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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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NASA NTRS1990

Environmental space hazards - An overview

An overview of space hazards that exist in the geo-lunar environment is given along with specific examples of deleterious effects that can be visited upon a long-term mission-oriented spacecraft system in LEO, GEO, the intervening space, LLO, and the lunar surface. Hazards discussed are categorized as pervasive (radiation), incident specific (meteoroids, monatomic oxygen, thermal gradient and shock, and low earth orbital debris), and chemically corrosive (monatomic oxygen). It is pointed out that, while some of the difficulties encountered are common to all types of propulsion systems, in the interplanetary domain the emphasis shifts from incident specific hazards to the pervasive upsets caused by ionizing and nonionizing radiation.

Bahr, G. K.↗

NASA NTRS1990

Notes on initial disturbance fields for the transition problem

Initial disturbance fields are categorized and discussed with respect to modes of disturbance and the variants which occur for each test technique. Attention is focused on four fluctuation modes included under the category of stream turbulence: vorticity fluctuations, entropy disturbances or temperature spottiness, noise, and concentration fluctuations. The mechanisms by which particulate matter can affect transition are discussed, along with electrostatic discharges with frequencies in the range from 200 KHz to 30 MHz which is within the critical disturbance-frequency range for many high-speed flows. Acoustic radiation from own vehicle, roughness, and Brownian motion are also covered.

Bushnell, Dennis↗

NASA NTRS1990

Thermal Infrared Imaging Spectrometer - An advanced optics technology instrument

Through the use of a special optical filter, the Thermal Infrared Imaging Spectrometer, an airborne multispectral IR imaging instrument operating in the thermal emission region (7.5-14 microns), will achieve signal-to-noise ratios greater than 600 with ambient temperature optics. This instrument will be used to do compositional surface mapping of the terrain, and will refine the ability to categorize rock families and types by providing much higher spectral resolution in the emission region than was previously available. Details of the optical system, the detector, the cooler system, and the support electronics are described.

Mahoney, Colin↗

NASA NTRS1991

Unified formulation of dynamics for serial rigid multibody systems

There has been a growing interest in the development of new and efficient algorithms for multibody dynamics in recent years. Serial rigid multibody systems form the basic subcomponents of general multibody systems, and a variety of algorithms to solve the serial chain forward dynamics problem have been proposed. In this paper, the economy of representation and analysis tools provided by the spatial operator algebra are used to clarify the inherent structure of these algorithms, to identify those that are similar, and to study the relationships among the ones that are distinct. For the purposes of this study, the algorithms are categorized into three classes: algorithms that require the explicit computation of the mass matrix, algorithms that are completely recursive in nature, and algorithms of intermediate complexity. In addition, alternative factorizations for the mass matrix and closed form expressions for its inverse are derived. These results provide a unifying perspective, within which these diverse dynamics algorithms arise naturally as a consequence of a progressive exploitation of the structure of the mass matrix.

Jain, Abhinandan↗

NASA NTRS1991

An engineering assessment of gas/surface interactions in free-molecular aerodynamics

Data available on the gas/surface interaction (GSI) phenomenon, particularly in the rarefied to near-free-molecular flow regime are collected, categorized, and analyzed with a purpose of developing a GSI model that could be used as a guide to spacecraft designers. The study shows that there are not enough useful data for building a high-confidence GSI model. However, sufficient results are obtained to suggest that continued reliance on the diffuse GSI model is inappropriate, particularly in the near-free-molecular regime.

Knox, E. C.↗

NASA NTRS1991

Nuclear Thermal Propulsion Technology - Summary of FY 1991 Interagency Panel Planning

An Interagency (NASA/DOE/DOD) technical panel has been working in 1991 to evaluate nuclear thermal propulsion (NTP) concepts on a consistent basis, and to continue technology development project planning for a joint project in nuclear propulsion for Space Exploration Initiative (SEI). This paper summarizes the efforts of the panel to date and summarizes the technology plans defined for NTP. Concepts were categorized based on probable technology readiness data, and innovative 'proof-of-concept' tests and analyses were defined. While further studies will be required to provide a consistent comparison of all of the NTP concepts, the current status of the studies is presented.

Clark, John S.↗

NASA NTRS1991

The business case for connectivity

Information systems that provide competitive advantages to organizations can be broadly classified into those that improve the effectiveness of a business function and those that improve the reach of information in the organization. The latter, organizational connectivity systems, can be categorized as intraorganizational and interorganizational systems. Intraorganization systems provide connectivity to function areas within the business, while interorganizational systems support the exchange of business data between independent business units. These system are not confined to a single entity but span organizational boundaries which can be national or international in scope. A series of case studies was undertaken in an effort to better understand the issues and problems associated with providing an increased flow of information within and outside of an organization. Ten issues emerged from this study. In summary, it is necessary for firms to first consider how effective their internal communications systems are before launching projects that tie the organization to external systems.

