The damage caused will likely take several months to repair. They could thus delay the next test flights, and therefore the development of this rocket on which NASA is quickly counting to send its astronauts back to the Moon.

Before Thursday's test flight, SpaceX boss Elon Musk's only wish was "not to destroy the launch pad." His fear: that the rocket would explode before it even tore itself off the ground -- which it finally did after four minutes of flight, over the sea.

But the company seems to have underestimated the damage that a simple take-off of this 120-meter-high behemoth could cause.

"The engines, when they ignited, may have broken the concrete, rather than just eroded it," Elon Musk tweeted Saturday.

The gigantic launch tower held the shock. The huge base on which the vehicle rests (launch table) is also still there, even if it has been damaged.

But under it, a deep crater was dug out, according to images posted by specialists on social networks.

The cloud of dust and debris thrown by the first liftoff of Starship, SpaceX's new rocket, on April 20 at Starbase in Texas © Patrick T. Fallon / AFP

All around reigns a landscape of desolation, noted an AFP photographer. During liftoff, a shower of debris was catapulted into the nearby sea, shows a video from SpaceX. A cloud of dust reached a small town several kilometers away, according to local press.

Not ready in time

"The radius of debris and nuisance was probably larger than anyone had anticipated," Olivier de Weck, a professor in MIT's department of aeronautics and astronautics, told AFP.

"The main damage to the launch pad is below, where the flames (of the engines) attack the ground," said de Weck, several of whose former students work for SpaceX. "The crater that was created is going to have to be filled and repaired, and it's certainly going to take several months."

The Starship launch pad did not appear to be equipped with two infrastructures typically used for heavy launchers.

A crater carved by the liftoff of Starship, the world's largest rocket, developed by SpaceX, at Starbase in Texas on April 22, 2023 © Patrick T. Fallon / AFP

First, a "deluge": phenomenal quantities of water spilled at the precise moment of ignition of the engines, in order to attenuate the acoustic waves, limiting the vibrations.

Then, a "jet deflector" (or flues): a system of tunnels to redirect the emitted gases, protecting both the concrete and the rocket.

But building them is extremely expensive, especially since they have to be adapted to the size of the rocket -- disproportionate in the case of Starship.

After the test, Elon Musk explained that the company had begun building "a water-cooled steel plate" to be placed under the base of the rocket, ultimately not "ready in time".

The company "mistakenly" thought the launch pad would withstand the test, he acknowledged, adding that a new takeoff would probably be possible "in one or two months".

Reinforce

Such a steel plate "would make sense, I think it will work," Philip Metzger, a former NASA employee who worked on launch pad physics, told AFP. Dousing it with water would prevent the plaque from "melting," he explained.

It wouldn't solve the problem of acoustic waves, but "you can build a rocket strong enough to withstand it," said the scientist at the University of Central Florida.

A piece of metal near the launch pad of Starship, SpaceX's new rocket, on April 22, 2023 in Texas, two days after its first liftoff © Patrick T. Fallon / AFP

Designing a launch pad is as complex as developing a rocket, he said.

NASA's new mega-rocket, SLS, which took off for the first time in November from Florida, also caused damage, including knocking out the elevators of its launch tower.

Before it can fly again, in addition to strengthening its launch pad, SpaceX will have to determine the cause of the problems encountered in flight. Several engines did not work, and the two stages of the rocket did not separate as planned, forcing SpaceX to activate the self-destruct command.

Finally, it will be necessary to convince the air regulator, the FAA, to authorize Starship to take off again, noted Olivier de Weck. The agency confirmed that the test on Thursday did not cause any injuries, and said it was overseeing the investigation into the blast. She assured that a new test flight would be conditional on public safety.

Counterintuitively, this first test remains "more of a success than a failure," according to de Weck. "SpaceX is able to develop these incredible capabilities, because they're willing to take risks and break things -- but they're learning from them."

© 2023 AFP