Watch a time-lapse of the Crew Dragon access arm installation (members only)

SpaceX chief executive Elon Musk on Tuesday outlined an ambition to send humans to Mars with methane-fueled reusable spaceships and the largest rocket ever built, an effort he said will likely require government support and initially cost billions of dollars to develop and test.

Christopher Ferguson, commander of the final space shuttle flight and now a Boeing executive, has stepped down as commander of the first piloted test flight of the company’s troubled CST-100 Starliner commercial spacecraft, he and Boeing announced Wednesday. He has been replaced by NASA astronaut Barry “Butch” Wilmore.

The last of Japan’s current series of HTV cargo freighters arrived at the International Space Station Monday with a fresh set of lithium-ion batteries, ready for installation on the research lab’s solar power truss after the scheduled docking of a two-man crew on a SpaceX Dragon spaceship later this week.