Solid-Fuel Ramjet Assisted Gun-Launched Projectiles

The principles of construction and operation of a solid-fuel ramjet assisted gun- launched projectile are briefly explained. A concise global-survey of the projects on solid-fuel ramjet powered missiles is presented. Pseudovacuum trajectory is a ballistic trajectory in air of a powered projectile where the thrust always balances the drag. Easy and accurate predictability and insensitiveness to external disturbances are the two major advantages of the pseudovacuum trajectory. This trajectory can be easily achieved for gun-launched projectiles by the use of solid fuel ramjets. A preliminary-sizing procedure for solid fuel ramjet powered gun launched projectile is presented. Supersonic spillage and its momentum, bypass-air momentum, real time variations of stagnation pressure losses at the two rearward steps (one at the inlet to and the other at the exit of the combustion chamber), heat addition losses, and combustion efficiency are included in the procedure. Also, presented are the ramjet-control requirements for a typical 155-mm gun launched projectile. The control requirements are minimal, demonstrating the "self throttling characteristics" of solid fuel ramjets. For the typical 155-mm gun launched projectiles, following pseudovacuum trajectories using solid fuel ramjets, the maximum range is found to be in excess of 40 km.