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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Experimental investigation of dynamic ground effect

A 60-degree delta wing, an F-106B, and an XB-70 model with and without flap deflections were tested in static and dynamic ground effect in the 36-by-51-inch subsonic wind tunnel at the University of Kansas. Dynamic ground effect was measured with movable sting support. For flow visualization, a tufted wire grid was mounted on the movable sting behind the model. Test results showed that lift and drag increments in dynamic ground effect were always lower than static values. Effect of the trailing edge flap deflections on lift increments was slight. The fuselage reduced the lift increments at a given ground height. From flow visualization under static conditions, the vortex core was seen to enlarge as the ground was approached.

Lee, Pai-Hung↗
NASA NTRS2004

Foreign Object Damage Behavior of a SiC/SiC Composite at Ambient and Elevated Temperatures

Foreign object damage (FOD) behavior of a gas-turbine grade SiC/SiC ceramic matrix composite (CMC) was determined at 25 and 1316 C, employing impact velocities from 115 to 440 meters per second by 1.59-mm diameter stell-ball projectiles. Two different types of specimen support were used at each temperature: fully supported and partially supported. For a given temperature, the degree of post-impact strength degradation increased with increasing impact velocity, and was greater in a partially supported configuration than in a fully supported one. The elevated-temperature FOD resistance of the composite, particularly under partially supported loading at higher impact velocities greater than or equal to 350 meters per second, was significantly less than the ambient-temperature counterpart, attributed to a weakening effect of the composite. For fully supported loading, frontal contact stress played a major role in generating composite damage; whereas, for partially supported loading, both frontal contact and backside bending stresses were combined sources of damage generation. The SiC/SiC composite was able to survive higher energy impacts without complete structural failure but suffered more strength affecting damage from low energy impacts than AS800 and SN282 silicon nitrides.

Bhatt, Ramakrishna T.↗
NASA NTRS1984

Cell wall pH and auxin transport velocity

According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

Plant Growth Regulators/metabolism↗
NASA NTRS1943

Large-deflection theory for end compression of long rectangular plates rigidly clamped along two edges

The von Karman equations for flat plates are solved beyond the buckling load up to edge strains equal to eight time the buckling strain, for the extreme case of rigid clamping along the edges parallel to the load. Deflections, bending stresses, and membrane stresses are given as a function of end compressive load. The theoretical values of effective width are compared with the values derived for simple support along the edges parallel to the load. The increases in effective width due to rigid clamping drops from about 20 percent near the buckling strain to about 8 percent at an edge strain equal to eight times the buckling strain. Experimental values of effective width in the elastic range reported in NACA Technical Note No. 684 are between the theoretical curves for the extremes of simple support and rigid clamping.

Levy, Samuel↗
NASA NTRS2010

KSC VAB Aeroacoustic Hazard Assessment

NASA Kennedy Space Center (KSC) carried out an analysis of the effects of aeroacoustics produced by stationary solid rocket motors in processing areas at KSC. In the current paper, attention is directed toward the acoustic effects of a motor burning within the Vehicle Assembly Building (VAB). The analysis was carried out with support from ASRC Aerospace who modeled transmission effects into surrounding facilities. Calculations were done using semi-analytical models for both aeroacoustics and transmission. From the results it was concluded that acoustic hazards in proximity to the source of ignition and plume can be severe; acoustic hazards in the far-field are significantly lower.

Oliveira, Justin M.↗
NASA NTRS1990

Deep space telecommunications, navigation, and information management - Support of the Space Exploration Initiative

The principal challenges in providing effective deep space navigation, telecommunications, and information management architectures and designs for Mars exploration support are presented. The fundamental objectives are to provide the mission with the means to monitor and control mission elements, obtain science, navigation, and engineering data, compute state vectors and navigate, and to move these data efficiently and automatically between mission nodes for timely analysis and decision making. New requirements are summarized, and related issues and challenges including the robust connectivity for manned and robotic links, are identified. Enabling strategies are discussed, and candidate architectures and driving technologies are described.

Hall, Justin R.↗
NASA NTRS1987

An experimental investigation of dynamic ground effect

Sixty degree delta wing, F-106B, and XB-70 models with and without flap deflections were tested in static and dynamic ground effect in the 36 by 51 inch subsonic wind tunnel at the University of Kansas. Dynamic ground effect was measured with movable sting support. For flow visualization, a tufted wire grid was mounted on the movable sting behind the model. Tests results showed that the lift and drag increments in dynamic ground effect were always lower than the static values. Effect of the trailing-edge flap deflections on lift increments was slight. The fuselage reduced the lift increments at a given ground height. From flow visualization under static conditions, the vortex core was seen to enlarge as the ground approached.

Lee, Pai Hung↗
NASA NTRS1973

Dynamic pressure transducer system for pulsed plasma flow diagnosis.

