A rocket engine with a long pedigree marked a big milestone on Monday. It’s 60 years since the hydrogen-fueled RL10 engine debuted onboard a Centaur upper stage launched from Cape Canaveral on Nov. 27, 1963.

The U.S. Space Force says it will launch two GPS navigation satellites on reused Falcon 9 boosters next year through a restructured contract with SpaceX that saved taxpayers $52 million, the first time the military has agreed to fly operational national security payloads on previously-flown rockets.

Rocket Lab’s Electron rocket, a commercially-developed light-class booster, lifted off at 1:33 a.m. EST (0633 GMT) Sunday, carrying 13 CubeSats into orbit under contract to NASA.