how are “nuclear powered” submarines and space probes powered?

Question

In other words, where do “nuclear powered” vehicles get their power from?

I imagine it’s not from fusion or fission, nor can it involve getting water to turn to steam, an in many other types of power generation.

So how does it work?

EDIT: it seems that nuclear submarines actually do use fission, so I’m switching my question to only focus on space vehicle power generation.

In: 3

Answer 1

They have thermoelectric piles. These would be like the peltier coolers you can buy on ebay/amazon.On those, if you connect power, it moves heat so one side gets hot and the other gets cold. It’s a pretty big difference too. They work the same in reverse too, so if one side is hot and the other cold, it’ll output power.

edit – this is for the satellites…
edit 2 – it is radioactive fission, the radioactive decay of elements makes them hot, and that heat is put through the thermopiles.