The U.S. military’s next GPS navigation satellite was ready for launch from Cape Canaveral at 9:43 p.m. EDT Friday (0143 GMT Saturday) aboard a SpaceX Falcon 9 rocket. But SpaceX aborted the countdown just two seconds prior to liftoff.

Russian Soyuz commander Alexander Misurkin and two U.S. astronauts — flight engineers Mark Vande Hei and Joe Acaba — lifted off Tuesday from the Baikonur Cosmodrome in Kazakhstan. The trio began their six-hour journey to the International Space Station with a launch aboard a Soyuz rocket at 2117 GMT (5:17 p.m. EDT), and docking occurred at 0255 GMT (10:55 p.m. EDT).

In one of its final preflight tests, a SpaceX Falcon 9 rocket ignited at pad 39A in Florida for several seconds Thursday, ramping up to full throttle in an end-to-end checkout of the booster before liftoff next week on a space station resupply flight.