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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Numerical simulation of a turbulent flame stabilized behind a rearward-facing step

Flow of combustible mixtures in a plane channel past a smooth contraction followed by an abrupt expansion, in a typical dump combustor configuration, is modeled by a two-dimensional numerical technique based on the random vortex method. Both the inert and the reacting case are considered. In the latter, the flame is treated as an interface, self-advancing at a prescribed normal burning speed, while the dynamic effects of expansion due to the exothermicity of combustion are expressed by volumetric source lines delineated by its front. Solutions are shown to be in satisfactory agreement with experimental results, especially with respect to global properties such as the average velocity profiles and the reattachment length. The stochastic turbulent velocity components manifest interesting differences, especially near the walls where three-dimensional effects of turbulence are expected to be of importance.

Hsiao, C. C.↗
NASA NTRS1984

Space Station - The next logical step

NASA is committed to the development of a permanently manned Space Station within a decade, in concert with European and Japanese space agencies. In addition to continuing scientific research, the Space Station will proceed with applied science and industrialization experiments. International cooperation opportunities arise within the Space Station program for users (in the definition of missions), for builders (in the development of station resources and capabilities), and operators (in the orbital maintenance of the Space Station).

Finn, T. T.↗
NASA NTRS1985

Space Station - The first step

The United States Space Station program, begun in Fiscal Year 1985 under significant cost constraints, should cause all those involved in the planning of manned interplanetary flight to revise their impressions of the cost and practicality of planetary missions. The presence of the Space Shuttle, as well as arrival of a capable Space Station, will provide a major impetus to planetary programs, both by removing most of the real barriers to extended manned space flights and by proving that significant manned space ventures may be performed very economically.

Mandell, H. C., Jr.↗
NASA NTRS1985

Initiation of the next step - The acquisition of a Space Station Program

Attention is given to NASA's Space Station Program acquisition strategy, as well as the internal implementation of the strategy and the nature of NASA's relations with industry. While the acquisition strategy addresses phased procurement, design-to-cost, and advanced development emphasis, internal implementation concerns itself with 'skunk works' activities and the exploitation of the Technical and Management Information System. NASA's relationship to contractors will stress competition, extensive commercial and international involvement, and design/development phase competition flexibility.

Mancuso, T. G.↗
NASA NTRS1986

On a large time-step high resolution scheme

This paper presents a class of new second-order accurate (2K + 3)-point explicit schemes for the computation of weak solutions of hyperbolic conservation laws, that are total-variation-diminishing under a Courant-Friedrichs-Lewy restriction of K. These highly nonlinear schemes are obtained by applying a nonoscillatory first-order accurate (2K + 1)-point scheme to a modified flux. The derived second-order accurate schemes achieve high resolutions, while retaining the robustness of the original first-order accurate scheme.

Harten, A.↗
NASA NTRS1985

Single step optimization strategies for constrained retargeting maneuvers

The present consideration of recent advancements in the nonlinear guidance of spacecraft, using feedback linearization and decoupling to generate exact nominal commands, gives attention to the correction of saturation effects and oscillation prevention in saturated operating regimes. In the case of spacecraft maneuvered by momentum-transfer devices, real time command generation is possible by means of pointwise minimization of the sum of the squares of the norms of the 'next state error' for the equivalent system and the linear system input. It is also possible to track a nominal trajectory, such as a critically damped harmonic oscillator response, by minimizing the square of the norm of the error between the actual and the tracked states.

Dwyer, T. A. W., III↗
NASA NTRS1985

Single step optimization of feedback-decoupled spacecraft attitude maneuvers

A next-state optimization technique for monitoring spacecraft maneuvers is examined. The optimization technique permits simultaneous trajectory planning and tracking, incorporates actuator saturation and attitude constraints, and prevents overshoot and undershoot. The global linearization of the dynamics and kinematics for a spacecraft driven by reaction wheels is considered. The equations utilized to derive the spacecraft trajectories are presented. The applications of the next-state optimization procedure to a spacecraft maneuvered by momentum transfer devices and the tracking of the nominal trajectory of a critically damped harmonic oscillator response are described.

Dwyer, T. A. W., III↗
NASA NTRS1987

GAS-007: First step in a series of Explorer payloads

As part of the NASA Get Away Special program for flying small, self-contained payloads onboard the Space Shuttle, the Alabama Space and Rocket Center (ASRC) in Huntsville has sponsored three such payloads for its Project Explorer. One of these is GAS-007, which was carried originally on STS mission 41-G in early October 1984. Due to an operational error it was not turned on and was, therefore, subsequently rescheduled and flown on mission 61-C. This paper will review Explorer's history, outline its experiments, present some preliminary experimental results, and describe future ASRC plans for Get Away Special activities, including follow-on Explorers GAS-105 and GAS-608.

Kitchens, Philip H.↗
NASA NTRS1986

Alkaline RFC Space Station prototype - 'Next step Space Station'

The regenerative fuel cell, a candidate technology for the Space Station's energy storage system, is described. An advanced development program was initiated to design, manufacture, and integrate a regenerative fuel cell Space Station prototype (RFC SSP). The RFC SSP incorporates long-life fuel cell technology, increased cell area for the fuel cells, and high voltage cell stacks for both units. The RFC SSP's potential for integration with the Space Station's life support and propulsion systems is discussed.

