1
Introduction

BACKGROUND

More affordable access to space is needed to bring down the cost of using space for communications, reconnaissance, and civil remote sensing; opening space for experimentation and processing; and learning about living in space in preparation for human space exploration. A number of important reports in recent years have identified lowering the cost of access to space as one of the highest national aerospace priorities.1 2 3 4 5 6

In the past, the National Aeronautics and Space Administration (NASA), the Department of Defense (DoD), and the U. S. launch industry have attempted to grapple with the problem of lowering the costs of space transportation by undertaking various research and development programs. In 1993 NASA issued a report entitled "Access to Space" recommending directions for future space transportation efforts.7 Specifically, the NASA study focused on improving reliability, crew safety, and reducing operations costs. The study concluded that a single-state-to-orbit (SSTO) vehicle is a feasible system for achieving reliable, low cost access to space. DoD considered launch vehicle modernization in a parallel study issued in early 1994.8 Building on these studies, the White House issued the National Space Transportation Policy in August 1994. The policy was developed by the Office of Science and Technology Policy (OSTP) and intended to address the issue of space transportation by assigning NASA the lead-agency responsibility for "technology development and demonstration for next-generation reusable space transportation systems."9 The policy further stated that "NASA's research shall be focused on technologies to support a decision no later than December 1996 to proceed with a subscale flight demonstration which would prove the concept of SSTO." NASA established the Reusable Launch Vehicle (RLV) program (see Figure 1-1) in the "Implementation Plan for the National Space Transportation Policy"10 in response to the OSTP mandate. NASA's Office of Space Access and Technology instituted the RLV program, focusing on maturation of the key technologies for development of an SSTO: advanced propulsion systems, reusable cryogenic tanks, composite primary structures, advanced thermal protection system, avionics, and more-operable systems.



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Reusable Launch Vehicle: Technology Development and Test Program 1 Introduction BACKGROUND More affordable access to space is needed to bring down the cost of using space for communications, reconnaissance, and civil remote sensing; opening space for experimentation and processing; and learning about living in space in preparation for human space exploration. A number of important reports in recent years have identified lowering the cost of access to space as one of the highest national aerospace priorities.1 2 3 4 5 6 In the past, the National Aeronautics and Space Administration (NASA), the Department of Defense (DoD), and the U. S. launch industry have attempted to grapple with the problem of lowering the costs of space transportation by undertaking various research and development programs. In 1993 NASA issued a report entitled "Access to Space" recommending directions for future space transportation efforts.7 Specifically, the NASA study focused on improving reliability, crew safety, and reducing operations costs. The study concluded that a single-state-to-orbit (SSTO) vehicle is a feasible system for achieving reliable, low cost access to space. DoD considered launch vehicle modernization in a parallel study issued in early 1994.8 Building on these studies, the White House issued the National Space Transportation Policy in August 1994. The policy was developed by the Office of Science and Technology Policy (OSTP) and intended to address the issue of space transportation by assigning NASA the lead-agency responsibility for "technology development and demonstration for next-generation reusable space transportation systems."9 The policy further stated that "NASA's research shall be focused on technologies to support a decision no later than December 1996 to proceed with a subscale flight demonstration which would prove the concept of SSTO." NASA established the Reusable Launch Vehicle (RLV) program (see Figure 1-1) in the "Implementation Plan for the National Space Transportation Policy"10 in response to the OSTP mandate. NASA's Office of Space Access and Technology instituted the RLV program, focusing on maturation of the key technologies for development of an SSTO: advanced propulsion systems, reusable cryogenic tanks, composite primary structures, advanced thermal protection system, avionics, and more-operable systems.

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Reusable Launch Vehicle: Technology Development and Test Program FIGURE 1-1 RLV Technology Demonstration Program. Source: NASA. FIGURE 1-2 RLV Program Phase Descriptions. Source: NASA.

