[spingsprong]

Please be true, please be true!

How big is a two megawatt nuclear power source anyway? A quick search showed nuclear power plants are in the hundreds to low thousands of megawatt range, and RTGs are in the tens to hundreds of watt range. I have no idea what something that lies between those two would be.

[runj__]

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

Toshiba 4S gives 10 MW.

"a 50 MW version [will be] available in the future"

[tgb]

Wikipedia gives the generator of Loss Angeles class nuclear submarines to be 26 MW [1]. I don't know whether you can make them as successful in space without the access to ambient water.

[1]http://en.wikipedia.org/wiki/Los_Angeles_class_submarine

[madaxe_again]

The principle problem to be overcome with this tech is going to be cooling - both for the power source and for the drive. It's going to require radiators the with a stonkingly huge area and Peltier shunts, unless we come up with a cunning means of dumping excess heat - potentially turning it into more energy to drive with, even, using the seebeck effect.

[runj__]

Isn't space pretty cool?

[damoncali]

As cool as space can be, it can also be incredibly hot. It's not uncommon to see huge temperature variations on the same object based on whether or not the surface in question is pointing toward or away from the sun. In any case, as others have said, there is no conduction or convection in space - only radiation, which needs a little help some times.

For an example, when I worked on the Hubble, a thermal short was discovered that would severely limit the life of one of the cameras, which have to be very cold to operate. In order to counteract that, a pretty complex cooling system was built to counteract the effect. It consisted of a couple of large metal boxes (a couple hundred pounds each, if I recall) attached to a couple of huge radiator panels. (About 3'x10' each, if memory serves). The whole thing took over a year to build and took a lot of care to launch and install.

[madaxe_again]

It's damnably cool!

And extremely hot (100C + in near-earth orbit) in the sun, and -273 in the shade - with nothing to conduct heat away - meaning that you can only emit heat as EM radiation (photons).

[crawshaw]

Space is mostly empty. There's nothing much to dissipate heat into.

Cooling is always a problem in space.

[noselasd]

In a sense, yes. But space has no medium to convey heat so you can't get rid of it by convection or diffusion. Getting rid of heat in space is hard and a big issue for spacecrafts.

[Crito]

> "I have no idea what something that lies between those two would be."

One example is the small nuclear reactors that have been used in orbit already: http://en.wikipedia.org/wiki/TOPAZ_nuclear_reactor

[robryk]

RORSAT[1] were Soviet satellites that carried radar and were powered by small nuclear reactors. The reactors provided between 2 and 6 kW of power.

[1] https://en.wikipedia.org/wiki/RORSAT