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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

A possibility of avoiding surface roughness due to insects

Discussion of a method for eliminating turbulence caused by the formation of insect roughness upon the leading edges and fuselage, particularly in aircraft using BLC. The proposed technique foresees the use of elastic surfaces on which insect roughness cannot form. The operational characteristics of highly elastic rubber surface fastened to the wing leading edges and fuselage edges are examined. Some preliminary test results are presented. The technique is seen to be advantageous primarily for short-haul operations.

Wortmann, F. X.↗
NASA NTRS1985

Screw-Retaining Allen Wrench

Steadying screws with fingers unnecessary. Crimp in uncompressed spring wire slightly protrudes from one facet of Allen wrench. Compressed spring retains Allen screw. Tool used with Allen-head screws in cramped spaces with little or no room for fingers to hold fastener while turned by wrench.

Granett, D.↗
NASA NTRS1986

Deployable Truss Member

Compact telescoping roll extends 24 times its length. Roll telescopes into extended truss member when force is applied. Truss members deployed by various means. Truss member initially constructed in its stowed state with appropriate sheet material rolled around central core. For deployment truss extends by centrifugal force to form cone. With both ends fastened to prevent unrolling, rigid truss member formed.

Frink, N. T.↗
NASA NTRS1984

The evolution of small payload carrier systems

The design of a bridge-like structure to span the Space Shuttle cargo bay but occupy only 3 feet of its length is discussed. The new structure was named the Missions Peculiar Equipment Support Structure (MPESS). The basic design requirements were as follows: to serve as support structure for small number of experiments; to occupy the minimal length of cargo bay; to have a standard interface hole pattern; to provide support at an elevated position; to employ standard Spacelab pallet trunnion; and to ensure natural frequency between the STS liftoff and landing frequency. The bridge-like structure is a riveted and bolted truss with machind end fittings which interface with the Spacelab trunnions. The structure is fabricated from aluminum alloy and assembled with stainless steel fasteners.

Breaux, C. G.↗
NASA NTRS1984

Bearing tester fit analysis

A NASTRAN model of the Bearing Tester was developed to determine the fit of its components while in use. The model was executed for three loading conditions involving appropriate thermal and pressure loading throughout: rotation (30,000 rpm), rotation with 5000 lb axial shaft loading, and rotation with 2000 lb lateral shaft loading. A 30 deg slice of the Bearing Tester was modeled with solid isoparametric elements (CIHEX). Five more slices were generated to form a 180 deg symmetrical half. Each component was modeled separately for two reasons: (1) in the heat transfer version each component required covering with appropriate heat transfer coefficient elements, and (2) for the displacement version each component required independent radial expansion with respect to adjacent components. The components are connected at fastener and bearing locations axially and/or tangentially. Differences in radial displacements of adjacent cylindrical surfaces were calculated and added to those differences calculated for 180 deg opposite locations to determine the diametric change.

Source record↗
NASA NTRS1985

The stress distribution in pin-loaded orthotropic plates

The performance of mechanically fastened composite joints was studied. Specially, a single-bolt connector was modeled as a pin-loaded, infinite plate. The model that was developed used two dimensional, complex variable, elasticity techniques combined with a boundary collocation procedure to produce solutions for the problem. Through iteration, the boundary conditions were satisfied and the stresses in the plate were calculated. Several graphite epoxy laminates were studied. In addition, parameters such as the pin modulus, coefficient of friction, and pin-plate clearance were varied. Conclusions drawn from this study indicate: (1) the material properties (i.e., laminate configuration) of the plate alter the stress state and, for highly orthotropic materials, the contact stress deviates greatly from the cosinusoidal distribution often assumed; (2) friction plays a major role in the distribution of stresses in the plate; (3) reversing the load direction also greatly effects the stress distribution in the plate; (4) clearance (or interference) fits change the contact angle and thus the location of the peak hoop stress; and (5) a rigid pin appears to be a good assumption for typical material systems.

Klang, E. C.↗
NASA NTRS1982

Results of tests of MTA-2 TPS on the SRB hold-down bolt blast container

The four solid rocket booster (SRB) hold-down posts are fastened to the mobile launch platform (MLP) with four large nuts. At liftoff the nuts are split with explosive changes to release the SRB/Shuttle. A blast container is placed over the nuts to protect the vehicle from flying debris. The blast container is a reusable part and has to be protected from aerodynamic heating during flight. The thermal protection system (TPS) used to protect these blast containers is cork. Fitting the flat cork sheet to this hemispherical shaped blast container is both time consuming and expensive. Another problem is removing the charred cork and epoxy glue from the blast containers. Replacements of this cork with another TPS material such as MTA-2 was examined. Heating rates along the centerline of the forward facing areas of the blast container were determined. The feasibility of using 1/2 in. MTA-2 on the SRB blast containers for protection from ascent, plume impingement and reentry heating is demonstrated.

