The Development of Ocean-Cable Plows

Transatlantic communication cables have been in use for more than a century. Studies indicate that more than half of the failures in telegraph cables in the past were due to fishing activity. Since 1956 high-capacity telephone cables have largely replaced telegraph cables. In these new cables 95 percent of all breaks have been due to fishing trawlers. To protect against this hazard a plow was developed that buries cable to a depth of up to 60 cm under the ocean bottom. The plow, which weighs 15 000 kg, is towed at 1 km/h and can bury cable in water depths up to 600 m. It incorporates about 50 sensors and controls including underwater TV, hydrophone, hydraulic and electrical systems, attitude, tension, and speed indicators. A 9000 hp icebreaker-cable ship is used to pull the plow. Typical plowing tensions of 15 000 kg force with peaks as great as 47 000 kgf have been recorded. By the end of 1969 about 500 km of undersea telephone cable had been buried in coastal areas off the United States, Spain, and Italy.