Overview:

Commercial solid rocket motors use various grain geometries that differ from what we employ on the MIT Rocket Team. This page is meant to describe the grain geometries of different industry rockets and their effects on flight performance in order to learn and adapt to our own designs.

Space Shuttle Boosters:

The forward segment of the motor employs an 11-point star shape along with a domed closure at the front. The middle segments use a straight-walled cylinder shape (BATES). The aft segment is mostly BATES, but tapers outward to surround the booster's submerged nozzle. As seen in the thrust curve, this combination was designed to create a boost to get off the launch pad before decreasing thrust to handle maximum dynamic pressure. The domed closure and submerged nozzle were likely designed for a structural reason rather than pure grain shape, with the grain serving to fill up the otherwise empty space (as opposed to MIT Rocket Team's normal cylindrical tube).