A method for improving interpenetration, mixing, and combustion between a fuel and oxidizer reactant mixture and combustion product gases in engines having a combustor includes the step of providing an engine having a combustor in which the reaction mixture and product gases are subjected to acceleration directed transverse to a direction along which the reactant mixture flows through the combustor during combustion. One or more catalyst elements are positioned within the combustor to generate Rayleigh-Taylor instability and thereby enhance interpenetration of the reactant mixture and product gases within the combustor chamber during combustion.