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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Instabilities of dynamic thermocapillary liquid layers. I Convective instabilities

A steady shear flow is set up in a planar liquid layer bounded below by a rigid plate, and above by an interface with a passive gas, by imposing a temperature gradient along the layer and driving the motion by thermocapillarity. The thermal-convective instabilities to which this dynamic state is susceptible include stationary longitudinal rolls involving the classical Marangoni instability, and unsteady hydrothermal waves, whose new instability mechanism derives its energy from the horizontal temperature gradients. The thermal stability characteristics for liquid layers with and without return flow profiles are presently given as functions of the Prandtl number for the liquid and the Biot number for the interface, and comparisons are made with available experimental observations.

Smith, M. K.↗
NASA NTRS1986

Analysis of cirrus from airborne lidar and radiometer observations

Lidar and passive radiance sensing data on cirrus clouds gathered in instrumented high altitude aircraft flights are analyzed, with emphasis on cirrus emittance characteristics. The data were collected with a U-2 aircraft flying at about 19 km altitude. Lidar data defined the vertical structure of the cloud which, when combined with independent atmospheric temperature data, permitted radiance to be derived from thermal radiance data. Sample return lidar images are provided of cirrus and cirrostratus clouds, along with the calculated emittance data.

Spinhirne, J. D.↗
NASA NTRS1988

The origin of broad emission line clouds in active galactic nuclei

Numerous arguments suggest that the broad emission lines characteristic of many types of active galactic nuclei are formed in comparatively cool clouds embedded in a much hotter medium of roughly equal pressure. Here it is shown that a cycle exists in which cooler condensations form within the hot medium via a finite-amplitude thermal instability, drop to temperatures characteristic of photoionization equilibrium, are destroyed by hydrodynamic processes, and then return their material to the hot medium. Clouds of characteristic pressure about 10 to the 14th K/cu cm and thickness about 10 to the 23rd/sq cm are produced by this mechanism, in agreement with the pressure and thickness inferred from photoionization model analysis of observed emission-line ratios. Only a fraction of the hot medium's mass must encounter a finite-amplitude perturbation in order to produce the observed mass in clouds.

Krolik, Julian H.↗
NASA NTRS1991

Problems and solutions for transition detection in cryogenic wind tunnels by infrared imaging

The authors analyzed the problems associated with the detection of boundary-layer transition to turbulence by using the IR imaging techique in cryogenic wind-tunnel testing. It is shown that testing at low temperatures forces this implementation to run against the physical laws of diminishing returns. The most difficult obstacle resulted from the considerable decrease in the overall level of IR radiation and the parallel shift of the bulk of the radiated energy to longer wavelengths, beyond 30 microns at 100 K. Some measures to alleviate the problem are described. The thermal signature of transition can be enhanced by allowing the flow in the wind tunnel to heat incrementally, thus inducing a transient heat transfer to the model. As a result, the model area under the turbulent regime is revealed by its higher heating rate compared to the laminar regime.

Gartenberg, Ehud↗
NASA NTRS1992

Post flight operation of a high peak power neodymium YAG laser aboard the G-449 payload flown on Space Shuttle Columbia mission 61-C

The Nd Yag laser flown on board the G-449 payload completed its postflight testing successfully. There was no indication that the laser had undergone any electronic or optical component failure. A postflight video was taken immediately following the return of the payload to the laboratory. Early anticipation of vibration and temperature changes contributed to the successful operation of the laser. Photographic material resulting from post flight videotape are presented. NASA safety reviews and recommendations supplied the insights which helped contribute to the successful operation of the Nd Yag laser. The safety review data is part of the technical presentation and gives some insight into why the system survived the severe environment of temperature and vibration during the flight of Space Shuttle 61-C.

Muckerheide, M. C.↗
NASA NTRS1998

Trends in the Annual Frequency of Atlantic Basin Intense Hurricanes: Implications for the Near-Term

