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At least 433 records · Page 24

All sources NASA NTRS DOE OSTI

NASA NTRS1980

Automated beam builder

Requirements for the space fabrication of large space structures are considered with emphasis on the design, development, manufacture, and testing of a machine which automatically produces a basic building block aluminum beam. Particular problems discussed include those associated with beam cap forming; brace storage, dispensing, and transporting; beam component fastening; and beam cut-off. Various critical process tests conducted to develop technology for a machine to produce composite beams are also discussed.

Muench, W. K.↗

NASA NTRS1980

Thermal performance of a mechanically attached ablator tile for on-orbit repair of shuttle TPS

The reusable surface insulation (RSI) material used in the shuttle thermal protection system is susceptible to damage. If any RSI tiles are damaged or lost during ascent, they must be repaired or replaced prior to entry. One approach to replacing a damaged or missing RSI tile consists of mechanically attaching a tile of ablation material in the place of the RSI tile. The thermal performance of this type of repair tile was evaluated in a simulated entry heating environment. The test specimen consisted of the ablator repair tile mechanically fastened to the strain isolation pad and surrounded by RSI tiles. The evaluation of the thermal performance was based on temperature response, surface integrity, and predicted flight performance. When the ablator tile protruded 1/8 inch above the surrounding RSI tiles, the forward facing steps caused significant inflow of hot gas down the ablator RSI joints and this inflow caused greatly increased back surface temperatures.

Thompkins, S. S.↗

NASA NTRS1980

Notch sensitivity of space shuttle tile materials

Tests were conducted at room temperature to determine the notch sensitivity of the thermal protection tile for the space shuttle. Two types of RSI tile were studied: LI-900 and LI-2200. Three point bend specimens were cut from discarded tiles in the in-plane (ip) and through-the-thickness (ttt) directions. They were tested with or without a sharp notch. The LI-900 (ip and ttt) specimens were not very notch sensitive, but the LI-2200 (ip and ttt) specimens were. The LI-2200 material showed about a 35 percent reduction in strength due to the presence of the notch. This reduction in strength should be considered in the design of mechanically fastened tile concepts.

Newman, J. C., Jr.↗

NASA NTRS1980

Small Transport Aircraft Technology

The article surveys the results of the NASA-instituted Small Transport Aircraft Technology (STAT) research effort aimed at generating advanced technologies for application to new small, short haul transports having significantly better performance, efficiency, and environmental compatibility. Discussion covers fuselage designs and bonded aluminum-honeycomb wing construction which reduces the number of parts and fasteners, and gives a smoother outer contour. Topics discussed include: advanced aluminum alloys, composite primary structures, propellers, engine components, icing protection, avionics, flight controls, aerodynamics, and gust load alleviation.

Galloway, T. L.↗

NASA NTRS1982

Recharging the Silicon Crucible in a Hot Furnace

"Melt recharger" adds raw silicon to crucible in crystal-growing furnace without disturbing inert-gas atmosphere or significantly lowering temperature of melt. Crucible-refill hopper is lowered into hot zone of crystal-pulling chamber through an isolation valve. Cable that supports hopper is fastened to cone-shaped stopper in bottom of hopper. Stopper moves out of opening in hopper, allowing part of polysilicon charge to drop into crucible.

Lane, R. L.↗

NASA NTRS1982

Shaping Transistor Leads for Better Solder Joints

Special lead-forming tool puts step in leads of microwave power transistors without damaging braze joints that fasten leads to package. Stepped leads are soldered to circuit boards more reliably than straight leads, and stress on brazes is relieved. Lead-forming hand-tool has two parts: a forming die and an actuator. Spring-loaded saddle is adjusted so that when transistor package is placed on it, leads rest on forming rails.

Mandel, H.↗

NASA NTRS1982

Safety Bolt Doubles as a Bushing-Removal Tool

Bushings fitted to close tolerances and limited access can be removed without damage to housing by using bolt with integrated locking dog. Such self-retaining positive - locking bolts are normally used as fasteners in critical joints where accidentally loosened bolt could cause damage or injuries.

Haverkamp, C. E.↗

NASA NTRS1982

Ultrasonic Welding of Graphite/Thermoplastic Composite

Ultrasonic welding of graphite/thermoplastic composite materials eliminates need for fasteners (which require drilling or punching, add weight, and degrade stiffness) and can be totally automated in beam fabrication and assembly jigs. Feasibility of technique has been demonstrated in laboratory tests which show that neither angular orientation nor vacuum affect weld quality.

Hardy, S. S.↗

NASA NTRS1980

Autoregulation of cerebral blood circulation under orthostatic tests

Autoregulation of cerebral blood flow (ACBF) under orthostatic tests (OT) was estimated in acute experiments on rabbits and cats under local anesthesia according to changes of perfusion pressure (PP) in carotid arteries, cerebral blood flow, pressure in the venous system of the brain, and resistance of cerebral vessels. The OT were conducted by turning a special table with the animal fastened to it from a horizontal to a vertical (head up or head down) position at 40 to 80 deg. In most experiments ACBF correlated with the changes of PP. Different variations of ACBF and its possible mechanisms are discussed.

