Search NASA⌕ Search

SEARCH · Search NASA

Results for “Virginia”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

29th JANNAF Combustion Subcommittee Meeting

This volume, the second of five volumes, is a collection of 38 unclassified/unlimited papers which were presented at the 29th Joint Army-Navy-NASA-Air Force (JANNAF) Combustion Subcommittee Meeting, 19-23 October 1992, at NASA Langley Research Center, Hampton, Virginia. Specific subjects discussed include combustion phenomena in air breathing, liquid and solid systems, energetic materials in solids, and combustion instability in solid rocket motors.

Gannaway, Mary T.↗
NASA NTRS1992

Rain rate and modeled fade distributions at 20 GHz and 30 GHz derived from five years of network rain gauge measurements

Five years of rain rate and modeled slant path attenuation distributions at 20 GHz and 30 GHz derived from a network of 10 tipping bucket rain gages was examined. The rain gage network is located within a grid 70 km north-south and 47 km east-west in the Mid-Atlantic coast of the United States in the vicinity of Wallops Island, Virginia. Distributions were derived from the variable integration time data and from one minute averages. It was demonstrated that for realistic fade margins, the variable integration time results are adequate to estimate slant path attenuations at frequencies above 20 GHz using models which require one minute averages. An accurate empirical formula was developed to convert the variable integration time rain rates to one minute averages. Fade distributions at 20 GHz and 30 GHz were derived employing Crane's Global model because it was demonstrated to exhibit excellent accuracy with measured COMSTAR fades at 28.56 GHz.

Goldhirsh, Julius↗
NASA NTRS1992

ACTS propagation terminal update

The activities at Virginia Polytechnic Institute and State University in preparation for the February 1993 launch of ACTS are summarized. ACTS propagation terminals (APT) are being constructed to receive the 20 and 27.5 GHz ACTS beacon signals. Total power radiometers operating at the same frequencies are integrated into the terminal for use in level setting. Recent progress and plans for APT's are reported.

Stutzman, Warren L.↗
NASA NTRS1992

More rain compensation results

To reduce the impact of rain-induced attenuation in the 20/30 GHz band, the attenuation at a specified signal frequency must be estimated and extrapolated forward in time on the basis of a noisy beacon measurement. Several studies have used model based procedures for solving this problem in statistical inference. Perhaps the most widely used model-based paradigm leads to the Kalman filter and its lineal variants. In this formulation, the dynamic features of the attenuation are represented by a state process (x(sub t)). The observation process (y(sub t)) is derived from beacon measurements. Some ideas relating to the signal processing problems related to uplink power control are presented. It is shown that some easily implemented algorithms hold promise for use in estimating rain induced fades. The algorithms were applied to actual data generated at the Virginia Polytechnic Institute and State University (VPI) test facility. Because only one such event was studied, it is not clear that the algorithms will have the same effectiveness when a wide range of events are studied.

Sworder, D. D.↗
NASA NTRS1992

29th JANNAF Combustion Subcommittee Meeting

This volume, the first of five volumes, is a collection of 36 unclassified/unlimited papers which were presented at the 29th Joint Army-Navy-NASA-Air Force (JANNAF) Combustion Subcommittee Meeting, 19-23 October 1992, at NASA Langley Research Center, Hampton, Virginia. Specific subjects discussed include gun propellants, interior ballistics, electrothermal-chemical guns and liquid guns.

Gannaway, Mary T.↗
NASA NTRS1993

Magnetic Suspension Technology Workshop

In order to identify the state of magnetic suspension technology in such areas as rotating systems, pointing of experiments or subsystems, payload isolation, and superconducting materials, a workshop on Magnetic Suspension Technology was held at the Langley Research Center in Hampton, Virginia, on 2-4 Feb. 1988. The workshop included five technical sessions in which a total of 24 papers were presented. The technical sessions covered the areas of pointing, isolation, and measurement, rotating systems, modeling and control, and superconductors. A list of attendees is provided.

