Water Tunnel Tests of the 3.5" Rotating Rocket

Abstract

This report covers tests of a 2" diameter model of the 3.5" Rotating Rocket. Five different designs of nose were tested and the drag, cross force, and moment coefficient curves determined. This projectile is unstable under static conditions, without rotation, except for yaw angles between - 1-1/2° and + 1-1/2° yaw in which region a slight stabilizing moment was observed. The drag coefficient varies from 0.28 at 0° yaw to 0.39 at 16° yaw and the cross force coefficient varies from zero a 0° yaw to 0.71 at 16° yaw. The moment coefficient curve, except for the region between - 1-1/2° and + 1-1/2° yaw, shows a destabilizing moment which reaches a maximum of + 0.081 at approximately 14° yaw. A series of tests was made to determine the effect of asymmetry of the nose. The model was assembled so the axis of the nose made an angle of about 1-1/2° with the axis of the body. This is equivalent to the center of the tip of the prototype nose being offset 1/8" from the center line of the body. This rather large asymmetry produced so little change in the drag, cross force, and moment that it would appear to be negligible from the practical standpoint.

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