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U.S. tests nuclear power system to sustain astronauts on Mars

reuters.com

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Re: U.S. tests nuclear power system to sustain astronauts on Mars

#111

Post by Balgair »

imglorp wrote: post #79
ifdefdebug wrote: post #70

I 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 find it encouraging the private sector is filling the gap. Musk's vision is clear if you assemble all the pieces his companies have built on Mars: solar and battery power, tunnel boring for both shelter, water, and air (which could imply return fuel he can do O2+H2). Solar might not be the most efficient for Mars, but he can bring tons of it without messing with nuclear politics and PR. Note also the Boring Company…

I agree that Elon's companies do have suspiciously many things to do with Mars habitats.

However, the reliability of the tech we have is severely lacking. To get off Mars, you are going to need a rocket. So then you need to land a rocket on Mars.

Fully fueled.

You also need a backup. We simply do not have that kind of reliability yet, and I don't think we're even close.

Fine, we'll fuel it on Mars. That means a remote robotic mining-facility and rocket-fuel-plant, in nearly no atmosphere, in cold temps, up to 16 light-minutes away (at worst, true). So it's gotta be totally autonomous. And not explode while people are in transit. And it's likely going be on a pole, so that you have easy access to fuelstuffs. Which is boring as all heck compared to Valles Marianas (not a big deal, admittedly)

If we have that tech on Mars, then the economy of Earth is going to look a LOT different. Self-driving cars aren't the half of it.

Mars, in a nutshell, is VERY Hard.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#112

Post by debt »

njarboe wrote: post #4
baron816 wrote: post #2

What 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…

It's an extremely toxic, dangerous material overall. The fear is well-founded in a geopolitically chaotic, variable world.

Not to mention, in this case specifically, they're going to strap it to a rocket and send it to Mars.

Gonna be hard to sell people on the safety of the mission if we're potentially spewing nuclear material over thousands of square miles in the worst case scenario.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#113

Post by gene-h »

superkuh wrote: post #37

As 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.

They already completed the equivalent thermal power tests last year[0], and you most certainly don't need to do electrical tests at the Nevada Nuclear Test Site. How much progress they've actually made at this point is not clear from the article, but slides from a presentation they posted yesterday detail what they plan to test[1]/maybe already tested. They need to test the individual reactor components to measure reactivity, then they need to put the power generator on and see what happens when it's just critical, but not producing any heat, then they bring thermal power up to 4 kilowatts, then they do a full power test.

All of these tests involve fissile materials, so to quote Red Alert, "Gentlemen, it's a nuclear device."

[0]https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201700... [1]https://www.nasa.gov/sites/default/files/atoms/files/kilopow...

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#114

Post by adventured »

ifdefdebug wrote: post #70

I 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

The entire subject of what you're talking about, is a non-issue. Five years ago it was barely a legitimate concern. It has no legitimacy at this point. The problem, isn't a problem, it's solved.

See: Boeing and SpaceX. Add 8 to 12 months. Done.

And just like that, NASA has access to superior human launch capabilities versus Russia and China. And that's before Blue Origin builds out its New Glenn monster. Russia will fall very far behind over the next five years, only China will be able to afford to keep up over time.

SpaceX already passed Russia in launches this year. That's going to get a lot worse.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#115

Post by nine_k »

7952 wrote: post #52
icelancer wrote: post #45

Earlier quoted context omitted.

There is essentially no actual ecological or serious fear about these devices. The weapons ban was meant to help avoid nuclear exchange between nations; there's very little scientific data that shows there's added cost or risk of thousands of reactors falling to Earth and causing radiation poisoning. Nuclear is exceptionally safe and all the recent accidents (and ones in the past, really) are all due to human stupidi…

> It's a human issue. Which could be applied to any challenge that humanity face. This basic human weaknesses is always what holds us back in any endeavour. It is dangerous to just dismiss it as "arbitary". You have to deal with these issues if you want to make big projects achieve their objectives.

It's fine to put yourself to a danger willingly. It's not fine to put your neighbors to a danger without their consent.

The problem with many pieces of large-scale tech is potential harmful side effects on unrelated people who did not ask for that.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#116

Post by jerven »

scrollaway wrote: post #62
jonathanstrange wrote: post #59

Earlier quoted context omitted.

I completely agree and don't think coal is better than nuclear power at all. Reduction of energy waste, renewable energy sources and nuclear fushion are the obvious way to go, but it may make sense to temporarily accompany them with nuclear power.

