Publications

Thermal analysts address a wide variety of applications requiring the simulation of radiation heat transfer phenomena. There are gaps in the currently available modeling capabilities. Addressing these gaps would allow for the consideration of additional physics and increase confidence in simulation predictions. This document outlines a five year plan to address the current and future needs of the analyst community with regards to modeling radiation heat transfer processes. This plan represents a significant multi-year effort that must be supported on an ongoing basis.

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The High-Altitude Balloon Experiment (HABE) telescope was designed to operate at an ambient temperature of {minus}55 C and an altitude of 26 km, using a precooled primary mirror. Although at this altitude the air density is only 1.4 percent of the value at sea level, the temperature gradients within the telescope are high enough to deform the optical wavefront. This problem is considerably lessened by precooling the primary mirror to {minus}35 C. This paper describes the application of several codes to determine the range of wavefront deformation during a mission.

Thermal testing of space payloads at Sandia National Laboratories is conducted in a large cylindrical (7.0 feet in diameter) vacuum chamber with temperature controlled walls. The payload is generally attached to a baseplate with independent temperature controls. To establish well-defined boundary conditions during the tests, uniform wall temperatures are desired in the test chamber. Thermal-vacuum tests were conducted on this space simulation chamber to determine if temperature gradients existed on the chamber shroud and end-bells. Recorded temperature measurements indicated large temperature gradients on the chamber shroud and end-bells. Furthermore, it was difficult to manually control the flow of liquid to the end-bells in order to achieve equal end-bell temperatures. However, results from these tests were used in a computer program developed to predict locations on the shroud and end-balls where a thermocouple would measure the best area-weighted average temperature. These measurements provide necessary boundary temperatures that can be used in a thermal model of a satellite payload. Results were obtained for different shroud and baseplate temperature settings. 8 figs., 5 tabs.