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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Aeroheating and Aerodynamic CFD Validation And Prediction for The X-38 Program

This paper presents the results of a computational fluid dynamics validation exercise using the General Aerodynamic Simulation Program (GASP) code for vehicles under consideration for the X-38 program. The scope of the exercise involved simulation and comparison with wind tunnel aeroheating and aerodynamic data in the hypersonic regime. In addition, simulations were performed and results are presented for the full-scale flight vehicle along an expected re- entry trajectory.

Loomis, Mark P.↗
DOE OSTI2026

Tailoring Crosslinks through Time─A Paradigm for Tough Hydrogels

The multidisciplinary applications of hydrogels have motivated a thorough exploration of the relationship between their structural and mechanical properties, i.e., spatial structure–function relationships, with particular regard to strength and toughness. While this approach has driven fundamental advancements in the design of robust hydrogel structures, further complementary perspectives are needed to enable holistic, rational design schemes that integrate considerations such as fabrication and advanced functions like response and adaptation. To these ends, this review focuses on the dynamics of temporal-function relationships and their fundamental bases in order to highlight how the dynamic regulation of polymer interactions programs: 1) polymer assembly and material structure; 2) response to deformation and fracture behavior; 3) dynamic modulation of properties and structural remodeling/self-healing. Here, by exploring this intersection of hydrogel formation, function, and remodeling, this review seeks to shed light on the fundamental relationship between molecular structure, material assembly, and performance in order to connect the emerging area of bioinspired materials processing with tough hydrogel design, and further provides a lasting inspiration and impetus for future hydrogel development that enables valuable scientific and technological advancements.

36 MATERIALS SCIENCE↗
NASA NTRS1974

SEASAT economic assessment

The SEASAT program will provide scientific and economic benefits from global remote sensing of the ocean's dynamic and physical characteristics. The program as presently envisioned consists of: (1) SEASAT A; (2) SEASAT B; and (3) Operational SEASAT. This economic assessment was to identify, rationalize, quantify and validate the economic benefits evolving from SEASAT. These benefits will arise from improvements in the operating efficiency of systems that interface with the ocean. SEASAT data will be combined with data from other ocean and atmospheric sampling systems and then processed through analytical models of the interaction between oceans and atmosphere to yield accurate global measurements and global long range forecasts of ocean conditions and weather.

Hicks, K.↗
NASA NTRS1975

Effect of damping on excitability of high-order normal modes

The effect of localized structural damping on the excitability of higher-order large space telescope spacecraft modes is investigated. A preprocessor computer program is developed to incorporate Voigt structural joint damping models in a finite-element dynamic model. A postprocessor computer program is developed to select critical modes for low-frequency attitude control problems and for higher-frequency fine-stabilization problems. The selection is accomplished by ranking the flexible modes based on coefficients for rate gyro, position gyro, and optical sensor, and on image-plane motions due to sinusoidal or random PSD force and torque inputs.

Merchant, D. H.↗
NASA NTRS1977

Air-cushion landing systems

Computer program based on heave/pitch analysis simulates dynamic behavior during landing impact and taxi over irregular runway. Program can be adapted to run on any computer with FORTRAN compiler.

Captain, K. M.↗
NASA NTRS1992

Liquid propulsion turbomachinery model testing

For the past few years an extensive experimental program to understand the fluid dynamics of the Space Shuttle Main Engine hot gas manifold has been in progress. This program includes models of the Phase II and II+ manifolds for each of the air and water flow facilities, as well as two different turbine flow paths and two simulated power levels for each manifold. All models are full-scale (geometric). The water models are constructed partially of acrylic to allow flow visualization. The intent of this paper is to discuss the concept, including the test objectives, facilities, and models, and to summarize the data for an example configuration, including static pressure data, flow visualization, and the solution of a specific flow problem.

Mcdaniels, David M.↗
NASA NTRS1974

Collaborative research in cardiovascular dynamics and bone elasticity

A collaborative research program covering a variety of topics of biomechanics and biomedical engineering within the fields of cardiovascular dynamics, respiration, bone elasticity and vestibular physiology is described. The goals of the research were to promote: (1) a better understanding of the mechanical behavior of the circulatory system and its control mechanisms; (2) development of noninvasive methods of measuring the changes in the mechanical properties of blood vessels and other cardiovascular parameters in man; (3) application of these noninvasive methods to examine in man the physiological effects of environmental changes, including earth-simulated gravitational changes; and (4) development of in-flight methods for studying the events which lead to post-flight postural hypotension.

