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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 1,279 records · Page 71

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NASA NTRS1982

Radiation effects in IRAS extrinsic infrared detectors

During the calibration and testing of the Infrared Astronomy Satellite (IRAS) focal plane, it was observed that the extrinsic photoconductor detectors were affected by gamma radiation at dose levels of the order of one rad. Since the flight environment will subject the focal plane to dose levels of this order from protons in single pass through the South Atlantic Anomaly, an extensive program of radiation tests was carried out to measure the radiation effects and to devise a method to counteract these effects. The effects observed after irradiation are increased responsivity, noise, and rate of spiking of the detectors after gamma-ray doses of less than 0.1 rad. The detectors can be returned almost to pre-irradiation performance by increasing the detector bias to breakdown and allowing a large current to flow for several minutes. No adverse effects on the detectors have been observed from this bias boost, and this technique will be used for IRAS with frequent calibration to ensure the accuracy of observations made with the instrument.

Varnell, L.↗

NASA NTRS1982

Implication of a color multibeam communications satellite in the 30/20 GHz bands

In order to meet the need for increased communications capacity, NASA is conducting a program to develop technology and systems for a 30/20 GHz multibeam domestic U.S. satellite. One way to provide the required national interconnectivity is to permute and time share connections among the involved areas by means of a satellite-borne multiport microwave switch with a Time-Division Multiple Access (TDMA) system. In this connection, the question was analyzed whether a practical satellite message routing system can be developed using FDMA techniques. The total traffic (model A) was derived and used as an input specification for the satellite-routed FDMA study. Attention is given to beam isolations, color and regional systems, the level of service, and the color FDMA satellite. It is concluded that the FDMA system considered can handle substantially all the Customer Premises Service (CPS) and Trunking (TR) traffic in Model A. The (color) scheme completely satisfies the CPS and TR requirements of 23 cities.

Hoffman, M.↗

NASA NTRS1986

International Ultraviolet Explorer (IUE) observation of Halley's Comet

The main objectives of the IUE Halley's Comet program are: study of the physical and chemical properties of a comet clearly different from those observed previously with IUE; study of the long-term evolution of the gas and dust coma and the ion and dust tails, by combining IUE data with UV and in-situ observations obtained by other spacecraft; and assessment of the gas and dust environment of Halley in terms of its possible impact on the trajectories of the flyby spacecraft. Another program investigates the CS scale length, and the rotational profile of CS in order to test and calibrate dynamic-flow models of comets. These observations will begin in August 1985 when the heliocentric distance of the comet is 2.8 AU and its total visual magnitude + 13. They will continue into the ninth IUE observing period, through mid-1986.

Kondo, Y.↗

NASA NTRS1986

Auroral morphology of the midday oval

Auroral displays in the noon sector were examined by using hundreds of Defense Meteorological Satellite Program auroral images, taken over the southern polar region in austral winters, in order to determine the morphology. The auroral displays in the midday part of the auroral oval can be grouped into five characteristic types, depending on the geomagnetic activity and the Bz component of the interplanetary magnetic field. An important characteristic is the clear disconnection in appearance between the noonside and the nightside discrete auroras. Also, there is the lack of correlation between the concurrent nightside substorm activity and midday discrete auroral activity. Thus, the occurrence of bright, discrete auroras in the midday oval may be caused by the local injection of the magnetosheath plasma into the dayside boundary layer. The observed discontinuity of discrete auroras between the dayside and the nightside ovals is consistent with the existence of two separated major injection regions along the auroral oval: the dayside cusp and the nightside plasma sheet.

Meng, C.-I.↗

NASA NTRS1986

The extinction law in the open cluster NGC 457 and the intrinsic energy distribution of Phi Cassiopeiae (F0 Ia)

Five early B-type stars near the main-sequence turnoff in NGC 457 have been observed at low dispersion with the short-wavelength prime and the long-wavelength redundant cameras of the IUE satellite. The equivalent widths of spectral features that are particularly strong and sensitive to temperature and luminosity were computed in the cluster stars and in 20 lightly reddened stars of types O9-B3 and luminosity classes III-V. The comparison of the equivalent widths provides a reliable method for finding matching pairs. Having identified the best comparison star for each program star, binned fluxes were used to determine the mean extinction curve. In order to cover the visible region, monochromatic fluxes of Phi Cas were derived from observations with the intensified Reticon scanner mounted on the No. 2 0.9 m telescope of KPNO, and they were dereddened with the mean extinction curve of Savage and Mathis. Thus, the intrinsic energy distribution of Phi Cas were determined from 1500 to 5800 A for use in a detailed model-atmosphere analysis.

