The Design of Sub-Caliber Aero-Thermal-Chemical (ATC) Gun Projectiles for Aerodynamic Stability

The following proposal details an effort required for understanding the in-bore aerodynamic stability of sub-caliber projectiles in aero-thermal- chemical (ATC) guns in order to design stable projectiles. The ATC gun is based on the concept of a projectile traveling through the propellant and deriving acceleration from the expansion of gases on the aft end of projectile. Since the projectile must travel through the propellant, the projectile is generally sub-caliber so that the propellant can flow around it. One of the most important unanswered questions in Ram and Scramaccelerator technology relates to the in-bore aerodynamic stability of the projectiles. If the stability of these sub-caliber projectiles was understood several important design problems for ramaccelerator systems could be greatly simplified. In the proposed Phase I effort, the in-bore aerodynamic stability of Ramaccelerator projectiles will be examined. A three-dimensional computational fluid dynamics (CFD) code will be used to assess the static stability of the projectile, the effect of several shape parameters on stability will be explored and a linearized analysis for the dynamic stability will be performed. The results of the Phase I effort will demonstrate the usefulness of CFD as a stability analysis tool and lay the groundwork for the study of the dynamic stability in Phase II.