Knew it was to good to be true.
Back to step 1!

But you can't hide your heat and radiation signature; the heat will (excepting any major discovery that can violate the Laws of Thermodynamics) have to go somewhere, and when it does, everyone can see you.

No, if you go into geostationary orbit in the other direction you're still going to make the trip all the way around the planet in 24 hours. The only difference is that the surface will rotate in the other direction from you.

There are only two ways I can think of where you can stay motionless relative to a planet: Either using a Solar Lagrange point, in which case you are way, way too far away from the planet hide behind it, or not actually being in orbit (that is, being above a planet with null horizontal velocity), meaning you have to constantly apply thrust to counter the gravity pulling you down. In either case, that still assumes you're at that position to begin with and the enemy isn't looking from multiple directions, otherwise you are toast.

Vacuum is a good insulator from convection, not from radiation, which is why you're using that method to get rid of heat in the first place. So the outer hull will absorb the radiation from the inner hull and will radiate it into outer space just the same.

Wouldn't that only work if you have this metamaterial right between your exhaust and the target? I don't think that's very practical, even assuming it is possible. Of course, that will still only relocate the problem somewhere else...

Ah, of course, hence why we can pick up the radiation from pulsars, I didn't think of that. I had a hunch that there would be hard science reasons why it wouldn't work, hence why I brought you guys in. :03:

Exactly, the planet rotates and your position over a piece of it moves but your position on, say the side facing away from the sun, will not change. Hence to anyone looking from that direction they will not see a ship parked on the opposite side.

There has to be another name for it, though. "Geostationary" literally means "staying in the same place above the planet".
http://en.wikipedia.org/wiki/Geostationary_orbit

That's incorrect. A geostationary orbit turns with the planet, thus experiencing the same day/night shift. Heading in the opposite direction at the same speed you will still orbit the Earth once every 24 hours, and experience the same shift.

To remain on the day or night side of the planet you would have to be standing still, not orbiting at all.

'Retrograde geosynchronous orbit' is the most accurate description I can think of. I don't know if this sort of orbit has a proper name, or, indeed, if anybody actually uses it enough to justify one...

I see what you mean. So if I want to stay on the night side of a planet I guess all I have to do is counteract the pull of gravity. Since centrifugal force won't help as you point out then you'd have to maintain a constant thrust against it which would also be hidden by the planet.

Why would you want to be on the night side? So that the incredible heat of you spacecraft is even more obvious in the shadow of the planet?

A bunch of us (traveller rpg geeks who happened to be astonmers) did the math decades ago. A small spacecraft would be near "naked eye" magnitude in the IR at the distance of earth to moon. (a traveller scout ship for traveller geeks). That's just waste heat from keeping the inside a shirtsleeves environment, computers, life support, etc.

I only said the night side to indicate that the craft would be hidden behind the planet from an observer located somewhere along a line running from the planet to the sun.

Bottom line I guess is how could a spacecraft keep the bulk of a planet or moon between them and an observer?

That's as good a name as any, I guess. It gets the point across.

Well, since the whole idea of a geosynchronous orbit is to stay in the same spot above the Earth, I'm not sure what would be the point of picking that exact altitude and speed to go in any other direction.

I would guess that far enough from the planet the amount of thrust required would be minimal. The biggest problem I can see is not staying in one place, but knowing what the guy you're hiding from is doing. You can't see him either, so you can't know exactly when he's going to pop into view, or even from which side.

It reminds me of a book I've just been reading on sailing ship combat. You can see the enemy coming hours before you're close enough to fight, and if you should go behind an island you can't tell what he's doing any more than he can tell what you're doing.

Captain Isaac Hull of USS Constution found a way to make that work for him while being chased by a British squadron in July 1812. After more than a day of towing the ships in a dead calm the wind picked up. As Constitution approached a light squall with a four-mile lead, Hull had his crew shorten sail as if preparing for a major storm. Seeing this from a distance, the British did the same. As soon as Constitution was on the other side of the squall, not able to see the enemy and knowing they couldn't see him, Hull put on full sail and ran away while the British ships were still on short sail, waiting for the "storm" to arrive.

Hiding behind a planet, or alternate ideas like radiating waste heat directionally require knowing what the enemy is doing so you can point away from them. Holding still above a planet makes you visible to everywhere on the planet as it rotates under you. Another spacecraft will be in orbit and will move to your side. If far away your craft must be in very low or it to be masked, might as well land.

Reading this thread, I have the idea that space battles are going to be more a game of cat and mouse than the battle for the Atlantic :hmmm:

And I can't get the final battle in Wrath of Khan out of my head

How could you come to that conclusion? There is no cat and mouse. All are easily visible to passive sensors. No hiding.

I would hazard to guess that anyone with the ability to travel between the stars will also know how to mask their heat signature.