The powerpack assembly for the Pratt & Whitney Rocketdyne (PWR) J-2X engine has completed its year of testing at NASA’s Stennis Space Center in Mississippi. The engine is set to provide the Earth Departure Stage (EDS) role for astronauts and hardware heading to destinations in deep space, should NASA opt to evolve SLS to the Block II configuration.
J-2X and SLS:
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.
Per NASA’s own Design Reference Mission (DRM) and Concept of Operations (CONOPS) documentation (L2), this 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 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.
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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.
Moving past the ongoing arguments about the need for a Block II SLS, the J-2X – the first human-rated liquid oxygen and liquid hydrogen engine developed in the United States in decades – will be a very capable engine.
The J-2X is being developed for the Marshall Space Flight Center (MSFC) SLS Program by Pratt & Whitney 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 my instrumentation during STS-51F – during the entire 30 year career of the Shuttle fleet.
As noted, 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 being tested at the new A2 test stand at 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.
This week marked the final test-firing of the J-2X powerpack assembly for 2012, a system of components on top of the engine that feeds propellants to the bell nozzle of the engine to produce thrust.
There are currently three major elements of J-2X hardware at Stennis, the 10001 engine, the powerpack and the 10002 engine – the latter of which was last noted as undergoing engine valve installation inside Stennis building 9101.
Showing the importance of testing, the hardware has provided few minor tantrums throughout the year, examples of which the early shutdown on a test in late September.
“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.”
The reason the powerpack was separated from the engine for evaluations is 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.
“These tests at Stennis are similar to doctor-ordered treadmill tests for a person’s heart,” said Tom Byrd, J-2X engine lead in the SLS Liquid Engines Office at Marshall in Huntsville, Alabama. “The engineers who designed and analyze the turbopumps inside the powerpack are like our doctors, using sensors installed in the assembly to monitor the run over a wide range of stressful conditions.
“We ran the assembly tests this year for far longer than the engine will run during a mission to space, and acquired a lot of valuable information that will help us improve the development of the J-2X engine.”
NASA engineers will remove the powerpack assembly from the test stand to focus on tests of the fully integrated engine – likely to be engine 10002 – to undergo testing in 2013.
(Images: Via L2 and NASA)
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