Rosenzweig, P.↗

NASA NTRS1986

Using a laser aureole to invert lidar return

An aureole generated by a laser beam was studied. The strength of the signal redirected towards a sensor high above the surface by a combination of one scattering event in the marine boundary layer (mbl) and one single reflection event from the ocean surface was estimated. A model of mbl aerosol size distributions was used to estimate Mie scattering for a wide range of meteorolocial conditions. The sea surface reflection was determined from a Gaussian model of the wave slopes. These laser aureoles which were estimated over the wide range of conditions and were normalized by the reflected laser light were found to be highly correlated with the optical depth of the boundary layer. By estimating optical depth from the aureole, the Bernoulli-Riccati inversion of lidar return could be constrained and the inversion accuracy improved. A Monte Carlo program was developed to study the laser aureole generated by up to 8 orders of reflection and scattering. The aureole was generated by a narrow, 10 nsec laser pulse at 1.06 microns and measured by a receiver 10 km above the ocean surface. The original theoretical computation compared well with the Monte Carlo method. When multiple scattereffects were included, the normalized aureole was still highly correlated with the mbl optical depth over the range of conditions.

Hooper, W. P.↗

NASA NTRS1985

A Study of the Utilization of Advanced Composites in Fuselage Structures of Commercial Aircraft

A study was conducted to define the technology and data needed to support the introduction of advanced composites in the future production of fuselage structure in large transport aircraft. Fuselage structures of six candidate airplanes were evaluated for the baseline component. The MD-100 was selected on the basis of its representation of 1990s fuselage structure, an available data base, its impact on the schedule and cost of the development program, and its availability and suitability for flight service evaluation. Acceptance criteria were defined, technology issues were identified, and a composite fuselage technology development plan, including full-scale tests, was identified. The plan was based on composite materials to be available in the mid to late 1980s. Program resources required to develop composite fuselage technology are estimated at a rough order of magnitude to be 877 man-years exclusive of the bird strike and impact dynamic test components. A conceptual composite fuselage was designed, retaining the basic MD-100 structural arrangement for doors, windows, wing, wheel wells, cockpit enclosure, major bulkheads, etc., resulting in a 32 percent weight savings.

Watts, D. J.↗

NASA NTRS1988

Coupled bending-torsion steady-state response of pretwisted, nonuniform rotating beams using a transfer-matrix method

Using the Newtonian method, the equations of motion are developed for the coupled bending-torsion steady-state response of beams rotating at constant angular velocity in a fixed plane. The resulting equations are valid to first order strain-displacement relationships for a long beam with all other nonlinear terms retained. In addition, the equations are valid for beams with the mass centroidal axis offset (eccentric) from the elastic axis, nonuniform mass and section properties, and variable twist. The solution of these coupled, nonlinear, nonhomogeneous, differential equations is obtained by modifying a Hunter linear second-order transfer-matrix solution procedure to solve the nonlinear differential equations and programming the solution for a desk-top personal computer. The modified transfer-matrix method was verified by comparing the solution for a rotating beam with a geometric, nonlinear, finite-element computer code solution; and for a simple rotating beam problem, the modified method demonstrated a significant advantage over the finite-element solution in accuracy, ease of solution, and actual computer processing time required to effect a solution.

Gray, Carl E., Jr.↗

NASA NTRS1987

A natural language query system for Hubble Space Telescope proposal selection

The proposal selection process for the Hubble Space Telescope is assisted by a robust and easy to use query program (TACOS). The system parses an English subset language sentence regardless of the order of the keyword phases, allowing the user a greater flexibility than a standard command query language. Capabilities for macro and procedure definition are also integrated. The system was designed for flexibility in both use and maintenance. In addition, TACOS can be applied to any knowledge domain that can be expressed in terms of a single reaction. The system was implemented mostly in Common LISP. The TACOS design is described in detail, with particular attention given to the implementation methods of sentence processing.

