Reusable Launch Vehicle: Technology Development and Test Program - Softcover

National Research Council; Division On Engineering And Physical Sci; Commission On Engineering And Technical

Softcover

ISBN 10: 0309054370 ISBN 13: 9780309054379

Verlag: NATL ACADEMY PR, 1996

Inhaltsangabe

The key to opening the use of space to private enterprise and to broader public uses lies in reducing the cost of the transportation to space. More routine, affordable access to space will entail aircraft-like quick turnaround and reliable operations. Currently, the space Shuttle is the only reusable launch vehicle, and even parts of it are expendable while other parts require frequent and extensive refurbishment. NASA's highest priority new activity, the Reusable Launch Vehicle program, is directed toward developing technologies to enable a new generation of space launchers, perhaps but not necessarily with single stage to orbit capability. This book assesses whether the technology development, test and analysis programs in propulsion and materials-related technologies are properly constituted to provide the information required to support a December 1996 decision to build the X-33, a technology demonstrator vehicle; and suggest, as appropriate, necessary changes in these programs to ensure that they will support vehicle feasibility goals.

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Committee on Reusable Launch Vehicle Technology and Test Program, National Research Council

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REUSABLE LAUNCH VEHICLE

Technology Development and Test Program

National Academies Press

Copyright © 1995 National Academy of Sciences
All right reserved.
ISBN: 978-0-309-05437-9

Chapter One

Executive Summary

The objective of the National Aeronautics and Space Administration (NASA) Reusable Launch Vehicle (RLV) Program is to develop technology and demonstrations for providing reliable, low cost access to space. Phase I of the RLV program consists of concept definition and technology development leading to a Phase II subscale flight demonstration vehicle, the X-33. Shortly after the NASA Office of Space Access and Technology requested that the National Research Council (NRC) examine the RLV Phase I technology development and test program, decision criteria for this phase were developed by NASA, the Office of Management and Budget (OMB), and the Office of Science and Technology Policy (OSTP); these criteria are cited in the body of the report. The NRC committee took these criteria into consideration when making judgments about whether the Phase I program would provide adequate information to "support a decision no later than December 1996 [whether] to proceed with a subscale launch vehicle flight demonstration which would prove the concept of single-stage-to-orbit (SSTO)." However, it needs to be emphasized that the committee assessed the extent to which the technology development programs represent rational paths (and alternatives) toward RLV goals. The NRC task was limited to the Phase I propulsion and materials technology programs; the NRC was asked not to assess the feasibility of SSTO. However, the technologies required for an SSTO vehicle were considered throughout the study because the Phase I development and test programs are structured to focus on three crucial areas in the development of a cost-effective SSTO vehicle: lightweight materials for the tanks and primary structure, efficient propulsion systems, and multimission reusability and operability.

Materials considerably lighter than those currently used for the tanks and primary structure are required because reaching orbit with an SSTO vehicle (using current technologies) requires that about 90 percent of the vehicle's total mass at launch be propellant. In the propulsion area, a significant improvement in the thrust-to-weight (F/W) ratio (sea-level) of the engines is necessary-compared to the F/W ratio of the two existing large-thrust liquid oxygen/liquid hydrogen engines, the Russian RD-0120 and the U.S. space shuttle main engine (SSME).

Achieving orbit with the required payload is only part of the challenge that has been undertaken in the NASA/industry RLV program. The other, equally important challenge is to demonstrate a system that is capable of achieving a lower cost per launch and be clearly competitive with other launchers worldwide. In the case of SSTO and maximum reusability, all of the components for the vehicle primary structures, the cryogenic tanks, the thermal protection system (TPS), and the propulsion system must first be developed. Then it must be demonstrated that these components are reusable with minimal inspections or replacements for at least 20 missions and have a lifetime of at least 100 missions.

The committee reviewed the RLV program and found the three phase approach to the program to be sound. Phase I of the program includes demonstrations of critical technologies. These demonstrations will be required before proceeding with the more costly, largely subscale flight demonstrations of Phase II. The committee found that the Phase I development, test, and analysis programs are appropriate to support a decision about proceeding with Phase II, subject to implementation of the committee's recommendations.

Three prime contractors have proposed three distinct RLV designs and are pursuing different paths in critical technology areas (in some instances a given contractor is pursuing several paths at this stage). NASA centers are providing supporting and complementary research and development in many instances; thus, if there is a failure along one path, alternative paths may be pursued. Phase II must successfully demonstrate that the technical challenges have been met before industry teams can proceed with costly, full-scale RLV development in Phase III. Using this phased approach, NASA can avoid the high development costs and technical risks of previous programs that depended on significant technological advances being concurrent with vehicle development.

The committee studied the four major technology areas in Phase I of the RLV program: composite primary structures, aluminum-lithium (Al-Li) and composite cryogenic tanks, TPS, and propulsion systems. However, the committee did not address issues of design integration of component technologies into flight vehicle configurations. In any event, because of the current stage of vehicle design by industry partners and NASA, it was not feasible for the committee to make definitive assessments. The committee's recommendations reflect those aspects of the technology programs believed to require special emphasis. Other important aspects of the programs, even those involving significant challenges, were not addressed in the report if the committee believed that the participating industrial teams and NASA were not only well aware of the challenges but were also paying sufficient attention to meeting them in the program plans. The major findings and recommendations in each of the four technological areas crucial to Phase I are discussed below.

COMPOSITE PRIMARY STRUCTURES

The technology development program is robust, well organized, and addresses all of the major issues. There are three basic structural approaches: basic composite materials, an isogrid design for the intertank, and a sandwich structure design being developed by a NASA center. Major contractor test articles include an 8-ft-diameter by 38- inch-long DC-XA intertank; an 8-ft-diameter by 10-ft-long ground test intertank; an 8-ft-diameter filament-wound isogrid, a one-fourth segment of a full-sized intertank (designed to address scaleability concerns); a segment of a full-scale thrust structure; and a full-scale wing box section for one of the RLV configurations. NASA centers are providing considerable analyses, material characterization, and subscale component tests, as well as an intertank/cryotank interface with a joint that is 8 ft in diameter and 6.5 ft long. Under cooperative agreements with industry, NASA also will provide structural test articles for system-level tests. Many of these test articles will be subjected to combined-load testing for life cycle; and some will undergo acoustic and damage-tolerance testing. Integrated health monitoring systems will be attached to many of the full-scale segments during testing.

Efforts to validate analysis techniques and to address scaleability to single stage RLVs is progressing satisfactorily. Testing ranges from extensive coupon and other subscale tests, to panel tests, to reasonably large test articles and includes continuous validation of the necessary predictive tools at every stage.

Although the approach is sound, the committee is concerned about the 15 percent maximum weight growth margin specified by the program managers; 20 to 25 percent weight growth is typical during the early stage of design development. The need to control weight growth tightly this early in the program places a premium on accurate calculation of structural performance and weight and on early verification that the...

Details zur Ausgabe

• Verlag: NATL ACADEMY PR
• Erscheinungsdatum: 1996
• Sprache: Englisch
• ISBN 10: 0309054370
• ISBN 13: 9780309054379
• Einband: Taschenbuch
• Anzahl der Seiten: 98
• Kontakt zum Hersteller: Nicht verfügbar
• Verantwortliche Person: Nicht verfügbar