Does physics forbid such a device; a heat destroyer

[Dale]

@DaleSpam: You already need contact to the 2.7K-bath to extract 998kW. You cannot get this and feed a 1000°C-surface with the remaining 2kW. Otherwise you could use this 1000°C-surface again, and extract .998 of the 2kW... you see the problem?

Certainly. I don't see a way around it, which is what I mentioned about the radiator at an intermediate temperature. I don't know how a heat engine could be in thermal contact with deep space rather than a radiator, but I don't know a law of physics that forbids it.

But the second law of thermo is satisfied as long as at least 2 kW/MW goes to space. So I think that anything else is fair game for "future tech". Although, maybe the "future tech" is a way of arbitrarily increasing the effective surface area of the radiator.

 

[Dale]

we would use a radiator as the cold reservoir which would be at an intermediate temperature between 1273 K and 2.7 K, reducing the maximum efficiency of the engine and increasing the surface area required to radiate.

Just out of curiosity I was playing around with this idea and optimizing the intermediate temperature such that the surface area of the radiator is minimized. For any given output power, the lower the intermediate temperature, the less energy needs to be radiated, but the less efficient the radiator. Conversely, the higher the intermediate temperature, the more efficient the radiator, but as the power plant becomes less efficient more energy needs to be radiated.

It turns out that there is a minimum at 955 K (64 m²/MW) which corresponds to a 25% efficiency on the engine. Any hotter than that and the engine becomes so inefficient that the radiator area needs to be larger, and any colder and the radiator itself becomes so inefficient that the area needs to be larger. However, there is a very broad range that is close to the minimum surface area.

 

[mfb]

Why does it grow so much above 1200K? Close to 1273K, the efficiency is ~0 and you have to dump ~33% more heat. However, the temperature is higher by 1/3, which leads to a radiation of (4/3)^4 =~ 3 times the 955K-value. Based on this, I would expect that the required radiator area does not have any minimum.

 

[Dale]

Why does it grow so much above 1200K? Close to 1273K, the efficiency is ~0 and you have to dump ~33% more heat. However, the temperature is higher by 1/3, which leads to a radiation of (4/3)^4 =~ 3 times the 955K-value. Based on this, I would expect that the required radiator area does not have any minimum.

That isn't quite how it works. Close to 1273 K you don't have to dump just 33% more heat, you have to dump an infinite amount of heat.

For example, at a radiator temperature of 1200 K the engine is terribly inefficient (~6.7%). So every 1 W of power produced requires 17.4 W of heat from the hot reservior and so you need to dump 16.4 W to the radiator. This is 448% more heat than the 955 K value (3 W), not just 33% more.

Remember, an engine is rated and designed for the power it produces, not the amount of fuel it burns. I suspect you are thinking of a constant heat input rather than a constant power output.

 

[Dotini]

Question: Is the interesting process which takes place on the sun - going from very hot interior to relatively "cool" surface to very hot corona - an example of the physical process the OP has in mind?

Respectfully submitted,
Steve

 

[mfb]

Oh, you fixed the amount of usable work. Sorry, I thought you fixed the thermal input power as Deeviant does.

 

[Deeviant]

Just to put some numbers on this. Suppose that the heat source is pretty hot, producing heat at 1000ºC (1273 K). And suppose further that the device is in thermal contact with deep space, as I suggested, and so it is using deep space as the cold reservoir (2.7 K). So the Carnot efficiency is 1-Tc/Th = .998. This means that for every 1 MW of heat produced, the device could capture 998 kW as work (or other low entropy forms of energy) and would have to dump 2 kW to deep space to satisfy the second law of thermo.

You can use the law for radiative power transfer for a black body, which is \dot{Q}= \sigma (T_h^4-T_c^4) A. So to radiate 2 kW at 1273 K to a bath of 2.7 K requires an area of .014 m².

You can just scale those numbers up by however many MW you expect your power plant to produce.

The technological advances would be to use deep space as the cold reservoir while radiating at the hot temperature. That isn't something we could do now, we would use a radiator as the cold reservoir which would be at an intermediate temperature between 1273 K and 2.7 K, reducing the maximum efficiency of the engine and increasing the surface area required to radiate. But that would be the limit of what is possible according to the laws of physics as we know them, so that would be the limit of what you could get away with using "future tech" but not breaking the laws of physics.

