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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Observations of the red auroral oxygen lines in nine comets

The digital sky-subtracted spectra of nine cometary nuclei are used to measure the 6300, 6363-A Auroral red doublet of the O I forbidden line, and in view of the confinement of the cometary oxygen lines to their nuclear source, a small but variable correction for NH2 blending in different comets is made. For seven of the comets measured, and under the assumption of H2O's exclusive role as the oxygen parent, the average Q(H2O)/Q(O I) ratio is about 20. This is in excellent accord with theory, and it is conjectured that the O I production rate can be used to scale the total cometary volatile loss in even faint, distant comets. The data obtained are consistent with heliocentric production rates that vary as power laws, with n values of 2.0 for 'gassy' comets and nearer to 5.0 for dusty ones. The comets with the greatest volatile mass-loss rates all were found to have dusty spectra.

Spinrad, H.↗
NASA NTRS1993

Bandwidth characteristics of multimedia data traffic on a local area network

Limited spacecraft communication links call for users to investigate the potential use of video compression and multimedia technologies to optimize bandwidth allocations. The objective was to determine the transmission characteristics of multimedia data - motion video, text or bitmap graphics, and files transmitted independently and simultaneously over an ethernet local area network. Commercial desktop video teleconferencing hardware and software and Intel's proprietary Digital Video Interactive (DVI) video compression algorithm were used, and typical task scenarios were selected. The transmission time, packet size, number of packets, and network utilization of the data were recorded. Each data type - compressed motion video, text and/or bitmapped graphics, and a compressed image file - was first transmitted independently and its characteristics recorded. The results showed that an average bandwidth of 7.4 kilobits per second (kbps) was used to transmit graphics; an average bandwidth of 86.8 kbps was used to transmit an 18.9-kilobyte (kB) image file; a bandwidth of 728.9 kbps was used to transmit compressed motion video at 15 frames per second (fps); and a bandwidth of 75.9 kbps was used to transmit compressed motion video at 1.5 fps. Average packet sizes were 933 bytes for graphics, 498.5 bytes for the image file, 345.8 bytes for motion video at 15 fps, and 341.9 bytes for motion video at 1.5 fps. Simultaneous transmission of multimedia data types was also characterized. The multimedia packets used transmission bandwidths of 341.4 kbps and 105.8kbps. Bandwidth utilization varied according to the frame rate (frames per second) setting for the transmission of motion video. Packet size did not vary significantly between the data types. When these characteristics are applied to Space Station Freedom (SSF), the packet sizes fall within the maximum specified by the Consultative Committee for Space Data Systems (CCSDS). The uplink of imagery to SSF may be performed at minimal frame rates and/or within seconds of delay, depending on the user's allocated bandwidth. Further research to identify the acceptable delay interval and its impact on human performance is required. Additional studies in network performance using various video compression algorithms and integrated multimedia techniques are needed to determine the optimal design approach for utilizing SSF's data communications system.

Chuang, Shery L.↗
NASA NTRS1994

VHF radar and rocket observations of equatorial spread F on Kwajalein

VHF radar data from the Summer 1990 Equatorial Spread F campaign on Kwajalein are presented. The Cornell 50 MHz portable radar interferometer (CUPRI) operated concurrently with the Altair UHF incoherent scatter radar throughout July and August and supported two sounding rocket flights on July 30 and August 2. This experiment provided the first opportunity to simultaneously diagnose equatorial spread F using the three prime experimental techniques: VHF/UHF coherent scatter, incoherent scatter, and in situ probe measurements of electric field and density fluctuations. The intensity of the coherent echoes observed was consistent with typical Jicamarca spread F observations, but chains of periodic, large-scale plasma upwellings were observed more often and for much longer durations on Kwajalein than have been seen over Peru. CUPRI also measured Doppler frequencies in one upwelling corresponding to 1200-m/s plasma drift velocities. This measurement agrees with recent observations of supersonic drift rates at the magnetic equator by spacecraft. Near the most active localized plasma upwellings, interferometer data reveal that the zonal drift rate of plasma irregularities can vary sharply in space, as one would expect for two-dimensional incompressible flow. We introduce a semiempirical model of the three-dimensional spectrum of F region irregularities that is consistent with the one-dimensional spectra of density fluctuations observed by sounding rockets and with the axial ratio of irregularities determined recently. Normalized to data from one of the rocket flights on Kwajalein, the model predicts the 3-m scattering cross-section measured by CUPRI to within a few decibels.

