On 2023-03-29, during a structural qualification test of United Launch Alliance’s (ULA) Centaur V upper stage for the Vulcan Centaur launcher at NASA’s Marshall Space Flight Center in Huntsville, Alabama, an explosion blew out pieces of the stand and created a large fireball.
Some time after the event, ULA CEO Tory Bruno posted on Twitter,
Most of what you’re seeing is insulation and smaller bits from the test rig. One piece of the hydrogen tank’s dome, about a foot square, ended up a few feet away. The test article is still inside the rig and largely intact, which will significantly help with the investigation
The Vulcan Centaur for the first flight is already stacked at Space Launch Complex 41 at Cape Canaveral with a planned launch date of 2023-05-04. If the cause of the explosion is traced to the Centaur stage the launch may be delayed but if as now seems probable, it was due to a hydrogen leak on the test stand that allowed an explosive mixture of air and hydrogen to accumulate, the launch will probably go ahead as planned.