Progress on the J-2X Upper Stage Engine for the Ares I Crew Launch Vehicle and the Ares V Cargo Launch Vehicle

The J-2X rocket engine will provide the upper stage propulsion for NASA’s Ares I Crew Launch Vehicle (CLV) and the Ares V Cargo Launch Vehicle (CaLV) as shown in Figure 1. The liquid oxygen/liquid hydrogen (LOX/LH2) J-2X represents an evolution of two historic predecessors: the powerful J-2 upper stage engine that propelled the upper stages of the Apollo-era Saturn IB and Saturn V rockets, and a simplified version of the J-2, the J-2S, developed in the early 1970s before the Apollo program ended and resurrected briefly in the late 1990s for the X-33 aerospike engine program but never flight-tested. This paper will discuss the history of the J-2, its evolution to its current configuration, its current technical and programmatic status, and a preview of future activities. Figure 1. Ares I, left, and Ares V launch vehicle concepts. The U.S. Vision for Space Exploration requires safe and highly reliable launch vehicles. The initial Ares I and Ares V design recommendations emerged from a team of aerospace experts commissioned by NASA in spring 2005 to conduct the Exploration Systems Architecture Study (ESAS). The ESAS analysis focused on a human-rated CLV to replace the Space Shuttle after it is retired in 2010 and a heavy-lift CaLV to carry equipment and supplies for lunar missions, and, eventually, the first human journeys to Mars. After several months of comparing safety, reliability, technical performance, budget, and schedule factors in relation to design reference missions, the ESAS design options were unveiled in summer 2005. The lunar mission would begin by launching the Ares V into orbit with the Earth Departure Stage (EDS) and the Lunar Lander, followed by the Ares I, carrying the Orion 1 Deputy Manager, Upper Stage Engine Element, Exploration Launch Projects Office. 2 Manager, Upper Stage Engine Element, Exploration Launch Projects Office. American Institute of Aeronautics and Astronautics 1 43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 8 11 July 2007, Cincinnati, OH AIAA 2007-5832 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States. Crew Exploration Vehicle (CEV), which would rendezvous with the EDS/Lunar Lander before beginning its journey to the Moon (Figure 2). Engineering trade studies performed by NASA’s Exploration Launch Projects Office helped refine the ESAS designs, so that the Ares I and the Ares V share a common upper stage engine, the J-2X. Figure 2. J-2X-powered Earth Departure Stage and Crew Exploration Vehicle in Earth orbit. The Ares I first stage is a single 5-segment Reusable Solid Rocket Booster (RSRB) derived from existing Space Shuttle hardware. The Ares V first stage is powered by two 5-segment RSRBs flanking a 33-foot-diameter propellant tank with an aft-mounted cluster of five RS68 engines. The ESAS identified the RS-25 Space Shuttle Main Engine (SSME), modified to be low-cost and expendable, as the baseline engine for the upper stages of both Ares launch vehicles, as well as the Ares V Core Stage. NASA’s systems engineering approach refined the ESAS point-of-departure architectures during the following analysis cycle, streamlining its hardware development approach to reduce programmatic, technical, and budget risks by seeking commonalities between the Ares I and Ares V. Analyses concluded that a modified RS-68 for the Ares V Core Stage and the J-2X for the Ares I and Ares V Upper Stage Engine would simplify recurring and nonrecurring costs, reduce the number of new engines to be developed, and also would leverage a higher technology readiness level than was available for the SSME. The J-2 engine also had an advantage in that it was a human-rated engine capable of restarting in flight, something the SSME was not designed to do. In June 2006, NASA gave the Exploration Launch Projects Office authority to proceed with J-2X development and awarded Pratt & Whitney Rocketdyne, Inc., of Canoga Park, Calif., a letter contract worth $50 million to initiate design, development, test, and evaluation of the J-2X engine for the Ares I and Ares V. Figure 3 shows the J-2X in expanded views of the Ares launch vehicles. American Institute of Aeronautics and Astronautics 2 Figure 3. Expanded views of Ares I and Ares V show common hardware. Ongoing reviews of engineering data and business considerations are ensuring that the J-2X fully meets customer and stakeholder requirements. Safe, reliable, and cost-effective space transportation systems are a critical part of America’s future plans in space, from the continued operation of the International Space Station, to revitalized lunar capabilities, to the eventual human exploration of Mars. NASA plans to use legacy knowledge and heritage hardware for near-term risk reduction and success that will help sustain the national interest and will. The J-2X exemplifies that guidance. The J-2X team will emphasize a “test as you fly, fly what you test” development philosophy as it continues testing critical engine hardware.