Firing recoilless weapons from enclosures.

THE PROBLEM: Recoilless weapons commonly release a great deal of energy rearward in the immediate vicinity of the crew. If such weapons are fired from within structures, there is concern that in addition to the acoustic hazard to the ear or other organs, there might be hazard associated with flying debris or even structural collapse.

STUDIES: Two studies were conducted to evaluate such hazards by remotely firing a total of 24 rounds from the 90 mm recoilless rifle, LAW, TOW, and DRAGON weapons systems from within enclosures (Price, 1978; Shank & Garinther, 1975). The structures, selected from available buildings, were made of various materials (reinforced concrete, masonry, sandbags, and wood) and ranged in volume from 14m3 to 161 m3 with venting areas from 2.9 m2 to 11 m2. Data included pressure histories, motion pictures of the structures and small objects placed in the room, and physiological data from 32 goats (tissue/organ system damage) and 8 cats (hearing loss measures).

RESULTS AND CONCLUSIONS: At the firer's locations, peak pressures ranged from 178 to 189 dB and B-durations ranged from 28 to 376 msec. Although the firings commonly produced some structural damage, none of the firings caused structural collapse or induced tissue damage to nonauditory organs. Ear drum rupture did occur in 5 goats and the cat ears exposed with no hearing protection did show permanent hearing losses. Of the cat ears exposed with hearing protection (EAR plugs), only one showed a permanent loss.