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The underwater workhorses

Posted in Exploration, Science, Sea, Technology on Friday, 29 July 2011

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This edited article about submarines originally appeared in Look and Learn issue number 998 published on 25 April 1981.

mini-sub, picture, image, illustration

The Vickers mini-sub, an undersea workhorse. Picture by Wilf Hardy

The midget submarine Pisces III was in trouble. She had finished a work session on the sea-bed and was being hauled to the surface when an auxiliary hatch broke open, flooding part of the craft and causing the hoisting cables to snap. Uncontrollably, Pisces III sank 480 metres back to the bottom. She had been engaged in digging a trench and laying a new transatlantic telephone cable, and everything had gone well – until now.

The accident happened on 19th August, 1973, 250 kilometres off the west coast of Ireland. Rapidly the rescue attempt became a desperate race against time. The depth was too great for divers to operate, weather conditions were poor, and most critically, the two men in the vessel had only a few hours’ air supply.

That a successful rescue was made was due to the efforts of two sister-midgets, Pisces II and Pisces V, and a strange-looking, unmanned American salvage vessel known as CURV (Controlled Underwater Recovery Vehicle). It is the deepest underwater rescue in the history of the sea.

In 1966 CURV had been involved in another dramatic incident when an American jet bomber and a tanker aircraft collided in mid-air off the Mediterranean coast of Spain.

The bomber was carrying four unprimed H-bombs, three of which fell on land and were rapidly recovered. Finding the fourth, which fell into the sea, was a more difficult proposition, but was located by an American midget submarine and recovered by CURV.

Since the end of the Second World War, there has been a tremendous increase in the production of submersibles for peaceful purposes. Bathyscaphes – underseas observation chambers which can withstand the immense pressures at great depths – have explored the deepest parts of the ocean. In 1960 the Swiss-built US Navy Trieste, the most famous of these craft, made the record descent to nearly 11,000 metres.

At this time bathyscaphes were limited in performance because they were “dumb”; nautically-speaking they could not power themselves. They had to be suspended from surface vessels, which are subject to all the variations in winds and waves, and these were consequently transmitted to the bathyscaphe. This, together with the “drift” of the suspension cable or cables, could make precise positioning and observation very difficult.

Obviously it was desirable for such submersibles to have their own means of propulsion. Trieste’s successor, Trieste II, can submerge, surface, and manoeuvre over short distances and for short periods of time at depths of up to 3,500 metres.

The US Navy has also produced two major developments in rescue technique. These are known as the DSSV (Deep Submergence Search Vehicle), and the DSRV (Deep Submergence Rescue Vehicle).

Previous rescue chambers which joined with a stricken vessel from the outside had to be lowered from a surface vessel. The DSRV has the enormous advantage of being able to manoeuvre independently to link with the disabled submarine, and is capable of bringing up 24 people at a time.

There has also been a great increase in the number and efficiency of small underwater vessels used for commercial purposes. Midget submarines are now regularly employed in checking underwater oil and gas pipelines, power and telephone cables, sewer outfalls, and support structures of oil and gas rigs, as well as locating and recovering equipment “lost overboard”.

One midget submarine has even made a comprehensive photographic survey of a 1,500 year-old Turkish galley in the Aegean Sea. It was a task which would have taken divers months. The sub did it in an hour.

The range of undersea activities in which small sumersibles are engaged grows ever larger. They are, for example, working for the fishery research departments of various countries, particularly Japan, specifically investigating the migratory habits and spawning and feeding grounds of commercially important species.

Mini-subs have been employed to drift with the great North Atlantic current, the Gulf Stream, which runs up the east coast of North America, and then turns eastwards to bring warmth to Britain and other countries on the western seaboard of Europe. For many years this has been intensively researched by surface vessels. Now submersibles are finding out what goes on at various depths.

But it is not all serious oceanic research. At the other end of the scale, small submarines have even been used in tourism. A notable example was the “tripper” submarine, one of the more novel attractions of the Swiss National Exhibition, held at Lausanne, on Lake Geneva, in 1964.

We all know that in 1969 the American “Stars and Stripes” was planted on the Moon. What is much less well-known is that, at about the same time, a midget submarine did the same thing on the bed of the Pacific Ocean, at a depth of over 475 metres.

This latter achievement, though the less dramatic of the two, was perhaps the more significant in that the oceans of the world offer us more riches than does Space, at least in the short term. For instance, there are vast mineral resources.

The mean depth of the oceans’ floor is at least 3,500 metres, making the greater part of it inaccessible at present. But, with the advance of technology, we shall be there before long.

There is also great potential in underwater transport. Submarine oil-tankers, as big as any of the surface tankers of today, are on the drawing-boards. It is envisaged that these huge vessels will travel at over 30 kilometres per hour, at a depth of around 130 metres, well below any disturbances on the surface, along safe courses that will have been charted by much smaller submersibles.

However, in the meantime the huge nuclear submarine warships of the world’s major powers will continue their ceaseless patrols – a terrible threat, but also, in a sense, guardians of peace. A major nuclear “strike” on land by one nation would bring instant retaliation from the depths, even if no land-based installations were operative, causing devastation to aggressor and defender. That is a most powerful argument for maintaining even an uneasy peace, and one in which the nuclear submarine has a major say.

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