These numbers get right at fundamentals of what a black-body cooling system would be looking at. But in the end, such a method is not what I was trying to get at. Don't get my wrong, I think using radiative cooling is super useful in space, but it is has been well hashed out in many different sci-fi worlds and it certainly isn't advanced technology, it really isn't technology at all; it's just how the universe works.

It may well be my fictional but physical law obeying spaceship relies solely on black-body emission for cooling, but I was looking for something a bit more... exotic.

 

[Drakkith]

It may well be my fictional but physical law obeying spaceship relies solely on black-body emission for cooling, but I was looking for something a bit more... exotic.

Invent something! It's fiction! Make it logically consistent with known laws as best as possible, but in the end you're going to have to break a rule or two, so go all out!

 

[Dale]

These numbers get right at fundamentals of what a black-body cooling system would be looking at. But in the end, such a method is not what I was trying to get at. Don't get my wrong, I think using radiative cooling is super useful in space, but it is has been well hashed out in many different sci-fi worlds and it certainly isn't advanced technology, it really isn't technology at all; it's just how the universe works.

It may well be my fictional but physical law obeying spaceship relies solely on black-body emission for cooling, but I was looking for something a bit more... exotic.

Honestly, it is much more important that your characters be compelling and the plot be interesting than technical details be correct.

 

[Deeviant]

Honestly, it is much more important that your characters be compelling and the plot be interesting than technical details be correct.

For most stories, yes that is certainly true. However, I am rather uninterested in human emotion and motivation; I am far more interested in the fate of humanity and future of our universe.

However, I don't want to full into a pedantic cycle of physics nit-picking, I want to look into the future.

 

[mfb]

I am highly confident that human emotions and motivations are of crucial importance for the fate and future of humanity.
I do not want to give any estimate for the influence of humanity on the future of the universe, and I do not even have a measure which would allow this.

I don't want to full into a pedantic cycle of physics nit-picking

Where is the problem with large radiators then? It is just an engineering issue, and it is usually fine to assume that those are solved in science-fiction.

 

[Deeviant]

I am highly confident that human emotions and motivations are of crucial importance for the fate and future of humanity.
I do not want to give any estimate for the influence of humanity on the future of the universe, and I do not even have a measure which would allow this.


Where is the problem with large radiators then? It is just an engineering issue, and it is usually fine to assume that those are solved in science-fiction.

The problem is that it doesn't not accomplish the goals I had in mind(I mainly wanted a device that could absorb and convert latent waste heat).

To give you a better picture of what I am working toward, picture this; In the future of spacecraft warfare, all the scenarios I have come up with is that you are completely out of luck as far as defensive systems go. I see no feasible way to create a star trek style "shield", nor any reasonable way to armor a spaceship that would be in any way capable of standing up to even the weapons we could build now, let alone weapons of the future.

Thus, I see only one defense left: stealth. The hulls would be built for stealth, and one important requirement for that would be that the hull would need to cool, specially so it does NOT emit large amounts of highly detectible EM radiation via black-body. And it must remain cool despite housing a large generator of some type inside it.

If anybody has any crazy ideas for possible defensive systems that physics may allow, I would certainly like to hear it, but I could not even think of a system that could sufficiently protect a ship against a large thermonuclear bomb. There just doesn't seem to be any good physics here to grab on too; magnetic shielding would only work against charge particles and requires too much energy anyways, a simply material based approach seems to fail against the furiosity of possible weapons, mirroring might be effective against one of the most obvious space-based weapons(laser) but would completely defeat the stealth idea and would be completely ineffective against kinetic or other more exotic weapons.

So, I would foresee that a futuristic spaceship intent on warfare would somewhat resemble a submarine, not in shape or operation, but in general philosophy. For this reason I imagine a black EM absorbing hull, some method of dumping heat that doesn't act as a beacon, a inertial/kinetic propulsion system as simple as accelerating masses to significant fractions of light (which happens to double as a weapon system).

