[en] Future NASA deep-space missions will require radioisotope-powered electric generators that are just as reliable as current RTGs, but more efficient and of higher specific power (W/kg). Thermoacoustic engines can convert high-temperature heat into acoustic, or PV, power without moving parts at 30% efficiency. Consisting of only tubes and a few heat exchangers, these engines are low mass and promise to be highly reliable. Coupling a thermoacoustic engine to a low-mass, highly reliable and efficient linear alternator will create a heat-driven electric generator suitable for deep-space applications. Data will be presented on the first tests of a demonstration thermoacoustic engine designed for the 100-Watt power range.

[en] This chapter uses a two-phase model to analyze the transients of a gas adsorption compressor. The modeling of the adsorption process is based on complete thermal and mechanical equilibrium between the gaseous phase and the adsorbed gas phase. The theories and techniques that have been developed for a two-phase system are used to predict the pressure, the temperature and the mass flow transients in a gas sorption compressor. The analytical solutions are then compared with the performance of a laboratory gas adsorption compressor. A computer code was written to solve the governing equations, using a standard forward marching predictor-corrector method. It is found that while the analytical model overpredicts the pressure and the temperature transient, it predicts the general trend of the transient profile and the existence of the turning point

[en] The state of the art of cryocoolers for space-based electronics and sensors is reviewed. Coolers under consideration include flexure-bearing and magnetic-bearing type Stirling coolers, pulse tube coolers, Vuilleumier coolers, magnetocaloric refrigerators, closed cycle Joule-Thompson coolers, sorption refrigerators, and reverse Brayton cycle refrigerators. The compromises among these systems in terms of reliability, efficiency, size, vibration, and system interface are discussed. 50 refs

[en] Large transient pressure pulses, referred to as a helium hammer, which occurred in the transfer line of the main cryogenic tank during the development tests of the Infrared Astronomical Satellite, launched on January 25, 1983, are analyzed, and the measures taken to prevent a failure described. The modifications include an installation of a 2.3-liter surge tank upstream, and a back-up relief valve downstream, of a burst disk. The surge tank is designed to attenuate a 0.33-MPa pressure pulse at the inlet down to 0.092 MPa at the outlet. A mechanism of the pulse generation is suggested, which involves flashing and rapid recondensation of the small amount of liquid entering the warm section of a transition to room temperature

[en] The performance of pulse tube coolers is being studied in order to determine their suitability for development into long-life space coolers. Coolers based on the pulse tube phenomenon appear to be attractive for long-life space application because of their inherent simplicity. Single-stage and two-stage pulse tube test coolers have been designed and tested. In these early tests a single stage cooler has achieved a low temperature of 53 K while rejecting heat above 300 K. An unoptimized two-stage cooler has reached 26 K while rejecting heat above 300 K. Performance measurements for the coolers is presented. 15 refs

[en] The sensitivity of the gravity wave detector at the University of Regina is presently limited by the noise in the SQUID that is used to detect the currents generated in the quartz antenna. This SQUID has a noise temperature estimated to be 4x10^-2 K at the resonance frequency (8846 Hz) of the antenna. The authors discuss the improvement that could be expected by using a quantum limited DC SQUID. (Auth.)

[en] Magnetic pick-up transducers for high-Q gravitational wave antennas are studied. The sensitivities of two recently proposed devices are evaluated from a general point of view. A general treatment of these systems as two coupled oscillators is used. The noise properties of these devices, taking into account the reaction of the electronics back on the antennas and the measuring times, are determined. A modification of the systems to operate as mechanical impedance transformers is also discussed. A comparison of two recently proposed magnetic transducer schemes with a mechanical impedance transformer scheme is made

[en] At the University of Regina a gravity wave detector is being constructed, using in the present instance, a single crystal bar of quartz as antenna. The apparatus can accomodate metallic antennae as large as 250 Kg of Nb or, in turn, 100 Kg of Al. The several benefits of cooling the antenna are obtained by operating the experiment at low temperature. Though presently work is at 1 K and 4.2 K, the cryostat is designed to reach temperatures near 3 millikelvin using adiabatic demagnetization. The signal derived when the piezoelectric crystal vibrates is passed through a superconducting transformer to a low-noise SQUID amplifier. The authors present results that have been obtained in the past two years. (Auth.)

[en] The small High Efficiency pulse tube Cooler (HEC) cooler, that has been produced and flown on a number of space infrared instruments, was originally designed to provide cooling of 10 W @ 95 K. It achieved its goal with >50% margin when limited by the 180 W output ac power of its flight electronics. It has also been produced in 2 stage configurations, typically for simultaneously cooling of focal planes to temperatures as low as 35 K and optics at higher temperatures. The need for even higher cooling power in such a low mass cryocooler is motivated by the advent of large focal plane arrays. With the current availability at NGAS of much larger power cryocooler flight electronics, reliable long term operation in space with much larger cooling powers is now possible with the flight proven 4 kg HEC mechanical cooler. Even though the single stage cooler design can be re-qualified for those larger input powers without design change, we redesigned both the linear and coaxial version passive pulse tube cold heads to re-optimize them for high power cooling at temperatures above 130 K while rejecting heat to 300 K. Small changes to the regenerator packing, the re-optimization of the tuned inertance and no change to the compressor resulted in the increased performance at 150 K. The cooler operating at 290 W input power achieves 35 W@ 150 K corresponding to a specific cooling power at 150 K of 8.25 W/W and a very high specific power of 72.5 W/Kg. At these powers the cooler still maintains large stroke, thermal and current margins. In this paper we will present the measured data and the changes to this flight proven cooler that were made to achieve this increased performance