THE WORLDs largest rocket has flown again, and the uncrewed test flight on March 14th, like the two previous ones, ended in rapid unscheduled disassembly (ie, catastrophic explosions). But the upper stage of Starship, built by SpaceX, Elon Musks rocket company, reached orbit for the first time and completed several test operations before being destroyed while re-entering Earths atmosphere. In a defiant post on X, the social network formerly known as Twitter, Mr Musk insisted that Starship will make life multiplanetary. This latest flight was one small step in that direction.

Starship is in fact two vehicles: the Super Heavy booster stage, a behemoth 71 metres tall, and the 50-metre Starship upper stage, which separates from the booster at an altitude of around 70km (44 miles) to proceed to orbit. The combined vehicles first test flight, in April 2023, ended roughly four minutes after lift-off, with the self-destruction of the entire spacecraft, after stage-separation failed and the rocket began to corkscrew erratically. During the second test flight, in November, the Starship upper stage successfully separated from the booster around three minutes into the flight, and continued to fly for another eight minutes, reaching an altitude of 149km. But both vehicles then suffered failures that led to their rapid unscheduled disassembly.

The third flight, once again from SpaceXs Starbase facility near Boca Chica in Texas, also led to the loss of both vehicles. But this time the upper stage reached orbit, at an altitude of 230km. SpaceXs aim is that both vehicles should eventually be fully reusable, flying back to Earth to land, as its Falcon 9 boosters already do. For these initial test flights, however, its plan has been for the Super Heavy booster to practise a soft splashdown at sea, slowing its descent using rocket engines before slipping beneath the waves, while the Starship, journey completed, then makes a hard splashdown (ie, falls into the sea from a great height).

Even these more limited goals have proved over-ambitious. In Novembers test flight, the Super Heavy booster exploded when it attempted to reignite its engines in preparation for splashdown. This time around, the reignition of its engines seems to have failed once again, leading to a hard splashdown in the Gulf of Mexico.

The Starship, however, reached a low-Earth orbit that took it across southern Africa. While in this so-called coast phase, it carried out a series of test operations: opening and closing its payload door (Starship will ultimately be able to carry as much as 150 tonnes of payload into orbit); transfering propellant between two on-board tanks (a warm-up for future Starship-to-Starship refuelling in orbit, a requirement for missions to the Moon and Mars); and, finally, attempting a controlled re-entry. On-board cameras showed the glowing pink plasma expected of a spacecraft re-entering the atmosphere. But contact was lost soon afterwards, and SpaceX announced that the vehicle had been destroyed. (Whether this was because of a failure of its heat-shielding tiles, loss of control of the Starship or some other reason is unclear.)

SpaceX has been mocked for the tendency of its test flights to end in expensive firework shows, but such criticism misunderstands the companys approach to rocket development. It prefers to iterate quickly and learn from failure, rather than painstakingly plan for a perfect launchwhich, in the rocket industry, almost never happens (as the loss of the Kairos rocket launched by Space One, a Japanese company, on its inaugural flight on March 13th, demonstrated). And a successful maiden flight is particularly unlikely for a system as complex as Starship, the largest rocket ever built, which is intended to carry humans to other worlds. Each of these flight tests continue to be just that: a test, SpaceX explained in a statement before the launch. They arent occurring in a lab or on a test stand, but are putting flight hardware in a flight environment to maximise learning.

This less risk-averse approach has undoubtedly enabled SpaceX to outpace its rivals in the industry; last year its Falcon 9 rockets flew more missions and launched more mass into orbit than did those of any other company or space agency. A more valid criticism of SpaceX is that it has cut corners in areas such as environmental protection. The first Starship test flight, last April, caused extensive damage to its launchpad, scattering debris over a wide area, and prompting the Federal Aviation Authority, which regulates rocket launches, to conduct a safety review. SpaceX has since upgraded its launchpad with a flame deflector system that sprays water beneath the rocket as it takes off, to reduce noise, heat and damage.

And while SpaceX may be making rapid progress by spacefaring standards, Starship development is taking longer than expected. The work is partly funded by NASA, Americas space agency, and is critical to its plans to return humans to the Moon later this decade. A lunar landing by astronauts in a Starship vehicle, as part of the Artemis programme, once planned for 2025, has been delayed to 2026. And even that looks like a stretch given that Starship has yet to fly successfully, let alone with humans on board.

Mr Musk has said that he hopes Starship will make at least six more flights this year. That is just about plausible, even allowing for his infamous over-confidence. But Mr Musk also says that he wants Starship to have completed hundreds of uncrewed launches, carrying satellites into orbit, before it carries astronauts. The paradox of SpaceXs approach to rocket development is that it is both faster than any of its competitors, and also slower than NASA needs. But whatever its speed of travel, SpaceX has just taken its next step towards the stars.

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Elon Musk's Starship reaches orbit on its third attempt - The Economist