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At least 847 records · Page 47

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NASA NTRS1938

The estimation of the rate of change of yawing moment with sideslip

Wind-tunnel data are presented on the rate of change of yawing moment with sideslip for tests of 9 complete airplane models, 20 fuselage shapes, and 3 wing models with various combinations of dihedral, sweepback, and twist. The data were collected during a survey of existing information, which was made to find a reliable method of computing the yawing moment due to sideslip. Important errors common to methods of computation used at present appear to be due to large interference effects, the investigation of which will undoubtedly require an extensive program of systematic wind-tunnel tests. At present it is necessary to place considerable reliance on past design experience in proportioning an airplane so as to obtain a reasonable degree of directional stability.

Imlay, Frederick H↗

NASA NTRS1988

Mathematical and statistical analysis

The goal of the mathematical and statistical analysis component of RICIS is to research, develop, and evaluate mathematical and statistical techniques for aerospace technology applications. Specific research areas of interest include modeling, simulation, experiment design, reliability assessment, and numerical analysis.

Houston, A. Glen↗

NASA NTRS1992

Activities relating to understanding the initiation, organization and structure of moist convection in the Southeast environment

In the spring and summer of 1986, NASA/Marshall Space Flight Center (MSFC) will sponsor the Satellite Precipitation And Cloud Experiment (SPACE) to be conducted in the Central Tennessee, Northern Alabama, and Northeastern Mississippi area. The field program will incorporate high altitude flight experiments associated with meteorological remote sensor development for future space flight, and an investigation of precipitation processes associated with mesoscale and small convective systems. In addition to SPACE, the MIcroburst and Severe Thunderstorm (MIST) program, sponsored by the National Science Foundation (NSF), and the FAA-Lincoln Laboratory Operational Weather Study (FLOWS), sponsored by the Federal Aviation Administration (FAA), will take place concurrently within the SPACE experiment area. All three programs (under the joint acronym COHMEX (COoperative Huntsville Meteorological EXperiment)) will provide a data base for detailed analysis of mesoscale convective systems while providing ground truth comparisons for remote sensor evaluation. The purpose of this document is to outline the experiment design criteria for SPACE, and describe the special observing facilities and data sets that will be available under the COHMEX joint program. In addition to the planning of SPACE-COHMEX, this document covers three other parts of the program. The field program observations' main activity was the operation of an upper air rawinsonde network to provide ground truth for aircraft and spacecraft observations. Another part of the COHMEX program involved using boundary layer mesoscale models to study and simulate the initiation and organization of moist convection due to mesoscale thermal and mechanical circulations. The last part of the program was the collection, archival and distribution of the resulting COHMEX-SPACE data sets.

Mcnider, Richard T.↗

NASA NTRS1991

Spectral analysis of resting cardiovascular variables and responses to oscillatory LBNP before and after 6 degree head dowm bedrest

A major focus of our research program is to develop noninvasive procedures for determining changes in cardiovascular function associated with the null gravity environment. We define changes in cardiovascular function to be (1) the result of the regulatory system operating at values different from 'normal' but with an overall control system basically unchanged by the null gravity exposure, or (2) the result of operating with a control system that has significantly different regulatory characteristics after an exposure. To this end, we have used a model of weightlessness that consisted of exposing humans to 2 hrs. in the launch position, followed by 20 hrs. of 6 deg head down bedrest. Our principal objective was to use this model to measure cardiovascular responses to the 6 deg head down bedrest protocol and to develop the most sensitive 'systems identification' procedure for indicating change. A second objective, related to future experiments, is to use the procedure in combination with experiments designed to determine the degree to which a regulatory pathway has been altered and to determine the mechanisms responsible for the changes.

Knapp, Charles F.↗

NASA NTRS1993

Flash melting of chondrule precursors in excess of 1600 C. Series 1: Type 2 (B1) chondrule composition experiments

Several questions in chondrule production remain an enigma despite years of experiments. What were the melting temperatures experienced by chondrules? What were the physical characteristics of chondrule precursors? How and why did volatile elements (i.e. Na) found within chondrules survive the formation process? We present the initial results of a series of experiments designed to investigate the above questions by using flash melting to duplicate the melting stage of chondrule formation.

Connolly, Harold C., Jr.↗

NASA NTRS1993

Principal investigators data package for Project Initiation Conference (PIC): EUVS sounding rocket no. 36.117CL. Target: Venus

The region of the UV between 500 and 1200 A is a rich one for the study of planetary and astrophysical targets. EUV atmospheric spectroscopy opens up an important window on ion and neutral nitrogen, oxygen, and noble gas emissions. In this document we describe the specific scientific background and motivations for this Venus EUV rocket observation along with experiment design and mission parameters.

