Naval front-line combatant vessels by their very nature are expected to be able to survive the loadings of various above and below water weapon attacks and continue fighting. Near misses by underwater weapons such as mines and torpedos may not damage a vessel from the structural viewpoint, however equipment and systems may be seriously damaged, often to the extent of incapacitation of power, navigation, propulsion and combat systems. Incapacitation is due to the resulting shock wave generated by an underwater explosion transmitted through the vessel structure, resulting in mechanical loadings and possible damage to equipment and systems. Vital equipment and systems are therefore usually shock tested prior to installation aboard a vessel and a shock trial on the First-of-Class vessel performed to ensure that, as a whole, systems continue to operate as installed on the vessel. A conventional shock trial requires an explosive charge to be detonated adjacent to the ship to simulate a weapon attack. First-of-Class ship shock trials can however be very expensive, time consuming and increasingly require extensive environmental considerations. This paper outlines an alternative technique that could be used in a trial to shock test vital equipment and systems aboard the First-of-Class RAN Hobart Class Air Warfare Destroyer. The technique involves the underwater use of air-guns to produce a mechanical shock load upon a vessel and a similar loading on equipment and systems that would be produced by an underwater explosive. Potentially, air-guns may offer numerous advantages over explosives, including cost of testing, time, safety and a considerably lower environmental hazard during a shock trial. DSTO is investigating the use of air-guns in collaboration with the US Navy and private industry to further develop this technology.
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