Blue Origin's giant New Glenn rocket exploded on Thursday night during a hot-fire test on the launchpad, lighting up the skies around the launch site in Cape Canaveral, Florida. In a post on X, Blue Origin founder Jeff Bezos said that all personnel had been accounted for.

“It’s too early to know the root cause, but we’re already working to find it,” Bezos wrote . “Very rough day, but we’ll rebuild whatever needs rebuilding and get back to flying. It’s worth it.”

What Is a Hot-Fire Test?

The test during which Blue Origin’s rocket—a vehicle that, at 98 meters tall, is one of the largest ever built—exploded is known as a hot-fire test, or static-fire test. Essentially, it is a standard procedure carried out on the engines of a rocket, spacecraft, or prototype in which the engines are ignited for a very short period of time and then shut down while the vehicle remains secured to the launchpad.…