Adams, Dennis↗

NASA NTRS1991

Analysis of objects in binary images

Digital image processing techniques are typically used to produce improved digital images through the application of successive enhancement techniques to a given image or to generate quantitative data about the objects within that image. In support of and to assist researchers in a wide range of disciplines, e.g., interferometry, heavy rain effects on aerodynamics, and structure recognition research, it is often desirable to count objects in an image and compute their geometric properties. Therefore, an image analysis application package, focusing on a subset of image analysis techniques used for object recognition in binary images, was developed. This report describes the techniques and algorithms utilized in three main phases of the application and are categorized as: image segmentation, object recognition, and quantitative analysis. Appendices provide supplemental formulas for the algorithms employed as well as examples and results from the various image segmentation techniques and the object recognition algorithm implemented.

Leonard, Desiree M.↗

NASA NTRS1991

Technology development on evolutionary space station

The topics covered are presented in view graph form and include a space research and technology (R&T) mission statement and a NASA action plan. With respect to an integrated technology plan for the civil space program, the following topics are also covered: (1) an R&T strategy; (2) a NASA technology maturation strategy; (3) an Office of Space Flight (OSF) technology requirements evaluation; (4) an external technology perspectives summary; (5) a work breakdown structure; (6) critical user requirements/ strategic plan element categorization; (7) technology flight experiments; (8) proposed station paylods by thrust; and (9) an integrated traffic model

Ambrus, Judith H.↗

NASA NTRS1991

A novel approach in formulation of special transition elements: Mesh interface elements

The objective of this research program is in the development of more accurate and efficient methods for solution of singular problems encountered in various branches of mechanics. The research program can be categorized under three levels. The first two levels involve the formulation of a new class of elements called 'mesh interface elements' (MIE) to connect meshes of traditional elements either in three dimensions or in three and two dimensions. The finite element formulations are based on boolean sum and blending operators. MEI are being formulated and tested in this research to account for the steep gradients encountered in aircraft and space structure applications. At present, the heat transfer and structural analysis problems are being formulated from uncoupled theory point of view. The status report: (1) summarizes formulation for heat transfer and structural analysis; (2) explains formulation of MEI; (3) examines computational efficiency; and (4) shows verification examples.

Sarigul, Nesrin↗

NASA NTRS1992

Investigation of possible causes for human-performance degradation during microgravity flight

The results of the first year of a three year study of the effects of microgravity on human performance are given. Test results show support for the hypothesis that the effects of microgravity can be studied indirectly on Earth by measuring performance in an altered gravitational field. The hypothesis was that an altered gravitational field could disrupt performance on previously automated behaviors if gravity was a critical part of the stimulus complex controlling those behaviors. In addition, it was proposed that performance on secondary cognitive tasks would also degrade, especially if the subject was provided feedback about degradation on the previously automated task. In the initial experimental test of these hypotheses, there was little statistical support. However, when subjects were categorized as high or low in automated behavior, results for the former group supported the hypotheses. The predicted interaction between body orientation and level of workload in their joint effect on performance in the secondary cognitive task was significant for the group high in automatized behavior and receiving feedback, but no such interventions were found for the group high in automatized behavior but not receiving feedback, or the group low in automatized behavior.

Schroeder, James E.↗

NASA NTRS1992

Neural network classification of questionable EGRET events

High energy gamma rays (greater than 20 MeV) pair producing in the spark chamber of the Energetic Gamma Ray Telescope Experiment (EGRET) give rise to a characteristic but highly variable 3-D locus of spark sites, which must be processed to decide whether the event is to be included in the database. A significant fraction (about 15 percent or 10(exp 4) events/day) of the candidate events cannot be categorized (accept/reject) by an automated rule-based procedure; they are therefore tagged, and must be examined and classified manually by a team of expert analysts. We describe a feedforward, back-propagation neural network approach to the classification of the questionable events. The algorithm computes a set of coefficients using representative exemplars drawn from the preclassified set of questionable events. These coefficients map a given input event into a decision vector that, ideally, describes the correct disposition of the event. The net's accuracy is then tested using a different subset of preclassified events. Preliminary results demonstrate the net's ability to correctly classify a large proportion of the events for some categories of questionables. Current work includes the use of much larger training sets to improve the accuracy of the net.

Meetre, C. A.↗

NASA NTRS1989

Low thrust propulsion literature survey

A literature search was performed to investigate the area of low thrust propulsion. In an effort to evaluate this technology, a number of articles, obtained through the use of the NASA-RECON database, were collected and categorized. The study indicates that although much was done, particularly in the 1960's and 1970's, more can be done in the area of practical navigation and guidance. It is suggested that the older studies be reinvestigated to see what potential there exists for future low thrust applications.