Source record↗
NASA NTRS1984

Aircraft penetrations of arc cloud lines

Results of a NOAA/NASA research field program (1982-1983) which focused on dynamic and thermodynamic characterization of arc cloud lines are discussed. The program combines research aircraft flights with rapid-scan (3-minute interval) GOES imagery and covers the subcloud layer above and below the density surge line. Strong differences in the dynamic characteristics of air are noted to exist within and above the density surge line (DSL); air motions within the DSL are much more turbulent, with stronger upward and downward motions, than in the subcloud layer above the DSL. The arc cloud lines and the associated DSL regions are concluded to pose an extreme potential hazard to aircraft and Space Shuttle operations.

Sinclair, P. C.↗
NASA NTRS1978

Space Shuttle Plume Simulation Effect on Aerodynamics

Technology for simulating plumes in wind tunnel tests was not adequate to provide the required confidence in test data where plume induced aerodynamic effects might be significant. A broad research program was undertaken to correct the deficiency. Four tasks within the program are reported. Three of these tasks involve conducting experiments, related to three different aspects of the plume simulation problem: (1) base pressures; (2) lateral jet pressures; and (3) plume parameters. The fourth task involves collecting all of the base pressure test data generated during the program. Base pressures were measured on a classic cone ogive cylinder body as affected by the coaxial, high temperature exhaust plumes of a variety of solid propellant rockets. Valid data were obtained at supersonic freestream conditions but not at transonic. Pressure data related to lateral (separation) jets at M infinity = 4.5, for multiple clustered nozzles canted to the freestream and operating at high dynamic pressure ratios. All program goals were met although the model hardware was found to be large relative to the wind tunnel size so that operation was limited for some nozzle configurations.

Hair, L. M.↗
NASA NTRS1979

Analytical investigation of the landing dynamics of a large airplane with a load-control system in the main landing gear

The results of an evaluation of an active load-control landing gear computer program (ACOLAG) for predicting the landing dynamics of airplanes with passive and active main gears are presented. ACOLAG was used in an analytical investigation of the landing dynamics of a large airplane with both passive and active main gears. It was concluded that the program is valid for predicting the landing dynamics of airplanes with both passive and active main gears. It was shown that the active gear reduces airframe-gear forces and airplane motions following initial impact, and has the potential for significant reductions in structural fatigue damage relative to that which occurs with the passive gear.

Mcgehee, J. R.↗
NASA NTRS1991

A Dynamic Testing Complexity Metric

This paper introduces a dynamic metric that is based on the estimated ability of a program to withstand the effects of injected "semantic mutants" during execution by computing the same function as if the semantic mutants had not been injected. Semantic mutants include: (1) syntactic mutants injected into an executing program and (2) randomly selected values injected into an executing program's internal states. The metric is a function of a program, the method used for injecting these two types of mutants, and the program's input distribution; this metric is found through dynamic executions of the program. A program's ability to withstand the effects of injected semantic mutants by computing the same function when executed is then used as a tool for predicting the difficulty that will be incurred during random testing to reveal the existence of faults, i.e., the metric suggests the likelihood that a program will expose the existence of faults during random testing assuming faults were to exist. If the metric is applied to a module rather than to a program, the metric can be used to guide the allocation of testing resources among a program's modules. In this manner the metric acts as a white-box testing tool for determining where to concentrate testing resources. Index Terms: Revealing ability, random testing, input distribution, program, fault, failure.

Voas, Jeffrey↗
DOE OSTI2026

Adaptive nonlinear wavefront shaping in layered TMDs

Two-dimensional transition metal dichalcogenides are promising candidates for nonlinear photonics applications, offering strong nonlinear susceptibility and compatibility with integrated platforms. Although considerable effort has been devoted to manipulating second harmonic generation in these materials, the dynamic control of nonlinear wavefronts remains largely unexplored. Metasurfaces have enabled significant progress in nonlinear beam engineering, yet their practical implementation is limited by low conversion efficiencies and restricted design flexibility. In this work, we employ feedback-based wavefront shaping using spatial light modulators to enhance SHG from pyramid-like WS 2 multilayer structures by over three orders of magnitude in selected spatial regions. This approach allows us to program nonlinear holograms and dynamically shape the SHG signal through phase-only modulation, opening new possibilities for nonlinear imaging, optical information processing, and data communication.

