NASA's commercial crew program has seen more than its fair share of delays in recent years, as both SpaceX and Boeing have to push back their timelines due to various problems. SpaceX's Crew Dragon proved to have made good progress late, with a blurry flight to the International Space Station earlier this year, but the company hit a bit of a snag when the canister exploded during a static fire test.
The answers were difficult to come up with in the explosion flow, with SpaceX and NASA calling it both an "anomaly" and the investigated cause. Now, months later, the company finally says it knows exactly what went wrong.
In a new statement on the company's website, SpaceX says that the reason for the unexpected explosion was due to a leak that made it possible for a chemical to force itself through a check valve when the launch interruption system interrupted. The valve failed, causing ignition and subsequent explosion.
Evidence shows that a leaking component permits liquid oxidants ̵1; nitrogen tetroxide (NTO) – to enter high-pressure helium pipes during basic processing. A slug of this NTO was run through a helium valve at high speed during rapid initiation of the launch relief system, resulting in structural failure in the check valve. The failure of the titanium component in a high-pressure NTO environment was sufficient to cause the non-return valve to ignite and lead to an explosion.
SpaceX says it did not expect NTO and titanium to react based on established standards, emphasizing that titanium has been safely used for many decades on many spacecraft from around the world. "
The company says it is already in the midst of adapting its design to prevent such failures from happening in the future, including the elimination of control valves in favor of a much more robust alternative.