France, Aug. 31 -- The United States is racing to build nuclear power reactors for the Moon, with the first system planned for the end of the decade. This would keep astronauts alive through weeks-long lunar nights, as well as powering permanent bases and outposts - and giving Washington an edge over China and Russia in a new space race.

NASA confirmed in a directive signed at the end of July that it will appoint a nuclear power czar and select two commercial proposals for the project within six months.

The aim is a 100-kilowatt reactor, ready to launch by 2029 or 2030. Unlike solar panels, nuclear systems can work around the clock - vital in a place where one night lasts 14 days. Why nuclear, why now?

The announcement comes as the US ...