Macross Missile Spam -> The only way to go

[baggers]

Isn't laser diffraction a problem too?

Rule of diffraction in space (perfect vacuum): Se = Lv/Sd * D

http://physics.stackexchange.com/questions/5702/can-we-transport-energy-over-infinite-distances-through-vacuum-using-light

Se= diameter of the ending beam

Sd= Diameter of the departure aperture beam

Lv= Wavelength of the laser (laser is not really a staigth beam of ligth: but a packet of vibrations. So it has some intrinsec dispertion, that depends of his wavelength and the size of aperture)

D= Distance betwen Se and Sd

I will take a 0.01m (1cm) diameter size laser beam. And a X-Ray 0.000000001m vawelength (1 nanometer)

-> at 100km, Se is 2 times Sd: You still hit your target, but at a concentration of heat 4 times lover because your beam is 2 cm diameter.

-> at 1.000km, you have lost 100 times the power: Your beam is 10 centimeters diameter instead of 1.

10.000km: you have lost 10.000 times the power concentration because you have at this range 1 meter diameter beam from a 1cm aperture, because of difraction.

Correct me if i'm wrong.

Edited September 30, 2015 by baggers

[GeneralVeers]

Do you understand the concept of "an object hotter than the background glows in infrared".

Do you understand the concept of "hey, everybody else in this thread probably thought of that already"?

Therefore, the entropy has to be rejected in the form of waste heat. Space has no particles to shed waste heat onto, so it must be radiated

No it doesn't. Easy solution: thermocouples. Which turn heat into electricity.

Other solution: shed waste heat by extending the radiator panels on the side of the ship away from the target. Which means the target can't see the waste heat, because the ship itself is blocking the view.

See? I've got zero experience in space warfare, outside of Master of Orion and Sins of a Solar Empire, and I still came up with two workable solutions that you didn't.

This is the reason. The RCS nozzles on the shuttle will glow.

Sigh. Followed by generic exasperated remark. I already covered this last post. Stealth aircraft solve this problem by concealing the engines and exhaust nozzles inside the plane. By the time the exhaust leaves the fuselage, it has cooled significantly and is a lot harder to spot. I already made it abundantly clear that human military genius has already solved the problem you're going on about.

[Shpaget]

No it doesn't. Easy solution: thermocouples. Which turn heat into electricity.

You're thinking of Seebeck effect, but no, it won't work. The moment you start using it you start radiating.

Other solution: shed waste heat by extending the radiator panels on the side of the ship away from the target. Which means the target can't see the waste heat, because the ship itself is blocking the view.

Easily countered by multiple very simple IR probes scattered around the solar system.

Stealth aircraft solve this problem by concealing the engines and exhaust nozzles inside the plane. By the time the exhaust leaves the fuselage, it has cooled significantly and is a lot harder to spot. I already made it abundantly clear that human military genius has already solved the problem you're going on about.

Stealth aircraft use cold air to cool the exhaust, something that is not available in space.

The atmosphere attenuates the remaining signature.

[KerikBalm]

Isn't laser diffraction a problem too?

Yes, thats why I was positing X rays (because lower wavelength= longer range), large focusing arrays (30-50m radius) and multiple ships acting as a phased array to help constrain the beam.

No it doesn't. Easy solution: thermocouples. Which turn heat into electricity.

Either you've broken the laws of thermodynamics, or you don't have a solution.

Thermocouples will never be 100% efficient... they only work if there is a temperature differential, and currently, they are less than 30% efficient (more like 10%). If you are hypothesizing things with nearly 100% efficiency, then fine, there's almost no waste heat to get rid of in the first place.

The thing is... for reasonable Isps to move a large craft, power output will be several gigawatts at least, one percent of that escaping as heat is still a thermal signature of dozens of megawatts... and of course there is the exhaust plume.

Stealth aircraft solve this problem by concealing the engines and exhaust nozzles inside the plane. By the time the exhaust leaves the fuselage, it has cooled significantly and is a lot harder to spot.

Stealth aircraft can have their exhaust lose heat by conduction.

Exhaust in space will not cool like that... it will cool by emission of blackbody radiation... that exhaust plume needs to cool down to nearly absolute zero to not show up. RCS exhaust is already really really cool relative to the sort of engine you'd see in a space warfare scenario (ie, something with enough Isp that you can actually move around a reusable space warship).

That plume is not going to cool down nearly enough in the time it takes to traverse 1 ship length.

