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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Reconstruction of the Genesis Entry

An overview of the reconstruction analyses performed for the Genesis capsule entry is described. The results indicate that the actual entry prior to the drogue deployment failure was very close to the pre-entry predictions. The capsule landed 8.3 km south of the desired target at Utah Test and Training Range. Analysis on infrared video footage (obtained from the tracking stations) during the descent estimated the onset of the capsule tumble at Mach 0.9. Frequency analysis on the infrared video data indicates that the aerodynamics generated for the Genesis capsule reasonably predicted the drag and static stability. Observations of the heatshield support the pre-entry simulation estimates of a small hypersonic angles-of-attack, since there is very little, if any, charring of the shoulder region or the aftbody. Through this investigation, an overall assertion can be made that all the data gathered from the Genesis entry is consistent with flight performance that was close to the nominal preentry prediction. Consequently, the design principles and methodologies utilized for the flight dynamics, aerodynamics, and aerothermodynamics analyses have been corroborated.

Desai, Prasun N.↗
NASA NTRS2017

Autonomous, Context-Sensitive, Task Management Systems and Decision Support Tools II: Contextual Constraints and Information Sources

Recent advances in artificial intelligence, machine learning, data mining and sensor technology have resulted in the availability of a vast amount of digital data and information and the development of advanced automated reasoners. This creates the opportunity for the development of a robust dynamic task manager and decision support tool that is context sensitive and integrates information from a wide array of on-board and off aircraft sourcesa tool that monitors systems and the overall flight situation, anticipates information needs, prioritizes tasks appropriately, keeps pilots well informed, and is nimble and able to adapt to changing circumstances. This is the second of two companion reports exploring issues associated with autonomous, context-sensitive, task management and decision support tools. In the first report, we explored fundamental issues associated with the development of such a system. In this report, we extend this work to focus on two critical aspects of these systems: 1) the constraints and conditions that drive the dynamic prioritization and presentation of data and information to the pilots, and 2) specific data and information to be accessed, monitored, integrated, and displayed in such a system.

context-sensitive↗
NASA NTRS1990

En route noise of two turboprop aircraft

In order to weigh en route noise emissions originating from future propfan powered aircraft, a data base of emission levels from conventional turboprop aircraft is needed. For this reason flyover noise measurements on two twin-engine turboprop aircraft were conducted at flight heights between 17,000 and 21,000 ft. Acoustic data are presented together with propeller operational parameters and environmental meteorological data. Narrowband spectral analyses demonstrate the characteristic features of the measured propeller noise signatures: Noise spectra are dominated by the propeller rotational noise fundamental frequency and pronounced noise beats occur as a consequence of different rotational speeds of the propellers.

Dobrzynski, Werner↗
NASA NTRS1989

Identification and interpretation of patterns in rocket engine data: Artificial intelligence and neural network approaches

This paper describes an expert system which is designed to perform automatic data analysis, identify anomalous events, and determine the characteristic features of these events. We have employed both artificial intelligence and neural net approaches in the design of this expert system. The artificial intelligence approach is useful because it provides (1) the use of human experts' knowledge of sensor behavior and faulty engine conditions in interpreting data; (2) the use of engine design knowledge and physical sensor locations in establishing relationships among the events of multiple sensors; (3) the use of stored analysis of past data of faulty engine conditions; and (4) the use of knowledge-based reasoning in distinguishing sensor failure from actual faults. The neural network approach appears promising because neural nets (1) can be trained on extremely noisy data and produce classifications which are more robust under noisy conditions than other classification techniques; (2) avoid the necessity of noise removal by digital filtering and therefore avoid the need to make assumptions about frequency bands or other signal characteristics of anomalous behavior; (3) can, in effect, generate their own feature detectors based on the characteristics of the sensor data used in training; and (4) are inherently parallel and therefore are potentially implementable in special-purpose parallel hardware.

