spacecraft adapted into military ones... but I think pure civillian spacecraft would be pretty poor for military tasks... for example an offensive mass driver would not have much use on a civillian ship.

Well assuming you wanted to launch an object that cant be made from the native resources very easily... Now lets say that the government who has jurisdiction on you and your crews homestead forgot to supply you with a 2160i HD tv and now you and your crew are angry because you may miss Super-bowl LXXXVII and are threatning a protest on living condtions by halting all experiments and research on solar panels... So your government uses a series of mass drivers to launch a capsule so that it can land a few feet from a target a half a mile away from your base... Now if they can launch a tv to a bunch of lazy ased crew than im dn sure they can destroy a hostile craft in orbit... Go figure...:rofl::rofl::rofl:
ITS IN THE CONTRACT THAT WE DESERVE OUR TV!:facts:

 

[Eagle1Division]

I would like to point out that armor on a spacecraft does not have to be heavy and robust. Whipple shields are already in use on many spacecraft, to defend against micrometeoroids and orbital debris. And you could potentially devise a sort of whipple shield against lasers and nukes as well.

About the only defensive measure you should probably take would be a whipple shield - it serves a second purpose of acting like a shadow shield from the enemies' laser blasts at "far" range. If they have a longer effective range than you do, then you can use the shield to hide behind until you're in range. It'll also act like a large radiating surface, for a third useful purpose.

And back to armor - F-15's and F-22's don't go around with the armor of an A-10 Warthog or the resilience of a B-17, and not even the A-10 warthog has the armor of a tank. F-15's and F-22's dropped the armor to increase performance, increased performance means they control the fight, and that advantage is better than having armor. Offense is the best defense, anyways, the best armor is to neutralize your enemy before he can take you out of the fight - That's how airplanes do it and I somewhat expect space combat will be similar - both involve weight restrictions.
Whipple shields are different than what I'm talking about, though. They're very light and very effective. The Ice shield utilizes reaction mass, and even that ended up being too heavy.

And one big point to make is WHY aircraft don't carry any significant type of armor today, while they used to: Anything strong enough to shoot you down will take prohibitively large amounts of armor to protect against, especially when you use things like a hydraulic flight control system, jet engines, etc. Even jet fighters are less vulnerable and more resilient than spacecraft, though. So anything that makes them more resilient or able to survive a direct hit will be prohibitively massive.

As for antimatter, what killed it for me was that the thrust was actually WORSE than it was for IC fusion as listed in Project Rho. Thrust was the only reason I like it so much, and, well, high thrust is wrong. And Thrust Power? You mean the power needed to run the engine? I thought that was provided by the Matter-Antimatter Annihilation.
(Waste heat problem could be solved with super-heated radiators that I described for stealth craft. Make your radiators heat sinks, keep it a plasma but have the container let out thermal radiation (container walls transparent on IR wavelengths. Sure, the walls would still heat up, but they could simply be cooled the same way the rest of the ship was - dump the heat into the heat sink and let the heat sink radiate.) - the fact that it's a plasma means it's so hot it's radiating a LOT of heat, much more than any solid-state radiator could before melting. - Or, as the ISV Venture Star did it: Just use HUGE radiators!)

As for breeding antimatter - it's a method of storing energy: Assuming production efficiency is 20% (We're assuming interplanetary warfare after all, it's not like we're not out there already.) and the engine only has 10% efficiency in using the antimatter - then you only need 50x as much power to produce the fuel as you get out of it. It'd be exactly the same as running an equally powerful fusion engine 50x as long for production purposes.
Sure, it's a lot, but not anything astronomical or prohibitive. Cost-effectiveness becomes questionable, at best, though. But ultimately, if you win and they don't because your vessels were able to "fly in circles" around his, then anything is worth the monetary cost for victory.

But ultimately - the main reason I was arguing for antimatter: being more speedy by all 3 definitions than fusion; including thrust, was wrong. Achieving Brochistrone with fusion is possible, so there's no reason to use antimatter unless you're willing to put in a LOT of resources for a very high Delta-V vehicle.

EDIT:

I personally believe that very few craft will be made for combat... And most that will be used will most likely be retrofitted or adapted for combat... A possible combat craft with a mass driver could be used to bombard targets or other spacecraft but will probably be used for sending small payloads to the moon or a space station in case a toilet breaks...

In the navy, a term that can be used it "platforms" for naval warships. A tanker or any kind of trans-martian transport that can carry a lot of cargo can easily be made into a makeshift warship - just make that "cargo" a nuclear-tipped gift for your Terrain friends. As a bonus, you can install a laser PDS, kinetic PDS, or even a whipple shield, though that last one would certainly be the hardest. Everything else can fit snugly where the cargo is supposed to go. (If it's a closed cargo bay, just get rid of the walls. You don't need them anyways, dunno why they'd even be there...)

