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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Western Pacific Hydroclimate Linked to Global Climate Variability Over the Past Two Millennia

Interdecadal modes of tropical Pacific ocean-atmosphere circulation have a strong influence on global temperature, yet the extent to which these phenomena influence global climate on multicentury timescales is still poorly known. Here we present a 2,000-year, multiproxy reconstruction of western Pacific hydroclimate from two speleothem records for southeastern Indonesia. The composite record shows pronounced shifts in monsoon rainfall that are antiphased with precipitation records for East Asia and the central-eastern equatorial Pacific. These meridional and zonal patterns are best explained by a poleward expansion of the Australasian Intertropical Convergence Zone and weakening of the Pacific Walker circulation (PWC) between B1000 and 1500 CE Conversely, an equatorward contraction of the Intertropical Convergence Zone and strengthened PWC occurred between B1500 and 1900 CE. Our findings, together with climate model simulations, highlight the likelihood that century-scale variations in tropical Pacific climate modes can significantly modulate radiatively forced shifts in global temperature.

Pacific Ocean↗
NASA NTRS1989

Space Power Free-Piston Stirling Engine Scaling Study

The design feasibility study is documented of a single cylinder, free piston Stirling engine/linear alternator (FPSE/LA) power module generating 150 kW-electric (kW sub e), and the determination of the module's maximum feasible power level. The power module configuration was specified to be a single cylinder (single piston, single displacer) FPSE/LA, with tuning capacitors if required. The design requirements were as follows: (1) Maximum electrical power output; (2) Power module thermal efficiency equal to or greater than 20 percent at a specific mass of 5 to 8 kg/kW(sub e); (3) Heater wall temperature/cooler wall temperature = 1050 K/525 K; (4) Sodium heat-pipe heat transport system, pumped loop NaK (sodium-potassium eutectic mixture) rejection system; (5) Maximum power module vibration amplitude = 0.0038 cm; and (6) Design life = 7 years (60,000 hr). The results show that a single cylinder FPSE/LA is capable of meeting program goals and has attractive scaling attributes over the power range from 25 to 150 kW(sub e). Scaling beyond the 150 kW(sub e) power level, the power module efficiency falls and the power module specific mass reaches 10 kg/kW(sub e) at a power output of 500 kW(sub e). A discussion of scaling rules for the engine, alternator, and heat transport systems is presented, along with a detailed description of the conceptual design of a 150 kW(sub e) power module that meets the requirements. Included is a discussion of the design of a dynamic balance system. A parametric study of power module performance conducted over the power output range of 25 to 150 kW(sub e) for temperature ratios of 1.7, 2.0, 2.5, and 3.0 is presented and discussed. The results show that as the temperature ratio decreases, the efficiency falls and specific mass increases. At a temperature ratio of 1.7, the 150 kW(sub e) power module cannot satisfy both efficiency and specific mass goals. As the power level increases from 25 to 150 kW(sub e) at a fixed temperature ratio, power module efficiency is seen to increase slightly, but at the expense of increased specific mass. An empirical equation relating power module thermal efficiency as a function of power module specific mass, power output, and temperature ratio is developed. Alternative configurations to the single cylinder, direct coupled linear alternator approach are also evaluated, but are shown to have technical drawbacks that lessen their attractiveness. The dynamic balance assembly mass (moving mass and structure) represents 20 to 30 percent of the total single cylinder power module mass. Joining two modules in a balanced opposed configuration eliminates the need for the balancer, and a hot end junction can be made without significant addition of structural mass. Recommendations are made for evaluation of advanced heat pipe concepts, tests of radial flow heat exchangers, and evaluation of high temperature alternator materials.

Jones, D.↗
NASA NTRS1979

Woodburning Heaters

On Apollo missions, the Lunar Module sewed as home and operating base for astronauts exploring the lunar surface. Since the moon has no layer of atmosphere to filter the sun's rays, the Lunar Module was exposed to extremely high daylight temperatures. To help cool the spacecraft, NASA employed a protective exterior coating capable of casting off, rather than absorbing, the sun's radiant energy. NASA selected an existing high temperature coating called Pyromark and asked the manufacturer to improve it to space-use specifications. Developed by Tempil Division of Big Three Industries, South Plainfield, New Jersey, Pyromark proved effective on the Lunar Module and it is similarly used on the Space Shuttle.

Source record↗
NASA NTRS1982

Temperature-Controlled Support for a Seed Crystal

A rodlike structure called a sting has been proposed for supporting a seed crystal at center of a body of saturated fluid and for controlling temperature/time profile of seed for experiments on crystal growth. Seed crystal is cooled or heated by thermoelectric modules while surrounding sheath remains at solution temperature. Heat is withdrawn to cooling fins by heat pipe, which replaces solid copper rod in a previous design.

