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At least 1,513 records · Page 84

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NASA NTRS1983

Hydrazine gas generator performance on Space Shuttle

The design, functions, performance, and applications of the hydrazine gas generators (GG) on the STS are detailed. The GGs provide gas horse power for the APUs that drive the hydraulic pumps on the SRBs, which have two cross-linked systems. The Orbiter has three-cross-linked APU systems, used for gimballing the main engine and booster nozzles, actuating the main engine fuel valves and the ET umbilical disconnect, actuation of the control surfaces, and powering the landing gear, brakes, and nose wheel steering. The major design components of the Orbiter GGs are an injector, a catalyst bed, a decomposition chamber, an exhaust nozzle, and an interface structure, with the main structural material being Hasteloy B. Hydrazine injected and dispersed into the catalyst bed decomposes into gas and exits for expansion in an APU turbine. Twenty-six GGs have flown on missions STS-1 through STS-6 with over three tons of hydrazine having been expended over 44 hr of operations, as no refurbishment to that point was necessary.

Patterson, I. J.↗

NASA NTRS1983

Stress intensity factors in two bonded elastic layers containing cracks perpendicular to and on the interface. I Analysis. II - Solution and results

The basic crack problem which is essential for the study of subcritical crack propagation and fracture of layered structural materials is considered. Because of the apparent analytical difficulties, the problem is idealized as one of plane strain or plane stress. An additional simplifying assumption is made by restricting the formulation of the problem to crack geometries and loading conditions which have a plane of symmetry perpendicular to the interface. The general problem is formulated in terms of a coupled systems of four integral equations. For each relevant crack configuration of practical interest, the singular behavior of the solution near and at the ends and points of intersection of the cracks is investigated and the related characteristic equations are obtained. The edge crack terminating at and crossing the interface, the T-shaped crack consisting of a broken layer and a delamination crack, the cross-shaped crack which consists of a delamination crack intersecting a crack which is perpendicular to the interface, and a delamination crack initiating from a stress-free boundary of the bonded layers are some of the practical crack geometries considered. Previously announced in STAR as N80-18428 and N80-18429

Lu, M.-C.↗

NASA NTRS1983

Observations of severe in-flight environments on airplane composite structural components

The development of relatively inexpensive, highly sophisticated avionics systems makes it now possible for general aviation aircraft to fly under more severe weather conditions than formerly. Increased instrument flying increases exposure of aircraft to potentially severe thunderstorm activity such as high rain rates, hail stones, and lightning strikes. In particular, the effects of lightning on aircraft can be catastrophic. Interest in aircraft lightning protection has been stimulated by the introduction of advanced composites as an aircraft structural material. The present investigation has the objective to report experiences with three composite components which have flown in thunderstorms, taking into account three F-106B composite fin caps. The only visible lightning strike damage to a flame sprayed aluminum coated glass/epoxy fin cap was a small area of the aluminum which was burned. Visible lightning strike damage to a Kevlar/epoxy fin cap was limited to the exterior ply of aluminum coated glass fabric. In the case of a graphite/epoxy fin cap, lightning currents could be conducted.

Howell, W. E.↗

NASA NTRS1984

Fatigue and Fracture Branch: A compendium of recently completed and on-going research projects

This compendium of recently completed and ongoing research projects from the Fatigue and Fracture Branch at NASA Langley Research Center provides technical descriptions and key results of all such projects expected to lead to publication of significant findings. The common thread to all these studies is the application of fracture mechanics analyses to engineering problems in metals and composites, with particular emphasis on airframe structural materials. References to recent publications are included where appropriate.

Elber, W.↗

NASA NTRS1983

Aging results for PRD 49 III/epoxy and Kevlar 49/epoxy composite pressure vessels

Kevlar 49/epoxy composite is growing in use as a structural material because of its high strength-to-weight ratio. Currently, it is used for the Trident rocket motor case and for various pressure vessels on the Space Shuttle. In 1979, the initial results for aging of filament-wound cylindrical pressure vessels which were manufactured with preproduction Kevlar 49 (Hamstad, 1979) were published. This preproduction fiber was called PRD 49 III. This report updates the continuing study to 10-year data and also presents 7.5-year data for spherical pressure vessels wound with production Kevlar 49. For completeness, this report will again describe the specimens of the original study with PRD 49 as well as specimens for the new study with Kevlar 49.

