Before the explosion, the test was proceeding according to plan, Hans Koenigsmann, SpaceX’s vice president of Mission Assurance, said at a press conference about SpaceX’s upcoming resupply mission to the ISS. The capsule was tethered in place for the test, which was designed to make sure that the system’s thrusters were working properly. Koenigsmann said that the capsule powered up “as expected” and then sets of smaller thrusters on either side of the vehicle called Dracos fired for five seconds each. Those tests “went very well” said Koenigsmann. Then it was time to test the SuperDracos, the thrusters designed to...