As for toilets braking - Astronauts on the STS have had this problem before, I read a book written by one of the guys on board the first time it happened (The book was about different random things about space.). They're pretty good at coming up with solutions... Mind, you will quickly run out of socks. Ever since then though, they carry extra "spacesuit toilets" for this purpose...

 

[fsci123]

I have a strong feeling that if you tried to emnuke a colony on mars it wouldnt work as any space gear would be in someway suited for EM blast from solar flares and other sources of radiation... Pluss it would be very hard to cart nukes across the solar system as they would be super heavy and there is a possibility of them exploding halfway there or not exploding at all... You can launch nukes onto the moon with significant technology...

 

[T.Neo]

Yeah, of course fighter jets don't use armor, like even an A-10 uses armor.

But a combat spacecraft is not a fighter jet. It may have certain parallels to a fighter jet, yes, but it also has parallels to a tank, and parallels to a submarine...

As for antimatter, what killed it for me was that the thrust was actually WORSE than it was for IC fusion as listed in Project Rho. Thrust was the only reason I like it so much, and, well, high thrust is wrong. And Thrust Power? You mean the power needed to run the engine? I thought that was provided by the Matter-Antimatter Annihilation.
(Waste heat problem could be solved with super-heated radiators that I described for stealth craft. Make your radiators heat sinks, keep it a plasma but have the container let out thermal radiation (container walls transparent on IR wavelengths. Sure, the walls would still heat up, but they could simply be cooled the same way the rest of the ship was - dump the heat into the heat sink and let the heat sink radiate.) - the fact that it's a plasma means it's so hot it's radiating a LOT of heat, much more than any solid-state radiator could before melting. - Or, as the ISV Venture Star did it: Just use HUGE radiators!)

When I mean 'thrust power', I mean the power output of the engines. In other words, the kinetic energy of the mass flow. Not the thermal energy or anything, it's basically... the kinetic... power. If that makes sense.

The thrust power equation is, as given on Project Rho:

Fp = (F * Ve)/2

F is thrust in newtons, Ve is exhaust velocity in meters per second, and Fp is thrust power in watts.

When you need huge radiators, you need huge huge huge huge huge huge huge radiators. The ISV didn't do justice to how absolutely gigantic these ungodly radiators have to be.

I'm not sure about your... superhot radiators, but I must confess I did not read about them (whenever 'stealth' enters the equation in terms of space warfare, my mind goes blank). I know, however, that materials have maximum operating temperatures, above which they fail. I'd love some magic radiator that could radiate at 15 000 K. Unfortunately that would require unobtanium, and, well...

Since your nozzle facing material has to be an actual material (even if you cut holes in it and let the heat escape), it can't be at... 15 000 K. It has to be at... maybe a couple thousand K. That's where Molybdenum alloys and ceramics come in handy.

The other problem, is that you need a super-reflective surface, to reflect most of the waste heat photons. But this material can also get pretty hot. A material at 2000 K, that reflects 99.5% of the photons that hit it, is seemingly pretty paradoxical...

The temperature and reflectivity establish the lower size bound of your engine. Even with highly reflective materials at high temperatures, you get... nozzle diameters on the order of tens of meters.

I have a hunch you can tune up the maximum thrust of an antimatter engine, but it'd be extremely difficult to do so. IC seems to be pretty much the only high thrust, high thrust/mass fusion concept out there...

As for breeding antimatter - it's a method of storing energy: Assuming production efficiency is 20% (We're assuming interplanetary warfare after all, it's not like we're not out there already.) and the engine only has 10% efficiency in using the antimatter - then you only need 50x as much power to produce the fuel as you get out of it. It'd be exactly the same as running an equally powerful fusion engine 50x as long for production purposes.
Sure, it's a lot, but not anything astronomical or prohibitive. Cost-effectiveness becomes questionable, at best, though. But ultimately, if you win and they don't because your vessels were able to "fly in circles" around his, then anything is worth the monetary cost for victory.

It is pretty prohibitive. Remember you are expnding that huge amount of energy. And that energy has to come from somewhere; it has to come from the powerplant that supplies the antimatter factory. An absolutely huge amount of energy would be stored up in that antimatter, which would require a huge factory working for a very long time to supply things.

