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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Evaluation of analytical procedures for prediction of turbulent boundary layers on a porous wall

An analytical study has been made to determine how well current boundary layer prediction techniques work when there is mass transfer normal to the wall. The data that were considered in this investigation were for two-dimensional, incompressible, turbulent boundary layers with suction and blowing. Some of the bleed data were taken in an adverse pressure gradient. An integral prediction method was used three different porous wall skin friction relations, in addition to a solid-surface relation for the suction cases. A numerical prediction method was also used. Comparisons were made between theoretical and experimental skin friction coefficients, displacement and momentum thicknesses, and velocity profiles. The integral method with one of the porous wall skin friction laws gave very good agreement with data for most of the cases considered. The use of the solid-surface skin friction law caused the integral to overpredict the effectiveness of the bleed. The numerical techniques also worked well for most of the cases.

Towne, C. E.↗
NASA NTRS1976

Electromagnetic instabilities driven by unequal proton beams in the solar wind

The paper sets forth a numerical investigation of the linear dispersion relation for typical solar wind conditions at 1 AU during those times (high-speed streams) when a secondary beam of protons drifting relative to the main proton component is present. Three beam-driven instabilities were found to occur as the beam drift velocity approaches the Alfven speed: (1) a pure, field-aligned magnetosonic wave that is most important at relatively high beta and/or high beam drift speeds; (2) an oblique magnetosonic wave having highest growth rates 15-30 deg from the magnetic field; and (3) an oblique Alfven wave having maximum growth rates at increasing angle to the magnetic field. The linear growth rates for the field-aligned magnetosonic and the Alfven oblique modes are investigated as a function of relative beam density, varying anisotropic pitch angle distributions for the various components, electron temperature, and electron heat flux.

Montgomery, M. D.↗
NASA NTRS1976

Engineering flowfields and heating rates for highly swept wing leading edges

An engineering flow model is developed (and verified experimentally) which describes the flowfield that arises when a supersonic stream encounters a wedge/cylinder configuration whose angles are such that the flow includes only weak shock waves. A numerical code using the perfect gas relations is used to describe the flow in the plane of symmetry inboard of the shock interaction region. Theoretical surface-pressure and heat-transfer distributions are computed for freestream velocities ranging from 1167 to 7610 m/sec. Nondimensionalization of the heat-transfer rates in terms of local flow parameters produced a correlation of Stanton number as a function of the local Reynolds number, which is independent of the freestream flow conditions and of the surface temperature.

Bertin, J. J.↗
NASA NTRS1978

Optimization and evaluation of main liquid rocket propulsion systems for advanced earth-to-orbit shuttles

A computerized preliminary design system is used to evaluate potential main liquid-rocket propulsion systems for advanced technology winged single-stage-to-orbit launch vehicles. Evaluated are trade-offs between ascent flight trajectory performance and flight vehicle sizing driven by engine mass and propellant requirements. Numerous mission, flight, and vehicle-related requirements and constraints are satisfied in the design process. With the design system, five dual-mode propulsion system concepts are compared to a baseline hydrogen and oxygen system in terms of the changes in vehicle dry mass and gross mass.

Wilhite, A. W.↗
NASA NTRS1980

Development and implementation of Shuttle/IUS proximity operations flight design software

The High Fidelity Relative Motion Program (HFRMP), a trajectory/attitude numerical integration program, was developed and implemented on the MPAD HP-9825A desk top computer systems. A solar and a lunar ephemeris is included in the HFRMP along with models of the oblate Earth, a rotating atmosphere, the orbiter's OMS/RCS/DAP system, orbiter vents, rotor dynamics, and upper stage propulsion systems. Although designed primarily for the analysis of proximity operations, it is useful in other areas such as attitude/stability analysis, propulsive consumables estimation, and trajector perturbation studies. An unique identification was assigned to each of the various configurations of the HFRMP that were developed to test new techniques and algorithms are briefly described. These include the HFRMP Versions 03H, 03M, 03T, 03U, and 05D. Development of orbiter/upper stage separation techniques including flight design support for the TDRS-A and Galileo deployment flights and design of standard maneuver sequences is discussed. Also, the development and implementation of the Euler angle conversion program is briefly addressed.

