Aerodynamic penetration and radius as unifying concepts in flight mechanics.

Abstract

The scale of atmospheric entry processes and of certain other problems in vehicle dynamics may be quantified in terms of a vehicle parameter that has the dimension of length. Two such lengths, the 2m/pACD and the 2m/pACL-> have simple physical interpretations and tend to be constant multiples of the characteristic dimensions of geometrically similar vehicles of constant density. The aerodynamic penetration may be used as a linear scale factor to generalize trajectory studies if aerodynamic drag is important, and the aerodynamic radius may be used if aerodynamic lift is important. Several problems involving the deceleration and flight mechanics of entry vehicles, airplanes, and ballistic projectiles are discussed to show the application of these parameters to wellknown situations.