Reeve, J. L.↗
NASA NTRS2008

Heat-Storage Modules Containing LiNO3-3H2O and Graphite Foam

A heat-storage module based on a commercial open-cell graphite foam (Poco-Foam or equivalent) imbued with lithium nitrate trihydrate (LiNO3-3H2O) has been developed as a prototype of other such modules for use as short-term heat sources or heat sinks in the temperature range of approximately 28 to 30 C. In this module, the LiNO3-3H2O serves as a phase-change heat-storage material and the graphite foam as thermally conductive filler for transferring heat to or from the phase-change material. In comparison with typical prior heat-storage modules in which paraffins are the phase-change materials and aluminum fins are the thermally conductive fillers, this module has more than twice the heat-storage capacity per unit volume.

Bootle, John↗
NASA NTRS1980

High efficiency compound semiconductor concentrator photovoltaics

Special emphasis was given to the high yield pilot production of packaged AlGaAs/GaAs concentrator solar cells, using organometallic VPE for materials growth, the demonstration of a concentrator module using 12 of these cells which achieved 16.4 percent conversion efficiency at 50 C coolant inlet temperature, and the demonstration of a spectral splitting converter module that achieved in excess of 20 percent efficiency. This converter employed ten silicon and ten AlGaAs cells with a dichroic filter functioning as the beam splitter. A monolithic array of AlGaAs/GaAs solar cells is described.

Borden, P.↗
NASA NTRS1999

Characterization of the Heat Extraction Capability of a Compliant, Sliding, Thermal Interface for Use in a High Temperature, Vacuum Microgravity Furnace

Much of the material science gained in microgravity research requires processing a sample in a high performance furnace. One such furnace currently being designed is the Quench Module Insert (QMI). The Principle Investigators, for whom the furnace is proposed, require high temperature gradients in their cylindrical samples to achieve the science objectives. One of the components critical to achieving high sample axial temperature gradients in the Quench Module Insert is a high performance cold zone to extract the heat from the sample. This cold zone employs a compliant, sliding thermal interface based on a Vel-Therm felt. This felt provides a conductive path between the Sample Cartridge Assembly (SCA) exterior surface and the interior surface of the water cooled chill block while allowing movement of the sample relative to the chill block. The Vel-Therm felt is composed of long polymer-based fibers affixed to a thin flexible substrate layer. The fibers are oriented perpendicular to this substrate giving the felt the appearance of a velvet fabric. The Vel-Therm felt heat extraction capability was quantified in earlier tests performed in an inert gas environment. The current activity, described in this paper, is intended to characterize the extraction capability of Vel-Therm felt in a vacuum environment similar to the QMI environment. This testing is necessary to quantify the thermal performance of the Vel-Therm felt and the sensitivity of that performance to key variables. The data derived from these tests will be incorporated into the current thermal models to improve the quality of the models and reduce uncertainty of the analytical results. In addition, the data will be used to help select the appropriate Vel-Therm felt and set proper operating limits as well as assess the performance range of the furnace. The objective of this test is to measure the heat extraction rate of the Vel-Therm felt as specified by the effective heat transfer coefficient. Therefore, the test setup was designed to force the bulk of the heat transfer through the area where the Vel-Therm felt was applied. A heat source, consisting of a ceramic heating element encased in a Copper (Cu) housing is mounted on four isolated support rods. A 6-layer molybdenum radiation shield is used to insulate against heat loss from the heater and prevent heat exchange between the hot and cold sides of the test apparatus. The Vel-Therm felt is affixed to the surface of the cold sink, a water-cooled Cu chill block. An adjustable plate supports and isolates the cold sink from above and is used to control the amount of the deflection of the Vel- Therm when in contact with the Cu heating element housing. The primary means of establishing the power being conducted through the felt is to measure the energy being transferred to the water passing through the chill block. Analysis was performed to support the assumption that the source and sink surfaces were approximately isothermal under the specific test conditions. As a check on the amount of power passing through the felt, the power supplied to the heater was also measured. Thermocouples were strategically located throughout the test apparatus for measurement purposes. A bell jar was lowered over the assembly to impose vacuum conditions. Currently, variables tested have been fiber compression and fiber type and surface temperatures (both the hot and cold side temperatures are hypothesized to be important to the performance of the Vel-Therm.) Selected runs were repeated to ensure consistency and repeatability. Results obtained thus far reveal that Vel-Therm performance is significantly degraded by fibers being exposed to high compression. It also shows that performance is somewhat negatively impacted by previous compression, thereby, raising the question of repeatability. In addition, early results show a significant dependence on temperature. A computer aided mathematical analysis of the test setup is ongoing. The results will be correlated to actual results. The correlation will examine such details as parasitic loses, conduction down the power leads and many other concerns.

Bellomy-Ezell, Jenny↗
NASA NTRS1972

Linear modulator

A study of frequency division multiplexing (FDM) systems was made for the purpose of determining the system performance that can be obtained with available state of the art components. System performance was evaluated on the basis of past experience, system analysis, and component evaluation. The system study was specifically directed to the area of FDM systems using subcarrier channel frequencies from 4 kHz to 200 kHz and channel information bandwidths of dc to 1, 2, 4, 8, and 16 kHz. The evaluation also assumes that the demodulation will be from a tape recorder which produces frequency modulation of + or - 1% on the signal due to the tape recorder wow and flutter. For the modulation system it is assumed that the pilot and carrier channel frequencies are stable to within + or - .005% and that the FM on the channel carriers is negligible. The modulator system was evaluated for the temperature range of -20 degree to +85 degree while the demodulator system was evaluated for operation at room temperature.