I have however, conceptualized a few ideas which do bend the rules a bit. For instance:

"Hawking" generators/weapons: Using some unknown process normal matter is condensed and compressed past it's Schwarzschild radius, creating an non-gravitationally induced black hole. Such a small black hole will then almost immediately evaporate via hawking radiation in the form of EM radiation, funny enough this is also a black-body emission. This would allow one to convert mass directly into energy without an matter/anti-matter reaction. I may be wrong, but I assume it radiates energy equivalent to the starting mass as well as the energy introduced via the compression. Other than the obviously enormous challenge of compressing matter to such a degree, I am reasonably sure this idea is in line with accepted physics. Obviously, this would also serve as a tremendous weapon; perhaps have an anti-matter kicker that provides compression energy then resulting in a center mass finding itself within it's own Schwarzschild radius and almost immediately converting itself into extremely hard EM radiation(the temperature of a 500 metric ton black hole would be 2.454406e^17 K, found with this very nice black hole calc ap http://xaonon.dyndns.org/hawking/). Anti-matter is obviously very powerful itself and extremely possible, but has many problems, which the Hawking devices overcome; there is no ready source of anti-matter so it will never be an energy source but rather a most effective means of story and concentrating energy, and anti-matter explosions are nearly as big as you think they would be since it is very hard to get each atom to combine considering the extremely energetic reactor, in fact most anti-matter would likely be wasted with only a small amount actually being converted.

 

[Drakkith]

Well, you could have all ships come with a cooling system that routes the heat to a specific location where and deposited. The resulting radiation is focused into a collimated beam and emitted in a specific direction. Unless you are in the direct line of this beam then you cannot detect it. I can think of a few situations where it would be useful in the book, such as a "lucky break" in detecting an incoming attack by a patrol that by chance stumbles in line of site of this beam.

For defending against nuclear warheads, a laser of some type, perhaps UV or X-Ray could be used for destruction of the warhead before detonation. A nuke in space must be very very close to damage something, as most things in space are many many kilometers away from each other.

 

[Dale]

I have however, conceptualized a few ideas which do bend the rules a bit. For instance:

"Hawking" generators/weapons:

I don't think this is bending the rules as much as you might think: http://arxiv.org/abs/0908.1803v1

 

[Drakkith]

I don't think this is bending the rules as much as you might think: http://arxiv.org/abs/0908.1803v1

That. Is. Cool.

 

[mfb]

Thus, I see only one defense left: stealth.

In this case, I have bad news for you.

You can direct the radiated heat to some extent, but if the enemy is prepared for that the spaceship cannot really hide.

 

[Deeviant]

In this case, I have bad news for you.

You can direct the radiated heat to some extent, but if the enemy is prepared for that the spaceship cannot really hide.

That was an interesting page, with a rather large amount of thought placed into it. However, it really seemed like they came up with a conclusion and then filled in the blanks.

Really though, the only point that I agree with is the black-body radiation is going to be a problem, hence the creation of this thread in the first place. One of the points they seem to keep going back to is that a ship has to have some huge drive plume, this is not at all I how I envision my ship, they will accelerate basically by using a mass driver, which doubles as a weapon. Radar could be easily defeated, a telescope would extremely hard pressed to pick up black ship(which could also have technology to light up it's hull to mimic the background stars behind it).

If push comes to shove, I use a black-body pumped laser and lase the energy out into space in such a narrow beam, a detection systems would simply not be useful. (http://www.freepatentsonline.com/3614663.html).Still though, I want my heat destroyer =/

 

[mfb]

(which could also have technology to light up it's hull to mimic the background stars behind it)

If you know the position of the enemy (and therefore the position on the ship you have to light), which is somewhat strange as you try to make ships invisible (and probably not just the own one). As alternative, you could have light emitters everywhere. In addition, you should try to reproduce the spectrum.

Your mass driver can have a high efficiency, sure. The required high acceleration is not trivial, but might be possible. However, the exhaust is not the main point. As soon as your ship has warm parts, it also needs some blackbody radiation.

 

[Plastic]

what is heat?

radiation? -> photoelectricity.
kinetic energy of a large particle? -> you could annihilate that particle with antimatter and harvest the resulting radiation, destroying the 'heat' in the process.