Now when you go to Ceres and you melt down some ice and you seperate the hydrogen from the deuterium (somehow), that is energy... that already exists... it's just sitting there, waiting for you. You don't have to put anything into it; that energy is stored up in those little deuterons already. Sure you have to fly there and set up a little refinery and get hold of the stuff, but it's all there waiting for you- unlike antimatter, which makes you climb a mountain only to submerge you. Antimatter is no energy source, it is an energy sink: It consumes more energy than it emits. It's a necessary evil only, and one for a scenario when only it will do the job (like a high speed interstellar vehicle).

Still... only 10 tons of reaction mass for a 1000 ton spacecraft with a dV of 1000 km/s... that is pretty darn potent! :blink:

Even if it is impractical. But hey, who is going to buy a Bugatti Veyron purely for its practical value?

 

[Eagle1Division]

[...]
It is pretty prohibitive. Remember you are expending that huge amount of energy. And that energy has to come from somewhere; it has to come from the powerplant that supplies the antimatter factory. An absolutely huge amount of energy would be stored up in that antimatter, which would require a huge factory working for a very long time to supply things.

[...]

Still... only 10 tons of reaction mass for a 1000 ton spacecraft with a dV of 1000 km/s... that is pretty darn potent! :blink:

Even if it is impractical. But hey, who is going to buy a Bugatti Veyron purely for its practical value?

It's like this: Ship A uses Fusion, and Ship B uses antimatter. Same Delta-Vee. You take the fusion reactor in Ship A, and let's say instead of producing thrust, that same amount of work is making electricity to go to antimatter production. Ship A can fire it's engines for X amount of time before reaching it's Delta-Vee. Ship A's power-producing reactor would have to work 50 * X long to produce the antimatter for Ship B. But here's what antimatter does that Fusion can't do: keep on working that reactor, and you'll get to 150 * X, working the anti-matter producing plant that long, and you've got 3x the Delta-Vee of the enemy ships. This is something you do years before the war. It may be quicker and cheaper to get Deuterium, but using antimatter you've got a supply of energy stored up tens of times larger than his, ready to unleash in the same amount of time.

Let me stress ten times the Delta-vee for the same mass ratio. Compare the STS and the Saturn V. One has less than twice the Delta-Vee of the other, roughly, and then consider the difference of what they're capable of. A fusion spaceship would be like the STS compared to FIVE Saturn-V rockets for a single Anti-matter ship, if you could add Delta-Vee. Brochistrone trajectories would take a pitifully small amount of your fuel. It's just about the only setup where you'd have enough fuel to pull crazy amounts of unnecessary, but tactically vital, maneuvers. If you're capable of producing this Anti-matter for Interstellar travel, then make an "interstellar" spaceship but use it as an interplanetary one!
Bringing a Fusion-powered ship to a fight with Anti-matter powered ones would be the equivalent of bringing a biplane to a supersonic jet fighter duel.
Actually, biplanes can manage 90mph or so, Jet Fighters only top out at ~800 (of course, depending on the plane). That analogy doesn't go far enough.
Sure, there are other factors, but on a single tank of fuel you could approach him at his same transit speed, stop, run away, stop, come back, stop, run away, stop, come back, stop, run away, come back, stop, run away, stop, come back, stop, run away, stop, and come back, where he had used half his entire Delta-Vee (keeping the other half in reserve to stop) for a SINGLE one of those maneuvers that you just pulled 20 times. Strategically speaking, it would be incredibly easy to "dance in circles" around your enemy. The Delta-Vee of his ships would make you feel more like you're fighting space stations than warships.

Oh, as for cooling the nozzle, why not just use highly reflective materials plus an active cooling system? Work it the exact same way as air conditioning, dropping off the heat at the radiators, to keep your nozzle from melting.

Oh, and operating at 15,000 K is very easy. It's operating at 15,000 K and staying solid that's hard. Super-hot radiators would work as a plasma confined in a container, the container would be transparent on the thermal wavelengths so the heat could escape. A very active cooling system would be needed to keep the walls from melting, it would work the same way as an air conditioner, dropping off heat into the chamber, cooling off, then cycling back again. It would be both a heat sink AND a radiator. I do believe it would be possible, and perhaps many times more efficient than old solid-state radiators.
Oh, and when I say a very active cooling system for the walls, I mean a VERY active cooling system. Less than a tenth the heat would be imparted into the walls, but that would be a LOT if that chamber contains all the waste heat from an antimatter engine firing...
It's also more expensive and many times more complicated. Plasma radiators would only really be for use on ships that NEED to dump an unholy amount of heat. Say for instance, ships with Antimatter engines.
(For that matter, you could trap all the heat into a plasma, then vent the plasma into space and refill the chamber with gas. Heat the gas into a plasma and repeat. Sort of like a super-efficient active cooling system. You'll lose mass with that system, necessitating coolant tanks that get depleted. This could be used on warships during combat, since heat can be used as a weapon of war and a hit meter in space combat at "far" ranges.)

