BOCA CHICA, Texas (Reuters) -SpaceX's Starship rocket, designed to eventually send astronauts to the moon and beyond, completed nearly an entire test flight to space on its third try on Thursday but was destroyed during its return to Earth after making it farther than ever before.

During a live webcast of the flight, SpaceX commentators said mission control lost communications with the spacecraft during its atmospheric re-entry at hypersonic speed. The vehicle was nearing a planned splashdown in the Indian Ocean about an hour after launch from south Texas.

A few minutes later, SpaceX confirmed that the spacecraft had been "lost," presumably either burning up or coming apart during re-entry or crashing into the sea.

For reasons that were left unclear, SpaceX opted to skip one of the test flight's core objectives - an attempt to re-ignite one of Starship's Raptor engines while it coasted in a shallow orbit. That milestone is considered key to its future success.

Still, completion of many of Starship's intended flight objectives represented a milestone in the development of a spacecraft crucial to the growing satellite launch business of SpaceX, founded by Elon Musk in 2002, and NASA's moon program.

NASA chief Bill Nelson congratulated SpaceX on what he called "a successful test flight" in a statement posted on social media platform X. SpaceX President Gwynne Shotwell wrote in an X post the test marked an "incredible day."

The two-stage spacecraft, consisting of the Starship cruise vessel mounted atop its towering Super Heavy rocket booster, blasted off from the company's Starbase launch site near Boca Chica Village on the Gulf Coast of Texas. The upper-stage Starship reached peak altitudes of 145 miles (234 km).

The spacecraft far exceeded its two past performances, both of which were cut short by explosions minutes after launch. The company had acknowledged in advance a high probability that its latest flight might similarly end with the spacecraft's demise before the mission profile was finished.

SpaceX's engineering culture, considered more risk-tolerant than many of the aerospace industry's more established players, is built on a flight-testing strategy that pushes spacecraft to the point of failure, then fine-tunes improvements through frequent repetition.

ENGINEERING GOALS

Thursday's flight achieved many of the engineering goals set for the mission: a repeat of successful stage separation during initial ascent; the first test of Starship's ability to open and close its payload door in orbit; and the transfer of super-cooled rocket propellant from one tank to another during spaceflight.

What SpaceX failed to demonstrate on top of Starship's re-entry failure and the skipped engine re-ignition test was an attempt to fly the Super Heavy rocket back to Earth, part of SpaceX's routine strategy of recovering its launch boosters for re-use.

SpaceX officials have said they plan to conduct at least six more test flights of Starship this year, subject to regulatory approval.

The company is required to investigate each test mission failure and deliver its findings and corrective actions to the Federal Aviation Administration for the agency's approval before the vehicle can fly again.

On the whole, Thursday's test encompassed a fraction of the remaining demonstrations and missions the vehicle must get through before it is proven safe enough to fly people to space.

Still, Musk is counting on Starship to fulfill his goal of producing a large, multipurpose next-generation spacecraft capable of sending people and cargo to the moon later this decade, and ultimately flying to Mars.

Closer to home, Musk also sees Starship as eventually replacing the SpaceX Falcon 9 rocket as the workhorse in the company's commercial launch business. It already lofts most of the world's satellites and other payloads to low-Earth orbit.

NASA, SpaceX's biggest customer, also has a lot riding on the success of Starship, which the U.S. space agency is giving a central role in its Artemis program, successor to the Apollo missions that put astronauts on the moon for the first time more than 50 years ago.

While NASA executives have embraced Musk's frequent flight-testing approach, agency officials in recent months have made clear their desire to see greater progress with Starship's development as the United States races with China to the lunar surface.