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Results for “thermal pressure”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

An evaluation of reaction wheel emitted vibrations for space telescope

Emitted forces and moments characteristics of the Space Telescope Reaction Wheel Assembly (ST RWA) were measured under room temperature and pressure, thermal extremes, and vibratory conditions. The RWA/Emitted Vibration Measurement Fixture was calibrated statically and dynamically, and background noise was measured with ST RWA not operating. A base line set of forces and moments of the ST RWA along and about three mutually perpendicular axes were recorded at room ambient. The temperature vibration sensitivites shown are those which were concluded to be a function of rotor unbalance changes and not associated with either spin motor nor rotor electronic changes.

Source record↗
NASA NTRS1979

The Get Away Special Program

The paper deals with the Get Away Special (GAS) Program which was initiated on the realization that not every Space Shuttle mission would make full use of the volume and weight capability of the Shuttle system. Currently, the GAS Program incorporates 158 domestic and foreign users who have reserved 270 spaces. Not all users and not all experiments are expected to meet the objective of processing to prime experiments for Shuttle. Each experiment will be worthy in its own right and each user will benefit to the limit of his ability and involvement. The structure and the mounting system of the GAS container are described, along with its pressure, thermal, and electronic characteristics. Safety philosophy and requirements are noted, and possible options to the standard contained are discussed.

Ott, E. J.↗
NASA NTRS1979

Future planetary probes for Jupiter and Saturn

The paper describes a study conducted to identify the technology developments that would allow deep atmospheric investigations of Jupiter and Saturn to proceed beyond currently planned investigation of the upper atmosphere. The study considered a deep probe mission that would provide the capability to scientifically examine planetary atmospheres to the 1000-bar level and 1400-K level. The major conclusions of the study are that (1) a probe designed for Jupiter can be used with minor changes for Saturn, (2) new science instrument technology developments are required, and (3) the only new technology developments required in the engineering subsystem are high pressure thermal insulation materials and advanced data processing techniques.

Butts, A. J.↗
NASA NTRS1979

HEAO 1 scanning modulation collimator discovery of an extended X-ray source at Cygnus A

The HEAO 1 modulation-collimator data associate the X-ray emission from the Cygnus A region (4U 1957 + 40) with a small area including the radio galaxy. The source appears to be extended, with a size of about 2 arcmin; it may have a complex geometry. Any point-source component must have a flux no greater than 1.3 UFU. A lower limit of 1 microgauss is placed on the magnetic field in the radio lobes, based on the upper limit on the X-ray flux due to inverse Compton scattering of radio electrons on the 2.7-K microwave background radiation. The X-ray emission is more likely due to driven accretion of the intercluster gas onto the giant cD radio galaxy. Therefore this source appears to be similar to the Virgo and Perseus clusters. The density derived for the X-ray-emitting gas is too small for its thermal pressure to confine the radio source.

Fabbiano, G.↗
NASA NTRS1979

On the connection of interplanetary shock wave parameters and energetic storm particle events

A series of energetic storm particle (ESP) events is investigated on the basis of observations of energetic solar protons by IMPs IV and V between 1967 and 1972. The total number and energy of particles associated with 20 ESP events are analyzed in connection with several plasma parameters at the shock surface; i.e., magnetic and thermal pressure, magnetic field and plasma mass flux. Correlation is established between the total energy of ESPs in the energy range of 1-80 MeV and the jump in the total pressure. It is pointed out that the amount of shock energy converted to the acceleration of ESP particles is not negligible and could, in principle, contribute to the deceleration of the shock wave.

Gombosi, T.↗
NASA NTRS1979

Radioisotope thermoelectric generator cooling in the Shuttle bay

The paper describes a Shuttle-integrated radioisotope thermoelectric generator (RTG) that consists primarily of a pump package and plumbing connected directly to the Shuttle payload heat exchanger. The RTG utilizes on-board water evaporative cooling capability, which is normally used for ascent, entry, and for supplementing the radiators. Attention is given to the RTG cooling concepts which include: (1) an active thermal cooling system (ATCS), where two Freon-21 loops operate simultaneously to transport heat from the Orbiter subsystem and payloads through liquid-to-liquid heat exchangers and pin-fin coldplates to four heat sinks, and (2) an atmosphere revitalization system (ARS) which provides for thermal, pressure, and contaminate control of the crew cabin and its equipment. The use of a payload heat exchanger to reduce weight, cost and complexity associated with an independent cooling system was investigated in detail.

Stimpson, L. D.↗
NASA NTRS1980

Mass loss from warm giants: Magnetic effects

Among warm giant stars, rapid mass loss sets in along a well defined velocity dividing line (VDL). Hot corona also disappear close to the VDL and thermal pressure cannot drive the observed rapid mass loss in these stars. The VDL may be associated with magnetic fields changing from closed to open. Such a change is consistent with the lack of X-rays from late-type giants. A magnetic transition locus based on Pneuman's work on helmet streamer stability agrees well with the empirical VDL. The change from closed to open fields not only makes rapid mass loss possible, but also contributes to energizing the mass loss in the form of discrete bubbles.

