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At least 199 records · Page 11

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NASA NTRS1993

Gamma ray spectrometer for Lunar Scout 2

We review the current status of the Los Alamos program to develop a high-resolution gamma-ray spectrometer for the Lunar Scout-II mission, which is the second of two Space Exploration Initiative robotic precursor missions to study the Moon. This instrument will measure gamma rays in the energy range of approximately 0.1 - 10 MeV to determine the composition of the lunar surface. The instrument is a high-purity germanium crystal surrounded by an CsI anticoincidence shield and cooled by a split Stirling cycle cryocooler. It will provide the abundance of many elements over the entire lunar surface.

Moss, C. E.↗

NASA NTRS1993

MOPITT - A gas correlation spectrometer for tropospheric Earth observations

MOPITT (Measurement of Pollution in the Troposphere) is an instrument that will fly on the EOS AM-1 Polar Orbiting Platform, to be launched in mid-1998. The instrument accurately measures the concentration of carbon monoxide (CO) and methane (CH4) gas in the troposphere, using novel and conventional gas correlation spectroscopy techniques. These techniques are used to measure both the column amount and the vertical profile of the two gases in the troposphere. The instrument is nadir viewing and has cross-track scanning ability. It measures upwelling IR radiation through the atmosphere in the 4.6-micron and 2.3-micron bands for CO detection, and 2.2-micron for CH4. The instrument performance is enhanced using Stirling cycle mechanical coolers to maintain the IR detectors at less than 100 K. MOPITT has a total of eight detector channels to measure the total column of atmospheric CH4 gas to a precision of 1 percent, and to measure CO profiles to a precision of 10 percent. The instrument is self-calibrating to ensure data validity using internal targets and an external cold space view.

Drummond, James R.↗

NASA NTRS1996

Oscillating-Flow Regenerator Test Rig: Hardware and Theory With Derived Correlations for Screens and Felts

A number of wire mesh and metal felt test samples, with a range of porosities, yield generic correlations for friction factor, Nusselt number, enhanced axial conduction ratio, and overall heat flux ratio. This information is directed primarily toward stirling cycle regenerator modelers, but will be of use to anyone seeking to better model fluid flow through these porous materials. Behind these results lies an oscillating-flow test rig, which measures pumping dissipation and thermal energy transport in sample matrices, and several stages of data-reduction software, which correlate instantaneous values for the above dimensionless groups. Within the software, theoretical model reduces instantaneous quantifies from cycle-averaged measurables using standard parameter estimation techniques.

Gedeon, D.↗

NASA NTRS1999

Demonstration of a Low Cost Cryocooler on a Long Duration Balloon Mission

NASA/GSFC has been evaluating the use of low cost Stirling cycle cryocoolers for aerospace applications since 1994. These include the M77B and M77C cryocoolers built by Sunpower Corporation. To date NASA has tested eight M77B and two M77C cryocoolers, with 8 additional M77C units now under construction. The intent of this work is to determine the flight worthiness of these cryocoolers. The Sunpower M77 coolers are candidate for use on the Ultra Long Duration Balloons presently under development by NASA. The flight on the Long Duration Balloon (LDB) in July 1998 represented an opportunity to test the cryocooler in the high altitude balloon environment in order to gain experience to prepare for possible opportunities on the Ultra Long Duration Balloon (ULDB) missions. The Long Duration Balloon is typically a 10 to 15 day mission. Typical ULDB missions might be as long as 100 days or more, and it is this duration which now forces many science groups to consider the use of cryocoolers in place of stored cryogens. This paper will present the basic design of the cryocooler experiment, and data acquired during the flight. The paper will also include a general perspective on the use of cryocoolers on future ULDB flights.

James, Edward F.↗

NASA NTRS1999

Design and Performance of the HESSI Cryostat

The High Energy Solar Spectroscopic Imager (HESSI) spacecraft, to be launched in July 2000, will be used to observe the Sun with the finest angular and energy resolutions ever achieved from a few keV to hundreds of keV. The spacecraft will use an array of nine germanium (Ge) detectors, each 7.1 cm in diameter and 8.5 cm long, operating at 75K. The detectors are mounted in a cryostat on a common cold plate, and cooled by a small Stirling-cycle cryocooler. This paper describes the design of the cryostat, special accommodations for the Ge detectors, interfaces with the cryocooler, and thermal performance of the engineering test unit.

Boyle, R.↗

NASA NTRS2000

Recent GRC Aerospace Technologies Applicable to Terrestrial Energy Systems

This paper is an overview of a wide range of recent aerospace technologies under development at the NASA Glenn Research Center, in collaboration with other NASA centers, government agencies, industry and academia. The focused areas are space solar power, advanced power management and distribution systems, Stirling cycle conversion systems, fuel cells, advanced thin film photovoltaics and batteries, and combustion technologies. The aerospace-related objectives of the technologies are generation of space power, development of cost-effective and reliable, high performance power systems, cryogenic applications, energy storage, and reduction in gas-turbine emissions, with attendant clean jet engines. The terrestrial energy applications of the technologies include augmentation of bulk power in ground power distribution systems, and generation of residential, commercial and remote power, as well as promotion of pollution-free environment via reduction in combustion emissions.

