6 ms·
Mars rover mission will use pioneering nuclear power source
- fsmv 2y agoSo the new part is they didn't bother generating power in the RTG because they only need the heat? That doesn't seem very pioneering to me, it's just a pile of plutonium.
- yeknoda 2y agoit's not plutonium. it's americium
- t43562 2y agoThe new part is that it's using Americium. That's it. It's a challenge to use the material for various reasons but the wonderful thing about it is that it's easier to get hold of apparently. The UK, in fact, has a problem with its plutonium stockpiles being polluted increasingly by Americium and now there's something it can be used for. There are significant disadvantages (lower power per weight, high gamma ray activity) and some upsides (longer half-life by a big factor).
- deleted 2y ago[deleted]
- outworlder 2y agoPiles of plutonium are pretty difficult to come by.
- acheron 2y agoI figured by 1985 it’d be available in every corner drugstore.
- preisschild 2y agoIf you have good contacts to Gadaffi and the Libyans, you might get it from them.
- shadowgovt 2y agoJust have some pinball machine parts ready to trade.
- thatoneguy 2y agoWhile this wasn't available in 1985, if it's a pile of parts that add up to, say, Addams Family Pinball, then that's the going rate for at least 1.5 grams of weapons-grade plutonium from the DoE last I checked (NRC and possible state fees not included).
- shadowgovt 2y agoWith that much and some careful engineering, I can probably generate 1.21 jigawatts of power.
- hi-v-rocknroll 2y agoNawh, it's already obsolete with Mr. Fusion. Just add banana peels.
- ffhhj 2y agoIf they only need heat, could they use nuclear waste?
- orev 2y agoThat’s exactly what they’re doing. FTA: americium-241, a by-product of plutonium decay
- perihelions 2y agoDoesn't talk about the downsides, which are mainly that Am-241 has about five times lower power density than Pu-238, and also needs additional radiation shielding. https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Fuels https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge... There's no spacecraft-related reason to select this—it's strictly worse—it's just the US/EU are in a decades-long ongoing shortage of Pu-238, and this is the only available alternative. I don't think this is "pioneering" in any positive sense of the word. IMHO, it's embarrassing.
- deleted 2y ago[deleted]
- Retric 2y agoThe half-life of americium-241 is about 432 years, that’s a huge advantage. The Voyager probes at half power and because of exponential decay it’s not easy to simply start with more Pu-238 to compensate. You need to deal with dumping exponentially more waste heat at the beginning when you want to extend their lifespan. Not everyone needs to last that long, but Opportunity died 15 years after launch plenty of time for a significant reduction in power output. When the cost per pound to orbit was higher it was an obvious choice, but these days it’s more questionable.
- deleted 2y ago[deleted]
- Dylan16807 2y agoPlutonium has a half life of almost 90 years which isn't too shabby. If you want ten more years at full power then you only need to add about 10 percent more. The exponent is not very big. An americium system that starts off bigger is going to be worse for most kinds of mission. Especially Mars landers that are going to wear out one way or another.
- FranOntanaya 2y agoIt's still boosting the science profile of the mission to use it as test bed for Americium. There's a lot of science to be done in the Kuiper belt and further out where longevity may matter eventually simply because we wouldn't be sending repeat missions to each dwarf planet out there anytime soon.
- outworlder 2y agoThat seems like a big deal. RTGs have been constrained by short supply, the department of energy is the only producer in the US. This is 'just' a heating device for now, but if they start delivering RTGs, as alluded to in the article, that would be fantastic. Americium is the same stuff that's in smoke detectors, albeit in tiny amounts.
- shadowgovt 2y agoShort supply, specifically, because the stuff has to be more meticulously tracked than elephant ivory. If the wrong people get their hands on enough of it, it is, at best, a dirty bomb.
- philipkglass 2y agoThe short supply is because plutonium-238 is difficult to make in relatively pure form. It's found in spent power reactor fuel, but only in tiny concentrations and mixed with much larger quantities of other plutonium isotopes. The United States started making Pu-238 in useful quantities again last year: https://www.ornl.gov/news/pu-238-shipment-quantity-opens-tap-space-missions https://www.ornl.gov/news/pu-238-shipment-quantity-opens-tap... https://www.energy.gov/ne/articles/us-department-energy-completes-major-shipment-plutonium-238-nasa-missions https://www.energy.gov/ne/articles/us-department-energy-comp... The process requires irradiating neptunium-237 (itself a small portion of spent nuclear fuel, requiring special chemical separation) in a government reactor. It's also true that Pu-238 is dangerously radiotoxic if inhaled or ingested, but that's true of every material that provides a useful quantity of decay heat, including the americium-241 alternative used in this new mission. The primary advantage of using Am-241 over Pu-238 is that it's easier to recover from spent power reactor fuel; there's more of it in spent fuel than Pu-238, and it's the most abundant isotope: https://en.wikipedia.org/wiki/Isotopes_of_americium https://en.wikipedia.org/wiki/Isotopes_of_americium Which means that Am-241 can be separated chemically from old fuel and does not require any additional nuclear treatment before use as a radioactive heat source.
