"There is no stealth in space." Whenever hard science fiction is mentioned on an RPG forum, this baby is trotted out. Why? Heat. All work produces waste energy in the form of heat. Despite the bitter cold of space, the big problem of spacecraft is radiating waste heat, not freezing. So what's the problem? Just rig up a big ol' radiator, a heat sink, and pump away! Not a problem at all - unless you don't want to be seen, that is. That big ol' radiator stands out like a beacon against the cold emptiness of space. Let's leave that for a moment, and jump to a new subject - they're related, I promise!
Zero-Point Energy is the McGuffin of SF - infinite energy all around us, free for the taking! Yay! Free beer! The zero-point is the ground state of the universe - here's wikipedia's take - which basically says the zero point, the lowest energy state you can go, is full of energy. Compared with this universal ground state, the energy demands of even a space ship are trivial. Much SF has been written about extracting this energy in some way for useful purposes.
Unfortunately, extracting this energy is the problem. There doesn't seem to be any way to extract this energy, what with the laws of conservation of energy, and besides, using it would eventually mean taking the universe down a peg energy-wise - not necessarily a good idea. So how could you use this without extracting energy?
How about pumping waste heat into it?
That violates no physical laws. It's useful, and it's very appealing. A ship equipped with a zero-point pump could go stealth! I would expect the technology is not cheap, so let's assume it is mainly a military thing. Ordinary civilian ships wouldn't need it anyway, as they aren't stealthy in other ways - radar, for example. A big ol' radiator would work just fine.
So, in StarCluster, there is stealth in space. Take that, nay-sayers!