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| Science & Technology |
| SpaceX and NASA detail cause of Dragon test failure, crewed flight this year looks ‘increasingly difficult’ |
| 2019-07-16 |
| [TechCrunch] 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” that occurred during the test was the result of oxidizer mixing with the helium component of the SuperDraco rocket engine propellant system at very high pressure. On April 20, SpaceX held an abort engine test for a prototype of its Crew Dragon vehicle (which had been flown previously for the uncrewed ISS mission). Crew Dragon is designed to be the first crew-carrying SpaceX spacecraft, and is undergoing a number of tests to prove to NASA its flight-readiness. After the first few tests proved successful, the test encountered a failure that was instantly visible, 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, Fla. SpaceX VP 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 there were 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 that can be opened to 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 caused a very violent reaction. Both Lueders and Koenigsmann noted that it was in many ways “a gift” that this happened during a ground test because there were many high-speed cameras to 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% through the investigation and there is about 20% 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. |
| Posted by:3dc |