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RL-10 engine test
Aerojet Rocketdyne has successfully tested a full-scale, 3-D-printed thrust chamber assembly for its workhorse RL-10 rocket engine. (Aerojet Rocketdyne Photo)

United Launch Alliance has chosen Aerojet Rocketdyne over Amazon billionaire Jeff Bezos’ Blue Origin space venture to provide the upper-stage rocket engine for its next-generation Vulcan launch vehicle.

But the suspense continues in the bigger contest to provide the more powerful first-stage engines.

Aerojet’s RL10 engine had been considered the favorite to power ULA’s Vulcan Centaur upper stage, which is to be used when the Vulcan makes its debut in 2020. For more than 50 years, the hydrogen-fueled RL10 has been a mainstay of the Centaur, which came into play most recently last weekend when it powered NASA’s Mars InSight lander out of Earth orbit.

“ULA and Aerojet Rocketdyne have a long and successful history together that began with the first flight of our Atlas and Delta rockets in the 1960s,” Tory Bruno, ULA’s president and CEO, said today in a news release. “We could not be more pleased to have selected the proven and reliable RL10 to power our Vulcan Centaur upper stage.”

Eileen Drake, Aerojet’s CEO and president, said the agreement means her company and ULA “will continue working together to extend our track record of mission success well into the future.”

Aerojet and ULA agreed to work together on a next-generation version of the RL10, known as the RL10C-X, that Drake said would “incorporate additive manufacturing and other technologies to make the engine more affordable while retaining its proven performance and reliability.”

Bruno said the key determining factors for choosing the RL10 included price and delivery schedule. The deal’s financial details were not disclosed.

Blue Origin’s BE-3U engine was the most likely alternative to the RL10. That engine is due to be used on the upper stage of Blue Origin’s New Glenn orbital-class rocket, which also has its debut set for 2020.

Aerojet is still in competition with Blue Origin to provide the Vulcan’s first-stage rocket engines, which will have to provide total liftoff thrust of more than 1 million pounds.

Blue Origin’s BE-4 rocket engine, built at the company’s headquarters in Kent, Wash., is currently ULA’s preferred choice. Two of the engines, fueled by liquefied natural gas and each capable of 550,000 pounds of thrust, would be used on the Vulcan. Blue Origin also plans to use seven of the reusable engines on its more powerful New Glenn first stage.

Aerojet is offering its kerosene-fueled, 500,000-pound-thrust AR1 engine as an alternative.

Neither of those engines has powered a rocket yet, but the BE-4 project is further along. Blue Origin has been testing the engines for months at its West Texas facility, while tests on the AR1 aren’t expected to start until next year.

At last month’s Space Symposium in Colorado, Blue Origin CEO Bob Smith told GeekWire that the engine has met all its technical requirements and is well on its way to full qualification. “At this point, we think it’s just, how do we get to the commercial production deal?” Smith said.

Today’s announcement on the upper-stage engine resolves one of the questions hanging over the Vulcan rocket project, and Bruno said in Colorado that the bigger question about the first-stage engine will be resolved “soon.”

Still more questions lie ahead: By the mid-2020s, ULA expects to introduce a completely new upper stage known as the Advanced Cryogenic Evolved Stage, or ACES.

ULA says the ACES upper stage will be capable of in-space refueling and serve as “the space transportation system for a new era of access to space.” The ACES development program could provide another opportunity for reviving the rocket engine rivalry.

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