 

[jedidia]

It may be quicker and cheaper to get Deuterium, but using antimatter you've got a supply of energy stored up tens of times larger than his, ready to unleash in the same amount of time.

A few misconceptions here: having stored up 10 times the energy is certainly nice, but for unleashing it in the same amount of time as 10 times less energy also means 10 times the heat, all at once. Ship B therefore has to have a radicaly different design from ship a, with a lot more radiator area that will be there simply to handle the short times of frantic energy release and doing nothing all the rest of the time. If they are to be the same mass, that means ship A will be able to carry a lot more loadout than ship B, and will probably blow it out of the sky by sheer firepower, never mind how much energy ship B had at its disposal.

As such, the analogy would rather go: bringing a biplane with a a complement of radar-guided missile to a fight against a jetfighter with nothing but its gun. That fight is a lot more equalized than what you present, especially if it starts at far range. Of course, this is under the assumption that the ships have the same mass. But here comes an iron law of space combat as we currently perceive it: bigger ships always have the advantage. They also have the advantage over a fleet of smaller ships that together have the same mass as the big ship. Simply because they concentrate much more firepower without redundant systems.

Also, energy != reaction mass. The antimatter you're having there is used to produce the energy, not to drive the ship. You'll still need propellant, it's not like you could just throw that antimatter out of the thruster. Sure, the more energy and efficiency you have the less propellant you need for the same amount of Dv, but if we're talking about 10% efficiency of the drive (which is lousy even for conservative estimates, given that we have the tech to store antimatter) you have to somehow get rid of the other 90% by radiators. There's a point in there where you need more radiator mass than propelant mass...

Having the antimatter production plant onboard also seems redundant. Since it has to be produced long before the fight anyways, it would make more sense to produce it on an orbital site.

container walls transparent on IR wavelengths. Sure, the walls would still heat up, but they could simply be cooled the same way the rest of the ship was - dump the heat into the heat sink and let the heat sink radiate.

Two problems: first, IR is damn ineficent to radiate high heat. You'll have to increase your radiator area hundredfold. Your heatsink is also adding extra mass, and as soon as it is satiated you'll be dead in the vacuum until it's cooled down. Which will be a looong time if you radiate only in the IR spectrum.

second, The IR filters on my ship's telescope to detect your IR radiation weights an insignificant fraction of your radiators. Mass that I can use for firepower instead, that will come in handy after I expended the extra 15 minutes to find your ship.

 

[T.Neo]

It's like this: Ship A uses Fusion, and Ship B uses antimatter. Same Delta-Vee. You take the fusion reactor in Ship A, and let's say instead of producing thrust, that same amount of work is making electricity to go to antimatter production. Ship A can fire it's engines for X amount of time before reaching it's Delta-Vee. Ship A's power-producing reactor would have to work 50 * X long to produce the antimatter for Ship B. But here's what antimatter does that Fusion can't do: keep on working that reactor, and you'll get to 150 * X, working the anti-matter producing plant that long, and you've got 3x the Delta-Vee of the enemy ships. This is something you do years before the war. It may be quicker and cheaper to get Deuterium, but using antimatter you've got a supply of energy stored up tens of times larger than his, ready to unleash in the same amount of time.

Yeah, and it is still extremely hard to make antimatter. That is a huge amount of energy. You're not just picking that energy up somewhere- you have to essentially make the energy. It isn't easy.

Do it years before the war? That is a nice idea, but what if you need more? What if your antimatter production stations are destroyed? What if you do not have antimatter production stations?

If you're capable of producing this Anti-matter for Interstellar travel, then make an "interstellar" spaceship but use it as an interplanetary one!

Yeah... this is why we use long-range aircraft as fighter jets.

It does not work that way. For example an interstellar ship is built for a totally different purpose than an interplanetary ship.

And the whole point of using antimatter in an interstellar ship, is because you need antimatter. It is so intrinsically high-performance that you need to stretch the boundary that way.

With an interplanetary ship, it doesn't quite work that way.

Bringing a Fusion-powered ship to a fight with Anti-matter powered ones would be the equivalent of bringing a biplane to a supersonic jet fighter duel.
Actually, biplanes can manage 90mph or so, Jet Fighters only top out at ~800 (of course, depending on the plane). That analogy doesn't go far enough.

I would not make that comparison. I think, it is better to compare a Me 262 with a pedal-powered aircraft here. The pedal powered aircraft is more advanced and more lightweight and has better materials and whatnot, but at the end of the day, the Me 262 comes out tops... because it is a far more practical design.

