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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

AutoCAD-To-GIFTS Translator Program

AutoCAD-to-GIFTS translator program, ACTOG, developed to facilitate quick generation of small finite-element models using CASA/GIFTS finite-element modeling program. Reads geometric data of drawing from Data Exchange File (DXF) used in AutoCAD and other PC-based drafting programs. Geometric entities recognized by ACTOG include points, lines, arcs, solids, three-dimensional lines, and three-dimensional faces. From this information, ACTOG creates GIFTS SRC file, which then reads into GIFTS preprocessor BULKM or modified and reads into EDITM to create finite-element model. SRC file used as is or edited for any number of uses. Written in Microsoft Quick-Basic (Version 2.0).

Jones, Andrew↗
NASA NTRS1989

AutoCAD-To-NASTRAN Translator Program

Program facilitates creation of finite-element mathematical models from geometric entities. AutoCAD to NASTRAN translator (ACTON) computer program developed to facilitate quick generation of small finite-element mathematical models for use with NASTRAN finite-element modeling program. Reads geometric data of drawing from Data Exchange File (DXF) used in AutoCAD and other PC-based drafting programs. Written in Microsoft Quick-Basic (Version 2.0).

Jones, A.↗
NASA NTRS1989

Translation-vibration-dissociation coupling in nonequilibrium hypersonic flows

A new simple and computationally efficient model was developed, describing the evolution of vibrational states during relaxation and dissociation. The model is based on dividing the nitrogen molecules into two types, those in the vibrational states at a lower level, whose vibrational energy is below a cutoff energy, and those in an upper level, with vibrational energy above the cutoff. Dissociation occurs at the upper level, and recombination returns molecules to the lower level. The model was applied to two flows of engineering interest, the flow through a normal Mach 15 shock wave at 60 km, and a supersonic quasi-one-dimensional flow in a nozzle. Results are compared to those obtained by existing translation-vibration-dissociation coupling models, with results indicating significant differences between the models.

Candler, Graham↗
NASA NTRS1989

Raster Metafile and Raster Metafile Translator

The intent is to present an effort undertaken at NASA Langley Research Center to design a generic raster image format and to develop tools for processing images prepared in this format. Both the Raster Metafile (RM) format and the Raster Metafile Translator (RMT) are addressed. This document is intended to serve a varied audience including: users wishing to display and manipulate raster image data, programmers responsible for either interfacing the RM format with other raster formats or for developing new RMT device drivers, and programmers charged with installing the software on a host platform.

Taylor, Nancy L.↗
NASA NTRS1990

Active control of bearing preload using piezoelectric translators

In many spacecraft applications, mechanisms are required to perform precision pointing operations or to sometimes dither about or track a moving object. These mechanisms perform in a predictable and repeatable manner in benign temperature environments. Severe thermal gradients experienced in actual space applications however, cause assemblies to expand and contract around their bearings. This results in unpredictable changes in bearing preload, and hence bearing friction. This becomes a limitation for servos controlling pointing accuracy. Likewise, uncontrollable vibrations may couple into fixed preload (hence, fixed stiffness) mechanisms and limit pointing accuracy. Consequently, a complex problem faced today is how to design mechanisms that remain insensitive to changing thermal and vibrational spacecraft environments. Research presented involves the simplified modeling and test results of an actuator module that used piezoelectrically preload controlled bearings. The feasibility of actively controlling bearing preload was demonstrated. Because bearing friction is related to preload, a thermally active system designed with aluminum components and a 440 C bearing, was friction tested at temperatures ranging from 0 to 70 C (32 to 158 F). Effectiveness of the translators were demonstrated by mapping a controllable friction range throughout tested temperatures. It was learned that constant preload for this system could be maintained over an approximate 44 C (79 F) temperature span. From testing, it was also discovered that at the more deviate temperatures, expansions were so large that radial clearances were taken up and the duplex bearing became radially preloaded. Thus, active control of bearing preload is feasible but may be limited by inherent geometry constraints and materials used in the system.

