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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Thermodynamic Analysis of the 3-Stage ADR for the Astro-H Soft X-Ray Spectrometer Instrument

The Soft X-ray Spectrometer (SXS) instrument on Astro-H will use a 3-stage ADR to cool the microcalorimeter array to 50 mK. In the primary operating mode, two stages of the ADR cool the detectors using superfluid helium at 1.20 K as the heat sink. In the secondary mode, which is activated when the liquid helium is depleted, two of the stages continuously cool the (empty) helium tank using a 4.5 K Joule-Thomson cooler as the heat sink, and the third stage cools the detectors. In the design phase, a high-fidelity model of the ADR was developed in order to predict both the cooling capacity and heat rejection rates in both operating modes. The primary sources of heat flow are from the salt pills, hysteresis heat from the magnets and magnetic shields, and power dissipated by the heat switches. The flight instrument dewar, ADR, detectors and electronics were integrated in mid-2014 and have since undergone extensive performance testing, in part to validate the performance model. This paper will present the thermodynamic performance of the ADR, including cooling capacity, heat rejection to the heat sinks, and various measures of efficiency.

space cryogenics↗
NASA NTRS2008

Transient Three-Dimensional Startup Side Load Analysis of a Regeneratively Cooled Nozzle

The objective of this effort is to develop a computational methodology to capture the startup side load physics and to anchor the computed aerodynamic side loads with the available data from a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, a transient 5 s inlet history based on an engine system simulation, and a wall temperature distribution to reflect the effect of regenerative cooling. To understand the effect of regenerative wall cooling, two transient computations were performed using the boundary conditions of adiabatic and cooled walls, respectively. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with the pulsation of shocks across the lip, although the combustion wave is commonly eliminated with the sparklers during actual test. The test measured two side load events: a secondary and lower side load, followed by a primary and peak side load. Results from both wall boundary conditions captured the free-shock separation to restricted-shock separation transition with computed side loads matching the measured secondary side load. For the primary side load, the cooled wall transient produced restricted-shock pulsation across the nozzle lip with peak side load matching that of the test, while the adiabatic wall transient captured shock transitions and free-shock pulsation across the lip with computed peak side load 50% lower than that of the measurement. The computed dominant pulsation frequency of the cooled wall nozzle agrees with that of a separate test, while that of the adiabatic wall nozzle is more than 50% lower than that of the measurement. The computed teepee-like formation and the tangential motion of the shocks during lip pulsation also qualitatively agree with those of test observations. Moreover, a third transient computation was performed with a proportionately shortened 1 s sequence, and lower side loads were obtained with the higher ramp rate.

Wang, Ten-See↗
NASA NTRS1982

UV eclipse observations of CI Cyg

Low spectral resolution observations were obtained with the IUE during the eclipse phase. Additional data obtained by other IUE groups have been included in the eclipse observations, making it possible to examine the UV spectral properties of CI Cyg over nearly an entire orbit which spans early 1979 through mid 1981. Data obtained over this period suggest an overall decline in UV emission, consistent with the decline of optical emission following the outburst of 1975. The short-wavelength spectrum 1200-2000 A is characterized by numerous intense high-excitation emission lines which become more prominent out of eclipse. The LWR wavelength range 2000-3200 A exhibits a few more additional lines of O III, Mg II, and He II which are superimposed on continuum that rises gradually with increasing wavelength. The observations are consistent with a binary star model which involves mass transfer from the extended cool envelope of the primary to the compact secondary.

Michalitsianos, A. G.↗
NASA NTRS1984

Cold-Crucible Premelter for Silicon

System allows replenishment of silicon melt in crystal puller. Cold crucible consists of water-cooled, silver plated boat in 500kHz field. Induced secondary currents cause preheated chunks of silicon to melt. Magnetic repulsion between current in silicon and in boat prevents silicon from touching boat. Used for crystal growth of other materials sufficiently conductive and difficult to keep free of contamination by container walls at temmperature of operation.

Lane, R. L.↗
NASA NTRS1985

Discovery of an accretion shock cone in 22 Vulpeculae

A previous report that 22 Vul is a zeta Aurigae-type eclipsing binary is supported by the discovery of evidence for an accretion shock cone in 22 Vul similar to those found in zeta Aurigae and 32 Cygni. Such systems consist of a cool supergiant star primary and a hot dwarf secondary (G3 Ib-II and B9 in the case of 22 Vul) and undergo atmospheric eclipses.