Ali, Moonis↗
NASA NTRS1999

Low-Energy Sputtering Research

An experimental study is described to measure low-energy (less than 600 eV) sputtering yields of molybdenum with xenon ions using Rutherford backscattering spectroscopy (RBS) and secondary neutral mass spectroscopy (SNMS). An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 (micro)A/sq cm. For RBS measurements, the sputtered material was collected on a thin aluminum strip which was mounted on a semi-circular collector plate. The target was bombarded with 200 and 500 eV xenon ions at normal incidence. The differential sputtering yields were measured using the RBS method with 1 MeV helium ions. The differential yields were fitted with a cosine fitting function and integrated with respect to the solid angle to provide the total sputtering yields. The sputtering yields obtained using the RBS method are in reasonable agreement with those measured by other researchers using different techniques. For the SNMS measurements, 150 to 600 eV xenon ions were used at 50deg angle of incidence. The SNMS spectra were converted to sputtering yields for perpendicular incidence by normalizing SNMS spectral data at 500 eV with the yield measured by Rutherford backscattering spectrometry. Sputtering yields as well as the shape of the yield-energy curve obtained in this manner are in reasonable agreement with those measured by other researchers using different techniques. Sputtering yields calculated by using two semi-spherical formulations agree reasonably well with measured data. The isotopic composition of secondary ions were measured by bombarding copper with xenon ions at energies ranging from 100 eV to 1.5 keV. The secondary ion flux was found to be enriched in heavy isotopes at low incident ion energies. The heavy isotope enrichment was observed to decrease with increasing impact energy. Beyond 700 eV, light isotopes were sputtered preferentially with the enrichment remaining nearly constant.

Ray, P. K.↗
NASA NTRS1975

A new global ionospheric model

A new global ionospheric model has been successfully implemented. The daytime portion of this model provides one-way ionospheric range corrections that compare favorably with those derived from the Mariner Venus Mercury (MVM'73) S- and X-band dual frequency doppler data. For elevation angles, γ, higher than 30 deg and solar zenith angle, X, less than 80 deg, this model provides calibrations accurate to a few centimeters. The calibrations provided by the nighttime model are also very reasonable. These, however, will have to be compared with the S/X data from Viking ‘75 for final confirmation. It is interesting to note that the daytime ionospheric calibrations derived from the current calibration scheme, DIEN/TIEN, are fairly close to those given by the new global model, especially in the temporal variations and thus the doppler effects. In the daytime and for γ ≳ 30 deg and X < 80 deg, the calibrations from the two models agree almost exactly. However, for situations when γ is below 30 deg and X is larger than 80 deg simultaneously, as much as 12% (~70 cm, typically) improvement of the new model over DIEN/TIEN results. The comparison between the nighttime model and DIEN/TIEN has been based on the one-way ionospheric range corrections for three passes near the Mariner 9 encounter with Mars in 1971 tracked at Goldstone. It is found that they can differ by over 30% (typically 20 cm). As mentioned, the confirmation of these nighttime calibrations awaits the availability of the Viking S/X dual frequency doppler data. Finally, the ionospheric calibration effects on orbit determination provided by DIEN/TIEN, the global model, and the S/X data will be intercompared during the Viking Mission.

K. W. Yip↗
NASA NTRS1984

Ground-effect analysis of a jet transport airplane

An analysis of the ground effect of a jet transport airplane has been made. Data were obtained from recent flight tests primarily using the constant angle-of-attack approach technique. Reasonable results were obtained for ground-effect pitching moment and lift increments. These were compared with data from other sources, including computations, wind tunnel, and previous flight test. A recommended ground-effect model was developed from the results. A brief simulator study was conducted to determine the sensitivity of a particular configuration to this ground-effect model and its associated uncertainty.

Curry, R. E.↗
NASA NTRS1985

Ground-effect analysis of a jet transport airplane

An analysis of the ground effect of a jet transport airplane has been made. Data were obtained from recent flight tests primarily using the constant angle-of-attack approach technique. Reasonable results were obtained for ground-effect pitching moment and lift increments. These were compared with data from other sources, including computations, wind tunnel, and previous flight tests. A recommended ground-effect model was developed from the results. A brief simulator study was conducted to determine the sensitivity of a particular configuration to this ground-effect model and its associated uncertainty.

Curry, R. E.↗
NASA NTRS1992

Erosion rates for polymers measured on LDEF

The summary and viewgraphs of work presented at the Long Duration Exposure Facility (LDEF) materials workshop are given. Experimental data for erosion depths and rates for polymers measured on LDEF are given. In general, agreement is reasonably good between erosion rates from the University of Alabama in Huntsville (UAH) LDEF experiment and prior data obtained at much lower mission fluences. Agreement is particularly satisfying in the case of Kapton where the prior data base is large. In spite of the known presence of silicaceous contamination on LDEF surfaces, the erosion rates of the highly erodible materials are hardly affected, if at all. Graphs showing changes in optical properties (reflectance and transmittance) of metal films are included.