Other solution: shed waste heat by extending the radiator panels on the side of the ship away from the target. Which means the target can't see the waste heat, because the ship itself is blocking the view.

Directional radiation is the only method that I think is dismissed too easily.

*if you already know where your enemy is (the counter argument is how can you know where your enemy is if stealth exists), then you can direct your radiation away from them.

Its also assumed there will be many probes and sensor systems launched that can send telemetry to the fighting ship.

If you have probes observing an area from multiple angles, then stealth of this nature doesn't work.

I would argue that stealth could work against Earth right now... as long as one doesn't radiate in the direction of Earth, they should be able to hide a spacecraft.

More generally, as long as you don't radiate in the ecliptic plane of the solar system, we humans aren't going to detect you.

The problem is.. there is no directional radiation for your exhaust... as soon as you want to alter your orbit, you will be detected.

I suppose there are very low thrust ways to get around this, like light propulsion... but certainly not something that is going to cause large accelerations.

Also, that is assuming some massive technology asymetry.

An enemy that is on somewhat equal technology and development ground won't be limited to observing you from the ecliptic plane...

Plus... directional radiation means very inefficient radiation, and with heat sinks and radiation rates being very important for laser/high Isp combat ships, your ship will lose.

If you don't use a laser... well, nothing is perfect, if you get close enough, you will be detected even if you try to present a cold face to all enemy sensors (how do you even know where all the sensors are if this sort of thing works?)... before you get within reasonable kinetic kill range... and those projectiles will be detectable, and their trajectories can be used todetermine your trajectory when you launched them... and since you can't fire up any sort of reasonable engine... you'll be right where they though you were when the incoming laser fire blinds your ship.... heats up the side facing the enemy enough that they can easily detect you (like active radar, but with xray photons instead of radio photons), and deliver killing strikes....

Then they leisurely destroy your kinetic projectiles with their lasers.

Game, set, match, non stealth laser ships win.

[RainDreamer]

I think stealth ships will never be battle ships. Cutting down all weapons system and be a really small/fast target will allow your ship to hide more efficiently, along with dumping heat through disposable heat sinks and launch them using cold gas inside vacuum-sealed cannisters will allow detection of your ship way too late for any action. This would make it a great espionage/scout ship, but not going to be able to come close to any other ships or engaging in any kind of combat.

[SomeGuy12]

No it doesn't. Easy solution: thermocouples. Which turn heat into electricity.

Entropy says this won't work (see Shpaget's reply).

As I said, you're not one of the posters that genuinely understands science and engineering, or you would have known this instantly.

[GeneralVeers]

You're thinking of Seebeck effect, but no, it won't work. The moment you start using it you start radiating.

Heat isn't going to radiate if it gets turned into something else. Such as electricity.

Easily countered by multiple very simple IR probes scattered around the solar system.

Which are the first targets to get blown up. Or jammed or hacked or whatever else. Once again (recurring theme!) that's something that has already happened in past wars. Warring nations have always devoted a significant portion of their war effort towards destroying, spoofing, or otherwise thwarting the other side's surveillance network. The "no stealth in space" arguments in this thread are all depending on perfect recon--which doesn't happen in a real-world war, space or otherwise.

Stealth aircraft use cold air to cool the exhaust, something that is not available in space.

Then use something else. Like exhaust nozzles cooled by the fuel itself (something several models of real spacecraft engines already do--the goal isn't stealth, it's usually to preheat the fuel, but this idea can be adapted for stealth in space).

Thermocouples will never be 100% efficient... they only work if there is a temperature differential, and currently, they are less than 30% efficient (more like 10%).

Which means a 10-30% reduction in the infrared signature.

that exhaust plume needs to cool down to nearly absolute zero to not show up

Wrong. At half the temperature the effective detection range gets cut in half. Any heat source becomes too dim to spot at a certain distance, depending on the temperature of the source, and the sensor resolution and viewing angle (the problem for the searcher being that a narrow viewing angle to improve detection requires lots of sensors for 360-degree coverage, which is more expensive and heavier--and if you play KSP, you know how big a deal "heavy" is!)

RCS exhaust is already really really cool relative to the sort of engine you'd see in a space warfare scenario (ie, something with enough Isp that you can actually move around a reusable space warship).

Unprovable. You have no idea what kind of engines, at what power levels, we're actually going to see in space. That's one of the things we can only guess at.