Source record↗
NASA NTRS1984

Measuring Delay in Lasers

Technique measures delay, i.e., response time of modulated diode laser as function of temperature by comparing excitation signal to laser output signal with vector voltmeter.

Bergman, L. A.↗
NASA NTRS1983

Spacecraft contamination environment; Proceedings of the Meeting, Arlington, VA, May 4-6, 1982

Aspects of IECM debriefing are considered, taking into account preliminary results of the induced environment contamination monitor measurements of STS-2, the humidity monitor and dew point hygrometer, the induced environment contamination monitor cascade impactor, the optical effects module and passive sample array, temperature-controlled quartz crystal microbalance measurements on STS-2, camera/photometer results, the mass spectrometer, and a summary regarding the induced environment contamination monitor/space transport system. Other subjects explored are related to contamination management and control, contamination/optical degradation, and contamination assessments and measurements. Attention is given to approaches for controlling contamination before launch, the coronagraph as the ultimate device to monitor orbiting particulates in the Space Transport System environment, and the contamination sensitivity of typical mirror coatings.

Maag, C. R.↗
NASA NTRS1984

Status of high efficiency module design and fabrication

The status of an ongoing DOE program to develop an AM1 photoelectric module with 15 percent conversion efficiency at normal heating temperatures, is reviewed. Emphasis is given to the efforts of a private company to develop a high efficiency module which also has high durability in normal operating conditions. The main design options considered are: high efficiency modules; large area modules; and optimized module fabrication techniques. The design of an automatic system for encapsulating module stacks is described.

Nowlan, M. J.↗
NASA NTRS1986

Comet rendezvous - The next stage in cometary exploration

NASA's Comet Rendezvous Asteroid Flyby (CRAF) mission to P/Tempel 2 is described with attention given to CRAF spacecraft design. Infrared/visible spectrometers, dust counters, magnetometers, and plasma-wave analyzers are an integral part of the CRAF payload. CRAF's subsystems consist of the following: (1) a structure subsystem, (2) a temperature control subsystem, (3) a propulsion module subsystem, (4) an attitude control subsystem, (5) a command and data subsystem, (6) a radio frequency subsystem, and (7) a power and pyrotechnics subsystem. It is concluded that the CRAF mission will enable the first detailed study of the cometary nucleus.

Collins, D. H.↗
NASA NTRS1989

Non-ideality near the monotectic composition of a miscibility-gap type system - Succinonitrile-water

Differential scanning calorimetry (DSC) of near monotectic succinonitrile-water solutions, fast-quenched in hydrophilic and hydrophobic DSC pans, indicate, by degree of undercooling, thst there may be significant dependence of final ingot microstructure on the pre-quench equilibration temperature. Partial molal-volume determinations from density data, along with DSC data, suggest the nature of temperature dependent component associations from 20 to 55 C in homogeneous solutions. The undercooling profile in a hydrophilic container is explained in terms of solution-composition shifts arising from the Gibbs surface excess. The evidence shows that temperature-dependent preferred component aggregates may modulate surface-composition gradients. Similar effects may be present through intermetallic compound formation in metallic monotectic alloys.

Frazier, D. O.↗
NASA NTRS1990

Short-term FUV flux variability and phase-dependent winds in Be stars

FUV (Far Ultraviolet) light curves and the behavior of the C IV wind line versus phase are discussed for four Be stars. The IUE (International Ultraviolet Explorer) data acquired during three multiwavelength campaigns aimed at determining the cause for short term optical light variability in Be stars and whether it is linked with the mass loss mechanism is presented. The observations confirm that it is a modulation in the star's photospheric temperature that causes the flux variability. A phase dependent variation is seen in the equivalent width and profile in the C IV wind line. The wind absorption tends to be strongest at maximum light and in a Be shell star the absolute flux of its C IV emission component appears to be anticorrelated with the absorption strength and the level of the FUV flux. The observations suggest that nonradial pulsations are responsible for the photometric variability and the generic model of a star pulsating in a sectorial mode.

Peters, G. J.↗
NASA NTRS1990

Test results of a diffraction grating beam combiner

A laser diode beam combiner employing diffraction gratings has been fabricated and tested. The Grating Laser Beam Combiner (GLBC) uses two holographic diffraction gratings to incoherently combine the first order diffraction components of four 35 mW AlGaAs lasers. The grating rhomb design minimizes the transmitter sensitivity to the inherent frequency instability of laser diodes. The overall throughput of the combiner is 74 percent. Each laser was temperature controlled to 0.1 C and modulated with 110 Mbps QPPM data. Two lasers under modulation were coaligned to within 76 microrad with a combined average power of 45 mW.

Rall, Jonathan A.↗
NASA NTRS1993

Balloons on planet Venus - Final results

On June 11 and 15, 1985 two packages with balloons have been inserted in the atmosphere of Venus from the Soviet VEGA landing modules. This paper summarizes the pressure, temperature, wind illumination and backscattering data from the balloons.

Blamont, J.↗