Power System

What are possible power sources for satellites?

What are the fuels for radioisotope thermoelectric generators?

A "fuel" for a radioisotope thermoelectric generator is a kind of unstable element. As that unstable element decays, it produces heat, which the RTG can use to make electricity.

The table below summarizes which kinds of fuel are used. Note that when we talk about watts, we're talking about a unit of power, and that we're referring to how many watts of power are generated in terms of heat. There is some loss of wattage when converting from heat to electricity through thermocouples.

Element Half-life (years) Watts/g (thermal) $/Watt (thermal)
Polonium-210 0.378 141 570
Plutonium-238 86.8 0.55 3000
Cesium-144 0.781 25 15
Strontium-90 28.0 0.93 250
Curium-242 0.445 120 495

DS1 does not use RTGs.

What are radioisotope thermoelectric generators?

Are radioisotope thermoelectric generators safe?
What are tradeoffs between different kinds of power sources for spacecraft?