 

[Dale]

The problem is that it doesn't not accomplish the goals I had in mind(I mainly wanted a device that could absorb and convert latent waste heat).

As described, you cannot absorb and convert latent waste heat to work without a cold reservoir, and even then you are limited by Carnot. However, here are three ideas:

1) They have developed a way to greatly expand their effective surface area for radiation. The bigger the surface area the closer to 2.7 K they can radiate with the radiator serving as the cold reservoir. Since it is slightly higher than 2.7 K the blackbody spectrum would be slightly different, so could still be tracked. But it could be made arbitrarily difficult by making it arbitrarily large.

2) They have developed a way to exchange heat directly with deep space at 2.7 K as the cold reservoir. Although there is no known way to do it, it does not violate the second law of thermo (but it might violate some other laws, I am not sure). In principle, there would still be energy leaving the ship, even if it were at 2.7 K, so there may still be a way to track it.

3) Military ships could be equipped with a material of very high specific heat capacity which is actively cooled down to a few μK (requiring substantial work) during "off duty" times. Then during operations that material could be used as the cold reservoir and the hull kept at 2.7 K without radiating. That would limit the time that they could be stealthed by the amount of time that it would take to heat up the material.

 

[rorix_bw]

I see no feasible way to create a star trek style "shield", nor any reasonable way to armor a spaceship that would be in any way capable of standing up to even the weapons we could build now, let alone weapons of the future. I could not even think of a system that could sufficiently protect a ship against a large thermonuclear bomb.

You do it the same way we do it today. Shoot the missile or jam its radar.

I suggest researching modern warfare especially air and sea. This is almost all electronic now (no more dogfights!). We have both hard and soft kill systems in use today, for preventing missile hits. Modern warships are not significantly armoured in way that World War II ships were, or that tanks are.

Hard kill involves shooting the missile. There are a number of systems for this e.g. AEGIS air defence system on the US Navy "Burke" class Destroyers. This was designed for air defence (against missiles and aircraft) but is now being adapted to defend against ballistic missiles (it has hit them in tests: give it a few more years). The premise of the system is that you fit surface-to-air (SAM) missiles to a ship, add a very sophisticated air defence radar, and theoretically (if it all works, and the crew all do their jobs) you can stop missiles and aircraft from reaching you.

I haven't seen any classified data on this but you can assume it *probably* works as follows: It has 90 missile cells. Each cell holds a single long range surface-to-air missile (SAM), or 4 short range ones (the new ESSM 4-packs). It will shoot 2 of the long range missiles at each incoming air target at about >100km range and each missile *probably* hits 0.5 of the time. At about >50km range it will shoot 2 of the short range ones at any "leakers", with almost certainly higher pH. At point blank range it will use a single RAM missile vs any leaker. In tests, RAM has a 0.9 pH.

I don't know what range they are hitting ballistic missiles at. Ask me again in 10 years. Space combat would probably be extending the ranges.

Soft kill can involve electronic jamming (ECM "Electronic Counter Measures"). For example radar "decoys". These rely on the fact that a missile must somehow be able to find its target by itself (unless you want to put a pilot into it) and do this it has a radar. The radar works by giving off signals that bounce back from the target and by detecing the reflected signals, the device locates stuff. By transmitting "false echos" you can confuse a radar.

An example of such a system is "Nulka". This is a rocket that you launch from a ship, which can hover close to the sea, and gives off signals, making it look, to the small computer and basic radar in a missile, like a ship. Remember that if a missile "misses" it may not be able to turn around and re-attack: Only a small number of modern missiles can turn around for a second go (fuel limit, computer limit, maneuvering limit, G-force breaks the fins off etc) and they can be shot as they turn.

There are also various "ECM" devices that comprise transmitters mounted on the ship itself, that can emit signals, that have the same effect. e.g. "SLQ-32". The large computer on a warship is much smarter than the smaller one on a missile.

More primitive systems used "chaff" which could be described as "reflective confetti" and produced a cloud on the radar that obscured the targets. One even launched a net at the missile (that didn't really work, but in space you might use a gun that shoots a glob of expanding foam or something to catch the missile, then it can have bomb or a TASER or something in the foam cartridge - net projectors certainly have worked in the past). A basic metal grille should stop a missile, if it hits it hard enough to hurt itself ...