Hamstad, M. A.↗

NASA NTRS1983

Fused silica mirror evaluation for the Shuttle Infrared Telescope Facility (SIRTF)

The SIRTF optics are intended for operation at 20 K (or less); it will be extremely inconvenient, expensive, and time consuming if it becomes necessary to accomplish all of the optical element testing, assembly, and alignment at comparable temperatures. The thermal strain behavior, including potential anisotropies and inhomogeneities, of a mirror substrate between room temperature and 20 K thus becomes a major factor in the selection of the substrate material, structural configuration, and joining methods for lightweight structures. With support from Space Projects, NASA Ames Research Center, an optical figure evaluation of a 0.65-meter, lightweight, fused silica mirror at a low-temperature goal of 20 K is being conducted. The design details of a thermal shroud, provisions for extracting heat from the low-conductivity mirror, and wavefront error sources other than the mirror surface are discussed and preliminary test results presented.

Barnes, W. P., Jr.↗

NASA NTRS1984

Concepts, technology, and operations for a quick response, highly maneuverable launch vehicle

Preliminary results from the NASA orbit-on-demand study are used to identify major technology issues for development of a quick response vehicle. Reasonable vehicles are found to require significant advances in propulsion, structures, materials, and flight mechanics technology. Vehicle concepts using normal growth technology predicted for the 1990s are compromised by expendable hardware or by unmanageable size and complexity. Operational analyses of the vertical-launch and horizontal-launch takeoff vehicles show that the latter have more inherent operational utility. The supply of liquid hydrogen propellant at alternate sites is a major issue; however, propane may be a viable option for at least one concept. Propellant for orbital maneuvering significantly increases gross weight for many of the concepts. This increase is greater for horizontal-takeoff systems becasue of their larger orbiters.

Gabris, E. A.↗

NASA NTRS1984

Aeronautics Technology Possibilities for 2000: Report of a workshop

The potential of aeronautical research and technology (R&T) development, which could provide the basis for facility planning and long range guidance of R&T programs and could establish justification for support of aeronautical research and technology was studied. The projections served specific purposes: (1) to provide a base for research and future facilities needed to support the projected technologies, and development advanced vehicles; (2) to provide insight on the possible state of the art in aeronautical technology by the year 2000 for civil and military planners of air vehicles and systems. Topics discussed include: aerodynamics; propulsion; structures; materials; guidance, navigation and control; computer and information technology; human factors; and systems integration.

Source record↗

NASA NTRS1984

Unidirectional fibers and polyurethane elastomer matrix based composites synthesis and properties

A study of the properties and manufacturing techniques for long-fiber reinforced elastomeric composites for flexible and damping structural materials is presented. Attention is given to the usage of polyurethane in the matrix to obtain plastic elastomeric matrices and vitreous transition temperatures which vary from -80 C to 10 C, as well as assure good fiber adhesion. Various polyurethane formulations synthesized from diisocyanate prepolymers are examined in terms of mechanical and thermal properties. The principal reinforcing fiber selected is a unidirectional glass cloth.

Chakar, A.↗

NASA NTRS1984

Heat pipe cooled probe

The basic heat pipe principle is employed to provide a self-contained passively cooled probe that may be placed into a high temperature environment. The probe consists of an evaporator region of a heat pipe and a sensing instrument. Heat is absorbed as the working fluid evaporates in the probe. The vapor is transported to the vapor space of the condenser region. Heat is dissipated from the condenser region and fins causing condensation of the working fluid, which returns to the probe by gravity and the capillary action of the wick. Working fluid, wick and condenser configurations and structure materials can be selected to maintain the probe within an acceptable temperature range.

Camarda, C. J.↗

NASA NTRS1985

Large Space Antenna Systems Technology, 1984

Papers are presented which provide a comprehensive review of space missions requiring large antenna systems and of the status of key technologies required to enable these missions. Topic areas include mission applications for large space antenna systems, large space antenna structural systems, materials and structures technology, structural dynamics and control technology, electromagnetics technology, large space antenna systems and the space station, and flight test and evaluation.

Boyer, W. J.↗

NASA NTRS1985

Large Space Antenna Systems Technology, 1984

Mission applications for large space antenna systems; large space antenna structural systems; materials and structures technology; structural dynamics and control technology, electromagnetics technology, large space antenna systems and the Space Station; and flight test and evaluation were examined.