Hackler, I. M.↗
NASA NTRS1986

Steps towards understanding deep atmospheric heating in flares

Different aspects of the heating of the deep solar atmosphere during flares, including temperature minimum enhancements and white light emission, are discussed. The proper treatment of H(-) radiative losses is discussed, and compared with previous studies, as well as a quantitative analysis of the ionizing effect of nonthermal particles and ultraviolet radiation. It is concluded that temperature minimum heating may be a natural consequence of the global radiation transport in flares. The implications of these results are discussed within the context of homogeneous and inhomogeneous models of the solar atmosphere.

Mauas, Pablo J. D.↗
NASA NTRS1987

Comet rendezvous - The next step

Features of a proposed NASA-West Germany Comet Rendezvous Asteroid Flyby mission (CRAF) are summarized. The spacecraft would carry an imaging system, visual and IR mapping spectrometers, an IR radiometer, an instrumented lander probe, ion mass, neutral-gas, secondary-ion mass, superthermal-ion and retarding potential ion mass spectrometers, etc. The spacecraft would fly alongside the nucleus, hover near it, and circle it. The earliest potential encounter would be with Comet Tempel 2 in October 1996, followed by a flyby of the asteroid 46 Hestia. The science goals of the mission are explored, mainly with reference to unanswered questions remaining after the Halley missions.

Neugebauer, Marcia↗
NASA NTRS1986

Steps toward 8m honeycomb mirrors. VIII - Design and demonstration of a system of thermal control

Directed jets of ambient temperature air are proposed for the maintenance of low internal temperature gradients and conformity with ambient temperatures in honeycomb-structure borosilicate glass telescope mirrors. The use of greater airflow on thicker sections, to match cooling rates, and the cooling or heating of the internal, back, and edge surfaces of the mirror at the same rate established by convection on the front surface, have been tested on a full scale glass thermal model of a single honeycomb cell from an 8-m diameter mirror. The internal thermal gradient (less than 0.1 C) and ambient-temperature-change lag (less than 0.24 C) ensure minimum image degradation.

Cheng, A. Y. S.↗
NASA NTRS1987

Three-dimensional numerical predictions of the flow behind a rearward-facing-step in a supersonic combustor

A CFD code was developed to compute the mixing and combustion of hydrogen fuel in the turbulent flow fields of scramjets. The code is based on the complete Reynold's time-averaged three-dimensional Navier-Stokes equations, and chemical species equations. The code includes a global finite rate hydrogen-air chemical reaction model and the Baldwin-Lomax (1978) turbulence model. The validity of this CFD code was demonstrated by comparing computed results from the code with existing data for three configurations, each containing an important feature of the scramjet combustor flow. The code was then applied to the reacting flow field in a complex combustor model in which hydrogen fuel was injected transversely into a supersonic hot airstream through several fuel injectors.

Uenishi, K.↗
NASA NTRS1988

Antireflection/Passivation Step For Silicon Cell

New process excludes usual silicon oxide passivation. Changes in principal electrical parameters during two kinds of processing suggest antireflection treatment almost as effective as oxide treatment in passivating cells. Does so without disadvantages of SiOx passivation.

Crotty, Gerald T.↗
NASA NTRS1988

Project Explorer takes its second step: GAS-608 in engineering development

An a continuation of its Project Explorer series, the Alabama Space and Rocket Center is sponsoring the development of two additional Get Away Special payloads. Details are given of GAS-608, including descriptions of its six experiments in organic crystal growth, roach eggs, yeast, radish seeds, bacterial morphology, and silicon crystals. A brief summary is also presented of GAS-105 and the Space Camp program for stimulating student first hand participation in space flight studies. GAS-608 will carry six student experiments, which will involve biology, crystal growth, and biochemistry in addition to a centralized package for electronics and power supply.

Kitchens, Philip H.↗
NASA NTRS1988

Predictive wall adjustment strategy for two-dimensional flexible walled adaptive wind tunnel: A detailed description of the first one-step method

Following the realization that a simple iterative strategy for bringing the flexible walls of two-dimensional test sections to streamline contours was too slow for practical use, Judd proposed, developed, and placed into service what was the first Predictive Strategy. The Predictive Strategy reduced by 75 percent or more the number of iterations of wall shapes, and therefore the tunnel run-time overhead attributable to the streamlining process, required to reach satisfactory streamlines. The procedures of the Strategy are embodied in the FORTRAN subroutine WAS (standing for Wall Adjustment Strategy) which is written in general form. The essentials of the test section hardware, followed by the underlying aerodynamic theory which forms the basis of the Strategy, are briefly described. The subroutine is then presented as the Appendix, broken down into segments with descriptions of the numerical operations underway in each, with definitions of variables.

Wolf, Stephen W. D.↗
NASA NTRS1987

The Spaceborne Imaging Radar program: SIR-C - The next step toward EOS

The NASA Shuttle Imaging Radar SIR-C experiments will investigate earth surface and environment phenomena to deepen understanding of terra firma, biosphere, hydrosphere, cryosphere, and atmosphere components of the earth system, capitalizing on the observational capabilities of orbiting multiparameter radar sensors alone or in combination with other sensors. The SIR-C sensor encompasses an antenna array, an exciter, receivers, a data-handling network, and the ground SAR processor. It will be possible to steer the antenna beam electronically, so that the radar look angle can be varied.

Evans, Diane↗