Nye, Ted W.↗
NASA NTRS1990

A noncontacting motion monitoring system for an astronaut translation aid

The development of a noncontacting motion sensing system designed to monitor the movement of a cart along a track in the low earth orbit space environment is described. The system uses Hall effect sensors to detect the position of small permanent magnets located along the track. The measurement criteria are described, the system design is discussed, and estimates of the system error are given. The system will be used on the Crew and Equipment Translation Aid (CETA) experiment scheduled for the STS37 flight in November 1990. It will allow the position, velocity, and acceleration of the cart to be determined as it moves along the track.

Finley, Tom D.↗
NASA NTRS1988

Rotational and translational effects in collisions of electronically excited diatomic hydrides

Collisional quenching and vibrational energy proceed competitively with rotational energy transfer for several excited states of the diatomic radicals OH, NH, and CH. This occurs for a wide variety of molecular collision partners. This phenomenon permits the examination of the influence of rotational motion on the collision dynamics of these theoretically tractable species. Measurements can also be made as a function of temperature, i.e., collision velocity. In OH (sup 2 sigma +), both vibrational transfer and quenching are found to decrease with an increase in rotational level, while quenching decreases with increasing temperature. This behavior indicates that for OH, anisotropic attractive forces govern the entrance channel dynamics for these collisions. The quenching of NH (sup 3 pi sub i) by many (although not all) collision partners also decreases with increasing rotational and translational energy, and NH (sup 1 pi) behaves much like OH (sup 2 sigma +). However, the quenching of CH (sup 2 delta) appears to decrease with increasing rotation but increases with increasing temperature, suggesting in this case anisotropic forces involving a barrier or repulsive wall. Such similarities and differences should furnish useful comparisons with both simple and detailed theoretical pictures of the appropriate collision dynamics.

Crosley, David R.↗
NASA NTRS1990

Rotational-translational energy transfer in rarefied nonequilibrium flows

A new model for simulating the transfer of energy between the translational and rotational modes is derived for a homogeneous gas of diatomic molecules. The model has been developed specifically for use in discrete particle simulation methods where molecular motion and intermolecular collisions are treated at the molecular level. A temperature dependence is introduced which has been predicted by theory and observed in experiment. The new model is applied to the relaxation of rotational temperature, and is found to produce significant differences in comparison with the model normally employed at both high and low temperatures. Calculations have also been performed for a Mach 7 normal shock wave.

Boyd, Iain D.↗
NASA NTRS1991

Analysis of vibrational-translational energy transfer using the direct simulation Monte Carlo method

A new model is proposed for energy transfer between the vibrational and translational modes for use in the direct simulation Monte Carlo method (DSMC). The model modifies the Landau-Teller theory for a harmonic oscillator and the rate transition is related to an experimental correlation for the vibrational relaxation time. Assessment of the model is made with respect to three different computations: relaxation in a heat bath, a one-dimensional shock wave, and hypersonic flow over a two-dimensional wedge. These studies verify that the model achieves detailed balance, and excellent agreement with experimental data is obtained in the shock wave calculation. The wedge flow computation reveals that the usual phenomenological method for simulating vibrational nonequilibrium in the DSMC technique predicts much higher vibrational temperatures in the wake region.

Boyd, Iain D.↗
NASA NTRS1992

Three-dimensional simulation of a translating strut inlet

A three-dimensional Navier-Stokes code is used to numerically simulate the flow through a translating strut scramjet inlet. The inlet has variable geometry for efficient operation over a wide speed range. Overall flow-field features such as the corner flow, topwall separation, shockwave coalescence, cowl pressure increase, and flow distortion at the throat are investigated. Comparisons are made with experimental results to provide for the assessment of the present analysis. Effects of boundary-layer ingestion on the overall flow features are also investigated.

Singh, D. J.↗
NASA NTRS1994

Apparatus Translates Crossed-Laser-Beam Probe Volume

Optomechanical apparatus translates probe volume of crossed-beam laser velocimeter or similar instrument while maintaining optical alignment of beams. Measures velocity, pressure, and temperature of flowing gas at several locations. Repeated tedious realignments no longer necessary. Designed to accommodate stimulated-Raman-gain spectrometer for noninvasive measurement of local conditions in flowing gas in supersonic wind tunnel. Applicable to other techniques like coherent anti-Stokes Raman spectroscopy involving use of laser beams crossed at small angles (10 degrees or less).