Gregory, John C.↗
NASA NTRSDate not supplied

Learjet 25D Jet Noise Flyover Measurements: Comparisons with Scale-Model Data

Continued interest in commercial supersonic flight has highlighted the need for accurate jet-noise predictions as jet noise is expected to be a dominant noise source for aircraft takeoff conditions. The current study compares the acoustic spectra obtained from a scale-model investigation to that from a Learjet 25D flyover test. Reasonable agreement was achieved between the scale-model and flight data in both peak level and frequency when the physical scale factor for the scale-model was increased by roughly 6%. The peak perceived noise levels (PNL) for the flight data were between 1.29 dB and 1.65 dB higher than those for the scale model. The roll-off of PNL with time for large emission angles was greater for the flight data than for the scale-model data. Using a distributed source model for shear-layer-refraction corrections to the scale-model data slightly improved comparisons to flight data at low frequencies for emission angles near 70° and between 110° and 130°. Distributed source models had no impact on the scale-model spectra near the peak jet-noise angle. Applying a stretching factor to the distributed source models to capture the effects of a flight stream had a very limited impact on the computed spectra.

Acoustics↗
NASA NTRS2006

Estimation of Longitudinal Unsteady Aerodynamics of a Wing-Tail Combination From Wind Tunnel Data

This paper presents an initial step toward model identification from wind tunnel data for an airliner configuration. Two approaches to modeling a transport configuration are considered and applied to both steady and large-amplitude forced-oscillation wind tunnel data taken over a wide range of angles of attack. Only limited conclusions could be drawn from this initial data set. Although model estimated time histories of normal force and pitching moment agree reasonably well with the corresponding measured values, model damping parameters did not, for some cases, have values consistent with small amplitude oscillatory data. In addition, large parameter standard errors implied poor information content for model structure determination and parameter estimation. Further investigation of the modeling problem for more general aerodynamic models is recommended with close attention to experiment design for obtaining parameters with high accuracy.

Murphy, Patrick C.↗
NASA NTRS1993

A practical large scale/high speed data distribution system using 8 mm libraries

Eight mm tape libraries are known primarily for their small size, large storage capacity, and low cost. However, many applications require an additional attribute which, heretofore, has been lacking -- high transfer rate. Transfer rate is particularly important in a large scale data distribution environment -- an environment in which 8 mm tape should play a very important role. Data distribution is a natural application for 8 mm for several reasons: most large laboratories have access to 8 mm tape drives, 8 mm tapes are upwardly compatible, 8 mm media are very inexpensive, 8 mm media are light weight (important for shipping purposes), and 8 mm media densely pack data (5 gigabytes now and 15 gigabytes on the horizon). If the transfer rate issue were resolved, 8 mm could offer a good solution to the data distribution problem. To that end Exabyte has analyzed four ways to increase its transfer rate: native drive transfer rate increases, data compression at the drive level, tape striping, and homogeneous drive utilization. Exabyte is actively pursuing native drive transfer rate increases and drive level data compression. However, for non-transmitted bulk data applications (which include data distribution) the other two methods (tape striping and homogeneous drive utilization) hold promise.

Howard, Kevin↗
NASA NTRS2007

Physical Interpretation of the Correlation Between Multi-Angle Spectral Data and Canopy Height

Recent empirical studies have shown that multi-angle spectral data can be useful for predicting canopy height, but the physical reason for this correlation was not understood. We follow the concept of canopy spectral invariants, specifically escape probability, to gain insight into the observed correlation. Airborne Multi-Angle Imaging Spectrometer (AirMISR) and airborne Laser Vegetation Imaging Sensor (LVIS) data acquired during a NASA Terrestrial Ecology Program aircraft campaign underlie our analysis. Two multivariate linear regression models were developed to estimate LVIS height measures from 28 AirMISR multi-angle spectral reflectances and from the spectrally invariant escape probability at 7 AirMISR view angles. Both models achieved nearly the same accuracy, suggesting that canopy spectral invariant theory can explain the observed correlation. We hypothesize that the escape probability is sensitive to the aspect ratio (crown diameter to crown height). The multi-angle spectral data alone therefore may not provide enough information to retrieve canopy height globally

Schull, M. A.↗
NASA NTRS1984

Frequency and site selection criteria for MST radars, part 5.1A

The majority of mesosphere-stratosphere-troposphere (MST) and ST radars are located in or near mountainous terrain. When measuring horizontal velocities, the terrain is a small factor, but when measuring vertical velocities, the meteorological noise induced by rough terrain can severely limit the usefulness of the observations. When the variance of the vertical velocity is too large, it is not possible to suitably filter the data to detect the small synoptic-scale signal with reasonable statistical confidence. The variance of vertical velocity at all tropospheric levels is directly related to the low level wind speed during flow over rough terrain. It is suggested that the synoptic-scale vertical velocity can be measured by ST radars where the terrain is smooth. The large-scale vertical velocity cannot always be reliably determined from MST radar data when the underlying terrain is rough. The vertical velocity is potentially on of future radar site selections, taking into account the desired meteorological applications of the data and engineering design factors. If the synoptic-scale vertical velocity is a desired variable, the radar should not be located near mountains.