Wilson, S. W.↗
NASA NTRS1981

Simulation of Heavy Lift Airship dynamics over large ranges of incidence and speed

A nonlinear, multibody, six-degrees-of-freedom digital simulation has been developed to study generic Heavy Lift Airship (HLA) dynamics and control. The basic aerodynamic functions developed to model the hull, tail, and rotor loads continuously over all incidence ranges are reviewed and applied to a Quadrotor HLA with a low fineness ratio hull and a small vee-tail. Trim calculations for a test vehicle suggest control power deficiencies in crosswind stationkeeping for the unloaded vehicle. Gust responses show the importance of correctly calculating loads due to accelerated relative motion of air and hull. Numerically linearized dynamics for the test vehicle show the existence of a divergent yaw mode, and an oscillatory pitch mode whose stability characteristics are sensitive to flight speed. A considerable improvement in the vehicle's stability and response results from a simple multi-axis closed-loop control system operating on the rotors and propeller blades.

Tischler, M. B.↗
NASA NTRS1982

Advanced rocket propulsion technology assessment for future space transportation

Single-stage and two-stage launch vehicles were evaluated for various levels of propulsion technology and payloads. The evaluation included tradeoffs between ascent flight performance and vehicle sizing that were driven by engine mass, specific impulse, and propellant requirements. Numerous mission, flight, and vehicle-related requirements and constraints were satisfied in the design process. The results showed that advanced technology had a large effect on reducing both single- and two-stage vehicle size. High-pressure hydrocarbon-fueled engines that were burned in parallel with two-position nozzle hydrogen-fueled engines reduced dry mass by 23% for the two-stage vehicle and 28% for the single-stage vehicle as compared to an all-hydrogen-fueled system. The dual-expander engine reduced single-stage vehicle dry mass by 41%. Using advanced technology, the single-stage vehicle became comparable in size and sensitivity to that of the two-stage vehicle for small payloads.

Wilhite, A. W.↗
NASA NTRS1985

Prediction of the flow-field interference induced by the long-range laser velocimeter in the Ames 40- by 80-foot and the 80- by 120-foot wind tunnels

The predicted flow disturbances induced in the test sections of the Ames 40- by 80-Foot Wind Tunnels by the presence of the Long-Range Laser Velocimeter (LRLV) are presented. The predictions were made using a potential-flow paneling code to model the test section and the LRLV, and a calculation of the resulting flow field was made. The flow velocity and angularity were calculated at numerous locations in the flow field relative to the LRLV, and the results are presented.

Reinath, M. S.↗
NASA NTRS1986

First- and second-order sensitivity analysis of linear and nonlinear structures

This paper employs the principle of virtual work to derive sensitivity derivatives of structural response with respect to stiffness parameters using both direct and adjoint approaches. The computations required are based on additional load conditions characterized by imposed initial strains, body forces, or surface tractions. As such, they are equally applicable to numerical or analytical solution techniques. The relative efficiency of various approaches for calculating first and second derivatives is assessed. It is shown that for the evaluation of second derivatives the most efficient approach is one that makes use of both the first-order sensitivities and adjoint vectors. Two example problems are used for demonstrating the various approaches.

Haftka, R. T.↗
NASA NTRS1987

Two-component LDV investigation of 3-dimensional shock/turbulent boundary layer interactions

Mean-velocity and turbulence measurements obtained by two-component laser Doppler velocimetry are presented, together with numerical predictions, for the shock-related separation of a turbulent boundary layer at Mach 2.85. The basic geometry, a 30 deg half-angle flare mounted on a long cylinder, is made three-dimensional by tipping the flare at an angle of attack, alpha. The separation length and general upstream influence increase with alpha. A recirculating vortex in the separated zone becomes stronger as three-dimensionality increases. A large-scale unsteadiness of the separation shock wave and surrounding flowfields grows in amplitude with alpha, and appears to strongly influence the amplification of turbulence correlations ahead of detachment. Scaling of the streamwise coordinate by separation length causes two-dimensional and three-dimensional data profiles on the cylinder to collapse for most measured quantities.

