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Forum:Exploration: Asteroids, Moon and Mars
Topic:[SLS] RS-25 (SSME) engine tests (Stennis A-1)
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Above: This is the first of eight tests for the development engine, which will provide NASA engineers with critical data on the engine controller unit and inlet pressure conditions.

The engine controller unit, the "brain" of the engine, allows communication between the vehicle and the engine, relaying commands to the engine and transmitting data back to the vehicle. The controller also provides closed-loop management of the engine by regulating the thrust and fuel mixture ratio while monitoring the engine's health and status. The new controller will use updated hardware and software configured to operate with the new SLS avionics architecture.

"This first hot-fire test of the RS-25 engine represents a significant effort on behalf of Stennis Space Center's A-1 test team," said Ronald Rigney, RS-25 project manager at Stennis. "Our technicians and engineers have been working diligently to design, modify and activate an extremely complex and capable facility in support of RS-25 engine testing."

Testing will resume in April after upgrades are completed on the high pressure industrial water system, which provides cool water for the test facility during a hot fire test. Eight tests, totaling 3,500 seconds, are planned for the current development engine. Another development engine later will undergo 10 tests, totaling 4,500 seconds. The second test series includes the first test of new flight controllers, known as green running.

Above: A close-up view from the test stand.

The first flight test of the SLS will feature a configuration for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system. As the SLS is upgraded, it will provide an unprecedented lift capability of 130 metric tons (143 tons) to enable missions even farther into our solar system.

Robert PearlmanNASA release
Some Assembly Required: The Newest RS-25 Joins the Space Launch System Family

NASA's Space Launch System, America's new deep space exploration rocket, has a new addition to the family with the completed assembly of RS-25 Engine 2063. The RS-25 engine will power the core stage of the SLS, the launch vehicle that will take humans and cargo on deep space missions, including to an asteroid and ultimately to Mars.

Engine maker Aerojet Rocketdyne completed assembly of RS-25 Engine 2063 at NASA's Stennis Space Center near Bay St. Louis, Mississippi, 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 Exploration Mission 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.

While SLS is designed for deep space exploration far beyond Earth. 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 16 RS-25 engines in the SLS inventory are veterans of numerous space shuttle missions, where they were commonly referred to as Space Shuttle Main Engines, or SSME. Engine 2063 is one of two additional "rookie" engines without previous shuttle flight experience. Engine 2063 will undergo acceptance testing to verify it is acceptable for flight, checking out the completed system. It does include some previously flown hardware, including the four turbopumps which have flown on several shuttle missions.

"Assembly of this new engine is part of a very busy year for the RS-25 team," said Steve Wofford, manager of the SLS Liquid Engines Office at NASA's Marshall Space Flight Center, where the SLS Program is managed for the agency. "We're testing one engine, developing a new controller and planning to manufacture new engines in the future."

Engine 2063 joins a famous family with a proud tradition. The RS-25 is one of the most tested large rocket engine in history, with more than 3,000 starts and over a million seconds of total ground test and flight firing time over 135 missions.

Four RS-25 liquid propellant engines will power the SLS for the eight-minute climb to orbit with the help of two solid propellant boosters – both flight qualified components of the Space Shuttle Program and now essential to SLS's unmatched payload capability.

"Completion of this engine is a significant accomplishment, considering it's been nearly five years since the last RS-25 was assembled," said Jim Paulsen, vice president of Program Execution Advanced Space & Launch Programs Aerojet Rocketdyne. "It's been a great opportunity for the team's SSME veterans to get reacquainted with this engine. For new members of the team, it's been an invaluable introduction to this dependable 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 first SLS launch planned for 2018.

The SLS team began test firing one of the development engines with a new controller earlier this year to make sure it can meet the different performance and environmental conditions required by the SLS. The entire flight engine inventory will be upgraded with new state-of-the-art engine controllers, insulation and other details.

"There is nothing in the world that compares to this engine," added Paulsen. "It is great that we are able to adapt this advanced engine for what will be the world's most powerful rocket to usher in a new space age."

After the first four 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.

"The RS-25 is still one of the most advanced engines in the world," said Philip Benefield, himself an SSME veteran now part of the team adapting the RS-25 to SLS. "It's an interesting challenge to put together a new SLS engine team of shuttle veterans and new engineers, much like the RS-25 incorporates veteran shuttle engine hardware and new hardware to meet new requirements."

For one of those new engineers, working on the RS-25 is the high point of a life-long interest in space exploration.

"Ever since I was in the third grade when I fell in love with the space program, I have always had the desire to work on a project that would take people further into space than ever before," said Esteban Barajas, a mechanical design engineer at Aerojet Rocketdyne.

"Now, being able to bring the space shuttle main engines roaring back to life with the many talented engineers who originally designed and built them is an incredible opportunity. As a young engineer, the experience has truly been invaluable."

Robert PearlmanNASA photo release
Steamy Summer Begins for SLS with RS-25 Test

A billowing plume of steam signals a successful 450-second test of the 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.

Four RS-25 engines will power the SLS vehicle at launch, firing simultaneously to generate more than 1.6 million pounds of thrust. RS-25 engines are modified Space Shuttle Main Engines, which powered 135 successful low-Earth orbit missions.

One of the objectives being evaluated in this test 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 conditions 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; 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.

NASA engineers conducted an initial RS-25 engine test on the A-1 stand Jan. 9. 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.

See here for discussion of RS-25 engine use for the Space Launch System.

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