N92-22620 Report of the Sensor Cooler Technology Panel Ronald Ross, Panel Chair Jet Propulsion Laboratory, California Institute of Technology Members of the Sensor Cooler Technology Panel: S. Castles, NASA Goddard Space Flight Center N. Gautier, California Institute of Technology P. KJttel, NASA Ames Research Center J. Ludwigsen, Nichols Research (SDIO) R. Ross, Jet Propulsion Laboratory INTRODUCTION Cryogenic cooler performance is a critical system requirement for many space-based spectroscopy and imaging measurements. This is particularly true for measurements of weak signals, such as are typical for astrophysics missions, where it is often necessary to cool the focal-plane sensors and electronics to cryogenic temperatures in order to reduce focal-plane thermal noise sources below the signal levels to be measured. Among the key aspects in which further development in space cryocooler technology is required are the achievement of lower temperatures, larger heat loads, reduced vibration, and longer cooler lifetimes. The focus of the Sensor Cooler Technology Panel was an analysis of the cryogenic cooler performance required to meet the Astrotech 21 mission set science objectives. A list of the mission set specifications and the pacing cooler technologies is provided in Table I. After a careful review of the mission set, the panel identified four general types of missions where existing cooler technology is expected to be insufficient or marginal. The four categories are: • Long-life precision-pointing space telescope missions with observations at 2.5 to 10 llm. (HST II &III, NGST, Imag. Int.) • Long-life missions requiring significant (> 100 mW) cooling capacity in the 2 to 5 K temperature range for periods of up to 15 years. (SMIM, NGOVLBI, LDR, SMMI) • Long-life missions with subkelvin applications requiring ~ 10 _tW of cooling at 0.1 K with heat sinking to 2 K. (SIRTF, SMIM, LDR, SMMI, AXAF) • A number of missions which require low- vibration, high-capacity coolers in the 65 K temperature range. (GRSO, NAE) The panel also reviewed current state-of-the-art capabilities and future potential of the various cryocooler technologies which either have been flown previously or are being considered for space applications. Figure 1 shows a compilation of the primary operating regions for these technologies in terms of the cooling temperature and cooling power ranges they can each be expected to offer. Working from the mission requirements in the context of this analysis of space cryocooler capabilities, the panel developed a four-element technology development strategy to meet the identified challenges of the Astrotech 21 mission set. The four areas recommended for development are: • Long-life vibration-free refrigerator development for 10 - 20 K and 65 - 80 K temperature ranges for use on missions requiting precision pointing. • 2 - 5 K mechanical refrigerator development for future long life infrared fiR) and submillimeter (submm) missions with lifetimes exceeding super-fluid He storage tank holding times. • Flight testing of emerging prototype refrigerators to determine feasibility before they are committed to large, high-visibility astrophysics missions. • R&D of promising backup technologies to mitigate against failure of one or more of the baseline technologies. The specific performance requirements in these four areas, the missions impacted, and the associated technology freeze dates are summarized in Table II. The items have not been prioritized. This report describes the panel findings and the recommended development plan to achieve the required capabilities on the necessary time scales. Note that requirements for other areas of space missions were not included in the considerations. The recommendations are restricted to issues of relevance to the specific missions and science objectives of the Astrotech 21 mission set described earlier in this Proceedings. 68 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by NASA Technical Reports Server
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
N92-22620
Report of the Sensor Cooler Technology Panel
Ronald Ross, Panel Chair
Jet Propulsion Laboratory, California Institute of Technology
Members of the Sensor Cooler Technology Panel:S. Castles, NASA Goddard Space Flight CenterN. Gautier, California Institute of TechnologyP. KJttel, NASA Ames Research CenterJ. Ludwigsen, Nichols Research (SDIO)R. Ross, Jet Propulsion Laboratory
INTRODUCTION
Cryogenic cooler performance is a criticalsystem requirement for many space-basedspectroscopy and imaging measurements. This isparticularly true for measurements of weak signals,such as are typical for astrophysics missions, where itis often necessary to cool the focal-plane sensors andelectronics to cryogenic temperatures in order toreduce focal-plane thermal noise sources below thesignal levels to be measured. Among the key aspectsin which further development in space cryocoolertechnology is required are the achievement of lowertemperatures, larger heat loads, reduced vibration, andlonger cooler lifetimes.