Stern, S. Alan↗

NASA NTRS1993

Space Applications Industrial Laser System (SAILS)

A program is underway to develop a YAG laser based materials processing workstation to fly in the cargo bay of the Space Shuttle. This workstation, called Space Applications Industrial Laser System (SAILS), will be capable of cutting and welding steel, aluminum, and Inconel alloys of the type planned for use in constructing the Space Station Freedom. As well as demonstrating the ability of a YAG laser to perform remote (fiber-optic delivered) repair and fabrication operations in space, fundamental data will be collected on these interactions for comparison with terrestrial data and models. The flight system, scheduled to fly in 1996, will be constructed as three modules using standard Get-Away-Special (GAS) canisters. The first module holds the laser head and cooling system, while the second contains a high peak power electrical supply. The third module houses the materials processing workstation and the command and data acquisition subsystems. The laser head and workstation cansisters are linked by a fiber-optic cable to transmit the laser light. The team assembled to carry out this project includes Lumonics Industrial Products (laser), Tennessee Technological University (structural analysis and fabrication), Auburn University Center for Space Power (electrical engineering), University of Waterloo (low-g laser process consulting), and CSTAR/UTSI (data acquisition, control, software, integration, experiment design). This report describes the SAILS program and highlights recent activities undertaken at CSTAR.

Mccay, T. D.↗

NASA NTRS1993

Characterization and durability testing of plasma-sprayed zirconia-yttria and hafnia-yttria thermal barrier coatings. Part 2: Effect of spray parameters on the performance of several hafnia-yttria and zirconia-yttria coatings

This is the second of two reports which discuss initial experiments on thermal barrier coatings prepared and tested in newly upgraded plasma spray and burner rig test facilities at LeRC. The first report, part 1, describes experiments designed to establish the spray parameters for the baseline zirconia-yttria coating. Coating quality was judged primarily by the response to burner rig exposure, together with a variety of other characterization approaches including thermal diffusivity measurements. That portion of the study showed that the performance of the baseline NASA coating was not strongly sensitive to processing parameters. In this second part of the study, new hafnia-yttria coatings were evaluated with respect to both baseline and alternate zirconia-yttria coatings. The hafnia-yttria and the alternate zirconia-yttria coatings were very sensitive to plasma-spray parameters in that high-quality coatings were obtained only when specific parameters were used. The reasons for this important observation are not understood.

Miller, Robert A.↗

NASA NTRS1993

Integrating payload design, planning, and control in the Dutch Utilisation Centre

Spacecraft payload design, experiment planning and scheduling, and payload control are traditionally separate areas of activity. This paper describes the development of a prototype software tool--the Activity Scheduling System (ASS)--which integrates these activity areas. ASS is part of a larger project to build a Dutch Utilisation Centre (DUC), intended eventually to support all space utilization activities in The Netherlands. ASS has been tested on the High Performance Capillary Electrophoresis payload. The paper outlines the integrated preparation and operations concept embodied in ASS. It describes the ASS prototype, including a typical session. The results of testing are summarized. Possible enhancement of ASS, including integration into DUC, is sketched.

Grant, T. J.↗

NASA NTRS1994

Development of braided rope engine seals

In this study, after reviewing current seal design concepts, the potential of textile structures for seal design is examined from the material, structural, and fabrication points of view. Braided structures are identified as potential candidates for hypersonic seal structures because of their conformability and design flexibility. A large family of braided structures using 2-D and 3-D architecture can be designed using well established methods to produce a wide range of braiding yarn orientation for wear resistance as well as seal porosity control. As a first demonstration of the approach, 2-D braided fiberglass seals were fabricated according to a factorial design experiment by varying braiding angles, fractional longitudinal fibers, and preload pressure levels. Factorial diagrams and response surfaces were constructed to elucidate the inter-relationship of the braiding parameters as well as the effect of preload pressures on leakage resistance of the seal. It was found that seal resistance is a strong function of fractional longitudinal fiber content. As braiding angle increases, seal leakage resistance increases, especially at high preload pressures and in seals having high proportion of longitudinal fibers.

