Good guess! Fuel cells have long been important power sources for spacecraft, going back to the Gemini missions in the 1960s.

But you have to bring along hydrogen and oxygen for fuel, so they aren't the best power source for long missions.

Batteries (One kilogram of batteries produces .05 kilowatts)

Nuclear (One kilogram of fuel cells produces .03 kilowatts)

Solar energy (One kilogram of solar cells produces .10 kilowatts)

© The Children's Museum of Indianapolis, 1999