What you lose in terms of propellant, in an antimatter spacecraft, you will make up for in nozzles and radiators and containment systems and gamma shields and fluid pipes and stuff.

Oh, as for cooling the nozzle, why not just use highly reflective materials plus an active cooling system? Work it the exact same way as air conditioning, dropping off the heat at the radiators, to keep your nozzle from melting.

Because it is very difficult to get rid of all that heat. You need a lot of coolant and a lot of radiator area.

And it is better when everything runs hot, of course. Because radiators are more efficient the hotter they are.

If you managed to have some sort of supermirror that was only at 400 K, radiating away that extra heat would then become pretty tricky...

Oh, and operating at 15,000 K is very easy. It's operating at 15,000 K and staying solid that's hard. Super-hot radiators would work as a plasma confined in a container, the container would be transparent on the thermal wavelengths so the heat could escape.

A very active cooling system would be needed to keep the walls from melting, it would work the same way as an air conditioner, dropping off heat into the chamber, cooling off, then cycling back again. It would be both a heat sink AND a radiator. I do believe it would be possible, and perhaps many times more efficient than old solid-state radiators.

There are several problems with that:

1. No transparent material is totally transparent, so some heat will be intercepted.

2. The secondary active cooling system will probably require more conventional radiators, which will have nonzero mass.

3. To prevent the plasma from contacting the container, you need to contain it with magnest... which will have nonzero mass.

4. If I have hardware at 2000 K, I cannot cool it at 15 000 K. Bombard 2000 K material with plasma at 15 000 K, and it'll only make the material heat up...

Oh, and when I say a very active cooling system for the walls, I mean a VERY active cooling system.

How active is "very active"? I have made mathamatical models with what one might call "very active" cooling systems, that have turned out pretty painful responses.

Plasma radiators would only really be for use on ships that NEED to dump an unholy amount of heat. Say for instance, ships with Antimatter engines.

There are other problems with antimatter engines. The waste energy from an antimatter engine is in gamma rays (well, the energy you need to worry about: a portion goes into neutrinos, which means you lose efficiency, but they won't fry your ship). And the exhaust products- pions- decay into gamma rays as well.

Now you can make the whole ship out of materials that have a low gamma-ray cross section, so most of the gamma rays escape... but even then, some energy is going to be deposited in the structure. And since these are levels in the hundreds of terawatts at the very least, that is going to be a lot of energy.

On the other hand, there is stuff you want to shield from the gamma rays- such as personnel, weapons, and even the antimatter fuel itself. To do this you have to use shielding, something that absorbs gamma rays readily, such as tungsten.

So you want to absorb most of these gamma rays. Ok, but... now your problem is, you've absorbed all that energy. You have to dump that energy out of the shield or else the shield will breach its operating temperature.

And as gamma rays go through stuff, they can both transmute atoms, and damage crystal structures... so not only will you start to get all sorts of weird elements in your ship that you didn't have at the start, but the structure will get more and more brittle over time.

You might be able to engineer things so that these incorperated elements enhance the strength of the structure, but embrittlement is more difficult to deal with... there are ways to fix it, for example with in-site annealing, but I would imagine these things would be pretty hard to achieve on a practical scale.

(For that matter, you could trap all the heat into a plasma, then vent the plasma into space and refill the chamber with gas. Heat the gas into a plasma and repeat. Sort of like a super-efficient active cooling system. You'll lose mass with that system, necessitating coolant tanks that get depleted. This could be used on warships during combat, since heat can be used as a weapon of war and a hit meter in space combat at "far" ranges.)

Well... an open-cycle cooling system is one option, but the problem is that you'll likely need a lot of mass for it to work, and a lot of mass in coolant offsets having less mass in propellant. Also, just as with closed-cycle coolant, you can not heat something up to 15 000 K from something that is only 2000K.*

Ejecting gas as a weapon would be pretty silly, even using your exhaust as a weapon over great ranges would be impractical, despite things such as Jon's Law and the Kzinti lesson: Usually exhaust spreads out at a wide angle, which means it soon dissipates enough to become harmless.

*Maybe I am missing some critical thermodynamic law here, but I seriously doubt that doing such a thing is possible... and if it is possible, it is likely possible only under circumstances that would be highly impractical onboard a spacecraft.

 

[jedidia]

*Maybe I am missing some critical thermodynamic law here, but I seriously doubt that doing such a thing is possible... and if it is possible, it is likely possible only under circumstances that would be highly impractical onboard a spacecraft.

oh, you can, but the additional heating will consume loads of energy and release additional waste heat... and would require some handwavium that can take the temperatures. It would basically mean dumping low heat into our handwavium, and then heating the handwavium up to 15'000 K. So yeah, it's a really silly idea.

