Bob Goddard         Senior Physicist         EIS Department         Applied Physics Laboratory         University of Washington	APL-UW is supporting simulation-based design and evaluation of the Tripwire torpedo defense system. Under funding from ONR Code 321, APL-UW will set up simulation runs to generate simulated signals for the Tripwire system, using existing software tools including SST, CASS, and Matlab. We will also modify SST as required to improve its realism and usability for Tripwire simulations, and provide support and advice on simulation issues for Tripwire project members at ONR, NUWC-Newport, ARL-JHU, and elsewhere. Issues to be addressed include the choice of material for the encapsulant, transmit power requirements, the consequences of partial failure modes, interference of active detection and ranging by noisy torpedoes, how to make use of intercepted active transmissions from the torpedoes, and the effects of the wake of the towing ship. Tripwire is the sonar component of the proposed AN/WSQ-11 system, which is intended to defend U.S. surface ships from torpedo attack. The current proposed system is a towed active system with separate transmitter and receiver on the same cable. The currently proposed receiver consists of a sparse 3D arrangement of hydrophones embedded in a cylindrical encapsulant; the transmitter is a high-power line array.