Definition
A subtle but catastrophic failure mode of the Composite Overwrapped Pressure Vessels (COPVs) used in Falcon 9 upper stages, where super-chilled liquid oxygen becomes trapped and auto-ignites due to the structural buckling of the tank’s inner liner.
Why It Matters
It serves as a reminder that even ‘compatible’ materials can fail catastrophically when pushed into extreme, novel physical environments.
Core Concepts
- COPV Structure: An inner aluminum liner wrapped with carbon fiber for strength.
- Buckling Mechanism: Rapid loading of high-pressure helium during the final minutes of the countdown made the aluminum liner hot. When submerged in super-chilled liquid oxygen (–340°F), the thermal differential caused the liner to “buckle” or wrinkle.
- Auto-Ignition: Super-chilled LOX pooled in these tiny buckles. As the COPV continued to be pressurized, the pooled oxygen was crushed between the liner and the carbon fiber. The combination of friction and high pressure caused the oxygen to solidify and then spontaneously ignite.
- The “Smoking Gun”: Replicated in McGregor in late 2016, where cameras inside a test tank recorded a COPV exploding as super-chilled oxygen pooling occurred.