Elon Musk's SpaceX saw mixed results in the latest test launch of its Starship mega-rocket on Thursday, successfully catching the massive booster but with the upper stage failing for the second consecutive time.

Minutes after lift-off and booster separation, a video live feed showed the upper stage tumbling uncontrollably, with signal soon cutting out.

"Can confirm we did lose contact with the ship. Unfortunately, this happened last time, too," SpaceX official Dan Huot said, alluding to the January launch that saw the upper stage explode over the Caribbean, raining debris.

The new setback could fuel questions over Musk's attention to his space company, as the billionaire spends most of his time in Washington leading US President Donald Trump's government overhaul efforts.

That work has also prompted mounted scrutiny over Musk's influence on the US government space program.

Starship, the world's biggest and most powerful launch vehicle, successfully blasted off from SpaceX's Starbase facility in Boca Chica, Texas shortly after 5:30 pm local time.

It was Starship's eighth orbital mission - all so far uncrewed - and the first since its dramatic mid-air explosion over the Caribbean during its last trial.

Despite losing contact with the upper stage again, SpaceX managed to return the huge booster stage to the launch tower - catching it with arms called "chopsticks." It was the third time SpaceX completed the tricky engineering feat.

About 40 minutes after the launch, Spacex turned off its livestream and the fate of the errant upper stage was not immediately known. (AFP)