An idea: Firing lines in space?

[speaker-to-trolls]

I've recently been looking over Atomic Rockets quite a bit and it's left me with two conclusions: First that I am hopelessly incompetent when it comes to quantitative science(my eyes seem to slide off the equations like they're unnatural script scribbled by the spawn of obscene and distant stars), and secondly that heat dissipation is much more important in space than most people realise.

In particular I've been looking over the space war pages, and it seems to me a space war would consist of either long range missile duels or close range laser duels, and in the close range combat it seems to indicate that getting rid of waste heat with massive radiator fins would be bad, and you'd have to run on capacitators which have a short useable lifespan. On the order of minutes if you have a big ship. My idea is basically that one can maximise ones available combat time by having different ships fall back behind the main wall of battle once they're getting near the limit and bleed off heat through their radiators while a second line of ships comes forward running on capacitator power and takes up the fight.

Two major problems, of course: You have to have enough ships for this to work, preferably for multiple ranks, and there's nothing to stop the enemy burning down your radiating ships while they aren't fighting. I also had the idea of covering the frontal part of the radiator in a reflective shield, but that of course means the radiator has to be bigger and the rear of your ship becomes absurdly vulnerable. Also the time it takes to radiate away your capacitators battle heat may be too long for this to work.

Thoughts?

[Teleros]

A lot depends on how tough these warships are, because rotating ships out of the front line is only useful if the battles are going on for long enough.

Assuming ships are tough enough though, it sounds like a tactic that would require an awful lot of investment to work...

1. Instead of rotating ships out of the front line like that, what is there to stop a commander from utilising more than the front rank of ships to attack an enemy? Each ship would need to work far less to wipe out the enemy's front line, so what remains of the enemy fleet could be engaged afterwards and hopefully destroyed before the attacking fleet needs to radiate away its waste heat.

2. Radiating ships would still be vulnerable to enemy fire unless there is a physical barrier blocking line of sight - and that wouldn't work against missiles and such.

3. Either way, there'd be a clear advantage to anyone able to reduce the amount of waste heat (or radiate it away earlier). In addition, Atomic Rockets also points out the idea of using an asteroid or similar as a massive heat sink, assuming you can establish yourself on one.

[Sky Captain]

Some ideas.

What about expandable coolant to lengthen effective combat time without deploying radiators. Think about large tank with water frozen to ice and cooled as much as possible before combat, now ship enters combat range, retracts radiators and dumps waste heat into ice. Now the combat time would be limited till the ice is heated up to melting point, melted, water heated up to boiling point, vaporized and vented out. It would allow ship to continue use its reactor to generate power for lasers for some time, but it would be longer than relying on capacitors or batteries. When coolant is depleted only choice of course is to deploy radiator or scram the reactor, if your engine does`t require reactor to operate you also have an option to run away. Hopefully battle is won before coolant is depleted.

[Teleros]

Problem is lugging all that ice (or whatever) around with you as well. Even if you take off from your base empty and stock up on it from ice in the asteroid / kuiper belt, you're going to reduce your maximum acceleration. That may not matter depending on the universe, but it's still a problem.

It should also be said of course that the same problem applies, but on a much larger scale, to the "asteroid as heat sink" idea - you'll have a huge amount of mass, so half-way decent manoeuvring is going to be a pain, unless you have ridiculously powerful engines. Problem then is that engines that powerful will mean weapon systems capable of making short work of most asteroids - so why even use the asteroid in the first place?

[Slacker]

Actually, though, wouldn't using water as a coolant also provide you with a means to survive longer in combat as well? As a countermeasure, ships could release clouds of vented water/steam/whatever, which would interfere (I'd imagine) with laser and perhaps other weaponry as well. It'd also have the effect of maneuvering the ship, so maybe some sort of interesting trade-off effect could occur where you could trade survivability for maneuvering capability and sustained combat capability-that water, once vented, can't obviously sink any more heat, but if the ship's radioactive flinders it wasn't going to do much good anyway.

[Teleros]

As a countermeasure, ships could release clouds of vented water/steam/whatever, which would interfere (I'd imagine) with laser and perhaps other weaponry as well.

Not really, unless there's a hell of a lot of it - as in "too much for a ship to be expected to carry" .

And you can forget about laser defenses like Traveller style Sandcasters. There is no way that they can project a cloud dense enough to do any good.

This would be even more problematic if you're using water, because I'd imagine the water to disperse very quickly, even without the help of a multi-MJ laser or two.

It'd also have the effect of maneuvering the ship, so maybe some sort of interesting trade-off effect could occur where you could trade survivability for maneuvering capability and sustained combat capability-that water, once vented, can't obviously sink any more heat, but if the ship's radioactive flinders it wasn't going to do much good anyway.

