NASA's Plutonium Supply Dwindling; ESA To Help

astroengine writes "NASA's stockpile of the plutonium isotope Pu-238 is at a critical level, causing concern that there won't be enough fuel for future deep space missions. Pellets of Pu-238 are used inside radioisotope thermoelectric generators (or RTGs) to generate electricity for space probes traveling beyond the orbit of Mars — solar energy is too weak for solar arrays at these distances. Blocked by a contract dispute with Russia to supply Pu-238 and the US Department of Energy that has not been granted funds to produce more of the isotope, NASA lacks enough of the radioisotope to fuel the future joint NASA-ESA mission to Europa. However, the head of the European Space Agency has announced that they have plans to commence a new nuclear energy program to alleviate the situation."

Comments

Actually...

[sznupi]

NASA is launching quite soon a spacecraft to Jupiter relying on solar panels. And the ESA spacecraft part of mentioned joint mission will also rely on solar panels. Seems they have improved quite a bit / I wouldn't be too surprised at seeing, eventually, some mission to Saturn relying on them.

Not saying that we don't need RTGs, we do of course (for further missions or more complex ones; using solar panels whenever possible saves RTGs for those...), but part of the premises of TFS is not terribly accurate.

Re:Actually...

[Anonymous Coward]

Even on Mars, the MER rovers use RHUs (radioactive heating units) to keep the electronics warm during the Martian night and winter. Ditto for most any mission going beyond the Earth's orbit, especially for landers (which see night).

An orbiter can conceivably be pointed to the sun, but the solar constant is pretty low. Jupiter is 5 AU away from the sun, so the solar constant is 1/25th of Earth: a monster 40 Watts/square meter. Compare this to radiation cooling to cold sky which is about 100W/square meter. Better have pretty good insulation, which takes volume and mass, both in short supply on a spacecraft.

Juno has enormous solar panels, which raise all sorts of practical problems.

You've got to decide whether you want to burn your mass allocation on solar panels or on science instruments.

Re:Actually...

[Chris Burke]

It'd have to be one damn beefy laser, since at the distances we're talking, even a very tightly focused laser beam has diverged to a huge diameter. A ridiculously harder problem than hitting a space elevator climber. Tens of thousands of kilometers, vs about 600 million kilometers at the closest. I don't think it's practical at this time to beam power from earth to Jupiter. Solar power would be way stronger than anything we could provide.

Re:Recycle Nukes?

[Anonymous Coward]

Pardon my ignorance and possible first post - but couldn't NASA just recycle some retiring nuke warheads for plutonium?

Oh, yes, any moron in Slashdot is a rocket scientist.

No, they can't. Nukes have Pu-239 (the fissile isotope), and they need Pu-238 (the alpha emmiter).

Re:Recycle Nukes?

[Wyatt Earp]

We only made it in the US at Hanford and Savannah River, both of those are shut down now.

It's very toxic, very hard to work with and very flammable and very much controlled, so thats why no private companies are in the market to produce it.

To produce Pu-238 you produce a ton of weapons grade plutonium, do we really need more of that crap churned out?

http://www.fas.org/nuke/intro/nuke/plutonium.htm

Re:NASA had another option in 1981

[compro01]

Using a gamma emitter (rather than an alpha emitter like Pu-238) means you need A LOT more shielding (and thus more weight and volume) to prevent it from screwing with the electronics and instruments.