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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Analytical study of the cruise performance of a class of remotely piloted, microwave-powered, high-altitude airplane platforms

Each cycle of the flight profile consists of climb while the vehicle is tracked and powered by a microwave beam, followed by gliding flight back to a minimum altitude. Parameter variations were used to define the effects of changes in the characteristics of the airplane aerodynamics, the power transmission systems, the propulsion system, and winds. Results show that wind effects limit the reduction of wing loading and increase the lift coefficient, two effective ways to obtain longer range and endurance for each flight cycle. Calculated climb performance showed strong sensitivity to some power and propulsion parameters. A simplified method of computing gliding endurance was developed.

Morris, C. E. K., Jr.↗
NASA NTRS1981

Parametric study of microwave-powered high-altitude airplane platforms designed for linear flight

The performance of a class of remotely piloted, microwave powered, high altitude airplane platforms is studied. The first part of each cycle of the flight profile consists of climb while the vehicle is tracked and powered by a microwave beam; this is followed by gliding flight back to a minimum altitude above a microwave station and initiation of another cycle. Parametric variations were used to define the effects of changes in the characteristics of the airplane aerodynamics, the energy transmission systems, the propulsion system, and winds. Results show that wind effects limit the reduction of wing loading and the increase of lift coefficient, two effective ways to obtain longer range and endurance for each flight cycle. Calculated climb performance showed strong sensitivity to some power and propulsion parameters. A simplified method of computing gliding endurance was developed.

Morris, C. E. K., Jr.↗
NASA NTRS2001

Planning and Scheduling for Fleets of Earth Observing Satellites

We address the problem of scheduling observations for a collection of earth observing satellites. This scheduling task is a difficult optimization problem, potentially involving many satellites, hundreds of requests, constraints on when and how to service each request, and resources such as instruments, recording devices, transmitters, and ground stations. High-fidelity models are required to ensure the validity of schedules; at the same time, the size and complexity of the problem makes it unlikely that systematic optimization search methods will be able to solve them in a reasonable time. This paper presents a constraint-based approach to solving the Earth Observing Satellites (EOS) scheduling problem, and proposes a stochastic heuristic search method for solving it.

Frank, Jeremy↗
NASA NTRS1995

Augmented Shock Wave Severance of Materials

This paper describes a new approach for severing or weakening a variety of materials. The technique employs embedding explosive cords into parallel grooves that are cut into a surface of a material. The cords are initiated simultaneously to produce shock waves that progress toward the centerline between the cords and the lower surface of the material. Intersecting incident and reflected waves augment at the centerline to fail or weaken the material in tension. No harmful debris is produced on the opposite side of the material from the explosive cords. The primary focus of the effort described in this paper was to fracture the F-16 aircraft trilaminate canopy. Also, complete severance was achieved in 2024-T4 aluminum plate stock. Possible applications are through canopy egress and crew module severance from military aircraft and separation of rocket vehicle stages and payloads. This approach offers important advantages over explosive methods currently in use.

Bement, Laurence J.↗
NASA NTRS1993

The 'Baldwin Effect' in Wolf-Rayet stars

The equivalent widths of a number of emission lines in the spectra of WN-type Wolf-Rayet stars are found to inversely correlate with the luminosity of the underlying continuum. This is the well-known Baldwin Effect that has previously been observed in quasars and some Seyfert I galaxies. The Effect can be inferred from line and continuum predictions in published non-LTE model helium atmospheres and is explainable in terms of differences in wind density among WN stars. Using a simple wind model, we show that the Effect arises from the fact that both the effective radius for the local continuum and the emission measure of the layers above the continuum-forming region depend on the density in the wind. The Effect provides a new method for distance determinations of W-R stars.

Morris, Patrick↗
NASA NTRS2005

Mixed-Initiative Activity Planning for Mars Rovers

One of the ground tools used to operate the Mars Exploration Rovers is a mixed-initiative planning system called MAPGEN. The role of the system is to assist operators building daily plans for each of the rovers, maximizing science return, while maintaining rover safety and abiding by science and engineering constraints. In this paper, we describe the MAPGEN system, focusing on the mixed-initiative planning aspect. We note important challenges, both in terms of human interaction and in terms of automated reasoning requirements. We then describe the approaches taken in MAPGEN, focusing on the novel methods developed by our team.

