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NASA completes full-power tests of small, portable nuclear reactor

engadget.com

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Re: NASA completes full-power tests of small, portable nuclear reactor

#11

Post by cathhhhji »

syntaxing wrote: post #7

For those curious, this uses a nuclear reactor to power a Stirling engine.Stirling engines are a good choice because there is no mass transfer to create the work (i.e. no fuel needed, just heat). It only needs a temperature differential and sealed gas/liquid to work. I highly recommend to read more about Stirling engines since they are of one the most efficient form of work generation with just a temperature differen…

Stirling engines are not efficient. Using that heat to make steam to turn a turbine is much more efficient. But it would be harder to make that portable.

Re: NASA completes full-power tests of small, portable nuclear reactor

#12

Post by practice9 »

dukoid wrote: post #9
netzone wrote: post #4

What would the effects be of releasing nuclear waste in space? Could we sent up all of our nuclear waste, put a rocket on it and just let it disappear into the distance?

How about just sending it to the moon instead? Perhaps then we could use the moon as a giant space ship by blowing up the nuclear waste?

It's a fascinating idea from science fiction perspective, but moving the Moon anywhere will probably have devastating effects on the Earth's biosphere

Re: NASA completes full-power tests of small, portable nuclear reactor

#13

Post by dukoid »

Sir_Substance wrote: post #8

Conspicuously not mentioned: what kind of design the reactor uses. Thanks engadget, 10/10 reporting. Based on the wikipedia article, it looks like a passive decay heater attached to a bunch of sterling engines. Pretty much a souped up RTG that trades more energy output for having moving parts. Neat.

Wouldn't "passive decay" mean it's not based on fission -- but the article and video both mention fission...?

Re: NASA completes full-power tests of small, portable nuclear reactor

#14

Post by dukoid »

practice9 wrote: post #12
dukoid wrote: post #9

Earlier quoted context omitted.

How about just sending it to the moon instead? Perhaps then we could use the moon as a giant space ship by blowing up the nuclear waste?

It's a fascinating idea from science fiction perspective, but moving the Moon anywhere will probably have devastating effects on the Earth's biosphere

I think that's just short term thinking: When the sun expands into a red giant, the gas drag will slow down the moon. I think that means it will crash into the earth if it's not removed before.

Re: NASA completes full-power tests of small, portable nuclear reactor

#15

Post by telchar »

cathhhhji wrote: post #11
syntaxing wrote: post #7

For those curious, this uses a nuclear reactor to power a Stirling engine.Stirling engines are a good choice because there is no mass transfer to create the work (i.e. no fuel needed, just heat). It only needs a temperature differential and sealed gas/liquid to work. I highly recommend to read more about Stirling engines since they are of one the most efficient form of work generation with just a temperature differen…

Stirling engines are not efficient. Using that heat to make steam to turn a turbine is much more efficient. But it would be harder to make that portable.

Yes they are. An ideal stirling engine has the Carnot level efficiency, i.e. maximum theoretical efficiency for a heat engine.

https://blog.mide.com/thermodynamic-theory-of-the-ideal-stir...

Re: NASA completes full-power tests of small, portable nuclear reactor

#16

Post by Sir_Substance »

dukoid wrote: post #13
Sir_Substance wrote: post #8

Conspicuously not mentioned: what kind of design the reactor uses. Thanks engadget, 10/10 reporting. Based on the wikipedia article, it looks like a passive decay heater attached to a bunch of sterling engines. Pretty much a souped up RTG that trades more energy output for having moving parts. Neat.

Wouldn't "passive decay" mean it's not based on fission -- but the article and video both mention fission...?

Passive decay is still fission, it's just not artificially sped up fission :)

it's probably more complex than that. Is high speed natural decay of an artificially created or enriched heavy element natural or artificial? I'm not sure how that gets classified.

Re: NASA completes full-power tests of small, portable nuclear reactor

#17

Post by craftyguy »

dukoid wrote: post #14
practice9 wrote: post #12

Earlier quoted context omitted.

It's a fascinating idea from science fiction perspective, but moving the Moon anywhere will probably have devastating effects on the Earth's biosphere

I think that's just short term thinking: When the sun expands into a red giant, the gas drag will slow down the moon. I think that means it will crash into the earth if it's not removed before.

Regardless of whether or not what you say is likely to happen (I think not, but anyways), if humans can even last long enough to see the Sun as a red giant, we'll have larger problems on our hands. In any case, we'll likely have destroyed ourselves or evolved into something else by that time.

Re: NASA completes full-power tests of small, portable nuclear reactor

#18

Post by dukoid »

Sir_Substance wrote: post #16
dukoid wrote: post #13

Earlier quoted context omitted.

Wouldn't "passive decay" mean it's not based on fission -- but the article and video both mention fission...?

Passive decay is still fission, it's just not artificially sped up fission :) it's probably more complex than that. Is high speed natural decay of an artificially created or enriched heavy element natural or artificial? I'm not sure how that gets classified.

My bad, I had assumed fission was splitting atoms by adding neutrons, but actually fission is just the "splitting" part, so both cases are indeed fission....

Re: NASA completes full-power tests of small, portable nuclear reactor

#19

Post by dukoid »

practice9 wrote: post #12
dukoid wrote: post #9

Earlier quoted context omitted.

How about just sending it to the moon instead? Perhaps then we could use the moon as a giant space ship by blowing up the nuclear waste?

It's a fascinating idea from science fiction perspective, but moving the Moon anywhere will probably have devastating effects on the Earth's biosphere

p.s. The process is shown in this documentary: https://www.youtube.com/watch?v=HE06rNkxlks&feature=youtu.be...

Re: NASA completes full-power tests of small, portable nuclear reactor

#20

Post by killjoywashere »

craftyguy wrote: post #17
dukoid wrote: post #14

Earlier quoted context omitted.

I think that's just short term thinking: When the sun expands into a red giant, the gas drag will slow down the moon. I think that means it will crash into the earth if it's not removed before.

Regardless of whether or not what you say is likely to happen (I think not, but anyways), if humans can even last long enough to see the Sun as a red giant, we'll have larger problems on our hands. In any case, we'll likely have destroyed ourselves or evolved into something else by that time.

The Moon orbits the Sun, and is only mildly perturbed by the Earth. Gas drag would decay the Moon's orbit, but it's not at all clear to me it would crash into the Earth. It seems far more likely it would simply fall into the Sun.
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