Mullan, D. J.↗
NASA NTRS1980

The retention of hot gas in elliptical galaxies

The X-ray emission is interpreted from the fast-moving elliptical galaxy M86 (Forman et al. 1979) as evidence for the accumulation of an extensive gaseous envelope. The gas within this envelope is relatively hot, yet has until now been confined to the galaxy by the thermal pressure of the outer atmosphere of the Virgo cluster. The ram pressure of the intracluster gas in the cluster core is now stripping this envelope away. It is suggested that significant quantities of hot gas may be found in many elliptical galaxies.

Fabian, A. C.↗
NASA NTRS1983

Study of advanced rotary combustion engines for commuter aircraft

Performance, weight, size, and maintenance data for advanced rotary aircraft engines suitable for comparative commuter aircraft system evaluation studies of alternate engine candidates are provided. These are turbocharged, turbocompounded, direct injected, stratified charge rotary engines. Hypothetical engines were defined (an RC4-74 at 895 kW and an RC6-87 at 1490 kW) based on the technologies and design approaches used in the highly advanced engine of a study of advanced general aviation rotary engines. The data covers the size range of shaft power from 597 kW (800 hp) to 1865 kW (2500 hp) and is in the form of drawings, tables, curves and written text. These include data on internal geometry and configuration, installation information, turbocharging and turbocompounding arrangements, design features and technologies, engine cooling, fuels, scaling for weight size BSFC and heat rejection for varying horsepower, engine operating and performance data, and TBO and maintenance requirements. The basic combustion system was developed and demonstrated; however the projected power densities and performance efficiencies require increases in engine internal pressures, thermal loading, and rotative speed.

Berkowitz, M.↗
NASA NTRS1983

Global characteristics of magnetic flux ropes in the Venus ionosphere

An examination is undertaken of global characteristics of Venus ionosphere magnetic flux ropes, whose maximum spatial occurrence at 165-km altitude occupies more than half of the ionospheric volume. Ropes above 200 km altitude in the low zenith angle regions appear to have quasi-horizontal orientations, while those below that altitude tend to be quasi-vertical. High zenith angle cases tend to be horizontal above 300 km, and randomly oriented below that altitude. Ropes may be more tightly 'twisted' at low than at high altitudes, especially in the low zenith angle regions. Rope field strengths are highest near the altitudes where their occurrence is greatest, and scale with the square root of the ambient thermal pressure. The global polarities of flux rope field-aligned currents seem to be random and do not support a steady, nonturbulent global formation mechanism.

Elphic, R. C.↗
NASA NTRS1984

On the theory of cosmic-ray-mediated shocks with variable compression ratio

Cosmic-ray-mediated shocks may accelerate enough cosmic rays to high enough energies that they escape the shock, carrying an appreciable amount of energy before being convected to downstream infinity. Under such conditions, it is noted, the overall compression ratio cannot be determined from the conservation equations as in conventional hydrodynamic treatments, and the standard equations for shock acceleration admit arbitrarily high compression ratios. A procedure is outlined for obtaining the structure of high Mach number, cosmic-ray-mediated shocks, including their overall compresion ratio, around a low Mach number viscous subshock. Analytic solutions are obtained by quardrature for an energy-dependent diffusion coefficient in the limit of extreme sensitivity to energy, which, unlike previous solutions, include the finite thermal pressure of the preshock gas.

Eichler, D.↗
NASA NTRS1985

Space Shuttle Main Engine nozzle thermal protection system

Two of the three Space Shuttle Main Engine (SSME) nozzles are exposed to significant reentry aeroheating loads. To ensure reusability of the Nozzle Assembly, the nozzle primary structure must not exceed specific temperature limits. Due to the thermal, pressure, and dynamic flexing of the nozzle during a mission cycle, an appropriate insulating system must have significant flexibility. Recent missions have demonstrated nozzle reentry aeroheating rates and heat loads much higher than predictions, higher than the capability of the original insulating system. A new insulating system has been developed using similar materials in an aerodynamically 'smooth' shape to both reduce the incoming heating and increase radiation cooling.

Nordlund, R. M.↗
NASA NTRS1985

An atlas of objectively analyzed atmospheric cross sections, 1973-1980

Atmospheric variability over time scales greater than one month is conceptually simplified and readily recognized from vertical cross-sections of zonal-monthly mean data. The reduction to two dimensions, latitude and height, explicitly eliminates all zonal waves but implicity retains their effects on the thermal-pressure fields and the dynamically related zonal wind fields. This atlas contains 96 examples, spanning all latitudes in both the northern and southern hemispheres and two decades in pressure, from 1000 to 10 mb. Four analyses, representing each month from January 1973 through December 1980, depicts the potential virtual temperature, the observed zonal wind velocity, the virtual temperature and the geostrophic zonal wind velocity. Each variable is contoured at a close interval to facilitate visual estimates of stability and vorticity via their gradients. The analyses are generated and contoured by objective computer methods from just one data source: in situ measurements from the conventional rawin-radiosonde system. Although the analyses are independently made at constant pressure levels (the mandatory levels) the cross-sections are drawn with geopotential height as the ordinate. With this ordinate one can observe the seasonal expansion and contraction of the earth's atmosphere, especially that of the polar stratosphere. Also, the quasi-biannual cycle can be identified and studied directly from successive cross-sections.

