SBIR-STTR Award

Improvements in the noise quieting of submarines have reduced the effectiveness of passive sonobuoys in Anti-Submarine Warfare (ASW), causing greater emphasis on active acoustics. However, a sonobuoy with array gain of 24 dB would be a useful asset in the Navys airborne ASW capability. Using velocity sensors can reduce the number of array sensor nodes over omnidirectional hydrophones and reduce the array aperture, needed to provide this much gain in an A-size sonobuoy. Maximum gain is achieved in the real world noise environment, where discrimination against vertical wind-wave noise will improve array performance. The acoustic frequency and array gain will define the array geometry. The large array provides a challenge to package the array in A-size, to deploy it, and maintain the array geometry over the life of the buoy. The Phase I effort will determine the feasibility of developing an innovative free floating high gain array of small inexpensive velocity sensors that can provide over 24dB gain, demonstrate innovative packaging and deployment concepts for the array in an A-size sonobuoy design, evaluate the performance of candidate arrays in realistic noise fields, through modeling, and to select the array design for fabrication and testing in Phase II.

Benefit:
The High Gain Array of Velocity Sensors development, as proposed and described in this proposal, gives this system a potential for application to a variety of other government agency and commercial markets. Passive detection of acoustic signals from the array has potential applications in marine mammal detection, drug interdiction and terrorist security systems. The Coast Guard will find it useful in coastline and harbor defense.

Keywords:
vector sensor, vector sensor, Horizontal Line Array, passive acoustic sensor, Passive Sonar, Sonobuoy, ASW, underwater acoustics

An air-launched passive long-life A-size sonobuoy with a vertical omnidirectional sensor array designed for the low frequency band from 5 to 100 Hz will be developed. The proposed design comprises a vertical line array of 21 omnidirectional sensors and centrally-located directional sensor with an aperture of 1000 feet suspended by a small-diameter telemetry cable from a surface float. The primary emphasis of this effort is the development of the acoustic array and its associated data handling and telemetry electronics to provide a capable acoustic ASW sensor system that will deliver useful target detection information to the war fighter. The sensor array will be integrated into a full sonobuoy system, which will include the suspension and telemetry cable, the surface float, and batteries. The system will be developed throughout with full consideration of the A-size packaging constraints. Prototype over-the-side units will be fabricated and tested to demonstrate the system performance.

Benefit:
The results of this effort will provide a prototype to be demonstrated at sea to validate and refine the operating characteristics of the array. The technologies developed under this SBIR may be transitioned into advanced development and ultimately production sonobuoys for submarine detection. In addition to Naval applications, the product of this effort could also benefit environmental measurements for oceanographic studies and forecasting, commercial studies of seismic activity, and commercial approaches to underwater mining and mineral exploration.

Keywords:
Sonar Array, Vertical Line Array, passive acoustic detection, ASW, Sonobuoy, low frequency sonar