Abstract : A theoretical study of the gas dynamic interaction between a hypersonic plume and the opposed hypersonic external stream is presented. Steady, axisymmetric, inviscid, perfect gas flow is postulated for both the bow and far field regions. Limiting forms of solutions are obtained for the bow region by application of the Newton-Busemann approximation to both the exhaust plume and ambient air flow. Through asymptotic expansions and their matching, it is found that six regions are required to adequately describe the bow region. For the far field region, the hypersonic small-disturbance form of the Newton- Busemann approximation is applied. From asymptotic expansions and their matching, it is found that entropy wake solutions are required to adequately describe the exhaust flow and the air flow near the contact surface. Analytical solutions are obtained which (1) define scaling parameters for the bow and far field flow; (2) estimate the accuracy of the Newtonian impact theory in predicting bow region geometry and properties; (3) establish the variation of bow and far field properties with variation in the primary system design parameters.