SBIR-STTR Award

This Phase I proposal is for transparent projectors to be used to add an active mode to a passive hydrophone array. This transparency is necessary to minimize the projectors effect on the hydrophone array performance. We present here a plan for this development which includes FEA modeling as well as some initial testing of modified in-stock projector candidates. We discuss various hydrophone array baffle conditions and how this affects the choice of projector type. The operation of some initial advanced projector design candidates, as well as a unique transparency means, are presented.

Benefit:
Once fully developed, this transparent transducer assembly will provide a means for adding an active projector mode to passive hydrophone arrays, which are currently being adversely affected by noises that have increased. Since the projectors can also be used as hydrophone, it may also be possible to, in some applications, replace the hydrophones in the array with these new transparent projectors. The transparency concepts might also be applied to other projector arrays to improve the performance of transducers with small, compared to wavelength, radiation dimensions.

Keywords:
Projector Technology Incorporated into Submarines, Projector Technology Incorporated into Submarines, Eliminate Specialty Mounting Infrastructure, Mid-frequency SONAR Projector, Acoustic, Projector Technologies Involving Meta-materials, Non-traditional Acoustic Signal Generation, Acoustically Transparent

A means for adding mid band sonar projectors to current passive hydrophone arrays, without reducing hydrophone performance has been developed. During the Phase I of this SBIR Program, small acoustically transparent SONAR projectors that meet these requirements were developed which use a unique yet simple transparency means. To accomplish this goal, Image Acoustics developed a Phase I method which electrically reduces the mechanical Q of the added projectors during their off operating condition while the hydrophones receive the return signal from the target. These conditions and results were demonstrated through FEA modeling and measurement. We propose to optimize the design of the projectors and tuning system and verify their output and apparent transparency during the receive cycle. We would initially verify operation with hydrophone and projector, then with a small array with projectors on both sides of the hydrophone and finally with a larger array of elements to include and evaluate array affects.

Benefit:
U.S. Navy nuclear attack submarines (SSNs) have traditionally relied on acoustic receive arrays to sense their environment, including sensing of enemy submarines. Evolving conditions such as increased shipping traffic have degraded the effectiveness of sensing the underwater regime solely using passive acoustic sensors. Mid-frequency active sonar is used extensively by surface combatants and could meet the environmental sensing needs of submarines; however, current projector technology incorporated into submarine arrays would degrade the passive capability that submarines depend on when covert. Adding an active component to traditionally passive arrays between hydrophones would provide substantial benefits for the navy. It would increase the effectiveness of the current passive arrays by adding dual use for both active and covert operations. Having the active component integrated into existing and new arrays would reduce integration costs by eliminating specialty structural and mounting requirements as well as reducing material, manufacturing, and packaging costs. Image Acoustics novel concept allows this technology to apply to most conformal arrays, offering active operation with little-to-no effects on a systems passive capability. A transparent projector that can be added to existing hydrophone arrays also has various commercial applications. There is a large commercial market for sonar arrays in the oil exploration, seismic survey, rescue and salvage, and bathymetric survey fields. This technology could be added to any arrays used by companies operating in these fields to get the same benefits listed above.

Keywords:
Mid Band Projector, Reradiation, Tuning, Transducers, transparent, Hydrophone Array, Sonar