Keckler, Claude R.↗
NASA NTRS1993

Magnetic Actuators and Suspension for Space Vibration Control

The research on microgravity vibration isolation performed at the University of Virginia is summarized. This research on microgravity vibration isolation was focused in three areas: (1) the development of new actuators for use in microgravity isolation; (2) the design of controllers for multiple-degree-of-freedom active isolation; and (3) the construction of a single-degree-of-freedom test rig with umbilicals. Described are the design and testing of a large stroke linear actuator; the conceptual design and analysis of a redundant coarse-fine six-degree-of-freedom actuator; an investigation of the control issues of active microgravity isolation; a methodology for the design of multiple-degree-of-freedom isolation control systems using modern control theory; and the design and testing of a single-degree-of-freedom test rig with umbilicals.

Knospe, Carl R.↗
NASA NTRS1993

Evaluation of actuators for the SDOF and MDOF active microgravity isolation systems

The University of Virginia examined the design of actuators for both single-degree-of-freedom (SDOF) and multiple-degree-of-freedom (MDOF) active microgravity isolation systems. For SDOF systems, two actuators were considered: a special large gap magnetic actuator and a large stroke Lorentz actuator. The magnetic actuator was viewed to be of greater difficulty than the Lorentz actuator with little compelling technical advantage and was dropped from consideration. A Lorentz actuator was designed and built for the SDOF test rig using magnetic circuit and finite element analysis. The design and some experimental results are discussed. The University also examined the design of actuators for MDOF isolation systems. This includes design of an integrated 1 cm gap 6-DOF noncontacting magnetic suspension system and of a 'coarse' follower which permits the practical extension of magnetic suspension to large strokes. The proposed 'coarse' actuator was a closed kinematic chain manipulator known as a Stewart Platform. The integration of the two isolation systems together, the isolation tasks assigned to each, and possible control architectures were also explored. The results of this research are examined.

Source record↗
NASA NTRS1992

Differential GPS/inertial navigation approach/landing flight test results

In November of 1990 a joint Honeywell/NASA-Langley differential GPS/inertial flight test was conducted at Wallops Island, Virginia. The test objective was to acquire a system performance database and demonstrate automatic landing using an integrated differential GPS/INS (Global Positioning System/inertial navigation system) with barometric and radar altimeters. The flight test effort exceeded program objectives with over 120 landings, 36 of which were fully automatic differential GPS/inertial landings. Flight test results obtained from post-flight data analysis are discussed. These results include characteristics of differential GPS/inertial error, using the Wallops Island Laser Tracker as a reference. Data on the magnitude of the differential corrections and vertical channel performance with and without radar altimeter augmentation are provided.

Snyder, Scott↗
NASA NTRS1992

Extracting dimensional geometric parameters from B-spline surface models of aircraft

Research that creates techniques to automatically obtain dimensional geometric parameters from the nonuniform B-spline surface description of an object is presented. These techniques have been implemented successfully in the aircraft design software, ACSYNT, a computer-aided design system for conceptual aircraft design created at Virginia Tech and NASA Ames. The techniques created and implemented in this research are also of significance to general-purpose design.

Jayaram, U.↗
NASA NTRS1991

Strategic avionics technology planning

NASA experience in development and insertion of technology into programs had led to a recognition that a Strategic Plan for Avionics is needed for space. In the fall of 1989 an Avionics Technology Symposium was held in Williamsburg, Virginia. In early 1990, as a followon, a NASA wide Strategic Avionics Technology Working Group was chartered by NASA Headquarters. This paper will describe the objectives of this working group, technology bridging, and approaches to incentivize both the federal and commercial sectors to move toward rapidly developed, simple, and reliable systems with low life cycle cost.

Cox, Kenneth J.↗
NASA NTRS1992

Workshop report - A validation study of Navier-Stokes codes for transverse injection into a Mach 2 flow

A CFD (Computational Fluid Dynamics) competition was held at the Third Scramjet Combustor Modeling Workshop to assess the current state-of-the-art in CFD codes for the analysis of scramjet combustors. Solutions from six three-dimensional Navier-Stokes codes were compared for the case of staged injection of air behind a step into a Mach 2 flow. This case was investigated experimentally at the University of Virginia and extensive in-stream data was obtained. Code-to-code comparisons have been made with regard to both accuracy and efficiency. The turbulence models employed in the solutions are believed to be a major source of discrepancy between the six solutions.

