[selectodude]

Using plutonium works great but there are two issues. 1) they don’t output that much power. Few hundred watts at most, and they decay at a fixed rate. 2) you need to get your hands on a decent amount of plutonium. Great for dirty bombs, hard to source.

[TkTech]

Both Canada and the US have restarted production specifically to produce RTGs for NASA, but the process takes time to scale up and automate. It's gone up 4x in 4 years and continues to increase, so this is a problem that will eventually be "fixed".

[floatrock]

Isn't it something like space-reactor plutonium is a waste product from nuclear weapons production, and since we don't really make nuclear weapons at scale anymore, we aren't really making (refining?) plutonium anymore. And NASA has some amount on reserve, but they're rationing it out carefully. So the Clipper probe had to go with a massive solar array (100ft, the length of a basketball court) because they would rather save their plutonium for some future rover mission.

[nick__m]

it don't make sense to stock hot plutonium to use it later, it loose power and decays overtime wherever you use it or not!