Boyer, W. J.↗

NASA NTRS1985

The composition of the primitive atmosphere and the synthesis of organic compounds on the early Earth

The generally accepted theory for the origin of life on the Earth requires that a large variety of organic compounds be present to form the first living organisms and to provide the energy sources for primitive life either directly or through various fermentation reactions. This can provide a strong constraint on discussions of the formation of the Earth and on the composition of the primitive atmosphere. In order for substantial amounts of organic compounds to have been present on the prebiological Earth, certain conditions must have existed. There is a large body of literature on the prebiotic synthesis of organic compounds in various postulated atmospheres. In this mixture of abiotically synthesized organic compounds, the amino acids are of special interest since they are utilized by modern organisms to synthesize structural materials and a large array of catalytic peptides.

Bada, J. L.↗

NASA NTRS1985

Research and development activities in unified control-structure modeling and design

Results of work to develop a unified control/structures modeling and design capability for large space structures modeling are presented. Recent analytical results are presented to demonstrate the significant interdependence between structural and control properties. A new design methodology is suggested in which the structure, material properties, dynamic model and control design are all optimized simultaneously. Parallel research done by other researchers is reviewed. The development of a methodology for global design optimization is recommended as a long-term goal. It is suggested that this methodology should be incorporated into computer aided engineering programs, which eventually will be supplemented by an expert system to aid design optimization.

Nayak, A. P.↗

NASA NTRS1984

Technology for space station

Some of the most significant advances made in the space station discipline technology program are examined. Technological tasks and advances in the areas of systems/operations, environmental control and life support systems, data management, power, thermal considerations, attitude control and stabilization, auxiliary propulsion, human capabilities, communications, and structures, materials, and mechanisms are discussed. An overview of NASA technology planning to support the initial space station and the evolutionary growth of the space station is given.

Colladay, R. S.↗

NASA NTRS1984

Aeronautical technology 2000 - A projection of advanced vehicle concepts

At the request of NASA and under the aegis of the National Research Council, representatives from industry, academic institutions and government have participated in a workshop to consider opportunities for the exploitation of aircraft technology in such fields as aerodynamics, materials, structures, guidance, navigation and control, human factors, propulsion, computers and data processing, and systems integration. Attention is given to the advanced vehicle concepts that have emerged for possible year-2000 implementation, which encompass such diverse aircraft types as supersonic transports, hypersonic airliners, missiles, and interceptors, transatmospheric vehicles, next-generation space shuttles, subsonic transports and attack aircraft, advanced helicopter, tilt-rotor VTOL configurations, and solar- and microwave beam-powered extremely high altitude aircraft.

Rosen, C. C., III↗

NASA NTRS1985

Using a life-cycle-cost criterion for multi-disciplinary design studies for the Manned Space Station

A life-cycle-cost measure for the Manned Space Station is suggested which considers the mass, initial cost, aerodynamic drag, electrical power, moment, required ground support, and expected life of subsystems or components. It is proposed that this life-cycle-cost measure be considered as a criterion for design trade-off studies involving controls and structures. Calculating the related sensitivities in the optimization process is discussed and then applied to specific examples. In the first example, the reaction control system is analyzed with regard to the design of its supporting structure and selection of rocket type. Values of support beam length, structural material selection, and rocket propellant selection are determined which minimize life-cycle-cost. In the second example, the alignment of solar arrays are analyzed for efficiency with regard to generating power, their drag, and their aerodynamic moment. Alignment angles are determined which again minimize life cycle cost. It seems clear from these and other examples that the proposed criterion has value for multi-disciplinary design studies for the Manned Space Station.

Taylor, L. W.↗

NASA NTRS1984

The trend of future gas turbine technology

Future gas turbine technology will be based on contributions to the technology base being made today. At the NASA Lewis Research Center in Cleveland, OH, research is being conducted on turbomachinery system components and in a number of associated disciplines to advance the technology of aviation turbofan and torbojet engines. Areas of research include compressors, turbines, internal flow analysis, combustion, fuels, materials, structures, bearings, seals, lubrication, dynamics and controls, and instrumentation. A review of the research directions being taken in these areas and the steady advances being made provides a reasonable glimpse at gas turbine technology of the future.

Hartmann, M. J.↗