N102-155 TITLE: Towed Array Fishing Net Entanglement Prevention or Damage Reduction

TECHNOLOGY AREAS: Sensors

ACQUISITION PROGRAM: SURVEILLANCE TOWED ARRAY SENSOR SYSTEM (Low Frequency Active) ACAT II

OBJECTIVE: Research and develop a method and/or apparatus to prevent or mitigate towed array system damage from fishing net and hook entanglement

DESCRIPTION: Fishing nets plague US Navy operating areas in the Pacific Fleet (PACFLT). They entangle Navy towed arrays, especially the twin-lined (TL -29A) array used by SURTASS. Entanglements occur with little or no warning. The entangled array coupled with the constant tow of the vessel causes enormous stress on the towed array and cable. The stress either snaps the array and/or significantly damages individual modules.
The costs of net entanglements are monetarily significant, impact mission critical operations, and reduce PACFLT ASW readiness. Disentanglement operations temporarily halt operations with similar consequences.

The Navy is committed to lessening the likelihood of net entanglements. This topic solicits innovative solutions beyond the current state of the art that improve array survivability.

Current solutions consist of the following. (a) SURTASS Headline and Roll Control System (SHARC), a rigid system between the two arrays that allows the system to potentially "fly" over the nets rather than collapse in them (as paravanes did). However, the SHARC system can act as a net collector. The system has been useful in preventing collapse of the arrays (and further more expensive damage) but still collects nets and often can "push" fishing nets further down the array. ( b) Preventative tools that measure spikes in tension. The tensiometer that is currently in use measures tension in the array, which is triggered by an entanglement that has already occurred. This device helps to prevent further damage caused by entanglement by alerting the crew to stop the ship and retrieve the array to remove nets. (c)Modifications to smooth array hard points, referred to as the y-joint modification, consist of a hard plastic shell (over the tow cable y-joint). It provides a smooth surface (over a once blunt design) and lets the nets glide over this area. However, there are still areas of the array that are prone to net entanglements (that now occur further down the array). (d)Hardware and sensors are used to locate and recover lost arrays, but that goal is not within the scope of this topic. All of these items provide help in dealing with net entanglements and can minimize impact but none provide a solution to prevent entanglement from occurring.

There is still no known solution to prevent entanglements. Using the technology listed above, the Navy has attempted to "steer" the net entanglements and damage to less costly, less critical parts of the array. However, net entanglements still occur and the damage often leads to both potential array loss and/or the array having to be removed from the ship to be repaired.

Offerors are asked to research, develop and demonstrate new solutions to the stated problem. Solutions may include location detection (of nets), preventative devices, safe cutting devices, avoidance devices and/or damage mitigation schemes.

PHASE I: Conduct a feasibility study of how the proposed solution would prevent net entanglements and reduce damage or loss. The feasibility of the proposed solution should be visually supported by a basic working model, CAD drawings at the conceptual level, or simulation. Assess and analyze the remaining research and development required to implement the proposed solution. Clearly identify how the analysis and study address the current Navy�s towed array system and system requirements.

PHASE II: Implement the Phase I design in an Engineering Development Model (EDM) and test the EDM in a realistic environment, which might include lake or basin testing. Incorporate lessons learned from these tests into a full system design. Complete some small tests or models to demonstrate that the lessons learned were incorporated into the system.

PHASE III: Fabricate a production representative towed array system for lake and/or at-sea testing onboard a SURTASS vessel. Successful completion of this waterborne testing will enable the integration of the net mitigation solution into the Navy�s towed array systems.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Net mitigation applications can have use in any towed array application including the seismic oil exploration industry. In addition any research attained throughout this process may be beneficial to any commercial or environmental agencies/sectors concerned with fishing net entanglement.

REFERENCES:
Patents cited represent different approaches and are not to be taken as endorsements of the patent or the patented approach.
1. "Adaptive Methods Develops SHARC Tow System" http://www.adaptivemethods.com/news/detail.php?news_id=10

2. "Gel-Filled Seismic Streamer Cable" http://www.freepatentsonline.com/6879546.html

3. "Lateral Force Device for Underwater Array" http://www.patentstorm.us/patents/5443027/description.html

4. "Thin-Line Towed Array Force Measurement Apparatus and Method" http://www.patentstorm.us/patents/6253627/description.html

KEYWORDS: entanglement avoidance; towed arrays; SURTASS; fishing nets; array damage mitigation; array damage avoidance

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between April 21 and May 19, 2010, you may talk directly with the Topic Authors to ask technical questions about the topics. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting May 19, 2010, when DoD begins accepting proposals for this solicitation.

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