China's manned space flight program.

[Urban Ranger]

But waste heat is just heat you can use because you don't have a sufficient gradient. This is mainly a problem on earth because it is generally somewhat warm. In space, though, you can easily set up a huge, huge gradient.

[Curiosity]

MikeH,

Let's ignore the Venus fly-by option; So our astronauts spend two 6-month stretches in zero-G and two years at one-third of a g. The two zero-g sections aren't a problem by themselves. We don't know exactly what effects will be caused by a third of a g, but it's reasonable to assume that wastage will be slower than zero g, and that a stable state, if it exits, will be at a lower level than in full g. Most of the possible outcomes should be within human tolerance; only if mars gravity has a minimal effect is there the possibility of a less-than-full recovery.
But the only way to find out is to put a couple of astronauts in one-third-g for two years. In which case, Mars seems like an excellent spot to test this...

Rogan,

Best solution according to what criteria? Employing lots of particle physicists, by any chance?
While IMO ion rockets and space fission reactors are certainly worthy of development, there's nothing like off-the-shelf technology for getting a job done.

For cooling, the only option is large radiator fins. Ask the russians how they managed it; IIRC they have two radarsats with fission reactors aboard.

skwalker,

In a normal nuclear reactor they do use vapourized coolant to power turbines, but not in most designs for space-based reactors. The mass of the turbines, cooling system etc. is considerable, and if you intend to launch the reactor into orbit then it's better to enlarge the size of the core and use a thermoelectric generator, even though you only get ~5% efficiency.

But this leads to a heck of a lot of heat which just has to be dumped by any means possible.

[Dinner]

You know we could just have he astronaights excerisze on resistance band machines and the problem would be solved.

[MikeH]

Originally posted by Curiosity
MikeH,

Let's ignore the Venus fly-by option; So our astronauts spend two 6-month stretches in zero-G and two years at one-third of a g. The two zero-g sections aren't a problem by themselves. We don't know exactly what effects will be caused by a third of a g, but it's reasonable to assume that wastage will be slower than zero g, and that a stable state, if it exits, will be at a lower level than in full g. Most of the possible outcomes should be within human tolerance; only if mars gravity has a minimal effect is there the possibility of a less-than-full recovery.
But the only way to find out is to put a couple of astronauts in one-third-g for two years. In which case, Mars seems like an excellent spot to test this...

Fine. There's no way I'd risk it though.

[Curiosity]

Oerdin,

They already exercise on almost every device imaginable, including bungee-cord treadmills and the like, for up to 6 hours a day. The problem is very strange; they apply far vastly more overall force to their muscles and bones than someone who is bedridden, but loose muscle and bone at a much higher rate. There seems to be something special about how the body reacts to constant, low level compression. (Which is why I suspect that Mars gravity will not be too much worse than full-g, but that's just conjecture.)

MikeH,

OK - one less competitor for the seat.

[Kuciwalker]

Originally posted by Curiosity
skwalker,

In a normal nuclear reactor they do use vapourized coolant to power turbines, but not in most designs for space-based reactors. The mass of the turbines, cooling system etc. is considerable, and if you intend to launch the reactor into orbit then it's better to enlarge the size of the core and use a thermoelectric generator, even though you only get ~5% efficiency.

But this leads to a heck of a lot of heat which just has to be dumped by any means possible.

I was talking about in submarines

[Rogan Josh]

KH: Presumably the subs can't cool like that if hey are running on stealth because you would see the heat signature. They must somehow 'store' the heat. Anyone know how?

Curiosity: This was a talk from NASA, so there were no particle physicists involved.

[Urban Ranger]

AFAIK, though, sub detection is mainly via sonar, not heat sensing.

[Chemical Ollie]

TCO would probably know, whenever he's sober and back home from the hurricane.

[Joseph]

Originally posted by Urban Ranger
AFAIK, though, sub detection is mainly via sonar, not heat sensing.

You would be surprise if you knew how we find Subs.

[Kuciwalker]

Originally posted by Rogan Josh
KH: Presumably the subs can't cool like that if hey are running on stealth because you would see the heat signature. They must somehow 'store' the heat. Anyone know how?

Curiosity: This was a talk from NASA, so there were no particle physicists involved.

Perhaps something with a high whatsitcalled (water has 1.0; it is volume/mass). Use it as a heat sink. Eventually you'll have to expell it or transfer the heat outside, of course.