A former Space Shuttle Main Engine (SSME), that never gained the honor of pushing a Space Shuttle into orbit, has completed an important role that is part of the preparations to launch the Shuttle’s successor. RS-25 Engine 0525 completed its seventh static fire at the Stennis Space Center on Thursday and will now be replaced by flight engine 2059 on the A-1 Test Stand for the next test series.
SLS RS-25 Test:
NASA’s Space Launch System (SLS) Program plans on continuing high-tempo testing of Aerojet Rocketdyne RS-25 engines at Stennis Space Center through next year in preparation for the SLS vehicle’s first flight planned in 2018.
Previously known as the Space Shuttle Main Engine (SSME), RS-25 testing resumed in January with development engine 0525 in the A-1 test stand at Stennis.
Engine 0525 never flew in space, as it was one of two development engines used for component testing on Stand A-2 to support shuttle flights – 0528 was the second development engine.
The tests are designed to validate a new engine controller and how the RS-25 engine design functions in the SLS operating environment, which has functional and environmental differences from the Space Shuttle.
It has been a speedy turnaround of the test stand by the test control team at Stennis – which completed the sixth test in on August 13, ahead of Thursday’s final test in the series.
While the data from test six was reviewed, crews inspected the engine and the A-1 test stand and performing any maintenance that was necessary to make sure they are ready for the final firing of E0525.
“The first thing we do (is) dry the engine right away after we test, so there will be a day’s worth of drying the engine,” noted Nyla Trumbach, NASA Test Operations Engineer at Stennis.
Heated nitrogen gas is used to dry out the engine after shutdown.
“After that, we have to perform certain leak checks on the engine, we’ll replace instrumentation that’s gone out of (calibration) on the facility, (and) perform any maintenance on the stand that needs to be done.
“The main thing to do before the next test (is) to perform (a) Flight Readiness Test; that’s where we take the test profile for that test (and) we actually input the set points and run the engine software along with the facility to make sure they both behave.”
NASA has sixteen RS-25 flight engines, most of which were used for Shuttle flights, and two development engines used in ground development testing for both the Space Shuttle Program and now SLS.
Following this final test in the current test series, engine 0525 will be replaced in the A-1 facility with flight engine 2059.
Engine 2059 is a veteran, having helped power five Space Shuttles into space, flying three times on Shuttle Orbiter Atlantis (STS-117, STS-122, and STS-125) and twice on Orbiter Endeavour’s last two flights (STS-130 and STS-134).
The engine flew all five flights installed in the center or number one position. It was the last flight engine to be shipped from the Kennedy Space Center to Stennis, arriving in April, 2012.
Ronnie Rigney, RS-25 Test Program Manager at Stennis, noted that the engine has a known specific impulse (Isp) and firing it in the modified test stand will help to calibrate how A-1 measures engine performance.
“We did some extensive modifications to the test stand, so we’ve kind of got a new test stand in that sense,” added Steve Wofford, manager of the SLS Liquid Engines Office at Marshall Space Flight Center in Alabama.
“So we’re going to run an existing flight engine that we have good green run data from and good flight data from before, so that we can get a comparison to isolate those changes in the test stand, so that we can do an ‘apples-to-apples’ comparison.”
The calibration test run with engine 2059 is currently targeted for the November time-frame. After the calibration run, the first of the two new flight engines will be acceptance tested.
Engines 2062 and 2063 have not been flown or fired before, so they will both be “green run” at Stennis prior to flight; both are currently assigned to fly on the second Core Stage. Engine 2063 will go first, with that test currently targeted for the February time-frame.
Following the green run on engine 2063 early next year, a second development test series of ten tests will be conducted using the other development engine, number 0528. Finally, engine 2062 will get its green run currently forecast for the November 2016 time-frame.
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