Polyurethane and polyisocyanurate foams in external tank cryogenic insulation

Abstract

External tanks of the spacecrafts need not only efficient, but also safe cryogenic insulation materials and the issues of their development are still urgent. At present, polyurethane (PUR) or polyisocyanurate (PIR) foams' cryogenic insulation is widely applied in the partially reusable launch systems. Factors influencing the cryogenic resistance of external thermal insulation performed of spray-on PUR or PIR foams are characterised based on a wide literature search. They include chemical structure and macromolecules' architecture of polymeric matrix, physical and mechanical properties of foams, thermal stability and combustibility, cellular structure of foams etc. Experimental data on physical and mechanical properties at room and cryogenic temperatures are presented for IWC developed PUR foams further named as IWC-Cryo. Technological processes of spray-on PUR and PIR foams cryogenic insulation, cryo-pumping and the main defects of external tank insulation are analysed as well as applications of foams' insulation in space technologies (Space Shuttle, Ariane and Buran).