AbstractThe kinetic deuterium isotope effect was used to investigate the rate‐limiting process in the combustion of formulated nitramine propellants. Model propellant formulations containing either octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), or their deuteriated analogues were pressed into pellets and burned under nitrogen pressure in a window bomb. The magnitudes of the observed deuterium isotope effects indicate that the HMX and RDX exert significant control over the combustion phenomenon of the propellants studied. Furthermore, assuming a consistent mechanism between decomposition and combustion, the observed isotope effects suggest that a carbon‐hydrogen bond rupture in HMX or RDX is the rate‐controlling step in the combustion of the model nitramine propellants. Observed isotope effect values for HMX‐CW5 and RDX‐CW5 formulated propellants at 1000 psig (6.99 MPa) pressure were 1.29 ± 0.09 and 1.24 ± 0.07, respectively, compared to a theoretical estimate of 1.29 for a primary effect due t