Second J-2X engine prepares for SLS testing
Engineers at the Stennis Space Center in Mississippi are preparing for a series of tests on a second J-2X engine – designated as unit 10002. This new series of evaluations will follow on from the 21 tests conducted on the 10001 J-2X, as the hardware prepares for its role as the future Upper Stage engine on the Space Launch System (SLS).
The J-2X initially held the role of the single engine on the Ares I Upper Stage, with work towards that goal beginning in 2006. It too had its own heritage, based on engineering that reached back as far as the 1960s, with the original J-2 engine – five of which powered the SII Second Stage of the Saturn V.
This latest variant is capable of generating 294,000 lbf (1,310 kN) of thrust, and is now deep into testing at Stennis Space Center.
The J-2X is has been development for several years, with Pratt & Whitney Rocketdyne successfully evaluating the initial J-2X gas generator design back in 2008, followed by the completion of a second round of successful gas generator tests in 2010.
The work at Stennis has revolved around three major elements of J-2X hardware, the 10001 engine, the powerpack and the 10002 engine – the latter of which spent the end of 2012 undergoing assembly inside building 9101 at the famous test center.
Showing the importance of testing, unit 10001 suffered from a few minor tantrums in 2012, with one example noting an early shutdown during its final test in late September of last year.
“The J-2X engine 10001 has completed its test series in the SSC A-2 test stand, completing 21 tests and 2,717 seconds hot fire time. Test #21 on September 25, 2012 was cut off at 3.5 seconds of the planned 250 second test, due to low discharge pressure at the fuel turbopump,” according to notes provided to L2’s J-2X Update Section.
“The engine was shut down safely. Post-test data review and hardware inspections found the engine experienced a combustion “pop” (anomalous lox/fuel detonation) inside the turbine drive hot gas system. The test failure team has determined root cause to be incorrect installation of the gas generator pyrotechnic igniters, resulting in failure to properly ignite the gas generator.”
However, the engine did gather a large amount of vital data, in addition to the tests that continued through the test of 2012 on the J-2X powerpack assembly – a system of components on top of the engine that feeds propellants to the bell nozzle of the engine to produce thrust.
The reason the powerpack was separated from the engine for evaluations was to allow for it to be more thoroughly tested to its limits. It also can be operated under a wider range of conditions, the results of which will tests provide a analytical predictions of the performance of several parts in the turbopump and flexible ducts.
The powerpack assembly burned millions of pounds of propellants during a series of 13 tests totalling more than an hour and a half in 2012. The testing team set several records for hot-firing duration at Stennis test stands during the summer of 2012.
In total, 34 tests were conducted on the J-2X engine and powerpack, with the J-2X achieving a full flight-duration firing of 500 seconds in the eighth test, earlier than any rocket engine in US history.
Now Stennis’ engineers are moving towards the next series of tests on the second J-2X development engine, designated number 10002, on the A-2 Test Stand. Once the series is completed, the engine will be transferred to the A-1 Test Stand to undergo a series of gimbal, or pivot, tests for the first time.
“The J-2X test team transported Engine 10002 from building 9101 to the A2 Test Stand on 1/22/13. The engine was installed several hours later and the clamshell was lowered. The nozzle extension was then installed, as final instrumentation work is completed on the extension in order to measure film-cooling effectiveness,” per notes in L2’s J-2X Update Section.
“This short test series consisting of approximately six tests will begin in February. After completion of this test series, the engine will be removed and installed in Test Stand A1 for a second short test series to characterize/verify gimbal requirements. Testing of Engine 10002 is planned to be complete by late summer 2013.”
According to NASA, the first objective of the testing is to verify and demonstrate the engine’s capability. Data from what is known as hot-fire engine tests will be compared to the performance of the first engine.
Engineers also will vary liquid hydrogen and liquid oxygen inlet pressures and subject the engine nozzle to higher temperatures than in previous tests to see what effect they have on performance.
“The upcoming test series is not only a critical step forward, but important to the Stennis test team, as well,” noted Gary Benton, manager of the J-2X test project at Stennis. “This test series will help us increase our knowledge of the J-2X and its performance capabilities.”
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The J-2X is being developed for the Marshall Space Flight Center (MSFC) SLS Program by P&W Rocketdyne – who are also the manufacturer for the superstar RS-25s that enjoyed a superb flight record with the Space Shuttle, with only one “engine out” issue during launch – caused by instrumentation during STS-51F – during the entire 30 year career of the Shuttle fleet.
“In addition, the series will help us maintain the high skill level of our team as we look ahead to continued J-2X testing and testing of the RS-25 engines that will be used to power the SLS first-stage,” added Mr Benton.
The new Heavy Lift Launch Vehicle (HLV) is currently set to evolve through three major configurations, opening with a 70mt Block 1 design, providing the vehicle for what is presently two test missions to send Orion on an uncrewed – then crewed – flight around the Moon.
These two missions using the Block 1 – Exploration Flight Test -1 (EM-1) and Exploration Flight Test -2 (EM-2) – are currently scheduled for 2017 and 2021 respectively.
The Block 1 will consist of an 8.4m diameter “External Tank” heritage system core stage, housing the Main Propulsion System (MPS) – which will drive four Space Shuttle Main Engines (RS-25Ds) donated by the Space Shuttle Program (SSP). Two ATK five segment boosters will provide the majority of the first stage power for the ride uphill.
The Interim Cryogenic Propulsion Stage (ICPS) will driven by the Delta Cryogenic Second Stage (DCSS), following on from its role in 2014 with the Exploration Flight Test -1 (EFT-1) mission that will send Orion on its first test mission.
For the majority of the 2020s, SLS will use the Block 1A or 1B configuration using PWR’s RS-25E engines – an expendable version of SSME – on the core stage once existing stocks of the RS-25D are exhausted, with the switch currently predicted to occur for SLS-5. The Upper Stage will be a Cryogenic Propulsion Stage (CPS) using four RL10A-4-2 engines.
The Block 1A/B options will be the configurations capable of hosting the Advanced Boosters, currently in the early stages of competition involving several companies.
The fully evolved SLS, known as the Block II (Block 2), is not expected to be ready until the late 2020s, possibly the early 2030s, providing 130mt of capability. There is some uncertainty surrounding this vehicle’s viability and requirement for what remains an undefined NASA exploration roadmap – although L2 source information is now showing a preliminary roadmap has been completed to a White Paper stage.
Per NASA’s own Design Reference Mission (DRM) and Concept of Operations (CONOPS) documentation (L2) – the foundation of the roadmap evaluations – the fully evolved HLV would only be required on the most ambitious mission scenario to a Near Earth Asteroid (NEA), with its focus firmly placed on missions to Mars.
Sources within NASA continue to claim the 105mt capable Block 1A/B configurations may be enough to satisfy upmass requirements for all Beyond Earth Orbit (BEO) missions.
It has also been argued that NASA had to find a use for the J-2X, following the demise of the Constellation Program (CxP), a program that saw the J-2X being used as the Upper Stage engine on the defunct Ares I launch vehicle.
With political requirements in the 2010 Authorization Act- created under the guidance of NASA managers – stating the need to provide a 130mt capable vehicle that utilized former Shuttle and CxP hardware, the J-2X was handed a lifeline, but only with the Block II SLS. As such, three J-2X engines are baselined into the Earth Departure Stage (EDS) on the fully evolved SLS.
(Images: Via L2 and NASA)
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