A simplified analytical pressure prediction model of an aerodynamically separated interceptor shroud

A FORTRAN computer code has been written to simulate the removal of a shroud which protects seeker hardware on a ballistic missile interceptor. The removal process is characterized by the aerodynamic filling and venting of the cavity defined by a four petal conic shroud. The resulting cavity pressure increase causes the shroud petals to rotate and release from the interceptor, exposing the seeker on the interceptor forebody. The code predicts the shroud petal motion and the pressures on the interceptor forebody at designated locations over the duration of the shroud separation event.

The code has been written to be used as a low cost aerodynamic environment. prediction tool for evaluating initial designs of interceptors which rely on aerodynamic forces to remove cone shaped shrouds consisting of two or more petals. Typically, interceptor forebodies which rely on this design experience mechanical shock related to the aerodynamics of the shroud removal process, which could jeopardize interceptor hardware.

The results of the code for the case of the Army's High Endo- atmospheric Defense Interceptor (HEDI) are compared with HEDI ground and flight test data. It was found that the code's modeling of a constant speed moving shock produced petal motion and forebody pressure data which compared well to the ground and flight test data.