Abstract:
Atmospheric entry is a critical phase for mission that seeks to return astronauts or
scientific payloads back to Earth or explore the surface of a planet with an appreciable
atmosphere. This project aims at the comprehensive investigation of the dynamic stability of
blunt body atmospheric entry vehicles. As blunt vehicle enters a planetary atmosphere, the
aerodynamic moments acting upon it can result in unstable pitching motions and divergence of
oscillation amplitude. Typically, these instabilities are found in the low or mid supersonic regime
of the trajectory just prior to parachute deployment. The amplitude envelope of a planetary probe
as it enters an atmosphere can play an important role in terminal events like the deployment of
parachutes and entry/reentry trajectories. Most analysis considers the case of constant or linear
aerodynamic coefficients. In many cases the aerodynamic coefficients exhibit nonlinear
behavior. In this research, the nonlinearities of various stability coefficients are correlated with
the system response by generating approximate closed form analytical solutions. For this
purpose, the Multiple Time Scales method in conjunction with bifurcation theory is used to
obtain the approximate solutions of the multiple degree-of-freedom nonlinear equations of
motion. The explicit analytical results obtained are useful to identify the key parameters affecting
the dynamics and stability of the blunt body atmospheric entry vehicle. The conditions leading to
limit cycle responses in the vicinity of loss of damping regime are discussed. The analytical
solution is duly validated with the numerical solution in the end. Such research endeavors will
help the Government of Pakistan to realize the goals of “Space Programme 2040” and bring the
benefits of the complete spectrum of space technology to the people of Pakistan.
