One-dimensional modeling of ram accelerator at high acceleration rates in the subdetonative velocity regime

The predicted acceleration performance of the ram accelerator at elevated pressures, based on the quasi-steady model, is much greater than that observed in experiments. This discrepancy is attributed to the increase of mass of the propellant accumulating in the control volume, such that it approaches the mass of the projectile itself. A revision of the conservation equations to account for unsteady flow effects was conducted. The corresponding predicted thrust as a function of Mach number is significantly less than that derived from the quasi-steady model. By using a virial-type equation of state for the combustion products, a better agreement with experimental data was obtained using this unsteady modeling approach.