SpaceX launched the most powerful rocket ever developed — the company’s next-generation Starship — on a key test flight on Saturday that could pave the way for missions to the moon and eventually Mars.

The uncrewed test flight was mostly successful with several key milestones achieved, but SpaceX ultimately lost contact with Starship roughly 10 minutes into flight, and the spacecraft likely self-detonated due to an issue mid-flight.

The nearly 400-foot-tall Starship rocket lifted off at 8 a.m. ET from SpaceX’s Starbase test site in Boca Chica, Texas. 

Cheers erupted from SpaceX’s headquarters in Hawthorne, California, as the Starship rocket ignited and rumbled skyward.

The fate of the Starship spacecraft is not yet known, but CNBC reported that SpaceX webcaster John Insprucker said during a livestream of the event that the spacecraft’s automated flight termination system was likely triggered and the spacecraft appeared to have detonated.

It’s not yet known what could have caused SpaceX to lose contact with Starship, but the spacecraft’s flight termination system is designed to kick in if it veers off course or another major anomaly is detected.

This was only the second launch of Starship, after a first test in April ended with the rocket exploding several minutes after liftoff.

The rocket has two parts: a first-stage booster known as Super Heavy and an upper-stage Starship spacecraft.

During Saturday’s launch, the two parts of the rocket separated in flight for the first time — a major milestone for SpaceX. The company pulled off a maneuver dubbed “hot staging,” which involved igniting the Starship spacecraft’s engines while the Super Heavy booster was still partially firing. The hot-staging strategy is designed to use the spacecraft’s engines to help it separate and continue on to orbit.

After separation, the Super Heavy first-stage was meant to fall back to Earth and splash down in the Gulf of Mexico, but SpaceX reported that the booster exploded, possibly due to an anomaly. Few other details were provided at the time.

Both the Super Heavy first-stage booster and the Starship spacecraft are designed to be reusable.

The launch was a closely watched event, with high stakes for SpaceX as well as for the future of American space exploration. 

Starship is expected to play a crucial part in NASA’s efforts to return to the moon. The spacecraft was selected by the agency to carry astronauts to the lunar surface during the upcoming Artemis III mission, which could launch as early as 2025. SpaceX founder and CEO Elon Musk has also said that Starship was developed for future missions to Mars.

The rocket’s second outing followed what was a fiery and destructive debut earlier this year.

In SpaceX’s first attempt to launch Starship, the rocket exploded a few minutes after liftoff, destroying much of the infrastructure at the launch pad and causing damage to coastal wetlands and a nearby Texas state park.

The incident triggered a monthslong safety review and drew intense scrutiny over the environmental consequences of launching rockets from Boca Chica.

Earlier this week, the U.S. Federal Aviation Administration cleared SpaceX to proceed with Starship’s second launch, saying that the company has conformed to the environmental protection requirements for such operations.