SpaceX's rocket has exploded just minutes after the Starship's first successful landing.
© OtherIt was thought the landing was successful but the rocket exploded shortly afterwards. Pic: SPADRE via YouTube
The rocket had soared more than six miles after taking off from Texas on Wednesday, powered through its ascent by three Raptor engines.
It descended over the Gulf of Mexico before turning upright, ready for landing.
Unlike two previous test flights, which crashed to earth, the prototype of Elon Musk's Mars rocket was still intact when it landed.
John Insprucker, who was commenting over SpaceX's live feed of the launch, was encouraged enough to say: "Third time's a charm, as the saying goes".
But, having declared the test a success, the rocket exploded and was hurled into the air before hitting the ground in flames.
SpaceX did not say what the problem was but Mr Musk was focusing on the positive: This was the first time Starship had landed safely after a high-altitude flight.
© OtherElon Musk said: "RIP SN10, honourable discharge". Pic: SPADRE via YouTube
The entrepreneur wrote on Twitter: "Starship 10 landed in one piece! RIP SN10, honourable discharge".
He added that the SpaceX team was "doing great work", saying: "One day, the true measure of success will be that Starship flights are commonplace".
Starship and launch vehicle Super Heavy were unveiled by Musk in 2019.
The rocket is designed to carry a crew and cargo "to the moon, Mars or anywhere else in the solar system" and land back on Earth perpendicularly instead of horizontally, Mr Musk has previously said.
But the first two tests crashed and exploded in December and February.