Abstract: The invention is concerned with reducing the effect of a progressive surface area versus web thickness relationship in a rocket motor and is particularly useful with center perforate propellant grains where the chamber pressure versus time history is generally progressive. In a very short action time rocket motor, it is desirable to keep the chamber pressure as close as practical to the peak during the entire burn to increase the propellant burn rate. The multiple-stage throat makes this possible in a motor that uses the cost effective center perforate propellant grain design and operates by allowing a first stage throat to erode at a predictable rate while the area of the propellant burning surface is increasing. The motor initial Kn (propellant surface area divided by nozzle area) is raised by using a relatively small initial size for the first stage throat and as a result the rocket motor reaches peak chamber pressure quickly.