SpaceX launched its huge Starship rocket into space from a south Texas launch pad Saturday morning. It lifted off into sunny skies at 7:06 a.m CST and was scheduled to splash down in the Pacific Ocean off the island of Kauai. That didn’t happen.

The rocket’s Super Heavy second stage booster exploded after it successfully separated from the Starship upper stage. That upper stage contained the capsule that would carry astronauts and was able to fly briefly. But SpaceX lost contact and intentionally exploded it, because communication would have been necessary for a successful return of Starship to earth.

“We have lost the data from the second stage … what we do believe right now is that the Automated Flight Termination System on the second stage appears to have triggered very late in the burn,” John Insprucker, SpaceX principal integration engineer, said on the company’s webcast.

SpaceX said the goal of this second flight test was to separate the rocket’s stages cleanly in space and that did happen. “Any and all data is going to be incredibly useful,” a SpaceX announcer said during the broadcast.

The rocket is 394 feet tall compared to NASA’s 363-foot-tall Saturn 5 and is a key part of SpaceX owner Elon Musk’s vision of making humans a multiplanetary species. It is designed to be reusable. NASA is also relying on Starship as part of its plan to return astronauts to the lunar surface.

Tech billionaire Elon Musk is the founder, chairman, CEO and chief technology officer of SpaceX. He is also CEO of the electric vehicle manufacturer Tesla and the owner of X (formerly Twitter).