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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Lightning strikes to a NASA airplane penetrating thunderstorms at low altitudes

The NASA Storm Hazards program was dedicated during the 1984 storm season to a study of lightning strikes on an instrumented F-106B aircraft, during penetrations of thunderstorms at altitudes lower than the 6-8 km center of lightning flash density. These altitudes coincide with the negative charge region of thunderstorms. An analysis of the correlation between the UHF band radar data obtained and TV images of lightning strikes indicates that, with a known aircraft position relative to the radar, the lightning channel motion can be adequately interpreted on the basis of radar echo evolution.

Mazur, V.↗
NASA NTRS1985

A new type of VLF emission triggered at low altitude in the subauroral region by Siple Station VLF transmitter signals

The present paper has the objective to report the existence of a new phenomenon in which coherent VLF signals from the Siple Station VLF transmitter (Antarctica, 76 deg S, 84 deg W) are observed to trigger a new type of VLF emission, taking into account the propagation of these signals upward through the ionosphere and low-altitude magnetosphere to the ISIS 2 satellite at 1400 km altitude. The existence of the impulsive emission (IE) effect lends credence to the idea that coherent VLF signals can act as catalysts to trigger natural plasma instabilities in the subauroral ionosphere and lower magnetosphere. Controlled studies of these instabilities may, therefore, be possible.

Bell, T. F.↗
NASA NTRS1985

A constant altitude flight survey method for mapping atmospheric ambient pressures and systematic radar errors

The flight test technique described uses controlled survey runs to determine horizontal atmospheric pressure variations and systematic altitude errors that result from space positioning measurements. The survey data can be used not only for improved air data calibrations, but also for studies of atmospheric structure and space positioning accuracy performance. The examples presented cover a wide range of radar tracking conditions for both subsonic and supersonic flight to an altitude of 42,000 ft.

Larson, T. J.↗
NASA NTRS1985

Comparison of measured and predicted F2 peak altitude

Different models for the F2 peak altitude hmF2 are compared with mean values determined from incoherent scatter measurements of the radar stations Jicamarca, Peru and Arecibo, Puerto Rico at all local times. The investigation shows that the daytime hmF2 is fairly well represented by the most recent models, whereas at nighttime, higher peak altitudes are measured rather than predicted by either model. The observed diurnal structure is slightly misinterpreted by the models above Jicamarca and is strongly disagreeing above Arecibo.

Bilitza, D.↗
NASA NTRS1986

Low-altitude coverage of ST radars

Clear air ST (stratosphere troposphere) radars are now widely used for atmospheric research and wind profiling. Most attention to date has been directed toward extending the altitude coverage as high as possible. It is also desirable to extend the coverage as low as possible. Any improvement in the low altitude coverage of existing wind profiling radars would be useful. The approximate lower limits of some existing ST radars are listed and what set these limits are briefly examined.

Ecklund, W. L.↗
NASA NTRS1987

Full-scale thrust reverser testing in an altitude facility

A two-dimensional convergent-divergent exhaust nozzle designed and fabricated by Pratt and Whitney Aircraft was installed on a PW1128 turbofan engine and tested during thrust reverser operation in an altitude facility at NASA Lewis Research Center. A unique collection system was used to capture the thrust reverser exhaust gas and transport it to the primary exhaust collector. Tests were conducted at three flight conditions with varying amounts of thrust reverse at each condition. Some reverser exhaust gas spillage by the collection system was encountered but engine performance was unaffected at all flight conditions tested. Based on the results of this test program, the feasibility of altitude testing of advanced multi-function exhaust nozzle systems has been demonstrated.

Mehalic, Charles M.↗
NASA NTRS1987

Integration of altitude and airspeed information into a primary flight display via moving-tape formats

A ground-based aircraft simulation study was conducted to determine the effect on pilot performance of replacing the electromechanical altimeter and airspeed indicators with electronically generated representations integrated into the primary flight display via moving-tape (linear moving scale) formats. Several key factors relating to moving-tape formats were examined during the study: tape centering, secondary (trend) information, and tape orientation. The factor of centering refers to whether the tape was centered about the actual airspeed or altitude or about some defined reference value. Tape orientation refers to whether the values represented are arranged in either descending or ascending order. Six pilots participated in this study, with each subject performing 18 runs along a single, known flight profile. Subjective results indicated that the moving-tape formats were generally better than that of the conventional instruments. They also indicated that an actual-centered fixed pointer was preferred to a reference-centered pointer. Performance data for a visual secondary task showed that formats not containing trend information produced better performance; however, no difference was noted in airspeed tracking or altitude tracking performance. Regarding tape orientation, subjective comments indicated that there was lower work load and better performance when the airspeed tape had the high numbers at the top.