That plume is not going to cool down nearly enough in the time it takes to traverse 1 ship length.

It already does with current stealth technology. Hell, even the A-10 Thunderbolt's extremely cheesy method of masking its infrared signature (rear control surfaces surrounding the engines to the sides and below) makes it very difficult for a defender on the ground to get an infrared missile lock. That trick will certainly work in space: surround the exhaust nozzle with fins (or simply make the exhaust nozzle bigger) to give the exhaust more time to expand and cool before it's visible.

And here's another trick: four engines, each at one-quarter the power. Thereby splitting up the one heat source into four smaller ones.....

The problem is.. there is no directional radiation for your exhaust... as soon as you want to alter your orbit, you will be detected.

.....if the ship is close enough to a sensor for whatever temperature the exhaust is.....and if the sensor is looking in the right direction. There's the "perfect recon" fallacy again. Can't rely on that.

I think stealth ships will never be battle ships. Cutting down all weapons system and be a really small/fast target will allow your ship to hide more efficiently, along with dumping heat through disposable heat sinks and launch them using cold gas inside vacuum-sealed cannisters will allow detection of your ship way too late for any action. This would make it a great espionage/scout ship, but not going to be able to come close to any other ships or engaging in any kind of combat.

Exactly! That's how modern stealth aircraft already operate (there's that thing about the real world again!). A stealth design means a lighter weapons loadout at higher cost (largely because you have to have internal weapons bays--external weaponry shows up like a Christmas tree on radar). The tradeoff is a more expensive craft, delivering fewer weapons, but with a higher chance of surprise and a higher chance of the craft coming back in one piece.

ALERT: INCOMING BUZZKILL. TAKE EVASIVE ACTION.

Truth is, unless we either encounter aliens or establish colonies on other planets which then revolt and become independent, we're not going to see an actual space war. Rather than firing at Russian spaceships, for example, it would be much easier to fire at Russia.....

[SomeGuy12]

Wedge, you're wrong. You cannot turn heat into electricity without releasing mostly heat because heat has more entropy than electricity. Go pick up a textbook and verify for this yourself.

We aren't making wild guesses when we say the plume from a rocket engine has to be hot and thus the actual gas molecules will also radiate in infrared. No engine design that gives performance better than "pathetic and useless" exists that doesn't have a hot exhaust. And that's after 40 years of rocket science. The plume itself must be a massive stream of gas, because (1) with high ISP, the exhaust velocity of the gas must be very high and (2) with high thrust, there has to be a lot of it.

That's all you have to detect.

[Red Iron Crown]

People, please restrict the discussion to the topic rather than the personalities or education of other posters. Ad hominem arguments are valueless and only serve to incite people, if you cannot make your points logically and without condescension or personal attacks then perhaps you should not bother posting.

[Shpaget]

Which are the first targets to get blown up. Or jammed or hacked or whatever else. Once again (recurring theme!) that's something that has already happened in past wars. Warring nations have always devoted a significant portion of their war effort towards destroying, spoofing, or otherwise thwarting the other side's surveillance network. The "no stealth in space" arguments in this thread are all depending on perfect recon--which doesn't happen in a real-world war, space or otherwise.

There is a vast difference in hiding an active ship that is supposed to shoot terrawatt lasers and dodge incoming fire, and small passive telescopes that use a few watts for their cameras.

[RainDreamer]

If only we have portal technology. Poke radiators into the portal and have them dissipate heat elsewhere safe.

[Rune]

First of all, guys and gals, let's not feed trolls and get this thread locked. Ignore list is there for something, if needs be.

Wedge, the fact is, some of the posters on this forum know what they are talking about, and the majority don't. So calling an argument "unresolved" when the posters on one side of the argument don't know basic physics or engineering, and the posters on the other side do, is misleading.

I know a lot of both and hold several degrees. Obviously that doesn't mean much unless I'm going to reveal my IRL identity, but from my perspective, the arguments are actually over.

1. I know, from my personal knowledge of physics and engineering, and the arguments given here, that ultimately laser weapons are the only way to go, because there is no way to stop the beams and if at least 2 beam frequencies are in use, no way to reflect them. However, I also know that the enormous pieces of equipment, weighing thousands of tons, needed to generate and focus even soft x-ray beams may mean there is a brief period of time before anyone invests that much money where simpler kinetic weapons may rule the day.

2. I know, again from both personal knowledge and the arguments give, that there is not any stealth in space except around the handful of places in space that give you cover, such as large planets. The rest of the time, it's a wide open battlefield, and range is king.

