SpaceX now intends to continue launches with Falcon 9 spacecraft starting Jan. 8 following investigations of the pad explosion four months ago that demolished a different Falcon 9.
SpaceX posted a statement on its website on Jan. 2, explaining that the explosion was the consequence of a helium tank failure within the rocket's second-stage liquid oxygen tank.SpaceX had originally suggested that the tank failure might be the cause.
These tanks, termed composite overwrapped pressure vessels (COPV), are made with aluminum liners individually wrapped with a carbon composite.The Falcon 9's other two COPVs also showed signs of these liners buckling, and the company has yet to state what caused this.
SpaceX explained this buckling as not being responsible for the failure of the tanks; rather, they believe the buckles made voids between the composite overwrap and the liner in which liquid oxygen was able to pool.
SpaceX: "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." The helium temperature inside the COPV was also cold enough to freeze oxygen, which made the problem worse.
SpaceX's statement pointed out that investigators found no one thing that could be dubbed more responsible for the failure than anything else.
"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," SpaceX elucidated.