Hornick, Thomas↗

NASA NTRS1990

Evaluating the effect of accuracy ratios on the percent of calibrations which are out of tolerance

The standard practice in calibration laboratories across the country, including the Measurement Standards and Calibration Laboratory (MSCL) at the Johnson Space Center, is to use accuracy ratios to determine if instruments are in-tolerance rather than computing the actual uncertainty associated with the instruments. In the past, the accepted practice was to use an accuracy ratio of 10:1, but then state of the art advanced to the point where the 10:1 ratio could no longer be maintained, and the ratio was arbitrarily lowered to 4:1. It is now becoming increasingly difficult to maintain the 4:1 accuracy ratio, and in some cases 1:1 is the best that can be achieved. However, the effect of using these small accuracy ratios on the number of mistakes made in classifying instruments as in or out of tolerance is completely unknown. In order to assess the effect of using accuracy ratios in calibration, a simulation program was written to compute the proportion of instruments determined to be out of tolerance which were actually in, denoted by alpha, and the proportion of instruments determined to be in-tolerance which were actually out, denoted by beta. This was done for accuracy ratios of 1:1 and 10:1, for one to five progressive calibrations, under varying standard and instrument conditions. Selected results are presented and explained.

Navard, Sharon E.↗

NASA NTRS1990

A new program in earth system science education

A program aimed at accelerating the development of earth system science curricula at the undergraduate level and at seeding the establishment of university-based mechanisms for cooperative research and education among universities and NASA has been initiated by the Universities Space Research Association (USRA) in conjunction with NASA. Proposals were submitted by 100 U.S. research universities which were selected as candidates to participate in a three-year pilot program to develop undergraduate curricula in earth system science. Universities were then selected based upon peer review and considerations of overall scientific balance among proposed programs. The program will also aim to integrate a number of universities with evolving earth system programs, linking them with a cooperative curriculum, shared faculty, and NASA scientists in order to establish a stronger base for earth systems related education and interdisciplinary research collaboration.

Huntress, Wesley↗

NASA NTRS1992

Digital data acquisition and preliminary instrumentation study for the F-16 laminar flow control vehicle

Preliminary studies have shown that maintenance of laminar flow through active boundary-layer control is viable. Current research activity at NASA Langley and NASA Dryden is utilizing the F-16XL-1 research vehicle fitted with a laminar-flow suction glove that is connected to a vacuum manifold in order to create and control laminar flow at supersonic flight speeds. This experimental program has been designed to establish the feasibility of obtaining laminar flow at supersonic speeds with highly swept wing and to provide data for computational fluid dynamics (CFD) code calibration. Flight experiments conducted as supersonic speeds have indicated that it is possible to achieve laminar flow under controlled suction at flight Mach numbers greater than 1. Currently this glove is fitted with a series of pressure belts and flush mounted hot film sensors for the purpose of determining the pressure distributions and the extent of laminar flow region past the stagnation point. The present mode of data acquisition relies on out-dated on board multi-channel FM analogue tape recorder system. At the end of each flight, the analogue data is digitized through a long laborious process and then analyzed. It is proposed to replace this outdated system with an on board state-of-the-art digital data acquisition system capable of a through put rate of up to 1 MegaHertz. The purpose of this study was three-fold: (1) to develop a simple algorithm for acquiring data via 2 analogue-to-digital convertor boards simultaneously (total of 32 channels); (2) to interface hot-film/wire anemometry instrumentation with a PCAT type computer; and (3) to characterize the frequency response of a flush mounted film sensor. A brief description of each of the above tasks along with recommendations are given.

Ostowari, Cyrus↗

NASA NTRS1994

Program For Joule-Thomson Analysis Of Mixed Cryogens

JTMIX computer program predicts ideal and realistic properties of mixed gases at temperatures between 65 and 80 K. Performs Joule-Thomson analysis of any gaseous mixture of neon, nitrogen, various hydrocarbons, argon, oxygen, carbon monoxide, carbon dioxide, and hydrogen sulfide. When used in conjunction with DDMIX computer program of National Institute of Standards and Technology (NIST), JTMIX accurately predicts order-of-magnitude increases in Joule-Thomson cooling capacities occuring when various hydrocarbons added to nitrogen. Also predicts boiling temperature of nitrogen depressed from normal value to as low as 60 K upon addition of neon. Written in Turbo C.

