Vulcan Rocket Delayed After Engine Explosion During Testing

United Launch Alliance's Vulcan Centaur rocket debut is delayed to late 2023 due to an engine explosion during testing.
The explosion occurred during a BE-4 engine test for the Vulcan rocket's Centaur upper stage.
ULA is working to re-certify the Centaur stage with design modifications before the first Vulcan launch.
The Vulcan rocket needs two successful launches before it can be approved for national security missions.
The delay from the original May launch date is due to additional testing and modifications needed after the explosion.