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SpaceX finds surprising cause behind Crew Dragon explosion

One of the spacecraft designed to launch astronauts from US soil for the first time in years has been grounded since April.


The SpaceX Crew Dragon will head to the ISS on its first test flight.


On April 20, a SpaceX Crew Dragon capsule unexpectedly exploded during a ground test at Cape Canaveral in Florida. After an investigation, NASA and SpaceX now say a leak led to a surprising chemical reaction that destroyed the spacecraft.

An accident investigation team involving SpaceX, NASA, the Federal Aviation Administration, US Air Force and National Transportation Safety Board collected debris from the explosion and the Dragon's SuperDraco thrusters and transported it to the company's development facility in McGregor, Texas, for testing.

On Monday, SpaceX released a statement outlining how a leak in the spacecraft's pressurization system allowed a liquid oxidizer -- nitrogen tetroxide, or NTO -- to make contact with a titanium valve. 

The resulting explosive reaction between the two substances was the subject of a leaked video of the Dragon's final fiery moments that made headlines in late April.

"It is worth noting that the reaction between titanium and NTO at high pressure was not expected," reads the company's statement. "Titanium has been used safely over many decades and on many spacecraft from all around the world."

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On a call with reporters, Hans Koenigsmann, SpaceX's vice president of mission assurance, emphasized that the problem was entirely within the pressurization system and not tied to any flaws in Crew Dragon's engines. He said the company will be replacing the valves with burst disks that seal more completely to mitigate the risk.

Glen Meyerowitz, a former SpaceX engineer noted on Twitter that "this change to burst disks from check valves may decrease the reusability of the Crew Dragon spacecraft. Depending on how/where these burst disks are installed they may be extremely difficult to remove and replace after one ruptures."

SpaceX didn't immediately respond to a request for further comment.

Crew Dragon is part of NASA's Commercial Crew program, which, along with Boeing's Starliner, aims to return to using US-built craft to deliver astronauts to space, a task that has been outsourced to Russian spacecraft since the end of the Space Shuttle program. However, both American craft have run into problems during tests this year

Crew Dragon previously made a successful uncrewed voyage to the International Space Station, but has yet to carry humans to space. 

NASA's Commercial Crew Program manager Kathryn Lueders and Koenigsmann both said they are hopeful Crew Dragon will fly by the end of the year, but that more testing remains to be done.

Koenigsmann specifically noted that a flight in 2019 is possible but is also "increasingly difficult."