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NASA Continues to Gather Data with RS-25 Engine Developmental Test

A test of RS-25 engine No. 0528 on July 14
A team of NASA, Aerojet Rocketdyne and Syncom Space Services engineers and operations conducted a test of RS-25 engine No. 0528 on July 14 on the A-1 Test Stand at Stennis Space Center. The test fell short of its scheduled 650 seconds. Initiated at 5:57 p.m. (CST), there was a minor issue with the test stand that triggered an early shutdown 193 seconds into the test. Facility control systems in place responded properly by shutting down the test in an orderly fashion. No issues were reported with the engine, and the next test is planned for August. Credits: NASA/SSC

NASA continues to gather performance data with the July 14 test fire of the RS-25 engine at NASA’s Stennis Space Center in Mississippi that will provide core stage power for the agency’s new Space Launch System (SLS).

Initiated at 5:57 p.m. (CST), a minor issue with the test stand triggered an early shutdown 193 seconds into the test, scheduled for 650 seconds. Facility control systems in place responded properly by shutting down the test in an orderly fashion. No issues were reported with the engine, and the next test is planned for August.

Even with the early shutdown, the test will provide valuable performance data on the new engine controller and operating parameters needed for launch of the SLS. The SLS Program, Stennis and Aerojet Rocketdyne will work to determine if missed development points can be added to one of the four future tests in the series.

The test of RS-25 developmental engine No. 0528 on the A-1 Test Stand was conducted by a team of NASA, Aerojet Rocketdyne and Syncom Space Services engineers and operators. Aerojet Rocketdyne is the prime contractor for the RS-25 engines. Syncom Space Services is the prime contractor for Stennis facilities and operations.

“The RS-25 is a proven engine, but the SLS will demand it to operate at higher levels than ever before,” Stennis Space Center Director Rick Gilbrech said. “Despite the early shutdown in this instance, the testing we’re doing is proving its capabilities and allowing us to move forward with confidence. Every test is a step closer to powering missions deeper into space than we’ve ever flown. It’s exciting to be a part of that progress.”

RS-25 engines are upgraded versions of the main engines used to power 135 space shuttle missions from 1981 to 2011. The RS-25 engines for initial SLS flights are flight engines remaining from the Space Shuttle Program. The engines were all built for NASA by Aerojet Rocketdyne and are among the most proven in the world, having logged more than 1 million seconds of hot fire time during ground tests and missions. In addition to the upgraded space shuttle main engines, NASA also has contracted with Aerojet Rocketdyne to produce new RS-25 engines for use on SLS missions.

For the SLS, however, the engines will operate at unprecedented levels. Four RS-25 engines will fire simultaneously to provide 2 million pounds of thrust and operate in conjunction with a pair of solid rocket boosters to power the SLS at launch.

“This test series is really a continuation of our broader objectives to certify the engine to new start and run conditions for flight on SLS. Last year’s developmental engine series was our first sample to answer the question, ‘Does this engine handle the new SLS condition,’ ” said Steve Wofford, SLS Engines Manager at Marshall Space Flight Center in Huntsville, Alabama. “And the answer from that test series was a resounding, ‘Yes, no problem.’ This test series is really a second sample to continue that verification and green run our new flight controllers.”

NASA engineers conducted a seven-test developmental series of the new performance levels on another RS-25 engine last year, also on the A-1 Test Stand at Stennis. Earlier this year, engineers installed and tested RS-25 engine No. 2059, one of engines that will power the SLS on Exploration Mission-2, the first crewed flight on the new spacecraft. Additional flight engines also will be tested at Stennis.

As with the previous developmental tests, the new series is focused on collecting data on the new engine controller and higher operating parameters. On space shuttle missions, the engines operated at 104.5 percent of power level capability. The SLS calls for the engines to operate at 109 percent of power level capability.

In addition, due to the size and nature of the SLS, the RS-25 engines must withstand colder liquid oxygen and engine compartment temperatures, higher propellant pressure and greater exhaust nozzle heating. Engineers also must ensure a new RS-25 engine controller is operating effectively. Performance specifications, such as percentage of thrust needed, are programmed into the controller prior to engine ignition. The controller then communicates the performance needs and monitors engine conditions to ensure that needs are met, controlling such factors as propellant mixture ratio and thrust level.

It is critical that the controller communicates clearly with the engine. The new series of developmental tests will run the RS-25 engine through a range of adaptations needed for the SLS. The engine will be started at various temperatures and propellant pressures. Performance of the programmed engine controller and how it is regulating engine thrust, propellant mixture and thrust adjustments will be carefully monitored in all of the test variations.

Three separate controllers will be tested later in the test series. New engine seals also will be tested during the initial two firings. Hydraulic shutdowns of the engine will be tested, as will varied engine chill procedures that prepare the engine for firing.

“This is important,” A-1 Test Director Jeff Henderson explained. “We have to know all of these details in order to fly safely. The engine and test stand teams have focused on including as many objectives as possible into the test plan. We want to collect as much data as we can so we know as much as we can about how this engine will perform.”

Valerie Buckingham
Stennis Space Center
228-688-3898
valerie.d.buckingham@nasa.gov