Video: Soyuz MS-01 leaves the space station for landing

Investigators believe a leak of propellant inside the Crew Dragon spacecraft’s propulsion system led to the capsule’s explosion April 20 during a ground test at Cape Canaveral, and a senior SpaceX official said Monday that delays are making it “increasingly difficult” to fly astronauts on the commercial spaceship before the end of the year.

Watch a replay of the launch Monday of an Orbital ATK Antares rocket carrying a commercial cargo craft destined for the International Space Station.

A corrective software patch has fixed a problem with a newly installed grapple fixture on one end of the International Space Station robot arm, NASA officials said Sunday. With the mechanism now fully operational, a re-planned spacewalk Monday to re-install a degraded unit has been called off.