Handling and towing the long range side scan sonar vehicle "GLORIA" on R.R.S. "Discovery"

The paper considers the special problems associated with handling, launching, towing and recovery of the large side scan sonar vehicle known as "G.L.O.R.I.A.", (Geological Long Range Inclined Asdic), using R.R.S. "Discovery".(1) (2) A general specification and description of the vehicle is given, together with the requirements of the towing arrangement to fulfill the acoustic requirements of stability. Handling such a vehicle, (which weighs 6,6 tonnes in air), involved the design and installation of a special double fall lifting Davit , with controlled tensioning in the falls. A special cable winch for the large armoured multi-way electric cable was also installed to accomodate the 366 metres of 46m.m. diameter cable required. Acoustic requirements dictated that the vehicle should be towed some 300 metres behind the ship at a depth of approx. 120 metres, and that its stability in pitch and yaw should be of the order of ^±1/2. The towing arrangement had therefore to be developed to decouple the motion of the ship from the vehicle. Initially, a scale model of "GLORIA" was manufactured, with full instementation to obtain a measure of its stability. This was towed from the "Discovery" in representative sea conditions and the towing system proved. The first towing arrangement on the full scale vehicle was found to be rather complicated to rig, and gave excess wear on the accumulator ropes used. A much simpler system was evolved which has been used latterly with great success. Hydrodynamic stability of the vehicle when towing is almost completely controlled by the towing arrangement. Small yaw rudders are fitted to make small corrections in yaw from an inbuilt yaw gyro, and the pitch attitude may be controlled by "blowing" or flooding either of the three separate compartments of the vehicle. Both launching and recovery of the vehicle requires the services of a team of skin divers-these operations therefore require relatively calm conditions - but the veh- - icle can be towed operationally in quite rough sea conditions.