Q&A with John Elbon, VP and general manager of Boeing’s space exploration division

Seven astronauts and cosmonauts are gearing up for launches April 9 and April 22 to the International Space Station, replacing seven outgoing crew members set to land in Kazakhstan and off the coast of Florida on April 17 and April 28.

United Launch Alliance teams loaded super-cold liquid hydrogen and liquid oxygen into an Atlas 5 rocket Friday at Cape Canaveral during a countdown dress rehearsal for a planned launch next month with the Solar Orbiter mission, a robotic spacecraft to study the origins of the solar wind and image the sun’s poles for the first time.

The rollout operation on Tuesday followed a day of evaluations using Boeing’s weight and center-of-gravity machine to determine the final measurements on the spacecraft. Launch is still targeting May 6 at 10:34 p.m. EDT (0234 UTC).