12-18-2013, 07:08 AM
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Freeform rocketry advocate.
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Join Date: Jan 2008
Location: Claremont, CA "The intellectual capitol of the world."-WSJ
Posts: 3,780
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They do it with a star core at the top and a tapered core for most of the motor. The various tapers and star shapes were engineered to deliver that particular thrust curve. Here's one I did.
http://en.wikipedia.org/wiki/File:Srbthrust2.svg
Having a regressive thrust trace, like an Aerotech C-Slot motor, it not only lowers the aerodynamic drag as compared to the alternative, it also lowers the G forces as the rocket looses propellant mass, perhaps keeping acceleration on a Space Shuttle under 3.5 G's.
Tech Jerry
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