The OAWRS vertical towed array & handling system

FMP on the ENDEAVOR - view from starboard forward

FMP on the R/V Endeavor

Ocean Acoustics Waveguide Remote Sensing (OAWRS) is a marine survey technique capable of instantaneous imaging and monitoring of fish populations and marine life over continental-shelf-scale areas. The system scans its surroundings at a rate tens of thousands to millions of times greater than that of conventional methods and yields valuable data for those faced with assessing and managing marine fisheries. The Massachusetts Institute of Technology (MIT) partnered with BAE Systems, and sub-contractor Einhorn Engineering, PLLC to build the first dedicated OAWRS Source Array and bring the tool out of the development phase.

The OAWRS Source array is a towed, multi-element, vertical-line, acoustic array. Eight of the towbodies contain BAE Systems acoustic projectors while the ninth element, located at the bottom of the array, is a depressor weight used to maintain array verticality. Einhorn Engineering was tasked with the hydrodynamic and structural design of the towed array, as well as, the specialized handling system, which allows for tow speeds up to 7 knots.

One of the most significant challenges faced by the Einhorn Engineering staff was the need to house 900 feet of 1.13” inch diameter umbilical cable on a winch, in a constrained space, and still avoid violating the electro-mechanical (EM) cable’s minimum bend diameter while preserving the necessary cable fleet angle. Einhorn Engineering addressed this issue by developing the patent pending “Levelwinding Drum Winch.” This traversing winch eliminates the potential cable bending, added height, and obstructions presented by a traditional levelwind mechanism. And, since the cable is always on the centerline of the handling system, there is no fleet angle to contend with either.

The OAWRS Source array got the chance to prove itself during a three-week collaboration with the Norwegian Institute of Marine Research (IMR) in February-March 2014. The OAWRS system was mobilized aboard the R/V KNORR and, over the course of 3 weeks, looked at spawning populations of capelin, herring and cod.

Curved track and sheave deployed

Curved track and sheave deployed

OAWRS at-sea crew take a break from a cable repair job.