BACK REFLECTION
THE CRASH OF PISCES III (SEA BURIAL, NOT BURIAL AT SEA) BY PHIL PILGRIM
J
ust over a year ago, in June, 2023, we witnessed the OceanGate tragedy. Their Titan submersible vessel was lost, and an international rescue effort was rapidly deployed. Sadly, the rescue mission was unsuccessful. Unknown to most, an event nearly identical, occurred 50 years earlier during a cable lay, and the outcome was more favourable. Here is a synopsis of that event.
CANTAT 2
In the spring and summer of 1973, the CANTAT 2 submarine cable was laid from Canada (Beaver Harbour) to England (Widemouth Bay). It was supplied by STC. CANTAT 2 was a 14 MHz coaxial cable design that
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transmitted bidirectionally in the same waveguide.
CABLE PROTECTION & PISCES III
By August 1973, post lay burial was underway. This procedure is conducted in the waters of the continental shelves where the maximum depth is only ~ 1.5km. As per the name, the armoured cable is buried under the ocean floor to further protect it from external aggression (fishing, anchors, abrasion, etc.). These days, cable burial is conducted mostly by plows that are towed behind ships. Often a plow cannot pass a repeater though its works, so remotely operated submersibles are sometimes used to bury the larger repeaters. These devices use jets of high pressure water that liquifies the soil
under the repeater. Although sea plows were first developed in the 1930’s and used ever since, they were still undergoing development in the early 70’s and were not widely used [Bell Lab’s Sea Plow I was deployed in 1966, by 1973 the mark was Sea Plow III and it could only work to 0.5 km water depth]. Likewise, Remotely Operated Vehicles (ROV’s) were relatively new and were not yet exploited for cable burial. Their early use was by navies for underwater ordinance work & salvage/ retrieval. At the time of CANTAT 2, small manned submarines were used to conduct post-lay burial of the cable in deeper water using high pressure water jetting. For CANTAT 2, a small submarine was deployed for burial on the continental shelves. It operated