Spaceflight Insider

The race to replace the RD-180 goes full throttle

United Launch Alliance Atlas V RD-180 rocket engine NASA photo posted on SpaceFlight Insider

Efforts are underway to have domestically produced rocket engines replace the Russian-made RD-180. Photo Credit: NASA

The U.S. Air Force awarded two public-private partnerships to develop a replacement for the Russian-built RD-180 engine. The first team is composed of a joint effort of United Launch Alliance (ULA) and Blue Origin. The second team is Aerojet Rocketdyne, a company that has been working for years to persuade the U.S. Air Force to back the development of the AR1 engine as a replacement.

The two teams will have until 2019 to design, build, and test the new engine for use on new launch systems such as the Vulcan. With Russia’s military actions in Ukraine, the RD-180 came under increased criticism. U.S. organizations began looking at developing their own engines.

Blue Origin BE-4 engine and man comparison

Blue Origin BE-4 engine and man comparison. Image Credit: Blue Origin

The RD-180 has been a workhorse for ULA in terms of launching the Atlas V. With the aforementioned international concerns, Congress has worked to restrict the importation of the engine.

Many solutions have been proposed including starting U.S. production of the RD-180, scaling back launches of the Atlas V to those that can only be supported by the remaining engines – or designing something new. The Air Force appears to have chosen to pursue a new engine design.

The ULA / Blue Origin team is proposing the use of the BE-4 – a liquid oxygen, liquefied natural gas (LNG) rocket engine that delivers an estimated 550,000-lbf (2.45 MN) of thrust at sea level. The engine is currently being tested at Blue Origin’s facilities located in West Texas. The rocket engine has been in development for more than four years now.

“While the RD-180 engine has been a remarkable success with more than 60 successful launches, we believe now is the right time for American investment in a domestic engine,” said Tory Bruno, ULA’s president and chief executive officer. “As America’s ride to space, we continue to meet our goal of delivering the most reliable launch systems at the most affordable cost, while developing a new rocket which enables brand new opportunities for the nation’s use of space.”

In addition to replacing the RD-180, the BE-4 is designed to power Vulcan, ULA’s next generation launch vehicle. Two BE-4s would power each ULA Vulcan booster, providing some 1,100,000-lbf (4.9 MN) of thrust at liftoff.  Vulcan will launch from Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida and Space Launch Complex 3 at Vandenberg Air Force Base in California.

Aerojet Rocketdyne was the second team selected to develop engine technology replacing the RD-180. The AR1, like the BE-4, has been in development for some time, making the Air Force’s selection of the engine as a potential replacement almost a certainty.

“This award from the U.S. government demonstrates its support of AR1 and recognizes the priority of assured access to space for our critical national security assets,” said Eileen Drake, CEO and President of Aerojet Rocketdyne. “The AR1 engine is the option with the least technical risk that allows the United States to quickly and efficiently transition off its use of Russian-supplied engines currently used on the Atlas V launch vehicle.”

The engine is touted as being developed using modern methods, which are being employed to end the use of Russian engines on Department of Defense missions.

“AR1 will return the United States to the forefront of kerosene rocket propulsion technology,” added Drake. “We are incorporating the latest advances in modern manufacturing, while capitalizing on our rich knowledge of rocket engines to produce a new, state-of-the-art engine that will end our reliance on a foreign supplier to launch our nation’s national security assets.”

Aerojet Rocketdyne's AR-1 engine. Image Credit: Aerojet Rocketdyne

Aerojet Rocketdyne’s AR-1 engine. Image Credit: Aerojet Rocketdyne

Aerojet Rocketdyne believes the liquid oxygen/kerosene-fueled AR1 to be the first engine produced in the United States to use an advanced oxidizer-rich staged combustion kerosene engine cycle.

This engine, like the BE-4, can be used on a variety of launch vehicles.

According to Drake, “This engine will be available for use on the Atlas V, Vulcan and other launch vehicles currently in development.”

Immediately after the Air Force announcement, Aerojet Rocketdyne released a statement confirming a partnership similar to ULA and Blue Origin. Aerojet Rocketdyne has with Dynetics, a Huntsville Alabama-based engineering firm, to complete development of the AR1.

