[mhh__]

Plutonium is really heavy, if you were to do that it strikes me that you'd be better off having some kind of wireless charging device which the helicopter lands on (But at that point why not solar power).

You'd probably already need some batteries anyway as I'm guessing that the transient spikes in power usage would probably exceed any RTG you could fit in a helicopter anyway.

[ncmncm]

Probably you would use strontium-90, instead, if weight was important. Strontium is 7.5 times less dense than plutonium.

Strontium-90 produces 0.95W/g, where Pu-238 produces only 0.57 W/g. So, it takes only 3/5 as much, by weight, to produce the same heat as a Pu-238 RTG, although it takes 4.5x as much room. Room is relatively cheap on spacecraft, vs. mass.

This makes me wonder why they use Pu-238 RTGs in spacecraft at all. Maybe because it lasts a bit longer?

[ncmncm]

... Probably just because of the industrial process availability of plutonium, as spinoff from weapons work. Sr-90 has no local infrastructure. Which is just dumb.