Rigid Polyurethane Foams as External Tank Cryogenic Insulation for Space Launchers

Abstract

In the framework of the present activity, work is carried out on the development of rigid polyurethane (PUR) foam material for external cryogenic insulation of a liquefied hydrogen (LH2) tank for the next generation launcher with a cryogenic upper stage. The main advantage of PUR foams in comparison with other thermal insulation materials is possibility to cover this material on the complicated shape metal surfaces by spraying method, which leads to significant cost savings. The spraying of PUR foams on metal constructions is chemical-technological process. As a result of work performed within the confidential European Space Agency contract, PUR foam material has been developed for the use as external insulation material for fuel tank structures. Raw ingredients from suppliers within EU have been used exclusively. The material has been tested for its performance in normal (room) and relevant (cryogenic conditions) environment and found to be mechanically durable and thermally excellent and therefore appropriate for use in space application. Accelerated ageing test indicate the material to be long-lasting. Safety coefficient, which characterizes the capability of insulation to withstand cryo-shocks, for optimal compositions reaches 4.7.