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Reusable Launch Vehicle: Technology Development and Test Program There has been much debate concerning the direction of the National Transportation Policy. This debate has focused mainly on whether NASA should attempt to develop an SSTO vehicle or should focus its limited resources on a less challenging goal, such as a reusable two-stage-to-orbit vehicle. Because this issue is being scrutinized in other forums, NASA asked that the National Research Council (NRC) not revisit the roles and responsibilities assigned to NASA by the National Transportation Policy or attempt to determine the feasibility of developing an SSTO vehicle. NASA will use three experimental vehicles for testing and technology development, the DC-XA, the X-34, and the X-33. The DC-XA vehicle will be the successor to the Delta Clipper-Experimental (DC-X) vehicle, which was initially developed and demonstrated by the Ballistic Missile Defense Organization. The DC-X vehicle, which was transferred to NASA in August 1995, will be reconfigured into the DC-XA. Numerous SSTO technologies will be added to the DC-X, and the reconfigured DC-XA will be flight tested in mid-1996. Both the X-34 and X-33 programs are likely to benefit from the technological advances and operational experiences of the DC-XA. The X-34 small booster technology demonstrator is intended to stimulate the joint industry/government-funded development of a small reusable (or partially reusable) booster that will be used to investigate advanced technologies for a future RLV. The demonstrator model is expected to provide an early testbed for some of the advanced technologies that could be used on a RLV and demonstrate significantly reduced mission costs for placing small payloads in low Earth orbits. NASA anticipates that the X-34 program will begin test flights in late 1997 and will achieve orbital launch by mid-1998, with two more test flights by the end of 1998. The advanced technology demonstrator program, the X-33, which will last longer than the X-34 program, is divided into the three phases shown in Figure 1–2. According to NASA's implementation plan, "the X-33 system must prove the concept of a reusable next-generation system by demonstrating key technology, operations, and reliability requirements in an integrated flight vehicle."11 The three phases of the X-33 program are as follows: Phase I—Concept Definition/Design. This phase began in March 1995 and is scheduled to continue for 15 months during which the maturity levels of a wide range of candidate technologies should be demonstrated. Phase II—X-33 Advanced Technology Demonstration. If approved, this phase will begin by the end of 1996 and will continue through the end of the decade. The X-33 vehicle will be built and flown during Phase II. Phase III—Commercial Development of a Next-Generation Space Launch System. This phase is expected to begin at the end of the decade, pending the success of Phase II, and could lead to the development of an operational RLV by 2005. To reduce the technical risks of the RLV program, NASA has contracted with three industry teams to develop and improve the desired technology. NASA maintains only a small RLV program office with a staff of about 20 people. The three industry

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Reusable Launch Vehicle: Technology Development and Test Program teams are operating as prime contractors and, accordingly, have selected subcontractors. In several instances, NASA centers that have the appropriate expertise or facilities have been chosen as subcontractors to the industry teams.a Prior to December 1996, NASA and the contractors will make a recommendation to the President about whether to proceed with Phase II of the program (i.e., development of the X-33). If one or more U.S. aerospace companies opt to proceed with the Phase III development of a full-scale RLV, that company will be free to adapt new propulsion systems, materials, and other technologies to whatever type of reusable, or partially reusable, vehicle design it believes will be most economical. In Phase I, each industry team is developing a different concept for the X-33 and RLV flight vehicles. The teams and concepts are described below: Lockheed Martin—Lockheed Martin's concept for both the RLV and X-33 demonstrator vehicles is a lifting body aeroshell with vertical liftoff and horizontal landing capability and horizontal processing and aircraft-like operation and support. The propulsion system of choice is an altitude-compensating linear Aerospike engine. McDonnell Douglas and Boeing—The McDonnell Douglas/Boeing team's current baseline X-33 demonstration and RLV configuration is a vertical takeoff/vertical lander; however, trade studies on other vehicle options, including horizontal landers, are also underway. The team's current propulsion choices are the near-term modified space shuttle main engine (SSME) for the X-33 and a SSME-derived engine (with high sea-level F/W) or RD-O120 Russian engine for the RLV. Rockwell International—The Rockwell concept for the RLV and X-33 vehicles is based on a wing-body approach with vertical liftoff and horizontal landing capabilities. Rockwell sees the wing-body approach as a low-risk configuration based on information from the Shuttle database. Rockwell's current propulsion choices are a near-term modified SSME for the X-33 and a SSME-derived engine (with high sea-level F/W) or the new RS-2100 engine for the RLV. DECISION CRITERIA On May 1, 1995, OMB issued a set of decision criteria that had been developed jointly by NASA, OMB, and OSTP for assessing technology maturation in preparation for an X-33 vehicle. These criteria, established in accordance with the 11-point a   Examples of NASA centers serving as subcontractors to industry include the Langley Research Center, where work is being done on a metallic TPS for McDonnell Douglas/Boeing and Lockheed Martin, and super lightweight tank development for Lockheed Martin; the Ames Research Center, where work is being done on a ceramic TPS for Rockwell International and McDonnell Douglas/Boeing; and the Marshall Space Flight Center, working on friction-stir welding for Rockwell International.