Ahmad, I. A.↗
NASA NTRS1986

Dual throat thruster test results

Test results are presented for a dual throat thruster burning gaseous oxygen and hydrogen at primary (inner) chamber pressures from 380 to 680 psia. Heat flux profiles were obtained from calorimetric cooling channels in the inner nozzle, outer or secondary chamber and the tip of the inner nozzle. Data were obtained for two nozzle spacings over a chamber pressure ratio (secondary/primary) range of 0.45 to 0.83 with both chambers firing (Mode I). Fluxes near the end of the inner nozzle were significantly higher than in Mode II when only the inner chamber was fired, due to flow separation and recirculation caused by the back pressure imposed by the secondary chamber. As the pressure ratio increased, these heat fluxes increased and the region of high heat flux relative to Mode II extended farther upstream. The use of a gaseous hydrogen bleed flow in the secondary chamber to control heat fluxes in the primary plume attachment region was investigated in Mode II testing. A bleed flow of less than two percent of the primary chamber flow was required.

Ewen, R. L.↗
NASA NTRS1986

Dual-throat thruster thermal model

The dual-throat engine is one of the dual nozzle engine concepts studied for advanced space transportation applications. It provides a thrust change and an in-flight area ratio change through the use of two concentric combustors with their throats arranged in series. Test results are presented for a dual throat thruster burning gaseous oxygen and hydrogen at primary (inner) chamber pressures from 380 to 680 psia. Heat flux profiles were obtained from calorimetric cooling channels in the inner nozzle, outer or secondary chamber and the tip of the inner nozzle. Data were obtained for two nozzle spacings over a chamber pressure ratio (secondary/primary) range of 0.45 to 0.83 with both chambers firing (Mode I). Fluxes near the end of the inner nozzle were significantly higher than in Mode II when only the inner chamber was fired, due to the flow separation and recirculation caused by the back pressure imposed by the secondary chamber. As the pressure ratio increased, these heat fluxes increased and the region of high heat flux relative to Mode II extended farther upstream. The use of the gaseous hydrogen bleed flow in the secondary chamber to control heat fluxes in the primary plume attachment region was investigated in Mode II testing. A thermal model of a dual throat thruster was developed and upgraded using the experimental data.

Ewen, R. L.↗
NASA NTRS1988

The stellar wind velocity function for red supergiants determined in eclipsing binaries

The potential for direct measurement of the acceleration of stellar winds from the supergiant component of Zeta Aurigae-type binary stars is discussed. The aberration angle of the interaction shock cone centered on the hot star provides a measure of the velocity of the cool star wind at the orbit of the secondary. This is confirmed by direct observations of stellar wind (P Cygni) line profile variations. This velocity is generally smaller than the final (terminal) velocity of the wind, deduced from the P Cygni line profiles. The contrast between these results and previously published supergiant wind models is discussed. The implication on the physics of energy source dissipation predicted in the theoretical models is considered.

Ahmad, Imad A.↗
NASA NTRS1980

The secondary circulation associated with a vertically aligned planetary wave critical line

An analytic model of the secondary circulation associated with a vertically aligned, energy absorbing, planetary wave critical line shows that strong zonal mean vertical motions and heating (or cooling) can develop even though no eddy transport of heat occurs. The type of secondary circulation which develops around a vertically aligned critical line may provide a mechanism for stratosphere-troposphere exchange of air. The model predictions are discussed with reference to the 76/77 sudden warming.

Schoeberl, M. R.↗
NASA NTRS1977

The metallic microstructures and thermal histories of severely reheated chondrites

The metallographic structures of eight severely reheated chondrites - Farmington, Ramsdorf, Orvinio, Wickenburg, Lubbock, Rose City, Arapahoe, and Tadjera - were studied using optical, SEM and electron microprobe techniques. The following metallographic criteria were used to estimate the post-shock residual temperature of the chondrites: melted metal-troilite appearance, presence of martensite, phosphorus enrichment of metal and averaging of central metal grain compositions. The presence of phosphides and secondary kamacite are due to slow post-shock cooling rates. Ni rim gradients indicate both extensive remelting of metal grains and relatively fast cooling.

Smith, B. A.↗
NASA NTRS1981

JT8D-15/17 High Pressure Turbine Root Discharged Blade Performance Improvement

The JT8D high pressure turbine blade and seal were modified, using a more efficient blade cooling system, improved airfoil aerodynamics, more effective control of secondary flows, and improved blade tip sealing. Engine testing was conducted to determine the effect of these improvements on performance. The modified turbine package demonstrated significant thrust specific fuel consumption and exhaust gas temperature improvements in sea level and altitude engine tests. Inspection of the improved blade and seal hardware after testing revealed no unusual wear or degradation.

Janus, A. S.↗
NASA NTRS1980

A portable He-3 cryostat for studies in astrophysics

The paper reviews the design, operation, and testing of a portable He-3 cryostat developed for astrophysical studies. The goal of the program was to develop an He-3 cryostat capable of cooling three bolometers to the 0.3-K temperature range for periods of more than six hours; a secondary goal was to evaluate the use of He-4 as the working fluid in a similar cryostat to provide cooling to infrared bolometers in the 0.8-K temperature range. It is planned to employ the He-3 cryostat for an infrared astronomy balloon flight. The cooler would be used with He-3 to achieve a 0.34-K bolometer temperature.

