Ice Dreams

Ice Will Win the War?

Icebergs in the Arctic Iceberg Depiction an iceberg under the surface of the water While he was resting, Pyke’s thoughts quickly turned from the snow in Norway to the giant icebergs floating in the Atlantic. After the sinking of the Titanic and the subsequent attempts of ice patrols to blast them apart, it was well known how strong and virtually indestructible icebergs are. If icebergs were so large and so strong, Pyke reasoned, why couldn’t they be used to solve the aircraft-carrier problem in the Atlantic? Pyke became obsessed with the idea of breaking off huge sections of ice from the Arctic icecap and towing them to the war zone. The enemy would never expect it. Pyke believed that this idea was the one that would win the war.

Pyke believed that the accessibility and size of icebergs would provide the perfect platform to build an enormous floating “bergship.” This bergship could be towed into the Atlantic, serving as a refueling station for planes and thereby eliminating the need to stay close to land. The planes would be better able to protect the vulnerable merchant ships as they crossed U-boat Alley.

The idea was presented to the desperate prime minister and, on December 4, 1942, Churchill dictated a “Most Secret” memo detailing how he felt the ice airfields should be constructed. In his memo, Churchill admitted that his knowledge of the properties of ice was extremely limited, but he felt that the project could be made to work.

There were many flaws in Churchill’s original memo. After reviewing it, the British Admiralty stated that it would be necessary for the iceberg to have a minimum of a 50-foot freeboard for a flight deck in the middle of the ocean. Ninety percent of a typical iceberg’s bulk lies underneath the water’s surface. This means that the iceberg would need to be over 500 feet tall if it were to have the minimum necessary freeboard. A 500-foot-tall iceberg raises many challenges. The drag created by an iceberg of this size would make it very difficult to maneuver. To correct this problem, it was decided that the iceberg would be hollowed out to make an ice vessel of more conventional form; however, this presented its own set of obstacles. The more “hollow” the iceberg; the less indestructible it would be, eliminating the properties that made the use of icebergs promising in the first place. Because they would be so much smaller than traditional icebergs, they would also require continual refrigeration and an insulating skin. Although these problems stood before them, the ice project continued to build steam into the new year.

Ship of Ice

RMS Queen Elizabeth Patricia Lake in Jasper, Alberta Detailed plans for the full-scale Habbakuk drawn up in 1943. Photo Courtesy of Susan Langley Interior depiction of full-scale Habbakuk. Photo Courtesy of Susan LangleyBecause Churchill was desperate for a way to win the war, after a surprisingly short discussion, it was decided that an iceberg aircraft carrier would be built. The proposed dimensions for this vessel were 2,000 feet long by 300 feet wide at the beam and 200 feet gross depth. She would have displaced an astounding 2,200,000 tons of water – 26 times that of the RMS Queen Elizabeth, the largest superliner of the time. It would be necessary to keep the carrier cooled to prevent the entire ship from melting underneath its cargo and crew. For this, 20 electric motors would be supplied from a turboelectric generating plant. To make the carrier maneuverable, it would need to have a minimum speed of seven knots. The proposed carrier would require over 120 tons of diesel oil per day with enormous tanks that could hold enough fuel for a 7,000 mile nonstop journey. The engines would need to produce only 30,000 horsepower to enable the carrier to reach the minimum speed of seven knots.

In early 1943, the Admiralty approached the Canadian government to solicit their assistance in conducting a feasibility project which would research the costs and construction of the vessel. It was at this time that the project received its name – Habbakuk. Dubbed so by Pyke, the name was a misspelling of the Old Testament book of the prophet Habakkuk, which states, “…regard and wonder marvelously. For I will work a work in your days which ye will not believe, though it be told to you.” (Habakkuk 1:5)

Research took place in various locations throughout Canada because the cold temperatures in the north provided much longer working periods throughout the year. Testing began in these various sites including Ottawa, Saskatoon, Montreal and Alberta. Most of the designing of the model was to take place in Ottawa; however, Patricia Lake in Jasper was chosen as the site for the building of the 1:10 model of the bergship that was to be built the following winter. The site was chosen for its cold weather, remoteness, railroad connections and, most importantly, for its readily-available source of labor. Conscientious objectors of the war, a camp of Mennonites, had already been sequestered so that ski paratroopers could be trained in the area. The Mennonites were available to work and would not notice the addition of extra military personnel.

Project designers planned to build the Habbakuk model out of frozen blocks of lake ice, but it was soon realized that it would be nearly impossible to build a carrier of the dimensions required out of lake ice. First, it would be nearly impossible to cut pieces of an iceberg which would be large enough to be of use in the project. Ice was also found to have poor qualities as a construction material. Its tensile strength, and its modulus of rupture – measured by supporting a beam of ice at its ends and applying pressure in the middle until it breaks - were both very low and unpredictable. As an example, ice has a modulus of rupture anywhere between 22.5 kg/cm² and 5 kg/cm², whereas a beam of pine wood has a modulus of approximately 800 kg/cm². Based on these calculations, it was easy to see that while ice was plentiful and held up well against an ocean liner, it might not be able to hold up as well against torpedoes or bullets.

Pulp Provides Progress

Wood pulp Supermarine SpitfireAs the British and Canadians were running into problems with their design, two researchers at Brooklyn’s Polytechnic University were also studying the various properties of ice and ways to strengthen it. When Pyke learned that something else would need to be done to ice to strengthen it, he consulted with Max Perultz (who later was to win a Nobel Prize). Perultz improved on the work done at Brooklyn Poly and found that adding any proportion from 4-15 percent of wood pulp to water before it freezes would significantly strengthen the resulting material. This new mixture would have a much higher modulus of rupture - up to three times that of plain ice - and was much more consistent, with less than 25 percent variability. Unlike regular ice that shatters easily when hit with something like a hammer or shot with a bullet, this new material did not shatter when hit, and was so ductile that it could easily be machined on a lathe. The resulting material, which was as hard as concrete and more resistant to melting, was named Pykrete for its similarity to concrete and the man who saw fit to work with it. Although the invention of Pykrete did seem to solve many of the problems associated with the Habbakuk project, such as melting, buoyancy and strength, it added its own set of problems, such as the additional costs and manpower required for such an undertaking.

The invention of Pykrete helped to solve many of the problems caused by using ice as a construction material. The use of Pykrete would change not only the properties of the ship, but the look as well. Although it was being called a “bergship,” this vessel would not look anything like an iceberg. The entire hull as well as the flight deck was to be sheathed in timber; below that would be the cooling system, insulation and ice. Although a maximum speed of seven knots would not be sufficient for outrunning enemy ships, this would more than sufficient for the Habbakuk. The Pykrete would give her such a resistance to attack that even a torpedo would only make a small “bruise” of about three feet. Her incredible floating ability proved that even such a hit would not threaten her buoyancy and the cooling system would have sealed up any damage while ice formed in the damaged area.

An enormous crew would be necessary to man such a vessel. The Habbakuk’s crew was to consist of 334 officers, 40 warrant officers, 164 chief petty officers and over 1,052 enlisted crewmen. Throughout her two decks of hangars, she would have been able to hold 200 Spitfire and 100 Mosquito bomber aircraft. To reduce material costs, Pykrete ramps would be used to transport the aircraft to the deck, rather than more traditional lifts.