Kankam, David↗

NASA NTRS2001

6 K Cryocooler Program

The report summarizes experimental and theoretical work on an Oxford type Stirling Cycle mechanical precooler operating in the temperature range of 13-20 degrees Kelvin. It includes measurements of the thermal losses of particle regenerators made from lead, and rare earth and rare earth alloys in an operating three stage cryocooler. A 6 K hybrid cooler is designed using the technical information gathered on regenerator performance.

Gully, Willy↗

NASA NTRS2001

Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Skukuza and Mongu Sites

The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF (bidirectional reflection function) measurements were obtained over different natural surfaces and ecosystems in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS (Earth Observing System) satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 S, 31.5 E) and Mongu tower, Zambia (15.4 S, 23.3 E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 microns), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 microns). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 degree IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 degree viewing angle from the CAR.

Gatebe, C. K.↗

NASA NTRS2001

Airborne spectral Measurements of Surface-Atmosphere Anisotropy for Several Surfaces and Ecosystem over Southern Africa

The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF measurements were obtained over different natural surfaces and ecosystem in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 deg S, 31.5 deg E) and Mongu tower, Zambia (15.4 deg S, 23.3 deg E). Additional sites are also considered and include, Maun tower, Botswana (20.0 deg S, 23.5 deg E), Sowa Pan, Botswana (20.6 deg S, 26.2 deg E) and Etosha Pan, Namibia (19.0 deg S, 16.0 deg E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 micrometers), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 micrometers). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 deg IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 deg viewing angle from the CAR.

Gatebe, Charles K.↗

NASA NTRS2002

Micro-Scalable Thermal Control Device

A microscalable thermal control module consists of a Stirling cycle cooler that can be manipulated to operate at a selected temperature within the heating and cooling range of the module. The microscalable thermal control module is particularly suited for controlling the temperature of devices that must be maintained at precise temperatures. It is particularly suited for controlling the temperature of devices that need to be alternately heated or cooled. The module contains upper and lower opposing diaphragms, with a regenerator region containing a plurality of regenerators interposed between the diaphragms. Gaps exist on each side of each diaphragm to permit it to oscillate freely. The gap on the interior side one diaphragm is in fluid connection with the gap on the interior side of the other diaphragm through regenerators. As the diaphragms oscillate working gas is forced through the regenerators. The surface area of each regenerator is sufficiently large to effectively transfer thermal energy to and from the working gas as it is passed through them. The phase and amplitude of the oscillations can be manipulated electronically to control the steady state temperature of the active thermal control surface, and to switch the operation of the module from cooling to heating, or vice versa. The ability of the microscalable thermal control module to heat and cool may be enhanced by operating a plurality of modules in series, in parallel, or in connection through a shared bottom layer.

Matthew E. Moran↗

NASA NTRS2002

Airborne Spectral Measurements of Ocean Anisotropy during CLAMS

The Cloud Absorption Radiometer (CAR) aboard the University of Washington Convair CV-580 research aircraft obtained bidirectional reflectance-distribution function (BRDF) of Atlantic Ocean and Dismal Swamp between July 10 and August 2, 2001. The BRDF measurements (15 in total, 8 uncontaminated by clouds) obtained under a variety of sun angles and wind conditions, will be used to characterize ocean anisotropy in support of Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRDF models of the ocean. In this paper we present results of BRDF of the Ocean under different sun angles and wind conditions. The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 micron), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 micron). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 degree IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 deg. viewing angle from the CAR.

Gatebe, C. K.↗

NASA NTRS2002

Powering the Future

Stirling Technology Company (STC) developed the RG-350 convertor using components from separate Goddard Space Center and U.S. Army Natick SBIR contracts. Based on the RG-350, STC commercialized a product line of Stirling cycle generator sets, known as RemoteGen(TM), with power levels ranging from 10We to 3kWe. Under SBIR agreements with Glenn Research Center, the company refined and extended the capabilities of the RemoteGen convertors. They can provide power in remote locations by efficiently producing electricity from multiple-fuel sources, such as propane, alcohol, gasoline, diesel, coal, solar energy, or wood pellets. Utilizing any fuel source that can create heat, RemoteGen enables the choice of the most appropriate fuel source available. The engines operate without friction, wear, or maintenance. These abilities pave the way for self-powered appliances, such as refrigerators and furnaces. Numerous applications for RemoteGen include quiet, pollution-free generators for RVs and yachts, power for cell phone towers remote from the grid, and off-grid residential power variously using propane, ethanol, and solid biomass fuels. One utility and the National Renewable Energy Laboratory are evaluating a solar dish concentrator version with excellent potential for powering remote irrigation pumps.

