[perihelions]

That'd be difficult in Mars' atmosphere -- but the planned *Titan* helicopter will actually be RTG powered:

https://en.wikipedia.org/wiki/Dragonfly_(spacecraft)#Design_...

https://news.ycombinator.com/item?id=18947350 ("NASA May Decide This Year to Land a Drone on Saturn's Moon Titan")

https://news.ycombinator.com/item?id=20337042 ("A technical look at the Dragonfly Titan mission")

>"Flight on Titan is aerodynamically benign as Titan has low gravity and little wind, and its dense atmosphere allows for efficient rotor propulsion.[35] The radioisotope thermoelectric generator (RTG) power source has been proven in multiple spacecraft, and the extensive use of quad drones on Earth provides a well-understood flight system that is being complemented with algorithms to enable independent actions in real-time.[35]"

[nharada]

Awh, I thought that meant infinite flight time, but it appears instead it carries the RTG along to recharge Li-ion batteries at night.

[Sharlin]

Yeah, unfortunately power density is not exactly where RTGs shine.