Aerodynamic Loads on a Ball-Obturated Tubular Projectile
Abstract
A tubular projectile is one with a hole bored along its longitudinal axis. The hole presents a problem in getting the round expelled from a gun. Some means of sealing the hole until the round clears the muzzle is required. A ball- obturator offers one practical means of accomplishing this without any accompanying FOD hazard. The ball-obturator, analogous to a common ball-valve, remains closed under the force of the expanding propellant charge and opens as soon as it is released. The high projectile spin rate created in the barrel causes the ball to align its ports with the projectile tube through a complex gyrodynamic motion that is highly dependent upon the external moments relative to the spinning projectile. This study presents results of wind-tunnel tests designed to quantify lift, drag, and moment forces imparted to the projectile by the ball as it transitions to a full open position. Wind-tunnel balance designs are discussed and equations for deduction of forces are presented. Drag and moment coefficients are plotted as functions of ball angle and presented along with Schlieren photographs of the flow at each test point. Techniques for separating tunnel interference from projectile forces are presented along with an uncertainty analysis.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1982
- Accession Number
- ADA115756
Entities
People
- William Arthur Bry
Organizations
- Naval Postgraduate School