Development of an Analytical Transient Evacuation Model for the Fairing Jettison Process

A general, lumped-parameter, control volume equation is developed to describe the rapid loss of pressure associated with a launch vehicle fairing jettison event in its initial phase. Beginning with a general mass conservation statement, a sonic constraint is applied to the expanding gap between receding fairing halves to produce a statement for transient density. This is related to fairing pressure by assuming the expansion may be described by a polytropic process. A generic, single-step, lateral fairing half separation case is created and explored for illustrative purposes.