“We are proud to be able to use Dynetics proven hardware fabrication capabilities and engineering expertise to join Aerojet Rocketdyne in this important endeavor”, said Steve Cook, vice president for Corporate Development at Dynetics. “Our large-scale manufacturing capabilities and extensive aerospace systems expertise, combined with Aerojet Rocketdyne’s leading rocket engine technology, offer a fast and low risk way to end U.S. reliance on Russian space launch propulsion systems.”

Under the agreement, Aerojet and Dynetics will increase their cooperation on the development of the AR1. The two companies have been working on some components of the engine design for the last 18 months. Under the agreement, Dynetics will provide support in three key areas including the AR1 engine’s main propulsion system, the ignition system and ground support equipment. Dynetics will also provide analysis support to Aerojet Rocketdyne.

“The AR1 engine is the right catalyst for moving our nation away from Russian reliance and returning America’s preeminence as a propulsion leader,” said Jim Simpson, senior vice president of Strategy and Business Development at Aerojet Rocketdyne. “Our collaboration with Dynetics in developing key AR1 components is an essential element to having a certified engine in 2019.”

The two firms have been working together to develop and test 3D printing or additive manufacturing for key components of NASA’s Space Launch System (SLS). That component will be used in the one million pound thrust booster as part of the Advanced Booster Engineering Demonstration and/or Risk Reduction (ABEDRR) contract.

Both teams have invested heavily into their engine designs. Despite financing from the Air Force, both teams will have to pay a combined $268 million. The U.S. Air Force intends to initially obligate $115.3 million. The total potential government investment, including all options, is $536 million.


Joe Latrell is a life-long avid space enthusiast having created his own rocket company in Roswell, NM in addition to other consumer space endeavors. He continues to design, build and launch his own rockets and has a passion to see the next generation excited about the opportunities of space exploration. Joe lends his experiences from the corporate and small business arenas to organizations such as Teachers In Space, Inc. He is also actively engaged in his church investing his many skills to assist this and other non-profit endeavors.

Reader Comments

On a sidenote—What’s the latest news on SpaceX and its big Raptor methane engine ? Haven’t heard much in recent months…

Dick Eagleson

There have been reports of subsystem testing at Stennis, though tests of a full-up engine are likely over a year away. Also, SpaceX got a modest USAF contract that will provide some money toward Raptor development. It was one of a series of contracts USAF awarded to pretty much every current large engine development effort in the U.S. – BE-3, BE-4, AR-1 and Raptor.

This article states that BE-4 and AR-1 will be replacements for RD-180 on Atlas V. ULA has publicly stated multiple times that neither engine will be used for Atlas V, but instead one will be used for its new Vulcan launch vehicle.

Vulcan may be the name ULA will use, but its design will almost certainly be based on Atlas V, especially if the LOX/kerosene AR-1 engine is ultimately used. Changing the name to Vulcan (instead of Atlas VI) is a public relations/perception move than an engineering decision to go with a “clean sheet” design.

Dick Eagleson

Given that liquid methane is much less dense than kerosene, ULA intends Vulcan to be much more like the Delta IV’s 5-meter diameter than the slimmer 3.8-meter Atlas V. Simply stretching the Atlas V tankage to accommodate the extra volume needed for liquid methane isn’t practical as it would make the vehicle much longer than even the comparably slim Falcon 9 which already pushes the length to diameter ratio envelope pretty hard. Doing this would also require huge and expensive modifications to the Atlas V pads and vertical payload integration structures. Making Vulcan fatter than Atlas V, rather than taller minimizes the need to modify existing launch facilities. Vulcan is also to incorporate a detachable engine module as part of the first stage. Going to a 5-meter diameter provides a lot more room to fit in an inflatable heat shield and parachutes. I am personally of the opinion that the alleged “backup” role of the AR-1 with respect to Vulcan was simply a convenient diplomatic fiction to mollify Congressional friends of AJR. ULA always intended Vulcan to fly on BE-4’s and is likely to make this unambiguously official before the end of this year. So, yeah, Vulcan is a clean sheet design. It will have no Atlas V heritage at all. The only legacy component in early Vulcan models is going to be the 5-meter version of the Centaur upper stage from the Delta IV which will serve for three or four years until the new ACES upper stage’s development is complete.

Is there a comparison of the technologies making up these engines somewhere? It would be very interesting to see.

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