Measurement of apparent thermal conductivity of multilayer insulations at low compressive loads.

A description is presented of the test calorimeter, the experimental technique, and the results obtained in an evaluation of four multilayer insulations selected for application on future multilaunch space vehicles utilizing liquid hydrogen and oxygen for orbital operations. Particular attention is paid to techniques for minimizing error in obtaining thermal conductivity data. The effective conductivity for four high-performance insulations was determined at a minimum of four compressive loads in the range from 0.0001 to 0.1 psi. Results show that the thermal conductivity of multilayer insulations is insensitive to small changes in mechanical loading at 1 torr interstitial gas pressure, but becomes increasingly more sensitive to mechanical loading as the interstitial gas pressure is reduced.