The effects of a spherical segment afterbody on the damping in pitch of a blunted 12-l/2℃one were studied. Variations were made in the base radius, and the surface of the shortest radius base was modified by annular steps, both in and out, and by annular fences. The Mach number range for the test was 0.25 to 2.20, and the angle-of-attack range from -4° to +l8°.nThe results of the tests showed that decreasing the radius of the spherical base caused an unstable shift in the damping moment. This change was large enough to cause unstable damping in the subsonic speed range. The surface modi¬fications to the base did have some corrective effect on the damping, but not sufficient to stabilize the model at subsonic speeds.
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