 

[Eagle1Division]

Do it years before the war? That is a nice idea, but what if you need more? What if your antimatter production stations are destroyed? What if you do not have antimatter production stations?

I'm working on the assumption that construction won't play a huge role in the war. What you start with will more or less be what you have for round one. Maybe if you had stuff already under construction you could finish before they arrived for round two, but, seeing as it takes years to travel back and forth, and sending a stream of ships is just about the worse thing you could possibly do strategically, you'd want to send all your ships at once. This means having your fleet ready before the war. Once the war starts, it will probably end well before a significant amount of forces can be built for either side. Especially if one side has a great advantage over the other.

(For reference, what I mean by "round one" is the first time someone sends an attack force. "Round two" would be if that attack forces fails and they send an attack force of their own.)

This isn't WWII. And if I had to compare it, it would be the Pacific naval war, minus the islands, and with much fewer ships. For Mars-Earth war, it would be many months to send forces before they arrive. You can't reinforce them along the way, any ships you're not finished with before you send "Round One" will have to be saved for "Round Two", or, if you're lucky, "Round Three".

Yeah... this is why we use long-range aircraft as fighter jets.

It does not work that way. For example an interstellar ship is built for a totally different purpose than an interplanetary ship.

And the whole point of using antimatter in an interstellar ship, is because you need antimatter. It is so intrinsically high-performance that you need to stretch the boundary that way.

With an interplanetary ship, it doesn't quite work that way.

Delta-Vee isn't just range. It's also your ability to maneuver AND shortening transit time. Jet fighters are built very maneuverable, and very fast.

I would not make that comparison. I think, it is better to compare a Me 262 with a pedal-powered aircraft here. The pedal powered aircraft is more advanced and more lightweight and has better materials and whatnot, but at the end of the day, the Me 262 comes out tops... because it is a far more practical design.

Once again, velocity. The antimatter craft would be the '262. I'm not advocating anti-matter purely on the basis of it being more "high-tech" than fusion (heck, whatever works best is high tech IMO. A good practical knot is more high tech than a fancy machine with many moving parts that does the same thing.), but because of the Delta-Vee equation ( = Ve * ln[R], to be specific), that darned natural logarithm means you can only practically get so much Delta-Vee out of a certain fuel. Heck, the best analogy would be using chemical rockets against NTR vessels. Sure with NTR you have to deal with radiation, and heat, and etc, but it's Delta-Vee advantage is so great that you'd easily choose it over a chemical rocket. I simply can't overstate how great the strategic AND tactical advantage would be to have an antimatter ship instead of a fusion one.

What you lose in terms of propellant, in an antimatter spacecraft, you will make up for in nozzles and radiators and containment systems and gamma shields and fluid pipes and stuff.

Because it is very difficult to get rid of all that heat. You need a lot of coolant and a lot of radiator area.

And it is better when everything runs hot, of course. Because radiators are more efficient the hotter they are.

If you managed to have some sort of supermirror that was only at 400 K, radiating away that extra heat would then become pretty tricky...

The same argument could be made for using a less advanced engine than fusion. Yet fusion is chosen for superior performance, in the same way antimatter could be chosen for superior performance.

There are several problems with that:

1. No transparent material is totally transparent, so some heat will be intercepted.

2. The secondary active cooling system will probably require more conventional radiators, which will have nonzero mass.

3. To prevent the plasma from contacting the container, you need to contain it with magnest... which will have nonzero mass.

4. If I have hardware at 2000 K, I cannot cool it at 15 000 K. Bombard 2000 K material with plasma at 15 000 K, and it'll only make the material heat up...

#1. I covered that.
#2. The heat would be radiated back into the heat sink the same way an A/C unit works.
#3. True, but so does everything else (have nonzero mass).
#4. Back to how an A/C works, you CAN take heat from a 2000K object and use it to heat up a 15000K object. Air conditioning can take the inside of a freezer down to -80*F when surrounding temperatures outside are up to 100*F, It's somewhat basic and that's also how any heat sink works. Except with a heat sink you replace "outside" with the heat sink and "inside" with the rest of the ship. I.e, instead of dumping heat outdoors to cool off the inside of the house, you dump heat in the heat sink to cool off the ship.
Keep in mind, heat sinks don't have to be huge or anything. They're as effective as they're sized, so they can come in the full range of sizes, so there's no need to argue that they'll be too big.

How active is "very active"? I have made mathamatical models with what one might call "very active" cooling systems, that have turned out pretty painful responses.

