Design and control of solid-fuel ramjet for pseudovacuum trajectories

A ballistic trajectory in air of a powered projectile where the thrust always balances the drag is termed as a pseudovacuum trajectory. For a solid-fuel-ramjet (SFRJ)-powered gun-launched projectile this trajectory can be achieved by the control of engine mass-flow rate, either by a bypass control of inlet air or by a regression rate control of fuel. Based on one-dimensional considerations, the procedures for a preliminary design of the propulsion system for an SFRJ-assisted gun-launched projectile and the methods to calculate the control requirements are presented. Using these, typical configurations of SFRJ suitable for 155-mm gun-launched projectiles are analyzed for different launch angles. The results indicate that the control requirements by either method are minimal and thus, demonstrate the self-throttling characteristics of SFRJ.