Reusable Launch Vehicle Technology Development and Test Program (1995) / Chapter Skim
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EXECUTIVE SUMMARY
EXECUTIVE SUMMARY
Pages 1-10
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However, the technologies required for an SSTO vehicle were considered throughout the study because the Phase T 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 Woks and primary structure are required because reaching orbit with an SSTO vehicle (using current technologies)
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There are three basic structural approaches: basic composite materials, an isognd 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-Iong DC-XA intertank; an 8-ft-diameter by 10-ft-long ground test intertank; an
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It is also important to note that various physical (and chemical) phenomena that directly affect the REV design and performance, scale ~ significantly different ways with changes in geometric size (e.g., structural strength and stability under load and thermal stress versus aerodynamic heating rates versus heat conduction through solids all interacting in the design of launch vehicle structures)
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In addition, three fabrication techniques-net shape extrusion, net shape spin forming, and net roll forging- are being considered, and two welding techniques-variable polarity plasma arc and fnction-stir welding are being developed and tested. To address scaleability issues, the REV program will fabricate and test both Aft and 14-ft diameter tanks; data from the space shuttle super lightweight tank, with a 28-ft-diameter tank, are being added to the REV Al-Li database.
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NASA and the industry partners are aware of most of these concerns; they are identified here because they are crucial to the success of the program. Major Recommendations Regarding Al-Li Cryogenic Tanks The committee's recommendations for Al-Li cryogenic tanks are as follows: Recent microstructure and texture analyses have shown that current processing methods produce excellent products.
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must be clarified for each vehicle concept, and satisfaction of predicted weight requirements must be verified using properly designed and scaled test articles. THERMAL PROTECTION SYSTEMS The current well-balanced program for developing advanced thermal protection materials addresses the key issues of significantly improved operability and reusability,
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The time and effort required after each Shuttle flight to return the vehicle to service are unacceptable in terms of turnaround time for an R:LV. Neither NASA nor the industry partners has successfully developed either agents or coatings that provide permanent waterproofing or rapid techniques of applying waterproofing to the TPS materials.
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Permissible heat-leakage rates into liquid hydrogen (LH2) and LOX propellants should be established for normal and subcooled propellants.
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The throttling and thrust vector methods proposed, including interaction effects between adjacent engines, should be evaluated. More robust and reliable health monitoring instrumentation than is currently used should be developed and thoroughly tested-.
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In addition, because of time constraints on the study, the committee could not review several important areas: . important aspects of the propulsion system such as: plumbing; leak sensors; lines, valves, and joints upstream of the engine; purge systems; pressurization systems; and the small reaction control system and orbital maneuvering system the integrated health monitoring system for all components and ODE technologies ground support equipment for the propulsion system, such as propellant quick disconnect, automation, automated fluid and electrical connections, and safe, operationally efficient ground and flight/vent purge systems operations issues that were explicitly excluded from the committee's charge to make the committee's task feasible within the allotted time
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