They'd just have to be active enough to keep the walls of the container cool. Though you can make the walls as transparent as you can across the widest range of thermal wavelengths (that the heat sink emits) as possible (UV, IR, Microwave, etc.), some small percentage of thermal radiation will still be absorbed, and however much it heats up the walls will have to be cooled down to keep heat from building up and melting them. That's how active, active enough to keep the walls cool for whatever small fraction of radiation they absorb.

Well... an open-cycle cooling system is one option, but the problem is that you'll likely need a lot of mass for it to work, and a lot of mass in coolant offsets having less mass in propellant. Also, just as with closed-cycle coolant, you can not heat something up to 15 000 K from something that is only 2000K.*

Well, you would have extra mass for it but not a ludicrous amount. I imagine not very much at all would be needed and the heat sinks would represent a relatively small part of the vessel. There's also the option of using reaction mass in the heat sinks, so you don't have to carry extra just for that purpose. (Though you probably would carry extra mass set aside for the heat sinks anyways, and use reaction mass in the heat sinks as a last resort.)

Ejecting gas as a weapon would be pretty silly, even using your exhaust as a weapon over great ranges would be impractical, despite things such as Jon's Law and the Kzinti lesson: Usually exhaust spreads out at a wide angle, which means it soon dissipates enough to become harmless.

I didn't phrase that well, what I meant was that heat would work something like a hit bar. When that "hit bar" runs out, you're too hot, radiators are already at max capacity, and you're forced to shut down critical systems, taking you out of the fight. So heat is a a weapon of war, and the "sword" in this case is lasers. The "shield" would be large radiators and heat sinks. This re-usable heat sink gives you a tremendous advantage in terms of how long you can keep fighting under repeated thermal laser attack.

A few misconceptions here: having stored up 10 times the energy is certainly nice, but for unleashing it in the same amount of time as 10 times less energy also means 10 times the heat, all at once. Ship B therefore has to have a radicaly different design from ship a, with a lot more radiator area that will be there simply to handle the short times of frantic energy release and doing nothing all the rest of the time. If they are to be the same mass, that means ship A will be able to carry a lot more loadout than ship B, and will probably blow it out of the sky by sheer firepower, never mind how much energy ship B had at its disposal.

As such, the analogy would rather go: bringing a biplane with a a complement of radar-guided missile to a fight against a jetfighter with nothing but its gun. That fight is a lot more equalized than what you present, especially if it starts at far range. Of course, this is under the assumption that the ships have the same mass. But here comes an iron law of space combat as we currently perceive it: bigger ships always have the advantage. They also have the advantage over a fleet of smaller ships that together have the same mass as the big ship. Simply because they concentrate much more firepower without redundant systems.

[...]

I think the Delta-Vee advantage of antimatter is being heavily underplayed, and the mass needed for radiators I seriously doubt would offset that advantage, especially using more advanced designs. Also, when I said unleash it in the same amount of time, I mean that the Fusion-fleet only has X amount of Delta-Vee for the whole war. The Anti-matter fleet has 10X amount. Your actual engine burns can last much longer, but you've got 10X as much energy over the course of the war.

Sure, he can continue to mine Deuterium as the war goes on, but so can you, except you started out with FAR more than he did, perhaps enough so to win the war in the first wave without giving him time for mining new Deuterium to become a significant advantage. Deuterium won't do any good if your refineries on Luna have been leveled, your stations in the outer system have been pulverized, and every other major strategic location has been annihalated by his forces before you could even get halfway to his homeworld. Never mind moving your fleet to defend your asset's, that's simply out of the question when your enemy has ten times the speed (by all three definitions) than you do. Once again, I really, really, really can not over-explain the advantage of having ten times the Delta-Vee of your enemy.

Look at this:
Case 1. You're both spread out over the system. You rally your fleet together, and bring your entire fleet to bear on up to 4 locations across the entire system, overwhelming his smaller pieces of his fleet set to defend each location, and ultimately winning the war because his fleet was spread out, yours was already together, result is something similar to his forces coming at you in a single file line.