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Reusable Launch Vehicle: Technology Development and Test Program agreement between NASA and OMB that was signed by NASA Administrator Daniel S. Goldin on November 25, 1994, provide the basis for decisions to be made in 1996 and at the end of the decade about whether to proceed with Phase II (X-33 Advanced Technology Demonstration) and Phase III (Commercial Development of a Next-Generation Space Launch System). The decision criteria are consistent with the National Transportation Policy, and the relevant sections are cited in appropriate chapters of this report. STUDY TASK In the spring of 1995, the NASA Office of Space Access and Technology requested that the NRC undertake a study to examine whether the technology development and test programs planned by the prime contractors and engine companies would, indeed, provide adequate, meaningful data upon which to base a decision in December 1996. The Statement of Task is as follows: The NRC/ASEB [Aeronautics and Space Engineering Board] committee, drawing on available data and analyses, extensive briefings by NASA and its industry partners, and on information gathered in site visits to development and test facilities, will assess whether the development and test program for the propulsion and vehicle materials technologies is sufficient and appropriately structured to support a decision at the end of 1996 on whether to proceed with the X-33. In accomplishing this task, the committee will: (1) Receive briefings and data from NASA which relate the goals of the X-33 and their relationship to the requirements for a SSTO reusable launch vehicle; (2) Review the technology capabilities currently available to meet the X-33 objectives for propulsive and structural efficiency; (3) Review the analytical and development and test programs for propulsion and vehicle structures and structural materials; and: Assess whether the technology development, test and analysis programs are properly constituted to provide the information required to support a December 1996 decision to build the X-33. Suggest, as appropriate, necessary changes in these programs to ensure that they will support vehicle feasibility goals. Vehicle technologies may include cryogenic propellant tanks, cryogenic insulation, thermal protection systems, and load-carrying airframe structures, focusing on their producibility, operability, weight, and multi-flight reliability. Propulsion technologies may include bipropellant and tripropellant rocket systems, focusing on multi-mission robustness, operability, and performance. The committee will not revisit the findings

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Reusable Launch Vehicle: Technology Development and Test Program operability, and performance. The committee will not revisit the findings and recommendations of the Access to Space Study nor the roles and responsibilities assigned to NASA by the National Space Transportation Policy. In order to ensure maximum impact, emphasis will be placed on providing final findings and recommendations in a timely fashion. The report will be subject to National Research Council report review procedures prior to release. APPROACH In response to NASA's request, the NRC formed the committee on the Reusable Launch Vehicle Technology and Test Program, which met on June 20–22, July 7, July 14, July 31–August 4, August 23–25, and August 30–September 1, 1995. The committee heard extensive briefings by officials and researchers at the appropriate NASA centers and by NASA's industry partners in the RLV program and their major engine subcontractors. The committee also conducted site visits of facilities and viewed the available hardware. The first committee meeting was at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, where NASA briefed the committee on the general features of the RLV program in all areas of interest, with an emphasis on MSFC's role in providing testing facilities and expertise for propulsion systems, cryogenic tanks, and advanced technology development (e.g., friction-stir welding). To accomplish its task more efficiently, committee members were divided according to their expertise into four subgroups: propulsion systems, cryogenic tanks, primary vehicle structure (PVS), and TPS. Because of the broad charter and the short time frame, the committee composed a list of specific questions to be submitted to the presenters and briefers during subsequent meetings and site visits. The committee also decided to augment its own expertise with an independent advisor on TPS. The committee next met at the Langley Research Center in Hampton, Virginia. At this meeting, the committee learned about the computational and simulation capabilities Langley used to help define and optimize concepts for the X-33 and X-34 demonstrators and for the composite primary structures, reusable cryogenic tank systems, aluminum-lithium (Al-Li) technology, and metallic/refractory composite TPS. The committee also visited Langley's materials and structures facility and the pressure box test facility. Some committee members then visited NASA's Ames Research Center in Moffett Field, California, for a briefing on the development and test programs for advanced ceramic TPS material and the information technology for integrated health management. This group also reviewed the Ames analysis program, which incorporates various TPS tradeoffs in the vehicle design and inspected the available advanced TPS hardware. At the third full meeting, the committee met with NASA's industry partners in the RLV program (Lockheed Martin, McDonnell Douglas/Boeing, and Rockwell International) and their major engine subcontractors (Aerojet, Pratt&Whitney, and

