Project Habbakuk was the name given to a British project to design a very new sort of aircraft carrier. Faced with limited access to steel and aluminum, a scientist named Geoffrey Pyke proposed a quite different idea. He suggested building an aircraft carrier from ice; the material could withstand torpedo fire, and was available at a much lower cost. In addition, it was naturally buoyant, and durable in cold temperatures. Ice alone was too fragile, but when a small amount of wood pulp was imbedded into the ice, it became quite bulletproof. This mixture of ice and wood pulp is called pykrete.
With the support of Winston Churchill, active work and testing began. They soon determined that refrigerant would be necessary to maintain adequately cold temperatures to keep the pykrete stable; however, they also found that a very small engine could adequately cool the pykrete. A 30-foot by 60-foot small test model was produced and set into the waters of Lake Alberta, Canada. The pykrete vessel had a few distinct drawbacks. It was, even with a large rudder, difficult to steer, and it was very slow, resembling more of a floating island than a ship. Work on the project was eventually abandoned, but the test ship took three full years to melt completely in Lake Alberta.
Although it was abandoned, Project Habbakuk was not a failure. In fact, the tests were successful. Unfortunately, the ship still required funds, wood pulp, and steel, and these were not adequately available. In addition, over the course of the war, the flying range of aircraft had increased, reducing the overall need for this sort of floating island-ship of ice.
Experiments continue with pykrete in cold climates. Engineering students have attempted to build domes, and even a model of the Sagrada Cathedral using pykrete; however, few practical uses have been found for the material, given its need for stable, cold temperatures.