The focus of the Sensor Cooler TechnologyPanel was an analysis of the cryogenic coolerperformance required to meet the Astrotech 21mission set science objectives. A list of the mission
set specifications and the pacing cooler technologiesis provided in Table I. After a careful review of themission set, the panel identified four general types ofmissions where existing cooler technology isexpected to be insufficient or marginal. The fourcategories are:
• Long-life precision-pointing space telescopemissions with observations at 2.5 to 10 llm.(HST II &III, NGST, Imag. Int.)
• Long-life missions requiring significant (> 100mW) cooling capacity in the 2 to 5 Ktemperature range for periods of up to 15 years.(SMIM, NGOVLBI, LDR, SMMI)
• Long-life missions with subkelvin applicationsrequiring ~ 10 _tW of cooling at 0.1 K with heatsinking to 2 K. (SIRTF, SMIM, LDR, SMMI,AXAF)
• A number of missions which require low-vibration, high-capacity coolers in the 65 Ktemperature range. (GRSO, NAE)
The panel also reviewed current state-of-the-artcapabilities and future potential of the variouscryocooler technologies which either have been flownpreviously or are being considered for spaceapplications. Figure 1 shows a compilation of theprimary operating regions for these technologies interms of the cooling temperature and cooling powerranges they can each be expected to offer. Workingfrom the mission requirements in the context of thisanalysis of space cryocooler capabilities, the paneldeveloped a four-element technology developmentstrategy to meet the identified challenges of theAstrotech 21 mission set. The four areas
recommended for development are:
• Long-life vibration-free refrigerator developmentfor 10 - 20 K and 65 - 80 K temperature rangesfor use on missions requiting precision pointing.
• 2 - 5 K mechanical refrigerator development forfuture long life infrared fiR) and submillimeter(submm) missions with lifetimes exceedingsuper-fluid He storage tank holding times.
• Flight testing of emerging prototype refrigeratorsto determine feasibility before they are committedto large, high-visibility astrophysics missions.
• R&D of promising backup technologies tomitigate against failure of one or more of thebaseline technologies.
The specific performance requirements in thesefour areas, the missions impacted, and the associatedtechnology freeze dates are summarized in Table II.The items have not been prioritized. This reportdescribes the panel findings and the recommendeddevelopment plan to achieve the required capabilitieson the necessary time scales. Note that requirementsfor other areas of space missions were not included inthe considerations. The recommendations are
restricted to issues of relevance to the specificmissions and science objectives of the Astrotech 21mission set described earlier in this Proceedings.
68
https://ntrs.nasa.gov/search.jsp?R=19920013377 2020-03-24T07:09:16+00:00Zbrought to you by COREView metadata, citation and similar papers at core.ac.uk
Long-life precision pointing space telescopetype missions with measurements in the near to midIR range require vibration-free coolers with - 1 W ofcooling capacity in the 65 to 80 K temperature rangefor use with 2.5 grn detectors, and with - 20 mW ofcapacity in the 10 to 20 K range for use with 10 lamdetectors. The critical issues are the requirements forno vibration and long life. The requirement for novibration is expected to exclude present Stirlingcooler technologies being developed for Earth
Observing System (Eos) missions. Similarly,typical lifetimes of 10 - 15 years also render the useof stored cryogens inappropriate (not cost effective).Thus new approaches will be needed to meet themission requirements.
B. Development Plan
The panel recommends that NASA develop andqualify one or two vibration-free coolers in the twokey temperature ranges (10 to 20 K, and 65 to 80 K),for use on space-telescope type missions. Candidate
technologies include sorption refrigerators (Fig. 2),and high-speed turbo-Brayton systems. Both of these
technologies have demonstrated technical feasibilityin recent lab breadboard tests, but must be carried to
the point of engineering model construction and lifetesting before they can be proposed for flightapplications. These technologies are ready forengineering model development, but remain unfundedat this time. An appropriate development schedule isshown in Table III.
MECHANICAL REFRIGERATORS FOR 2TO5K
A. Technical Assessment
Long-life IR and submm missions requiresignificant (> 100 roW) cooling capacity in the 2 to 5K temperature range for periods of up to 15 years.This type of mission considerably exceeds (by morethan a factor of 10) the cooling capacity beingdeveloped for SIRTF (see Figs. 3 to 5), and isprobably unrealistic (not cost effective) for a storedcryogen system.
