The guarded flat plate insulation test cryostat (Cryostat-500) is a boil-off calorimeter comprising a flat-bottom test apparatus for measuring the absolute thermal performance of an insulation test article. Typical dimensions allow accepting test specimens 200 mm in diameter by up to 30 mm thick. The test chamber is guarded by a second cryogen chamber to prevent parasitic heat loads. System insulation materials provide additional thermal stability for testing over a wide range of environmental conditions. The cold-mass assembly can be configured for rigid or soft materials, with or without compressive loads.

The Cryostat-500 provides a wide range of heat flux performance over the full range of environmental conditions including vacuum levels from 10–7 to 760 torr. The instrument has been proven through extensive testing of multilayer insulation (MLI) systems, aerogel blankets, fiberglass, foams, etc. Both the quality and quantity of the thermal performance data have increased, even as the process and method have become more time-efficient and cost-effective. The apparatus provides information on the steady-state thermal transmission properties of thermal insulation systems and materials under cryogenic-vacuum conditions. These thermal properties include heat flux (q) and effective thermal conductivity (ke). Thermal insulation systems may be composed of one or more specimens that may be homogeneous or non-homogeneous at boundary conditions from 4 to 400 K, and in environments from high vacuum to ambient pressure of residual gas.

The combination of cold mass design, vacuum chamber design, and ancillary equipment, along with boiloff methods, makes the high testing rate and high data quality a nearly hands-off operation. Installation is simplified and operation is accomplished by periodic tending of the instrument over several hours or several days, depending on the type of test specimen. The core of the technology is the cold mass design that ensures the energy being measured by the test chamber is passing only through the desired heat transfer area of the test specimen. The cold mass also includes an edge guard ring that is fully adjustable. The edge guard provides for additional thermal fine-tuning capability, and expands the capability of the Cryostat-500 instrument by allowing testing of thicker specimens.

The Cryostat-500 technology includes handling tools, instrumentation, methodology, data acquisition (hardware/software), and other ancillary equipment needed to provide consistent test results in a cost-effective, safe, reliable, and practical manner.

This work was done by James Fesmire, Thomas Bonner, Philip Stroda, and Wesley Johnson of Kennedy Space Center. For more information, contact the Kennedy Space Center Technology Transfer Office at 321-861-7158. KSC-13633

NASA Tech Briefs Magazine

This article first appeared in the January, 2015 issue of NASA Tech Briefs Magazine.

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