The more efficient the rocket engine you devise, the bigger the flare of infrared light you must emit in order to use it. This is because kinetic energy of your rocket exhaust stream scales with the square of the exhaust stream velocity. Ergo, if you double ISP, you must quadruple the required energy, and a rocket exhaust stream has low entropy compared to the power source driving it. This means you must have gigantic heat radiators in order to use any kind of high performance rocket. This is why even the mediocre performance space shuttle RCS plumes can be seen from the asteroid belt, and a nuclear thermal rocket would be visible from anywhere in the solar system. And don't even think of cloaking a fusion or antimatter drive, either of which will glow like a star.

You can't get into weapons range of someone if you don't maneuver, and the moment you maneuver, "bloop. contact detected, no IFF, mass estimate is warship class. Shall I arm weapons, commander?"

So from my perspective, the arguments are resolved. I have not seen any arguments from a poster that are supported by actual facts and knowledge to dispute #1 and #2.

Couldn't have put it better myself.

How accurately can a spacecraft hold its attitude? Wouldnt that also affect the range of a laser weapon due to the aiming being off?

Lets assume the maximum error in aim is of around 4 meters. Current space telescopes can hold an attitude with 0.007 arsecs of accuracy, that gives us that the maximum engagement distance is of 83000 kilometers. Lets also say that the approach speed is of 6 kilometers per second, which is sort of reasonable considering the distance between colonies and the orbital mechanics associated (say a moon colony vs GEO colony). That gives us an engagement time of almost 4 hours, that doesnt seem too long actually. What do you guys think?

You can set the beam to wide angle and gradually narrow it. (adjustable elements in the telescope). This lets you calibrate for conditions, as you can empirically discover the correct set of mirror settings this way. You could do the calibration much faster by using several laser frequencies and several sets of mirrors and adjusting each mirror asymmetrically.

This will stop systematic errors that are constant during the calibration period. Once you are zeroed in and have a narrow patch of laser light impinging on the enemy hull, burning a hole or just warming the surface, you can correct for small attitude errors by adjusting as the beam tracks due to attitude error.

Still, yeah, in some cases, I think the beam would kind of wobble over the enemy spacecraft, semi-randomly damaging different parts of it. Especially if your spacecraft is taking hits, causing outgassing and flexing as the whole structure bends back and forth chaotically.

So we are zeroing out in reasonable ranges within the tens of thousand kms (order of magnitude up or down), and at those ranges, near-term optical lasers with comparable optics to our present-day telescopes can already play at blinding themselves. They would also be fearsome things at closer ranges, so no CIWS required to back them up. And much over their range, relativistic effects ruin the party anyway. Given that, the appetite for exotic X-Ray FEL lasers measuring kms in length, I think, will be small to nonexistant, for a long time. Such size of weapon almost counts as a fixed installation by default, and fixed installations are kinetic fodder. So yeah, in a sense, "macross missile spam" makes sense, but with unguided projectiles to overwhelm CIWS of fixed installations. You know, because you have to actually vaporize the rocks instead of side-stepping them neatly. Not much of a "macross missile spam", and more of a cold war nuclear exchange type of thing. Have I already said it's not a good thing to be a civilian in a space war?

Anyhow, in some ways, this is still quite random at the extreme ranges... a small technical superiority may be key, one side might have an incentive to speed up and "hunker down" wile they get closer to their effective range, with all optical apertures closed. And you certainly must count that the enemy will have a good read on your general capabilities, and won't be very far from them. I think in these scenarios, the laser drones I described in the other thread make a lot of sense... it will be a very ablative battle, as each side progressively losses weapon and sensor platforms as they start coming into range of each other, while trying to keep some active for later on. Dense volume of concentrated fire, or ablative defense in depth? I guess that depends on who thinks that he has the upper hand... We really are finally coming into the tactic, and not strategic, level! It would still be nice to somehow restrict ourselves to one drive/tech level, but hey, some general conclusions should still be possible.

Rune. Another interesting question: at what point do lasers retire present-day kinetic weaponry, exactly?

[shynung]

Another interesting question: at what point do lasers retire present-day kinetic weaponry, exactly?

The time when an electric power generation system that has a high power-to-weight ratio, good portability, and good reliability gets invented. Right now, internal combustion engines fill that role, and they're not very efficient. Nuclear power sounds good, but it somehow gathered a negative stigma, so we don't have portable reactors right now.

