U.S. tests nuclear power system to sustain astronauts on Mars
reuters.com
reuters.com
This isn't a fission test. It's a mechanical engineering test. Still cool.
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 mars though due to the low temps, kinda like your combustion engine in your car, the waste heat can be used to provide useful heating, but still most needs to be rejected and it only puts out about 100 watts of electricity.
This new one looks to be striling engine based which means its going to have much better efficiency since it is a more standard heat engine with moving parts, prob 20-40%. Hence the higher output. However that comes with much more complexity and things to go wrong over long term use.
I still wonder if there is much more efficiency to be had from thermocouple's if the research effort was put into it, it would be similar to solar cell improvements over the last few decades. You just don't hear about thermocouple R&D and if it where improved to say a typical solar cell efficiency of 18-20% it would open all sorts of doors.
1. https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
"Thermonuclear" usually refers to the sorts of fusion reactions found in stars and modern nuclear warheads.
[1]: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
This reactor says it uses U-235 which would be full fission similar to the US SNAP-10A[2] or Russian BES-5 RTG[3]
So yes the fission part is more complicated than a P-238 alpha decay RTG. Perhaps I mischaracterized the R&D complexity on the reactor portion, although it has been done before.
1. https://physics.stackexchange.com/questions/35303/alpha-deca...
When writing the answer, I didn't even consider, that those reactors need to be fast reactors. In retrospect it is obvious, but makes controlling the power even harder.
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, radiophotovoltaic (works only in 0g)
"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/...
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.
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.
Those probes are absolutely not using fission. Radioactive decay is not the same thing.
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...
https://beyondnerva.wordpress.com/
See also
https://github.com/briligg/moonwards/wiki/Nuclear-Reactors--...
Edit: even on a round trip it wouldn't be a big deal, the reactor can just be jettisoned before re-entering Earth's gravity well. You just can't have a fission reactor with spent fuel anywhere near Earth orbit. Space reactors in general are pretty interesting, because the design criteria are so different from terrestrial power reactors.
I think if there’s one thing to be learned from previous missions, it’s that nothing will „just work“. If the ejection mechanism is damaged, or the spacecraft is hit by some object and rendered useless shortly before ejection, then the radioactive payload will make it to Earth. I think a roundtrip would be dangerous, and the core should be left at Mars.
Polluting the new homeland from the start, eh?
More seriously, we can afford to have a small amount of nuclear waste there, but we need to plan for it better than we have previously. First, document where it is and what it contains. Second, I don't know.
The correct response is reprocessing. Most of the "waste" generated by power reactors is actually still usable as fuel. It also eliminates the really long-lived stuff, so that the small amount of leftover waste only has to be kept stored for a much more manageable 500-1000 years.
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 reactor comes after the reactor has been running for some period of time (from byproducts of the nuclear reaction), not the original fuel itself.
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.
Renaming things with bad public images is a popular trick.
Windscale > Sellafield
Blackwater > Xe Services > Academi
Philip Morris > Altria
原子力(atomic, using atoms)+発電所(power plant) is the common term
eg 福島(Fukushima)第一(No. 1)原子力(nuclear)発電所(power plant)
I am not sure about the readings of the first two kanji (atomic) so I used generic ones heehe.
Thanks in advance.
原子 genshi means atom. 力 means power (strength). Stick them together and it means using the power of the atom.
Japan has completely shut down all operations of Nuclear Plants since 2011. https://en.wikipedia.org/wiki/Nuclear_power_in_Japan
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.
https://listverse.com/2012/01/20/top-10-space-age-radiation-...
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
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 TBM diameter is less than the BFS. Don't be surprised if a TBM one of the first payloads.
https://en.wikipedia.org/wiki/SpaceX_Mars_transportation_inf...
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.
NASA can’t do everything themselves, so why not let Russia launch the rockets while the US and other countries focus on other parts of the mission?
But this isn’t really a NASA problem, this is a US government funding problem right? I can’t imagine how anyone can put people in space without the budget for it
IMO all that sandbox research they are doing now is useless, because they ain't gonna need it: they ain't gonna need it if they are not going, and they ain't gonna need it if and when they are really preparing to go because everything is gonna be different and nobody will give a shit about how such a power device might have looked like 10 years ago.
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.
[1] - https://en.wikipedia.org/wiki/Commercial_Crew_Development#Fl...
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.
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?
>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(<100 watts), you are already screwed.
[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...
https://www.nasa.gov/directorates/spacetech/game_changing_de...
Named after Krusty the Clown?
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 launching one, fresh, yet inert reactor, is not a big issue. The issue starts when we fly a lot of them and they start falling back to Earth after some service time.
It is relatively easy to build safe reactors on Earth (if only everybody was interested in safety and not their own agenda). It is much more difficult when you are going to shoot the entire device into space and you can't have 1000:1 of shields and casings.