The response characteristics of high sensitivity piezoelectric pressure transducers suitable for use in the plasma flow induced by megawatt-level electric discharges in low density (less than 1 Torr) gases are described. The uniquely designed probe records the initial impingement of a large magnitude total pressure pulse, followed by the flow of primary interest with order-of-magnitude smaller signals. Effects relating to probe and support accelerations, blast shielding and probe heating are evaluated and accounted for in a probe system with a sensitivity of 40 V/atm.

York, T. M.↗
NASA NTRS1975

Results of a 0.03- scale aerodynamic characteristics investigation of Boeing 747 carrier (model no. AX 1319 I-1) mated with a space shuttle orbiter (model 45-0) conducted in the Boeing transonic wind tunnel (CA5), volume 1

The performance, stability, and control characteristics of various carrier aircraft configurations are presented. Aerodynamic characteristics of the carrier mated with the Orbiter, carrier alone, and Orbiter alone were investigated. Carrier support system tare and interference effects were determined. Six-component force and moment data were recorded for the carrier and Orbiter. Buffet onset characteristics of the carrier vertical tail and horizontal tail were recorded. Angles of attack from -3 deg through 26 deg and angles of slideslip between +12 deg and -12 deg were investigated at Mach numbers from 0.15 through 0.70. Photographs are included.

Sarver, D.↗
NASA NTRS1974

A comparison of leaf epinasty induced by weightlessness or by clinostat rotation

A space flight experiment to determine the effect of weightlessness on the liminal angle of leaves of pepper as compared to the angles of leaves of central plants that rotate horizontally on an earth-based clinostat is evaluated. Copies of the Biosatellite II pepper plant flight film and of the clinostat central film were obtained, and an objective analysis of the information on these films is presented. Results confirm that epinastic leaf movements are characteristic in both orbital and clinostated pepper plants. Claims that the rotation on the clinostat produce the same effect as weightlessness are not supported by the pepper plant experiment.

Brown, A. H.↗
NASA NTRS1976

Application of NASTRAN to large deflection supersonic flutter of panels

Flat panel flutter at high supersonic Mach number is analyzed using NASTRAN Level 16.0 by means of modifications to the code. Two-dimensional plate theory and quasi-steady aerodynamic theory are employed. The finite element formulation and solution procedure are presented. Modifications to the NASTRAN code are discussed. Convergence characteristics of the iteration processes are also briefly discussed. Effects of aerodynamic damping, boundary support condition and applied in-plane loading are included. Comparison of nonlinear vibration and linear flutter results with analytical solutions demonstrate that excellent accuracy is obtained with NASTRAN.

Mei, C.↗
NASA NTRS1979

Cinemicrographic specimen housing

Housing used to observe gravitation effects on specimens embedded in support media, such as agar, supports microbial specimens vertically for time-lapsed cinemicrographic studies. Procedure cannot be performed with conventional microscopes which see specimens in horizontal plane only.

Wilkins, J. R.↗
NASA NTRS1980

Software development environments: Present and future, appendix D

Computerized environments which facilitate the development of appropriately functioning software systems are discussed. Their current status is reviewed and several trends exhibited by their history are identified. A number of principles, some at (slight) variance with the historical trends, are suggested and it is argued that observance of these principles is critical to achieving truly effective and efficient software development support environments.

Riddle, W. E.↗
NASA NTRS1979

A cracked beam or plate transversely loaded by a stamp

In this paper the problem of an infinite elastic beam or a plate containing a crack is considered. The medium is loaded transversely through a stamp which may be rigid or elastic. The problem is a coupled crack-contact problem which cannot be solved by treating the crack and contact problems separately and by using a superposition technique. First the Green's functions for the general case are obtained. Then the integral equations for a cracked infinite strip loaded by a frictionless stamp are obtained. With the question of fracture in mind, the primary interest in the paper has been in calculating the stress intensity factors. The results are given for a rigid flat stamp with sharp edges and for an elastic curved stamp. The effect of friction at the supports on the stress intensity factors is also studied and a numerical example is given.

Nied, H. F.↗
NASA NTRS1981

In-situ cross linking of polyvinyl alcohol

A method of producing a crosslinked polyvinyl alcohol structure, such as a battery separator membrane or electrode envelope is described. An aqueous solution of a film-forming polyvinyl alcohol is admixed with an aldehyde crosslinking agent a basic pH to inhibit crosslinking. The crosslinking agent, perferably a dialdehyde such as glutaraldehyde, is used in an amount of from about 1/2 to about 20% of the theoretical amount required to crosslink all of the hydroxyl groups of the polymer. The aqueous admixture is formed into a desired physical shape, such as by casting a sheet of the solution. The sheet is then dried to form a self-supporting film. Crosslinking is then effected by immersing the film in aqueous acid solution. The resultant product has excellent properties for use as a battery separator.

Philipp, W. H.↗
NASA NTRS1982

Application of control theory to dynamic systems simulation

The application of control theory is applied to dynamic systems simulation. Theory and methodology applicable to controlled ecological life support systems are considered. Spatial effects on system stability, design of control systems with uncertain parameters, and an interactive computing language (PARASOL-II) designed for dynamic system simulation, report quality graphics, data acquisition, and simple real time control are discussed.

Auslander, D. M.↗