SpaceX is targeting launches March 6 and March 11 for its next two missions after swapping an upper stage for its next Falcon 9 rocket with another stage already being readied for liftoff at Cape Canaveral.

United Launch Alliance engineers filled a Delta 4-Heavy rocket with super-cold liquid hydrogen and liquid oxygen propellants Friday at Cape Canaveral Air Force Station during a practice countdown before the heavy-lifter’s scheduled liftoff in June with a top secret U.S. government spy satellite.

An Orbital ATK Minotaur 4 rocket partially powered by modified motors from a Cold War-era nuclear missile lifted off early Saturday from Cape Canaveral with a small U.S. military satellite to help track other objects in space. The solid-fueled launcher took off at 2:04 a.m. EDT (0604 GMT) after a weather delay.