Finally, and this sounds crazy, but you also have to locate the target before you can shoot a weapon at it. I don't mean stealth, I mean: Say there's a CVN (aircraft carrier) attacking you, that you want to get rid of. OK, where is it? It's not going to be in sight of the coast as it can strike from over 1,000 kilometers away. (In space, it's painted black and in any case they probably parked it behind the moon and are sending drones out around the moon to attack you. "Behind the moon" is a big place.)

First, your radar and camera satellites don't cover the entire ocean. There are gaps and because their orbits are known, the carrier can sail between them: (no joke, USA used to do this to Russian RORSATS [Radar Ocean Reconnaissance SATellite) but it is harder now with more satellites (a lot harder). However, USA, Russia and China have all demonstrated the abilty to shoot satellites. In space, radar satellites aren't going to be as lopsided as they are on Earth - they will be be just extra spaceships.

Second, the carrier has a sea control zone of several hundred kilometers in any direction created by its air patrols. Your own scouts and satellites entering this zone are certainly going to come under attack well before they cross the "radar horizon" at the point at which they can detect the carrier due to line of sight over the curve of the Earth or in our case "behind the moon". If the scouts have their own radars on, this is even harder as a radar is like a searchlight: The guy you are looking for can detect you very easily by the beam from your searchlight, and will see you before you see him; it's quite easy therefore for him to shoot his rifle at the light then move to a new place - don't stand next to the guy carrying the light - the equivalent to this is a missile that homes in on active radars. There's also missiles that home in on jamming sources - it's a never ending cycle of weapon vs counter-weapon.

Even if your missiles are set for "bearing only launch" with a wide search pattern (Mr Missile, please fly 500 km in direction A then turn on your radar and look for ship targets over 100 meters in length) not only to the missiles themselves also have to survive, and not get their radars turned off, they are as likely to prang an oil tanker as they are the enemy warship. That's probably less likely in space but you never know ... one assumes you will fight for control of planets, and not randomly in deep space.

Finally, if you're in space and using nukes, note that in space, you're going to have land a nuke very close, as there is no atmosphere to create a pressure wave. There's also nothing stopping the other guy using nukes to counter your nukes. He doesn't need to destroy the missile, just damaging its electronic systems is sufficient.

Missiles can evade (modern anti-ship ones do, they are programmed to make radical maneuvers as they near the target to make it harder to hit them) but essentially they have to get within a certain distance of the target so their destination is known, and they do have a big heat source from their engine and a big searchlight on the front called a radar, so they aren't exactly hard to see.

Guns also can be effective against missiles. The reason gun-based defences are being superceeded with electronics and counter-missiles in modern warfare is due to the limited range of guns vs the speed of modern missiles. However, in space with access to lasers and railguns etc, this may be less of a factor. A gigantic "shotgun" may well be able to deal with incoming missiles.

One other thing to consider, you can stick a gun or submunition on a missile. For example a bomb-pumped X-Ray laser. This is supposed to be a nuke that explodes and directs its force forwards via rods that channel the blast; it's sort of a one use laser that doesn't require you to get close to the enemy. Today we have thing like "subroc" which is a missile that launches a torpedo (because the range of a torpedo is limited, and it does not require a separate torpedo system to launch it); many mines also don't explode, but instead launch torpedoes. You could have a single "bus" vehicle that would spit out submunitions - small anti-missile missiles - in the vague direction of any incoming missile.

Some wikis to check out

http://en.wikipedia.org/wiki/Ballistic_missile_defence

http://en.wikipedia.org/wiki/Nulka

http://en.wikipedia.org/wiki/Aegis_Combat_System

http://en.wikipedia.org/wiki/Electronic_countermeasure

http://en.wikipedia.org/wiki/DDG_51

http://en.wikipedia.org/wiki/SLQ-32_Electronic_Warfare_Suite

BTW: I just remembered there have been nuclear tests vs warships. You have to get considerably closer than most people would imagine ... and that's with an atmophere. They have positively pressurised super-structure and decontamination wash-down systems now on warships. I'll to find the results in Google but that is something you may wish to look for.

