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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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NASA NTRS1991

Thermal design of the Cosmic Background Explorer cryogenic optical assembly

The Cosmic Background Explorer (COBE) is a satellite which is designed to study the 3-K cosmic background radiation. Two cryogenic instruments and a common support structure comprise the Cryogenic Optical Assembly (COA). In order to make definitive measurements of the low-energy FIR radiation, the temperature of the COA must be maintained below 3 K. Temperature control of the COA elements is achieved by the use of a superfluid helium dewar. The thermal design also minimizes power dissipation, transient operational effects, and thermal gradients within the COA. This is accomplished by isolating selected components and heat-sinking others to various locations on the cryogen tank. The thermal design was developed primarily through analysis. Analytical models were created to perform parametric design studies. Ground testing was performed to correlate the thermal models and validate the thermal design. Both test and flight data confirmed that all design requirements were either met or exceeded.

Mosier, Carol L.↗

NASA NTRS1989

Pressure drop and He II flow through fine mesh screens

Fluid acquisition systems for He II transfer devices will utilize gallery arms to ensure that the fluid encounters the pump inlet. In near term experiments such as Superfluid Helium on Orbit Transfer (SHOOT), the preferred configuration consists of several rectangular channels which have one side made from a Dutch weave stainless steel screen having 325 x 2300 wires per inch. The effective pore diameter for this screen is about 5 microns. The present paper reports on measurements of pressure drop across a screen when it is subjected to a flow of liquid helium. The experiment measures the time rate of change of the level in two different helium reservoirs connected by a screen-blocked channel. Results with normal helium are compared with predictions based on the Armour-Cannon (1968) equations. The He II data show considerable deviation from the classical result. A discussion of the He II pressure drop results in terms of two fluid hydrodynamics is included.

Maddocks, J. R.↗

NASA NTRS1990

Thermal behavior of the SHOOT gallery arm

The planned Superfluid Helium On-Orbit Transfer (SHOOT) experiment will show the feasibility of resupplying orbiting facilities with liquid helium. The SHOOT experiment, designed for transfer rates of 300 to 800 liters/hr, will use a thermomechanical pump and four screen covered flow channels for fluid acquisition. Cavitation and thermal behavior was examined in ground based tests of the pump and of a full sized channel. A model for estimating the temperature profile at the pump inlet is presented. Large temperature increases in this region can significantly degrade the performance of the fountain pump.

Nissen, J. A.↗

NASA NTRS1990

Advances in cryogenic engineering. Vols. 35A & 35B - Proceedings of the 1989 Cryogenic Engineering Conference, University of California, Los Angeles, July 24-28, 1989

The book presents a review of literature on superfluid helium, together with papers under the topics on heat and mass transfer in He II; applications of He II for cooling superconducting devices in space; heat transfer to liquid helium and liquid nitrogen; multilayer insulation; applications of superconductivity, including topics on magnets and other devices, magnet stability and coil protection, and cryogenic techniques; and refrigeration for electronics. Other topics discussed include refrigeration of superconducting systems; the expanders, cold compressors, and pumps for liquid helium; dilution refrigerators; magnetic refrigerators; pulse tube refrigerators; cryocoolers for space applications; properties of cryogenic fluids; cryogenic instrumentation; hyperconducting devices (cryogenic magnets); cryogenic applications in space science and technology and in transportation; and miscellaneous cryogenic techniques and applications.

Fast, R. W.↗

NASA NTRS1990

Mission optimization of the Space Infrared Telescope Facility

The Space Infrared Telescope Facility (SIRTF) mission based on a cryogenically cooled telescope is described. The SIRTF makes it possible to perform background limited measurements with three focal plane instruments in the wavelength range 2-700 microns over the entire celestial sphere for at least five years. A telescope performance limited by the natural astrophysical background between 2 to 300 microns is achieved by using a superfluid helium cryogenic system for maintaining the forebaffle temperature below 8 K. The attitude control system based on Extreme Ultra-Violet Explorer reaction wheels meets the large and small angle slew requirements and provides 0.15 arc sec pointing stability. The present HEO baseline configuration has a mass of 4370 kg. The future Titan IV/Centaur launch capability to 100,000 km for a SIRTF-sized payload is at least 5770 kg.

Brooks, Walter F.↗

NASA NTRS1990

The SHOOT cryogenic components - Testing and applicability to other flight programs

Cryogenic components and techniques for the superfluid helium on-orbit transfer (SHOOT) flight demonstration are described. Instrumentation for measuring liquid quantity, position, flow rate, temperature, and pressure has been developed using the data obtained from the IRAS, Cosmic Background Explorer, and Spacelab 2 helium dewars. Topics discussed include valves and burst disks, fluid management devices, structural/thermal components, instrumentation, and ground support equipment and performance test apparatus.