69
10
:1= 1t_
i!1O.1
O
(0 .01Z
.,IOO£3 .OOl
.0001
5% CARNOT REFRIGERATOR COP, watts/watt
60,000 10,000 3000 1000
0.1 1 10
COOLING TEMPERATURE, OK
30t
N_./H2_
100 40
& _ i | z i z •
100
-N2/O2J-T
Figure I. A compilation of the primary operating regions for various cryocooler technologies in terms of thecooling temperature and cooling power ranges they can each be expected to offer. Included for comparison are theoperating ranges required for various detector types.
INCONEL SORBENT
HEATSWITCHPORT
Xe _ |,
Figure 2, Schematic diagram of a concentric sorption compressor, a candidate for vibration-free cooling at 65 K.
70
Table II. Technology Areas Recommended for Development
Develop new approachesincluding sorption andturbo-Brayton
Qualify best option(s)
lab breadboardtests demonstrated
feasibility
Program ProgramDates Size
engineering model 91 - 93 Moderateand life testing
Space qualified model:for HST & NAE 93-94 Large
for NGST & GRSO 95 - 00 Large
B. Development Plan
It is recommended that one or two long-life low-vibration mechanical refrigerators be developed andqualified to provide 2 to 5 K cooling for future LDR-type applications that are beyond the reach of launch-vehicle limited SFHe Dewars such as used on SIRTF.
A bali park target of less than 1 kW input power and10 - 20 mW of cooling at 2 K together with 50 to100 mW of additional cooling at 4 - 5 K wasidentified as about right. This distribution of coolingshould be carefully reviewed in light of thethermodynamic inefficiency and immaturity ofhardware for providing mechanical cooling at 2 K; thecapacity at 2 K should be selected to just meet thosescience objectives requiring this temperature. Becauseof the vastly improved efficiency of providing coolingabove the liquefaction point of He at 4 K, the sciencecommunity should strive to meet as many objectivesas possible using temperatures in the 4 to 5 K rangeor higher.
A variety of candidate technologies exist for
providing 4 to 5 K mechanical cooling (Fig. 6).
These include: three-stage turbo-Brayton systems,closed-cycle He Joule-Thomson Q-T) refrigeratorswith upper stages, 4 K Stifling plus upper stages, andmagnetic refrigerators with upper stages. Two-stageStirling, pulse tube, and turbo-Brayton systems arecandidate upper-stage technologies. Of thesetechnologies for attaining 4 - 5 K, the three-stageturbo-Brayton is the most mature, having reached theprototype stage under DoD/SDIO funding. Becauseof the diversity of technical approaches, a multiple-path development approach is recommended, withdown selection occurring after the definition of apreferred configuration. The proposed developmentschedule is summarized in Table IV.
Significant (x 10) expansion of superfluid HeDewar size and life performance beyond that forSIRTF was judged not to be a cost effective approachto meeting these most demanding Astrotech 21missions. However, the SFHe technology is thelogical choice for the smaller SIRTF-size missions.
71
EJECTABLEAPERTURE
COVER
/CRYOGEN
TANK
APERTURESHADE
SECONOARYmRROR
ASSEMBLY
TANK SUPPORTS
OUTER VACUUMHOUSING
SUPERFLUIDHELIUM TANK
VAPORCOOLEDSHIELDS
TERTIARY MIRRORASSEMBLY
FINEGU_ANCE
SENSOR
METERING PRIMARY MULTIPLECYLINDER AND MIRROR INSTRUMENT CHAMBERBARRELSAmE
Figure 3. Schematic cut-away view of the plans for the SIRTF telescope displaying the cryogenic Dewar assembly.
lOOO
E
a",<O.-I
I--
"I"
Z.1
k-
Z
lOO
lO
DEWAR (4000 liter)
SIRTF
_-BASELINE
3 4 5 6 7 8
LIFETIME, years
Figure 4. Plot of the instrument heat load that can be accommodated as a function of mission lifetime, assuming a4,000 liter cryogen Dewar, as is planned for SIRTF.
72
Plumbing(SKo, 1%) -.
Wires
(38Kg, 7%)
MLI(41.5Kg, 6%)
Aperture(9Kg, 2%)
Launch(27Kg, 5%)
\\
\,\
IRS, IRAC, MIPS
(Total = 19.7 mW)
Instruments
(182Kg, 33%)
Sec. Mirrol
(46Kg, 8%)
Straps FGS*(114.5Kg, 20%} (88Kg, 16%)
Figure 5. Breakdown of the heat load budget for a SIR'IF-like mission displaying the relative contributions ofdifferent system components. FGS refers to the fine guidance system, and MLI to the multilayer insulation.