Dean, W. G.↗
NASA NTRS1982

SRB attach ring phenolic TPS fishtail seal evaluation tests

The SRB attach ring is thermally protected with layered phenolic cloth fairings that are fastened to the ring. The gap between the fairings and the motor case is closed off with a rubber seal of a fishtail cross sectional shape bonded to the phenolic. On both the STS-1 and STS-2 flights this gap was discovered to vary anywhere from an intended gap of 0.375 in. to an actual measured gap of 0.60 in. due to tolerances. Tests were conducted with and without a 0.25 in. thick cork shim placed under the seal with a 0.60 in. gap under the phenolic TPS to determine and compare the performance of the seal in the two different configurations. To alleviate the difficult and costly procedure of installing the cork shim under the seal, especially after phenolic TPS mounting on the attach ring, large fishtail seals of idential Elder gray silicon material and two different hardnesses were tested. A similar matrix of tests was conducted with this new large fishtail seal, and seals with both type hardnesses performed well regardless of whether or not the seal was bonded in the phenolic at the front of the seal groove. Similar results had been obtained with the original small fishtail seal which performed adequately with the 0.25 in. cork shim under it.

Karu, Z. S.↗
NASA NTRS1985

Development of medical electronic devices in the APL space department

Several electronic devices for automatically correcting specific defects in a body's physiologic regulation and allowing approximately normal functioning are described. A self-injurious behavior inhibiting system (SIBIS) is fastened to the arm of a person with chronic self-injurious behavior patterns. An electric shock is delivered into the arm whenever the device senses above-threshold acceleration of the head such as occur with head-bangers. Sounding a buzzer tone with the shock eventually allows transference of the aversive stimulus to the buzzer so shocks are no longer necessary. A programmable implantable medication system features a solenoid pump placed beneath the skin and refueled by hypodermic needle. The pump functions are programmable and can deliver insulin, chemotherapy mixes and/or pain killers according to a preset schedule or on patient demand. Finally, an automatic implantible defibrillator has four electrodes attached directly to the heart for sensing electrical impulses or emitting them in response to cardiac fibrillation.

Newman, A. L.↗
NASA NTRS1984

A survey of strength analysis methods for laminates with holes

The methods for predicting the strength of composite laminates with fastener holes are reviewed for the cases of unloaded as well as loaded holes. Three categories of methods are discussed: (1) the hole-boundary stress (HBS) methods which compare the peak stresses and the laminate strength; (2) the linear elastic fracture (LEFM) methods which assume cracks emanating from the hole and predict failure when the stress intensity factor for a crack equals the laminate fracture toughness; and (3) two different two-parameter (TP) methods: the average-stress (ASTP) method, which predicts failure when the average stress over a distance from the hole equals the laminate strength; and the point-stress (PSTP) Whitney-Nuismer (1974) approach, which predicts failure when the stress near the hole equals the material strength. The PSTP is relatively accurate and is by far the most widely used of all the prediction methods. However, for large ranges of variables and cases, the current strength predictions may not always be accurate.

Crews, J. H., Jr.↗
NASA NTRS1986

Optimized Bolted Joint

Computer technique aids joint optimization. Load-sharing between fasteners in multirow bolted composite joints computed by nonlinear-analysis computer program. Input to analysis was load-deflection data from 180 specimens tested as part of program to develop technology of structural joints for advanced transport aircraft. Bolt design optimization technique applicable to major joints in composite materials for primary and secondary structures and generally applicable for metal joints as well.

Hart-Smith, L. J.↗
NASA NTRS1986

Lubricating Holes for Corroded Nuts and Bolts

Corroded fasteners taken apart more easily. Lubricating holes bored to thread from three of flats. Holes facilitate application of penetrating oil to help loosen nut when rusted onto bolt. Holes make it possible to apply lubricants and rust removers directly to more of thread than otherwise reachable.

