SpaceX Plans to Resume Falcon 9 Launches
SpaceX have announced plans to resume Falcon 9 launches on January 8th. This news comes following the investigation into the pad explosion four months ago, which destroyed another Falcon 9 rocket, along with the Spacecom Amos-6 satellite. Posting an update on their website on 2nd January, SpaceX has attributed the explosion to a failure of one of the three helium tanks, known as composite overwrapped pressure vessels (COPVs), inside the liquid oxygen tank in the rocket’s second stage. The company had previously suggested that a COPV failure was a leading cause of the accident.
Each COPV consists of an aluminium liner surrounded by a carbon composite overwrap. The recovered COPVs showed buckles in their liners, however SpaceX did not identify the cause of this buckling. The company did however indicate that the buckling itself did not cause the tanks to fail; rather that these buckles created voids between the liner and composite overwrap where liquid oxygen could pool. “When pressurized, oxygen pooled in this buckle can become trapped; in turn, breaking fibers or friction can ignite the 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 (SOX), which exacerbates the possibility of oxygen becoming trapped as well as the likelihood of friction ignition,”the company stated.
In the statement, SpaceX said that investigators did not identify one single, most likely cause for the failure; instead identifying several similar credible causes, “all of which involve accumulation of super chilled [liquid oxygen] or [solid oxygen] in buckles under the overwrap.”
Further information regarding SpaceX’s return-to-flight, and indeed the changes the company will be making in preparation, can be found here http://www.spacex.com/news/2016/09/01/anomaly-updates