Brown, J. D.↗
NASA NTRS1987

On the thermal instability of galactic and cluster halos

The paper presents a detailed study of thermal instabilities in cooling flows associated with galaxies and clusters of galaxies. In the case of purely radiation-driven accretion onto a central object such as the cD galaxy M87, it is found that the gas is largely subject to overstability, rather than to monotonic instability. If thermal conductivity is taken into account, the flow is stabilized on scales of several kiloparsecs, even if the conductivity is appreciably reduced (e.g., about 1 percent) with respect to the Spitzer value. In no case are the globular perturbations (i.e., perturbations with comparable radial and azimuthal dimensions) found to be monotonically unstable. The paper presents numerical solutions of the local dispersion relation for the cooling flow in M87 and discusses the possible consequences of the results for a correct understanding of cooling flows.

Malagoli, A.↗
NASA NTRS1987

Space station proximity operations windows: Human factors design guidelines

Proximity operations refers to all activities outside the Space Station which take place within a 1-km radius. Since there will be a large number of different operations involving manned and unmanned vehicles, single- and multiperson crews, automated and manually controlled flight, a wide variety of cargo, and construction/repair activities, accurate and continuous human monitoring of these operations from a specially designed control station on Space Station will be required. Total situational awareness will be required. This paper presents numerous human factors design guidelines and related background information for control windows which will support proximity operations. Separate sections deal with natural and artificial illumination geometry; all basic rendezvous vector approaches; window field-of-view requirements; window size; shape and placement criteria; window optical characteristics as they relate to human perception; maintenance and protection issues; and a comprehensive review of windows installed on U.S. and U.S.S.R. manned vehicles.

Haines, Richard F.↗
NASA NTRS1988

Nature and the nonlinear evolution of electrostatic waves associated with the AMPTE solar wind releases

The nonlinear evolution of the electrostatic waves observed during the AMPTE (Active Magnetosphere Particle Tracer Explorers) solar wind releases is investigated. Previous linear studies indicate two distinct sets of instabilities may be responsible for the generation. One set consists of ion-acoustic type instabilities which are insensitive to the presence of a background magnetic field, while the other group corresponds to the modified two stream instabilities and requires the solar wind flow to be across the ambient magnetic field. To establish which set of instabilities is more viable a detailed linear Vlasov theory has been conducted by numerically solving the full electromagnetic dispersion relation. In addition both the plasma wave as well as the magnetic field measurements by the IRM (Ion Release Module) spacecraft were used to correlate the frequency and the power of the observed waves with the magnitude and the direction of the solar wind magnetic field. The results of these analyses indicate that the ion-acoustic type instabilities have growth rates that are an order of magnitude or more larger than those of the modified two stream instabilities. Results show that both the solar wind protons and the released ions may be heated and accelerated in the directions oblique to the solar wind flow velocity.

Omidi, N.↗
NASA NTRS1989

Animation graphic interface for the space shuttle onboard computer

Graphics interfaces designed to operate on space qualified hardware challenge software designers to display complex information under processing power and physical size constraints. Under contract to Johnson Space Center, MICROEXPERT Systems is currently constructing an intelligent interface for the LASER DOCKING SENSOR (LDS) flight experiment. Part of this interface is a graphic animation display for Rendezvous and Proximity Operations. The displays have been designed in consultation with Shuttle astronauts. The displays show multiple views of a satellite relative to the shuttle, coupled with numeric attitude information. The graphics are generated using position data received by the Shuttle Payload and General Support Computer (PGSC) from the Laser Docking Sensor. Some of the design considerations include crew member preferences in graphic data representation, single versus multiple window displays, mission tailoring of graphic displays, realistic 3D images versus generic icon representations of real objects, the physical relationship of the observers to the graphic display, how numeric or textual information should interface with graphic data, in what frame of reference objects should be portrayed, recognizing conditions of display information-overload, and screen format and placement consistency.