EDIT: I also remembered the "medium problem". This is "a missile is faster than a sea ship because it moves in the air, and not the sea". But a missile is not significantly faster than an aircraft ... and only recently (e.g. Spearfish @ 70 knots) have torpedoes been faster than ships or submarines.

The Russians actually built a submarine (Akula class - NATO name, Russian "Akula" is a different class) with sufficient speed to outrun the American torpedo of the same period, and the American SR-71 "blackbird" airplane was able to outrun anti-aircraft missiles. The actual missile had similar speed to the plane, but since the missle had to close, if the aircraft saw it and altered course, it would pass behind.

 

[Deeviant]

As described, you cannot absorb and convert latent waste heat to work without a cold reservoir, and even then you are limited by Carnot. However, here are three ideas:

1) They have developed a way to greatly expand their effective surface area for radiation. The bigger the surface area the closer to 2.7 K they can radiate with the radiator serving as the cold reservoir. Since it is slightly higher than 2.7 K the blackbody spectrum would be slightly different, so could still be tracked. But it could be made arbitrarily difficult by making it arbitrarily large.

2) They have developed a way to exchange heat directly with deep space at 2.7 K as the cold reservoir. Although there is no known way to do it, it does not violate the second law of thermo (but it might violate some other laws, I am not sure). In principle, there would still be energy leaving the ship, even if it were at 2.7 K, so there may still be a way to track it.

3) Military ships could be equipped with a material of very high specific heat capacity which is actively cooled down to a few μK (requiring substantial work) during "off duty" times. Then during operations that material could be used as the cold reservoir and the hull kept at 2.7 K without radiating. That would limit the time that they could be stealthed by the amount of time that it would take to heat up the material.

Ok, I think I am still managing to misunderstand you. You say we can not exchange head directly with deep space this day, but my understanding is: it happens for free via black body. The ISS is current exchanging heat directly with deep space right now as we speak, is it not? Or are you taking about some other sort of mechanism, I don't understand what you mean by "is no known way to do it".

@rorix_bw:

I think you are thinking too much in terms of today's battle scenarios. Think of a perfected electro-magnetic slug shooter a future ship may pack; let's say this thing accelerates a slug to 99.99% C. Then let's say it fires a slug at your ship the same instant a photon bounces off the ship and heads your way; the slug would only be a bit behind and that photon hitting your ship would be the first moment you could even possibly realize the ship fired a projectile at you in the first place, let alone avoid it somehow. For all intents and purposes, the thing would be like a laser that shoots bullets. Prototypes for this type of weapon technology exist today, albeit at much slower velocities(although they have to deal with air resistances and a ship obviously would not). And the thing is, I don't even think the future ship would use a railgun but something far worse that we haven't thought up of yet, my point is if beefed up versions of today's technology already defeats any kind of defense I can dream up; then defensive ship technology has only one fallback: stealth.

 

[Dale]

Ok, I think I am still managing to misunderstand you. You say we can not exchange head directly with deep space this day, but my understanding is: it happens by for free via black body. The ISS is current exchanging heat directly with deep space right now as we speak, is it not? Or are you taking about some other sort of mechanism, I don't understand what you mean by "is no known way to do it".

Sorry, I was definitely unclear there. I meant that there is no way that I know of to directly use deep space as a 2.7 K cold reservoir in a heat engine.

 

[Deeviant]

Sorry, I was definitely unclear there. I meant that there is no way that I know of to directly use deep space as a 2.7 K cold reservoir in a heat engine.

I think most space probes use the 2.7 K cold reservoir in a heat engine today. I.E. the voyager probes use a plutonium powered thermopile. Plutonium heats up one side of a peltier device and the other side is cooled via black body directly into space.

