Introduction

Multilayer insulation (MLI) and single-layer radiation barriers are among the most common thermal-control elements on spacecraft. MLI blankets prevent both excessive heat loss from a component and excessive heating from environmental fluxes, rocket plumes, and other sources. Most spacecraft flown today are covered with MLI blankets, with cutouts provided for areas where radiators reject internally generated waste heat. MLI blankets are also typically used to protect internal propellant tanks, propellant lines, solid rocket motors, and cryogenic dewars. Single-layer radiation barriers are sometimes used in place of MLI where less thermal isolation is required, since they are lighter and cheaper to manufacture. Applications requiring insulation under atmospheric conditions generally use foam, batt, and aerogel materials because MLI is not very effective in the presence of a gas. See Chapter 3 for specific examples of how insulation is used in typical thermal designs.

MLI is composed of multiple layers of low-emittance films, as shown in Fig. 5.1. The simplest MLI construction is a layered blanket assembled from thin (1/4-mil thick) embossed Mylar sheets, each with a vacuum-deposited aluminum finish on one side. As a result of the embossing, the sheets touch at only a few points, and conductive...