The U.S. Department of Defense wants to test a directed energy weapon in space, one that it hopes will someday destroy ballistic missiles moments after launch. The weapon, a so-called neutral particle beam, would be boosted into space and tested from orbit in 2023.

Neutral particle beams don’t get as much attention as lasers but are attractive in their own right. The weapons work by accelerating particles without an electric charge—particularly neutrons—to speeds close to the speed of light and directing them against a target. The neutrons knock protons out of the nuclei of other particles they encounter, generating heat on the target object.