Ariane 6 could use reusable Prometheus engine, designer says

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LES MUREAUX, France and WASHINGTON — Europe’s upcoming Ariane 6 rocket, though designed to be expendable, could one day sport a reusable engine, according to Patrick Bonguet, head of the Ariane 6 program at ArianeGroup.

Whether or not the rocket would ever use that engine, called Prometheus, depends on whether Ariane 6 manufacturer ArianeGroup, formerly Airbus Safran Launchers, finds enough benefit for the European launch sector. So far, the merits of reusable rockets to ArianeGroup are unclear at best, Bonguet said, but the company is researching the technology to be ready for implementation should it prove worthwhile.

“We could replace Vulcain 2.1 by Prometheus,” Bonguet told SpaceNews. “Or Prometheus can be the first brick to build the next generation. We will see where we are in 2025 or 2030, and then decide on the right time whether to go one way or the other.”

The Ariane 6’s maiden flight is scheduled for 2020, meaning the rocket would fly for at least five years or longer in an expendable configuration with Vulcain 2.1, a streamlined version of the Ariane 5’s Vulcain 2 liquid engine with the same performance.

ArianeGroup’s Prometheus engine received a substantial budget boost this year from the European Space Agency, which is paying the company via a fixed-price contract to build the Ariane 6 as a successor to the Ariane 5. ESA is supplying 85 million euros ($91 million) through its Future Launchers Preparatory Program, and began funding Prometheus in June.

Bonguet said ArianeGroup is studying reusability with Prometheus “in order to be sure to take the right path at the right moment.” Those efforts are mostly to prevent Europe from being caught flat-footed in the wake of other reusable launch systems, namely from SpaceX and now also Blue Origin.

Reusability is far from a primary focus, however.

“We still have not understood, would we save money by reusing? At least with our launch rate?” he asked. “We hope to launch 12 times a year. If we reuse 12 times, that means we only manufacture one time per year. It is difficult for us to have that.”

Bonguet said reusability would essentially erase the production efficiencies ArianeGroup is striving for, starving the Ariane 6 industrial base of the work upon which it relies.

A smaller tip-toe into reusability could come through salvaging Ariane 6’s payload fairings. Swiss manufacturer Ruag Space is developing reusable fairings, which Bonguet said are of interest to ArianeGroup.

“We are discussing with Ruag,” he said. “They have presented to us their concept. If it is working, and if it is bringing cost savings, we will be happy to accommodate it.”

Production value of Ariane 6

ArianeGroup is seeking a 40 percent price reduction for the Ariane 6 compared to the Ariane 5.

The biggest difference between the Ariane 5 and the Ariane 6 is the way the two rockets will be produced, Bonguet said. Compared to the Ariane 5, Europe’s Ariane 6 is factoring in production at the design stage. This includes leveraging an “extended enterprise” concept where ArianeGroup co-designs components with suppliers. Having production efficiency at the forefront of development will allow the rocket to be lower cost yet still reliable, he said.

“Ariane 6 is basically an industrialization of Ariane 5. So, it is not a brand new design. The innovations are more to make it robust to manufacture,” Bonguet said.  

ArianeGroup also gains cost savings by leveraging the combined resources of French and German rocketry expertise, which was previously stratified as Airbus and Safran. Bonguet said it is a rational step to further integrate other parts of the Ariane 6 industrial base, but ESA member states would likely reject such integration to prevent losing domestic competencies.

A third means of cost reduction and improved production efficiency is with additive manufacturing, or 3D printing. Bonguet said the Ariane 6 will likely have around a dozen 3D printed parts, compared to just one on the Ariane 5. ArianeGroup is primarily using 3D printing to streamline the production of complicated equipment that is otherwise difficult to machine. The company is also using 3D printing to create an addition to the upper stage called the Auxiliary Power Unit (APU), which is fully 3D printed, he said. The APU is a low-thrust system that enables the Vinci upper stage to drop satellites in multiple orbits for constellation deployment, and can also assist in deorbiting the stage at the end of each mission.

Maintaining schedule

Bonguet said the Ariane 6 is holding to its 2020 schedule, but ArianeGroup had to invest its own non-ESA resources into the test program to hold to that date. He didn’t label the size of the investment, but said ArianeGroup is building an additional upper stage in order to perform tests in parallel with the lower stage.

Bonguet said ArianeGroup will perform tests of the fully integrated Ariane 6 in the second half of 2019 into early 2020. In 2018, test firings will begin for the Avio-supplied strap on solid rocket boosters, he said.

ArianeGroup and Arianespace plan to overlap launches of Ariane 5 and Ariane 6 until around 2023. Bonguet said commercial demand for the Ariane 6 looks promising enough that the company is considering five launches in 2022.

Arianespace bought six more Vega and four Vega C from Avio last month, has yet to place an order for Ariane 6 rockets with ArianeGroup. To keep schedule, ArianeGroup is already buying long-lead items for the first batch.

“We have already ordered long-lead items covering up to launcher 15 already in order to be on time,” he said. “Industry is anticipating the start of production this way. We are doing this because there is an exploitation readiness key point organized by ESA and member states at the end of this year taking place in November-December, with a final outcome in March where the member states will formally endorse Arianespace with the operational role of Ariane 6.”

So far the first Ariane 6 customer is the European Commission for two Galileo launches. Bonguet said ArianeGroup is still waiting on a commitment from the European Commission to aggregate European government demand into a binding commitment for at least five Ariane 6 launches per year. This need, in order to ensure stable demand for the rocket, “is confirmed in principle,” but has yet to be confirmed in a contractual manner, he said.