SpaceX Closes In On Cause of Falcon 9 Launch Pad Disaster

Credit: U.S. Launch Report

Credit: U.S. Launch Report

With the highly anticipated introduction of its next generation super heavy lift launch system just days away, SpaceX has shed a little more light on what went badly wrong with its current Falcon 9 workhorse during pre-launch preparations for the Amos-6 satellite mission three weeks ago.

In an anomaly update posted to its website on September 23rd, SpaceX says “preliminary review of the data and debris suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place. All plausible causes are being tracked in an extensive fault tree and carefully investigated.”

One of the most critical facts to be determined is whether or not this “anomaly” has any relation to the 2015 CRS-7 in-flight accident which was ultimately traced to a faulty strut supporting a high pressure helium tank in the Falcon 9’s second stage. Given the exhaustive analysis of the Falcon 9 vehicle following that incident, any determination that another, interconnected  flaw was somehow overlooked could be particularly devastating to the company’s reputation as it is still seeking to secure a place in the national security launch business, where there is less tolerance for failure than in the overall commercial market. On this point SpaceX seems clear, stating “through the fault tree and data review process, we have exonerated any connection with last year’s CRS-7 mishap.”

With an accident investigation team (AIT) comprised of members from NASA, the Air Force, aerospace industry professionals and of course the company itself, this finding likely comes as some relief, even as the actual cause of the conflagration which destroyed the rocket, the satellite and much of the transporter/erector remains elusive and is still a cause of great concern. The statement appears to strongly suggest that the problem was in the rocket itself, rather than in the ground equipment which services it, a finding which could delay a return to flight the company hopes could take place in November.

The effort to determine the cause of what company founder Elon Musk has characterized as the most difficult investigation SpaceX has ever faced is focused on an astonishingly brief moment in time. According to the update, the AIT is “scouring through approximately 3,000 channels of engineering data along with video, audio and imagery. The timeline of the event is extremely short – from first signs of an anomaly to loss of data is about 93 milliseconds or less than 1/10th of a second.”

SpaceX uses composite overwrapped pressure vessels, or COPVs, mounted within the liquid oxygen tank to provide helium for the initial spin of the Falcon 9’s turbo-pumps and to bring the rocket’s tanks to flight pressure. Mounting the helium COPV’s within the much larger liquid oxygen tanks helps maintain cold temperatures and saves weight, but it is design with some drawbacks as well. The helium pressurization system has at times been a considerable point of difficulty for SpaceX, leading to a number of flight delays earlier in the Falcon 9’s history, prompting Musk to describe it as a “pesky little molecule.” With the wording of Friday’s statement somewhat ambiguous, it is unclear whether or not the investigation is focusing on the rupture of a single tank, or another element in the system.

Posted in: SpaceX

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