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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

An earth outgoing longwave radiation climate model. II - Radiation with clouds included

The model of the outgoing longwave radiation (OLWR) of Yang et al. (1987) is modified by accounting for the presence of clouds and their influence on OLWR. Cloud top temperature was adjusted so that the calculation agreed with NOAA scanning radiometer measurements. Cloudy sky cases were calculated for global average, zonal average, and worldwide distributed cases. The results were found to agree well with satellite observations.

Yang, Shi-Keng↗
NASA NTRS1989

Bubble behaviors in a slowly rotating helium dewar in a Gravity Probe-B spacecraft experiment

Potential problems for the Gravity Probe-B (GP-B) spacecraft design requirements and the operational considerations could arise because of the free surface configurations between liquid helium and helium vapor in the rotating dewar. This free surface is present in the partially filled liquid helium dewar. The liquid helium in the dewar is depleted as it is consumed as propellant for the spacecraft. In this study, the doughnut-shaped helium bubble equilibrium profiles in the rotating dewar have been numerically calculated. These calculations were performed under the conditions imposed during the period of the GP-B experiment instrument calibration (gyro spinup period) and also during the normal operational stages of the GP-B spacecraft.

Hung, R. J.↗
NASA NTRS1989

Comets in the space age

The historical development of the study of the nature of comets and their origin is discussed, emphasizing the use of aerospace technology in cometary science. The use of satellites to study the Comet Kohoutek 1973 XII, advances between Kohoutek and P/Halley, and studies of P/Halley during its 1986 return are examined. Consideration is given to data from ground, air, and space sensors, and from the Giotto and Vega spacecraft missions. Also, the physical structure of the nucleus of Comet Halley is described.

Whipple, Fred L.↗
NASA NTRS1989

The infrared emission bands. III - Southern IRAS sources

Airborne 5-8-micron spectra of southern IRAS sources are presented which display the strong PAH emission features. The sources studied include those in a previous paper (Cohen et al, 1986) and NGC 6302, HR 4049, and CPD -56 deg 8032. A good correlation is found between the intensity ratio of the 7.7-micron feature relative to the FIR dust continuum and nebular C/O ratio, supporting a carbonaceous carrier for these emission features. In addition, a weak PAH band is detected near 5.2 microns in several sources.

Cohen, Martin↗
NASA NTRS1989

Discovery of a cool expanding shell at -1200 kilometers per second around V471 Tauri

High-resolution IUE spectra of V471 Tauri reveal the presence of a very-high-velocity cool expanding gas in the line of sight to the binary system with an expansion velocity of -1200 km/s. The summed strength of the coadded absorption is 125 mA + or - 25 mA, with FWHM = 30 km/s. It is suggested that the observed absorption may be related to the narrow coadded absorption at -590 km/s noted by Bruhweiler and Sion (1966). The large expansion velocity suggests a possible association with an ancient nova outburst.

Sion, Edward M.↗
NASA NTRS1989

Finite-element grid improvement by minimization of stiffness matrix trace

A new and simple method of finite-element grid improvement is presented. The objective is to improve the accuracy of the analysis. The procedure is based on a minimization of the trace of the stiffness matrix. For a broad class of problems this minimization is seen to be equivalent to minimizing the potential energy. The method is illustrated with the classical tapered bar problem examined earlier by Prager and Masur. Identical results are obtained.

Kittur, Madan G.↗
NASA NTRS1989

Infrared studies of hydrocarbons on Jupiter

Measurements of ethane and ethylene emission lines on Jupiter were made using a dual CO2 laser heterodyne spectrometer. Retrieved abundances of these products of methane photolysis in the Jovian stratosphere were used to test existing photochemical models and to investigate a localized "hot spot" in the northern auroral region.

Kostiuk, Theodor↗
NASA NTRS1989

A search for p-mode oscillations of Jupiter - Serendipitous observations of nonacoustic thermal wave structure

Frequencies for the p-mode oscillations of Jupiter have been determined, and infrared brightness temperature fluctuations are used to search for the modes. Measurements of the infrared intensity of the Jovian disk were obtained in a broad bandwidth using a 20-element linear array. No p-mode oscillations were observed at the 0.07-K level in the 8-13-micron brightness temperature. The results suggest that Jovian p modes are not likely to have observable amplitudes. A prominent nonacoustic wave-like structure in the 8-13-micron brightness temperature is found both at 20 deg N and at the equator.

