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At least 1,207 records · Page 67

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NASA NTRS1996

Testing of 100 mK bolometers for space applications

Electrical and optical performance data are presented for a prototype 100 mK spider-web bolometer operating under very low photon backgrounds. These data are compared with the bolometer theory and are used to estimate the expected sensitivity of such a detector used for low background space astronomy. The results demonstrate that the sensitivity and speed of response requirements of the bolometer instruments proposed for these missions can be met by 100 mK spider-web bolometers using neutron transmutation doped germanium as the temperature sensitive element.

Murray, A. G.↗

NASA NTRS1996

An interactive parallel programming environment applied in atmospheric science

This article introduces an interactive parallel programming environment (IPPE) that simplifies the generation and execution of parallel programs. One of the tasks of the environment is to generate message-passing parallel programs for homogeneous and heterogeneous computing platforms. The parallel programs are represented by using visual objects. This is accomplished with the help of a graphical programming editor that is implemented in Java and enables portability to a wide variety of computer platforms. In contrast to other graphical programming systems, reusable parts of the programs can be stored in a program library to support rapid prototyping. In addition, runtime performance data on different computing platforms is collected in a database. A selection process determines dynamically the software and the hardware platform to be used to solve the problem in minimal wall-clock time. The environment is currently being tested on a Grand Challenge problem, the NASA four-dimensional data assimilation system.

Interactive Display Devices↗

NASA NTRS1998

Use of Airport Noise Complaint Files to Improve Understanding of Community Response to Aircraft Noise

This study assessed the feasibility of using complaint information archived by modem airport monitoring systems to conduct quantitative analyses of the causes of aircraft noise complaints and their relationship to noise- induced annoyance. It was found that all computer-based airport monitoring systems provide at least rudimentary tools for performing data base searches by complainant name, address, date, time of day, and types of aircraft and complaints. Analyses of such information can provide useful information about longstanding concerns, such as the extent to which complaint rates are driven by objectively measurable aspects of aircraft operations; the degree to which changes in complaint rates can be predicted prior to implementation of noise mitigation measures; and the degree to which aircraft complaint information can be used to simplify and otherwise improve prediction of the prevalence of noise-induced annoyance in communities.

Fidell, Sanford↗

NASA NTRS1998

Preliminary In-Flight Loads Analysis of In-Line Launch Vehicles using the VLOADS 1.4 Program

To calculate structural loads of in-line launch vehicles for preliminary design, a very useful computer program is VLOADS 1.4. This software may also be used to calculate structural loads for upper stages and planetary transfer vehicles. Launch vehicle inputs such as aerodynamic coefficients, mass properties, propellants, engine thrusts, and performance data are compiled and analyzed by VLOADS to produce distributed shear loads, bending moments, axial forces, and vehicle line loads as a function of X-station along the vehicle's length. Interface loads, if any, and translational accelerations are also computed. The major strength of the software is that it enables quick turnaround analysis of structural loads for launch vehicles during the preliminary design stage of its development. This represents a significant improvement over the alternative-the time-consuming, and expensive chore of developing finite element models. VLOADS was developed as a Visual BASIC macro in a Microsoft Excel 5.0 work book on a Macintosh. VLOADS has also been implemented on a PC computer using Microsoft Excel 7.0a for Windows 95. VLOADS was developed in 1996, and the current version was released to COSMIC, NASA's Software Technology Transfer Center, in 1997. The program is a copyrighted work with all copyright vested in NASA.

Graham, J. B.↗

NASA NTRS1960

Performance of Several Conical Convergent-Divergent Rocket-Type Exhaust Nozzles

An investigation was conducted to obtain nozzle performance data with relatively large-scale models at pressure ratios as high as 120. Conical convergent-divergent nozzles with divergence angles alpha of 15, 25, and 29 deg. were each tested at area ratios of approximately 10, 25, and 40. Heated air (1200 F) was supplied at the nozzle inlet at pressures up to 145 pounds per square inch absolute and was exhausted into quiescent air at pressures as low as 1.2 pounds per square inch absolute. Thrust ratios for all nozzle configurations are presented over the range of pressure ratios attainable and were extrapolated when possible to design pressure ratio and beyond. Design thrust ratios decreased with increasing nozzle divergence angle according to the trend predicted by the (1 + cos alpha)/2 parameter. Decreasing the nozzle divergence angle resulted in sizable increases in thrust ratio for a given surface-area ratio (nozzle weight), particularly at low nozzle pressure ratios. Correlations of the nozzle static pressure at separation and of the average static pressure downstream of separation with various nozzle parameters permitted the calculation of thrust in the separated-flow region from unseparated static-pressure distributions. Thrust ratios calculated by this method agreed with measured values within about 1 percent.