Ko, Frank K.↗

NASA NTRS1991

Phasing the Very Large Array on Galileo in the presence of Jupiter's strong radio emission

Work is in progress to determine the feasibility of using the Very Large Array (VLA) radio telescope to receive telemetry from Galileo during its close encounter with Io on 7 Dec. 1995. The VLA was used previously to receive telemetry from Voyager 2 at Neptune. However, Jupiter's strong radio emission is an additional complication in the case of the Galileo encounter. This article analyzes the effect of Jupiter's radio emission on the phase-adjustment procedure ('autophasing') used to maintain coherence among the 27 VLA antennas. Results of an experiment designed to mimic the Io encounter are presented. As expected, Jupiter's strong radio emission has a considerable effect on the autophasing procedure. A simple emission model is found to give a good approximation to the fringe-visibility plots derived from the VLA data, and that successful model is used to estimate the VLA's ability to autophase on Galileo during the Io encounter. The effect of Jupiter should be small for projected baselines longer than approximately 800 m and completely negligible for projected baselines longer than approximately 1.1 km. The most extended configuration of the VLA (the A configuration) probably can be used successfully for telemetry reception during the Io encounter. Further analysis and testing of the effect of correlated noise from Jupiter is necessary before a final decision can be made about the feasibility of using the second largest (B) configuration of the VLA for reception of Galileo telemetry. Use of the B configuration could simplify the upgrades needed to support the Io encounter. Tests to help choose the preferred VLA configuration could be performed by using the VLA to observe the Magellan spacecraft at Venus during Jul. and Oct. 1991. Examination of the effects of planet noise on the VLA have implications beyond the use of that telescope for supporting the Io encounter. The effects of planet radio emission on spacecraft data received by antenna arrays are relevant to choosing the exact locations of antennas that might be built by the Deep Space Network in coming years.

Ulvestad, J. S.↗

NASA NTRS1994

Operations summary for the convection and moisture experiment (CAMEX)

During the fall of 1993, NASA sponsored a field program called the Convection and Moisture Experiment (CAMEX) at Wallops Island, Virginia. CAMEX was a multidisciplinary experiment design to measure the three dimensional moisture fields over Wallops Island and to characterize the multifrequency radiometric signature of tropical convection over the Gulf Stream and southeastern Atlantic Ocean. This document summarizes the daily CAMEX activities, including ground and aircraft (NASA ER-2) operations, and includes 'quick-look' summaries of data acquisition along with data examples provided by the various CAMEX PI's.

Griffin, V. L.↗

NASA NTRS1994

Three dimensional audio versus head down TCAS displays

The advantage of a head up auditory display was evaluated in an experiment designed to measure and compare the acquisition time for capturing visual targets under two conditions: Standard head down traffic collision avoidance system (TCAS) display, and three-dimensional (3-D) audio TCAS presentation. Ten commercial airline crews were tested under full mission simulation conditions at the NASA Ames Crew-Vehicle Systems Research Facility Advanced Concepts Flight Simulator. Scenario software generated targets corresponding to aircraft which activated a 3-D aural advisory or a TCAS advisory. Results showed a significant difference in target acquisition time between the two conditions, favoring the 3-D audio TCAS condition by 500 ms.

Begault, Durand R.↗

NASA NTRS1994

Participation in the scientific activities of the Waves in Space Plasma (WISP) project

This is the Final Report for Contract NAG5-1925, that consisted of experiment design, for possible use by the space science mission called WISP (Waves in Space Plasma). This mission is under study by the Canadian Space Agency and by NASA. Two WISP configurations are contemplated, under the name of BICEPS: one is called BOLAS, and the other WISPRS. Both these configurations are meant to perform bistatic sounding of the ionosphere, at a height close to F(sub 2) H(sub max) (about 350 Km), with a pair of satellites, either tethered or in free flight. Investigation A (with Y.L. Alpert as P.I.) addresses the subject of parametric decay effects, expected to arise in a magnetoplasma under the influence of high-intensity HF fields. Criteria were formulated that could be used in searching for parametric instabilities and of electric fields in the ionosphere and magnetosphere, by in-situ satellites, such as the BICEPS Pair. Investigation B (with M.D.Grossi as P.I.) addressed the bistatic measurement, by the BICEPS pair,of ionospheric features, such as large-scale and small-scale disturbances, travelling ionospheric disturbances, electron density irregularities, spread-F phenomena, etc. These measurements by BICEPS could be correlated with the waveform distortion and degradation experienced by microwave links from geosynchronous height to ground, such as the ACTS satellite, expected to radiate pulses as short as 1 nanosecond in the band 20 to 30 GHz. These links are transionospheric and propagate e.m. waves in the volume of the ionosphere where BICEPS operates. It will be possible, therefore, to correlate the two classes of measurements, and learn the causative mechanisms that are responsible for the time-spread and frequency-spread nature of communications waveforms at microwave, in geosynchronous height to ground paths.

