Review of X-33 Hypersonic Aerodynamic and Aerothermodynamic Development

A review of the experimental and computational studies performed at NASA Langley Research Center (LaRC) to support the optimization and benchmarking of the hypersonic aerodynamic and aerothermodynamic databases for the X-33 vehicle is presented. A synoptic of the testing, computational, and analysis capabilities at LaRC applied to these studies is given. Analyses of the hypersonic aerodynamic characteristics, control surface effectiveness, and reaction control system effects are discussed. Experimental measurement of the aerodynamic heating via the global thermographic phosphor technique and development of a hypersonic boundary-layer transition correlation for X-33 is described. Computational results used to complement the experimental program and to assess the vehicle aerodynamic and aerothermodynamic characteristics in flight are presented. The technical findings, impacts, and lessons learned from the studies are discussed. 1 Overview of the X-33 Program 1.1 Background In 1993, an internal NASA study [1] proposed development of a fully reusable, rocket powered, single-stage-to-orbit (SSTO) vehicle capable of delivering 25,000 lbs (including crew members) to the International Space Station. This new launch system would combine efficient operations with increased safety and provide access to space at greatly reduced cost. The “Access-to-Space” study identified critical technologies that required development before a SSTO reusable launch vehicle (RLV) could be successfully flown. NASA also recommended that this new system be commercially owned and operated, unlike previous programs. Therefore, an approach was followed whereby NASA would work cooperatively with an industry partner to mature the technology for RLV through development of a sub-scale technology demonstration, i.e. the X-33 program. The X-33 program was organized as an industry-led partnership with NASA in which the companies negotiated development tasks with the various NASA centers prior to submitting proposals. Industry would utilize government facilities and share in the program costs. A Phase I competition for X-33 was held in 1995 among the industry leaders (Lockheed-Martin, Rockwell, McDonnell Douglas/Boeing). Lockheed-Martin Skunk Works (LMSW) was ultimately awarded the program to continue into Phase II and toward construction and flight of the X-33 vehicle. The X-33 program (Phase I and Phase II) had ambitious, fast-paced schedules with a total time from development to flight of 3-4 years. Development of VentureStar , the full-scale operational RLV, progressed in parallel with the X-33 program [2]. Figure 1. The Lockheed-Martin X-33 and early RLV compared to Shuttle.