Effects of launch tube shock dynamcis on initiation of ram accelerator operation

摘要

Normal operation of the University of Washington's ram accelerator involves the use of a perforated tube to vent gases from the light gas gun into an evacuated tank before the projectile enters the ram accelerator tubes. Because there is residual air in the launch tube and gases from the gun that blow by the obturator, a shock is generated and reflects between the movign projectile/obturator and the entrance diaphragm. The vent tube perforations relieve the resulting pressure rise, such that it does not become significant until after the projectile has passed the vent section. Experiments were performed to determine the feasibility of eliminating the venting process. It was found, as expected, that the pressure increase from the shock reflections was much higher for ventless operation than for vented operation and in some cases prvented initiation of the ram acceleration process. The effect of increasing residual launch tube pressure on the starting process of the ram accelerator wasalso ivnestigated. It was found that for initial gun launch tube pressures of 21 kPa or less, successful starting of the ram accelerator was possible at a fill pressure of 5.0 MPa.