Earlier quoted context omitted.
Tectonic activety I suspect.
Tharsis region?
When was anything there last active?
U.S. tests nuclear power system to sustain astronauts on Mars
101–110 of 138 posts
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#102Re: U.S. tests nuclear power system to sustain astronauts on Mars
#103I am not sure this is a good idea. Nuclear reactor is an easy way out of a problem that has alternative solutions. Restriction on using nuclear power for previous missions did a lot of good in terms of researching and perfecting the alternatives (solar arrays). Restricting the use of nuclear power does not prevent missions, it only adds to the cost of the mission, which is not really a technical problem. Maybe launch…
What power source do you propose for a long-duration human mission to Mars, if not nuclear? Solar won’t work, given the loss of output during a dust storm.
If I were on my way to Mars I wouldn't go without nuclear power. It is too far away to have an Amazon drone drop off a fresh batch of batteries or solar panels.
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#104Earlier quoted context omitted.
From my understanding the fission part is "easy", the hard part is taking the heat and converting to electricity efficiently and reliably. The Mars Curiosity rover among other probes use a thermocouple based generators to create electricity from the fission heat[1]. Extremely robust , no moving parts, but extremely inefficient just a few percent converted to electricity the rest to heat. The heat is very useful on ma…
There are fundamental physical limits of quantum nature to Seebeck effect based thermocouple efficiency. The maximum what you can get can't be higher than the hypothetical ideal quantum diode made from a material pair. There are much more down to earth alternatives that beat both stirlings and thermocouples on reliability and specific power density: thermionic converters, thermoaccoustic generators, AMTEC converters,…
Can you point me to the physical limit?
"Thermoelectric efficiency depends on the figure of merit, ZT. There is no theoretical upper limit to ZT, and as ZT approaches infinity, the thermoelectric efficiency approaches the Carnot limit. However, no known thermoelectrics have a ZT>3."[1]
There seem to be some in promising materials with a ZT of 2.2[2] which is around 20% similar to a solar cell. It seems again if more R&D where applied we might be able to make that cheap and practical.
1. https://en.wikipedia.org/wiki/Thermoelectric_materials#Devic...
2. https://newatlas.com/most-efficient-thermoelectric-material/...
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#105As far as I understand it they are pumping the equivalent thermal energy as an actual operating core would produce into the reactor casing and assembly using a specially designed electrical insert that uses external power. This isn't a fission test. It's a mechanical engineering test. Still cool.
From my understanding the fission part is "easy", the hard part is taking the heat and converting to electricity efficiently and reliably. The Mars Curiosity rover among other probes use a thermocouple based generators to create electricity from the fission heat[1]. Extremely robust , no moving parts, but extremely inefficient just a few percent converted to electricity the rest to heat. The heat is very useful on ma…
The thermoelectric generators with Pu238 don't use fission. The energy is released through alpha-decay.
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#106"Testing on components of the system, dubbed KRUSTY... " Named after Krusty the Clown?
KRUSTY stands for "Kilopower Reactor Using Stirling TechnologY".
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#107This thread is a great example of why I love HN. I clicked on Comments expecting to see a bunch of "nuclear = devils energy" posts, but what I found was reasoned discussion weighing the real pros and cons of this particular use case.
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#108Earlier quoted context omitted.
Plutonium isn't toxic, not any more than any other heavy metal.
It is radiotoxic
Nope, it is not. Not anymore than the straight radiation you would get from it.
When you talk of radiatoxicity what is usually meant is the hot particle theory which says that a bit of radioactive material lodged in one place is more likely to cause cancer, because the radiation given off repeatedly hits the same tissue. It turns out that in cohort studies done this is not true. Specifically people who have inhaled plutonium, an inadvisable thing to do, actually have lower rates of lung cancer.
Pu-238 has some radioactivity, although not as much as many fission products. Radioactivity is bad. But the fear over plutonium toxicity is actually overblown beyond the baseline radioactive dose it provides.
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#109What happens if the launch rocket fails? That’s been the main concern of sending nuclear reactors into space thus far, right? Has this been addressed here?
It is too bad that most people are so afraid of anything nuclear. I hate to say it, but maybe people working on nuclear power need to change the name. Isotopic power would have pretty bland associations. Uranium 235 is a very low level radioactive metal. Even if the rocket blew up, the isotopic fuel would remain intact (that is, not vaporized into breathable particles). The radioactivity from a Uranium 235 isotopic r…
I mean, there is a bit of precedence for the fear. It's not that we can't deal with the fission, it's that we can't have really really smart people on deck at all times. The consequences of big failures are pretty bad and pretty newsworthy.
Re: U.S. tests nuclear power system to sustain astronauts on Mars
#110I find it frustrating NASA talking about putting people on Mars but if you look at reality, it can't even put astronauts in the orbit anymore. What about solving that problem first, and when it's done, then we can dream about Mars... Or are we going to outsource such mundane tasks like manned orbital space flight to the Russians and Chinese forever, while we are proudly preparing the colonization of Mars? /s
I think outsourcing is precisely what we're doing; we're good at that.
Spaceflight is easy, creating a nuclear battery might be easy too, maybe even something we can outsource, but it's the one thing we definitely do not want other countries working on.