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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Lightning Return-Stroke Current Waveforms Aloft, from Measured Field Change, Current, and Channel Geometry

Three-dimensional reconstructions of six rocket-triggered lightning channels are derived from stereo photographs. These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and electric-field-change waveforms measured at a range of 5.2 kilometers for 24 return strokes in these channels. Streak photographs of 14 of the same strokes are analyzed to determine the rise times, propagation speeds, and amplitudes of relative light intensity for comparison with the electrical inferences. Results include the following: 1) The fine structure of the field-change waveforms that were radiated by these subsequent return strokes can be explained, in large part, by channel geometry. 2) The average 10 - 90% rise time of the stroke current increased by about a factor of seven in our sample, from an observed 0.31 plus or minus 0.17 microseconds at the surface to an inferred 2.2 plus or minus 0.5 microcseconds at 1 kilometer path length above the surface. 3) The three-dimensional propagation speed of the current front averaged 1.80 plus or minus 0.24 X 10(exp 8) meters per second over channel lengths typically greater than 1 kilometer. 4) Assuming that the measured current was entirely due to the return stroke forced an unreasonably large and abrupt reduction in inferred current amplitude over the first few tens of meters above the surface, especially in cases when the leader was bright relative to its stroke. Therefore, a significant fraction of the current at the surface was probably due to the leader, at least in such cases. 5) Peak return-stroke currents decreased by approximately 37 plus or minus 12% from 100 meters to 1 kilometer of path length above the surface. Because of uncertainty about how to partition the measured current between leader and return stroke, we are unable to infer the variation of current amplitude near the ground.

Willett, J. C.↗
NASA NTRS1993

Lightning studies using LDAR and LLP data

This study intercompared lightning data from LDAR and LLP systems in order to learn more about the spatial relationships between thunderstorm electrical discharges aloft and lightning strikes to the surface. The ultimate goal of the study is to provide information that can be used to improve the process of real-time detection and warning of lightning by weather forecasters who issue lightning advisories. The Lightning Detection and Ranging (LDAR) System provides data on electrical discharges from thunderstorms that includes cloud-ground flashes as well as lightning aloft (within cloud, cloud-to-cloud, and sometimes emanating from cloud to clear air outside or above cloud). The Lightning Location and Protection (LLP) system detects primarily ground strikes from lightning. Thunderstorms typically produce LDAR signals aloft prior to the first ground strike, so that knowledge of preferred positions of ground strikes relative to the LDAR data pattern from a thunderstorm could allow advance estimates of enhanced ground strike threat. Studies described in the report examine the position of LLP-detected ground strikes relative to the LDAR data pattern from the thunderstorms. The report also describes other potential approaches to the use of LDAR data in the detection and forecasting of lightning ground strikes.

Forbes, Gregory S.↗
NASA NTRS2006

Atmospheric Radiation Measurements Aerosol Intensive Operating Period: Comparison of Aerosol Scattering during Coordinated Flights

In May 2003, a Twin Otter airplane, equipped with instruments for making in situ measurements of aerosol optical properties, was deployed during the Atmospheric Radiation Measurements (ARM) Program s Aerosol Intensive Operational Period in Oklahoma. Several of the Twin Otter flights were flown in formation with an instrumented light aircraft (Cessna 172XP) that makes routine in situ aerosol profile flights over the site. This paper presents comparisons of measured scattering coefficients at 467 nm, 530 nm, and 675 nm between identical commercial nephelometers aboard each aircraft. Overall, the agreement between the two nephelometers decreases with longer wavelength. During the majority of the flights, the Twin Otter flew with a diffuser inlet while the Cessna had a 1 mm impactor, allowing for an estimation of the fine mode fraction aloft. The fine mode fraction aloft was then compared to the results of a ground-based nephelometer. Comparisons are also provided in which both nephelometers operated with identical 1 mm impactors. These scattering coefficient comparisons are favorable at the longer wavelengths (i.e., 530 nm and 675 nm), yet differed by approximately 30% at 467 nm. Mie scattering calculations were performed using size distribution measurements, made during the level flight legs. Results are also presented from Cadenza, a new continuous wave cavity ring-down (CW-CRD) instrument, which compared favorably (i.e., agreed within 2%) with data from other instruments aboard the Twin Otter. With this paper, we highlight the significant implications of coarse mode (larger than 1 mm) aerosol aloft with respect to aerosol optical properties.