Wike, Jeffrey↗
NASA NTRS1990

Formulation and evaluation of an analytical model for composite box-beams

A direct method for determining the effective elastic stiffnesses and deformation behavior of composite box-beam (BB) structures is developed analytically, validated, and demonstrated. The BB walls are modeled as orthotropic-ply laminated plates, so that the elastic properties vary both through the thickness and around the BB contour; deformation is described in terms of extension, bending, twisting, shearing, and torsion-related out-of-plane warping. Numerical results for several BB configurations are presented in tables and graphs and compared with experimental data and FEM computations (Stemple and Lee, 1989): good general agreement is obtained for cross-ply, antisymmetric, and symmetric layups, except for symmetric layups with ply orientation angles theta greater than 30 deg. Both out-of-plane warping and transverse shear coupling are found to have significant effects on BB elastic response.

Smith, Edward C.↗
NASA NTRS1990

High speed turbulent reacting flows: DNS and LES

Work on understanding the mechanisms of mixing and reaction in high speed turbulent reacting flows was continued. Efforts, in particular, were concentrated on taking advantage of modern computational methods to simulate high speed turbulent flows. In doing so, two methodologies were used: large eddy simulations (LES) and direct numerical simulations (DNS). In the work related with LES the objective is to study the behavior of the probability density functions (pdfs) of scalar properties within the subgrid in reacting turbulent flows. The data base obtained by DNS for a detailed study of the pdf characteristics within the subgrid was used. Simulations are performed for flows under various initializations to include the effects of compressibility on mixing and chemical reactions. In the work related with DNS, a two-dimensional temporally developing high speed mixing layer under the influence of a second-order non-equilibrium chemical reaction of the type A + B yields products + heat was considered. Simulations were performed with different magnitudes of the convective Mach numbers and with different chemical kinetic parameters for the purpose of examining the isolated effects of the compressibility and the heat released by the chemical reactions on the structure of the layer. A full compressible code was developed and utilized, so that the coupling between mixing and chemical reactions is captured in a realistic manner.

Givi, Peyman↗
NASA NTRS1991

Feedback instability of the ionospheric resonant cavity

A model is developed that provides a theoretical basis for previous numerical results showing a feedback instability with frequencies characteristic of Alfven travel times within the region of the large increase of Alfven speed above the ionosphere. These results have been extended to arbitrary ionospheric conductivity by developing a numerical solution of the cavity dispersion relation that involves Bessel functions of complex order and argument. It is concluded that the large contrast between the magnetospheric and ionospheric Alfven speed leads to the formation of resonant cavity modes with frequencies ranging from 0.1 to 1 Hz. The presence of the cavity leads to a modification of the reflection characteristics of Alfven waves with frequencies that compare to the cavity's normal modes.

Lysak, Robert L.↗
NASA NTRS1991

ISEE 1 observations of electrostatic ion cyclotron waves in association with ion beams on auroral field lines from about 2.5 to 4.5 R(E)

Quasi-monochromatic waves at about the hydrogen cyclotron frequency were observed as the ISEE 1 satellite traversed auroral field lines at radial distances of about 2.5-4.5 R(E) near midnight on June 19, 1981. Waves and both lower and higher frequencies were observed at higher altitudes, and possible electrostatic helium cyclotron and oxygen cyclotron waves occurred at lower altitudes. Upflowing hydrogen and oxygen beams and field-aligned currents occurred simultaneously. The features of the waves are most consistent with the current-driven mode. In addition, numerical studies of the linear dispersion relation, using parameters based on the observations, show that both the parallel and oblique two-stream modes and the ion-beam-driven modes were stable while oblique current-driven modes were unstable. The O(+) and H(+) distributions provide evidence for interactions with local electrostatic ion cyclotron waves and for the H(+)-O(+) two-stream instability at altitudes below the satellite.

Catell, C. A.↗