Mavian, Alex [Rensselaer Polytechnic Inst., Troy, ↗
NASA NTRS1986

COFS 3: Multibody dynamics and control technology

COFS 3 is the third project within the Control of Flexible Structures (COFS) program. It deals with developing multibody dynamics and control technology for large space structures. It differs from COFS 1 and 2 in two respects. First, it addresses a more complex class of structure, and second it is basically a scale model ground test and analysis program while COFS 1 and 2 feature Shuttle flight experiments. The specific technology thrusts within COFS 3 are model sensitivities, test methods, analysis validation, systems identification, and vibration suppression. The COFS 3 project will develop the methods for using dynamically scaled models and analysis to predict the structural dynamics of large space structures. The project uses the space station as a focus because it is typical of the structures of interest and provides the first opportunity to obtain full-scale on-orbit dynamics data.

Letchworth, Robert↗
NASA NTRS1991

Analyzing Control/Structure Interactions

CO-ST-IN computer program developed to facilitate study of control/structure interactions; dynamic coupling between control systems and flexible structures. Works in conjunction with other programs to enhance analysis of vibrations. Designed to complement and enhance rather than replace software tools for analysis of control systems and dynamics of structures. FORTRAN 77 program.

Carney, K.↗
NASA NTRS1974

Dynamic properties of aircraft tires

A research program has investigated the use of the von Schlippe string-type tire model for predicting the dynamic behavior of aircraft tires. The transfer-function method was used for theory evaluation. A more flexible two-constant modification to the string theory tire model is presented. Experiments were conducted on four types of scale model aircraft tires. Two types were of conventional bias construction, one type was an isotropic toroid, and one type was of unbelted radial construction. The conventional string theory and model gave predictions that were in good agreement with experimental data for bias constructed tires. The two-constant modification to string theory provided better agreement between predictions and experiment for the unconventional tires. The results indicate that the string theory tire model using static and slow-rolling tire properties predicts dynamic aircraft tire properties that have the same trends as the measured dynamic properties and, in most cases, provides good quantitative agreement.

Clark, S. K.↗
NASA NTRS1992

NACA 0012 benchmark model experimental flutter results with unsteady pressure distributions

The Structural Dynamics Division at NASA Langley Research Center has started a wind tunnel activity referred to as the Benchmark Models Program. The primary objective of the program is to acquire measured dynamic instability and corresponding pressure data that will be useful for developing and evaluating aeroelastic type CFD codes currently in use or under development. The program is a multi-year activity that will involve testing of several different models to investigate various aeroelastic phenomena. This paper describes results obtained from a second wind tunnel test of the first model in the Benchmark Models Program. This first model consisted of a rigid semispan wing having a rectangular planform and a NACA 0012 airfoil shape which was mounted on a flexible two degree-of-freedom mount system. Experimental flutter boundaries and corresponding unsteady pressure distribution data acquired over two model chords located at the 60 and 95 percent span stations are presented.

Rivera, Jose A., Jr.↗
NASA NTRS1975

The effects of localized damping on structural response

The effect of localized structural damping on the excitability of higher order normal modes of the large space telescope was investigated. A preprocessor computer program was developed to incorporate Voigt structural joint damping models in a NASTRAN finite-element dynamic model. A postprocessor computer program was developed to select critical modes for low-frequency attitude control problems and for higher frequency fine-stabilization problems. The mode selection is accomplished by ranking the flexible modes based on coefficients for rate gyro, position gyro, and optical sensors, and on image-plane motions due to sinusoidal or random power spectral density force and torque inputs.

Merchant, D. H.↗
NASA NTRS1989

Experimental and computational studies of dynamic stall

A review of dynamic stall research in progress under the Navy-NASA Joint Institute of Aeronautics is presented. This effort, which includes both experimental and computational studies of the dynamic stall process, is directed toward better understanding and modeling of the fluid flow that occurs on helicopters and aircraft flying in conditions that induce dynamic stall. The results of research now in progress are presented, with discussion of the experimental program on compressibility effects on dynamic stall, related CFD studies of the stall process based on Navier-Stokes modeling, and viscous-inviscid flow modeling of the incipient stall process.

Carr, L. W.↗