 A BATES grain consists of two or more cylindrical grain segments with the outer surface inhibited, but free to burn both on the segment ends and the cylindrical core. Such grains can be configured to achieve a desired thrust-time profile while maintaining an acceptable center of gravity

This configuration has the disadvantage that the burning area increases as the grain regresses, resulting in an increase of chamber pressure with time, a situation that is undesirable for three reasons. First, the case must be designed structurally for the maximum pressure and it is used inefficiently for much of the burn time. Second, at least for launch systems, we want a high chamber pressure at the beginning of the burn to provide a high nozzle pressure ratio in the presence of the high atmospheric pressure. And finally, if the thrust increases with time it exacerbates the increase in acceleration due to the decreasing mass of the vehicle that results from the propellant consumption, and results in very high g loads at the end of burning.