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NASA NTRS2002

Operation of A Sunpower M87 Cryocooler In A Magnetic Field

The Alpha Magnetic Spectrometer-02 (AMS-02) is an experiment that will be flown as an attached payload on the International Space Station to detect dark matter and antimatter. It uses large superconducting magnets cooled with superfluid helium to bend the path of cosmic particles through a series of detectors, which then measure the mass, speed, charge, and direction of the particles. Four Sunpower M87N Stirling-cycle cryocoolers are used to extend the mission life by cooling the outer vapor-cooled shield of the dewar. The main magnet coils are separated by a distance of approximately 1 m and the coolers are located approximately 1.5 m from the center line of the magnet, where the field is as high as 925 gauss perpendicular to the cryocooler axis and 400 gauss along the cryocooler axis. Interactions between the applied magnetic field and the linear motor may result in additional forces and torques on the compressor piston. Motion of the compressor arid displacer pistons through the magnetic field spatial gradients will generate eddy currents. Additional eddy currents are created during magnet charge, discharge, and quench by the time-varying magnetic field. The results of tests to determine the magnitude of the forces, torques, and heating effects, as well as the need for additional magnetic shielding, are presented.

Breon, S. R.↗

NASA NTRS2002

Space Flight Qualification Program for the AMS-2 Commercial Cryocoolers

The Alpha Magnetic Spectrometer-02 (AMS-02) experiment is a state-of-the-art particle physics detector containing a large superfluid helium-cooled superconducting magnet. Highly sensitive detector plates inside the magnet measure a particle's speed, momentum, charge, and path. The AMS-02 experiment will study the properties and origin of cosmic particles and nuclei including antimatter and dark matter. AMS-02 will be installed on the International Space Station on Utilization Flight-4. The experiment will be run for at least three years. To extend the life of the stored cryogen and minimize temperature gradients around the magnet, four Stirling-cycle Sunpower M87N cryocoolers will be integrated with AMS-02. The cryocooler cold tip will be connected via a flexible strap to the outer vapor cooled shield of the dewar. Initial thermal analysis shows the lifetime of the experiment is increased by a factor of 2.8 with the use of the cryocooler. The AMS-02 project selected the Sunpower M87 cryocoolers and has asked NASA Goddard to qualify the cryocoolers for space flight use. This paper describes the interfaces with the cryocoolers and presents data collected during testing of the two engineering model cryocoolers. Tests include thermal performance characterization and launch vibration testing. Magnetic field compatibility testing will be presented in a separate paper at the conference.

Shirey, K. A.↗

NASA NTRS1986

Supercooling Refrigerator

A Goddard/Philips research project resulted in a refrigeration system which works without seals, lubricants or bearings. The system, originally developed to cool satellite-based scientific instruments, has an extensive range of potential spinoffs. It is called the Stirling Cycle Cryogenic Cooler and eliminates friction by using electronically controlled linear magnetic bearings. Mechanical failure, contamination are eliminated.

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NASA NTRS2003

MEMS Stirling Cooler Development Update

This presentation provides an update on the effort to build and test a prototype unit of the patented MEMS Stirling cooler concept. A micro-scale regenerator has been fabricated by Polar Thermal Technologies and is currently being integrated into a Stirling cycle simulator at Johns Hopkins University Applied Physics Laboratory. A discussion of the analysis, design, assembly, and test plans for the prototype will be presented.

Moran, Matthew E.↗

NASA NTRS2003

AMS-02 Cryocooler Baseline Configuration and Engineering Model Qualification Test Results

Four Sunpower M87N Stirling-cycle cryocoolers will be used to extend the lifetime of the Alpha Magnetic Spectrometer-02 (AMS-02) experiment. The cryocoolers will be mounted to the AMS-02 vacuum case using a structure that will thermally and mechanically decouple the cryocooler from the vacuum case while providing compliance to allow force attenuation using a passive balancer system. The cryocooler drive is implemented using a 60Hz pulse duration modulated square wave. Details of the testing program, mounting assembly and drive scheme will be presented. AMS-02 is a state-of-the-art particle physics detector containing a large superfluid helium-cooled superconducting magnet. Highly sensitive detector plates inside the magnet measure a particle s speed, momentum, charge, and path. The AMS-02 experiment, which will be flown as an attached payload on the International Space Station, will study the properties and origin of cosmic particles and nuclei including antimatter and dark matter. Two engineering model cryocoolers have been under test at NASA Goddard since November 2001. Qualification testing of the engineering model cryocooler bracket assembly is near completion. Delivery of the flight cryocoolers to Goddard is scheduled for September 2003.

Banks, Stuart↗

NASA NTRS2004

Free-Piston Stirling Convertor Controller Development at NASA Glenn Research Center

The free-piston Stirling convertor end-to-end modeling effort at NASA Glenn Research Center (GRC) has produced a software-based test bed in which free-piston Stirling convertors can be simulated and evaluated. The simulation model includes all the components of the convertor - the Stirling cycle engine, linear alternator, controller, and load. This paper is concerned with controllers. It discusses three controllers that have been studied using this model. Case motion has been added to the model recently so that effects of differences between convertor components can be simulated and ameliorative control engineering techniques can be developed. One concern when applying a system comprised of interconnected mass-spring-damper components is to prevent operation in any but the intended mode. The design mode is the only desired mode of operation, but all other modes are considered in controller design.

Regan, Timothy↗