Deming, Drake↗
NASA NTRS1989

Numerical simulations of an isolated microbursts. II - Sensitivity experiments

A time-dependent, high-resolution, axisymmetric numerical model simulating isolated and stationary microbursts is used to evaluate the sensitivity of microbursts to the environment and other factors. It is found that microbursts intensity is sensitive to ther vertical distirbution of ambient temperature and humidity, the horiontal width of the precipitation shaft or downdraft, the magnitutde of precipitation loading, and the type and duration of precipitation. Scenarios for the generation of an intense microburst and the possible applications of the results are examined.

Proctor, Fred H.↗
NASA NTRS1989

Axisymmetric bubble profiles in a slowly rotating helium dewar under low and microgravity environments

The Gravity Probe-B (GP-B) Spacecraft is designed to test the General Theory of Relativity through long-term monitoring the precession of a set of gyros in free-fall around the earth. The potential problems for GP-B Spacecraft design requirements could be due to asymmetry in the static liquid helium distribution, or to perturbations in free surface which is present in the partially-filled liquid helium dewar. In this study, doughnut-shaped helium bubble equilibrium profiles in rotating dewar, under the conditions during the period of GP-B experiment instrument calibration and also during the period of normal operation stages of GP-B Spacecraft, have been numerically calculated. For academic interest, the range of coverage has been extended beyond the conditions assigned by the GP-B Spacecraft experiment.

Hung, R. J.↗
NASA NTRS1988

Hypersonic aerodynamics at North Carolina State University

Hypersonic Aerodynamics has attracted outstanding graduate students and faculty at NCSU. It has grown to 6 faculty and 32 graduate students for fall, 1988. A significant feature of the program is that students and faculty spend time at government laboratories which currently include NASA Langley Research Center, Naval Surface Warfare Center at Silver Spring, and the Wright Aeronautical Laboratories. Research projects include analysis, computational and experimental aerodynamics. The combined program produces graduates with the background needed to perform aerodynamics investigations of hypersonic aircraft and spacecraft. The research performed helps advance the state of the art as well as assist government laboratories in meeting their goals.

Dejarnette, Fred R.↗
NASA NTRS1989

Spectral distortions of the cosmic microwave background

Recent experiments indicate that the spectrum of the cosmic microwave background deviates from a pure blackbody; here, spectral distortions produced by cosmic dust are considered. The main result is that cosmic dust in conjunction with an injected radiation field (perhaps produced by an early generation of very massive stars) can explain the observed spectral distortions without violating existing cosmological constraints. In addition, it is shown that Compton y-distortions can also explain the observed spectral shape, but the energetic requirements are more severe.

Adams, Fred C.↗
NASA NTRS1989

A relationship between peak temperature drop and velocity differential in a microburst

Results from numerical microburst simulations using the Terminal Area Simulation System (Proctor, 1987) are used to develop a relationship between wind velocity differential and peak temperature drop. The numerical model and the relationships derived from the model are described. The relationship between peak temperature drop and differential wind velocity is shown to be valid during microburst development, for all precipitation shaft intensities and diameters. It is found that the relationship is not valid for low-reflectivity microburst events or in the presence of ground-based stable layers. The use of the relationship in IR wind shear detection systems is considered.

Proctor, Fred H.↗
NASA NTRS1989

A mesoscale numerical simulation of an index for use in the forecasting of the potential severity of wet microbursts

This paper demonstrates the feasibility of using the wet microburst potential intensity index developed by Proctor (1989) for predicting the onset of a wet microburst. After describing the index and the principles involved in its derivation, the version 4.0 of the Mesoscale Atmospheric Simulation System (MASS) model described by Karyampudi et al. (1988) was used to illustrate how the index would perform as a forecast product. An analysis is presented of the use of the microburst potential intensity index in the numerical simulation of the DFR aircraft accident on August 2, 1985 in a downburst environment.

Zack, John W.↗
NASA NTRS1990

Two-Phase Accumulator

Two-phase accumulator maintains pressure and temperature in thermal-bus system within predetermined range during variations in heat load on system. Stores liquid and vapor ammonia. Exchanges liquid ammonia with condenser to adjust level of liquid in condenser. Prototype has capacity of 13 gallons (49 liters). Simple and highly reliable. Responds quickly, restoring pressure and temperature to proper values within minutes. Low in cost and requires little further development. Used to dispose of waste heat, such as that from electronic equipment or power-plant.

Kalb, Charles E.↗
NASA NTRS1990

Modification Of Gear Teeth To Reduce Vibrations

Computer simulations yield data useful in designing for low noise. Effects of modifications in shape of gear teeth upon static transmission error and dynamic loading of gears now analyzed systematically. Design curves generated by conducting numerical simulations of dynamic effects at successive incremental modifications of gear systems operated at various applied loads. Modifications that result in minimum dynamic effect determined from design curves.

Townsend, Dennis P.↗