Sherman, A.↗
NASA NTRS1983

A microprocessor-based position control system for a telescope secondary mirror

The pointing requirements for the Shuttle IR Telescope Facility (SIRTF), which consists of an 0.85-m cryogenically cooled IR telescope, call for an image stability of 0.25 arcsec. Attention is presently given to a microprocessor-based position control system developed for the control of the SIRTF secondary mirror, employing a special control law (to minimize energy dissipation), a precision capacitive position sensor, and a specially designed power amplifier/actuator combination. The microprocessor generates the command angular position and rate waveforms in order to maintain a 90 percent dwell time/10 percent transition time ratio independently of chop frequency or amplitude. Performance and test results of a prototype system designed for use with a demonstration model of the SIRTF focal plane fine guidance sensor are presented.

Lorell, K. R.↗
NASA NTRS2001

High-Efficiency Solar Thermal Vacuum Demonstration Completed for Refractive Secondary Concentrator

Common to many of the space applications that utilize solar thermal energy--such as electric power conversion, thermal propulsion, and furnaces--is a need for highly efficient, solar concentration systems. An effort is underway at the NASA Glenn Research Center to develop the refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. When used in combination with advanced lightweight primary concentrators, the refractive secondary concentrator enables very high system concentration ratios (10,000 to 1) and very high temperatures (>2000 K). The innovative refractive secondary concentrator offers significant advantages over all other types of secondary concentrators. The refractive secondary offers the highest throughput efficiency, provides for flux tailoring, requires no active cooling, relaxes the pointing and tracking requirements of the primary concentrator, and enables very high system concentration ratios. This technology has broad applicability to any system that requires the conversion of solar energy to heat. Glenn initiated the development of the refractive secondary concentrator in support of Shooting Star, a solar thermal propulsion flight experiment, and continued the development in support of Space Solar Power.

Wong, Wayne A.↗
NASA NTRS1986

Effect of flame-tube head structure on combustion chamber performance

The experimental combustion performance of a premixed, pilot-type flame tube with various head structures is discussed. The test study covers an extensive area: efficiency of the combustion chamber, quality of the outlet temperature field, limit of the fuel-lean blowout, ignition performance at ground starting, and carbon deposition. As a result of these tests, a nozzle was found which fits the premixed pilot flame tube well. The use of this nozzle optimized the performance of the combustion chamber. The tested models had premixed pilot chambers with two types of air-film-cooling structures, six types of venturi-tube structures, and secondary fuel nozzles with two small spray-cone angles.

Gu, Minqqi↗
NASA NTRS1957

Experimental Investigation of Ejector-nozzle Metal Temperatures

Metal temperatures were obtained on a full-scale ejector nozzle installed on an afterburner operating at exhaust-gas temperatures up to 3450 degrees R. A favorable afterburner-outlet temperature profile helped keep the primary-jet nozzle components cool. The ejector shroud temperatures were much more sensitive to secondary airflow than were temperatures on the primary-jet nozzle.

Shillito, Thomas B↗
NASA NTRS2012

Ultra-Compact Motor Controller

This invention is an electronically commutated brushless motor controller that incorporates Hall-array sensing in a small, 42-gram package that provides 4096 absolute counts per motor revolution position sensing. The unit is the size of a miniature hockey puck, and is a 44-pin male connector that provides many I/O channels, including CANbus, RS-232 communications, general-purpose analog and digital I/O (GPIO), analog and digital Hall inputs, DC power input (18-90 VDC, 0-l0 A), three-phase motor outputs, and a strain gauge amplifier. This controller replaces air cooling with conduction cooling via a high-thermal-conductivity epoxy casting. A secondary advantage of the relatively good heat conductivity that comes with ultra-small size is that temperature differences within the controller become smaller, so that it is easier to measure the hottest temperature in the controller with fewer temperature sensors, or even one temperature sensor. Another size-sensitive design feature is in the approach to electrical noise immunity. At a very small size, where conduction paths are much shorter than in conventional designs, the ground becomes essentially isopotential, and so certain (space-consuming) electrical noise control components become unnecessary, which helps make small size possible. One winding-current sensor, applied to all of the windings in fast sequence, is smaller and wastes less power than the two or more sensors conventionally used to sense and control winding currents. An unexpected benefit of using only one current sensor is that it actually improves the precision of current control by using the "same" sensors to read each of the three phases. Folding the encoder directly into the controller electronics eliminates a great deal of redundant electronics, packaging, connectors, and hook-up wiring. The reduction of wires and connectors subtracts substantial bulk and eliminates their role in behaving as EMI (electro-magnetic interference) antennas. A shared knowledge by each motor controller of the state of all the motors in the system at 500 Hz also allows parallel processing of higher-level kinematic matrix calculations.

Townsend, William T.↗