Numerical analysis of the free-fall behavior of a space launcher fragment

A numerical investigation of the behavior of stages or parts of launchers as a function of fundamental parameters, such as Mach number and incidence angle during the free-fall phase, is presented. The analysis is performed considering a cylindrical body as a representative model of a generic launcher fragment. Initially, a static analysis is conducted to determine the average equilibrium angle achieved for various positions of the center of gravity (c.g.). In the supersonic regime, because the center of pressure (c.p.) is at the center of the cylinder, the equilibrium position is 180 or 0 deg, excluding the condition in which the c.g. is in a tiny region around the cylinder center. In the subsonic and transonic regimes, the c.p. moves forward, approaching one-fourth of the chord, and the equilibrium position is related to the c.g. location. Then, a dynamic analysis is conducted to determine the dynamic stability of the cylinder at different equilibrium positions and oscillation amplitudes. It is found that the fragment is stable in all the aerodynamic regimes when the c.g. is far from the center of the body. In cases characterized by a c.g. location close to the center, a stable condition is observed only in the supersonic regime.