Les Mureaux (France) (AFP)

At first glance, nothing looks less like an automobile than a rocket reaching more than 60 meters high, but the challenge with the future Ariane 6 is that of a real flow production chain.

Seen from the outside, nothing betrays the destination of the huge building with blind walls which extends its area of ​​three football fields on the ArianeGroup site at Les Mureaux, near Paris.

In front of a Lego model of the factory, its director Vincent Lavisse talks about "production sequences" where "everything moves at the same time".

With at the end of the immense U-shaped "chain", a container 30 meters long to accommodate in a few days the first copy of the first stage of the rocket.

From the neighboring quay, it will spin gently by the Seine to the port of Le Havre, then from there to Kourou, for the final assembly of Ariane 6. With an inaugural flight scheduled for the second quarter of 2022.

The factory has a target of maximum output of twelve units (floors) per year, twice as fast as for the first stages of Ariane 5, which the factory is close by.

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But where this production is vertical, it is done horizontally for Ariane 6. "It is less expensive", summarizes Mr. Lavisse.

- 150 tonnes of hydrogen -

Illustration with the leak test of the colossal liquid hydrogen reservoir, a cylinder about fifteen meters long, which does not tolerate any leak before filling 150 tonnes of hydrogen maintained at -250 degrees Celsius.

It is subjected to a pressure test like a vulgar inner tube.

For Ariane 5, the tank must be lowered with an overhead crane into a vertiginous well, capable of withstanding an explosion if the seal were to fail.

For Ariane 6, it is simply rolled into a factory room, isolated by a 50 tonne door.

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Everything is in the same vein.

Where men used to glue insulating plates to tanks by hand, a layer of thermal protection is now being sprayed on them.

The arc welds of the aluminum alloy plates for Ariane 5 are replaced by a "friction-knead" process, carried out with a custom-made machine which joins them "like two plasticine".

More reliable, cheaper and faster.

"All the cost savings are in the way things are done", summarizes Mathieu Chaize, Ariane 6 systems engineer, adding that here, "the industrial challenge is to create a culture of flow".

An essential asset to face ever fiercer competition on the international market for launchers, with Space X in the lead.

Same scenario in the "clean room" where engineers, wearing charlottes, circulate at the foot of the main engine of the rocket, the Vulcain 2.1.

We will eventually be able to integrate three in parallel.

- A new generation -

They are made a handful of kilometers away, in the Vernon factory, nestled in a thick forest on the hillsides of the Seine, in Normandy.

Everything has been thought of to speed up the pace by facilitating the work of men on the machines.

A 3D manipulator, a sort of robot capable of moving its 14 tons on an air cushion, firmly holds in its arms a Vulcain 2.1 which points to more than two tons.

Controlled on a touch screen tablet, it allows the engine to be oriented from all angles for easy access.

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In a large adjacent hall, it is already after Ariane 6 that is taking shape.

With the Themis project, a reusable first stage rocket demonstrator, to ensure succession by 2030.

The centerpiece is an engine, Prometheus, which will be fired for the first time by the end of the year.

70% produced in 3D printing, with the objective of costing ten times less than the Vulcain 2.1, for an equivalent power.

New fact, this future is being written by bringing together in the same space personnel from the entire chain, from designers to salespeople, including development and assembly.

Because if machines still play a great role, it is up to a new generation to bring them to life.

"We tried to put a lot of young people, so that they take power," explains Emmanuel Edeline, head of the Prometheus program, who hides his past sixty well behind an anti-covid mask.

© 2021 AFP