A little under two months after an anomaly during a static fire test that resulted in the destruction of a Crew Dragon spacecraft, SpaceX has released an update on the progress of the provider’s investigation.
The mishap that resulted in the destruction of the Crew Dragon spacecraft that was recovered following the SpaceX Demo-1 mission occurred on Saturday, April 20. In preparation for an inflight abort test, SpaceX was performing a static fire test of the spacecraft’s two thruster systems.
The sixteen Draco thrusters, which are used for on-orbit manoeuvring were test-fired first and performed as expected. As SpaceX ground crews were preparing to fire the eight SuperDraco thrusters, which are used in the event of a launch escape, the spacecraft exploded.
In a July 15 press release, SpaceX revealed that the anomaly that caused the explosion occurred approximately 100 milliseconds prior to the ignition of the Crew Dragon’s SuperDraco thrusters. According to SpaceX, the explosion was the result of “a leaking component” allowing liquid oxidizer, specifically nitrogen tetroxide (NTO) to enter the spacecraft’s high-pressure helium tubes. A “slug” of NTO then impacted with a helium check valve at high speed causing the valve to fail. The failure of the titanium valve in the high-pressure NTO environment caused an ignition which ultimately led to the explosion.
Although the investigation is not yet concluded, SpaceX has moved to eliminate “any flow path within the launch escape system for liquid propellant to enter the gaseous pressurization system.” Additionally, the titanium check valves will be substituted for burst disks, “which seal completely until opened by high pressure, will mitigate the risk entirely.”
It is still unclear to what extent the investigation will have on SpaceX’s Commercial Crew Program flights. However, it is likely that a crewed flight to the International Space Station will slip to no earlier than the first quarter of 2020.