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Reusable Launch Vehicle: Technology Development and Test Program Rocketdyne). In this week-long meeting in the Los Angeles, California, area, the committee was briefed on the details of each contractor's current vision of the RLV program and its precursor demonstrator, the X-33. As the committee had requested, the emphasis of the briefing was on technology development and test programs related to the X-33 decision and indicating the traceability to the eventual SSTO RLV. The prime contractors described their alternative vehicle concepts for the X-33 and RLV as well as the associated propulsion systems and TPSs, structural materials, and cryogenic tanks. The committee gathered data about the contractors' fall-back positions and examined facilities and hardware. The major engine subcontractors provided the committee with technical details about the propulsion systems available for immediate use in the X-33 demonstrator, as well as those that could be used with minor modifications, and described development and test programs for more advanced RLV propulsion systems. This meeting marked the conclusion of the information gathering phase of this study. Subsequently, the propulsion and TPS subgroups met at the National Academy of Sciences Beckman Center in Irvine, California, to discuss their findings and recommendations. The primary structure and cryogenic tank subgroups met in Washington, D.C. one week later to finalize their findings and recommendations. The findings and recommendations were coordinated between the two groups by teleconference. ORGANIZATION OF THE REPORT This report is organized to reflect the findings and recommendations of the full committee and the subgroups. This introductory chapter is followed by chapters on primary vehicle structures (chapter 2), cryogenic tanks (chapter 3), TPS (chapter 4), and propulsion systems (chapter 5). Each chapter begins with an introduction detailing issues and objectives specific to the technology under consideration. This is followed by the decision criteria for implementing Phase II of the RLV program, a discussion of the NASA/industry programs for meeting Phase II criteria, and the committee's technology-specific findings and recommendations. NOTES 1. National Research Council (NRC). 1987. Space Technology to Meet Future Needs. Aeronautics and Space Engineering Board. Washington, D.C.: National Academy Press. 2. National Academy of Sciences/National Academy of Engineering. 1988. Toward a New Era in Space: Realigning Policies to New Realities. Committee on Space Policy. Washington, D.C.: National Academy Press.

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Reusable Launch Vehicle: Technology Development and Test Program 3. NRC. 1992. From Earth to Orbit: An Assessment of Transportation Options. Aeronautics and Space Engineering Board. Washington, D.C.: National Academy Press. 4. National Aeronautics and Space Administration (NASA). 1990. Report of the Advisory Committee on the Future of the U.S. Space Program. Washington, D.C.: U.S. Government Printing Office. 5. Vice President's Space Policy Advisory Board. 1992. The Future of the U.S. Space Launch Capability: A Task Group Report. Washington, D.C.: U.S. Government Printing Office. 6. U.S. Congress, Office of Technology Assessment. 1995. The National Space Transportation Policy: Issues for Congress. OTA–ISS–620. Washington, D.C.: U.S. Government Printing Office. 7. Aldrich, Arnold D. 1993. Access to Space Study: Report to the Administrator. Washington, D.C.: NASA. 8. Moorman, Jr., Lt. Gen. Thomas. 1994. A briefing by the chairman of the Defense Space Launch Modernization Plan presented to the Committee on Space Facilities at the National Academy of Sciences in Washington, D.C., March 9, 1994. 9. The White House Office of Science and Technology Policy. 1994. Statement on National Space Transportation Policy. Washington, D.C.: U.S. Government Printing Office. 10. NASA. 1994. Implementation Plan for the National Space Transportation Policy . Washington, D.C.: U.S. Government Printing Office. 11. Ibid.