This could be useful - as far as fiction goes it'd make for some good scenes - but if you're rotating ships in and out of combat as s-t-t suggests then I wouldn't recommend it, simply because it'll mean your ship is out of combat for longer.

[Jonen C]

If you're going to lug ice around, you might as well put it between the enemy and your ship as extra armor.
And if you're going to haul around extra armor, it might as well be something that takes longer to become useless than ice - you can dump excess heat into rock just as well as ice, but the rock will become so hot that it starts venting heat into your ship sooner or later - the more rock, the longer you have.

Problem becomes an issue of maneuverability.

[Slacker]

As a countermeasure, ships could release clouds of vented water/steam/whatever, which would interfere (I'd imagine) with laser and perhaps other weaponry as well.

Not really, unless there's a hell of a lot of it - as in "too much for a ship to be expected to carry" .

And you can forget about laser defenses like Traveller style Sandcasters. There is no way that they can project a cloud dense enough to do any good.

This would be even more problematic if you're using water, because I'd imagine the water to disperse very quickly, even without the help of a multi-MJ laser or two.

Ah, yeah, I was thinking along the line of sandcasters, but with water. I thought it'd be enough to scatter the beam. What about just serving as crap on the radar to make targeting more difficult? I imagine 'short range' would still be considerably past visual.

[Teleros]

What about just serving as crap on the radar to make targeting more difficult?

I doubt it, because of the emissions a ship will be giving off. Heat, light, and the properties of whatever material you make the ship out of would I'd've thought lead to very different results from an expanding cloud of ice / sand / whatever. And even if you can fool the sensors, it only just takes some bright spark to say "hey, a ship can't just jump 2km to the side like that" for the ploy to be discovered.


Another thought about using an on-board heat sink though: what are you sacrificing for it? Aside from the obvious problem of dragging all that mass around, unless you've enough engineering expertise that it's just a case of spending a couple of billion credits (or whatever) extra per ship then you're going to be making sacrifices somewhere along the line. For example, any ports used to vent the vaporised ice must be placed such that they can't interfere or damage anything else on the hull, which may mean cutting back on some of those other things (say, radiators or something). Positioning of the ice (or whatever we're using for the heat sink) within the ship near weapons might mean it's harder to effect repairs on some systems, etc.

[Sky Captain]

I don`t think there are any viable alternatives to heat sinks unless you want to go into combat with radiators deployed or reactor turned off - both options will seriously degrade combat performance. If enemy is using heat sinks then his ships will be capable of operating longer giving an advantage. What will prevent him from pursuing your ships which just have run out of capacitor stored power and are unable to shoot back, remember at the end of the battle most of the coolant would probably be vented out eliminating slightly reduced acceleration at the beginning of battle.

[Formless]

I think a better solution would be to simply find a way of armoring the radiators, which Atomic Rockets has recently suggested might not be as hard as once thought:

Having said all that, Isaac Kuo is having second thoughts about the impossibility of armoring radiators.

Eric Henry:

The general wisdom, promulgated by the Atomic Rocket website, is that it's hard to armor a radiator and still have it be an efficient radiator.

Isaac Kuo:

I know that's the general wisdom, and I used to believe in it...but I'm now skeptical of it. All you really need is for your armor material to be transparent to your desired operating frequency range. If diamond-like carbon is too rich for your tech, then try IR grade quartz. Either way, the basic idea is the same--your coolant fluid simply flows through tunnels in the transparent armor material. This actually makes for a more efficient radiator than the traditional design.

The traditional radiator involves coolant which conducts heat to the surrounding tubes, which then conduct heat to the radiator surface, which then radiates away heat. This armored radiator skips the conduction steps and simply radiates heat directly from the coolant.

Anthony Jackson:

I tend to assume radiator wings will be lightly armored because they're big, and therefore heavy to armor. However, it doesn't seem that difficult to make radiators that are damage-tolerant enough to not be very tempting targets (the sails on age of sail ships weren't armored, but it wasn't terribly useful to shoot at them).

And that is to say nothing of liquid droplet radiators, which are more resistant to being shot in the first place.

[Lord of the Abyss]

Perhaps you could deploy a large, very thin film of material, rather like a solar sail. Or many of them. Then the ships that need to cool down hide behind them. With the right material, shooting it with a laser will just punch a hole in it I'd think, without destroying the whole thing or letting you see anything on the other side to target it. And you probably aren't going to hit a ship shooting blind. If the fleet's missile defenses are good missiles will have a hard time shredding them too.

Or possibly you could go the opposite route, and bring along "shadow ships" which would basically be flattened slabs of asteroid with an engine attached. Drone vessels with everything on board optimized for heat tolerance.

