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

Launch of a SpaceX Falcon 9 rocket carrying a Dragon cargo ship loaded with more than 5,100 pounds of equipment and supplies bound for the International Space Station was called off Tuesday less than two minutes before liftoff because of apparent problems with the second stage engine steering system.

The mission features orbital transfer vehicles that are carrying 30 of the payloads with 14 being deployed after the initial mission launch. Liftoff from pad 4 East at Vandenberg Space Force Base happened at 10:49 a.m. PST (1:49 p.m. EST, 1849 UTC).

Track the progress of the Soyuz TMA-19M spacecraft and its three-man crew through Tuesday’s countdown, launch and docking with the International Space Station.