Foam-in-place pyrotechnic system

A gas generator is provided, the gas generator having a propellant cushion that prevents movement of propellant wafers, tablets, or grains by providing a bias thereagainst. Furthermore, the cushion may be formed from a polyurethane-based foam material and if desired, a known oxidizer combined within the foam. Channels inherent within the polyurethane-based foam enhance the combustion of the main gas generant. Alternatively, the substituted polyurethane polymer combined with an oxidizer may be formed as a monolithic grain that provides autoignition and gas generant function in lieu of a primary gas generant or in lieu of an igniter composition, for example.