[Mr Bean]

Everyone goes right to the lasers, nukes my friends nukes aboard missiles are much easier to deal with don't generate any heat from firing (Get it started with a spray can sized burst of air then vector away a tiny bit to let it's engine kick in without giving you any burn marks).


Any realistic form of space combat still comes back to the idea of firing lots or missiles in the direction of your enemy (Even if they are nothing more than kinetic weapons with a engine and a seeker-head) with laser weapons or possibly railguns being last resort weapons for use under 200,000 kilometers. And given how fast ships can get going in space you might only get a brief window before you flash past them.

Short of building your spaceships inside existing asteroids without unobatium materials the speeds ships will be moving at and weapons moving at the same time mean that all impacts are going to be mostly fatal to starships of any size smaller than a massive half a kilometer long ships.

[Ender]

Silicone (or is it silicon?) is transparent to infrared IIRC. So slap some of that on the radiators. Crappy armor is better than no armor at all.

[Sea Skimmer]

Silicone (or is it silicon?) is transparent to infrared IIRC. So slap some of that on the radiators. Crappy armor is better than no armor at all.

It might be transparent to certain infrared wavelengths, but being totally transparent to heat, that doesn’t seem physically possible.

In any case, any kind of protection for the radiators takes mass, and if we have enough mass, we can do all sorts of things. One idea for example, would be just to have a huge amount of redundancy, keep all the main cooling lines inside an armored shell, and then use hundreds of individual heat pipes to transmit heat to the radiator surfaces, each one piercing the armor with a dog leg. The ships own propellant/fuel supply could serve as a heatsink in the event of heavy damage or the need for silent running.

[Formless]

It might be transparent to certain infrared wavelengths, but being totally transparent to heat, that doesn’t seem physically possible.

Eh, hows a little inefficiency going to kill this idea? I would take the protection, if I could pay the mass penalty. A little armor can go a long way, as long as it makes the radiators no more inviting a target than the rest of the ship. If the radiators can survive more, I the ships operator can survive more.

The mass penalty, now that's more of a problem, isn't it?

[Sky Captain]

Everyone goes right to the lasers, nukes my friends nukes aboard missiles are much easier to deal with don't generate any heat from firing (Get it started with a spray can sized burst of air then vector away a tiny bit to let it's engine kick in without giving you any burn marks).


Any realistic form of space combat still comes back to the idea of firing lots or missiles in the direction of your enemy (Even if they are nothing more than kinetic weapons with a engine and a seeker-head) with laser weapons or possibly railguns being last resort weapons for use under 200,000 kilometers. And given how fast ships can get going in space you might only get a brief window before you flash past them.

A lot depends on how good laser and particle beam technology are. Even now prototype laser anti missile systems have managed to successfully shoot down salvo of artillery shells. In a far future it might come to the point it`s nearly impossible to breach fleet`s point defense screen without firing unreasonably huge missile spams. If that happens combat goes mostly to laser duels.

Also comes a question what kind of engine missiles will use. Nuclear engines don`t scale down well and probably is going to be too expensive equip huge number of missiles with them. Chemical drives are cheap and simple, but may lack necessary delta v to successfully intercept nuclear engine equipped ships when fired from light seconds away. For example enemy fires a huge missile spam on my fleet, computers calculate chances of successful interception are slim. Now I wait till missiles accelerate on me (they might be programmed to use 2/3 of their fuel to accelerate and 1/3 for final attack run) then order my fleet to do a hard burn for few minutes to change my trajectory so much those missiles simply can`t intercept me. Now enemy by choosing to open fire from long range have just wasted a lot of missiles.

[Sea Skimmer]

Eh, hows a little inefficiency going to kill this idea? I would take the protection, if I could pay the mass penalty. A little armor can go a long way, as long as it makes the radiators no more inviting a target than the rest of the ship. If the radiators can survive more, I the ships operator can survive more.

The mass penalty, now that's more of a problem, isn't it?

Are you too dense to realize that the efficiency problem and the mass problem are utterly intrinsically linked? If your radiators are less efficient, then you need more of them, and thus more mass. Since you went and increased radiator area… you’ve also got to increase the mass of armor being employed to cover it all too, and expand the ship to accommodate it. Now that mass has gone up, you need more propellant for the ship to retain the same total kinetic performance, which means bigger propellant tanks and those have got to fit into the ship too and presumably be armored too, since loss of propellant will be fatal in space.

If these penalties add up enough, then you might need more reactor power too to keep up acceleration rates which will require more radiator space and…. Wow mass just went up a whole lot more then just slapping some armor on the radiators didn’t it? See the problem here, and the cycle of design trade offs one must engage in when you design a remotely realistic warship of any type?

