The United States wants a reactor on the moon by 2030. A Russian-Chinese alliance is working on one for 2036. Some leading scientists say the danger is great. In late August, NASA asked contractors to prepare to build a nuclear reactor that could survive a space voyage and run without maintenance near the moon’s south pole.

That may sound like science fiction, but the agency wants it ready to be launched by December 2030. There is a reason for the rush. Russia aims to have a lunar reactor running by 2036 as part of a secretive partnership with China. NASA has already sped up its schedule to beat its rivals.

The race is for the very future of space exploration. The United States and China want to be first to establish a moon base, to search for resources like frozen water and to launch missions deeper into the solar system. Controlling access to the moon’s assets is vital to this mission. Both superpowers believe a nuclear reactor is the centerpiece of this ambition.

The countries plan to turn on their reactors only after they reach the moon. But some leading scientists caution that governments are moving too quickly in an era of space exploration that has seen some notable disasters. In the last six years, multiple Chinese, American and Russian rockets have failed and exploded, and a Russian lander has crashed into the moon. Space junk regularly tumbles to Earth.

Failures could cause a chain reaction with dire consequences. Falling reactor debris could scatter radioactive material, as happened in Canada in the late 1970s. An explosion or a meltdown on the moon’s surface would risk turning entire regions into no-go zones.