Maturity level of various mechanical cryocooler technologies versus their temperature range of operation.
73
Table IV. Mechanical Refrigerators for 2 - 5 K
Technology Development Current ProgramTechnologlt Goals
Explore multiple approaches
Develop best option(s)
Prototype turbo-Bmyton2.5 W at 8.5 K
9 W at25 K80 W at 70 K
- 3 kW input power
Program ProgramDates Size
Feasibilityfor 2 - 5 K operation
long life, low vibration
93 - 96 Several small
10-20 mW at 2 K50-100 mW at4-5 K
long life, low vibration
96 - 00 Large
FLIGHT TESTING OF EMERGINGPROTOTYPE REFRIGERATORS
A. Technology Assessment
Because of the extreme challenges in achievinglong-life mechanical refrigerators, a significant needwas identified to qualify and flight test critical coolertechnologies before they are committed to large high-visibility astrophysics missions that demand very lowrisk of failure.
B. Development Plan
To this end, it is recommended that a programof advanced development and flight testing besupported to help bridge the technology maturity gapbetween present cooler research activities and thedemands of flight programs. As this time, 65 K low-vibration Stirling refrigerators and subkelvin adiabaticdemagnetization refrigerators (ADR) are technologiesin this category. The former are required for a numberof missions, including the gamma-ray missions,which need low-vibration, high-capacity coolers inthe 65 K temperature range. These applications willlogically be met by the class of low-vibrationStirling (Fig. 7) and turbo-Brayton coolers currentlyunder development for Eos and DOD, but not yetflight qualified. Subkeivin ADR systems are requiredfor long-life subkelvin applications associated withthe use of bolometers for IR and X-ray applications
which need ~ 10 _tW of cooling at 0.1 K with heatsinking at 2 K. Such refrigerators are underdevelopment (Fig. 8), but also need qualification andflight testing.
Other refrigerator technologies, as they reachthis stage of development, would also greatly benefitfrom a pathfinder qualification and debugging phase ina low-risk (Class D) experiment setting. The panelrecommends that this program be maintained at amoderate level throughout the development of newcooler capabilities required for Astrotech 21 missions,as indicated in Table V.
R&D OF PROMISING BACKUPTECHNOLOGIES
A. Technology Assessment
Although the above three program elements arenecessary to achieve technology readiness for the
Astrotech 21 mission set, it is not certain that theywill be sufficient, and the parallel development ofother promising backup technologies is stronglyadvised to mitigate against failure of one or more ofthe baseline technologies, and/or to take advantage ofenabling improvements in current technologies. This
is particularly relevant for large, high-visibilitymissions, such as many of these for astrophysicsresearch, for which it is desirable to reduce the risk offailure to a very low level.
Table V. Flight Testing of Emerging Prototype Refrigerators
Current Program Program Program [Technology Goals Dates Size INew research-grade Qualification and 93 - 03 Moderate
cooler technologies flight testing as
Class D experiments
Technology Development
Flight test experiments
74
ORI_!NAt. PA_[_
L,:._,'_O_ A_D WHITE P_-iOIOGt_APH
L
Figure 7. Photograph of 80 K Stirling Cooler developed by British Aerospace from a prototype constructed at
Oxford University. This cooler is currently being evaluated by JPL for Earth Observing Systems application.
Figure 8. Schematic of prototype adiabatic demagnetization refrigerator (ADR) planned to provide subkelvin coolingfor SIRTF bolometers.
75
B. Development Plan
With this concern in mind, the panelrecommends that a program be initiated to support anumber of promising backup technologies atrelatively low levels. Example backup technologiesthat are of interest for the Astrotech 21 mission setinclude:
• Technologies that would significantly reduceparasitic heat loads into SFHe Dewars.
The Sensor Cooler Technology Panel identifiedfour major areas in which technology developmentmust be supported in order to meet the systemperformance requirements for the Astrotech 21
mission set science objectives. These are, in short:
• Long-life vibration-free refrigerators• Mechanical refrigerators for 2-5 K
• Flight testing of emerging prototyperefrigerators
A development strategy and schedule wererecommended for each of the four areas.