[Admiral Valdemar]

I would imagine warships would use the idea Skimmer alluded to, which is basically have a nice internalised heat sink that allows at least a few hours of moderate (minutes at high end) use before the radiator wings or armoured radiators need to be deployed. The heat has to be radiated sooner or later, but preferably later and preferably in a controlled manner. Using propellant tanks or empty compartments to store this heat would allow for that. You're going to need some armour anyway, simply to make sure your vessel isn't full of green glowing crew and micro-meteorite holes. If you're performing war in space, you've got the tech to make ships move with more than several layers of gold plated aluminium sheet for skin.

This does depend on the ship's mission profile and so on. A picket that uses DEWs for missile duty will probably require this far more than a missile cruiser sitting back and flinging multiple warheads.

[NoXion]

How good are droplet radiators, and how does their mass compare to solid radiators? I'm guessing that a good compromise is to use a combination of droplet radiators and internal heatsinks depending on the ship's mission profile, with the heatsinks perhaps using the same coolant as the radiators so you can cool some and save having to vent so much.

[Samuel]

Everyone goes right to the lasers, nukes my friends nukes aboard missiles are much easier to deal with don't generate any heat from firing (Get it started with a spray can sized burst of air then vector away a tiny bit to let it's engine kick in without giving you any burn marks).


Any realistic form of space combat still comes back to the idea of firing lots or missiles in the direction of your enemy (Even if they are nothing more than kinetic weapons with a engine and a seeker-head) with laser weapons or possibly railguns being last resort weapons for use under 200,000 kilometers. And given how fast ships can get going in space you might only get a brief window before you flash past them.

A lot depends on how good laser and particle beam technology are. Even now prototype laser anti missile systems have managed to successfully shoot down salvo of artillery shells. In a far future it might come to the point it`s nearly impossible to breach fleet`s point defense screen without firing unreasonably huge missile spams. If that happens combat goes mostly to laser duels.

Also comes a question what kind of engine missiles will use. Nuclear engines don`t scale down well and probably is going to be too expensive equip huge number of missiles with them. Chemical drives are cheap and simple, but may lack necessary delta v to successfully intercept nuclear engine equipped ships when fired from light seconds away. For example enemy fires a huge missile spam on my fleet, computers calculate chances of successful interception are slim. Now I wait till missiles accelerate on me (they might be programmed to use 2/3 of their fuel to accelerate and 1/3 for final attack run) then order my fleet to do a hard burn for few minutes to change my trajectory so much those missiles simply can`t intercept me. Now enemy by choosing to open fire from long range have just wasted a lot of missiles.

Missiles will always have higher delta-v than your ships. They don't have squishy organics and can accelerate alot more than 10 gs if they need to.

[Admiral Valdemar]

That's where Peter F. Hamilton style Combat Wasps come in handy. You have an AI controlled bus for extreme performance, utilising beam and projectile weapons in swarms. Something small and not needing a load of life support equipment, which can deliver munitions or act as a jammer or anything required with a small high thrust powerplant to give you 40 gees, but also more versatile than a basic missile.

[Lancer]

How good are droplet radiators, and how does their mass compare to solid radiators? I'm guessing that a good compromise is to use a combination of droplet radiators and internal heatsinks depending on the ship's mission profile, with the heatsinks perhaps using the same coolant as the radiators so you can cool some and save having to vent so much.

Take a can of compressed air and spray it for 15 seconds. Notice how the temperature of the can goes down. That's basically what a droplet radiator does. It's mass consists of the reservoir you're using to hold the coolant, the coolant itself, and whatever ports you're using to vent coolant from the system. The simplest way to do this would be to have your internal heatsink be the coolant reservoir(s) for the droplet radiator. Internal systems dump heat into the reservoirs, and when you finally need to vent, it sprays pressurized coolant out of the vessel.

For your coolant, you want something fluid, compressible, and with a high specific heat capacity.

[Admiral Valdemar]

You can also collect the matter again so that it's basically a very efficient, non-solid radiator surface. Or, if being attacked by beam weapons, you can disperse the material in the direction of the attack and help dissipate the weapon's energy.

[Sky Captain]

Missiles will always have higher delta-v than your ships. They don't have squishy organics and can accelerate alot more than 10 gs if they need to.

I think you misunderstood me. Small missile with chemical engine will never have as much delta-v as large nuclear powered ship. That`s right, missile will accelerate faster than ship, but it will also burn out it`s fuel even more faster. Chemical powered missile will have delta-v of about 10 km/s whereas nuclear engine equipped ship can have delta-v of about 200 km/s. Think about it, enemy fires missile spam on my ship from 200 000 km distance, missiles approach at about 10 km/s, it would take about 5,5 hours for them to reach me. All I have to do to avoid that missile spam is to do a comfortable 1 G burn for little more than dozen minutes and my ship is out of reach.

Of course if technology is advanced to the point small cheap fusion torch engines for missiles no longer is a problem then this tactic won`t work.