Abbott, Terence S.↗
NASA NTRS1987

Active vehicle charging measurements in sounding rocket and space shuttle orbiter environments at Low Earth Orbit (LEO) altitude

It was concluded that for electron beam emission up to 100mA, vehicle charging is not a significant problem with the Space Shuttle Orbiter. Similarly, sounding rocket payloads have no serious charging problems up to this level of beam current, provided that the maximum amount of the rocket skin is available to collect ionospheric electrons from the LEO altitude range. However, sounding rockets are marginal in their collecting area capability and other effects may occur to balance the beam current when operated at lower altitudes during the night.

Raitt, W. J.↗
NASA NTRS1987

Integration of altitude and airspeed information into a primary flight display via moving-tape formats: Evaluation during random tracking task

A ground-based aircraft simulation study was conducted to determine the effects on pilot preference and performance of integrating airspeed and altitude information into an advanced electronic primary flight display via moving-tape (linear moving scale) formats. Several key issues relating to the implementation of moving-tape formats were examined in this study: tape centering, tape orientation, and trend information. The factor of centering refers to whether the tape was centered about the actual airspeed or altitude or about some other defined reference value. Tape orientation refers to whether the represented values are arranged in descending or ascending order. Two pilots participated in this study, with each performing 32 runs along seemingly random, previously unknown flight profiles. The data taken, analyzed, and presented consisted of path performance parameters, pilot-control inputs, and electrical brain response measurements.

Abbott, Terence S.↗
NASA NTRS1986

Liquid crystals for high-altitude in-flight boundary layer flow visualization

A novel method for visualization of laminar to turbulent boundary layer transition in flight is presented, in which liquid crystal coatings are used to indicate the transition by a change of color (in response to the changes in the wall shear and the temperature). The liquid crystals applied to the wing surfaces were either cholesteric crystals formulated to be active between temperatures of 30 and 100 F or a sample of chiral nematic liquid crystals formulated to be active between -18 and -22 F. Liquid crystal coatings were shown to provide visualization data at flight altitudes and temperatures at which data could not be obtained previously. Flight evaluations were successfully conducted on a T-34C and a Learjet research aircraft at Mach numbers of up to 0.8 and altitudes of up to 50,000 ft. The time response during oscillating sideslip tests was very rapid. In wind tunnel tests, a hysteresislike behavior was observed in the liquid crystal coatings, possibly because of the lower dynamic pressures in wind tunnels as compared to flight.

Gall, P. D.↗
NASA NTRS1986

Median density altitude profiles of the major ions in the central nightside Venus ionosphere

Altitude profiles of median values for total ion density, constituent ion densities, and the molecular ion group of the central nightside Venus ionosphere are presently derived from the Pioneer Venus retarding potential analyzer's measurements during the first five seasonal passages of the spacecraft through the nightside hemisphere. The altitude profiles for total ion density, constituent ions and the molecular ion group are compared with previously predicted profiles derived from numerical models in which the ionization source was O(+) ions transported from the dayside ionosphere and electron impact-produced ionization. The electron impact-produced profiles for O(+) is 2 orders of magnitude smaller than that observed.

Knudsen, William C.↗
NASA NTRS1987

Full-scale thrust reverser testing in an altitude facility

A two-dimensional convergent-divergent exhaust nozzle designed and fabricated by Pratt and Whitney Aircraft was installed on a PW1128 turbofan engine and tested during thrust reverser operation in an altitude facility at NASA Lewis Research Center. A unique collection system was used to capture the thrust reverser exhaust gas and transport it to the primary exhaust collector. Tests were conducted at three flight conditions with varying amounts of thrust reverse at each condition. Some reverser exhaust gas spillage by the collection system was encountered but engine performance was unaffected at all flight conditions tested. Based on the results of this test program, the feasibility of altitude testing of advanced multifunction exhaust nozzle systems has been demonstrated.

