Humans could vastly expand our presence off Earth by powering spacecraft with nuclear reactors, but this dream has been stalled out for decades, partly due to regulations governing the use of nuclear power in space. Though many orbiters, deep-space probes, and Mars rovers run on radioisotope batteries fueled by plutonium, the United States has only ever launched one nuclear fission reactor in space, called SNAP-10, in 1965.

A startup called Atomos Space is now working to change this decades-long lag with a plan to conduct a basic critical test of a low-power (100-Watts thermal) fission reactor in orbit. Called the Neutrino Space Nuclear Pathfinder, the planned spacecraft would navigate a new U.S. government framework that clarifies many ambiguous regulations surrounding space nuclear power.

Atomos Space, which was founded in 2017 and is based in Denver, Colorado, is currently investing in a reactor as part of the company's larger vision to develop "space tug" services that guide satellites into target orbits after launch. Though it is not the only organization developing space nuclear reactors—others include companies like SpaceNukes and X-energy, as well as government agencies such as NASA and DARPA—the company has set itself apart with a focus on the bureaucratic legwork, according to Atomos Space CEO Vanessa Clark.

"We're definitely the first company to go out there and say that the biggest step isn't the technology; it's proving that it's possible from the regulatory perspective," said Clark in a joint call with Lucas Beveridge, Atomos Space's senior nuclear engineer. "We're definitely a trail-blazer from that perspective."