Development of advanced secondary cable for the full ocean depth ROV Kaiko

Kaiko has accomplished more than 20 dives to 11000 m at the Challenger Deep in the Mariana Trench since 1995. On May 29th in 2003, Kaiko made 296th dive at a depth of 4675m to recover bore whole data from the A-CORK. After completion of the data recovery, the secondary cable of Kaiko was snapped, and the vehicle was lost. After the accident, secondary cables including the snapped cable were examined at JAMSTEC. The secondary cable was snapped at the end of the cable because of the structural defect of the cable termination. Also, it was made clear that the cable strength has weakened by 30% all along the cable. This is because of buckling by micro-bending of the aramid fibers under extremely high water pressure. In order to avoid the buckling, we knew that it was necessary to get a pressure balance between each fiber. For this purpose, JAMSTEC has developed two types of advanced secondary cables as first stage prototype for the Kaiko. In one of the secondary cables, aramid fiber was made up to FRP same with a strength member for the primary cable. In the other new secondary cable polyarylate fiber was just bundled.