Campbell, C. E.↗

NASA NTRS1961

Wind-Tunnel Investigation of Paraglider Models at Supersonic Speeds

An investigation was made in the Langley Unitary Plan wind tunnel to determine the behavior of paraglider models at moderate to high supersonic speeds. The models were deployed from a sting in the supersonic stream and steady-state aerodynamic performance data were obtained. Maximum values of the lift-drag ratio were about 1.4 at a Mach number of 2.65 and about 1.2 at a Mach number of 4.65. The angles of attack over which the models could be flown were limited by unsteady behavior of the canopy.

Taylor, Robert T.↗

NASA NTRS1998

TRMM Solar Array Panels

This final report presents conclusions/recommendations concerning the TRMM Solar Array; deliverable list and schedule summary; waivers and deviations; as-shipped performance data, including flight panel verification matrix, panel output detail, shadow test summary, humidity test summary, reverse bias test panel; and finally, quality assurance summary.

Source record↗

NASA NTRS1999

800 Hours of Operational Experience from a 2 kW(sub e) Solar Dynamic System

From December 1994 to September 1998, testing with a 2 kW(sub e) Solar Dynamic power system resulted in 33 individual tests, 886 hours of solar heating, and 783 hours of power generation. Power generation ranged from 400 watts to over 2 kW(sub e), and SD system efficiencies have been measured up to 17 per cent, during simulated low-Earth orbit operation. Further, the turbo-alternator-compressors successfully completed 100 start/stops on foil bearings. Operation was conducted in a large thermal/vacuum facility with a simulated Sun at the NASA Lewis Research Center. The Solar Dynamic system featured a closed Brayton conversion unit integrated with a solar heat receiver, which included thermal energy storage for continuous power output through a typical low-Earth orbit. Two power conversion units and three alternator configurations were used during testing. This paper will review the test program, provide operational and performance data, and review a number of technology issues.

Shaltens, Richard K.↗

NASA NTRS1999

Computing with Beowulf

Parallel computers built out of mass-market parts are cost-effectively performing data processing and simulation tasks. The Supercomputing (now known as "SC") series of conferences celebrated its 10th anniversary last November. While vendors have come and gone, the dominant paradigm for tackling big problems still is a shared-resource, commercial supercomputer. Growing numbers of users needing a cheaper or dedicated-access alternative are building their own supercomputers out of mass-market parts. Such machines are generally called Beowulf-class systems after the 11th century epic. This modern-day Beowulf story began in 1994 at NASA's Goddard Space Flight Center. A laboratory for the Earth and space sciences, computing managers there threw down a gauntlet to develop a $50,000 gigaFLOPS workstation for processing satellite data sets. Soon, Thomas Sterling and Don Becker were working on the Beowulf concept at the University Space Research Association (USRA)-run Center of Excellence in Space Data and Information Sciences (CESDIS). Beowulf clusters mix three primary ingredients: commodity personal computers or workstations, low-cost Ethernet networks, and the open-source Linux operating system. One of the larger Beowulfs is Goddard's Highly-parallel Integrated Virtual Environment, or HIVE for short.