Edited September 30, 2015 by shynung

[briansun1]

Rune. Another interesting question: at what point do lasers retire present-day kinetic weaponry, exactly?

Exactly? I guess it would depend on how quickly we get into space and want to start shooting each other, and if lasers are an improvement over kinetics. So, probably whenever a fleet armed with lasers beats a fleet armed with kinetics. Much like in the past with the wood to ironclads, Pre-dreadnaughts to dreadnaughts to Battleships, Battleships to aircraft carriers, or prop to jets

[Creature]

I think many of the questions and arguments in this thread would benefit from more clearly defined parameters. Like what's the range the engagements are happening at? Where are the crafts coming from and how fast? Are they highly maneuverable? How big are they? If we assume scaled up laser technology, how does the heat shielding technology hold up?

If we go with today's technology, I'd say missiles are very good against any space target but so are lasers. And pebbles, too.

If we're on the more sci-fi end of the technology spectrum with a highly maneuverable ship closing in at relativistic speed behind a massive heat shield then kinetic armament could be useful. If the attacker is able to dodge well enough and keep the evasive maneuvers up for a long time, it's almost impossible to hit it effectively until it's well within a few light minutes at best. If that's the case, then I could imagine firing similarly powered relativistic torpedoes to meet it half way. Even a shrapnel hitting the craft would make for a nice explosion at those speeds. If it's coming in at for example 0.1c, you'd need some hefty lasers to completely vaporize several tons of heat shielding before it makes a pass and unloads whatever attack payload it's carrying. Obviously that sort of propulsion is complete fiction, but so are laser battles in space in general

[wumpus]

Do you understand the concept of "an object hotter than the background glows in infrared". "Most of space is empty of all objects, glowing or otherwise". "A rocket exhaust stream is a stream of high velocity particles going the same direction." This is less entropy than the chaotic sea of high energy particles you get when you combust 2 chemicals, fuse or fission some atoms, or react matter and antimatter. Therefore, the entropy has to be rejected in the form of waste heat. Space has no particles to shed waste heat onto, so it must be radiated, as convection/conduction do not work. You have to radiate to a significant portion of the sky, or you are also creating an impedance in your heat rejection system by trying to radiate energy in a low entropy form.

While such observations are certainly possible, I still think you are ignoring the severity of the problem. You still need sensors that can detect objects that merely have to contain a laser, a power supply, and some sort of heat-sink (presumably a liquid and vacuum chamber that can keep flooding the chamber so you can mask the IR until the laser has fired). Expect this to be few meters in a sea of millions of km. About the only real advantage you have is seeing that IR signature pop out against a 3K background, but you still need either outrageous resolution (or more likely sensors *everywhere*). Hubble can resolve about 25km on Mars (and I would assume this means pictures taken in 2003 with the 56 million km distance), this won't help at all with a stealthy ship. Not only that, but you effectively have to get near-meter resolution *in*all*directions*all*the*time*. No mere 2-d sweep with detectional RADAR, expect sensor ships *everywhere*.

This brings us back to the title of the thread "macross missile spam". It is entirely possible that the economics, not the physics will drive the stealth ship. The "gotta detect 'em all" problem just gets too expensive. You wind up with a situation like the cold war where there all multiple nukes for each target, largely for certainty of one getting through but also helping the PR "I've got more bombs than you!". I still expect that I would want the sensors made, though I don't know what the price tag would be.

It already does with current stealth technology. Hell, even the A-10 Thunderbolt's extremely cheesy method of masking its infrared signature (rear control surfaces surrounding the engines to the sides and below) makes it very difficult for a defender on the ground to get an infrared missile lock. That trick will certainly work in space: surround the exhaust nozzle with fins (or simply make the exhaust nozzle bigger) to give the exhaust more time to expand and cool before it's visible.

You really can't mask an IR signature. Your best bet is to simply reduce thrust enough to hide it in the noise (although your detector can average it out, so unless you have a noisy signal behind you it won't help at all). Most of the ideas I've seen break thermodynamics (the one I've listed with single evaporation "cycle" shouldn't, it just is extremely limited), this one seems to have invented the rocket anti-bell (seriously, look up what a rocket bell does and compare it to this suggestion).

[Mazon Del]

I think many of the questions and arguments in this thread would benefit from more clearly defined parameters. Like what's the range the engagements are happening at? Where are the crafts coming from and how fast? Are they highly maneuverable? How big are they? If we assume scaled up laser technology, how does the heat shielding technology hold up?

