RAM ACCELERATOR OPERATION ANALYSIS IN THERMALLY CHOKED AND TRANSDETONATIVE PROPULSIVE MODES

The thrust characteristics of a ram accelerator are investigated in a quasi-one-dimensional, steady flow analysis that includes finite rate chemistry. From a generalized choking condition, the location of the n ormal shock wave on the projectile and that of a choking location are uniquely determined. When the choking occurs downstream of the project ile, the non-dimensional thrust equals that determined by the existing ram accelerator theory for thermally choked propulsive mode and it is independent of the projectile dimensions (subdetonative velocity regi me). The effective induction length of the chemical reaction decreases with an increasing projectile speed. When the induction length become s shorter, a projectile choking occurs on the projectile body as antic ipated for the transdetonative propulsive mode. In this case, the flow at the projectile exit becomes supersonic, yielding a thrust which is larger than that calculated by the above-mentioned thermally choked p ropulsion theory and depends on the projectile dimensions. Comparing e xperimental data and the results of the present analysis, it is conclu ded that this relatively simple model describes the ram accelerator th rust characteristics reasonably well both in the subdetonative and tra nsdetonative propulsive modes.