Cohen, Jarrett↗

NASA NTRS1998

The UNO Aviation Monograph Series: The Airline Quality Rating 1998

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline performance on combined multiple factors important to consumers. Development history and calculation details for the AQR rating system are detailed in The Airline Quality Rating 1991 issued in April, 1991, by the National Institute for Aviation Research at Wichita State University. This current report, Airline Quality Rating 1998, contains monthly Airline Quality Rating scores for 1997. Additional copies are available by contacting Wichita State University or University of Nebraska at Omaha. The Airline Quality Rating 1998 is a summary of month-by-month quality ratings for the ten major U.S. airlines operating during 1997. Using the Airline Quality Rating system and monthly performance data for each airline for the calendar year of 1997, individual and comparative ratings are reported. This research monograph contains a brief summary of the AQR methodology, detailed data and charts that track comparative quality for major airlines domestic operations for the 12 month period of 1997, and industry average results. Also, comparative Airline Quality Rating data for 1991 through 1996 are included to provide a longer term view of quality in the industry.

Bowen, Brent D.↗

NASA NTRS1997

The UNO Aviation Monograph Series: The Airline Quality Rating 1997

The Airline Quality Rating (AQR) was developed and first announced in early 1991 as an objective method of comparing airline performance on combined multiple factors important to consumers. Development history and calculation details for the AQR rating system are detailed in The Airline Quality Rating 1991 issued in April, 1991, by the National Institute for Aviation Research at Wichita State University. This current report, Airline Rating 1997, contains monthly Airline Quality Rating scores for 1996. Additional copies are available by contacting Wichita State University or the University of Nebraska at Omaha. The Airline Quality Rating (AQR) 1997 is a summary of a month-by-month quality ratings for the nine major domestic U.S. airlines operating during 1996. Using the Airline Quality Rating system and monthly performance data for each airline for the calendar year of 1996, individual and comparative ratings are reported. This research monograph contains a brief summary of the AQR methodology, detailed data and charts that track comparative quality for major domestic airlines across the 12 month period of 1996, and industry average results. Also comparative Airline Quality Rating data for 1991 through 1995 are included to provide a longer term view of quality in the industry.

Bowen, Brent D.↗

NASA NTRS1999

Control of a Thrust Alignment Table for Modeling the Coning Dynamics of a Spinning Spacecraft with a Follower Force

This document presents a system controlling the motion of a spherical air bearing used in the modeling of spacecraft dynamics and controls in a laboratory environment. The system is part of the Spinning Rocket Simulator (SRS), used to simulate the coning of spacecraft during a thrusting stage. The reaction force at the spherical air bearing supporting the spacecraft model must coincide with the thrust axis of the model for proper simulation. Therefore, the bearing is translated in a circular path to introduce a centrifugal force. This horizontal force along with the gravitational reaction force at the bearing combines to simulate the direction of the spacecraft's thrust force. The control system receives attitude information from the spacecraft model via a laser beam embedded in the model that impinges on a photosensitive array. The non-linear system is controlled using high-speed lookup tables and digital techniques. A vector-controlled motor and a stepper motor are given the necessary signals to accurately control the turntable and platform supporting the air bearing. Preliminary performance data is presented. Mechanical elements of the table and platform are described in detail. A wireless (RF) data path for all devices on the spacecraft model to an off-table command computer is also described.

Halsmer, Dominic↗

NASA NTRS1999

Overview of the Testing of a Small-Scale Proprotor

This paper presents an overview of results from the wind tunnel test of a 1/4-scale V-22 proprotor in the Duits-Nederlandse Windtunnel (DNW) in The Netherlands. The small-scale proprotor was tested on the isolated rotor configuration of the Tilt Rotor Aeroacoustic Model (TRAM). The test was conducted by a joint team from NASA Ames, NASA Langley, U.S. Army Aeroflightdynamics Directorate, and The Boeing Company. The objective of the test was to acquire a benchmark database for validating aeroacoustic analyses. Representative examples of airloads, acoustics, structural loads, and performance data are provided and discussed.

