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SpaceX Says Helium Loading Issue May Have Caused Falcon 9 Explosion (arstechnica.com)
An anonymous reader quotes a report from Ars Technica: Nearly two months after a September 1 accident on the launch pad, SpaceX says it is nearing the conclusion of its investigation. Although the company has yet to identify the "exact root cause" of the accident that occurred during a static fire test just prior to a planned launch of a communications satellite, the investigation has reached an "advanced state." Shortly after the fiery incident, the company focused on a breach in the cryogenic helium system of the rocket's upper stage liquid oxygen tank. "Attention has continued to narrow to one of the three composite over-wrapped pressure vessels (COPVs) inside the LOX tank," the company stated in an update released Friday afternoon. "Through extensive testing in Texas, SpaceX has shown that it can re-create a COPV failure entirely through helium loading conditions. These conditions are mainly affected by the temperature and pressure of the helium being loaded." SpaceX intends to continue work to identify the precise cause of the accident and to improve its method of loading helium onto the rocket to prevent a repeat failure. The company also plans to resume testing Falcon 9 rocket stages at its facility in McGregor, Texas, soon. By taking this step in early November, SpaceX maintains that it is on track to resume flight operations of its Falcon 9 rocket before the end of 2016.
Washington Post: Implication of sabotage adds intrigue to SpaceX investigation https://www.washingtonpost.com... That story was picked up all over the media.
Helium? Explosion - it is a nobel gas? I guess they mean structural failure causing a cascade of other problems.
It's not the helium exploding, no. The helium is in a high pressure container inside the liquid oxygen (LOX) tank and is supposed to be released slowly during launch to push the LOX out. If it bursts, the LOX tank can't take the pressure from both a full tank of LOX and the helium at once and will burst too. Once that happens, one spark and the LOX will burn and expand like crazy and once the kerosene (RP-1) tank is compromised it'll just be a giant ball of fire. If these helium tanks weren't super-compressed you'd need helium tanks the size of the fuel tanks which is obviously not very practical. But that also means these vessels contain extreme forces that are on the very border of what material science can offer us so it won't explode but you could absolutely call it explosive decompression.
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