Supplying spacecraft with electricity: a challenge within reach for nuclear power

Nuclear power is necessary in spacecraft for getting higher electric power over a longer period but reducing its weight is a challenge. Today, the most advanced project for an embarked nuclear reactor is the American Kilopower project. Kilopower is a compact fission reactor, the heat produced by U²³⁵ fission is turned into electricity thanks to a Stirling cycle. Its output power is 10 kWe for a weight (shielding included) between 1.5 and 2 tonnes. The power-to-weight ratio is far better for bigger reactors: about 1 MWe for 10 to 15 tonnes but weight is limited in spacecraft. China, who is developing the concept of molten salt reactor (MSR) for its nuclear power plants, is considering the concept for space missions. In France a study has shown the feasibility of a spatial MSR and its power-to-weight ratio would be better than that of the Kilopower reactor. (A.C.)