Goodman, J.↗
NASA NTRS1985

The photospheric magnetic field of the dM3.5e flare star AD Leonis

A high-resolution infrared spectrum of the dM3.5e flare star AD Leo, obtained with the Kitt Peak 4 m Fourier Transform Spectrometer, clearly shows the presence of strong magnetic fields. Five absorption lines in the 4400-4600 per cm region have been modeled, and it is inferred that 73 percent + or - 6 percent of the surface of AD Leo is covered by active regions outside of dark spots containing a mean field strength of 3800 + or - 260 G. If these active regions are brighter than the quiet photosphere, the surface filling factor will be somewhat smaller. Since simultaneous H-alpha observations exhibited no evidence of flares, the observations probably represent the quiescent magnetic flux level. The inferred field strength is consistent with equipartition of magnetic and thermal pressures in the photosphere and is similar to values derived using the scaling laws of Golub. The large observed filling factor is consistent with efficient dynamo generation of magnetic flux in this rapidly rotating star.

Saar, S. H.↗
NASA NTRS1986

The detection of distant cooling flows and the formation of dark matter

Cooling flows involving substantial mass inflow rates appear to be common in many nearby rich and poor clusters and in isolated galaxies. The extensive optical and ultraviolet filaments produced by the thermal instability of large flows are detectable out to redshifts greater than 1. It is proposed that this may explain the extended optical line emission reported in, and around, many distant radio galaxies, narrow-line quasars, and even nearby normal and active galaxies. An important diagnostic to distinguish cooling flows from other possible origins of emission line filaments is the presence of extensive regions at high thermal pressure. Other evidence for distant cooling flows and the resultant star formation is further discussed, together with the implications of cooling flow initial-mass functions for galaxy formation and the nature of 'dark' matter.

Fabian, A. C.↗
NASA NTRS1986

Cool interstellar matter in early-type galaxies

IRAS fluxes of early-type galaxies have been examined. From studying a magnitude-limited sample, it seems that although the statistics are poor, perhaps a third of these objects and possibly even more have an appreciable amount of dust. In general, the infrared emission is strongest at 100 microns, and quite often the far-infrared luminosity of an early-type galaxy can be well in excess of 10 to the 8th solar luminosities. The data are most easily understood if the infrared results from dust reprocessing of starlight. Within 3 kpc of the center of an early-type galaxy, there may be more cold matter than hot gas; recent models that the interstellar media of these objects are composed primarily of hot gas appear to be oversimplifications. The X-ray data do indicate that the thermal pressure in the early-type galaxies often is sufficiently high that in view of the expected low temperatures of their interstellar clouds, it can be speculated that the cold material that is present may be forming low-mass stars.

Jura, M.↗
NASA NTRS1986

Solar cycle variations in the solar wind

The solar cycle variations of various solar wind parameters are reviewed. It is shown that there is a gradual decrease in the duration of high-speed streams from the declining phase of solar cycle 20 through the ascending phase of cycle 21 and a corresponding decrease in the annual average of the proton speed toward solar maximum. Beta, the ratio of the proton thermal pressure to magnetic pressure, undergoes a significant solar cycle variation, as expected from the variation in the IMF. Individual hourly averages of beta often exceed unity with 20 cases exceeding 10 and one case as high as 25. The Alfven Mach number shows a solar cycle variation similar to beta, lower aboard solar maximum. High-speed streams can be seen clearly in epsilon and the y component of the interplanetary magnetic field.

Freeman, John W.↗
NASA NTRS1987

Characteristics of the Marslike limit of the Venus-solar wind interaction

The response of the Venus ionosphere to the solar wind when the latter exceeds the peak thermal pressure in the Venus ionosphere is characterized on the basis of observations from the Pioneer Venus Orbiter. At these times, the Venus ionosphere becomes increasingly magnetized until the total ionospheric pressure matches that of the solar wind. The ionopause becomes less distinct and asymptotically approaches a limiting altitude of about 220 km for extremely high pressures. When the ionopause is low, the hot regions of electrons which occurs within the ionopause gradient extends to lower altitudes. The ion temperatures show little change, and there is no discernible increase in plasma wave activity at the ionopause. The Venus observations at high dynamic pressure provide a framework for reassessing the available Mars observations. In particular, this study shows that solar wind standoff without sufficient ionospheric plasma pressure cannot by itself be used as evidence for a planetary magnetic field.

Luhmann, J. G.↗