Hysell, D. L.↗
NASA NTRS1982

Deep Discharge Reconditioning and Shorted Storage of Batteries

The identification and measurement of hydrogen recombination in sealed nickel-cadium cells makes deep reconditioning on a battery basis safe and feasible. Deep reconditioning improves performance and increases life of nickel-cadium batteries in geosynchronous orbit applications. The hydrogen mechanism and supporting data are presented. Parameter cell design experiments are described which led to the definition of nickel-cadium cells capable of high rate overdischarge without detriment to specific energy. Nickel-cadium calls of identical optimum design were successfully cycled for 7 seasons in simulation of geosynchronous orbit at 75 percent depth-of-discharge with extensive midseason and end-of-season overdischarge at rates varying from C/20 to C/4. Destructive physical analysis and cyclin data indicated no deterioration or the development of dangerous pressures as a result of the cycling with overdischarge.

Ritterman, P. F.↗
NASA NTRS1993

Experimental studies of an ECR plasma thruster

The Electron Cyclotron Resonance (ECR) thruster is a proposed electrodeless space electric propulsion device with interesting and little understood physics. A laboratory ECR thruster was run in a vacuum tank at pressures in the 10 exp -5 torr range using 2.12 GHz microwave beam and Ar gas propellant. Movable diagnostic probes (a Faraday cup and a gridded energy analyzer) measured plasma characteristics as propellant gas flow rate and input microwave power level were varied. Ion energy and flux data were used to calculate I(sp), propulsive efficiency, and thrust. The ion flux profiles show an unexpected depression on the thruster axis for low tank pressures that disappears as the tank pressure increases. Ion energies decrease as the flow rate and pressure increase, but the microwave power level affects the energy only negligibly. The calculated propulsion parameters demonstrate that the efficiency of the laboratory device is low, and that tank pressure greatly changes the performance.

Kaufman, D. A.↗
NASA NTRSDate not supplied

The Effects of Plasma Application on Radish Seeds with Implications for Space Crop Production

In extended space missions, the astronaut diet will consist mostly of prepackaged foods. This could result in nutritional deficiencies due to the gradual breakdown of certain vitamins. To address this deficiency, fresh produce must be grown from seed during spaceflight. Stored seeds, however, can be vulnerable to microbial contamination which could jeopardize plant health and crop food safety. To alleviate this concern, the current practice is to sanitize seeds on the ground before spaceflight to the International Space Station (ISS). Methods of seed sanitization include alcohol soaking and chlorine gas fumigation, which have harmful effects on the environment and human health. Plasma application is a new sanitization approach that avoids these negative side effects while potentially elevating germination rate and improving growth rate; yet plasma application requires specific exposure time, power, and pressure to achieve these benefits. In the present study, Raphanus sativus ‘Cherry Belle’ radish seeds were exposed to either low pressure (Diener) plasma or atmospheric pressure plasma for varying increments of time (30s-1200s). Data collected includes immediate germination rate (viability) and microbial log reduction. Additionally, seeds were stored for later germination rate testing. Microbial assay controls have highlighted variability in initial microbial load between individual seeds, and further work is being performed to determine the standard microbial load of an untreated seed. In some samples, a negative log reduction was observed after plasma treatment encouraging further study to determine if the plasma is perforating the seed coat and releasing endophytic microbes. Treatment with Diener plasma shows promising microbial log reduction, but lower viability. In contrast, treatment with atmospheric pressure plasma offers high viability, but poor microbial log reduction. Further study will aim at determining whether plasma treatment is effective at not only sanitization, but sterilization. This research was funded by a NASA grant at the Kennedy Space Center.