If we go with today's technology, I'd say missiles are very good against any space target but so are lasers. And pebbles, too.

The problem we get right now is that ALL of the parameters concerning the scenario and ship design are open to discussion. Are we talking just LEO ranges, Earth/Moon, Earth/Mars, etc. All these ranges change fairly drastically what weapons are viable at all without even considering the various (realistic) technologies those weapons might have. Similarly, questions about how maneuverable the ships are involves a lot of guessing about the thrust/weight ratio of the ship as well as the speed with which the ship can change its attitude. While we can certainly KNOW how good various systems are in modern day, but we do not know how they will be brought together. A craft the size and mass of the shuttle might be reasonable given some parameters and in others an SSBN might be thought to be more accurate.

The only thing that can be said with certainty is that lasers have the largest effective range, missiles are likely the most precise but also the most massive, and ballistics are useful only in very specific arrangements, but in those arrangements they are the most effective.

I've been (very slowly) working on a simulation system that lets the user put in a lot of statistics about the craft in question, their weapons, etc. Then place them in whatever orbital paths are desired in an effort to allow for a more empirical analysis of these sorts of questions. Don't hold your breath though, it'll be a while. Plus I might hold off on any release till I've written a paper on the results of a set of scenarios. T-T

[GeneralVeers]

The problem we get right now is that ALL of the parameters concerning the scenario and ship design are open to discussion.

Bingo.

Wedge, you're wrong. You cannot turn heat into electricity without releasing mostly heat

You're missing the point. A ship that uses thermocouples to turn some of that heat into electricity releases less heat.

Modern stealth isn't about making an object completely disappear off the screen--that's impossible. The goal is to reduce the objects radar and infrared signature enough that the computer controlling the radar can't pick the object out from the background.

We aren't making wild guesses when we say the plume from a rocket engine has to be hot

Uhh.....yes. You are. Rocket engines don't have to be hot, and making the logical conclusion "they are, therefore they have to be" is a mistake. The reason all modern rocket engines emit hot exhaust is because nobody cares. They're civilian ships, nobody's shooting at them, and a massive infrared signature is not a problem. If a space war breaks out, that will change.

There is a vast difference in hiding an active ship that is supposed to shoot terrawatt lasers and dodge incoming fire, and small passive telescopes that use a few watts for their cameras.

And emit radio signals in order to transmit their findings back to base. And jamming that kind of signals is already part of modern warfare in the real world.

Side note--terawatt lasers?? Are you familiar with, for example, the YAL-1 airborne laser for intercepting ICBMs in boost phase? It's a real-world laser that has been tested and does work (though the project was shelved). That laser is megawatt class. And the firing platform is a modified Boeing 747. To get into the terawatt range, you need either a million times the power generation or a million times the battery storage. Which will not fit in any reasonably-sized starship without massive technological breakthroughs that cannot be relied on to happen. So, terawatt-range lasers? Not happening any time soon.

You really can't mask an IR signature. Your best bet is to simply reduce thrust enough to hide it in the noise

Exactly. Beyond a certain range, we humans can't see spaceships such as the Dawn space probe. Beyond a certain further range, we can't see planets. Go further, and we can't see individual stars--only entire galaxies.

Stealth in space is all about the numbers. And we don't know what those numbers are, so you cannot simply handwave the entire concept out of existence.

[RainDreamer]

I guess it is related to the range of the weapon? If a weapon can hit at a distance far enough where the ship it shoots from looks like anything else in the back ground, it can essentially launch a stealth attack. Though after that it would be instantly detected...

Maybe stealth is not possible now, or in near future, but in far, far future, it might happen based on some absurdly ground breaking technology?

[Mazon Del]

Maybe stealth is not possible now, or in near future, but in far, far future, it might happen based on some absurdly ground breaking technology?

Of course. But the problem is that it's also easy to say that in the far, far future we might have figured out some sort of sensor that can detect any mass greater than several hundred kilograms within numerous light hours thus making your ability to hide your heat and radar signatures moot. That sort of discussion, while entertaining at times, doesn't really actually end up settling much when ostensibly the purpose of the discussion is to gain an idea of what is possible in a now-ish time frame.

[Kryten]

You're missing the point. A ship that uses thermocouples to turn some of that heat into electricity releases less heat.

