Now We Know What Caused the SpaceX Explosion

A Crew Dragon test ended with a bang in April, as an engine meant to power ejection systems exploded a fraction of a second before ignition. SpaceX reports they now know the reason for the mishap. The accident took place on April 20, during a static fire test of the engine at Landing Zone 1 at Cape Canaveral Air Force Station in Florida.

The accident occurred at at 2:13 PM EDT, just one-tenth of a second prior to the ignition of the last thrusters. A leak of nitrogen tetroxide (NTO), the oxidizer fueling the vehicle, ignited a check valve, resulting in the blast which consumed the engine.

A SuperDraco rocket engine similar to the one which exploded in April during a static fire test. Image credit: SpaceX

Just prior to the explosion, a leaking component allowed NTO to enter high pressure helium tubes during ground processing. Some of this NTO entered a helium check valve during rapid initialization of the launch escape system, resulting in a structural failure of the titanium valve. It was the failure of the valve which led to the ignition which triggered the explosion.

The Crew Dragon spacecraft includes two separate propulsion systems — 16 Draco thrusters operating at low pressure for on-orbit maneuvering, and a high-pressure SuperDraco engine, composed of eight Draco thrusters, designed to carry the crew to safety in the event of a catastrophic failure.