What is a cableship?
Ah, the Internet! YouTube videos, social media, forums, maps, weather, the wonders of Wikipedia – so much happiness at the touch of a key. Communication is the defining feature of the modern world, but have you ever wondered how it reaches your home? Of course you have – that is why you are visiting this website.
It’s all about cables – submarine cables, that is. And how do those cables get down to the seabed in one piece? There are special ships for that, and there have been for over a century and a half.
Some History
In keeping with the earliest ships, the first cableship was not built as a cableship, but was actually a steam tug called Goliath. In August, 1850, it laid a telegraph cable between St-Margaret’s Bay in England and Sangatte in France. The cable was not a success due to signal retardation, but another attempt a year later was made using a hulk called Blazer, towed by two tugs, and led by HMS Fearless.
The demand for telegraphy grew as successful cables shrunk the world, and the need for a specialised cable-ship became more apparent. The paddle-steamer Monarch was the first ship to be permanently converted into a cableship, but the first purpose-built cableships were the Hooper in 1873 and the Faraday in 1874.
The 19th century took its last bow and the 20th century began. Technology marched on and telegraph submarine cables gave way to coaxial telephone cables, and the advent of fibre optics brought us an explosion of submarine cables. More submarine cable has been laid since the arrival of fibre optics in the 1980s than all the telegraph and telephone cables of the previous century and a half combined. Are you impressed?
All these cables were laid by cableships, so the cableship is still at the forefront of modern telecommunications. Their history includes names such as the Willing Mind, the Ampere, the Thor, the Cyrus W. Field, the Hooker, the Omega (presumably the last of its name), the Long Lines (and they were), the All America, the Relay, the Transmitter, the Restorer, the Miner (there were eight of them), the Redstart, the Stonechat, the Bullhead, the Holdfast, and the Cable Enterprise.
So, what is a cableship?
Well, it is an ocean-going vessel designed to lay and/or repair submarine cables. Its characteristics include a high degree of manoeuverability (ensured by diesel-electric engines), active rudders, variable pitch propellers, and the means for transverse thrust. Modern ships have computer-controlled dynamic positioning systems.
For much of cableship history, there have been two types: the cable-layer and the cable repair ship. These days, the capabilities of both types are combined into one ship, but originally the cable-layer was the larger of the two and laid the cables across the great expanse of ocean, while the cable repair ship was smaller and stationed close to cables, ready to put to sea to find and repair faults at a moment’s notice. For example, the Lady Denison-Pender was based in Aden during the Second World War; the fifth Retriever was based in Fiji. Cable repair ships have traditionally had only bow sheaves (those wheels on the prow or nose of the ship), whilst cable layers have often had bow and stern sheaves, and in modern times only stern sheaves for the actual laying of a cable. For both types, a large part of the internal space of a cable-ship is taken up with cable tanks.
Few cable laying ships have, in the past, been large enough to carry all the submarine cable needed for long stretches (for example, across the North Atlantic). The fourth Monarch (1946) was able to carry some 2,600 miles, or more than 4,000 kilometres, of deep-sea cable in its four cable tanks, but had to be the largest cable-ship in the world to achieve this. The laying of cable in sections was the order of the day, with the ends of the laid cable buoyed up to await a new section. If the cable end was lost, the cable-ship would have to use a grapnel towed behind it to find and grab the cable. The ends of these sections of cable would be spliced together.
But if you are envisioning a plain cable snaking across the soft, muddy silt on the gloomy ocean floor, then stop, because with the advent of telephones came the advent of repeaters. Transoceanic cable telephony needed a means to amplify the signal as it passed down the cable, and so repeaters were developed, as were passive devices called equalisers. By 1980, many ships carried their repeaters separately from the cable, which was stored in lengths, and attached as needed.
The technological development of the modern cable vessel has resulted in the multi-purpose cableship, and so the specialised cable repair ship and cable layer have been combined into one vessel. Not only that, but modern cables are thinner, more capable, and are now buried under the sea floor using ploughs to dig trenches, rather than the traditional practice of simply laying the cable on the seabed. Locating and repairing faults are these days more likely to be carried out by submersibles or remotely operated vehicles. The basic principles remain the same, though, and the importance of their work has increased with more and more cable laid for our modern, online world.
Image: Bow sheaves of the Recorder in 1954
How does a cable-ship go about its work?
First, a route study is made using existing data and charts. This study should have a depth profile, a track, and sea-bottom temperature. Following this comes a hydrographic survey of the route on which the cable is to be laid. Depth readings are taken, as well as temperature measurements and geology samples. A route through the surf zone is established and how much burial of the shore-end of the cable will be needed is established. It may be the case (and these days it is quite common) that the cable will be buried under the seabed in a trough dug by a plough further out from the coast, so detailed knowledge of the ocean floor is valuable.
The cableship lays its cable by carefully following the planned route and paying out the cable astern. The repeaters are added as necessary – at intervals as short as three miles or as long as twenty. At times, scientific instruments are included with the cable.
The cableship lays its cable by carefully following the planned route and paying out the cable astern. The repeaters are added as necessary – at intervals as short as three miles or as long as twenty. At times, scientific instruments are included with the cable.
Submarine cables are not entirely safe at the bottom of the sea. Fishing trawlers, submarine earthquakes, volcanoes, icebergs, shark-bites (no, really), shipwrecks, the Mid-Atlantic Ocean Ridge – and there are electrical faults that must be repaired. When this happens, a cable-ship must detect the location of the problem and then hook the cable with a grapnel and bring it to the surface. The crew cut the cable and test the ends to find the fault. The faulty section, once found, is replaced and the ends spliced together, before being thoroughly tested.
Image: Landing Gemini cable at Porthcurno in 1997
So, we still need cableships?
In this age of the Internet, we definitely still need cableships. In fact, we need them so much that cable layers are chartered years ahead. There are new cables needed between ports, cities, and countries all over the world. And with technology advancing at so fast a pace, old cables need to be replaced with new and more capable cables.
Cableships are not the past. They are the present, and they are the future.
Author
Duncan S. Mackenzie, RITTech, AMBCS
Digital Collections Officer, PK Porthcurno
Header image: Cableship Innovator at sea