 

[rorix_bw]

Gaussian Beam

While composing a reply I was wondering if someone knows: is a gaussian beam the best you can focus a laser to? Can you actaully focus it better than this so it retains its full intensity (same beam width) over a longer distance? Wikipedia isn't clear on this, it only says that some lasers can be gaussian. I know I don't have to link to here, as many guys will know already, but I provide for convenience so you can see what I read, not what the truth is :-)

http://en.wikipedia.org/wiki/Gaussian_beam

 

[rorix_bw]

1) Think of a perfected electro-magnetic slug shooter a future ship may pack; let's say this thing accelerates a slug to 99.99% C.
2) Then let's say it fires a slug at your ship the same instant a photon bounces off the ship and heads your way; the slug would only be a bit behind and that photon hitting your ship would be the first moment you could even possibly realize the ship fired a projectile at you in the first place
3) my point is if beefed up versions of today's technology already defeats any kind of defense I can dream up; then defensive ship technology has only one fallback: stealth

I will address the last point first. You cannot envisage a defence because modern military hardware is complex enough to no longer be obvious to one who has not studied them. Now I am not saying that it must be this way and that modern systems will work in space, but it's clear to me there's large difference between how the average person envisages defences work, and how they actually work.

For point (1), I see you changed to "impulseguns" from nuclear missiles? Well at least we're helping :-)

Thinking laterally (or again copying from modern design) you do not have to absorb the full energy of a projectile to stop it.

Whatever you make the projectile out of, someone can make armour out of, and it will most likely cause both to shatter on impact - in general, you need to be harder than something to survive striking it. Now you need to decouple the armour from the vehicle so you don't have to eat the added momentum of the surviving parts of the projectile that don't bounce off your (obviously curved) armour due to hitting at an angle.

In space we can launch a plate of armour metal, and drift along behind it. Get a drone to drive it perhaps (or maybe you can use a collapsible bracket or electromagnet). This de-coupling should provide protection against the initial salvo. You might get fragments depending on the angles of the hit and the angle your armour plate is at, but that's why you have a second layer of armour. (This system of 2 plates with a gap, with the outer plate shattering hard rounds, resembles some types of modern tank armour - the spaceship difference is that we don't need to attach the inner plate to the outer plate, so we have no momentum transferred on a hit)

As for point (2) I regard a faster than light detection system as cheating in the scenario you defined. The earliest you can fire is when you receive a reflection - with perfect "optics" both ships can in theory simultaneously detect each other and shoot at the same time. (Unless one side is invisible, which is already how it works today if the sides are mismatched).

You're going to have decide what your space combat ranges are and how fast a ship can maneuver. I am assuming no human crew on the combat units (because sci-fi, and the next generation of fighter planes built here on Earth will be pilotless) so the 9G acceleration limit on consciousness isn't relevant. (Maybe just a few techs and leaders in a command unit, everything else is robot)

If you're fighting at close ranges you need to explain how you got there past all the robofighters and missiles. If you're fighting at long ranges you probably aren't using a gun. Earth to Moon is 0.04 light seconds? Probably no chance of target dodging there, but how big is the ship and even a laser will gradually diffuse? (actually that's an interesting question ... i will pose separately)

The defence there is the same as it probably always will be, use decoys, maneuver erratically and use stealth. With so little time to identify and get a shot off, and such tiny targets, something like coming in with the sun behind you in a cloud of (mirrored?) drones might actually work. Decoys sound stupid but they do work. Really they're just another form of camoflauge, which is just another form of stealth. It's way of saying "I am not here" or "congratulations, you have more targets than guns. how lucky are you?"

Anyway stuff to think about. No-one can predict the future of spacewar but you should at least read up on current systems, since otherwise your book is going to be World War II in space.

 

[Dale]

I think most space probes use the 2.7 K cold reservoir in a heat engine today. I.E. the voyager probes use a plutonium powered thermopile. Plutonium heats up one side of a peltier device and the other side is cooled via black body directly into space.

The cold side of the junction is warmer than 2.7 K.

 

[Deeviant]

I will address the last point first. You cannot envisage a defence because modern military hardware is complex enough to no longer be obvious to one who has not studied them. Now I am not saying that it must be this way and that modern systems will work in space, but it's clear to me there's large difference between how the average person envisages defences work, and how they actually work.

For point (1), I see you changed to "impulseguns" from nuclear missiles? Well at least we're helping :-)

Thinking laterally (or again copying from modern design) you do not have to absorb the full energy of a projectile to stop it.

Whatever you make the projectile out of, someone can make armour out of, and it will most likely cause both to shatter on impact - in general, you need to be harder than something to survive striking it. Now you need to decouple the armour from the vehicle so you don't have to eat the added momentum of the surviving parts of the projectile that don't bounce off your (obviously curved) armour due to hitting at an angle.