Eklund, Dean R.↗
NASA NTRS1992

Precipitation observed by the airborne advanced microwave moisture sounder (AMMS)

Airborne radiometric measurements at frequencies near 92 GHz and 183 GHz were conducted over two precipitation events near Wallops Island, Virginia during February, 1986. The measured brightness temperatures are compared with those from calculations to estimate the snowfall and rainfall rates for both events. The estimated rates over water surface are within a factor of two of those derived from the concurrent measurements by the SPANDAR radar at the NASA Wallops Flight Facility. These estimated rates, however, suggest that both snowfall events are light and close to the threshold of radiometric detection especially over land surface. Observations of additional snowfall events with lower frequency channels are needed to demonstrate the approach and to account for cloud effects.

Chang, A. T. C.↗
NASA NTRS1991

Spatial transportability of geobotanical spectral signatures associated with soil geochemical anomalies

Consideration is given to a specific problem of spectral signature extension through examination and comparison of multitemporal spectral data signatures developed over a generalized, along-strike geochemical trend located within eastern deciduous hardwood forest. The spectral geobotanical signatures associated with soil Pb, Cu, and Zn anomalies were examined in south-central Virginia. Spectral discrimination between a training pair of anomalous and control sites within the Mineral district was 100 percent successful. It is concluded that spectral geobotanical signatures serve to identify regions of lowered biomass, lowered vigor, and/or differing species composition.

Bell, R.↗
NASA NTRS1993

Flight and wind-tunnel calibrations of a flush airdata sensor at high angles of attack and sideslip and at supersonic Mach numbers

A nonintrusive airdata-sensing system was calibrated in flight and wind-tunnel experiments to an angle of attack of 70 deg and to angles of sideslip of +/- 15 deg. Flight-calibration data have also been obtained to Mach 1.2. The sensor, known as the flush airdata sensor, was installed on the nosecap of an F-18 aircraft for flight tests and on a full-scale F-18 forebody for wind-tunnel tests. Flight tests occurred at the NASA Dryden Flight Research Facility, Edwards, California, using the F-18 High Alpha Research Vehicle. Wind-tunnel tests were conducted in the 30- by 60-ft wind tunnel at the NASA LaRC, Hampton, Virginia. The sensor consisted of 23 flush-mounted pressure ports arranged in concentric circles and located within 1.75 in. of the tip of the nosecap. An overdetermined mathematical model was used to relate the pressure measurements to the local airdata quantities. The mathematical model was based on potential flow over a sphere and was empirically adjusted based on flight and wind-tunnel data. For quasi-steady maneuvering, the mathematical model worked well throughout the subsonic, transonic, and low supersonic flight regimes. The model also worked well throughout the angle-of-attack and sideslip regions studied.

Moes, Timothy R.↗
NASA NTRS1992

C-band measurement of radar backscatter from the ocean surface during SWADE

A preliminary analysis of backscatter measurements collected during the joint NASA/ONR Surface Wave Dynamics Experiment (SWADE) by a C-band scatterometer (C-SCAT) is presented. Data were collected during a total of ten flights on board the NASA/Ames C-130B off the coast of Virginia. These backscatter measurements are vertically polarized, and were obtained over a full 360* in azimuth, at incidence angles ranging from 20 to 50 . The data set is now in a state where it can provide a unique test bed for normalized radar cross section (NRCS) model functions because of the variety of phenomena encountered, and the quantity and quality of the measurements.

Carson, S. C.↗
NASA NTRS1988

A comparison of two OTVs

For a low Earth orbit (LEO) to geosynchronous orbit (GEO) mission scenario, it can be shown that both a chemically-propelled, aerobraked orbital transfer vehicle (OTV), and a high-thrust, nuclear OTV use approximately 50 percent less propellant than a comparable, chemical OTV. At the University of Virginia two teams worked on designs for these types of OTVs. One group formed WWSR Inc. and worked on the aerobraked OTV, which was named Project Orion. The other group, named MOVERS, collaborated on the design for the nuclear engine OTV. This report will briefly review the nature and specifics of their work. This will summarize each of these propellant systems and their corresponding cost savings. It will also highlight the strengths and weaknesses of each OTV concept.

Source record↗