RS-25 fires up again in latest SLS engine test

by Chris Bergin and Philip Sloss

The latest static fire test of the development RS-25 engine (E0528) has taken place at the Stennis Space Center. The test is part of a series aimed at validating hardware and software elements, such as the improved engine controller, as the former Space Shuttle Main Engines (SSME) prepare to launch the opening Space Launch System (SLS) missions.

RS-25 Test:

NASA already has a healthy stock of RS-25 flight engines, most of which were used for Shuttle flights, along with two development engines used in ground development testing for both the Space Shuttle Program and now SLS.

A total of 15 RS-25Ds left the Kennedy Space Center (KSC) to be reunited with spare engines and parts that have since congregated at Stennis.

The shipment from Florida included nine of the last SSMEs to fly with the Space Shuttle, all of which performed admirably.

Per L2 documentation, Discovery flew with 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.

RS-25 Engine 0525 – a development engine that new flew with the Shuttle – conducted seven static fire tests on the A-1 Test Stand at Stennis, prior a flight engine being installed in its place.

*Click here for more RS-25 Engine News Articles*

That engine was E2059, which flew on five Space Shuttle missions; it first flew three times on Shuttle Orbiter Atlantis (STS-117, STS-122, and STS-125) and then on Orbiter Endeavour’s last two flights (STS-130and STS-134).

2016-07-07-204204It is currently assigned to fly installed in the second Core Stage on Exploration Mission-2 (EM-2), which is planned to be the first crewed SLS/Orion flight.

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.

The RS-25 controller provides complete and continuous monitoring and control of engine operation. In addition, it performs maintenance and start preparation checks, and collects data for historical and maintenance purposes.

The controller is an electronic package that 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.

2016-07-14-174007Continuing the test program, E0528 was then installed for a new test series, with the primary objective of the testing aimed to verify the new engine control system and more data testing on the new engine controller for the RS-25.

In a rare occurrence, the first test firing of this engine was aborted.

Test 901-1016 on July 14 was planned to last 650 seconds, exercising Engine 0528 at different throttle settings.

However, the test was abruptly terminated with the engine commanded to shutdown approximately 193 seconds after ignition.

The problem was not the result of engine problems, but with the test facility itself. Syncom Space Services is the prime contractor for Stennis facilities and operations.

However, a follow-on “make up” test, which wasn’t classed as a repeat of the aborted firing, took place on July 29 and was a full duration success.

The 7.5-minute tests are part of a series of designed to put the engines through the rigorous temperature and pressure conditions they will experience during a launch.

The latest test, technically the third of the series for this engine, fired up on Thursday, providing a focal point to a day of assaulting social media with hashtags to increase awareness for missions that NASA hopes will take place via the use of RS-25 hardware.

2015-09-16-032047Those missions to Mars are still in the planning phase – in some cases “U/R – Under Review” via the Design Reference Mission (DRM) process – and are technically unfunded.

Given the projected timeline in NASA’s own documentation, missions to Mars are expected no sooner than the end of the 2030s. However, the agency hopes to land humans to Phobos by the mid-2030s.

That hasn’t stopped NASA twitter accounts from claiming human boot prints on the Red Planet by the “early” 2030s, which is in line with political instruction, but not aligned to NASA’s own internal schedules.

While political instruction needs to be backed with political funding support, the current timeline includes the challenge of new Presidents and administrations backing each of their predecessor’s path.

For the interim, NASA will continue to press forward with its current instructions, of which these RS-25 tests are a required element.

(Images: Via NASA and L2 – including SLS renders from L2 artist Nathan Koga)

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