Subsonic Static and Dynamic Aerodynamics of Blunt Entry Vehicles

The incompressible subsonic aerodynamics of four entry-vehicle shapes with variable c.g. locations are examined in the Langley 20-Foot Vertical Spin Tunnel. The shapes examined are spherically-blunted cones with half-cone angles of 30, 45, and 60 deg. The nose bluntness varies between 0.25 and 0.5 times the base diameter. The Reynolds number based on model diameter for these tests is near 500,000. Quantitative data on attitude and location are collected using a video-based data acquisition system and reduced with a six deg-of-freedom inverse method. All of the shapes examined su ered from strong dynamic instabilities which could produced limit cycles with su cient amplitudes to overcome static stability of the con guration. Increasing cone half-angle or nose bluntness increases drag but decreases static and dynamic stability. Nomenclature A1;A2;A3 = coe cients in velocity t (Eq. 5) CD = drag force coe cient CD;0;CD 2 = drag force coe cient terms (Eq. 1) CL = Lift force coe cien