GODDARD SPACE FLIGHT CENTER

Cryocoolers

PROGRESS REPORT

July - September, 1994

Two-Stage Stirling Cooler

Program Goals and Objectives

This program will result in an advanced engineering model of a two-stage linear Stirling cycle cooler for use by instruments on the Earth Observing System (EOS). However, the cooler will be of use to many other NASA programs in earth science, astronomy, microgravity sciences, interplanetary sciences and the Human Exploration Initiative.

The cooler must have long life, high reliability and low vibration, as well as being small, light weight, and efficient. The key cooler specifications are as follows:

• Long life: 5 years minimum; 10 year goal
• High reliability: 0.95 for 5 years
• 1000 start/stop cycles over mission life
• Low vibration: <0.05 lb force maximum; 0.02 lbf goal
• High efficiency: < 75 watts input power
• 0.3 watts of cooling power at 30 K
• Low weight: less than 15 kg
• Minimal size
• Simple interfaces
• Integration flexibility
• Designed to withstand Titan 4 or Shuttle loads
• Maximum cold finger displacement during operation of 0.001 inches
• 0.1 K temperature stability over a 24 hour period 28 volt dc input power
• Electromagnetic compatibility with EOS (GISS)
• Minimum magnetic signature
• Soft mounting cannot be used to meet vibration
• Cryocooler must operate in any orientation in a zero and 1-G environment.

GSFC - Cryocoolers

Fourth Quarter FY 94 - Report

Executive Summary

Highlights of the Past Quarter:

The engineering model two-stage Stirling cooler continued to progress at Ball Aerospace during the fourth quarter of FY94. Unfortunately, a reduction in the funding available in FY95 will delay completion of the cooler development program until FY96.

The most important highlight this quarter was the successfully completion of two tests of the fixed regenerator. I have reported previously that the fixed regenerator eliminates the delicate cold finger that is a very serious integration problem with all existing long life Stirling coolers. The first test indicated that the fixed regenerator will have the same excellent thermodynamic performance as the previous moving regenerator. The second test demonstrated that additional cooling power can be obtained at higher input power. This flexibility further increases the applicability of the cooler.

The engineering model compressor parts were completed and the assembly of the compressor was begun. The design of the electronics was completed and, except for final details of the cold finger, the design of the expander was completed. Parts for the electronics were ordered and the detailed planning for the fabrication of the electronics was begun.

The Air Force has decided to procure a two-stage Stirling cooler from Ball. The Air Force cooler will be a duplicate of the NASA cooler except that the regenerator will be optimized for optimum thermodynamic performance at a higher temperature. The Air Force is considering optimizing the performance at some temperature between 35 K and 65 K.

Tests performed at Goddard on the Technology Demonstration model and calculations performed by Ball both indicate that the Ball cooler can be used to cover a wide range of applications.

Level 1 Two-Stage Cooler Milestone Status Report

Goal:

• Develop a long life, highly reliable two-stage Stirling cooler for use by Mission to Planet Earth and other users.

Approach:

• Contract with industry supported by Goddard-developed vibration control system and Goddard functional and environmental testing of the cooler.

Background:

• Two-stage Stirling coolers obtain lower temperatures than single-stage coolers and provide higher thermodynamic performance.

Status of Ball engineering model two-stage cooler:

• The design of the compressor and electronics for the engineering model cooler is compete and the design of the expander is nearing completion. The expander will incorporate a fixed regenerator to eliminate the delicate cold finger that is a major concern with the present generation of Stirling coolers. The electronics for the engineering model have benefited from the parallel development of cooler electronics under the X-Ray Spectrometer (XRS) flight program at Ball. As a result, the engineering model cooler will include surface mount electronics which will result in a compact, light weight set of electronics to operate the cooler.

• Ball is currently fabricating the engineering model cooler.

Return to:

• Sensors and Instrument Technology Page
• NASA OSAT Spacecraft Systems Division Page
• NASA Office of Space Access and Technology (OSAT) (no page available yet).
• NASA Headquarters Page
• NASA Page