Numerical Investigation of Ram Accelerator Operation with Axisymmetric Projectiles

Abstract

The ram accelerator is a hypervelocity chemical propulsion device capable of accelerating massive projectiles throughout the velocity range of 0.5 km/s to 6.0 km/s. Its propulsion cycle is similar to that of an in-tube ramjet operating with subsonic, supersonic, and/or mixed mode combustion processes that are dependent on in-tube Mach number and projectile geometry. The projectile carries no onboard propellant and has no moving parts. Ram accelerator was originally successfully developed with finned-projectiles in smooth-bored tube. More recently, however, new configurations are being developed to operate with axisymmetric projectiles in baffled and railed tubes to implement more practical setup for various applications. First, a review of theoretical and experimental developments of ram accelerators with emphasis on development of baffled and railed tubes is presented. Second, reviews of recent numerical/computational fluid dynamic models of railed and baffled tubes configurations are summarized. Then, some recommendations are provided for future works to improve CFD modeling of railed and baffled tubes with an expectation to layout a process how to optimize geometrical features of ram accelerators and projectiles. Lastly, a high-level summary of findings on railed and baffled tube CFD research works are provided. Achieving these research goals will improve our understanding of ram accelerators and provide guidance on how to optimize geometrical features of ram accelerators.