In 1941-1943, the Axis U-boats dominated the Atlantic, and the Allies were looking for an answer. The airplane was an effective anti-submarine weapon, but the logistics of using planes in the Atlantic were daunting. Aircraft carriers were urgently needed in the Pacific and Mediterranean. Land based planes' range was limited, and could only cover portions of the Atlantic. So there existed a "black gap" in mid-ocean, where the U-boats could roam at will.
So the naval staff of Britain came up with a remarkable idea, which was named Project Habakkuk: to build a gigantic aircraft carrier out of ice. And, as crazy as it sounds, it may have worked.
Normal ice shatters, and melts. A British engineer, Geoffrey Pyke, developed a mixture of ice and wood pulp called Pykrete. The new material was surprisingly resistant to blunt force. As temperatures rose, the wood pulp formed a fuzzy coating over the ice, insulating it from further melting. Experiments on Pykrete were conducted in top secret, in a refrigerated meat locker beneath Smithfield meat market in London. Frozen animal carcasses were used to hide the research areas.
The size of these ships would have been remarkable. The initial design was for a floating airfield 5000 feet (1524 m) long, 2000 feet (610 m) wide, and 100 feet (30 m) high. Later designs were shortened to 2000 feet long. They would have a displacement of 1-2 million tons. By comparison, the huge aircraft carriers in use today by the U.S. Navy are just under 1100 feet long and weigh 101,000 tons.
They could handle the biggest planes of the era, and carry enough food and fuel to resupply them for months. They had externally mounted power plants capable of propelling them at 6 knots, and would act as floating airfields in the North Atlantic. They were cheaper, and could be built much faster, then a conventional carrier, and had an estimated lifespan of 6-18 months (likely longer, as it turned out).
To see if the idea would work, a 60 foot scale model was built at Patricia Lake, in Canada, over the winter of 1942-1943. To preserve secrecy, the Pykrete blocks were made at Lake Louise, and moved to Patricia for assembly. And it worked quite well. In Summer the wood pulp covered the ice and slowed the rate of melting. Auxiliary cooling equipment was developed that could be carried outside the hull.
Churchill thought quite highly of the idea. The ships would be built in Canada, and to this end the Canadians began assembling enough ice and wood pulp to begin construction.
More and more technical problems, however, came up, and by the time they were sorted out the tide had started to turn against the Axis. The Liberty ships were being built faster than U-boats could sink them. The Allies had developed small, relatively cheap, escort aircraft carriers, which were now providing air coverage to Atlantic convoys. Long range patrol bombers had improved. And so one of the most remarkable ideas in naval history was quietly shelved.
The model built at Patricia Lake took 3 years to melt, showing that Pykrete was quite durable. It was allowed to sink into the lake.
And there, at the bottom of Patricia Lake in Alberta, Canada, lie the remains of Habakkuk. The test ship's frame, with a small motor and refrigeration plant, are now visited by scuba divers. Jasper National Park receives many visitors every year, most unaware that at the bottom of a small, serene, lake is all that's left of this remarkable idea.