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ULA picks an engine for its next generation rocket — just not the main one

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Aerojet’s RL10 engine during a hot-fire test
Image: Aerojet Rocketdyne

The United Launch Alliance announced today that it had picked one of the engines it plans to use to power the company’s next generation rocket, called the Vulcan. ULA has decided to go with the RL10, an engine manufactured by Aerojet Rocketdyne, to propel the Vulcan’s upper stage, the top portion of the vehicle that deploys satellites into their final orbits during launch. It’s a big hardware decision for ULA, but the company has yet to make a much more anticipated choice for the Vulcan: which will be the main engine?

The question over the Vulcan’s main engine has loomed over the company ever since it announced plans to develop the rocket in 2014. The move to create a brand new vehicle was borne out of tense geo-political relations with Russia at the time. ULA is the primary launch provider for the US government, but it relies on Russian-made rocket engines to power its main rocket, the Atlas V. And when Russia invaded Ukraine, the company faced mounting pressure to replace the engines with American-made hardware. So it decided to create a new rocket using all new engines.

But instead of picking an engine right away, ULA decided to partner with two engine manufacturers to develop potential hardware for the Vulcan. Aerojet Rocketdyne — a company with a long history of building rocket engines — has been developing the AR-1 engine for the job, while Jeff Bezos’ Blue Origin — a relative newcomer in the space industry — has been working on its own engine, the BE-4. ULA has consistently said that Blue Origin is the front-runner in the competition. The BE-4 is further along in its development, as Blue Origin has done a full-scale hot-fire test on the engine. Still, there’s no final decision on who will get the gig.

A rendering of the different parts of the Vulcan rocket
Image: ULA

In a press release regarding today’s engine selection, ULA said it plans to announce its final choice about the Vulcan’s main engine “soon.” (The Verge sent a followup email asking when that announcement would happen and just received the reply: “Soon.”) It’ll be a big deal for whoever wins. ULA is responsible for launching the majority of the US’s national security satellites, so providing the engine for the vehicle will mean having a relatively steady contract.

Meanwhile, Aerojet Rocketdyne’s hardware will at least fly in one part of the rocket thanks to today’s decision. And the pick makes sense, too. The RL10 is the engine that the company currently uses to power the upper stages on its two main rockets — the Atlas V and the Delta IV. Aerojet will be developing an upgraded version of the engine called the RL10C-X, what ULA is calling “the next generation of the RL10 family.” And it looks like Aerojet beat out at least one other competitor for this gig, though ULA won’t say the other companies that competed. It seems that Blue Origin’s smaller BE-3U engine might have been considered, according to GeekWire.

Tory Bruno, ULA’s CEO, said that the decision to choose the RL10 for the upper stage came down to price and delivery schedule. “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,” Bruno said in a statement. “We could not be more pleased to have selected the proven and reliable RL10 to power our Vulcan Centaur upper stage.”

ULA plans to fly the Vulcan for the first time in mid-2020. So a verdict on the main engine should, indeed, come “soon.”