Plasma↗
NASA NTRSDate not supplied

The Effects of Plasma Application on Radish Seeds with Implications for Space Crop Production

In extended space missions, the astronaut diet will consist mostly of prepackaged foods. This could result in nutritional deficiencies due to the gradual breakdown of certain vitamins. To address this deficiency, fresh produce must be grown from seed during spaceflight. Stored seeds, however, can be vulnerable to microbial contamination which could jeopardize plant health and crop food safety. To alleviate this concern, the current practice is to sanitize seeds on the ground before spaceflight to the International Space Station (ISS). Methods of seed sanitization include alcohol soaking and chlorine gas fumigation, which have harmful effects on the environment and human health. Plasma application is a new sanitization approach that avoids these negative side effects while potentially elevating germination rate and improving growth rate; yet plasma application requires specific exposure time, power, and pressure to achieve these benefits. In the present study, Raphanus sativus ‘Cherry Belle’ radish seeds were exposed to either low pressure (Diener) plasma or atmospheric pressure plasma for varying increments of time (30s-1200s). Data collected includes immediate germination rate (viability) and microbial log reduction. Additionally, seeds were stored for later germination rate testing. Microbial assay controls have highlighted variability in initial microbial load between individual seeds, and further work is being performed to determine the standard microbial load of an untreated seed. In some samples, a negative log reduction was observed after plasma treatment encouraging further study to determine if the plasma is perforating the seed coat and releasing endophytic microbes. Treatment with Diener plasma shows promising microbial log reduction, but lower viability. In contrast, treatment with atmospheric pressure plasma offers high viability, but poor microbial log reduction. Further study will aim at determining whether plasma treatment is effective at not only sanitization, but sterilization. This research was funded by a NASA grant at the Kennedy Space Center.

Space Crop Production↗
NASA NTRSDate not supplied

TO252: Parabolic Flight Demonstration of Fluid Dispensing Tube Performance Limits for Drop Delivery

Ring Shear Drop (RSD) ISS flight hardware failed to pin sample fluid drops between two rings, likely due to dynamic instability inherent to the dispensing tube (D-Tube) design. The first parabolic flight tested 5 D-tube tip designs with two bounding surface tension fluids, enabling an engineering design decision. D-tube Tip Cage Design was selected based on the November 2020 parabolic flight test data. Flight Operations Program (FOP) approved a reflight proposal to include 2 parabolic flight days during the April/May 2021 campaign with following objectives: • Validate ISS hardware flight design with actual flight fluids (test as you fly), demonstrating the ability to deliver 1” fluid drops in near-microgravity conditions. • Demonstrate pinning of 1” flight fluid drops: a secondary pinning ring is planned to be installed in the parabolic flight hardware to meet this objective. Fluid flow rates will also be varied as needed and as possible. • Provide data to validate computational models used to guide ISS operational deployment decisions and demonstrate the viability of the redesigned hardware to accommodate a range of future flight investigations. This presentation introduces highlights and lessons learned during this recent flight campaign for discussion in the Flight Opportunities Program Panel, “Leveraging Suborbital Flight Tests to Advance Science and Technology."

Sridhar Gorti↗
NASA NTRS1978

Evaporator film coefficients of grooved heat pipes

The heat transfer rate in the meniscus attachment region of a grooved heat pipe evaporator is studied theoretically. The analysis shows that the evaporation takes place mainly in the region where the liquid changes its shape sharply. However, comparisons with available heat transfer data indicate that the heat transfer rate in the meniscus varying region is substantially reduced probably due to groove wall surface roughness.

Kamotani, Y.↗
NASA NTRS1987

Giving you the business - Competitive pricing of selected Predicasts' databases

The pricing policies of different data-base services offering Predicast data bases are examined from a user perspective. The services carrying these data bases are listed; the problems introduced by varying exchange rates and seemingly idiosyncratic price structures are discussed; and numerous specific examples are given.