- jjk166 2y agoThat's not why it is in short supply. Plutonium based RTGs use Plutonium 238, a non-fissile isotope. Being an alpha emitter, it is a terrible choice for a dirty bomb - certainly no better than any other potential RTG fuel candidate. Obviously it is a radioactive isotope, and a hazardous one at that, but it is not meticulously tracked for security purposes. Indeed up until lithium batteries rendered them obsolete, Plutonium-238 was used in nuclear powered pacemakers. Plutonium-328 is a trace impurity in general plutonium production, but production of RTG-grade Plutonium-328 needs to be done in special reactors, where Neptunium-237 is bombarded with neutrons. The US shut down its only Pu-238 producing reactor in 1988, along with the rest of the Savannah River Site. Since then, Russia has been the sole source of Pu-238. Since 2013 the US has been trying to set up a new Pu-238 production plant at Oak Ridge National Labs, but even at full scale production it can still only produce 1.5 kg per year.
- bilsbie 2y agoAnyone know what temperature this runs at internally? If the black body radiation is high enough frequency maybe we could tune a special solar panel to pick it up and be dramatically more efficient than thermal electric.
- perihelions 2y agoThey've built those in the lab decades ago [0]. I don't know what the large drawback is that prevents them from being more widely used. In the thermophotovoltaic case they were looking at emitter temperatures between 1,200 and 1,350 K. [0] https://sci-hub.se/https://doi.org/10.1063/1.1867178 https://sci-hub.se/https://doi.org/10.1063/1.1867178 ("Thermophotovoltaic Converter Performance for Radioisotope Power Systems", 2005)
- sandworm101 2y agoBlackbody radiation is the wrong approach. If you are going to slap a PV panel onto a radioactive source then tune it for the emitted radiation rather than the blackbody heat. Radiation from nuclear decay should be very narrowband, allowing for a more efficient PV solution.
- perihelions 2y agoThere is no emitted radiation: the heat source self-absorbs its own alpha radiation and converts it into heat.
- angiosperm 2y agoArrayed as a thin film on a substrate, you can use the kinetic energy of the alpha particles directly for thrust. The substrate will need to dissipate some heat from nuclei emitted in the wrong direction.
- eternauta3k 2y agoWhat is the status of making power directly from e.g. alpha radiation?
- deleted 2y ago
- mechhacker 2y agoI was hoping there would be something here about using Stirling engines that use decay heat, but looks like they are just using the decay heat itself and not generating electricity. The space stirling engines that NASA has worked on in a few iterations made a lot more electrical power than the older RTGs, with the tradeoff of moving components and associated issues.
- krunck 2y agoA Wikipedia page[1] claims that Chandrayaan-3 used Am241 but the referred article does not mention anything. [1] https://en.wikipedia.org/wiki/List_of_nuclear_power_systems_in_space https://en.wikipedia.org/wiki/List_of_nuclear_power_systems_...
- qayxc 2y agoReading the linked source the tells you that the RHUs were not installed on the rover due to mass constraints and might instead be used in future missions. The propulsion module carried an experiment, though, which was wasn't used for providing actual heating and a test only.
- perihelions 2y ago- "It is thought[by whom?] that national security reasons delayed the disclosure to the media." Ludicrous. More realistic is they were afraid of negative media coverage and protests about the potential public health hazard to their people. In the US, NASA goes to extreme lengths to qualify their space radioisotope devices, their survivability and how they fail in a failed rocket launch or unplanned atmospheric reentry. All of which is transparent to the public, and to independent review. There's AFAICT the opposite of such transparency and accountability here. It's not clear at all what degree of risk this (at-the-time secret!) radioisotope launch had, how the containment device was engineered and what potential (secret) flaws it could have.
- swamp40 2y agoESA finally using nuclear power? Hallelujah. They actually learned from the mistake of Rosetta's Philae landing in the shade on Comet 67P, where its solar panels couldn't produce any power and it died humiliatingly.
- kristianp 2y agoIt's striking that this is only used on the lander to keep it warm until the rover deploys. Seems overkill if the lander is only used briefly.