Dipirro, Michael J.↗

NASA NTRS1992

Space Infrared Telescope Facility mission and cryogenic design

The Space Infrared Telescope Facility is the last of the Great Observatory missions. It is presently scheduled for launch in 2001. The mission will study the infrared spectrum from 2 to 1200 microns with three imaging and spectral instruments. The observatory will have a 5 year lifetime and will be placed in a 100,000 km earth orbit. The cryogenic system is based on a 4000 I superfluid helium cryostat. The mission and the cryogenic system are described, and the cryogenic technology issues are discussed.

Mason, P. V.↗

NASA NTRS1991

Welding in space and the construction of space vehicles by welding; Proceedings of the Conference, New Carrollton, MD, Sept. 24-26, 1991

The present conference discusses such topics in spacecraft welding as the NASA Long Duration Exposure Facility's evidence on material properties degradation, EVA/telerobotic construction techniques, welding of the superfluid helium on-orbit transfer flight demonstration tanks and hardware, electron-beam welding of aerospace vehicles, variable-polarity plasma arc keyhole welding of Al, aircraft experiments of low-gravity fusion welding, flash-butt welding of Al alloys, and a computer-aided handbook for space welding fabrication. Also discussed are the welded nozzle extension for Ariane launch vehicles, the existence of on-orbit cold-welding, structural materials performance in long-term space service, high-strength lightweight alloys, steels, and heat-resistant alloys for aerospace welded structures, the NASA-Goddard satellite repair program, and the uses of explosion welding and cutting in aerospace engineering.

Source record↗

NASA NTRS1991

SIRTF stray light analysis

The Space Infrared Telescope Facility (SIRTF) is a 1-meter cryogenic infrared telescope. Stray light is kept below the natural background by restrictions on sun, Earth, and moon off-axis angles; by conservative baffle design; by the use of advanced diffuse black coatings; and by superfluid helium cooling. The aperture stop is located at the primary mirror rather than at the secondary mirror to increase the aperture and reduce the central obscuration. Stray light from off-axis sources is greater with the aperture stop at the primary than with the aperture stop at the secondary, but the modulation of the signal produced by tilting of the secondary mirror for chopping is less. Stray light from telescope thermal emission is lower with the aperture stop at the primary.

Elliott, David G.↗

NASA NTRS1992

Conceptual thermal design and analysis of a far-infrared/mid-infrared remote sensing instrument

This paper presents the conceptual thermal design and analysis results for the Spectroscopy of the Atmosphere using Far-Infrared Emission (SAFIRE) instrument. SAFIRE has been proposed for Mission to Planet Earth to study ozone chemistry in the middle atmosphere using remote sensing of the atmosphere in the far-infrared (21-87 microns) and mid-infrared (9-16 microns) spectra. SAFIRE requires that far-IR detectors be cooled to 3-4 K and mid-IR detectors to 80 K for the expected mission lifetime of five years. A superfluid helium dewar and Stirling-cycle cryocoolers provide the cryogenic temperatures required by the infrared detectors. The proposed instrument thermal design uses passive thermal control techniques to reject 465 watts of waste heat from the instrument.

Roettker, William A.↗

NASA NTRS1991

A liquid/gas phase separator for He-I and He-II

A liquid/gas phase separator has been developed which separates both liquid He-I and He-II from their vapor. The phase separator was designed for the Superfluid Helium On Orbit Transfer (SHOOT) Flight Demonstration both to cool the liquid He after launch (at temperatures between 2.8 and 4.3 K) to the operating temperature of 1.4 K and as a low rate vent on orbit to maintain operating temperature. The phase separator is made of high-purity copper disks held apart by 6 micron Kevlar fibers. It works on the principle of conducting heat from within the dewar to vaporize liquid as it is throttled in the slits to efficiently cool the remaining liquid. Laboratory tests have demonstrated perfect phase separation for both He at its saturated vapor pressure from 1.2 to 4.3 K and for He-II at 2.13 K at pressures from 4.6 to 112 kPa. The performance of this phase separator during lab testing as well as expected performance in space is discussed.

Shirron, P. J.↗

NASA NTRS1991

Thermal behavior of the SHOOT gallery arm

Nissen, J. A.↗

NASA NTRS1991

The X-ray Spectrometer - A cryogenic instrument on the Advanced X-ray Astrophysics Facility

The X-ray Spectrometer (XRS) is an instrument on the Advanced X-ray Astrophysics Facility (AXAF), the third of NASA's Great Observatories scheduled for launch in 1998. The XRS detectors have a resolution of approximately 10 eV over the range 0.3 - 10 keV. To achieve this resolution, the detectors are maintained at or below 0.1 Kelvin using an adiabatic demagnetization refrigerator inside a superfluid helium dewar. In addition, split-Stirling-cycle mechanical coolers are used to extend the anticipated on-orbit helium lifetime to a minimum of 4 years. This paper describes the challenges of developing this hybrid cryogenic system and presents an overview of the current design of the system.