Monroe, Darrel↗

NASA NTRS1992

Achieving spectrum conservation for the minimum-span and minimum-order frequency assignment problems

Effective and efficient solutions of frequency assignment problems assumes increasing importance as the radiofrequency spectrum experiences ever increasing utilization by diverse communications services, requiring that the most efficient use of this resource be achieved. The research presented explores a general approach to the frequency assignment problem, in which such problems are categorized by the appropriate spectrum conserving objective function, and are each treated as an N-job, M-machine scheduling problem appropriate for the objective. Results obtained and presented illustrate that such an approach presents an effective means of achieving spectrum conserving frequency assignments for communications systems in a variety of environments.

Heyward, Ann O.↗

NASA NTRS1992

Stiffness and strength tailoring in uniform space-filling truss structures

A deterministic procedure for tailoring the continuum stiffness and strength of uniform space-filling truss structures, through the appropriate selection of truss geometry and member sizes (flexural stiffness, axial stiffness, and length), is presented. The trusses considered herein are generated by uniform replication of a characteristic truss cell. The repeating cells are categorized by one of a set of possible geometric symmetry groups derived using crystallographic techniques. The elastic symmetry associated with each geometric symmetry group is identified to help select an appropriate truss geometry for a given application. Stiffness and strength tailoring of a given truss geometry is enabled through explicit expressions relating the continuum stiffnesses and failure stresses of the truss to the stiffnesses and failure loads of its members. These expressions are derived using an existing equivalent continuum analysis technique and a newly developed analytical failure theory for trusses. Several examples are presented to illustrate the application of these techniques and to demonstrate the usefulness of the information gained from this analysis.

Lake, Mark S.↗

NASA NTRS1992

Space Science Laboratory publications and presentations, 1 January - 31 December 1991

Listed here are significant publications and presentations of the Space Science Laboratory during the period January 1 to December 31, 1991. Entries are categorized according to NASA Reports (arranged by report number), Open Literature, and Presentations (arranged alphabetically by title). Also included is an appendix listing preprints issued by the laboratory during this reporting period.

Moorehead, Tauna W.↗

NASA NTRS1991

Geostationary Operational Environmental Satellite (GOES-N report). Volume 1: Technical

The GOES-N study consisted of five distinct tasks including: determining replication costs of GOES I-M and GOES-7 in the GOES-N time frame; defining and evaluating modifications to GOES I-M to improve efficiency or reduce costs; and defining evolutionary changes to the GOES I-M design to satisfy National Weather Service (NWS) 1983 and NOAA 1989 requirements. The categorization and disposition of NOAA requirements is reported in volume 1 section 4. Results of the GOES I-M efficiency/cost improvement modifications study are described in Section 7.1. The system concept options 1, 2, and 3 that generally represent the results of the Task 2, 3A, and 3B studies are summarized in Section 7.2. Another result of the GOES-N study, the determination of which NWS 1983 and NOAA 1989 requirements can be met with the three options, is contained in volume 1 section 7. Conclusions and recommendations are covered in volume 1 section 8. Imager, sounder, control system, space environment monitor, search and rescue, weather facsimile, data collection system, and products/process/communications recommendations were extracted from sections 9, 10, and 11. Section 8 also contains conclusions pertaining to programmatic operational satellite issues (prerequisite development strategies, the direct procurement of instruments by the government, protoflight mission, etc.). Sections 9, 10, and 11 address instrument, control system, image/navigation/registration, and other system design considerations and surveys. These sections are supported by the appendices in volume 2.

Source record↗

NASA NTRS1991

Space transportation systems, launch systems, and propulsion for the Space Exploration Initiative: Results from Project Outreach

A number of transportation and propulsion options for Mars exploration missions are analyzed. As part of Project Outreach, RAND received and evaluated 350 submissions in the launch vehicle, space transportation, and propulsion areas. After screening submissions, aggregating those that proposed identical or nearly identical concepts, and eliminating from further consideration those that violated known physical princples, we had reduced the total number of viable submissions to 213. In order to avoid comparing such disparate things as launch vehicles and electric propulsion systems, six broad technical areas were selected to categorize the submissions: space transportation systems; earth-to-orbit (ETO) launch systems; chemical propulsion; nuclear propulsion; low-thrust propulsion; and other. To provide an appropriate background for analyzing the submissions, an extensive survey was made of the various technologies relevant to the six broad areas listed above. We discuss these technologies with the intent of providing the reader with an indication of the current state of the art, as well as the advances that might be expected within the next 10 to 20 years.

Garber, T.↗