The FAA has yet to issue a license for Space Exploration Technology Corp.’s (SpaceX) return to flight despite the company announcing it is targeting Jan. 8 for its first launch in four months.
FAA spokesman Hank Price said Jan. 3 the agency has received the mishap investigation report from SpaceX and that it is under review. A SpaceX source said Jan. 3 the FAA has not processed the company’s application for its flight license, which would allow it to fly from Vandenberg AFB, Calif., as part of an Iridium Next mission.
SpaceX has worked with officials from the FAA, the Air Force, NASA, NTSB and industry experts to determine the cause of a Falcon 9 anomaly that took place Sept. 1 at Cape Canaveral Air Force Station, Fla., causing an explosion during pre-launch activities. SpaceX said Jan. 2 an accident investigation team concluded that one of the three composite overwrapped pressure vessels (COPV) inside the second stage liquid oxygen tank failed. Specifically, the investigation team concluded the failure was likely due to the accumulation of oxygen between the COPV liner and overwrap in a void or a buckle in the liner, leading to ignition and the subsequent failure of the COPV.
SpaceX said each Falcon 9 stage uses COPVs to store cold helium, which is used to maintain tank pressure and each COPV consists of an aluminum inner liner with a carbon overwrap. The recovered COPVs showed buckles in their liners. Although buckles were not shown to burst a COPV on their own, the company said investigators concluded that super chilled liquid oxygen can pool in these buckles under the overwrap.
When pressurized, oxygen pooled in this buckle can become trapped; in turn, breaking fibers or friction can ignite oxygen in the overwrap, causing the COPV to fail. In addition, investigators determined that the loading temperature of the helium was cold enough to create solid oxygen, which exacerbates the possibility of oxygen becoming trapped as well as the likelihood of friction ignition.
SpaceX said the investigation team identified several credible causes for the COPV failure, all of which involve accumulation of super chilled liquid oxygen or solid oxygen in buckles under the overwrap. The corrective actions address all credible causes and focus on changes which avoid the conditions that led to these credible causes.
In the short term, this entails changing the COPV configuration to allow warmer temperature helium to be loaded, as well as returning helium loading operations to a prior flight-proven configuration based on operations used in over 700 successful COPV loads. In the long term, SpaceX will implement design changes to the COPVs to prevent buckles altogether, which will allow for faster loading operations.