R. G. Ross

Aerospace Coolers: A 50-Year Quest for Long-Life Cryogenic Cooling in Space

Cryogenic temperatures are critical to allow infrared, gamma-ray and X-ray detectors to operate with low background noise and high sensitivity. As a result, the world’s aerospace industry has long dreamed of having the means for multiyear cryogenic cooling in space to enable long-life sensors of various forms for scientific, missile defense, and reconnaissance observations. Not long after the first Sputnik was launched into space in October 1957, engineers and scientists were actively seeking means of providing cryogenic cooling for evermore sophisticated and sensitive detectors in a variety of spectral regions. Although both passive cryoradiators and stored cryogens have provided a source of cryogenic cooling for many missions, the consistent dream of scientists and mission planners was always for a mechanical refrigerator that could achieve the temperatures of the coldest cryogens (vastly colder than possible with passive radiators) and have multiyear life without the finite life limitations of stored cryogens. The first cryocoolers in space were short-life Joule–Thomson and Stirling cryocoolers flown on both US and USSR missions around 1970. Since that time, extensive research and development of evermore sophisticated cryocoolers (Stirling, Vuilleumier, Brayton, magnetic, sorption, and pulse tube) has taken place in the world’s aerospace industry. This chapter examines the enormous progress made by the aerospace industry over the past 50 years in developing both cryostats and cryocoolers to enable the widespread use of cryogenic temperatures in space.

Vibration characterization and control of miniature Stirling-cycle cryocoolers for space application

A number of near-term precision space-science instruments have baselined the use of miniature long-life space Stirling-cycle cryocoolers. In support of these instruments, JPL is conducting an extensive cooler characterization test and analysis program focused at developing special sensitive performance measurement techniques and identifying means of improving cooler performance. This paper provides a summary overview of the vibration characteristics of split Stirling cryocoolers of the Oxford type and describes means being developed to achieve vibration levels consistent with the exacting requirements of sensitive infrared spectrometer instruments currently under development for NASA applications. A key emphasis of the paper is on exploring both active and passive means of reducing the residual upper harmonics of the drive frequency that remain with nulled back-to-back compressor and displacer units. Vibration supression results, measured with JPL’s unique 6-degree-of-freedom force dynamometer, are presented for the 80K Stirling cooler manufactured by British Aerospace.

AIRS PFM Pulse Tube Cooler System-Level Performance

JPL’s Atmospheric Infrared Sounder (AIRS) instrument is being built to make precision measurements of air temperature over the surface of the Earth as a function of elevation; the flight instrument is in the final stages of assembly and checkout at this time, and uses a pair of TRW pulse tube cryocoolers operating at 55 K to cool its sensitive IR focal plane.

Synthesis of stiffness and mass matrices from experimental vibration modes.

With highly complex structures, it is sometimes desirable to derive a dynamic model of the system from experimental vibration data. This paper presents algorithms for synthesizing the mass and stiffness matrices from experimentally derived modal data in a way which preserves the physical significance of the individual mass and stiffness elements. The synthesizing procedures allow for the incorporation of other mass and stiffness data, whether empirical or based on the analysts insight. The mass and stiffness matrices are derived for a cantilever beam example and are compared with those obtained using earlier techniques.

Cryocooler Resonance Characterization

Abstract An important issue in the design and scaling-up of Stirling cryocoolers is achieving good drive motor efficiency and launch survivability. The important common thread linking these two topics is the dynamic resonant response of the compressor and displacer moving masses. The fundamental equations governing cryocooler mechanical efficiency and launch vibration response are presented and explored in terms of their implications for cooler design. The resonant frequency, damping and drive motor force parameters associated with the cooler are shown to be key to efficient operation. Means of measuring these parameters are presented and shown to have broad applicability to additional parameters such as drive stiction and vibration transmitted to the instrument. The resonant parameters of the BAe 55 K AIRS proof-of-concept cooler are used as an example to demonstrate the good correlation between the analytical fundamentals and the measured characteristics of a state-of-the-art cryocooler design.

