Abstract: An underwater acoustic surveillance system for obtaining data related to nd sources of interest in a large geographic area over long periods. A number of acoustic sensors are dropped from an aircraft for placement on the bottom of the sea at known locations. Each sensor automatically deploys a parachute to retard the descent in the air. A parachute riser weak link releases the parachute upon immersion in the water, and a latch operable at a preselected depth allows cylindrical staves to spread apart and form a stable platform on the bottom from which a hydrophone suspends and an acoustic projector tethers. A web-like flow shield unfolds between adjacent staves of the platform to provide additional retardation during the descent in the water and to reduce hydrophone noise due to water currents at the bottom.

Abstract: A sonobuoy suspension system is disclosed wherein a spring motor having a substantially constant output torque is mounted within an upper sonobouy unit secured to a buoyant flotation member. Formed from a coiled band, constant force extension spring wound in opposite directions about a pair of rotatable drums so that the spring is extended tangentially therebetween, the motor is coupled to a lower sensor unit by a non-compliant suspension cable for supporting the sensor unit at a predetermined underwater depth substantially isolated from the wave affecting the upper unit and flotation member.

Abstract: A sonobuoy is disclosed which has a linear array of hydrophones horizonta depolyable at sea by a metal hydride jet thruster. The thruster is powered by releasing hydrogen gas from iron-titanium hydride (FeTiH.sub.1.95) and igniting it in a mixture with oxygen generated by reacting sodium peroxide (Na.sub.2 O.sub.2) with the water. The hydride is activated by an electrical heater and the steam generated by the combustion of the hydrogen and oxygen mixture. The thrust is directionally controlled in azimuth and depth by a compass and depth sensor.

Abstract: A shape-memory alloy initially configured to have engaging potential for a ance, guillotine or pin connected thereto is wrapped in a heating element powered by current from a water activated battery. When the alloy reaches a specific temperature it silently reverts to a predetermined shape. The reversion force is used to displace a lance to pierce a gas cylinder seal to allow inflation of a float and to cut a retaining loop or withdraw a pin to payout a preset length of hydrophone suspension cable.

Abstract: An air launchable sonobuoy having two separate liquid chemicals which react pon mixing to form an expanded, rigid foam flotation device. Upon deployment in the air, windflaps release a preloaded plate within a submersible housing and urge the chemicals to mix and foam in an elastic envelope. After water impact, an orifice in the housing permits water to fill the voids at a rate sufficient to allow the housing to remain afloat until foaming and erection of an antenna within the envelope is complete. As the envelope expands, a latch releases it from the housing and permits the housing when flooded to sink to the desired depth determined by the payout length of a cable within the housing connected to the flotation device.

Abstract: A novel low cost air-launched sonobuoy having a spherical housing of a liweight semi-rigid foam housing encapsulated the electronic components. The housing includes recesses for receiving a hydrophone and cable pack, and for inserting D-size batteries just prior to launching. A vertical antenna is wrapped around the housing and prevents the pack from deployment until the sonobuoy is charged with the batteries and immersed in water. The free end of the antenna is released and unwraps to permit deployment of the hydrophone and cable pack. The sonobuoy is stored without the batteries in a sealed moisture-proof envelope which can be easily torn open and removed when desired.

Abstract: A sonobuoy having a directional hydrophone centrally enclosed in a flexib acoustically transparent, spherical bag which upon deployment is filled with water to form a hydrosphere. A first embodiment comprises a plurality of upper and lower spreaders which form the bag into a spherical shape having a valve at the bottom most portion thereof for entry of water into the bag during oscillatory motion of the hydrophone. A second embodiment comprises a flexible, acoustically transparent, spherical bag which is time-filled with water by a pump to inflate the bag to a predetermined pressure. The hydrosphere forms a large virtual mass of static water around the hydrophone which reduces near field affects due to flow and motion noise and which also operates as a sea anchor.

Abstract: A system for suspending a gradient hydrophone from a flotation member at the surface of a body of fluid by a single compliant member attached closely above the center of gravity of the hydrophone, in order to minimize the number of principal vibration modes, such as the rocking mode, and group the frequencies of such principal vibration modes in a band far enough below the operational acoustical bands of the hydrophone to allow effective electronic rolloff.