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The forward segment of the booster has a 15-point star grain geometry along with a domed forward closure. The forward segment also includes faster burning fuel than the rest of the motor to alter the thrust curve. The center segments are straight-walled (BATES) grain. In the aft segment, the BATES tapers outward to enclose a submerged nozzle. The thrust of the motor is as follows: it increases with the expanding area of the BATES and star shapes, it decreases substantially when the forward segment burns out, and finally it increases with the BATES until it also burns out.
Vega P80 Motor:
The forward section of the motor has a BATES shape and a forward domed closure. The middle section also has a cylindrical BATES grain geometry. At the aft end, the BATES opens up into a 12-point star shape before surrounding a submerged nozzle. These geometries have the thrust first increase with the expanding BATES/star shapes, decrease as the star loses area and becomes more circular, and finally increase with the expanding areas before burning out.