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Multi Layer Insulation (MLI) performance at cold boundary temperatures above 80K to 100K have been well characterized. Further, Lockheed Martin has found that at these temperatures, a blanket’s performance can be well represented by analytic expressions, so long as edge effects, local compressions, and blanket layer density are controlled during the blanket installation. Testing a cold boundary temperatures of 4.2K for the superfluid helium Gravity Probe-B program also found that these same relationships tend to deviate considerably from measurements by a significant margin. Between 4.2K and 80K, no data has been published that quantifies the point where this deviation becomes significant.
This lack of data has the potential for a major impact in the thermal subsystem performance for systems that operate at 30K to 80K cold boundary temperatures. The Next Generation Space Telescope (NGST), Terrestrial Planet Finder (TPF), and Constellation-X are systems that benefit from this data, as they all require passive cooling of critical observatory components to between 30K and 40K. To meet each system’s cooling requirement with low performance risk, large design margins must currently be incorporated in the baseline design.
This paper summarizes testing performed with cold boundary temperatures at liquid nitrogen (77K), solid nitrogen (47K). These measurements fill the gap between 4.2K and 80K and provide MLI design data at low boundary temperatures that are relevant for future NASA initiatives. Commentary is also provided on some limited cold boundary testing with liquid neon (25K) and solid neon (17K).
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