Case 2. You're spread out, but your fleets are in orbit over your homeworlds. In this case, you can attack 3 locations of choice, which are completely undefended across the system. After this free move, one of three things happen:
A) His fleet stays defensive over his homeworld. Your anti-matter ships aren't as combat-capable, so you don't attack. It's a stalemate, because everyone, including him, knows (B) or (C) will happen if he attacks.
B) He attacks with all his forces, leaving his homeworld undefended. This will result in 50/50 Mutually Assured Destruction. You might lose your homeworld, but whatever happens, your antimatter ships can come in and level his cities, then chase after and engage his fleets before they arrive at your homeworld!
When your fleets meet, if he wins, then you'll both lose your homeworlds.
If you win, then only he will lose his homeworld.
Either way, he loses, but there's a chance you might win.
C) He splits his forces, some defend and some attack. In this case he will lose everything because his fleet will meet your forces in smaller pieces, once again, something like a single file line (combat square theory, I'll mention this in a sec.).
Case 3. No spread whatsoever. Just two homeworlds, each fleet is in orbit over their homeworld. Being cynical of antimatter designs, assuming they would be less combat capable (even though IMO there's no reason they wouldn't be), and would lose a direct head-to-head engagement with a fleet of fusion-powered vessels.
A) This would be the smartest thing to do; nobody does anything. (no, I'm not saying peace :lol: ). In a sense, though, antimatter fleet v.s. Fusion fleet would mean peace for this reason: 50/50 Mutually Assured Destruction as stated earlier in Case 2.
If he attacks, you go, literally, the opposite way around the solar system, on a course that keeps you out of attack range of his ships, level his homeworld, then turn around and engage his fleet. This is possible because of the better engine performance of Antimatter.
B) You attack him and lose, assuming antimatter ships are for some reason less combat capable.

In all these cases and other times I've mentioned single files lines... I don't know if it's written anywhere, but I'll call it the combat-square theory. It goes like this: If you have 2x the forces, you have 4x the advantage.
If you have 1.1x the forces, you have 1.21x the advantage.
The reason is this: Two ships against one both have twice the armament, and twice the number of targets he has to take out. So you've got 2x the "hit points", or hits you can take, AND 2x the firepower.
This is intuitively understood in this way: You won't win by sending your soldiers in a single file line! Even if you vastly outnumber him, 1 v.s. 20, done 40 times, does NOT equal 40 v.s. 20 in warfare.

Also, energy != reaction mass. The antimatter you're having there is used to produce the energy, not to drive the ship. You'll still need propellant, it's not like you could just throw that antimatter out of the thruster. Sure, the more energy and efficiency you have the less propellant you need for the same amount of Dv, but if we're talking about 10% efficiency of the drive (which is lousy even for conservative estimates, given that we have the tech to store antimatter) you have to somehow get rid of the other 90% by radiators. There's a point in there where you need more radiator mass than propelant mass...

Having the antimatter production plant onboard also seems redundant. Since it has to be produced long before the fight anyways, it would make more sense to produce it on an orbital site.

I was pulling a number out of the air for 10% efficiency. I'm not sure what efficiency actual designs will have, and surely future designs will have more efficiency than current ones (as much as it would be nice to be able to say we know intimate technical details of the future, scientific laws may not chance, but engineering solutions are constantly getting better.)

Of course there's also the option of doing the Delta-V burn for 10x as long, working at a lower thrust so you don't create so much heat at once, giving your radiators more time to work it off. Though I guess in this case antimatter loses the acceleration advantage... Possibly.

Two problems: first, IR is damn ineficent to radiate high heat. You'll have to increase your radiator area hundredfold. Your heatsink is also adding extra mass, and as soon as it is satiated you'll be dead in the vacuum until it's cooled down. Which will be a looong time if you radiate only in the IR spectrum.

second, The IR filters on my ship's telescope to detect your IR radiation weights an insignificant fraction of your radiators. Mass that I can use for firepower instead, that will come in handy after I expended the extra 15 minutes to find your ship.

Once again, I was pulling IR out of the air. Presumably you'd use the best transparent material you could over the optimal wavelength to radiate the most heat and absorb the least. Also, you can use the heatsink/radiator as it's cooling down, it's like a normal radiator but it operates at much higher temperatures, you can use it as long as you don't exceed it's limits. Which aren't 15,000 K, once again a number out of the air. I'm really sorry I'm no good with the precise ranges, but what is sure is that the heatsink/radiator could operate at temperatures far, far above any regular radiator, and thus presumably be more efficient, even if it does have to radiate through a transparent wall of a holding container.

And sure all these systems for using antimatter take mass, but I think that mass consumption will be tiny compared to the increase of efficiency, unless the extra mass needed is more than 10x what's needed for fusion engines. Don't forget fusion is no small technical problem when it comes to heat and radiation, either.
And the fact that the engine efficiency advantage per mass ratio is much higher, at the end of the day, if I wanted the same Delta-Vee, I could carry MORE weapons and sensors per amount of fuel. But, as things would have it, I'm more interested in strategic/tactical mobility than brute armament. The mobility given by Anti-matter engines versus fusion wins an interplanetary war in any scenario I can think of, and ultimately winning the war is what it's about.

...

Phew, don't expect me to make replies like that during the week! TGIF! :lol: