Engineering topics
Publications and source records attributed to Sherman, A..
Magnetic bearings and noncontacting seals let cooler operate unattended at 65 K for more than 3 years. New cooler uses magnetic bearings, small piston/cylinder clearance seals, and linear motors. Cooler consists of compression and expansion sections connected end-to-end. Compression section houses reciprocating hollow piston driven by linear motor.
In 1979, a project leading to the development of a Stirling type cryogenic refrigerator for spaceborne application was initiated. The refrigerator is to generate five watts of net cooling at a temperature of 65 K. An operation without maintenance for a period of five years is required. A novel approach was selected for meeting the life requirement, taking into account an electromagnetic suspension of the moving parts. The fabrication of the hardware has now been completed and the performance of the refrigerator has been measured. The present paper provides a short review of the Stirling cycle, a description of the refrigerator design, and a summary of the test results. The new refrigerator configuration contains four major features, including a purely rectilinear drive, magnetic bearings, clearance seals, and all metal/ceramic working space surfaces. The displacer and the piston are supported and guided by magnetic bearings. The magnetic bearing consists of a set of electromagnetic actuators and radial position transducers.
Projected NASA needs in spaceborne cryogenic systems and recent results of NASA cryogenic cooling technology efforts in infrared astronomy, X-ray astronomy, gamma ray astronomy, liquid helium and space stations are discussed.
Catalyst speeds conversion, increasing capacity of solid hydrogen cooling system. In radial-flow catalytic converter, para-hydrogen is converted to equilibrium mixture of para-hydrogen and ortho-hydrogen as it passes through porous cylinder of catalyst. Addition of catalyst increases capacity of hydrogen sublimation cooling systems for radiation detectors.
The cooling capacity of a solid hydrogen cooling system is significantly increased by exposing vapor created during evaporation of a solid hydrogen mass to a catalyst and thereby accelerating the endothermic para-to-ortho transition of the vapor to equilibrium hydrogen. Catalyst such as nickel, copper, iron or metal hydride gels of films in a low pressure drop catalytic reactor are suitable for accelerating the endothermic para-to-ortho conversion.
A long lifetime Stirling cycle cryogenic cooler particularly adapted for space applications is described. It consists of a compressor section centrally aligned end to end with an expansion section, and respectively includes a reciprocating compressor piston and displacer radially suspended in interconnecting cylindrical housings by active magnetic bearings and has adjacent reduced clearance regions so as to be in noncontacting relationship therewith and wherein one or more of these regions operate as clearance seals. The piston and displacer are reciprocated in their housings by linear drive motors to vary the volume of respectively adjacent compression and expansion spaces which contain a gaseous working fluid and a thermal regenerator to effect Stirling cycle cryogenic cooling.
At the 1979 Cryogenic Engineering Conference, attention was given to conceptual designs of spaceborne cryogenic refrigeration systems which can provide long-term, unattended operation. Since that time, efforts have continued to translate one of those concepts into an engineering model. The present investigation is concerned with a refrigerator which was designed to generate 5 W of cooling power at a temperature of 65 K. The compression heat of the refrigerator is dissipated at a temperature of 300 K, and the output of the system is to be maintained reliably for a period of five years or longer. The refrigerator design is based on the Stirling cycle, which has an ideal efficiency equal to that of the Carnot cycle. Attention is given to some background information concerning a cryogenic refrigerator, the design of the refrigerator components, and the development status. The magnetic bearings and the linear motors have been tested at the component level.
Cryogenic cooling is employed for an increasing number of space instruments. Cryogenic cooling is needed to provide the required detector response, reduce preamplifier noise, and/or reduce background radiation. Cryogenic cooling is required by instruments employed for applications missions, gamma-ray and X-ray astronomy, cosmic ray measurements, space surveillance, IR astronomy, relativity measurements, superconductivity devices, and basic research experiments. The cooling is provided with the aid of radiant coolers, stored solid cryogen coolers, stored liquid-helium coolers, mechanical coolers, He-3 coolers, adiabatic demagnetization, refrigeration, and higher temperature adsorption and magnetic systems. Radiant coolers will continue to find widespread application for low cooling-load/high-temperature situation. It is pointed out that a long-lifetime closed-cycle, mechanical cooler is one of the most critical space technological needs.
Low and ultra low temperature cryogenic cooler systems for future space missions include mechanical, solid cryogen, gas adsorption, superfluid helium, helium-3, and magnetic (adiabatic demagnetization) coolers. Operating lifetimes required vary from a few weeks for a Shuttle/Spacelab mission to as long as nine years for missions to the outer planets. Temperature requirements vary from tens to tenths of kelvin. At the higher temperature, cooling loads for detectors, instruments and associated shields may be as high as 15 watts. The general requirements for low and ultra low temperature and techniques that can be employed to achieve these temperatures at expected heat loads are discussed. The NASA Centers involved in the R & T efforts and the type of cooler systems on which they are focusing their effort are considered as well as the thrust of R & T effort for each cooler type. Projected missions that will use the technology are identified.
The results of tests and studies to investigate the utilization of solid hydrogen for cooling of spacecraft instruments and sensors are presented. The results are presented in two sections; the first describing the tests in which an existing single stage solid cooler was filled and tested with solid hydrogen and the second which describes the analysis and design of a catalytic converter which will be tested in the vent line of the cooler.
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.
A new approach to the development of a 3- to 5-year lifetime Stirling cycle refrigerator for space is described. The reciprocating components would be driven directly by linear motors. There would be no contact between the moving components and the machine housing or motor during operation. The noncontact operation can be achieved either by magnetic or gas bearings and clearance seals. Consequently, two major contractual efforts are underway, one to develop the magnetic-bearing cooler and the other to develop the gas-bearing machine. The coolers are required to have a 5-W capability at 65 K and to be dynamically balanced. The results of the major contractor phase 1 design definition studies and component testing are discussed. Both the gas-bearing and magnetic-bearing coolers show promise for achieving the 3- to 5-year lifetime goal.
A study has been conducted to determine the utility and characteristics of a solid cryogen cooler which could meet a variety of instrument and mission requirements. The cooler consists essentially of two stages of solid cryogen and two cooled shields. The inner shield is thermally grounded to the secondary (warmer) cryogen and provides a low temperature boundary around the colder primary stage, while the outer shield reduces the heat loads upon the secondary cryogen. The baseline design provides cooling of approximately 1 watt over the temperature range 60-100 K, 0.5 watts from 15 to 60 K, and 0.2 watts from 8 to 15 K for a one-year lifetime. For low cooling loads (0.1 W) and with use of an optional cooled shield, cooling lifetimes of 8 years are possible.
Preliminary design studies were performed for a multi-mission solid cryogen cooler having a wide range of application for both the shuttle sortie and free flyer missions. This multi-mission cooler (MMC) is designed to be utilized with various solid cryogens to meet a wide range of instrument cooling from 10 K (with solid hydrogen) to 90 K. The baseline cooler utilizes two stages of solid cryogen and incorporates an optional, higher temperature third stage which is cooled by either a passive radiator or a thermoelectric cooler. The MMC has an interface which can accommodate a wide variety of instrument configurations. A shrink fit adapter is incorporated which allows a drop-in instrument integration. The baseline design provides cooling of approximately 1 watt over a 60 to 100 K temperature range and about 0.5 watts from 15 to 60 K for a one year lifetime. For low cooling loads and with use of the optional radiator shield, cooling lifetimes as great as 8 years are predicted.
Several disciplines requiring in-space cryogenic cooling are identified including high-energy, gamma-ray, and IR astronomy, relativity missions, and superconducting devices. Radiant coolers are limited in terms of temperature ranges and cooling loads. Other spacecraft cryogenic systems include stored solid cryogenic coolers using materials such as hydrogen, neon, argon, and methane. Two such cooler designs are described including one for the Nimbus F limb radiance inversion radiometer and one for the Nimbus G limb infrared monitoring of the atmosphere. Suggestions for increasing the performance of solid cryogenic coolers are made, such as a multimission cooler, a mechanical refrigerator, Stirling-cycle refrigerators, and Vuilleumier mechanized coolers. Techniques for obtaining cryogenic cooling in the milli-K range are identified as dilution refrigeration and adiabatic demagnetization.
The preliminary design of the cryogenic cooling system for the Cryogenic Cooled Limb Scanning Interferometer Radiometer (CLIR) instrument to be flown on the Atmospheric Magnetospheric Physics Satellite (AMPS) was studied. The top level trade studies were extensive due to the instrument requirement for cooling at three temperature levels as opposed to the two levels initially described for the instrument. Approximately 12 different combinations of cryogens were investigated. The basic lifetime requirement for the instrument was 30 days. However, studies were also conducted for a follow-up mission requiring a 1 year lifetime. The top level trades led to the selection of a single stage supercritical helium baseline.
On October 4, 1974, the International Heat Pipe Experiment was launched aboard a Black Brant sounding rocket from White Sands, New Mexico. The flight provided six min of near zero gravity during which a total of ten separate heat pipe experiments was performed. The fifteen heat pipes tested represent some of the latest American and European technology. This flight provided the first reported zero gravity data on cryogenic and flat plate vapor chamber heat pipes. Additionally, valuable design and engineering data were obtained on several other heat pipe configurations. The payload and several of its experiments are discussed.
Flight data from a 15.8 mm OD, 760 mm long, axial-groove, methane cryogenic heat pipe verified successful priming and operation during six min of zero-g time. The nominal power applied to the evaporator was 60-w for the first 60 sec of zero-g time, 14 w for the next 270 sec, and 25 w for the last 20 sec of flight. The heat pipe condenser was mounted into an aluminum heat sink which was cooled to 103 K at launch and increased in temperature to 128 K by the end of the flight. Ground test data obtained for the flight heat pipe, together with theoretical predictions, indicate a zero-g heat transport capability of 3500 to 4000 w-cm in the 100-125 K temperature range.