Nearly three months after the explosion of its Crew Dragon spacecraft, SpaceX has preliminary results to share about what it suspects caused failure. On April 20, the Crew Dragon vehicle experienced what the company called an “anomaly”. Leaked images appeared to show the spacecraft exploding in a cloud of smoke on its test pad during some sort of test at Cape Canaveral in Florida.
SpaceX has revealed the cause of the explosion appears to have been a faulty valve. SpaceX VP of Build and Flight Reliability Hans Koenigsmann said a check valve allowed a slug of liquid oxidizer to leak into the high-pressure abort system. The slug caused the valve to ignite, leading to the vehicle’s explosion.
The SpaceX statement said the reaction between the titanium and the NTO slug was “not expected”. According to the statement, titanium has been “used safely over many decades and on many spacecraft from all around the world”. SpaceX is now planning to replace the type of valve used from a check valve to a burst disk. The burst disk will make Crew Dragon a safer vehicle by separating the oxidizer and fuel from the liquid components.
The vehicle that exploded was going to be used for an in-flight abort test. SpaceX said the issue occurred during a test of the capsule’s thrusters. The capsule’s smaller Draco thrusters were tested successfully, but the explosion happened about 100 milliseconds before the ignition of the larger SuperDraco thrusters. High-speed cameras captured the incident, and investigators have examined various debris that had been ejected around the site.
No one was hurt during the incident. SpaceX said in its statement, “In accordance with pre-established safety protocols, the test area was clear and the team monitored winds and other factors to ensure public health and safety.” SpaceX is now delaying its first launch of humans to at least the end of 2019. Koenigsmann declined to give a tentative launch date for the test flight with astronauts, explaining that more issues could come up in the coming months.