Perfect cloaking device? No problem, just call your resident wizard.

He casts a spell and your perfectly cloaked

It's the answer to all of the sci-fi mysteries: A wizard did it!

Well, despite the engine type names, Aurora Engines seem to be more of a Warp field.

Andrew:  Thermodynamics says that any attempt at "directed heat discharge" is going to produce more (undirected) waste heat.  The second law can get really annoying at times.

Holding shrouds in place faces the problem that the shrouds themselves will heat up and produce a thermal signature - though, true, perhaps a more diffuse one if they're really big.  (More diffuse, but then also larger in area - somewhat of a wash.)

Not quite.  The second law is a global statement: the entropy of the universe is monotonically increasing.  You can cheat locally by consuming "free energy" (which is a technical term in thermodynamics - it basically means "energy which is available to do work without violating the 2nd law").  This is what an air conditioner does - it makes the coolant colder and the radiator fins warmer at the cost of burning fuel/consuming electricity which results in the warm radiator fins needing to also absorb the waste heat from the burning/consuming and therefor becoming even warmer.

The way this applies to a "directed heat discharge" is to imagine having a spaceship with a really good refrigerator, a really good battery to run it, and a refrigerated spherical shell with a hole punched in it (to radiate the heat).  You probably also want the interior of the shell to have a high reflectance/low absorbance so that not much interior heat leaks into it (you could also insulate it really really well) which cuts down on the work the refrigerator has to do.  You use the refrigerator to keep the shell cooled to 3 degrees kelvin (background temp).  This makes the ship (inside the shell) heat up more and more - as it heats up, it glows and will radiate thermal energy.  Most of this energy will be reflected by the walls of the shell, except where you've punched the hole in it, where it escapes to space.  The problem with this technique is that you lose radiation efficiency as you make the hole smaller/more directed.  One way to to get around this would be to stick a (refrigerated) parabolic "mirror" outside the shell, with a radiator at the focal point of the mirror, and with the mirror having high reflectivity in the vicinity of the peak of the black body spectrum for the radiators operating temperature.  This would allow you to get (almost) 4pi solid angle of radiation from your radiator, while directing the radiation into a "beam" that the bad guys would need to be lucky to intercept.

The upshot of this is that, as long as you have a free energy source (i.e. fuel) you can selectively refrigerate parts of your ship so that they don't show up like a spotlight on the bad guys' thermal sensors, unless the bad guys happen to be looking "up your kilt".  This does not violate the 2nd law in the same way that the refrigerator in your kitchen doesn't.

John

I think there could be several ways to block thermal scans.

1) Umbrella effect: if you have a wall of perfect coolness in front of you and all the heat behind, then the thermal dectors would just hit your "invisible wall" and not be able to detect the heat behind you. Obviously something would need to be done about heat trails etc. but assuming the enemy thermal scanners aren't omnipotent, any kind of electronic subterfuge could be used. Look at stealth bombers vs. thermal scanners.

2) Super-coolant: true the heat has to go somewhere, but what if it is contained within the ship itself? the exteriors would need to be super-cooled but anything inside could be hot as hell as long as the exterior is the same temp as surrounding space and doesn't permit the thermal scnaners from penetrating

3) Space can't always be a consistent temperature, can it? With stars and planets, and comets, and ships, there have to be residual heat signatures everywhere, right? Masking teh ship as "background thermal energy" works, right? Isn't that how cloaking works right now, by significantly reducing the signature of the ship?

Isn't that how "stealth" planes work now? By being built to reduce their image on radar/sonar etc. so they're indistinguishable from background noise?

I´d like to quote the Atomic Rocket site for re. this discussion


So you know, university Physics* is essentially three years of this discussion among like-minded enthusiasts.

Done with supercomputers, access to the textbook collections of five continents and thirty languages.

On four hours sleep a night.

With no sex.

You're not going to find the loophole these guys missed. *Whis simply says: There is no stealth in space!

"The Andrew:  Thermodynamics says that any attempt at "directed heat discharge" is going to produce more (undirected) waste heat.  The second law can get really annoying at times.

Holding shrouds in place faces the problem that the shrouds themselves will heat up and produce a thermal signature - though, true, perhaps a more diffuse one if they're really big.  (More diffuse, but then also larger in area - somewhat of a wash.)
.

It has been a long time since I studied thermodynamics , but by careful design of your material structure I am certain you can greatly increase thermal radiation from part of an object without having to expend any energy which would leaf to more waste heat.  
A good start to a system would be to have high efficieny radiators on the various surfaces of the ship , linked to a central heat sink via thermal superconducting links(I beleive you can manage thermal supeconductors with some variations of industrial diamond ). You then selectively select which radiators are active as you need to hide you emissions from some aspect of your vessel. Obviously there is going to be a limit to how much you can radiate from each aspect and it likely that you are only going to delay having to dump heat from all aspects.
The Drive shrouds are I agree also less than perfect you can pick a fairly thermally reflective material but you are still going to get warming OTH I don't actually consider that given the mechanics Aurore ships can actually be using reaction drives so you may not have a drive plume to worry about(the names suggest they do but the behaviour of ships movement proves they are not reaction drives) given that the heat signature from drives probably reflects more the heat generated by the power reactors of the drive (probably means the extra powerplants for beam weapons should increase a ships thermal sig, but as that would only be while firing weapons it is probably more trouble than its worth)

"We don't even have weaponized versions of tractor and repulsor beams, for that matter, though perhaps we should.  Shlock Mercenary style "gravy guns" would make an interesting addition to the beam weapon stockpile.

No problem with that would actually be similar to the Starfire Force beams or imploder lances from the vorkosigan books

I think there could be several ways to block thermal scans.

1) Umbrella effect: if you have a wall of perfect coolness in front of you and all the heat behind, then the thermal dectors would just hit your "invisible wall" and not be able to detect the heat behind you. Obviously something would need to be done about heat trails etc. but assuming the enemy thermal scanners aren't omnipotent, any kind of electronic subterfuge could be used. Look at stealth bombers vs. thermal scanners.

2) Super-coolant: true the heat has to go somewhere, but what if it is contained within the ship itself? the exteriors would need to be super-cooled but anything inside could be hot as hell as long as the exterior is the same temp as surrounding space and doesn't permit the thermal scnaners from penetrating

3) Space can't always be a consistent temperature, can it? With stars and planets, and comets, and ships, there have to be residual heat signatures everywhere, right? Masking teh ship as "background thermal energy" works, right? Isn't that how cloaking works right now, by significantly reducing the signature of the ship?

Isn't that how "stealth" planes work now? By being built to reduce their image on radar/sonar etc. so they're indistinguishable from background noise?

Cloaking devices
http://en.wikipedia.org/wiki/Cloaking_device

OK, granted that further progress with metamaterials could make a ship invisible to radar and maybe even visible light.

But you're not going to be able to mask a ship's thermal emissions forever;  the heat has to go *somewhere*.  A heat sink will work for a while, but then it's done.

And given that "EM" sensors are really gravitic... good luck imagining a metamaterial which could shield against *that*.

I do agree with you, as I said above, that there's no reason to think neutrinos would work in the way described.

Pseudo science rubbish, similar to the book

You mean like tractor beams and cloaking devices?

That said, I can't think of any reason why a stream of neutrinos would particularly affect organics.