Q&A with Mark Mulqueen, Boeing’s space station program manager

SpaceX test-fired a Falcon 9 rocket for the second time Saturday after replacing a valve following an earlier static fire test Wednesday. The move has postponed the Falcon 9 rocket’s launch with the Amos 17 commercial communications satellite to no earlier than Tuesday.

NASA officials gave approval Tuesday for SpaceX to begin regular crew rotation flights to the International Space Station with the launch of four astronauts set for Saturday from the Kennedy Space Center in Florida, signaling a transition from development to operations for the human-rated Dragon spacecraft.

Boeing and SpaceX hope to launch commercial crew ferry ships on long-awaited test flights later this year, but both companies face major challenges getting the spacecraft certified before late 2019 when seats aboard Russian Soyuz spacecraft will no longer be easily available for NASA space station crews, officials told lawmakers Wednesday.