Nastrom, G. D.↗
NASA NTRS1992

A program of correlated observations using the EGRET instrument on GRO and the IMB neutrino detector

A reliable, real-time supernova monitoring system was devised using the IMB neutrino detector to serve as an 'early-warning' system for EGRET and other instruments on GRO. New methods and software were developed to allow the IMB monitoring computer in Cleveland to: recognize that a trigger burst had occurred; make a judgement on whether the burst was spurrious or an actual supernova; prepare brief summary files and 'quick-look' data so that a final disposition could be made by a trained scientist; and contact the 'watch' scientist via personal beeper in Baton Rouge. This system ran from Dec. 1990 to Apr. 1991, when the neutrino detector failed for unrelated reasons. In addition to the supernova system, high-energy neutrino data was prepared and formatted for comparison with EGRET gamma-ray data.

Svoboda, Robert C.↗
NASA NTRS1991

Software reliability report

There are many software reliability models which try to predict future performance of software based on data generated by the debugging process. Unfortunately, the models appear to be unable to account for the random nature of the data. If the same code is debugged multiple times and one of the models is used to make predictions, intolerable variance is observed in the resulting reliability predictions. It is believed that data replication can remove this variance in lab type situations and that it is less than scientific to talk about validating a software reliability model without considering replication. It is also believed that data replication may prove to be cost effective in the real world, thus the research centered on verification of the need for replication and on methodologies for generating replicated data in a cost effective manner. The context of the debugging graph was pursued by simulation and experimentation. Simulation was done for the Basic model and the Log-Poisson model. Reasonable values of the parameters were assigned and used to generate simulated data which is then processed by the models in order to determine limitations on their accuracy. These experiments exploit the existing software and program specimens which are in AIR-LAB to measure the performance of reliability models.

Wilson, Larry↗
NASA NTRS1994

Results From The First Interactive Scientific Expert System In Space

We describe recent work on automation and support of science experiments on the Space Shuttle. PI-in-a-Box, the first interactive expert system for scientific support, was flown onboard STS-58 in October 1993. It was designed to help astronauts perform better science in space by providing expert-level advice in real-time. The system provides help with 'technician' tasks such as data acquisition, data quality monitoring, and diagnostic, troubleshooting and repair. The system also performs 'expert' reasoning on the scientific model and experiment steps scheduling. It can make scheduling recommendations based on hardware status, time available, and agreement between predictions and flight data. The system was successfully deployed and used throughout the mission. Most of the 'technician' skills of the system were used with success. The scientific model study performed correctly, but we believe the results were not exploited by the astronauts because of Spacelab operational pressures. Also, portions of the system were designed around rigid schedule constraints that were essentially relaxed during the mission. This version was tailored to a specific vestibular experiment known as the 'rotating dome'. We are currently expanding our effort in various scientific (other life and microgravity sciences experiments) and technological directions (integrated telescience, astronaut science advisor, and autonomous control).

Groleau, Nicolas↗
NASA NTRS1994

Results from the First Interactive Scientific Expert System in Space

We describe recent work on automation and support of science experiments on the Space Shuttle. PI-in-a-Box, the first interactive expert system for scientific support, was flown onboard STS-58 in October 1993. It was designed to help astronauts perform better science in space by providing expert-level advice in real-time. The system provides help with "technician" tasks such as data acquisition, data quality monitoring, and diagnostic, troubleshooting and repair. The system also performs "expert" reasoning on the scientific model and experiment steps scheduling. It can make scheduling recommendations based on hardware status, time available, and agreement between predictions and flight data. The system was successfully deployed and used throughout the mission. Most of the "technician" skills of the system were used with success. The scientific model study performed correctly, but we believe the results were not exploited by the astronauts because of Spacelab operational pressures. Also, portions of the system were designed around rigid schedule constraints that were essentially relaxed during the mission. This version was tailored to a specific vestibular experiment known as the "rotating dome". We are currently expanding our effort in various scientific (other life and microgravity sciences experiments) and technological directions (integrated telescience, astronaut science advisor, and autonomous control).

Groleau, Nicolas↗