Penn, B. G.↗
NASA NTRS1985

The Alternating Surface Segmented Lap Joint: a Design for Thin Highly Loaded Joints

The combination of thin airfoil sections and high aerodynamic loads on many wind tunnel models presents a major problem for attachment of flap elements. Conventional methods of attaching fixed control elements such as lap and tongue-in-groove joints are not rigid enough to provide surface continuity required in high Reynolds number research. For the extreme cases, the solution has been to fabricate separate wings for each flap setting with the flap element being and integral part of the wing. Here an attractive solution to this problem, the alternating surface segmented lap joint, is discussed. This joint provides increased rigidity and lower stress levels than conventional joints. Additionally, attachment fastener loading is low and the joint can be designed to accommodate high shear levels due to bending without the use of dowel pins.

Watkins, V. E., Jr.↗
NASA NTRS1985

Initial Investigation of Cryogenic Wind Tunnel Model Filler Materials

Filler materials are used for surface flaws, instrumentation grooves, and fastener holes in wind tunnel models. More stringent surface quality requirements and the more demanding test environment encountered by cryogenic wind tunnels eliminate filler materials such as polyester resins, plaster, and waxes used on conventional wind tunnel models. To provide a material data base for cryogenic models, various filler materials are investigated. Surface quality requirements and test temperature extremes require matching of coefficients of thermal expansion or interfacing materials. Microstrain versus temperature curves are generated for several candidate filler materials for comparison with cryogenically acceptable materials. Matches have been achieved for aluminum alloys and austenitic steels. Simulated model surfaces are filled with candidate filler materials to determine finishing characteristics, adhesion and stability when subjected to cryogenic cycling. Filler material systems are identified which meet requirements for usage with aluminum model components.

Firth, G. C.↗
NASA NTRS1985

Recent developments in polyimide and bismaleimide adhesives

Research on high temperature resin systems has intensified. In the Aerospace Industry, the motivation for this increased activity has been to replace heat resistant alloys of aluminum, stainless steel and titanium by lighter weight glass and carbon fiber reinforced composites. Applications for these structures include: (1) engine nacelles involving long time exposure (thousands of hours) to temperatures in the 150 to 300 C range, (2) supersonic military aircraft involving moderately long exposure (hundreds of hours) to temperatures of 150 to 200 C, and (3) missile applications involving only brief exposure (seconds or minutes) to temperatures up to 500 C and above. Because of fatigue considerations, whenever possible, it is preferable to bond rather than mechanically fasten composite structures. For this reason, the increased usage of high temperature resin matrix systems for composites has necessitated the devlopment of compatible and equally heat stable adhesive systems. The performance of high temperature epoxy, epoxy phenolic and condensation polyimide adhesives is reviewed. This is followed by a discussion of three recently developed types of adhesives: (1) condensation reaction polyimides having improved processing characteristics; (2) addition reaction polyimides; and (3) bismaleimides.

Politi, R. E.↗
NASA NTRS1985

Design and construction of models for the National Transonic Facility, part 2

This lecture presents the results of fastener load and retention systems tests which were carried out as a part of the cryogenic models technology development program a the NASA Langley Research Center (LaRC). Various design concepts for the National Transonic Facility (NTF) developmental and production models are discussed. A number of NTF models are described with emphasis on materials used, uniqueness of design and design drivers. Design and fabrication experience is presented in terms of the primary thermal and mechanical considerations required for design as well as fabrication. Cost considerations are addressed in terms of factors influencing costs for NTF models and cost data comparisons which are taken from both NASA Langley and industry experience.

Young, C. P., Jr.↗
NASA NTRS1985

Segmented tubular cushion springs and spring assembly

A spring which includes a tube with an elliptical cross section, with the greater axial dimension extending laterally and the lesser axial dimension extending vertically is disclosed. A plurality of cuts in the form of slots passing through most of a wall of the tube extend perpendiculary to a longitudinal axis extending along the tube. An uncut portion of the tube wall extends along the tube for bonding or fastening the tube to a suitable base, such as a bottom of a seat cushion.

Haslim, L. A.↗
NASA NTRS1985

Self-locking double retention redundant full pin release

A double retention redundant pull pin release system is disclosed. The system responds to a single pull during an intentional release operation. A spiral threaded main pin is seated in a mating bore in a housing, which main pin has a flange fastened thereon at the part of the main pin which is exterior to the housing. Accidental release tends to rotate the main pin. A secondary pin passes through a slightly oversized opening in the flange and is seated in a second bore in the housing. The pins counteract against one another to prevent accidential release. A frictional lock is shared between the main and secondary pins to enhance further locking of the system. The secondary pin, in response to a first pull, is fully retracted from its bore and flange hole. Thereafter the pull causes the main pin to rotate free of the housing to release, for example, a parachute mechanism.

Killgrove, T. O.↗