Question by Aquariumnerd Guy: i read some interesting article about nuclear rocket engines, I was wondering?
they say the technology is being held back because of the high mass of the reactor, and that the power per unit mass of the reactor could be increased if we had materials that could tolerate a higher temperature, but nothing can. So what is stopping them producing a reactor that can stay in one piece till the edge of space then detach from the craft and go into meltdown?
I thought basic models had already been developed years back?
Best answer:
Answer by Vitki
so….you want the reactor in meltdown to fall back to earth where it might effectively eliminate the population? A Brilliant idea for genocide! lets get right to it!
even if you go to the edge of the atmosphere, the gravitational pull of the planet reaches far beyond that. if it didn’t we would have lost the moon about 4 billion years ago.
I assume here you’re talking about a fission reactor. a Fusion reactor (also called a breeder reactor because instead of nuclear waste, it generates more nuclear fuel) would probably work better for a propulsion source, but nobody’s managed to make a fusion reactor work yet.
the most viable engine (currently) for deep space travel is the VASIMR engine. the only drawback is that it takes a LOT of fuel.
Currently, Materials sciences are making huge breakthroughs every day–which reduces the potential mass (and price) of anything we consider sending up into space. but the real block isn’t the mass, its the price. it costs an estimated ,000 a pound to send anything up there. Where should the money come from? do you want to spend that much of your own money for something with a high risk of failure and a low probability of financial return?
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One Response
1] Vitki is full of sh!t when he says a breeder reactor is doing fusion reactions. THey do fission. Fusion is like H bombs and the sun, putting small nuclei, like H or D together, such as making He.
2] Rockets are rated by ‘specific impulse’, http://en.wikipedia.org/wiki/Specific_impulse
Specific impulse is limited by the exhaust velocity of the rocket. That depends on the temperature of the exhaust.
Any rocket has a pressure chamber where the gas is produced already hot [such as by combustion] and/or comes in cold and is heated [such as in a nuke rocket]. THat pressure chamber has to be light enough but strong enough at temperature… A tricky bit of engineering.
THe rocket has to have high pressure to get high exhaust velocity.
Meltdown is inherently unsafe to be around. Besides which, for decent economics you want the engine to be reusable.