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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.
Titan IV UA-1207:
The forward booster segment includes an 8-point finocyl grain geometry along with a forward domed closure. The center segments are cylindrical in shape, but all also slightly taper outward in the aft direction. The aft segment is cylindrical (BATES) with a domed shape. As seen in the Thrust vs. Time graph, adding restrictors to the segments can significantly change the thrust curve over time. In the standard configuration, however, it has a regressive curve, where the grain area continuously decreases over time before burnout.
Conclusions:
- Complex/large designs seen in industry require segmented motors
- Many industry grains use 3D shapes (such as truncated cones)
- Industry motors use domed ends filled with fuel (probably due to structural reasons)
- Many industry grains surround a submerged nozzle (likely not too useful for Rocket Team)
- Some motors have segments with different burn rates to further alter thrust curves
- Most industry motors are relatively simple (mainly cylindrical with a little bit of finocyl grain)