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

Some space probes use heat from natural radioactive decay [of a radioactive material] to produce electricity via thermocouples and something called the Seeback effect. This does not require any sort of reactor and does not require moving parts. However the power output is relatively low. Basically the heat from the emitted radiation from the material is turned into electricity for powering components.