Q&A with Keith Gendreau, principal investigator of the first X-ray space communications experiment (members only)

A Falcon 9 rocket powered by a recycled first stage lit its main engines for a hold-down firing on a launch pad Tuesday at Vandenberg Air Force Base in California in preparation for launch with an Argentine radar satellite on a mission that will feature the first SpaceX booster landing on the West Coast.

Tugged along a historic route leading to the launch pad where Yuri Gagarin took off 1961 to become the first person in space, a Soyuz rocket rolled out of its assembly hangar in Kazakhstan and stood up on its launch mount Sunday.

Watch a replay of the pre-launch news conference for the SpaceX CRS-10 space station resupply mission is held at the Kennedy Space Center Press Site on February 17, 2017.