Steamy Summer Begins For SLS With RS-25 Test

Image Credit: NASA

Image Credit: NASA

May 29, 2015 – A billowing plume of steam signaled a successful 450-second test of the Aerojet Rocketdyne RS-25 rocket engine May 28 at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. The hotfire test was conducted on the historic A-1 Test Stand where Apollo Program rocket stages and Space Shuttle Program main engines also were tested.

RS-25 engines tested on the stand will power the core stage of NASA’s new rocket, the Space Launch System (SLS), which is being developed to carry humans deeper into space than ever before. The heavy-lift SLS will be more powerful than any current rocket and will be the centerpiece of the nation’s next era of space exploration, carrying humans to an asteroid and eventually to Mars.

While SLS is designed for deep space exploration, it’s also designed to take advantage of the investments the nation has already made in space exploration, including the RS-25. Fourteen of the sixteen RS-25 engines currently in the SLS inventory are modified Space Shuttle Main Engines (SSME), which powered 135 successful low-Earth orbit missions.

NASA engineers conducted an initial RS-25 engine test on the A-1 stand on January 9, 2015. Testing then was put on hold for scheduled work on the Stennis facility high-pressure industrial water system that provides the tens of thousands of gallons of water needed to cool the stand during an engine test. RS-25 testing now is set to continue through the summer.

Aerojet Rocketdyne technicians put the final touches on the 16th engine for the RS-25 program. This engine will join three others to help propel the nation’s most powerful rocket, the Space Launch System, which is currently in-development by NASA. Image credit: Aerojet Rocketdyne

Aerojet Rocketdyne technicians put the final touches on the 16th engine for the RS-25 program. This engine will join three others to help propel the nation’s most powerful rocket, the Space Launch System, which is currently in-development by NASA. Image credit: Aerojet Rocketdyne

Aerojet Rocketdyne recently completed assembly of the RS-25 Engine 2063, after approximately three months of work. The new engine becomes the 16th assembled RS-25 flight engine in inventory for SLS flights. It will be one of four RS-25s used to power Orion Exploration Mission-2 (EM-2), the second SLS launch targeted for the 2021 time frame. Testing of these four engines will begin later this year as work accelerates on NASA’s newest launch vehicle.

The SLS will be bigger than previous rockets and fly unprecedented missions, and its engines will have to perform in new ways. Tests at Stennis will ensure the new controller and engine are in sync and can deliver the required performance to meet the SLS requirements. The entire flight engine inventory will be upgraded with new state-of-the-art engine controllers, insulation and other details.

One of the objectives evaluated in these tests is the new engine controller, or “brain.” The RS-25 is unique among many engines in that it automatically runs through its cycles and programs. The controller monitors the engine condition and communicates the performance needs. The performance specifications, such as what percentage of thrust is needed and when, are programmed into the controller before the engines are fired. For example, if the engine is required to cycle up to 90 percent thrust, the controller monitors the fuel mixture ratio and regulates the thrust accordingly. It is essential that the controller communicates clearly with the engine.

Four previously flown RS-25s will be attached to the first SLS core stage and test fired together as a stage before being approved for the expected 2018 SLS test launch.

Four RS-25 engines, propulsion system ducting and an RL10 upper stage engine, designed and built by Aerojet Rocketdyne, will power the SLS core stage. Aerojet Rocketdyne will also be supplying the propulsion products for nearly every component of the Orion spacecraft that is being built by Lockheed Martin in Littleton, Colorado. The Orion spacecraft will launch aboard the SLS. Exploration Mission-1 (EM-1) will launch an uncrewed Orion spacecraft to a stable orbit beyond the moon and bring it back to Earth to demonstrate the integrated system performance of the SLS rocket and Orion spacecraft.

After the first four SLS flights, NASA will start using brand new RS-25 engines. These “next generation” engines will be more affordable by utilizing components made with the latest 21st century electronics, cost-saving manufacturing techniques and more cost effective materials.

In this two-minute time-lapse video, see how a powerhouse of a rocket engine, the RS-25, is assembled at NASA’s Stennis Space Center near Bay St. Louis, Mississippi. Four RS-25 engines will power NASA’s new rocket, the Space Launch System, on missions to deep space, including to an asteroid and ultimately to Mars.
Credits: Aerojet Rocketdyne