Nuclear is exceptionally safe and all the recent accidents (and ones in the past, really) are all due to human stupidity and bypassing several failsafes. You can argue that's an issue that will never go away, and that's true in the absolute sense, but it's not a nuclear problem. It's a human issue. We're holding ourselves back for scientific research because of arbitrary issues; and the weapons test ban didn't even solve nuclear proliferation anyway.
Solar won't be held back because nuclear is finally an option. They serve two different purposes entirely.
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.
The problem with many pieces of large-scale tech is potential harmful side effects on unrelated people who did not ask for that.
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 reliant on active protection (pushing a lot of water as required means to prevent disaster).
But still, this is radioactive material in Earth orbit where stuff tends to fall back after some time and we don't always control when and where it reaches us.
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.
And your comment conveniently ignores Fukushima.
Half life time of nuclear waste ranges from 30 years to 24,000 years, so it's possible that hundreds of people die in 30,000 years from now by being exposed to nuclear waste from our time.
How many hundreds of billions of people will die over the next 30000 years from coal effects? How does that compare to your 'hundreds'?
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.
You could easily make the opposite argument - solar power is an easy way out of making nuclear power safe enough to go up into space. Having to use nuclear power for missions might do a lot of good in terms of researching and perfecting safe nuclear power.
It is maybe not as big a problem if we never plan it to return to Earth or Mars orbit (reactor is not as radioactive until it actually is started), but if we are using it to supply energy to the crew for the duration of the mission in deep space, the reactor will inevitably be radiactive and brought at least to Mars orbit or even back to Earth orbit.
Now, if that piece of junk falls to Earth, we have a big problem. Not the same kind of problem as falling solar array.
Not even Chernobyl, that had an atmospheric nuclear fire, the worst case scenario imaginable, had a economic, environmental or human live cost comparable to the impact of a single coal power plant.
It really concerns me when people on this forum, that has no excuse to not know better, parrots this anti-nuclear FUD.
Aside from the headline numbers of 31 dead and 237 with acute radiation poisoning other costs include:
- Encasing the site in a sarcophagus that will need to be maintained essentially forever. Immediate disaster response was estimated at $18B in today's dollars.
- A 30km exclusion zone from which 135,000 people were evacuated. Costs from this include costs of resettlement, loss of essentially all capital, cropland, and infrastructure in the zone
- Outside the zone millions of tons of contaminated earth were trucked for containment. Remediation is ongoing to this day and will continue indefinitely. Certain agricultural production is limited by type and practice to reduce probability of contamination from deeper in the soil.
- Health monitoring response across Europe in the aftermath, plus increased monitoring forever in the neighboring countries
- An unknown number of additional cancers and birth defects
There are additional costs, mostly more evacuees than were likely strictly necessary and compensation to others affected. Its unclear how much of this are legitimate costs or not, but its worth noting that uncertainty and lack of transparency themselves have costs.
https://en.wikipedia.org/wiki/Chernobyl_disaster
https://en.wikipedia.org/wiki/Effects_of_the_Chernobyl_disas...
Chernobyl still is a massive cost factor for plenty of countries ( all that are helping out financially with building the new mantle ).
Also look at the large effects of Fukushima.
Every time nuclear power comes up here on HN, there are some fierce defenders.
No matter how 'safe' newer generation plants are and how much it was the oprators fault, the potential for disaster is there. And that's not even mentioning the high lifetime cost when you consider safely storing the material, which often falls to the public.
Now please provide citations for your claims. Specifically 'Massive Costs' and 'large effects'.
Nuclear power does not need to be safe, only saver than the alternatives, this includes long term pollution from solar panel waste.
Every ounce of nuclear waste is entirely contained, every other power source's waste is dumped into the environment.
That's a little disingenuous, though, isn't it? It's only contained because no one will allow it to be dumped ("stored") near them. Actually, the fact that we have to take special precautions with nuclear waste due to its toxicity is a disadvantage of nuclear power vs. fossil fuels (for example).
Obviously, there is a much different calculus when thinking about Mars though.
Chernobyl costs for new "sarcophagus": 1.5bn (https://en.wikipedia.org/wiki/Chernobyl_New_Safe_Confinement, sources on bottom)
Fukushima cost: 188bn + (https://www.reuters.com/article/us-tepco-fukushima-costs/jap...)
Costs for decomissioning a nuclear power plant in the US: up to 500mil (https://www.nrc.gov/reading-rm/basic-ref/students/decommissi...) (which needs total cost and revenue to put it in perspective, but it gives a sense of the scale and difficulty of decommissioning and storage.
That paper, and others like it, demonstrates that radiation is much more benign than generally believed, and that level of resources spent on threads that don't exists, especially in comparison with others, like drink a can of soda a day, or living in a city, is not justifiable.