Herring, Gregory C.↗
NASA NTRS1994

Raster Metafile And Raster Metafile Translator Programs

Raster Metafile (RM) computer program is generic raster-image-format program, and Raster Metafile Translator (RMT) program is assortment of software tools for processing images prepared in this format. Processing includes reading, writing, and displaying RM images. Such other image-manipulation features as minimal compositing operator and resizing option available under RMT command structure. RMT written in FORTRAN 77 and C language.

Randall, Donald P.↗
NASA NTRS1994

Knowledge based translation and problem solving in an intelligent individualized instruction system

An Intelligent Individualized Instruction I(sup 3) system is being built to provide computerized instruction. We present the roles of a translator and a problem solver in an intelligent computer system. The modular design of the system provides for easier development and allows for future expansion and maintenance. CLIPS modules and classes are utilized for the purpose of the modular design and inter module communications. CLIPS facts and rules are used to represent the system components and the knowledge base. CLIPS provides an inferencing mechanism to allow the I(sup 3) system to solve problems presented to it in English.

Jung, Namho↗
NASA NTRS1994

Asymptotic forms for the energy of force-free magnetic field ion figurations of translational symmetry

It is known from computer calculations that if a force-free magnetic field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution and the energy of the field increases progressively. For configurations of translationalsymmetry, it has been found empirically that the energy tends asymptotically to a certain functional form. It is here shown that analysis of a simple model of the asymptotic form of force-free fields of translational symmetry leads to and therefore justifies this functional form. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

Sturrock, P. A.↗
NASA NTRS1998

Thermal Vacuum Testing of the Crew and Equipment Translation Aid for the International Space Station

The Crew and Equipment Translation Aid (CETA) is a human powered cart that will aid astronauts in conducting extra-vehicular activity (EVA) maintenance on the International Space Station (ISS). There are two critical EVA tasks relevant to the successful operation of the CETA. These are the removal of the launch restraint bolts during its initial deployment from the Space Shuttle payload bay and the manual deceleration of the cart, its two onboard astronauts, and a payload. To validate the launch restraint and braking system designs, the hardware engineers needed to verify their performance in an environment similar to that in which it will be used. This environment includes the vacuum of low earth orbit and temperatures as low as -11O F and as high as +200 F. The desire for quantitative data, as opposed to subjective information which could be provided by a suited astronaut, coupled with test scheduling conflicts resulted in an unmanned testing scenario. Accommodating these test objectives in an unmanned test required a solution that would provide remotely actuated thermal vacuum compatible torque sources of up to 25 ft-lbs at four horizontally oriented and four vertically oriented bolts, a variable input force of up to 125 lbs at the four brake actuators, and thermal vacuum compatible torque and force sensors. The test objectives were successfully met in both the thermal Chamber H and the thermal vacuum Chamber B at NASA's Johnson Space Center.

Blanco, Raul A.↗
NASA NTRS1999

Experimental and Computational Investigation of a Translating-Throat Single-Expansion-Ramp Nozzle

An experimental and computational study was conducted on a high-speed, single-expansion-ramp nozzle (SERN) concept designed for efficient off-design performance. The translating-throat SERN concept adjusts the axial location of the throat to provide a variable expansion ratio and allow a more optimum jet exhaust expansion at various flight conditions in an effort to maximize nozzle performance. Three design points (throat locations) were investigated to simulate the operation of this concept at subsonic-transonic, low supersonic, and high supersonic flight conditions. The experimental study was conducted in the jet exit test facility at the Langley Research Center. Internal nozzle performance was obtained at nozzle pressure ratios (NPR's) up to 13 for six nozzles with design nozzle pressure ratios near 9, 42, and 102. Two expansion-ramp surfaces, one concave and one convex, were tested for each design point. Paint-oil flow and focusing schlieren flow visualization techniques were utilized to acquire additional flow data at selected NPR'S. The Navier-Stokes code, PAB3D, was used with a two-equation k-e turbulence model for the computational study. Nozzle performance characteristics were predicted at nozzle pressure ratios of 5, 9, and 13 for the concave ramp, low Mach number nozzle and at 10, 13, and 102 for the concave ramp, high Mach number nozzle.

Deere, Karen A.↗