Stennis fires up RS-25 engine for full duration test

by Chris Bergin

The second test firing of RS-25 engine 0525 has taken place at the A-1 Test Stand at the Stennis Space Center. The developmental engine – that never got to fly with the Space Shuttle – is paving the way for the first four RS-25 engines that will help push the Space Launch System (SLS) uphill in 2018, with 16 of the engines now available following the construction of a new engine.

RS-25 Hot Fire:

Thursday night’s test follows on from the return to RS-25 firings at Stennis at the start of the year.

Testing was then halted to allow engineers to complete upgrades on the high pressure industrial water system, which provides cool water for the test facility during a hot fire test.

2015-05-29-023112Thursday’s full duration test was deemed to be successful, although engineers are required to check over the data in the coming days and weeks, with the engine and test stand heavily instrumented during the firing for that purpose.

Engine 0525 has never flown in space, given 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.

A total of eight tests, totaling 3,500 seconds, are planned for E0525, with a second development engine set to undergo 10 tests, totaling 4,500 seconds. The second test series includes the first test of new flight controllers, known as green running.

The engine controller unit allows for the engine and the vehicle to communicate with each other, relaying commands to the engine and transmitting data back to the vehicle – providing closed-loop management of the engine by regulating the thrust and fuel mixture ratio while monitoring the engine’s health and status.

The electronic package of the controller contains five major sections; power supply section, input electronics section, output electronics sections, computer interface section, and digital computer unit.

Pressure, temperature, pump speed, flowrate, and position sensors supply the input signals. Output signals operate spark igniters, solenoid valves, and hydraulic actuators. The controller is dual redundant, which provide normal, fail-operate, and fail-safe operational mode capability.

The controllers on the RS-25Ds used during the Space Shuttle Program (SSP) proved to be highly reliable. However, the new controller will utilize updated hardware and software configured to operate with the new SLS avionics architecture.

“The RS-25 is still one of the most advanced engines in the world,” noted RS-25’s Philip Benefield. “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.”

2015-05-29-023415For the debut flight – known as Exploration Mission-1 (EM-1) – NASA’s Liquid Engine Office has already selected the first four engines that will loft the monster rocket uphill.

The four engines – ME-2045, ME-2056, ME-2058, and ME-2060 – are all established Shuttle veterans with numerous successful missions under their belts.

A total of 15 RS-25Ds left the Kennedy Space Center (KSC) for their new role, arriving at the Stennis Space Center in 2012.

FRR Slide for STS-133, via L2All nine of the last SSMEs to fly with the Space Shuttle performed admirably, with Discovery flying Main Engine 1 (ME-1) – serial number 2044, ME-2 – 2048 and ME-3 – 2058 during her final mission, STS-133.

For Endeavour’s swansong, ME-1 – 2059, ME-2 – 2061, and ME-3 – 2057 helped begin the flight phase of the successful STS-134 mission, while Atlantis closed out the Space Shuttle Program, flying with engines ME-1 – 2047, ME-2 – 2060 and ME-3 – 2045 during STS-135.

All of these engines will now get to fly one more time, on the core stage of the SLS.

As recently reported by, the RS-25’s recently welcomed a new sibling to the engine family.

2015-05-29-023304“The assembly of the first new RS-25 flight engine 2063 for SLS was completed. This is also the first RS-25 engine completely assembled from available parts since Sep 20, 2010,” noted L2 information.

“This engine joins a fleet of 15 other legacy engines, 14 of which have already flown to space numerous times on various Space Shuttles during the 135 missions of the Shuttle era. All of the legacy engines are being upgraded with a state of the art engine controller and improved thermal insulation.”

NASA has since confirmed the addition of the engine and provided more information on its construction.

2015-05-29-024520This new unit will undergo acceptance testing to verify it is acceptable for flight, checking out the completed system. NASA also noted that the engine 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,” noted Steve Wofford, manager of the SLS Liquid Engines Office at MSFC.

“We’re testing one engine, developing a new controller and planning to manufacture new engines in the future.”

2015-05-29-023636Several additional engines have also been ordered from Aerojet Rocketdyne by NASA, known solely as the RS-25 (as opposed being called the RS-25E), which are cheaper, expendable versions of the engine. Further information on those engines will be revealed at the conclusion of the procurement process.

Those engines will join a rich tradition, with the RS-25 one of the most tested large rocket engines in history, with more than 3,000 starts and over a million seconds of total ground test and flight firing time over 135 missions.

The engines proved their worth during the Shuttle era, with only one major malfunction during its flight history, namely STS-51F (ME-1), resulting in a safe Abort To Orbit (ATO).

Images: NASA and L2 artist Nathan Koga via L2’s SLS sections, which includes, presentations, videos, graphics and internal – interactive with actual SLS engineers – updates on the SLS and HLV, available on no other site.)

(L2 is – as it has been for the past several years – providing full exclusive SLS and Exploration Planning coverage. To join L2, click here:

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