During the interval of 1944-1997, 120 intense hurricanes (category 3, 4, or 5 on the Saffir-Simpson hurricane scale) have been observed in the Atlantic basin. These intense hurricanes have had an observed annual frequency of 0-7 events per year (having a mean, mode, and median equal to about 2 events per year), being preferentially lower during El Ninio years and higher during non-El Ninio years. Also, it has recently been established that a long-term downward trend in the annual frequency of intense hurricanes, spanning about five decades, has taken place, although this trend can, alternatively, be explained as a shift from a more active state prior to the mid 1960's to a less active state thereafter (rather than as a simple linear decline). In this paper, on the basis of 10-yr moving averages, the long4erm trend of the frequency of intense hurricanes is compared against one for the annual mean temperature at Armagh Observatory, Northern Ireland (which serves as a proxy for climatic change). Interestingly, the two sets of 10-yr moving averages correlate extremely well, especially, when incorporating a slight 6-yr lag between them (with temperature leading; r = 0.90). This suggests that the current leading trend of temperature, which had been downward, but now is upward, may portend a return to the more active state for intense hurricanes. Thus, the 1998 season (presuming the abatement of El Ninio prior to the start of the hurricane season), and for several years thereafter (at least, into the early years of the next millennium), may have an annual frequency of intense hurricanes that is commensurate with the previously observed active state that was seen prior to the mid 1960's. If true, then, the shift to the more active state, probably, occurred in the mid-to-late 1980's, apparently, having gone undetected because of the masking, or modulating, effect of El Ninio, which has been rampant since the mid-to-late 1980's.

Wilson, Robert M.↗
NASA NTRS2000

A Hot-Electron Far-Infrared Direct Detector

A new approach is proposed to improve the sensitivity of direct-detection bolometers at millimeter, submillimeter and far-infrared wavelengths. The idea is to adjust a speed of the thermal relaxation of hot-electrons in a nanometer size normal metal or super-conductive transition edge bolometer by controlling the elastic electron mean free path. If the bolometer contacts are made of a superconductor with high critical temperature (Nb, Pb etc.) then the thermal diffusion into the contacts is absent because of the Andreev's reflection and the electron-phonon relaxation is the only mechanism for heat removal. The relaxation rate should behave as T(sup 4)l at subkelvin temperatures (l is the electron elastic mean free path) and can be reduced by factor of 10-100 by decreasing l. Then an antenna- or waveguide-coupled bolometer with a time constant about 10(exp -3) to 10(exp -5) s at T approximately equals 0.1-0.3 K will exhibit photon-noise limited performance in millimeter and submillimeter range. The choice of the bolometer material is a tradeoff between a low electron heat capacity and fabrication. A state-of-the-art bolometer currently offers NEP = 10(exp -17) W(Square root of (Hz)) at 100 mK along with a approximately equals 2 msec time constant. The bolometer we propose will have a figure-of-merit, NEP(square root (r)), which is 10(exp 3) times smaller. This will allow for a tremendous increase in speed which will have a significant impact for observational mapping applications. Alternatively, the bolometer could operate at higher temperature with still superior sensitivity. This device can significantly increase a science return and reduce the cost for future observational missions. This research was performed by the Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, and was sponsored by NASA, Office of Space Science.

Karasik, B. S.↗
NASA NTRS2019

Long-Duration Venus Lander Development

One of the most intriguing planets in our solar system for both solar system and extra-solar system science is Venus. Venus is the planet most similar to Earth in several key ways and many believe Venus-like planets are more common around other suns than are Earth-like planets. Therefore scientific understanding of our sister planet is a high priority. However, the hostile environmental conditions at the surface coupled with thick acid clouds and dense atmosphere have made understanding this planet very challenging. Remote sensing of surface features and near surface environments is very limited. The hostile environment has also limited the ability of landers to survive, in fact the longest living asset survived just over two hours. Even after over 50 years of attempts to explore Venus, many key measurements, especially near the surface, are still in the future. NASA has begun to undertake steps to overcome the technical challenges and is developing the capability for sustained operations and science return from this important body. For example, recent technology advances in high temperature sensors, electronics, power, and other systems have been funded and this, combined with the new capabilities to replicate Venus conditions on Earth, are changing the outlook for Venus surface exploration.

Kremic, Tibor↗
NASA NTRSDate not supplied

Capability Improvements at Marshall Space Flight Center's X-Ray and Cryogenic Facility

The X-Ray & Cryogenic Facility (XRCF) at Marshall Space Flight Center is the world’s largest x-ray optic calibration facility and NASA’s premier cryogenic optical test facility. Built specifically to calibrate the Chandra telescope, the facility contributed to several other x-ray missions until 2005 when it became dedicated to normal incidence optical testing at cryogenic temperatures. Recently the facility’s x-ray test capability has been returned to service and updated. New beam monitors, focal plane detectors, and test article and instrument positioning systems have been added. The x-ray data acquisition system has been updated. A real-time position monitoring metrology system is being developed that will enable calibration of large diameter optics via partial illumination in a diverging beam. The newly expanded x-ray test capabilities of the facility will be discussed.

