A SpaceX Starship rocket roared into space from Texas on Tuesday on its ninth uncrewed test launch, flying farther than the last two attempts.

The two-stage spacecraft, consisting of the Starship vessel mounted atop a towering SpaceX Super Heavy rocket booster, blasted off at about 7:36pm from the company's Starbase launch site on the Gulf Coast of Texas near Brownsville.

A live SpaceX webcast of the liftoff showed the rocketship rising from the launch tower into the early evening sky as the Super Heavy's cluster of powerful Raptor engines thundered to life in a ball of flame and billowing clouds of exhaust and water vapour.

SpaceX launched the Starship system with a previously flown Super Heavy booster for the first time, aiming to achieve a key demonstration of its reusability.

As expected, the 71m first-stage rocket separated from the upper-stage Starship vehicle several minutes after launch and headed back toward Earth.

But SpaceX controllers lost contact with the booster during its descent before it presumably plunged into the sea instead of making the controlled splashdown the company planned.

The upper-stage Starship vehicle continued to climb to space, reaching its planned suborbital trajectory about nine minutes into the flight.

In one test-flight mishap, Starship's payload doors failed to open in order to release a group of simulated satellites.

Plans called for Starship to complete its experimental flight of less than 90 minutes with a controlled descent and splashdown in the Indian Ocean.

But about a half-hour after launch, SpaceX said its flight team had lost attitude control over Starship, leaving the vehicle in a spin as it continued to head for atmospheric re-entry.

"We will not be aligned as we wanted it to be aligned for re-entry," a SpaceX commentator said during the livestream. "Our chances of making it all the way down are pretty slim."

Its last two test flights - in January and March - were cut short moments after liftoff as the vehicle blew to pieces on its ascent, raining debris over parts of the Caribbean and disrupting scores of commercial airline flights in the region.

The US Federal Aviation Administration expanded debris hazard zones around the ascent path for Tuesday's launch.

The previous back-to-back failures occurred in early test-flight phases that SpaceX had easily achieved before, dealing a striking setback to a programme that Musk, the billionaire entrepreneur who founded the rocket company in 2002, had sought to accelerate this year.

Musk is counting on Starship to fulfil 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. (Reuters)