During his testimony before the House Science, Space and Technology Committee’s hearing last month regarding the future of human space exploration, Dr. Jonathan Lunine, Report Co-Chair and Director of Cornell University’s Center for Radiophysics and Space Research, urged lawmakers to ensure that the U.S. will take the necessary steps so that humans will one day “walk on the red soil of Mars.” Working toward that goal, NASA and Aerojet Rocketdyne have recently completed successfully the final series of hot-fire tests on the J-2X engine, which is designed to be used on the evolved Block II version of the Space Launch System, which forms the backbone of the space agency’s exploration architecture for eventually sending humans to Mars during the 2030s.
Currently under construction, the Space Launch System, or SLS, is NASA’s next generation heavy-lift launch vehicle for sending crew and cargo to deep-space destinations like the Moon and Mars, a capability the U.S. has lacked ever since the end of the Apollo program 40 years ago. Although the first two launches of the SLS in 2017 and 2021 respectively are designed to be test flights of the initial Block I configuration capable of delivering 70 metric tons to low-Earth orbit (LEO), NASA is designing the heavy launch system to be evolvable, with the final Block II configuration having a payload capacity of 130 metric tons to LEO—surpassing the capability of the mighty Saturn V rocket that propelled humans to the Moon in 1968-1972. To achieve this superior payload-to-LEO capability, the SLS Block II configuration will host a large Earth Departure Stage powered by a trio of J-2X engines developed by leading space propulsion manufacturer Aerojet Rocketdyne, whose design is in turn based on the proven J-2 liquid fuel rocket engine that powered the second and third stages of the Saturn V during the Apollo program. Capable of producing a vacuum thrust of 294,000 lbs, the liquid hydrogen/liquid oxygen J2-X engine will have the power needed to propel heavy payloads like crew habitats, interplanetary science probes, and other cargo to beyond-LEO destinations in space.
Ever since the contract award for the design and development of the J-2X engine to Pratt & Whitney Rocketdyne (now Aerojet Rocketdyne) in July 2007, progress on the engine has been rapid and impressive. Following two rounds of successful shakedown tests of its gas generator and liquid fuel turbopumps during 2008-2010, the full J-2X engine underwent a rigorous hot-fire test campaign at NASA’s Stennis Space Center in Mississippi, during which a total of four test engines were manufactured, assembled, and tested by Aerojet Rocketdyne. The hot-fire test campaign began in June 2011 with the first J-2X test engine (officially known as E10001) undergoing a total of 21 tests over a period of 14 months on the A-2 test stand at the Stennis Space Center, while recording a total of more than 2,700 seconds of hot-fire time in the process including 1,700 seconds of hot-fire testing on the engine’s nozzle extension, a key engine component that allows the J-2X to deliver approximately 30 percent more thrust and 5 percent more performance than the Saturn V’s J-2 engine. During the E10001 tests, NASA’s engineers were able to meet all of the hot-fire campaign’s milestones as well, including a full flight hot-fire duration of 500 seconds in November 2011. A little over six months later, in June 2012, a marathon test of the engine’s Power Pack—the upper segment of the engine, including the gas generator, liquid hydrogen, and oxygen turbopumps, as well as related valves and ducting—was also performed, achievinng a record time of 1,150 seconds of hot-fire operation, while being the longest firing ever conducted at Stennis’ A Test Stand.
With the successful completion of the Power Pack’s test series in December 2012, it was time for engine E10002 to feel the heat while undergoing sea-level simulation testing on A-1 and high-altitude simulation testing on A-2 between February and September 2013. The E10002 test series proved to be a resounding success as well, leading to a total of 13 engine starts that accumulated over 5,200 seconds of hot-fire operation. Some of the milestones that were met were the successful study of the engine’s combustion stability and the thermal environment of the nozzle extension as well as its gimbal operation. The J-2X test campaign was concluded with the successful completion of hot-fire tests of engine E10003, which run from November 2013 to April 2014, recording 3,760 seconds of hot-fire duration during a total of 12 successful engine starts, while adding a wealth of data on the J-2X’s performance, allowing NASA to better evaluate its options for the SLS Block II configuration design. “From the start, testing of the J-2X engine progressed at an incredible pace and provided invaluable data,” said Gary Benton, RS-25 and J-2X Engine Test Project Manager at the Stennis Space Center, following the conclusion of the J-2X hot-fire test campaign on April 10. “We began J-2X Power Pack testing for the engine in late 2007 and conducted a wide range of full-engine developmental tests since then. We have collected data on engine and test stand capabilities and performance that will benefit the nation’s space program for years to come.”
The superior performance that the J-2X engine showcased on the test stand, compared to its predecessor, the J-2 used on the Saturn V rocket, was a result not only of a modernized, more streamlined design, but of Aerojet Rocketdyne’s on rocket propulsion development for all of NASA’s previous human spaceflight programs as well. “With J-2X, we were able to drive down the time needed to take a new rocket engine to 100 percent power level in testing, from 651 days to just 29, by integrating modern design, analysis and test practices with decades of experience gained on multiple engine development programs,” says Warren M. Boley, Jr. President of Aerojet Rocketdyne. “That kind of knowledge isn’t retained anywhere else in the industry and it demonstrates that we know how to design an engine that will work the first time.” “We had to modernize the J-2 engine to increase its power level and performance, so we had a good challenge on our hands,” adds Walt Janowski, J-2X Director and Program Manager for Aerojet Rocketdyne. “No part of this engine went untouched. We looked closely at each part to make sure it met modern standards and human-rated requirements.”
With the J-2X hot-fire tests now complete, NASA and Aerojet are gearing up for a similar round of tests on the liquid fuel RS-25, better known as the Space Shuttle Main Engine, or SSME. Four RS-25 engines will power the core stage of the Space Launch System, beginning with the heavy-lift vehicle’s inaugural EM-1 mission in December 2017. Having performed flawlessly on 135 missions during the 30-year career of the now-retired space shuttle, the RS-25, which were also developed by Rocketdyne, is being prepared for its next role as the workhorse of NASA’s next-generation launch vehicle. To that end, engineers at the Stennis Space Center have begun a series of modifications to the A-1 test stand, so that it can accommodate the engine for its upcoming hot-fire test series, which are due to begin July 8. “We’re gearing up for what we trust will be a successful and essential RS-25 test series, technically as well as on cost and schedule and our J-2X experience directly contributes to this need,” says Tom Byrd, Deputy Manager in the SLS Liquid Engines Office at NASA Marshall Space Flight Center in Huntsville, Ala. “The manufacturing and testing we just completed will continue to be beneficial to the RS-25, the SLS Program and the agency’s initiatives.”
The successful completion of the J-2X hot-fire tests and the transition to the RS-25 testing at NASA’s Stennis Space Center reflect the steady progress being made on the development and construction of the space agency’s next-generation launch vehicle. Following the completion of the RS-25 hot-fire tests, the engines will be transported to NASA’s Michoud Assembly Facility in New Orleans in September 2015, prior to their installation on the core stage of the SLS that will fly on the launch vehicle’s first mission, which remains on schedule and on budget for December 2017.
“This is a very exciting time at NASA,” says Benton. “We are moving closer and closer to making unprecedented space exploration missions a reality.”
Video Credit: NASA/Stennis Space Center
This article was co-written by AmericaSpace author Ben Evans. The authors would like to thank Aerojet Rocketdyne’s Communications Specialist Miss Jessica Pieczonka for her overall assistance.