Young, Larry A.↗

NASA NTRS1998

Video Guidance Sensor Flight Experiment Results

NASA's Marshall Space Flight Center flew on the STS-87 mission an active sensor system, the Video Guidance Sensor (VGS), to demonstrate its functioning in space and to collect performance data. The VGS was designed to provide near-range sensor data as part of an automatic rendezvous and docking system. The sensor determines the relative positions and attitudes between the active sensor and the passive target. The VGS uses laser diodes to illuminate retro-reflectors in the target, a solid-state camera to detect the return from the target, and a frame grabber and digital signal processor to convert the video information into the relative positions and attitudes. The system is designed to operate with the target within a relative azimuth of +/- 9.5 degrees and a relative elevation of +/- 7.5 degrees. The system will acquire and track the target within that field-of-view anywhere from 1.5 meters to 110 meters range, and is designed to acquire at relative attitudes of +/- 10 degrees in pitch and yaw and at any roll angle. The data is output from the sensor at 5 Hz, and the target and sensor software have been designed to permit two independent sensors to operate simultaneously (in order to allow for redundancy). The data from the flight experiment includes raw video data from the VGS camera, relative position and attitude measurements from the VGS to the target, independent hand-held laser ranges from the Shuttle Aft Flight Deck to the target, and Remote Manipulator System position data to correlate with the VGS data. The experiment was quite successful and returned much useful information. The experience gained from the design and flight of this experiment will lead to improved video sensors in the future.

Howard, Richard T.↗

NASA NTRS1999

Overview of the NASA Wallops Flight Facility Mobile Range Control System

The NASA GSFC's Wallops Flight Facility (WFF) Mobile Range Control System (MRCS) is based on the functionality of the WFF Range Control Center at Wallops Island, Virginia. The MRCS provides real time instantaneous impact predictions, real time flight performance data, and other critical information needed by mission and range safety personnel in support of range operations at remote launch sites. The MRCS integrates a PC telemetry processing system (TELPro), a PC radar processing system (PCDQS), multiple Silicon Graphics display workstations (IRIS), and communication links within a mobile van for worldwide support of orbital, suborbital, and aircraft missions. This paper describes the MRCS configuration; the TELPro's capability to provide single/dual telemetry tracking and vehicle state data processing; the PCDQS' capability to provide real time positional data and instantaneous impact prediction for up to 8 data sources; and the IRIS' user interface for setup/display options. With portability, PC-based data processing, high resolution graphics, and flexible multiple source support, the MRCS system is proving to be responsive to the ever-changing needs of a variety of increasingly complex missions.

Davis, Rodney A.↗

NASA NTRS1999

Flight Performance of the Balloon Gondola Solar Pointing System

The NASA Solar Pointing System (SPS) has made two operational flights since its test flight in April of 1997. This pointing device was conceived and designed to provide ultra-low power gondola pointing primarily for directing gondola-fixed solar panels toward the sun. While typically consuming less than 5 watts, the system is capable of suspending and pointing up to 3400 kg, The SPS has logged over 25 days of mostly continuous operation. The performance data, including power consumption and pointing accuracy for these two successful flights is presented and analyzed. The data is compared to predictions and test flight data Suggestions for further developments and applications including Ultra-Long Duration Balloon (ULDB) are discussed.

Simpson, Joel↗

NASA NTRS1999

Middle Atmosphere Transport Properties of Assimilated Datasets

One of the most compelling reasons for performing data assimilation in the middle atmosphere is to obtain global, balanced datasets for studies of trace gas transport and chemistry. This is a major motivation behind the Goddard Earth observation System-Data Assimilation System (GEOS-DAS). Previous studies have shown that while this and other data assimilation systems can generally obtain good estimates of the extratropical rotational velocity field, the divergent part of the dynamical field is deficient; this impacts the "residual circulation" and leads to spurious trace gas transport on seasonal and interannual timescales. These problems are impacted by the quality and the method of use of the observational data and by deficiencies in the atmospheric general circulation model. Whichever the cause at any place and time, the "solution" is to introduce non-physical forcing terms into the system (the so-called incremental analysis updates); these can directly (thermal) or indirectly (mechanical) affect the residual circulation. This paper will illustrate how the divergent circulation is affected by deficiencies in both observations and models. Theoretical considerations will be illustrated with examples from the GEOS-DAS and from simplified numerical experiments. These are designed to isolate known problems, such as the inability of models to sustain a quasi-biennial oscillation and sparse observational constraints on tropical dynamics, or radiative inconsistencies in the presence of volcanic aerosols.

Pawson, Steven↗

NASA NTRS1999

Middle Atmospheric Transport Properties of Assimilated Datasets

Pawson, Steven↗