XRCF↗
DOE OSTI2020

Neutronic Consideration of TREAT Facility Fuel SiC Recladding

The Transient Reactor Test (TREAT) Facility is an air-cooled reactor composed of graphite-urania fuel encapsulated in zirconium alloy canisters and surrounded by ~2 ft (~61 cm) of nuclear grade graphite. The primary role of TREAT is to provide in-pile nuclear-heated safety research via transient testing [1]. Benchmark efforts have demonstrated sensitivity of TREAT neutronics models to graphite cross section data and key neutron poisons found in the fuel assemblies [2]. During fabrication of TREAT fuel assemblies, a small concentration of boron was inadvertently introduced with variable concentration into the aggregate of fuel blocks prepared for TREAT use. The concentration of boron, and its respective uncertainty, represent the most sensitive component in a neutronics study; unfortunately, nothing can be done to reduce or otherwise mitigate its impact. Hydrogen in the fuel blocks reduces the mean free path of the core and its true quantity and uncertainty is approximated. The hydrogen remains from pitch binder used in the fuel fabrication process and was not completely released due to incomplete fuel graphitization. Destructive fuel testing is necessary to quantify the actual hydrogen content and to improve benchmark model quality. A third neutron poison of some significance is the hafnium impurity in the Zircaloy-3 (Zry-3) assembly cladding. The quantity of hafnium is expected to be within nominal manufacturing limits for nuclear grade zircaloy. Recladding the fuel assemblies with material that is less neutron absorbing is expected to benefit reactor neutron economy. Moreover, TREAT’s total transient energy is restricted based on the rate of Zry-3 oxidation in TREAT’s air coolant environment. Hence, cladding with more benign air reaction kinetics could dramatically uprate the facility’s experimental capability. Silicon carbide (SiC) has been proposed as a candidate material for recladding TREAT assemblies, as SiC/SiC demonstrate favorable properties within nuclear environments [3]. The current operational limits of TREAT are restricted by the oxidation of Zry-3. Change of the cladding to SiC could feasibly double the current temperature limitation. Recladding opportunities allow for previously damaged fuel assemblies to be returned to service, as Zry-3 is not commercially available. The initial effort required to consider proceeding with any recladding effort is to neutronically characterize key reactor parameters while replacing Zry-3 with SiC. A characterization summary, with respective results, is provided herein.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1986

Remote temperature profiling in the troposphere and stratosphere by the radio-acoustic sounding technique

Radar application of the radio-acoustic sounding technique uses the Doppler frequency shift of radar echoes returning from the atmospheric wave structure, in association with a traveling acoustic pulse transmitted from the ground, to determine the speed of sound, and hence the atmospheric temperature, as a function of altitude. Temperature measurement in the troposphere and stratosphere were determined using the radio-acoustic sounding technique with the Radio-Acoustic Sounding System (RASS). Successful experiments were performed in March 1985, and in August 1985.

Matuura, N.↗
DOE OSTI2019

Numerical study of the temperature dependence of the NMR relaxation rate across the superfluid–Bose glass transition in one dimension

Here, we study the nuclear magnetic resonance (NMR) spin-lattice relaxation rate 1/ T 1 1 in random one-dimensional spin chains as a function of the temperature and disorder strength. In the zero temperature limit, the system displays a disorder-induced quantum phase transition between a critical Tomonaga-Luttinger liquid (TLL) phase and a localized Bose glass phase. The 1/ T 1 is investigated across this transition using large-scale simulations based on matrix product state techniques. We find that this quantity can detect the transition and probe the value of the dimensionless TLL parameter K . We also compute the NMR relaxation rate distributions for each temperature and disorder strength considered. In particular, we discuss the applicability of the stretched exponential fit to the return-to-equilibrium function to extract the 1/ T 1 experimentally. The results presented here should provide valuable insights in regards of future NMR experiments in realistic disordered spin compounds.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1982

Use of thermocapillary migration in a controllable heat valve

In accordance with the Marangoni effect, immiscible droplets in a host fluid in which a temperature gradient exists move in the direction of increasing temperature. It is proposed that this thermocapillary migration could be used to construct a 'liquid wick' that would return the condensed vapor at the condenser end of a heat pipe back to the evaporator, thus completing the fluid circuit. The droplets would be formed by capillary pressure forcing the condensate through a perforated diaphragm whose temperature would control the droplet flux, and hence the heat flux between the two ends of the heat pipe, thus making it a controllable heat valve.

