Loss of the Full Ocean Depth ROV Kaiko - Part 1: ROV Kaiko - A Review

Hiroyasu Momma, Masayuki Watanabe, Kikuo Hashimoto and Shozo Tashiro Research Support Department, JAMSTEC Yokosuka, Japan

ABSTRACT cable was snapped will be analyzed and discussed.

Kaiko has been the only one full ocean depth survey system in the SHORT HISTORY OF THE ROV KAIKO world since 1995. She has accomplished more than 20 dives to 11000 m at Challenger Deep in the Mariana Trench. Unfortunately, in May Kaiko means trench in Japanese. As its name, the ROV Kaiko was 2003, the secondary cable of the Kaiko was snapped during 296th dive designed to dive into the deepest trench in the world. She was at a depth of 4675 m, and the vehicle has been missing. The secondary originally built in 1993, and made a trial dive to the Challenger Deep in cable was snapped because the aramid fiberss had weakened by the Mariana Trench. However, just before she touched down the bottom, bending under extremely high water pressure, and local fatigue of the black out occurred by failure of the optical fiber in the secondary cable strength members occurred at the cable termination. Taking into (Takagawa et al, 1995). The optical fiber and strength members were consideration the valuable lessons of the accident, JAMSTEC will build snapped by micro bending, both under extremely high water pressures. new and advanced Kaiko as early occasion as possible. In order to avoid the damage, plastic groove to lay the optical fiber, and strength members were filled with gel, which allowed them to move KEY WORDS: ROV; Kaiko; launcher; vehicle; lost object; electro- smoothly. Several improvements were took place not only for the optical cable; Challenger Deep; Mariana Trench; aramid fiber secondary cable, but also for the total system, such as launch/recovery and winch system. The second trial dives at the maximum depth were INTRODUCTION carried out in March 1995 at a water depth of 10911 m in the Challenger Deep (Kyo et al, 1995). The dives were successful and In May 29th in 2003, the Kaiko completed the 296th dive at a depth of Kaiko left a memorial flag on the deepest seafloor. The dive by ROV 4675 m in the Nankai Trough 130 km southeast off Cape Muroto in Kaiko was indeed 35 years after the historical dive by the bathyscaphe Shikoku Island. By successfully recovering bore hole data from ODP Trieste in 1960. In 1996, mother ship of the Kaiko was converted from Hole 808I the operator tried to reel in the secondary cable to mate the R/V Yokosuka to R/V Kairei. In 1998, scientific diving in Mariana launcher and the vehicle. However, they could not be mated, and the Trench were carried out to collect biological samples and pressure optical line and the electricity failed successively, a black out has resistant bacteria in sediments at water depth of 10911 m. occurred. Then, the primary cable was reeled in slowly. After the Because of complicated underwater and on board systems, it took long launcher surfaced, they found that the vehicle end of the secondary time to be fully operational until 1997. From 2000, operation of the cable was snapped, and the vehicle did not appear on the surface. Soon Kaiko was entrusted to Nippon Marine Enterprises Ltd., one of the after the launcher was on deck, clear radio signal of the beacon from sister companies of JAMSTEC. Between 1997 and 2003, the Kaiko the vehicle was received on the R/V Kairei, and they knew that the worked very hard for scientific and engineering purposes. vehicle was on the surface. The radio signal stopped after three Unfortunately, in May 2003, secondary cable, which connects launcher successive pulses, and it was never heard since then. Extensive search and vehicle, was snapped and the vehicle was lost at 296th dive. for the vehicle was carried out until June 21st from surface and air, based on the simulation by taking current and wind profiles into DESCRIPTION OF THE KAIKO SYSTEM consideration. Unfortunately, we could not find any indication and parts of the vehicle at all. The Kaiko system comprises of launcher, vehicle, primary cable, This paper is Part 1 of the three successive papers on the loss of the secondary cable, launch/recovery system, passive heave compensator, Kaiko vehicle, which describes the short history of the Kaiko, traction winch, storage winch, on board control/power unit, and R/V significance of the full ocean depth ROV, and background of the Kairei as a mother ship. Specification of the system is listed in Table 1 accident. In Part 2, search tactics and analysis why the vehicle was not (Momma et al, 2000a). Total length of the primary cable is 12500 m discovered will be described. In Part 3, the reason why the secondary and 44 mm in outer diameter, and the secondary cable is 250 m in