Discussions between the cooler panel and otherworkshop panels also brought to light additionalissues which should be considered by space scientistsand detector instrument designers to optimize the totalsystem performance. There are natural break pointsin operating temperature for space coolertechnologies, such that the arbitrary selection of asensor temperature just below one of these points canresult in significant increases in cooler powerrequirements and in technical complexity, withconcomitant increases in demands on the mission
budget and in the risk of in-flight failure. Animportant break point for the Astrotech 21 missionset is at around 4 K, the liquefaction temperature ofHe. In addition, large cooling loads can be just asdemanding of cooler technology as operatingtemperature requirements. Consequently, there aresituations where it may be worthwhile sacrificingsome small amount of signal to noise, and allowingthe amplifier and/or readout electronics to operate at adifferent (higher) temperature than required for thesensors themselves, thereby reducing the heat load atthe lowest temperatures. Similarly, efforts toimprove thermal isolation technology, asrecommended by the Sensor Readout ElectronicsPanel, are also supported by this panel.
Table VI. R&D of Promising Backup Technologies
Technology Development Current Program Program ProgramTechnology Goals Dates Size
Approaches to reduce parasitic heatload into SFHe Dewars
Subkelvin coolers such as dilution
and 3He-4He Stifling technologies
Vibration-free approaches such asthermoelectric coolers
Low-vibration upper-stage coolerssuch as pulse-tube
Concepts Feasibility 93 - 98 Small
Concepts Feasibility 93 - 98 Small
Concepts Feasibility 93 - 98 Small
Concepts Feasibility 93 - 98 Small
76
APPENDIX A. SENSOR TECHNOLOGY WORKSHOP PANELS AND CHAIRS
X-Ray and Gamma-Ray Sensors Panel
Char: A. Szymkowiak, NASA Goddard Space
Flight Center
S. Collins, Jet Propulsion Laboratory
J. Kurfess, Naval Research Laboratory
W. Mahoney, Jet Propulsion Laboratory
D. McCammon, University of Wisconsin - Madison
R. Pehl, Lawrence Berkeley Laboratory
G. Ricker, Massachusetts Institute of Technology
Direct Infrared Sensors Panel
Chair: C. McCreight, NASA Ames Research Center
R. Bharat, Rockwell International Science Center
R. Capps, Jet Propulsion Laboratory
W. Forrest, University of Rochester
A. Hoffman, Hughes SBRC
H. Moseley, NASA Goddard Space Flight Center
R. McMurray, NASA Ames Research Center
M. Reine, Loral Infrared and Imaging Systems
P. Richards, University of California, Berkeley
D. Smith, Los Alamos National Laboratory
E. Young, University of Arizona
Sensor Readout Electronics Panel
Chair: E. Fossum, Jet Propulsion Laboratory
J. Carson, Irvine Sensors
W. Kleinhans, Valley Oak Semiconductor
W. Kosonocky, New Jersey Institute of Technology
L. Kozlowski, Rockwell International Science Center
A. Pecsalski, Honeywell SRC
A. Silver, TRW
A. Spieler, Lawrence Berkeley Laboratory
J. Woolaway, Amber Engineering
Ultraviolet and Visible Sensors Panel
Cha_: J.G. Timothy, Stanford University
M. Blouke, Tektronix, Inc.
R. Bredthauer, LORAL (Ford)
R. Kimble, NASA Goddard Space Flight Center
T.-H. Lee, Eastman Kodak Corporation
M. Lesser, Steward Observatory, University ofArizona
O. Siegmund, University of California, Berkeley
G. Weckler, EG&G Solid-State Products Group
Heterodyne Submm-Wave Sensors Panel
Chair." R. Wilson, AT&T Bell Laboratories,
Crawford Hill
G. Chin, NASA Goddard Space Flight Center
T. Crowe, University of Virginia
M. Feldman, University of Rochester
M. Frerking, Jet Propulsion Laboratory
E. Kolberg, California Institute of Technology
H. LeDuc, Jet Propulsion Laboratory
T. Phillips, California Institute of Technology
F. Ulaby, University of Michigan Center for SpaceTerahertz Technology
W. Wilson, Jet Propulsion Laboratory
J. Zmuidzinas, California Institute of Technology
Sensor Cooler Technology Panel
Cha_: R. Ross, Jet Propulsion Laboratory
S. Castles, NASA Goddard Space Flight Center
N. Gautier, California Institute of Technology
P. Kittel, NASA Ames Research Center
J. Ludwigsen, Nichols Research (SDIO)
77
APPENDIX B. ACRONYMS AND ABBREVIATIONS
The following tables are provided of all the acronyms and abbreviations utilized in the text of this Proceedings.
Space missions and instruments axe listed in Table I, all other acronyms and abbreviations in Table II.