Alpert, Yakov L.↗

NASA NTRS1994

Piloted simulation study of two tilt-wing flap control concepts, phase 2

A two phase piloted simulation study has been conducted in the Ames Vertical Motion Simulator to investigate alternative wing and flap controls for tilt-wing aircraft. This report documents the flying qualities results and findings of the second phase of the piloted simulation study and describes the simulated tilt-wing aircraft, the flap control concepts, the experiment design and the evaluation tasks. The initial phase of the study compared the flying qualities of both a conventional programmed flap and an innovative geared flap. The second phase of the study introduced an alternate method of pilot control for the geared flap and further studied the flying qualities of the programmed flap and two geared flap configurations. In general, the pilot ratings showed little variation between the programmed flap and the geared flap control concepts. Some differences between the two control concepts were noticed and are discussed in this report. The geared flap configurations had very similar results. Although the geared flap concept has the potential to reduce or eliminate the pitch control power requirements from a tail rotor or a tail thruster at low speeds and in hover, the results did not show reduced tail thruster pitch control power usage with the geared flap configurations compared to the programmed flap configuration. The addition of pitch attitude stabilization in the second phase of simulation study greatly enhanced the aircraft flying qualities compared to the first phase.

Birckelbaw, Lourdes G.↗

NASA NTRS1994

Statistical design study of lunar ceramic

Fabrication of a lunar ceramic was conducted according to a statistically designed experiment. The method of cold pressing was used since the consumption of electrical energy is kept to a minimum (a priority in the lunar environment). This traditional fabrication technique also provides an initial data source on which further investigations can be based. Results obtained from using two percent binder, a cold pressing pressure of 276 MPa, and 24 hours sintering time yielded the greatest compressive strength of 247 MPa. Analysis of each variable's influence on the compressive strength is also presented.

Effinger, Mike↗

NASA NTRS1995

Observed acoustic and aeroelastic spectral responses of a MOD-2 turbine blade to turbulence excitation

Early results from a recent experiment designed to directly evaluate the aeroacoustic/elastic spectral responses of a MOD-2 turbine blade to turbulence-induced unsteady blade loads are discussed. The experimental procedure consisted of flying a hot-film anemometer from a tethered balloon in the turbine inflow and simultaneously measuring the fluctuating airload and aeroelastic response at two blade span stations (65% and 87% spans) using surface-mounted, subminiature pressure transducers and standard strain gage instrumentation. The radiated acoustic pressure field was measured with a triad of very-low-frequency microphones placed at ground level, 1.5 rotor diameters upwind of the disk. Initial transfer function estimates for acoustic radiation, blade normal forces, flapwise acceleration/displacement, and chord/flapwise moments are presented.

Kelley, N. D.↗

NASA NTRS1994

Growing season boundary layer climate and surface exchanges in a subarctic lichen woodland

Between June and August 1990, observations were made at two surface micrometeorological towers near Schefferville Quebec (54 deg 52 min N, 66 deg 40.5 min W), one in a fen and one in the subarctic lichen woodland, and at four surface climatological stations. Data from these surface stations were supplemented by regular radiosonde launches. Supporting measurements of radiative components and soil temperatures allowed heat and moisture balances to be obtained at two sites. The overall surface meteorological experiment design and results of micrometeorological observations made on a 30-m tower in the lichen woodland are presented here. Seasonal variation in the heat and water vapor transport characteristics illustrate the marked effect of the late summer climatological shift in air mass type. During the first half of the summer, average valley sidewalls only 100 m high are sufficient to channel winds along the valley in the entire convective boundary layer. Channeling effects at the surface, known for some time at the long-term climate station in Schefferville, are observed both at ridge top and in the valley, possibly the response of the flow to the NW-SE orientation of valleys in the region. Diurnal surface temperature amplitude at ridge top (approximately equal to 10 C) was found to be half that observed in the valley. Relatively large differences in precipitation among these stations and the climatological station at Schefferville airport were observed and attributed to the local topography. Eddy correlation observations of the heat, moisture and momentum transports were obtained from a 30-m tower above a sparse (approximately equal to 616 stems/ha) black spruce lichen woodland. Properties of the turbulent surface boundary layer agree well with previous wind tunnel studies over idealized rough surfaces. Daytime Bowen ratios of 2.5-3 are larger than those reported in previous studies. Surface layer flux data quality was assessed by looking at the surface layer heat balance. Diurnal and seasonal scale heat budget imbalances were found. We suggest that unmeasured surface heat storage may be responsible for some of the observed imbalance. The presence of the unexplained residual in this and other studies of energy balance over forests casts a note of caution on the interpretation of energy balance components obtained using heat residual methods.

Fitzjarrald, David R.↗