Engineering topics

Castles, Stephen H.

Publications and source records attributed to Castles, Stephen H..

11 records

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 NTRS1993

Germanium Resistance Thermometer For Subkelvin Temperatures

Improved germanium resistance thermometer measures temperatures as small as 0.01 K accurately. Design provides large area for electrical connections (to reduce electrical gradients and increase sensitivity to changes in temperatures) and large heat sink (to minimize resistance heating). Gold pads on top and bottom of germanium crystal distribute electrical current and flow of heat nearly uniformly across crystal. Less expensive than magnetic thermometers or superconducting quantum interference devices (SQUID's) otherwise used.

Castles, Stephen H.↗

NASA NTRS1992

Sub-Kelvin resistance thermometer

A device capable of accurate temperature measurement down to 0.01 K of a particular object is discussed. The device is comprised of the following: a heat sink wafer; a first conducting pad bonded near one end of the heat sink wafer; a second conducting pad bonded near the other end of the heat sink wafer; and an oblong doped semiconductor crystal such as germanium. The oblong doped semiconductor crystal has a third conducting pad bonded on its bottom surface with the oblong doped semiconductor crystal bonded to the heat sink wafer by having the fourth conducting pad bonded to the first conducting pad. A wire is bonded between the second and third conducting pads. Current and voltage wires bonded to the first and second conducting pads measure the change in resistance of the oblong doped semiconductor crystal; this indicates the temperature of the object whose temperature is to be measured.

Castles, Stephen H.↗

NASA NTRS1991

Magnetic shielding for a spaceborne adiabatic demagnetization refrigerator (ADR)

The Goddard Space Flight Center has studied magnetic shielding for an adiabatic demagnetization refrigerator. Four types of shielding were studied: active coils, passive ferromagnetic shells, passive superconducting coils, and passive superconducting shells. The passive superconducting shells failed by allowing flux penetration. The other three methods were successful, singly or together. Experimental studies of passive ferromagnetic shielding are compared with calculations made using the Poisson Group of programs, distributed by the Los Alamos Accelerator Code Group of the Los Alamos National Laboratory. Agreement between calculation and experiment is good. The ferromagnetic material is a silicon iron alloy.

Warner, Brent A.↗

NASA NTRS1990

Cryogenic on-orbit performance of the NASA Cosmic Background Explorer (COBE)

The initial thermal set-up and operation of the dewar for the COBE spacecraft are discussed, focusing on the helium vent system. During the initial cooldown of the dewar from 1.72 K to 1.41 K, short term temperature and pressure oscillations were observed in the porous plug and in the vent line. A detailed flow model describing these oscillations was developed. Attention is also given to the steady state operating mode for the instruments and the dewar, a comparison of the 'mission mode' temperature and power profile of the dewar with the predicted performance, the instrument and spacecraft events affecting the helium boil-off rate, and the methods for determining the helium flow rate and remaining mass measurements.

Volz, Stephen M.↗

NASA NTRS1989

Surface Tension Confines Cryogenic Liquid

New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

Castles, Stephen H.↗

NASA NTRS1989

The cryogenic subsystem for the X-ray spectrometer on the Advanced X-Ray Astrophysics Facility (AXAF)

The X-ray Spectrometer (XRS) instrument on the Advanced X-ray Astrophysics Facility (AXAF) will use X-ray detectors that operate at 0.1 K. The detectors will be maintained at 0.1 K by an Adiabatic Demagnetization Refrigerator (ADR) that operates inside a liquid helium dewar. The ADR rejects approximately 2 mW of heat to the stored liquid helium. With this low instrument heat load, the liquid helium dewar will have a long lifetime if the parasitic heat load on the helium from the surrounding warm facility is minimized. Spaceborne helium dewars typically use up to 3 vapor cooled shields to intercept the parasitic heat load. The XRS will add mechanical coolers to provide additional cooling to the outer vapor cooled shield. The cryogenic system consists of an ADR, a liquid helium dewar, mechanical coolers, and a thermal strap to connect the coolers to the dewar. The lifetime of the stored cryogen is calculated to be up to 5 years. This cryogenic system is described, with particular attention given to the dewar, mechanical cooler, and ADR design, testing, and trade studies. A breadboard ADR is presently being fabricated and tested. The status of the construction and testing of this breadboard will be described.

Castles, Stephen H.↗

NASA NTRS1988

Current developments in NASA cryogenic cooler technology

Cooler technologies that are being developed by NASA to meet the varying temperature and cooling power requirements of NASA instruments are described. In addition to providing the desired operating temperature and cooling power by stabilizing temperatures from room temperature down to 0.1 K or less, these coolers will have working lifetimes commensurate with the 10 to 15 year lifetime expected for major future NASA facilities. The types of coolers currently under development are discussed, including radiative coolers, solid cryogen coolers, surface tension confined liquid cryogen coolers, mechanical coolers, liquid helium dewars, He3 adsorption coolers, adiabatic demagnetization refrigerators, and dilution refrigerators.

Castles, Stephen H.↗

NASA NTRS1988

Development of a space qualified Surface Tension Confined Liquid Cryogen Cooler (STCLCC)

The Surface Tension Confined Liquid Cryogen Cooler (STCLCC), a new type of cryogenic cooler which is being developed by the NASA-GSFC for spaceflight payloads, is described. The STCLCC will be capable of maintaining instrumentation within the temperature range of 10-120 K and will allow liquid cryogens to be flown in space without the risk of liquid being entrained in the vent gas. A low-density open-cell material in the STCLCC acts as a 'sponge', with the surface tension trapping the liquid cryogen within its pores and keeping the liquid away from the cooler's vent during launch, zero-g operations, and landing. It is emphasized that the STCLCC concept is amenable to a wide variety of applications, whenever a passive low-cost cooler is required or when the on-orbit service of a cooler would increase a mission's lifetime.

Castles, Stephen H.↗

NASA NTRS1987

Cryogenics program overview

An overview of the cryogenics program of the Goddard Space Flight Center is given in viewgraph form. Goddard's role and the flight programs requiring cryogenics are outlined. Diagrams are given of the Cosmic Background Explorer, the Broad Band X-Ray Telescope, the Hubble Space Telescope, an adiabatic demagnetization refrigerator, a liquid cryogenic cooler for the Shuttle Glow Experiment, a liquid helium dewar, and the X-ray spectrometer on the Advanced X-Ray Astrophysics Facility.

Castles, Stephen H.↗

NASA NTRS1987

The Goddard Space Flight Center mechanical cooler program

The Philips Stirling Cooler Program will ensure that a cooler is available to meet NASA's needs in the 40 to 120K temperature range in the 1990's. The Creare turbomachinery based cooler may provide an improved cooler for the 40 to 120K range. The design of advanced multistage coolers for use down to 2K will begin in 1988. Requirements, the history of the Stirling cooler, features of the photoflight cooler, advantages of the Philips cooler, mechanical reliability, and potential advantages of the Creare reverse Brayton cycle cooler are presented in viewgraph form.

Castles, Stephen H.↗