Spaceflight Insider

Aerojet Rocketdyne starts off a busy 2018 with hot fire of RS-25 engine

Archive image of prior RS-25 test, Feb. 22, 2017 , Shown from the viewpoint of an overhead drone. Photo Credit: KSC Unmanned Aerial Systems Team

Archive image of prior RS-25 test, Feb. 22, 2017 , Shown from the viewpoint of an overhead drone. Photo Credit: KSC Unmanned Aerial Systems Team

NASA and Aerojet Rocketdyne conducted another successful test firing of the Space Launch System’s core stage main engine, the RS-25, on Jan 16 2018.

The 14 foot (4 meter) tall engine was attached to NASA’s Stennis Space Center’s A-1 test stand where it was hot fired for six minutes and five seconds. When propelling the SLS on its missions to the Moon and beyond, these engines are planned to fire for about eight and half minutes. This marks the second successful test for the engine in just over a month with a six minute and 40 second firing having occurred on Dec. 13 2017.

RS-25 Space Shuttle Main Engines at Kennedy Space Center in Florida Photo Credit Jason Rhian SpaceFlight Insider

RS-25 rocket engines at NASA’s Kennedy Space Center in Florida. Photo Credit: Jason Rhian / SpaceFlight Insider

“Aerojet Rocketdyne is playing a vital role in the nation’s effort to expand the frontiers of humankind. This test is the latest example of our steady progress, not only toward EM-2 but also toward putting the nation’s exploration program on a sustainable path for the future,” said Eileen Drake, Aerojet Rocketdyne’s CEO and president via a company-issued release.

This particular test qualified the engine controller that will be used on the third engine of the second planned flight of the SLS (EM-2), currently scheduled to be a crewed trip around the Moon. The SLS main core is designed to use four RS-25 engines producing just over 2 million pounds of thrust paired with two 5 segment Solid Rocket Boosters (SRBs – produced by Orbital ATK) propelling it at liftoff.

The RS-25 engine is fueled by a mixture of Liquid Hydrogen (LH2) and Liquid Oxygen (LOX), earlier versions of the engine helped power NASA’s now-retired fleet of Space Shuttle orbiters off the pad for more than 30 years.

A total of 16 Space Shuttle Main Engines are being upgraded for use on the SLS. Improvements to the engine include a new controller, which is  essentially the engine’s brain. With substantially increased processing power and a decrease in weight, the engine controller is being prepared to be ready to take SLS through its first flights. In addition, engine thrust has been increased by 21,000 pounds to a total of 512,000 pounds.

Unlike with the shuttle, where the engines were reused, the SLS engines will be single-use as the core stage will not be recovered.

This test also marked the second successful demonstration of the pogo accumulator assembly, which is designed to dampen vibrations that could result in stability issues during flight. The pogo accumulator is NASA’s largest additive manufactured (3-D-printed) rocket engine component used in the retooled RS-25.

Additive manufacturing is planned to play a key role in Aerojet Rocketdyne’s efforts to reduce the production costs of future versions of the RS-25 by as much as 30 percent.

More testing of the RS-25 is scheduled to be conducted this year to test components and to qualify more of the new flight controllers so they are ready for future SLS missions.

“We ended 2017 with a successful engine test in December and have now maintained that momentum into 2018,” said Dan Adamski, RS-25 program director at Aerojet Rocketdyne. “Future testing this year will continue to add to the program’s inventory of flight controllers and will bring additional development hardware into the test program to demonstrate design, manufacturing and affordability improvements. Our pogo accumulator assembly is just one of the first of these efforts to be hot-fire tested.”

The first flight of the Space Launch System, Exploration Mission 1, is currently scheduled for some time in 2019 will be an uncrewed flight to the Moon.

Video courtesy of NASA Stennis




Lloyd Campbell’s first interest in space began when he was a very young boy in the 1960s with NASA’s Gemini and Apollo programs. That passion continued in the early 1970s with our continued exploration of our Moon, and was renewed by the Shuttle Program. Having attended the launch of Space Shuttle Discovery on its final two missions, STS-131, and STS-133, he began to do more social networking on space and that developed into writing more in-depth articles. Since then he’s attended the launch of the Mars Science Laboratory Curiosity rover, the agency’s new crew-rated Orion spacecraft on Exploration Flight Test 1, and multiple other uncrewed launches. In addition to writing, Lloyd has also been doing more photography of launches and aviation. He enjoys all aspects of space exploration, both human, and robotic, but his primary passions lie with human exploration and the vehicles, rockets, and other technologies that allow humanity to explore space.

Reader Comments

Douglas Fingles

I am curious why a live test is required to certify a particular controller. Wouldn’t it be simpler, cheaper, and faster to create a test box to simulate inputs and see how the controller reacts in a similar environment (noise/heat/vibration, etc)?
Run the controllers through the test box and certify for use when/if they pass. Then, I assume, the SLS will have a hot-fire check at some point, that’s when a live feed will be recorded for the propulsion gurus to verify the controller did what it was supposed to.

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