SpaceX and NASA detail cause of Dragon test failure, crewed flight this year looks ‘increasingly difficult’
SpaceX held a press conference on Monday to discuss the results of a months-long investigation conducted by itself and NASA into an anomaly that took place during a static fire test in April. The investigation found that the “anomaly” which occurred during the test was the result of oxidizer mixing at very high pressure with the helium component of the SuperDraco rocket engine propellant system.
On April 20, SpaceX held an abort engine test for a prototype of its Crew Dragon vehicle (which had been flow previously for the uncrewed ISS mission). Crew Dragon designed to be the first crew-carrying SpaceX spacecraft, and is underling a number of test to prove its flight-readiness to NASA. The test encountered a failure that was instantly visible after the first few tests proved successful, with an unexpected explosion that produced a plume of fire visible for miles around the testing site at its Landing Zone 1 facility in Cape Canaveral, Florida.
SpaceX BP of Build & Flight Reliability Hans Koenigsmann and NASA Commercial Crew Program Manager Kathy Lueders took members of the media through the results of their joint investigation into the cause of this anomaly. Koenigsmann explained that thanks to identifying burn marks around a check valve in the system that’s meant to separate the oxidizer and fuel components under pressure. These check valves contain a spring which can be opened and allow flow in the direction you want the propellant components to go, but in this case a ‘leaky’ check valve resulted in a ‘slug’ composed of high pressure oxidizer striking a titanium component that resulted in a very violent reaction, hence the explosion.
Both Lueders and Koenigsmann noted that it was in many ways “a gift” that this happened during a ground test, because it mean that there were many high-speed cameras that could capture the incident, and it was relatively easy to comb the site and recover components to best figure out the cause of the anomaly. Koenigsmann also noted that while the team is confident in sharing these results, they are actually only approximately 80 percent the investigation and there is about 20 percent left to do in terms of figuring out additional details, mostly around the physics involved.
Koenigsmann said that SpaceX is already implementing a crucial hardware fix for this, which is to replace the check valve with a burst valve. A burst valve completely separates the oxidizer and fuel from any pressurization liquid, which will mitigate this issue and definitely “make Crew Dragon a safer vehicle,” he said.
So far this year, SpaceX has succeeded in launching an uncrewed version of its Crew Dragon 2 spacecraft to the ISS during a mission in March, and had planned to run the first crewed test mission this July, with a mission duration of two weeks. That definitely won’t occur on that timeline, and now ongoing production of Crew Dragon craft will bump back the designated machines one generation, meaning the intended Crew Dragon 1 craft meant for crewed mission flight is now Test 2, and so on.
Asked repeatedly about timeliness, neither Koenigsmann nor Lueders would offer anything concrete, but both expressed some skepticism about managing a launch by end of year, without dismissing the possibility outright.
“There’s always the chance that we’re gonna fly crew on a SpaceX vehicle this year,” Lueders said, but continued that “right now” NASA is paying attention to all the ongoing testing of various systems and “all those things need to occur before we’re gonna be confident that the system can safely fly our crew.” “I hope it’s this year,” she added.
Koenigsmann noted that this is an issue he’s fairly confident can be addressed in parallel with other things that need to be addressed with Crew Dragon before crewed flight. “I don’t think it’s impossible but it’s getting increasingly difficult, too,” he said, however, when asked directly about a crewed Dragon launch occurring before the end of 2019.
Lueders ended by expression appreciation for SapceX’s openness with NASA and its astronauts throughout this process, and Koenigsmann reinforced the superiority of the burst valve vs. the check valve it’s replacing for this application.