Jack, Robert F.↗
NASA NTRS1988

Electrical measurements over active thunderstorms

During the summer of 1986, the air conductivity and the vertical electric field were measured over active thunderstorms from a high altitude U-2 airplane. The conductivity at 20 km remained relatively steady above storms with variations less than + or - 15 percent while vertical electric fields in excess of 5 kV/m were regularly observed. Estimates of the storm generator current and the C.T.R. Wilson (i.e., conduction) current can be obtained using the current densities derived from the conductivity and field measurements and integrated over area. Upward flowing currents of 0.05 to 7.7 A were observed with an average of 2.2 A. More importantly, the U-2 data show that the storm current varies linearly with flash rate, therefore, the average charge transfer per discharge should be independent of storm development or activity.

Blakeslee, Richard J.↗
NASA NTRS1976

The evolution of the clear air convective layer revealed by surface-based remote sensors

Results are reported for simultaneous observations of the growth and decay of the clear-air convective mixing layer near a coastline, which were made with an FM-CW radar, a high-power narrow-beam S-band radar, and an acoustic echo sounder. The main purpose of this study was to determine the relationship between the rise rate of the convective depth and the lapse rate of temperature, particularly in the morning hours. The results indicate that the three remote sensors can provide excellent mutually supporting data on the convective depth. It is found that this depth is well behaved during the day and that its rise rate varies roughly linearly with the inverse square root of the temperature lapse rate during the morning. The data suggest that some models concerning the rise rate require modification, since these models imply that the surface heat flux would have to be unreasonably large to produce the observed relationship.

Noonkester, V. R.↗
NASA NTRS1991

Computer-based video digitizer analysis of surface extension in maize roots: kinetics of growth rate changes during gravitropism

We used a video digitizer system to measure surface extension and curvature in gravistimulated primary roots of maize (Zea mays L.). Downward curvature began about 25 +/- 7 min after gravistimulation and resulted from a combination of enhanced growth along the upper surface and reduced growth along the lower surface relative to growth in vertically oriented controls. The roots curved at a rate of 1.4 +/- 0.5 degrees min-1 but the pattern of curvature varied somewhat. In about 35% of the samples the roots curved steadily downward and the rate of curvature slowed as the root neared 90 degrees. A final angle of about 90 degrees was reached 110 +/- 35 min after the start of gravistimulation. In about 65% of the samples there was a period of backward curvature (partial reversal of curvature) during the response. In some cases (about 15% of those showing a period of reverse bending) this period of backward curvature occurred before the root reached 90 degrees. Following transient backward curvature, downward curvature resumed and the root approached a final angle of about 90 degrees. In about 65% of the roots showing a period of reverse curvature, the roots curved steadily past the vertical, reaching maximum curvature about 205 +/- 65 min after gravistimulation. The direction of curvature then reversed back toward the vertical. After one or two oscillations about the vertical the roots obtained a vertical orientation and the distribution of growth within the root tip became the same as that prior to gravistimulation. The period of transient backward curvature coincided with and was evidently caused by enhancement of growth along the concave and inhibition of growth along the convex side of the curve, a pattern opposite to that prevailing in the earlier stages of downward curvature. There were periods during the gravitropic response when the normally unimodal growth-rate distribution within the elongation zone became bimodal with two peaks of rapid elongation separated by a region of reduced elongation rate. This occurred at different times on the convex and concave sides of the graviresponding root. During the period of steady downward curvature the elongation zone along the convex side extended farther toward the tip than in the vertical control. During the period of reduced rate of curvature, the zone of elongation extended farther toward the tip along the concave side of the root. The data show that the gravitropic response pattern varies with time and involves changes in localized elongation rates as well as changes in the length and position of the elongation zone. Models of root gravitropic curvature based on simple unimodal inhibition of growth along the lower side cannot account for these complex growth patterns.