Mehalic, Charles M.↗
NASA NTRS1988

Experimental investigation of the subsonic high-altitude operation of the NASA Lewis 10- by 10-foot supersonic wind tunnel

An experimental investigation was conducted in the NASA Lewis 10- by 10-Foot Supersonic Wind Tunnel during subsonic tunnel operation in the aerodynamic cycle to determine the test section flow characteristics near the Advanced Turboprop Project propeller model plane of rotation. The investigation used an eight-probe pitot static flow survey rake to measure total and static pressures at two locations in the wind tunnel: the test section and the bellmouth section (upstream of the two-dimensional flexible-wall nozzle). A cone angularity probe was used to measure any flow angularity in the test section. The evaluation was conducted at tunnel Mach numbers from 0.10 to 0.35 and at three operating altitudes from 2,000 to 50,000 ft. which correspond to tunnel reference total pressures from 1960 to 245 psfa, respectively. The results of this experimental investigation indicate a total-pressure loss area in the center of the test section and a static-pressure gradient from the test section centerline to the wall. These total and static pressure differences were observed at all tunnel operating altitudes and diminished at lower tunnel velocities. The total-pressure loss area was also found in the bellmouth section, which indicates that the loss mechanism is not the tunnel flexible-wall nozzle. The flow in the test section is essentially axial since very small flow angles were measured. The results also indicate that a correction to the tunnel total and static pressures must be applied in order to determine accurate freestream conditions at the test section centerline.

Hughes, Christopher E.↗
NASA NTRS1988

Midlatitude ClO below 22 km altitude - Measurements with a new aircraft-borne instrument

Midlatitude stratospheric ClO at altitudes below 22 km has been measured for the first time. Measurements were made at latitudes between 27 and 48 deg N during three flights from Moffett Field, CA, in June and July of 1987, with a new instrument flown on the NASA ER-2 aircraft. The result from these flights is that the ClO mixing ratio increases from less than 0.5 pptv at 16.8 km to 2.0 pptv at 18.3 km and 10.1 pptv at 21 km. These altitude profiles agree with an extrapolated profile from a May 1986 balloon-borne experiment (Brune and Anderson, 1986).

Brune, Wm. H.↗
NASA NTRS1987

The visual control of simulated altitude

The ability of a subject flying an experimental flight to use the different sources of visual information by looking at the vertical tracking error was investigated using a 3 (altitude) x 3 (texture) x 2 (replication) factorial design. Each subject flew these 18 flights in the same partially counterbalanced order, constructed such that there was one flight at each of the three altitudes, and over each of the three surface textures within each successive set of three flights. The three ground-surface textures used consisted of meridian, latitudinal, and square textures described by Wolpert et al. (1983). The results showed that, in displays where only splay information was available, the subjects tended to confuse lateral motion with vertical.

Johnson, Walter W.↗
NASA NTRS1987

Auroral zone field-aligned currents observed in the magnetotail and at intermediate altitudes - An ISEE perspective

The relationship between low-altitude auroral-zone field-aligned currents and the geomagnetic tail is investigated on the basis of a statistical analysis of ISEE and DE observations. The data are compiled in diagrams and graphs and characterized in detail. It is shown that the large-scale current systems of low-altitude regions 1 and 2 are only reduplicated in 27 percent of the observations at 2-7 earth radii (those associated with the onset of a substorm expansion), while the flow at the plasma-sheet boundary opposes the region 1 polarity (the highest-latitude near-midnight currents being directed earthward).

Elphic, R. C.↗
NASA NTRS1988

Determination of auroral electrostatic potentials using high- and low-altitude particle distributions

The auroral electrostatic potential differences were determined from the particle distribution functions obtained nearly simultaneously above and below the auroral acceleration region by DE-1 at altitudes 9000-15,000 km and DE-2 at 400-800 km. Three independent techniques were used: (1) the peak energies of precipitating electrons observed by DE-2, (2) the widening of loss cones for upward traveling electrons observed by DE-1, and (3) the energies of upgoing ions observed by DE-1. The assumed parallel electrostatic potential difference calculated by the three methods was nearly the same. The results confirmed the hypothesis that parallel electrostatic fields of 1-10 kV potential drop at 1-2 earth radii altitude are an important source for auroral particle acceleration.

Reiff, P. H.↗
NASA NTRS1988

Low-energy ions at low equatorial altitudes

Ion mass composition data, obtained with the ISEE-1 mass spectrometer, and other data are used to study the intense low-energy populations observed in the low-altitude equatorial magnetosphere by Williams and Frank (1984). The observed ions are identified primarily as H(+), O(+), and He(+). Observed peak energies are shown to increase with decreasing altitude and to vary by at least 30 percent over time. It is suggested that a mechanism of resonant wave-particle interaction is responsible for the energization of the observed ions, and that such a mechanism may act in a two-phase mode, resulting in the energization of minor ions up to the local Alfven energy of the ambient plasma.

Williams, D. J.↗