Abstract: A small sonobuoy for dropping without a parachute and quickly deploying hydrophones is cylindrical and adapted to float with its axis parallel to the water. The hydrophone cable is wrapped around the housing so that the housing rotates as the cable is payed out. The antenna is also wrapped around the housing and is released after the cable is fully deployed. A retainer covering the coiled cable and the stored hydrophones is held in place by a releasable pin which is released by an electrical device activated by a sea water sensitive switch. The device heats a resistor which melts a lanyard which releases the pin.

Abstract: A sequential launching system is disclosed for sonobuoys and the like in which each of a plurality of sonobuoys is provided with a separate launch mechanism. The launch mechanism comprises a piston and piston chamber at the aft end of the sonobuoy. The cross-sectional area of the piston chamber is substantially smaller than that of the launch tube and air flow passages are provided for allowing ambient air to flow to the aft end of the sonobuoy to equalize the air pressure with that at the forward end. Air passages around the plural sonobuoys are provided by longitudinally extending, radially spaced ribs which extend from the muzzle end to the breech end of the launch tube. The ribs serve to support and guide the sonobuoys in the launch tube.