Stennis preparing to throttle up SLS engine testing

by Chris Bergin

NASA’s Stennis Space Center is deep into preparations for numerous engine testing for the Space Launch System (SLS), ranging from the old, the new and the miniature. Continued J-2X testing will next take place on the A-2 Test Stand, while the A-1 Test Stand will conduct RS-25 testing next year. Meanwhile the 116 Test Stand will host testing of the mini-SLS for the Scale Model Acoustic Test program (SMAT).

Stennis Testing:

NASA’s new Heavy Lift Launch Vehicle (HLV), the SLS, will be an evolvable rocket that will be able to cater for a range of missions throughout NASA’s long-term deep space ambitious of visiting Near Earth Asteroids and eventually landing people on Mars.

NASA leaders claim they require the fully evolved Block II SLS, capable of lofting payloads of 130mT into space, for their “full capability” missions to asteroids and Mars – the latter requiring numerous launches of the HLV per campaign.

A large amount of the additional power of the Block II will come via the Upper Stage, driven by J-2X engines.

J2XFamilyThe J-2X is being developed for the Marshall Space Flight Center (MSFC) SLS Program by Pratt & Whitney Rocketdyne (now Aerojet Rocketdyne) with the engine initially starting out its life as the single engine on the Ares I Upper Stage, with work towards that goal beginning in 2006.

Based on an engineering heritage that reached back as far as the 1960s, five of the original J-2 engines powered the SII Second Stage of the Saturn V.

This latest variant is capable of generating 294,000 lbf (1,310 kN) of thrust, with a lengthy test program continuing at the Stennis Space Center.

Testing began with P&W Rocketdyne successfully evaluating the initial J-2X gas generator design in 2008, followed by the completion of a second round of successful gas generator tests in 2010.

Z3The test schedule, now with a focus on supporting future SLS missions, remains on track, with this month marking J-2X Engine No. 10002 test firing for the final time on the A-1 test stand at Stennis.

The 330-second test was the last in a series of gimbal, or pivot, tests on the engine.

“This test completed a very successful thirteen test series for engine 10002 which included a 5200 second, two-times service life demonstration, as well as seven gimbal tests,” noted information in L2’s SLS section.

“All J-2X gimbal requirements were verified.  The new facility Thrust Measurement System (TMS) was also exercised for the first time with no significant issues.”

The engine will now be removed from A-1 Test Stand, ahead of facility modifications to accommodate RS-25 engine 0525 for test operations, set to begin in Spring 2014. The “new build” J-2X engine E10003 will be hosted on the A-2 Test Stand to continue its test program.

RS-25 engine 0525 is one of numerous former Space Shuttle Main Engines (SSMEs) that are living on with SLS.

A319All 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.

A total of 15 RS-25Ds left the Kennedy Space Center (KSC) for their new role, arriving at the Stennis Space Center not long after the orbiters all started to head out to their retirement homes.

Z27Notably, 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.

Final testing – using these units was conducted in 2009 – with engine 0525 earmarked for any hot-fire tests that may have been required to support the final STS missions during 2010.

This engine now gets a staring role in helping kick-start the RS-25’s new life with SLS, as Stennis engineers continue to building and install a new 7,755-pound thrust frame adapter for the A-1 Test Stand, in order to enable testing of the RS-25s ahead of their role on SLS’ core.

RS-25 with the adaptorThe reason for the new adaptor relates to the requirement of different types of engines. On the test stand, the adapter is attached to the thrust measurement system, with the engine then attached to the adapter, which must hold the engine in place and absorb the thrust produced during a test, while allowing accurate measurement of the engine performance.

The adaptor that is installed on the A-1 Test Stand is specific for the J-2X and can’t be used for the RS-25, given that engine is much more powerful, with the ability to produce approximately 530,000 pounds of thrust.

The design – produced by NASA, Lockheed Martin Test Operations Contract Group and Jacobs Technology – took several considerations into account, such as specific stresses on the equipment as an engine is fired and then gimbaled during a test.

The installation is set to take place in November, once the Test Stand has completed J-2X gimbal testing. Testing of the RS-25 family will begin next year.

Also preparing for testing is the scaled version of the SLS, ahead of test firing it later this year.

Z76Known as the Scale Model Acoustic Test (SMAT), the mini-version of the SLS will have functioning rockets mimicking both the core engines and boosters, in order to gain data on the acoustic environments endured during ignition and launch.

*Click here for the full SMAT Overview Article*

Following on from the Ares I Scale Model Acoustics Test (ASMAT) tested during 2010, Marshall Space Flight Center (MSFC) turned their attentions towards a similar test for the HLV.

Work begin in 2012 at Marshall’s Test Stand 116, with the construction of a working water-based sound suppression system, while plans were made of the assembly of what is the advanced sub-scale rocket to used on such a test.

The model – which is at least 20 feet tall – will sport two Rocket-Assisted Take Off (RATO) motors, which will simulate SLS boosters, with the test requirement calling for the motors ignite simultaneously, as the SRBs would during launch.

Four small thrusters have been installed on the core, with their role in mimicking the RS-25s for the test objectives that will be initiated in November.

Z4“Preparations are continuing for the Space Launch System (SLS) Scale Model Acoustic Test program (SMAT) in Test Stand 116 at Marshall Space Flight Center (MSFC),” added L2 notes.

“The four Core Stage Thrusters have been integrated into the core section of the SMAT model with the required Propulsion system feed lines and components.  Initial Thruster only testing is on track to initiate in mid-November of this year.”

The test vehicle will be heavily instrumented, with five primary instrumentation suites resulting in over 325 sensors on the SMAT rocket.

It will be outfitted with B&K 4944-B microphones, pressure transducers on the tower/mobile launcher. It will include far field measurement devices, accelerometers, thermocouples and strain gauges on vehicle, thermocouples, flow meters and chamber pressure instrumentation.

All core stage schedules show they continue to enjoy at least six months margin for making SLS’ debut flight – on Exploration Mission -1 (EM-1) – in 2017.

(NSF and L2 are continuing to provide the most extensive and exclusive SLS coverage. To join L2, support the site and access a huge database of content, click here:

Related Articles