Volume I: Fundamental Technologies, David G. Gilmore

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Multilayer Insulation (MLI) is used to minimize temperature gradients throughout the spacecraft and to control heat transfer rates. 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. Single-layer radiation barriers are sometimes used in place of MLI where less thermal insulation is required, since they are lighter and cheap to manufacture. <br \>

In practice, simply increasing the number of layers past a certain value will not improve performance. As the no. of layers increases, radiative heat transfer becomes small compared with conductive “shorts” between layers and other losses. Taking all these factors into account, about 25 layers usually suffice to obtain a minimum overall conductance value.