4 ms·
One of the biggest problems is that NASA's Plutonium-238 stockpile is running low, and is only barely being replenished (it was an artifact of nuclear weapon pr
by bpodgursky 7y ago
One of the biggest problems is that NASA's Plutonium-238 stockpile is running low, and is only barely being replenished (it was an artifact of nuclear weapon production, at the time). Each of Voyager 1 and 2 used something like 15kg of it for their RTGs. Because they were so heavily powered, the half-life won't power the craft down for decades.
The availability of Pu-238 is why European missions can't go past Jupiter without coordinating with NASA -- politically is impossible for them to produce nuclear spacecraft, but solar power becomes ineffective farther from the sun.
But given that NASA has a limited Pu-238 stockpile, they're only stocking new craft with the minimum necessary to hit the key science objectives.
There's (finally) a new program to produce more if it, but in very limited quantities: https://www.businessinsider.com/nasa-nuclear-battery-plutonium-238-production-shortage-2017-8 https://www.businessinsider.com/nasa-nuclear-battery-plutoni...
- jandrese 7y agoThis was a mostly political problem with Congress kicking the can down the road for 20 years. According to the article they've restarted production although a bit slower than they wanted. Of course you can't stockpile radioactive materials for too long. Their very nature limits their shelf life. So constant production is necessary if you want to use it on missions.
- baking 7y agoDo you know if the new designs proposed using thermophotovoltaics and silicon-carbide pellets are more efficient than traditional RTGs in their use of plutonium? Eli Yablonovitch mentions work being done at Berkely: https://www.youtube.com/watch?v=lDxJsa8miNQ&t=3280 https://www.youtube.com/watch?v=lDxJsa8miNQ&t=3280
- marcoseliziario 7y agoWouldn't kilopower (https://en.wikipedia.org/wiki/Kilopower https://en.wikipedia.org/wiki/Kilopower) be an alternative? It used U-235.
- theandrewbailey 7y agoI wonder how long that reactor would provide useful energy. U-235 has a half life of 700 million years. If it were to last that long, they'd be dealing with thermonuclear Long Now-type problems.
- baking 7y agoThe Kilopower reactor uses a chain reaction to trigger fission so the U-235 will be depleted much faster than the half-life. Wikipedia says its operational life is 12-15 years.
- mongol 7y agoSome years ago Sweden handed over 3kg plutonium to the US. They should have given it to ESA instead. https://obamawhitehouse.archives.gov/the-press-office/2012/03/26/fact-sheet-plutonium-removal-sweden https://obamawhitehouse.archives.gov/the-press-office/2012/0...
- baking 7y agoIt needs to be Pu-238 which is not a typical component of nuclear waste. https://neutronbytes.com/2017/03/05/nasa-re-starts-pu-238-production-at-two-sites/ https://neutronbytes.com/2017/03/05/nasa-re-starts-pu-238-pr...