Title: Effects of launch tube gases on starting of the ram accelerator
Abstract: I. Introduction The ram accelerator is a ramjet-in-tube concept for propelling projectiles to very high velocities. Using a conventional gun, a subcaliber projectile is injected supersonically into a tube filled with premixed gaseous fuel and oxidizer, through which it is driven by a wave of combustion. Normal operation involves the use of a perforated tube to vent gases from the conventional 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 full caliber piston, or obturator, placed at the base of the projectile, a shock is generated and reflects between the moving projectile/obturator and the diaphragm that separates the launch tube from the ram accelerator tube. The vent tube perforations relieve the resulting the pressure rise, such that it does not become significant until after the projectile has passed the vent section. 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 prevented initiation of the ram acceleration process. The effect of increasing residual launch tube pressure on the starting process of the ram accelerator was also investigated. It was found that for initial gun launch tube pressures of 3.1 psi or less, a successful start occurred at a fill pressure of 50 atm. Instruments just beyond the entrance diaphragm showed that the initiation of combustion generated enough thrust to allow the projectile to overtake a transmitted shock, whereas, in a non-reacting experiment, the projectile experienced a start failure. Presumably, the initiation process at launch tube pressures higher than 3.1 psi did not generate sufficient thrust to allow the projectile to outrun the shock.
Publication Year: 1997
Publication Date: 1997-07-06
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 13
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