In space we can launch a plate of armour metal, and drift along behind it. Get a drone to drive it perhaps (or maybe you can use a collapsible bracket or electromagnet). This de-coupling should provide protection against the initial salvo. You might get fragments depending on the angles of the hit and the angle your armour plate is at, but that's why you have a second layer of armour. (This system of 2 plates with a gap, with the outer plate shattering hard rounds, resembles some types of modern tank armour - the spaceship difference is that we don't need to attach the inner plate to the outer plate, so we have no momentum transferred on a hit)

As for point (2) I regard a faster than light detection system as cheating in the scenario you defined. The earliest you can fire is when you receive a reflection - with perfect "optics" both ships can in theory simultaneously detect each other and shoot at the same time. (Unless one side is invisible, which is already how it works today if the sides are mismatched).

You're going to have decide what your space combat ranges are and how fast a ship can maneuver. I am assuming no human crew on the combat units (because sci-fi, and the next generation of fighter planes built here on Earth will be pilotless) so the 9G acceleration limit on consciousness isn't relevant. (Maybe just a few techs and leaders in a command unit, everything else is robot)

If you're fighting at close ranges you need to explain how you got there past all the robofighters and missiles. If you're fighting at long ranges you probably aren't using a gun. Earth to Moon is 0.04 light seconds? Probably no chance of target dodging there, but how big is the ship and even a laser will gradually diffuse? (actually that's an interesting question ... i will pose separately)

The defence there is the same as it probably always will be, use decoys, maneuver erratically and use stealth. With so little time to identify and get a shot off, and such tiny targets, something like coming in with the sun behind you in a cloud of (mirrored?) drones might actually work. Decoys sound stupid but they do work. Really they're just another form of camoflauge, which is just another form of stealth. It's way of saying "I am not here" or "congratulations, you have more targets than guns. how lucky are you?"

Anyway stuff to think about. No-one can predict the future of spacewar but you should at least read up on current systems, since otherwise your book is going to be World War II in space.

To be honest, I'm really not picking up what you're putting down. There is no material that can successful absorb the energy of a .99 C projectile of any significant mass, and your idea of some sort of "decoupled" armor is laughable, you'd have to know where I am in order to put it "in line" with my attack vector; I already said I'm focused on stealth. To put it into perspective, a 1 kilogram projectile traveling at .99 C represents 10.52 MEGATONS of energy, there is NO material conceivable that will be able to withstand that much energy.

It's strange that you basically said I was wrong, then agreed with me; "The defence there is the same as it probably always will be, use decoys, maneuver erratically and use stealth". Maneuverability isn't going to happen, it takes too much energy and mass for a ship of any decent size to rapidly change velocity, decoys are only useful AFTER you have been discovered else you will just give away your general position, that leaves one thing: stealth. As for you WWII in space, that is exactly what I foresee; a scenario similar to WWII submarine warefare.

 

[Drakkith]

To be honest, I'm really not picking up what you're putting down. There is no material that can successful absorb the energy of a .99 C projectile of any significant mass, and your idea of some sort of "decoupled" armor is laughable, you'd have to know where I am in order to put it "in line" with my attack vector; I already said I'm focused on stealth. To put it into perspective, a 1 kilogram projectile traveling at .99 C represents 10.52 MEGATONS of energy, there is NO material conceivable that will be able to withstand that much energy.

Perhaps, but there is no way to accelerate a 1 kg mass to 0.9999c using a single launcher either. It require extremely hard acceleration for a very long period of time to get up to speed using a propulsion system. It takes the LHC almost an hour to accelerate protons up to their top speed, and this is using multiple stages of circular accelerators that are kilometers long, and you're talking about something many orders of magnitude larger. It isn't feasible at all.

 

[mfb]

Well, the LHC needs ~30min because the bending magnets have to be ramped up. Acceleration itself could be done within milliseconds. You will not see bending magnets at the acceleration of macroscopic objects.
However, large objects have serious issues with the maximal acceleration. Acceleration to relativistic velocities within reasonable length (not several million kilometers) is impossible today, and this is not just an engineering issue.