Spaceflight Insider

RS-25 engine tested for NASA’s Space Launch System

RS-25 tested at A1

The latest development test of the RS-25 engine occurred July 29 at NASA’s Stennis Space Center. Photo Credit: NASA

After an early shutdown some two weeks ago, NASA and Aerojet Rocketdyne successfully hot-fired a development RS-25 engine. The full-duration test involved engine 0528 and lasted 650 seconds.

The engine roared to life in the afternoon of July 29 on the A-1 test stand at NASA’s Stennis Space Center in Mississippi. The RS-25, previously known as the Space Shuttle Main Engine, is being repurposed for use on the Space Launch System (SLS).

RS-25 July 14 test

The July 14 firing of the same engine, 0528, lasted only 193 seconds due to a problem with the A-1 test stand. Photo Credit: NASA

“When we send astronauts to deep space destinations, including Mars, we want them to be riding on the safest, most reliable launch vehicle, which is why we are testing the RS-25 engine under multiple scenarios to ensure America’s next heavy-lift rocket will have the performance needed to take our astronauts deeper into space,” Aerojet Rocketdyne CEO and President Eileen Drake said in a news release.

Testing is required for these engines because, even though they have flown into space before with the Space Shuttle, they will be operating in more extreme conditions.

“During the flight, the RS-25 engines will endure more heat, pressure and thrust on SLS than on the Space Shuttle,” said Jim Paulsen, vice president for NASA programs at Aerojet Rocketdyne.

Four RS-25 engines will fly at the bottom of the SLS core stage at 109 percent power level, compared to the 104.5 percent when operated on the Space Shuttle. Additionally, they will be closer to the two side-mounted Solid Rocket Boosters. On top of that, the taller core stage will result in a higher pressure on the fuel inlet system on each engine.

The firing comes after the July 14 early shutdown of the same engine. However, according to a NASA media release, that was due to a minor problem with the test stand and not the RS-25.

The test lasted about 193 seconds. According to a report by NASASpaceflight, at the recent NASA Advisory Council, NASA Exploration Systems Development Deputy Associate Administrator Bill Hill said the shutdown was due to a low-pressure indication on the line that feeds industrial water to and cools the flame trench. He said that indicated there was a leak somewhere. Teams fixed the problem earlier this week.

There are three more scheduled firings in the current series – the next scheduled for Aug. 18. According to NASA, the tests are focused on a new engine controller and higher operating parameters.

“Stennis is our go-to site to put our engines through rigorous testing; this is where we assemble and test our RS-25, RS-68 and AR1 engines,” Drake said, “Mission success is our number one priority and testing at Stennis is critical to providing the nation with next generation propulsion capabilities.”

Video courtesy of NASA Stennis


Derek Richardson is a student studying mass media with an emphasis in contemporary journalism at Washburn University in Topeka, Kansas. He is currently the managing editor of the student run newspaper, the Washburn Review. He also writes a blog, called Orbital Velocity, about the space station. His passion for space ignited when he watched space shuttle Discovery leap to space on Oct. 29, 1998. He saw his first in-person launch on July 8, 2011 when the space shuttle launched for the final time. Today, this fervor has accelerated toward orbit and shows no signs of slowing down. After dabbling in math and engineering courses in college, he soon realized that his true calling was communicating to others about space exploration and spreading that passion.

Reader Comments

I still think it is an absolute shame that these marvels of engineering will be just thrown away with each flight of the SLS.


I agree with Bruce Peters. Such beautiful marvels of engineering will have to be used repeatedly and cannot be thrown away with one flight. I think the SLS systems needs to be developed in such a way, that after reaching the required orbital height provided by this engine, the crew capsule moves ahead to its destination of Mars/Asteroids, etc. This engine housing should however return to the earth, if not to the point of launch to a different place/ platform from where it can be recovered for another use. In fact, the space shuttle was also designed in such a way that it could return to earth after a launch. In the shuttle’s case the advantage point was that it was a vehicle meant for low earth orbit, unlike SLS which will be for deep space.

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