The Hydroshock® water gun

Abstract

An impulsive acoustic source has been developed which uses water under high pressure to create a controlled, impulsive signature generally free of bubble pulses or other aftershot clutter. The gun uses high-pressure water to force a piston back against an air spring to a stop position. A trigger signal releases the piston which drives water through ports in the gun housing to form jets at right angles to the axis of piston travel. The piston abruptly closes the ports as it passes by them, terminating the jets and generating cavitation voids. The voids subsequently collapse in synchronism, away from the body of the gun, creating the gun signature. A prototype model, designated HS-56, exhibits a peak-to-peak signature in excess of 8 bar meters (238 dB re 1 μPa@ 1 M) in a 0–2 kHz band, and can be fired at repetition periods of less than 4 s with a 15-hp pump. This model appears useful for high resolution engineering profiling, subbottom investigations, target impulse response studies, and various signaling applications. The gun concept and the results of calibration, reliability and operational tests will be described. A comparison of HS-56 performance with that of competing seismic sources will also be discussed.