Hallar, A. G.↗
NASA NTRS2012

Size Resolved Measurements of Springtime Aerosol Particles over the Northern South China Sea

Large sources of aerosol particles and their precursors are ubiquitous in East Asia. Such sources are known to impact the South China Sea (henceforth SCS), a sometimes heavily polluted region that has been suggested as particularly vulnerable to climate change. To help elucidate springtime aerosol transport into the SCS, an intensive study was performed on the remote Dongsha (aka Pratas) Islands Atoll in spring 2010. As part of this deployment, a Davis Rotating-drum Uniform size-cut Monitor (DRUM) cascade impactor was deployed to collect size-resolved aerosol samples at the surface that were analyzed by X-ray fluorescence for concentrations of selected elements. HYSPLIT backtrajectories indicated that the transport of aerosol observed at the surface at Dongsha was occurring primarily from regions generally to the north and east. This observation was consistent with the apparent persistence of pollution and dust aerosol, along with sea salt, in the ground-based dataset. In contrast to the sea-level observations, modeled aerosol transport suggested that the westerly flow aloft (w700 hPa) transported smoke-laden air toward the site from regions from the south and west. Measured aerosol optical depth at the site was highest during time periods of modeled heavy smoke loadings aloft. These periods did not coincide with elevated aerosol concentrations at the surface, although the model suggested sporadic mixing of this free-tropospheric aerosol to the surface over the SCS. A biomass burning signature was not clearly identified in the surface aerosol composition data, consistent with this aerosol type remaining primarily aloft and not mixing strongly to the surface during the study. Significant vertical wind shear in the region also supports the idea that different source regions lead to varying aerosol impacts in different vertical layers, and suggests the potential for considerable vertical inhomogeneity in the SCS aerosol environment.

South China Sea↗
NASA NTRS1970

Development of a test and flight engineering oriented language, phase 3

Based on an analysis of previously developed test oriented languages and a study of test language requirements, a high order language was designed to enable test and flight engineers to checkout and operate the proposed space shuttle and other NASA vehicles and experiments. The language is called ALOFT (a language oriented to flight engineering and testing). The language is described, its terminology is compared to similar terms in other test languages, and its features and utilization are discussed. The appendix provides the specifications for ALOFT.

Kamsler, W. F.↗
NASA NTRS1973

Summary of atmospheric data observations for 155 flight of MSFC/ABMA related aerospace vehicles

A summary of selected atmospheric conditions observed near launch time for 155 NASA-Marshall Space Flight Center and Army Ballistic Missile Agency related vehicles, launched primarilv from Cape Kennedy, Florida, between August 20, 1953, and November 16, 1963, is presented. Values of ambient pressure, temperature, relative humidity, ground winds, visual observations, density aloft, and wind/wind shear aloft are included. The extremes of these parameters are listed for each type of launch vehicle.

Johnson, D. L.↗
NASA NTRS1975

Vestibular side effects in the orbital stage of Skylab II and III missions

None of the six astronauts were motion sick when tested (on or after Mission Day 8) in the workshop under experimental conditions which elicited motion sickness preflight and postflight. Skylab III but not Skylab II astronauts experienced motion sickness under operational conditions aloft. There were individual differences in the severity of the symptoms and susceptibility to motion sickness persisted for three to five days. The discussion centers around the reasons for the greater susceptibility to motion sickness under operational than experimental conditions aloft and the implication of Skylab findings for future manned space missions.

Graybiel, A.↗
NASA NTRS1978

Mariner 9 television limb observations of dust and ice hazes on Mars

Results are presented for a statistical analysis of over 3000 Mariner 9 television reflectance profiles of the planetary limb of Mars for the period from the decaying phase of a global dust storm (southern summer) to southern winter solstice. It is shown that during the decaying phase of the storm, the dust is maintained aloft to high elevations by vertical mixing primarily in the equatorial zone, apparently by the direct or indirect action of the diurnal tide; the result is that the dust decay is much faster in high-latitude regions than near the equator. Significant dust remains aloft in Martian equatorial regions long after the major dust storms have subsided. At the top of the dusty atmosphere, a region exists where temperatures relax toward values expected for a dust-free CO2 atmosphere; this is therefore a region of convective overturning topped by thin condensation hazes resembling terrestrial noctilucent clouds, thereby showing occasionally gravity wave structures.

Anderson, E.↗
NASA NTRS1979

Motion sickness susceptibility during rotation at 30 rpm in free-fall parabolic flight

To make comparisons with experimental motion sickness susceptibility in Skylab missions, subjects were tested during free fall in parabolic flight and in ground-based simulation tests. They were rotated at 30 rpm in a rotating litter chair (RLC) with head fixed, head swiveling left-to-right, or with 90 degree forward and return head and body movements. Stressful accelerations similar to those in the Skylab RLC were generated only in the tests aloft, where subjects who made 'forward and return' movements (generating cross-coupled angular accelerations) were substantially more prone to motion sickness than those with either head fixed or head swiveling left-to-right. However, with head swiveling, susceptibility was slightly higher in the laboratory than aloft.

Graybiel, A.↗