VERNON, France (AP) — In a tightly controlled manufacturing hangar west of Paris, workers put the finishing touches on an enormous silver-colored engine. In just a few days, a similar machine will help propel the most powerful version of Europe’s Ariane 6 rocket yet, flying for the first time with four boosters.

On Thursday, the Ariane 64 rocket — named after its four boosters — is scheduled to make its maiden launch from the European spaceport in Kourou, French Guiana, aiming to deploy 32 satellites for Amazon Leo’s broadband constellation.

The flagship of Europe’s rocket industry is racing in a highly competitive environment against heavy weight players across the world, including the global market leader, Elon Musk’s SpaceX.

At ArianeGroup’s plant in Vernon, engineers design, integrate and test engines for the European heavy-lift launcher. At another site west of Paris, in Les Mureaux, the rocket’s main stage components are being carefully built and assembled.

Associated Press journalists were provided rare access to facilities placed under strict security and confidentiality rules where teams of highly-specialized workers make from space conquest a daily reality.

“It’s a special launch — something new for us on Ariane 6,” ArianeGroup Chief Technical Officer Hervé Gilibert said. This flight marks the debut of the four-booster configuration, making the rocket roughly twice as powerful as the version flown since 2024, he said.

“Don’t be surprised if you see it accelerate much more than Ariane 62, the version we have already launched five times,” Gilibert said. “It delivers significantly more power, allowing much heavier payloads to be sent into space.”

Components make trans-Atlantic journey

The launcher, its engines and avionics are built across Europe as 13 nations, members of the European Space Agency, agreed to cooperate and finance the Ariane 6 program.

“We are working with more than 600 subcontractors,” Gilibert said. “Everything comes together at two main sites — Bremen in Germany for the upper stage, and Les Mureaux in France for the lower, or main stage of the launcher.”

Ahead of Thursday’s launch, all components have crossed the Atlantic to French Guiana for final assembly. The rocket stands about 62 meters (203 feet) tall, roughly the height of a 20-story building.

“We check everything until the very last minute, and then we fly,” Gilibert said.

Once airborne, the mission will last about one hour and 50 minutes — nearly a full orbit around Earth — before the satellites are deployed in pairs from the top of the rocket. Amazon Leo’s constellation is intended to compete with SpaceX’s thousands of Starlink satellites.

The Vulcain 2.1 engine built at Vernon ignites first at liftoff.

“For a few seconds, we verify that it is functioning properly,” said Emmanuel Viallon, director of the Vernon site. “Once we are fully confident it will operate correctly for the eight minutes that follow, we ignite the solid boosters and the rocket lifts off.”

The four boosters help propel the rocket at launch, consuming 142,000 kilograms (313,056 pounds) of solid propellant in just over two minutes until they burn out.

Ariane 6, through both its launcher and engines, was designed to halve operating costs compared with its predecessor, Viallon said. Ariane 5 was last launched in 2023, concluding a program that began in the late 1970s to give Europe independent access to space.

Engines tested under near-real conditions

Engines produced in Vernon are tested on site under near-real launch conditions. Deep in the surrounding forest, reinforced structures hold the engines in place as they fire at full power, while test teams operate from underground control rooms.

Laurence, the engine firing test director at Vernon, said the full testing cycle takes two to three weeks, before the engines return to the assembly facility for final adjustments. Laurence’s last name was not disclosed for security reasons.

For the team, each launch “is always a joy, it’s always very intense,” she said. “When an engine arrives here, those are really important moments for the team. And then, seeing that the launch goes well ... that brings a great deal of gratitude.”

At Les Mureaux facility, engineers have started preparing rocket components for upcoming missions. Huge white cylinders lie horizontally to form the rocket’s main stage that is 5.4 meters (17.7 feet) wide including tanks for supercooled hydrogen and oxygen that will feed the Vulcain engine.

Caroline Arnoux, business unit director at ArianeGroup, said seven to eight launches are planned this year.

“We have a very strong order book, equivalent to about 30 launches,” Arnoux said. “Roughly one-third are institutional missions and two-thirds commercial. And our commercial customers are all waiting for the Ariane 64 version, which will be extremely important in the coming years.”

Europe's independence at stake

Ariane 64 "is an additional level of performance," Hermann Ludwig Moeller, director of the European Space Policy Institute, said. “In itself, this is an important step in the whole program, hoping to demonstrate that this configuration works as reliably as Ariane 6 has been working so far.”

The rocket’s institutional missions last year included launches of a French military reconnaissance satellite, a weather satellite, and EU-sponsored Earth-observation radar and navigation satellites.

Moeller argued there can hardly be any comparison with SpaceX, which dominates the sector with its reusable rocket model.

SpaceX “builds the rockets, builds the satellites and also sells the service” while Europe operates under a different industrial setup with separate companies responsible for launchers, satellite manufacturing and satellite operations, he said.

For Ariane 6, a key challenge will be diversifying its European customer base, which could involve a system of European preference for government missions and further development of commercial markets across the continent, Moeller argued.

Independent access to space remains the core objective of the program to “allow Europe to meet its own needs,” stressed Arnaud Demay, the Ariane 6 project manager.

ArianeGroup is also preparing for the future, working "on key technology bricks ... to enable the reuse of certain launcher components. Ideally, we would like to be able to reuse an entire stage, including the engines that powered its liftoff,” Demay said.

Demay confided he almost always cries with emotion at seeing the rocket lifting off.

“We do it so rarely, and it's so majestic when it takes off: that little touch of magic inevitably overwhelms me with emotion every time,” he said.

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Nicolas Garriga contributed to this report.

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