It sounds like a scene from “Gravity,” but a growing army of space debris orbiting the Earth is increasing the risk of collision for U.S. satellites, the commander of the U.S. Strategic Command said.

“My Joint Space Operations Center [at Vandenberg Air Force Base, California] routinely tracks more than 17,000 objects the size of softballs or larger,” Adm. Cecil Haney said. “Which means there are smaller objects that we do not track.”