New mini-sub. to seek out riches under the Arctic ice

Press, 29 August 1986, Page 21

New mini-sub. to seek out riches under the Arctic ice

From

MICHAEL SWISS

in Paris

While attention has been focused on the submarine searching the wreck of the Titanic, another deep-diving vessel is about to be launched — to search for minerals, oil, and gas on the hitherto inaccessible ocean floor beneath the Arctic ice.

Twenty years ago Jacques Cousteau conceived the idea of a small underwater craft and started to build it. It was to be 28 metres long and 7.4 metres wide, and carry a crew of 13 in two chambers, one at atmospheric pressure and the other highly pressurised. Those in the former would run the craft, the others would be ready to go out and work on the seabed at a depth of about 500 metres.

But only now has it become feasible for such a mini-

submarine to undertake missions that would last two weeks or more, or travel 150 nautical miles.

Cousteau’s submarine, named Argyronete after a species of underwater spider, was barely half-buiit when the project ran out of money. It was left in the care of the French Comite d’Etudes Petrolieres Marines and another French organisation, the C.N.E.X.C.0., a branch of the Ministry of Industry and Research. It was subsequently passed on to the Marseilles company Comex, which has been continuing Cousteau’s work since 1982. It is now near completion

and due for trials in the Mediterranean, after which the craft, renamed Saga-1, may go to Britain.

Providing power for the minisub required some original thinking. Saga-1 will compare well with a naval vessel. It will have a displacement of only a fifth of a full-size submarine, and will be provided with something like 60 per cent more energy by burning a hydrocarbon fuel in pure oxygen.

The heat generated causes the working fluid (helium) to expand and move the pistons. When the engine, like that in a car, goes through its cycle to the stage

when cool helium is expelled from the cylinder, it will go into an enclosed system of pipes and vessels where it will be heated once more. The concept is old, but it required modern technology to bring it to perfection. The “waste” heat output is also used to keep the divers warm.at work. A nuclear heat source, which is also being considered, would extend missions to 30 days, and let the craft travel 300 nautical miles.

The nuclear boiler will be put on board by cutting Saga-I’s tail section off, welding on a IOOkW reactor and replacing the tail. The length of the mini-sub will be increased to about 36m, and its name will be changed to Saga-N. Energy Conversion Systems of Canada will use the

Slowpoke-type reactor. This incorporates a safety factor which means that if the cooling water gets too hot, the reactor’s output automatically falls off. Comex expects Saga to be deployed in the repair and maintenance of oil installations, wreck recovery, and the military. The divers would be able to work attached by an umbilical cord or take packs to provide heat, energy, and a breathing mixture. The company is carrying out a series of deep diving simulations in which the divers must work in conditions identical to prolonged submersion at 500 m.

At such depths the pressure is so great that even simple breathing is exhausting. In addition, the natural components of ordinary air cause hallucinations and other symptoms. So for breathing at such depths the percentage of oxygen is reduced to 10 per cent of that in air, and nitrogen is replaced, usually by helium. Comex has succeeded in getting its divers to work with hydrogen instead, partly because of cost and partly because helium also causes breathing difficulties. This gas also has narcotic effects, but fortunately only about a quarter as severe as those of nitrogen. Further research — with a mixture which contains just under 50 per cent of each helium and nitrogen and barely 1 per cent oxygen — has been better. Comex has found the divers can work and breathe comfortably even through the nose, quite impossible with pure “oxy-hel-ium.” The way is now open for Saga 1 (or Saga-N) to venture beneath the Arctic ice, and carry out its search for oil, gas, and minerals. Copyright — London Observer Service.