JPL cryocooler development and test program: A 10-year overview

In the 1988 timeframe increasing numbers of proposed space-instrument programs within NASA and the Ballistic Missile Defense Organization (BMDO) were in need of high-reliability, long-life, low-vibration space cryocoolers. To ensure the success of its emerging cryogenic instrument commitments, the Jet Propulsion Laboratory (JPL) implemented a focused multi-year cryocooler program. Over the past 10 years the JPL cryocooler program has included the procurement/development of pulse tube cryocoolers for the AIRS, TES and IMAS JPL/NASA instruments, performed extensive characterization testing of 22 industry-developed cryocoolers, developed and flight-tested a wide variety of cryocooler integration technologies, and developed sorption cryocoolers for use at 10 to 25 K. An overview of the ten years of progress is presented together with a thorough bibliography of published documents describing the work.

PV Reliability Development Lessons From JPL's Flat Plate Solar Array Project

Key reliability and engineering lessons that were learned from the 20-year history of the Jet Propulsion Laboratorys Flat-Plate Solar Array Project and thin-film module reliability research activities are presented and analyzed. Particular emphasis is placed on lessons applicable to evolving new module technologies and the organizations involved with these technologies. The user-specific demand for reliability is a strong function of the application, its location, and its expected duration. Lessons relative to effective means of specifying reliability are described, and commonly used test requirements are assessed from the standpoint of which are the most troublesome to pass, and which correlate best with field experience. Module design lessons are also summarized, including the significance of the most frequently encountered failure mechanisms and the role of encapsulant and cell reliability in determining module reliability. Lessons pertaining to research, design, and test approaches include the historical role and usefulness of qualification tests and field tests.

A study of the use of 6K ACTDP cryocoolers for the MIRI instrument on JWST

The Mid Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST) is a demanding application for the use of space cryocoolers. During calendar year 2003 an extensive study was carried out examining the application to this mission of hybrid 6K/18K J-T cryocoolers developed by NASA as part of their Advanced Cryocooler Technology Development Program (ACTDP). Among the most challenging requirements of the MIRI application were the requirements to cool down the ∼90 kg 6 K cooling load in less than 30 days and to restrict the location of the compressors with their heat dissipation and vibration generation to a remote spacecraft position some 12 meters away from the cryogenic load. Because the hybrid 6K/18K J-T cryocoolers have unique load-carrying capability as a function of temperature, the cooldown requirement was the primary consideration in cooler sizing. This paper presents the lessons learned and performance achieved in the MIRI cryocooler application. In the final proposed configuration, all of the MIRI/JWST design considerations were successfully met. Although the cryocooler option was eventually deselected in favor of a solid-hydrogen stored cryogen system, the cryocooler study offered an important opportunity for understanding and refining the performance and integration capabilities of this important new class of low-temperature space cryocoolers.

EMI Performance of the AIRS Cooler and Electronics

The TRW pulse tube cryocooler for JPL’s Atmospheric Infrared Sounder (AIRS) instrument is required to meet stringent requirements for radiated electric and magnetic fields, conducted emissions on the input power bus, and electromagnetic susceptibility. To meet the radiated magnetic field requirements, special mu-metal shields were designed, fabricated, and fined to the cooler following an extensive period of magnetic testing with mock-up cooler hardware. Excessive magnetic fields is a generic issue with linear-motor cryocoolers, as is excessive levels of input ripple current. Solving the ripple current issue required the addition of a dedicated ripple filter as part of the spacecraft power system.

Performance Characterization of the TRW 3503 and 6020 Pulse Tube Coolers

The Jet Propulsion Laboratory, under joint Ballistic Missile Defense Organization (BMDO)/Air Force Phillips Laboratory and NASA/EOS Atmospheric Infrared Sounder (AIRS) sponsorship, has conducted extensive characterization testing of the TRW Model 3503 and Model 6020 pulse tube cryocoolers. These coolers, built under BMDO/AFPL sponsorship, share a common design that utilizes a single-stage pulse tube integrally mounted onto 10-cc common compression space compressors, and are distinguishable by slight differences in the pulse tube designs which optimized cooler performance for operation at either 35 K or 60 K. The coolers were characterized over a range of heak rejection temperatures and cooler operating parameters (compressor stroke, piston offset, and drive frequency) to understand their effects on cooler thermal performance, cooler-generated vibration and cold block motion, and cooler-generated EMI. Pulse tube parasitic conduction as a function of cold block temperature has been studied for a non-operating cooler; the results show a strong angular dependence relative to gravity. The results of the parametric studies are presented.