Sure, I didn't mean to imply that. I just meant that whatever long term damages are done need to be put on a timescale that actually helps us compare alternatives. If hundreds of billions of lives are saved in the time it takes for nuclear to do real damage, maybe that's just worth it.

It is also worth to estimate how quickly nuclear production can scale up and deplace coal. I personally think wind and solar can scale up much faster economically and socially and more easily deplace coal and gas than nuclear could in the best case.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#117

Post by nine_k »

Kutta wrote: post #61
lmilcin wrote: post #54

Earlier quoted context omitted.

Hi, just to point out a hole in your reasoning, if these reactors are so safe then why even a small portion of the radioactivity escaping the containment shell can cause such a big disaster like Fukushima or Chernobyl? Now, I understand there are differences in size and the level of radioactivity used (they won't be driven as close to prompt criticality as the power reactors) and they may be designed to be less relia…

> small portion of the radioactivity escaping the containment shell The Chernobyl reactor was very unsafe by modern standards, it did not have a containment vessel and tens of tons of reactor material was blown into the air, not a small amount.

To actually blow the Chernobyl reactor, the personnel explicitly disabled quite a few safety systems that otherwise would not allow for a runaway reaction which led to a mighty (thermal and chemical) explosion.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#118

Post by gene-h »

SigmundA wrote: post #76
superkuh wrote: post #37

As 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…

Fission isn't necessarily easy. One problem is that the reactor behavior changes when you add the generators to the reactor. These components can reflect neutrons back to the reactor, which changes how much power the reactor produces. That being said, 'easy' or 'hard' are really not the best way to think about flight ready hardware. Actually making hardware and guaranteeing that it works involves so much more than just understanding nuclear fission. We can come up with a design on paper, but without testing we don't have assurance that it works.

Simply putting the reactor together and testing it are more complicated than they seem. This is because of three things matter can reflect neutrons back, humans are harmed by radiation, and humans are the ones assembling/transporting/testing the reactor. We have to be careful putting the reactor together so that it doesn't spew neutrons and harm the humans assembling it. We need to develop ways to transport the reactor so that it doesn't spew neutrons. When we test the reactor, we have to set up our test so that humans won't have to get anywhere close to the reactor for a couple of months. There's also other issues like training people to do these things and NASA cooperating with the DOE to do the testing. These are 'simple' things, but they still need to be done.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#119

Post by baybal2 »

SigmundA wrote: post #104
baybal2 wrote: post #86

Earlier quoted context omitted.

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…

1. Work function - how much energy is needed to let an electron move from one material to another.

2. Quantum tunneling - electrons will tunnel back to lower charge density region, and preventing them from doing so is effectively impractical with modern day tech.

If they were any actual thermocouples with 20% efficiency, they would've nuked piston engines long time ago.

Re: U.S. tests nuclear power system to sustain astronauts on Mars

#120

Post by gene-h »

ourmandave wrote: post #69

Unanswered in article: How long does the power unit lasts until you have to replace the paper-towel-roll-sized U-235 core? Where are they going to put the old ones? What's the plug interface? Can I charge my iPhone? What about my electric razor? Are they going to test burying one in red sand for 15+ years and see if it can be dug up to phone home in an emergency?

>How long does the power unit lasts until you have to replace the paper-towel-roll-sized U-235 core? It's not a completed design, but based on their proposed design[0] 20 or more years. The old reactor core is going to remain in the spacecraft, which will probably be at the very least hundreds of thousands of kilometers from Earth. In short, you don't replace the core, you would replace the entire reactor, which is doable because the reactor isn't very big. >plug interface whatever you want it to be, it's not a complete design >Can I charge my iPhone? What about my electric razor? The current tests should enable reactors with electrical power outputs ranging from 500 watt to 10 kilowatts. An iphone probably has a power consumption of around 1 watt max, so you should probably be able to run between 500 and 10,000 iphones. Electric razors have a max power draw of 20 watts, so it should be possible to run between 25 and 500.

>Are they going to test burying one in red sand for 15+ years and see if it can be dug up to phone home in an emergency? Any such tests would be purely ad-hoc. That being said, if you don't have enough power to phone home([0]https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201700... [1]https://www.nasa.gov/sites/default/files/atoms/files/kilopow... [2]https://www.daftlogic.com/information-appliance-power-consum...

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