Bresina, John↗
NASA NTRS1964

Monte Carlo techniques for solving transport problems

The Monte Carlo procedure is a model sampling technique. A model is established, and the behavior of sample units in this model is followed. A sufficient number of sample units are followed to obtain a statistical average or macroscopic quantities, which are the quantities of interest. This technique was used in crude form by Fermi in connection with the building of the first atomic pile. Later, Von Neumann and Ulam developed and used the Monte Carlo procedure extensively in developing the atomic bomb. Since then this technique has gained considerable use in nuclear reactor problems (refs. 1 and 2), and we at the Lewis Research Center have been extending it to thermal radiation (refs. 3 and 4), rarefied gas flows, and plasma flow problems (ref. 5). This technique, which requires a large number of sample histories to obtain solutions with small variances, is receiving greater use because of the development of the high-speed electronic computers.

SAMPLED DATA SYSTEM↗
NASA NTRS1983

An Empirical Bayes Approach to Spatial Analysis

Multi-channel LANDSAT data are collected in several passes over agricultural areas during the growing season. How empirical Bayes modeling can be used to develop crop identification and discrimination techniques that account for spatial correlation in such data is considered. The approach models the unobservable parameters and the data separately, hoping to take advantage of the fact that the bulk of spatial correlation lies in the parameter process. The problem is then framed in terms of estimating posterior probabilities of crop types for each spatial area. Some empirical Bayes spatial estimation methods are used to estimate the logits of these probabilities.

Morris, C. N.↗
NASA NTRSDate not supplied

Validation Testing and Statistical Analysis of the Rotary Tumbler Fabric Abrasion Method

The Artemis space suit glove environmental protection garment (EPG) will be the first line of protection used to shield the crewmember’s hands from the environments encountered during extravehicular activity (EVA). As the Artemis missions will include more extreme environments than those experienced on the International Space Station, development, verification, and validation of gloves requires the development of new test methods. A previous paper focused on the development of a test procedure to characterize lunar EVA glove fabrics using ASTM standardized test methods and the design and validation of a new standardized test procedure for comparing abrasion resistance between fabrics using a dust and rock filled rotary tumbler. Preliminary results of testing were presented in that paper. This paper reports on the validation testing and statistical analysis of the newly developed tumbler abrasion test method.

Robert J Jones↗
NASA NTRSDate not supplied

Wire-break Ignition Testing of Materials for Spacesuit Fire Hazard Control

The input design constraints applied to the extravehicular activity (EVA) spacesuit pose a significant challenge for mitigation of fire hazards. To minimize fatigue and increase comfort of the crewmember operating the suit, the suit pressure is lowered below sea level conditions with typical EVA suit designs operating with 4.3 psia (29.7 kPa). With the lowered operating pressures and the use of closed-loop life support, the suit requires elevated concentrations of oxygen, typically >95%. At these oxygen concentrations, nearly the entirety of the suit internal materials are flammable. This leaves one remaining possible control leg of the fire triangle: ignition sources. Since the Gemini and Apollo programs, this has been a risk that has undergone constant reassessment, with a focus on improved mitigation. After the Apollo I fire, an arc ignition method was developed and used to quantify ignition thresholds for in-suit materials resulting in a current limit for powered in-suit devices applied to all subsequent suit designs. After the discovery of a frayed spacesuit biomed cable on STS-113 during the Shuttle Program, the previous arcing method was repeated with additional methods developed to extend the testing further. One of those methods was wire-break ignition testing, in which the current in a single strand of wire was progressively increased, preheating the material in proximity with a resultant break and the application of a reasonably repeatable arc to ignite the material, all while exposed in the selected environment. This method was used to test a suite of spacesuit materials providing relative performance with respect to ignition with this configuration for application of energy. This paper discusses extension of the current data set to address recent material additions, lowering of energy test levels for quantification of materials too low to measure in previous testing, as well as future plans to improve this method.

Colin Campbell↗
NASA NTRS1990

Thermal stress analysis of the NASA Dryden hypersonic wing test structure

Present interest in hypersonic vehicles has resulted in a renewed interest in thermal stress analysis of airframe structures. While there are numerous texts and papers on thermal stress analysis, practical examples and experience on light gage aircraft structures are fairly limited. A research program has been undertaken at General Dynamics to demonstrate the present state of the art, verify methods of analysis, gain experience in their use, and develop engineering judgement in thermal stress analysis. The approach for this project has been to conduct a series of analyses of this sample problem and compare analysis results with test data. This comparison will give an idea of how to use our present methods of thermal stress analysis, and how accurate we can expect them to be.

Morris, Glenn↗