Breon, Susan R.↗

NASA NTRS1991

Design of the cryogenic system for the SAFIRE instrument

One of the primary goals of the NASA Mission to Planet Earth is to improve understanding of the ozone chemistry of the atmosphere over an extended period of time. The Spectroscopy of the Atmosphere using Far Infrared Emission (SAFIRE) instrument is being developed to conduct, for the first time, global measurements of the key ozone chemistry constituents in both the mid- and far-infrared spectral regions. Such remote, long-term observations are made possible by the recent development of compact long-life hybrid cryogenic dewars which are necessary to cool the sensitive detectors to the 3-4 K range. The success of this hybrid concept is based on the use of long-life Stirling cycle cryocoolers to intercept parasitic heat from the internal radiation shields of the superfluid helium dewar. Extensive system trade studies are required to optimize the mass, power, and lifetime of these space-borne cryogenic systems. The SAFIRE Cryogenic Subsystem is described, including the thermal performance trades leading to the chosen system configuration and the important dewar/cryocooler interface issues.

Lee, J. H.↗

NASA NTRS1994

Peculiar Behavior of He II Disturbances due to Sloshing Dynamics Driven by Jitter Accelerations Associated with Slew Motion in Microgravity

The mathematical formulation of Dewar container sloshing dynamics when partially filled with superfluid liquid He 11 driven by the gravity jitter acceleration associated with slew motion in a microgravity environment is studied. Numerical computation of the sloshing dynamics is based on the non-inertia container bound co-ordinate, and solving time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. This study discloses the capillary effect of the sloshing dynamics governing the liquid-vapour interface fluctuations driven by the gravity jitter acceleration associated with slew motion, which affects the stability of the fluid system in a microgravity environment. The peculiar behaviour of superfluid helium when reacting to the sloshing dynamics driven by the gravity jitter acceleration associated with slew motion in a microgravity environment is also investigated.

Hung, R. J.↗

NASA NTRS1999

Large-Scale Sakharov Condition

Recent far-reaching theoretical results have used the quantum vacuum noise as a fundamental electromagnetic radiation field to derive a frequency (w) -dependent version of Newton's gravitational coupling term, G(w). This paper reconciles the cutoff frequency with the observed cosmological constant, then briefly puts forward a realizable laboratory test case in the 10-100 Mhz frequency range. One analogy is drawn between the classical vacuum energy experiments with attraction between two closely spaced plates (Casimir cavity) and the arbitrarily dense material boundaries possible in Bose condensates, such as irradiation at Mhz frequencies of superfluid helium or superconductors.

Noever, David A.↗

NASA NTRS1999

T(sub lambda) Depression by a Heat Current Along the lambda-Line

We report measurements of the depression of the superfluid transition temperature by a heat current (1 less than or = Q less than or = 100 microW/sq cm) along the lambda-line (SVP less than or = P less than or = 21.6 bar). At P = 21.6 bar, measurements were also performed in a reduced gravity (0.2g). Experimental results show that the pressure dependence of the depression and the gravity effect on the measurements are small, in qualitative agreement with theoretical predictions. Keywords: superfluid helium; Lambda transition; heat current

Liu, Yuanming↗

NASA NTRS2000

Measurement of the Heat Capacity of He-II Under a Heat Current Near the Lambda Transition

We present preliminary measurements of the heat capacity of superfluid helium-4 under an applied heat current near the lambda transition. The calorimeter is a standard cylindrical thermal conductivity cell with a 0.6 mm gap between two copper endplates. The sidewall is made of stainless steel. A heat current density in the range of 1 to 4 microW/sq cm is applied through the helium sample while a pulse method is used to measure the heat capacity. Temperature changes are recorded with high-resolution thermometers (HRTs) located on the top and bottom endplates. Corrections are made to the readings of the HRTs to account for the Kapitza boundary resistance and the anomalous Kapitza boundary resistance. After the corrections, both the top and the bottom HRTs. give the same heat capacity values. The heat capacity is found to be much larger than the prediction of recent theories. We also plotted our data on a scaled plot to test the prediction of scaling by the theories. The result and its interpretation will be presented. The cell height was deliberately made to be thin to reduce the effects of gravity. Nonetheless, gravity is expected to have significant effects on the heat capacity data in the temperature range of our measurement. A space experiment would remove this unwanted gravity effect and allow the true physics to be examined. Moreover, in the absence of gravity, a deeper cell can be used allowing HRTs to be mounted on to the sidewall providing direct measurements of the helium temperature, unaffected by the anomalous Kapitza boundary resistance.

Harter, Alexa W.↗