Jones, Jack A.↗

NASA NTRS1989

Addressing the problem of interruptability in the construction of large space structures

Large scale space missions of the near future will depend upon successful multi-launch coordination and construction in the space environment. One of the main challenges is how to accomplish a valid global analysis of a construction project with the intent of improving safety, reducing overall mission cost, and total construction time. These three items are dependent on the interruptability of the project, which is the ability of the project to recover from unplanned interruptions; such as failure of the launch vehicle; sudden, on-orbit, crew illness; or damage from a space debris impact on the partially completed space structure. A new method for addressing and analyzing this type of problem is being developed. The method is called Program Interruptability and Risk Evaluation Technique, or PIRET. PIRET has been developed in order to model and analyze potential interruptability concerns of the construction of the U.S. Space Station Freedom (SSF), although PIRET is applicable to any complex, multi-launch structural assembly. This paper is a progress report on the continuing research of the NASA Center for Space Construction at the University of Colorado, Boulder into this area of space construction interruptability. The paper will define the problem of interruptability, will diagram the PIRET approach to space construction, will share results from a preliminary PIRET analysis of SSF, and will show that PIRET is a useful tool for modelling space construction interruptability.

Davidson, Roger A.↗

NASA NTRS1985

Requirements for Conformal Coating and Staking of Printed Wiring Boards and Electronic Assemblies

In order to maintain the high standards of the NASA conformal coating and staking program, this publication: prescribes NASA's requirements for assuring reliable conformal coating and staking for printed wiring boards and electronic assemblies; describes and incorporates basic considerations necessary to assure reliable conformal coating and staking; establishes the supplier's responsibility to train and certify personnel; provides for supplier documentation of the fabrication and inspection procedures to be used for NASA work, including supplier innovations and changes in technology; and provides visual workmanship standards to aid those responsible for determining quality conformance to the established requirements.

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NASA NTRS1993

The Advanced Technology Operations System: ATOS

Mission control systems supporting new space missions face ever-increasing requirements in terms of functionality, performance, reliability and efficiency. Modern data processing technology is providing the means to meet these requirements in new systems under development. During the past few years the European Space Operations Centre (ESOC) of the European Space Agency (ESA) has carried out a number of projects to demonstrate the feasibility of using advanced software technology, in particular, knowledge based systems, to support mission operations. A number of advances must be achieved before these techniques can be moved towards operational use in future missions, namely, integration of the applications into a single system framework and generalization of the applications so that they are mission independent. In order to achieve this goal, ESA initiated the Advanced Technology Operations System (ATOS) program, which will develop the infrastructure to support advanced software technology in mission operations, and provide applications modules to initially support: Mission Preparation, Mission Planning, Computer Assisted Operations, and Advanced Training. The first phase of the ATOS program is tasked with the goal of designing and prototyping the necessary system infrastructure to support the rest of the program. The major components of the ATOS architecture is presented. This architecture relies on the concept of a Mission Information Base (MIB) as the repository for all information and knowledge which will be used by the advanced application modules in future mission control systems. The MIB is being designed to exploit the latest in database and knowledge representation technology in an open and distributed system. In conclusion the technological and implementation challenges expected to be encountered, as well as the future plans and time scale of the project, are presented.

Kaufeler, J.-F.↗

NASA NTRS1994

A finite element code for electric motor design

FEMOT is a finite element program for solving the nonlinear magnetostatic problem. This version uses nonlinear, Newton first order elements. The code can be used for electric motor design and analysis. FEMOT can be embedded within an optimization code that will vary nodal coordinates to optimize the motor design. The output from FEMOT can be used to determine motor back EMF, torque, cogging, and magnet saturation. It will run on a PC and will be available to anyone who wants to use it.

Campbell, C. Warren↗

NASA NTRS1994

A parallel strategy for implementing real-time expert systems using CLIPS

As evidenced by current literature, there appears to be a continued interest in the study of real-time expert systems. It is generally recognized that speed of execution is only one consideration when designing an effective real-time expert system. Some other features one must consider are the expert system's ability to perform temporal reasoning, handle interrupts, prioritize data, contend with data uncertainty, and perform context focusing as dictated by the incoming data to the expert system. This paper presents a strategy for implementing a real time expert system on the iPSC/860 hypercube parallel computer using CLIPS. The strategy takes into consideration not only the execution time of the software, but also those features which define a true real-time expert system. The methodology is then demonstrated using a practical implementation of an expert system which performs diagnostics on the Space Shuttle Main Engine (SSME). This particular implementation uses an eight node hypercube to process ten sensor measurements in order to simultaneously diagnose five different failure modes within the SSME. The main program is written in ANSI C and embeds CLIPS to better facilitate and debug the rule based expert system.

Ilyes, Laszlo A.↗