Space Station WP-2 application of LDEF MLI results

The Cascaded Variable Conductance Heat Pipe Experiment, which was developed by Michael Grote of McDonnell Douglas Electronic Systems Company, was located in Tray F-9 of the Long Duration Exposure Facility (LDEF), where it received atomic oxygen almost normal to its surface. The majority of the tray was covered by aluminized Kapton polyimide multilayer insulation (MLI), which showed substantial changes from atomic oxygen erosion. Most of the outermost Kapton layer of the MLI and the polyester scrim cloth under it were lost, and there was evidence of contaminant deposition which discolored the edges of the MLI blanket. Micrometeoroid and orbital debris (MM/OD) hits caused small rips in the MLI layers, and in some cases left cloudy areas where the vapor plume caused by a hit condensed on the next layer. The MLI was bent gradually through 90 deg at the edges to enclose the experiment, and the Kapton that survived along the curved portion showed the effects of atomic oxygen erosion at oblique angles. In spite of space environment effects over the period of the LDEF mission, the MLI blanket remained functional. The results of the analysis of LDEF MLI were used in developing the standard MLI blanket for Space Station Work Package-2 (WP-2). This blanket is expected to last 30 years when exposed to the low Earth orbit (LEO) environment constituents of atomic oxygen and MM/OD, which are the most damaging to MLI materials. The WP-2 standard blanket consists of an outer cover made from Beta-cloth glass fiber fabric which is aluminized on the interior surface, and an inner cover of 0.076-mm (0.003-in) double-side-aluminized perforated Kapton. The inner reflector layers are 0.0076-mm (0.0003-in) double-side aluminized, perforated Kapton separated by layers of Dacron polyester fabric. The outer cover was selected to be resistant to the LEO environment and durable enough to survive in orbit for 30 years. This paper describes the analyses of the LDEF MLI results, and how these results contributed to the selection of the WP-2 MLI blanket materials and configuration.