NASA Discipline Plant Biology↗
NASA NTRS1995

A flying qualities study of longitudinal long-term dynamics of hypersonic planes

The NASA Dryden Flight Research Center and the Technical University of Munich are cooperating in a research program to assess the impact of unstable long-term dynamics on the flying qualities of planes in hypersonic flight. These flying qualities issues are being investigated with a dedicated flight simulator for hypersonic vehicles located at NASA Dryden. Several NASA research pilots have flown the simulator through well-defined steady-level turns with varying phugoid and height mode instabilities. Th data collected include pilot ratings and comments, performance measurements, and pilot workload measurements. The results presented in this paper include design guidelines for height and phugoid mode instabilities, an evaluation of the tapping method used to measure pilot workload, a discussion of techniques developed by the pilots to control large instabilities, and a discussion of how flying qualities of unstable long-term dynamics influence control power design requirements.

Cox, T.↗
NASA NTRS1995

A Flying Qualities Study of Longitudinal Long-Term Dynamics of Hypersonic Planes

The NASA Dryden Flight Research Center and the Technical University of Munich are cooperating in a research program to assess the impact of unstable long-term dynamics on the flying qualities of planes in hypersonic flight. These flying qualities issues are being investigated with a dedicated flight simulator for hypersonic vehicles located at NASA Dryden. Several NASA research pilots have flown the simulator through well defined steady-level turns with varying phugoid and height mode instabilities. The data collected include Pilot ratings and comments, performance measurements, and Pilot workload measurements. The results presented in this paper include design guidelines for height and Phugoid mode instabilities, an evaluation of the tapping method used to measure pilot workload, a discussion of techniques developed by the pilots to control large instabilities, and a discussion of how flying qualities of unstable long-term dynamics influence control Power design requirements.

Cox, Timothy H.↗
NASA NTRS2002

Surface Crystallization of Cloud Droplets: Implications for Climate Change and Ozone Depletion

The process of supercooled liquid water crystallization into ice is still not well understood. Current experimental data on homogeneous freezing rates of ice nucleation in supercooled water droplets show considerable scatter. For example, at -33 C, the reported freezing nucleation rates vary by as much as 5 orders of magnitude, which is well outside the range of measurement uncertainties. Until now, experimental data on the freezing of supercooled water has been analyzed under the assumption that nucleation of ice took place in the interior volume of a water droplet. Here, the same data is reanalyzed assuming that the nucleation occurred "pseudoheterogeneously" at the air (or oil)-liquid water interface of the droplet. Our analysis suggest that the scatter in the nucleation data can be explained by two main factors. First, the current assumption that nucleation occurs solely inside the volume of a water droplet is incorrect. Second, because the nucleation process most likely occurs on the surface, the rates of nuclei formation could differ vastly when oil or air interfaces are involved. Our results suggest that ice freezing in clouds may initiate on droplet surfaces and such a process can allow for low amounts of liquid water (approx. 0.002 g per cubic meters) to remain supercooled down to -40 C as observed in the atmosphere.

Tabazadeh, A.↗
NASA NTRS2003

Propagation Measurement and Analysis

The future NASA planned spacecraft networks involving multiple non-GEO satellites consisting of variable nodes, altitudes, and transmission rates are shown. The nature and requirements of the spacecraft networks can vary broadly depending on specific design criteria and intended missions. The networks have flexible spacecraft configuration, data rates, and constellation.

Ugweje, Okechukwu C.↗
NASA NTRS1977

Solar flare activity - Evidence for large-scale changes in the past

An analysis of radar and photographic meteor data and of spacecraft meteoroid-penetration data indicates that there probably has not been a large increase in meteoroid impact rates in the last 10,000 yr. The solar-flare tracks observed in the glass linings of meteoroid impact pits on lunar rock 15205 are therefore reanalyzed assuming a meteoroid flux that is constant in time. Based on this assumption, the data suggest that the production rate of Fe-group solar-flare tracks may have varied by as much as a factor of 50 on a time scale of about 10,000 yr. No independently obtained data are known to require conflict with this interpretation. Confidence in this conclusion is somewhat qualified by the experimental and analytical uncertainties involved, but the conclusion nevertheless remains the present 'best' explanation for the observed data trends.

Zook, H. A.↗