Gayevyy, M. D.↗

NASA NTRS1978

Advanced composite aileron for L-1011 transport aircraft, task 1

Structural design and maintainability criteria were established and used as a guideline for evaluating a variety of configurations and materials for each of the major subcomponents. From this array of subcomponent designs, several aileron assemblies were formulated and analyzed. The selected design is a multirib configuration with sheet skin covers mechanically fastened to channel section ribs and spars. Qualitative analysis of currently available composite material systems led to the selection of three candidate materials on which comparative structural tests were conducted to measure the effects of environment and impact damage on mechanical property retention. In addition, each system was evaluated for producibility characteristics. From these tests, Thornel 300/5208 unidirectional tape was selected for the front spar and covers, and Thornel 300 fabric/5208 was chosen for the ribs.

Griffin, C. F.↗

NASA NTRS1981

Design and fabrication of a stringer stiffened discrete-tube actively cooled panel for a hypersonic aircraft

A 0.61 x 1.22 m (2 x 4 ft) test panel was fabricated and delivered to the Langley Research Center for assessment of the thermal and structural features of the optimized panel design. The panel concept incorporated an aluminum alloy surface panel actively cooled by a network of discrete, parallel, redundant, counterflow passage interconnected with appropriate manifolding, and assembled by adhesive bonding. The cooled skin was stiffened with a mechanically fastened conventional substructure of stringers and frames. A 40 water/60 glycol solution was the coolant. Low pressure leak testing, radiography, holography and infrared scanning were applied at various stages of fabrication to assess integrity and uniformity. By nondestructively inspecting selected specimens which were subsequently tested to destruction, it was possible to refine inspection standards as applied to this cooled panel design.

Anthony, F. M.↗

NASA NTRS1981

Comparative evaluation operability of large space structure connectors

The evaluation of several connector concepts in the neutral buoyancy simulator is discussed. Parameters for evaluating the fasteners included subject comments and hardware damage. Evaluation results include a rank ordering of the candidates with descriptions of the acceptable and unacceptable points of each. General design recommendations established as a result of neutral buoyancy testing are defined. Recommendations include detailed hardware and operational design requirements.

Stokes, J. W.↗

NASA NTRS1981

Integrated residential photovoltaic array development

Sixteen conceptual designs of residential photovoltaic arrays are described. Each design concept was evaluated by an industry advisory panel using a comprehensive set of technical, economic and institutional criteria. Key electrical and mechanical concerns that effect further array subsystem development are also discussed. Three integrated array design concepts were selected by the advisory panel for further optimization and development. From these concepts a single one will be selected for detailed analysis and prototype fabrication. The three concepts selected are: (1) An array of frameless panels/modules sealed in a T shaped zipper locking neoprene gasket grid pressure fitted into an extruded aluminum channel grid fastened across the rafters. (2) An array of frameless modules pressure fitted in a series of zipper locking EPDM rubber extrusions adhesively bonded to the roof. Series string voltage is developed using a set of integral tongue connectors and positioning blocks. (3) An array of frameless modules sealed by a silicone adhesive in a prefabricated grid of rigid tape and sheet metal attached to the roof.

Royal, G. C., III↗

NASA NTRS1981

Flight service evaluation of kevlar-49 epoxy composite panels in wide-bodied commercial transport aircraft: Flight service report

Kevlar-49 fairing panels, installed as flight service components on three L-1011s, were inspected after 7 years service. There are six Kevlar-49 panels on each aircraft: a left hand and right hand set of a wing-body sandwich fairing; a slid laminate under-wing fillet panel; and a 422 K service aft engine fairing. The three L-1011s include one each in service with Eastern, Air Canada, and TWA. The fairings have accumulated a total of 52,500 hours, with one ship set having 17.700 hours service. The inspections were conducted at the airlines' major maintenance bases with the participation of Lockheed Engineering. The Kevlar-49 components were found to be performing satisfactorily in service with no major problems or any condition requiring corrective action. The only defects noted were minor impact damage and a minor degree of fastener hole fraying and elongation. These are for the most part comparable to damage noted on fiberglass fairings. The service history to date indicates that Kevlar-49 epoxy composite materials have satisfactory service characteristics for use in aircraft secondary structure.

Stone, R. H.↗

NASA NTRS1981

Composite beam builder

The building block approach to large space structures is discussed, and the progress made in constructing aluminum beams is noted. It is pointed out that composites will also be required in space structures because they provide minimal distortion characteristics during thermal transients. A composite beam builder currently under development is discussed, with attention given to cap forming and the fastening of cross-braces. The various composite materials being considered are listed, along with certain of their properties. The need to develop continuous forming stock up to 300 m long is stressed.

Poveromo, L. M.↗

NASA NTRS1982

Oxidation-Strengthened High-Temperature Rivets

Shear strength of titanium-niobium rivets improves with oxidation. Ti-Nb rivets developed for fastening parts of Space Shuttle thrustors may be suitable also for other high-temperature applications in oxidizing environments--for example, in burner cans of commercial jet engines and boilers and retorts for coal gasification systems.

Mclemore, R. L.↗

NASA NTRS1982

Self-Alining, Latching Joint For Folding Structural Elements

Structural column elements assembled quickly and easily with aid of new center joint. Joint alines column elements automatically and fastens them together securely. Tapered half columns are stacked like paper cups, unfolded, and connected to other similar elements to form truss structures.

Bush, H. G.↗

NASA NTRS1982

Tool Preloads Screw and Applies Locknut

Special tool reaches through structural members inside Space Shuttle fasten nut on preloaded screw that holds thermal protection tile against outside skin of vehicle. Tool attaches tiles with accuratelycontrolled tensile loading.

Wood, K. E.↗