Schmid, L. A.↗
NASA NTRS2006

Sensor Amplifier for the Venus Ground Ambient

Previous Venus Landers employed high temperature pressure vessels, with thermally protected electronics, to achieve successful missions, with a maximum surface lifetime of 127 minutes. Extending the operating range of electronic systems to the temperatures (480 C) and pressures (90 bar) of the Venus ground ambient would significantly increase the science return of future missions. Toward that end, the current work describes the innovative design of a sensor preamplifier, capable of working in the Venus ground ambient and designed using commercial components (thermionic vacuum tubes, wide band gap transistors, thick film resistors, advanced high temperature capacitors, and monometallic interfaces) To identify commercial components and electronic packaging materials that are capable of operation within the specified environment, a series of active devices, passive components, and packaging materials were screened for operability at 500C, assuming a 10x increase in the mission lifetime. In addition. component degradation as a function of time at 500(deg)C was evaluated. Based on the results of these preliminary evaluations, two amplifiers were developed.

Venus electronics↗
NASA NTRS2006

Generation of Data-Rate Profiles of Ka-Band Deep-Space Links

A short report discusses a methodology for designing Ka-band Deep-Space-to- Earth radio-communication links. This methodology is oriented toward minimizing the effects of weather on the Ka-band telecommunication link by maximizing the expected data return subject to minimum link availability and a limited number of data rates. This methodology differs from the current standard practices in which a link is designed according to a margin policy for a given link availability at 10 elevation. In this methodology, one chooses a data-rate profile that will maximize the average data return over a pass while satisfying a minimum-availability requirement for the pass, subject to mission operational limitations expressed in terms of the number of data rates used during the pass. The methodology is implemented in an intelligent search algorithm that first finds the allowable data-rate profiles from the mission constraints, spacecraft-to-Earth distance, spacecraft EIRP (effective isotropic radiated power), and the applicable zenith atmospheric noise temperature distribution, and then selects the best data rate in terms of maximum average data return from the set of allowable data-rate profiles.

Shambayati, Shervin↗
NASA NTRS2009

High Temperature Antenna Measurement System with GSG or GS Contact Probing Capability

Applications that require data transmission at high temperatures are becoming more common due to growing commercial and military needs. Antennas are an indispensable part of these systems and the ability to characterize them at elevated temperatures is quite complicated with little or no information being reported on the subject [1]. This paper describes a measurement system that can characterize planar antennas up 600 C with ground-signal-ground (GSG) or ground-signal (GS) probe contacts. The return loss and radiation patterns of a folded slot antenna (FSA), designed to operate at 5 GHz (no ground plane on back side) and fabricated on an alumina substrate, are presented at room temperature (RT) and 250 C [2]. All measurements were made with Agilent's Precision Network Analyzer (PNA) E8361. The return loss and radiation patterns were also measured on a Styrofoam chuck to illustrate the effect the high temperature measurement system has on the patterns.

Jordan, Jennifer L.↗
NASA NTRS1991

The magnitude of the magnetic field near the surface of a high-T(sub c) superconductor with a trapped flux

In 1986, much excitement was caused by the discovery of a class of materials that conducted electricity with zero resistance at temperatures above the boiling temperature of liquid nitrogen. This excitement was checked by the difficulties of manufacturing ceramics and the usefulness of high temperature superconductors that were restricted by their becoming high resistive conductors at small current densities. A lack of pinning of the magnetic field flux caused the return of high resistance as the current was increased in these materials. A study of the magnetic field near the surface of a high temperature superconductor is the first step in the search for a means of pinning the flux lines and increasing their critical current densities. The author found that a comparison between the defects in the surface of the superconductor and the magnetic field showed only a change in the field near the notch and the edge. No correlation was found between the surface grain or structure and the oscillations in the magnetic field. The observed changes in the magnetic field show resonances which may give an indication of the non-flux pinning in these superconductors. A flux pinning mechanism will increase the critical current densities; therefore, other methods of determining this field should be tried. The author proposes using a flux gate magnetometer with a detector wound on a ferrite core to measure the magnitude and direction of the magnetic field.

Overcash, Dan R.↗