No it doesn't, that would break the laws of thermodynamics. Thermocouples generate a current from the transfer of heat down a gradient, you still get the heat transfer.

[SomeGuy12]

Uhh.....yes. You are. Rocket engines don't have to be hot, and making the logical conclusion "they are, therefore they have to be" is a mistake. The reason all modern rocket engines emit hot exhaust is because nobody cares. They're civilian ships, nobody's shooting at them, and a massive infrared signature is not a problem. If a space war breaks out, that will change.

Describe for me a potential rocket engine design that has ISP above 100 and does not involve a massive thermal signature. This means you must have an exhaust velocity of 1 kilometer/second with respect to your ship. Keep in mind that the heat radiators to shed the waste heat from your energy source count as well as the exhaust plume. "Engine design" means all critical components - don't say a "photon drive" without including the power system.

[Shpaget]

And emit radio signals in order to transmit their findings back to base. And jamming that kind of signals is already part of modern warfare in the real world.

Directional antennas are a lot easier to make than directional heat radiation. They also work at much lower powers.

For example, New Horizons transmitter is a 12W thingy and has a half-power beam width of about a degree.

Side note--terawatt lasers?? Are you familiar with, for example, the YAL-1 airborne laser for intercepting ICBMs in boost phase? It's a real-world laser that has been tested and does work (though the project was shelved). That laser is megawatt class. And the firing platform is a modified Boeing 747. To get into the terawatt range, you need either a million times the power generation or a million times the battery storage. Which will not fit in any reasonably-sized starship without massive technological breakthroughs that cannot be relied on to happen. So, terawatt-range lasers? Not happening any time soon.

Okay, maybe I misspoke. Not terawatt... Whats the next bigger prefix? Petawatts... Yeah, that might do.

I'll refer you an earlier post in this thread, where beggers explains why you need such levels of power.

http://forum.kerbalspaceprogram.com/threads/135385-Macross-Missile-Spam-The-only-way-to-go?p=2221733&viewfull=1#post2221733

Yes, I'm aware of YAL-1, and it's a toy compared to what you'd need in interplanetary conflicts at distances of millions of kilometers.

Edited September 30, 2015 by Shpaget

[SomeGuy12]

Directional antennas are a lot easier to make than directional heat radiation. They also work at much lower powers.

For example, New Horizons transmitter is a 12W thingy and has a half-power beam width of about a degree.

Okay, maybe I misspoke. Not terawatt... Whats the next bigger prefix? Petawatts... Yeah, that might do.

I'll refer you an earlier post in this thread, where beggers explains why you need such levels of power.

http://forum.kerbalspaceprogram.com/threads/135385-Macross-Missile-Spam-The-only-way-to-go?p=2221733&viewfull=1#post2221733

Yes, I'm aware of YAL-1, and it's a toy compared to what you'd need in interplanetary conflicts at distances of millions of kilometers.

I'm a little confused.

1. Are you saying you can't focus, with a big mirror on the order of 100 to 1000 meters radius, onto a target at a great distance using UV or X-rays?

2. Are you saying you actually need that kind of beam power if you can get a small, tight beam at whatever distance you are at?

The whole idea is that if you are using a laser against an enemy vehicle in the same weight class, the enemy can shed just as much heat as you are sending. So you have to be able to focus the beam onto a small enough area to vaporize a hole in their systems. The vapor gets lost to space and so the enemy ship loses mass, and the functionality of whatever system the beam burned through. Burn a hole in the enemy power source or the enemy weapons or the enemy radiator junctions and you win.

If you are forced to spread the light over their whole hull, you don't win. They can shed as much heat as you are sending, because by definition they have radiators about the same size, and your lasers are less than 50% efficient. (they basically have to be, because of that dreaded law of physics, entropy. An in phase laser beam focused in a single direction has very low entropy compared to the chaotic sea of high energy particles resulting from a fission, fusion, or antimatter reaction that is your power generator. So you have to shed the difference as high entropy heat)

Your "petawatts of power" idea only works if the enemy is massively out-massed.

Edited September 30, 2015 by SomeGuy12

[Shpaget]

I'm saying that at interplanetary distances beam weapons (using technology we have now or in near future) are not feasible. There are too many issues for them to be an effective weapon that can be deployed on a spaceship.

1000m radius antenna? Come on. How do you turn that thing without it wobbling horribly out of shape?

Even if you could get a focused beam, pointing it accurately at a few million kilometers is going to be hard.