A method for improving interpenetration, mixing, and combustion between a fuel and oxidizer reactant mixture and combustion product gases in engines having a combustor, said method comprising the steps 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; characterized by: positioning one or more catalyst elements defined as catalyst material having a longer dimension oriented generally parallel to a streamwise direction along which the reactant mixture and product gases flow through the combustor and on a radially outermost inner surface of the combustor that is perpendicular to the direction of the transverse acceleration to generate Rayleigh-Taylor instability and thereby enhance interpenetration of the reactant mixture and product gases within the combustor chamber during combustion; and wherein the one or more catalyst elements are positioned in the combustor and arranged circumferentially around the combustor with lateral separations between two adjacent of the catalyst elements along a lateral direction that is perpendicular to the transverse direction along which the acceleration acts on the gases flowing through the combustor during combustion. 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; characterized by: positioning one or more catalyst elements defined as catalyst material having a longer dimension oriented generally parallel to a streamwise direction along which the reactant mixture and product gases flow through the combustor and on a radially outermost inner surface of the combustor that is perpendicular to the direction of the transverse acceleration to generate Rayleigh-Taylor instability and thereby enhance interpenetration of the reactant mixture and product gases within the combustor chamber during combustion; and wherein the one or more catalyst elements are positioned in the combustor and arranged circumferentially around the combustor with lateral separations between two adjacent of the catalyst elements along a lateral direction that is perpendicular to the transverse direction along which the acceleration acts on the gases flowing through the combustor during combustion. positioning one or more catalyst elements defined as catalyst material having a longer dimension oriented generally parallel to a streamwise direction along which the reactant mixture and product gases flow through the combustor and on a radially outermost inner surface of the combustor that is perpendicular to the direction of the transverse acceleration to generate Rayleigh-Taylor instability and thereby enhance interpenetration of the reactant mixture and product gases within the combustor chamber during combustion; and wherein the one or more catalyst elements are positioned in the combustor and arranged circumferentially around the combustor with lateral separations between two adjacent of the catalyst elements along a lateral direction that is perpendicular to the transverse direction along which the acceleration acts on the gases flowing through the combustor during combustion.