During World War II the Allies actively recruited the inception and development of new and unique weapons. They knew that innovation and creativity would be the juggernauts of the war. Ideas from making bats carry incendiary devices to the A-bomb were pursued, but perhaps none were as hugely ambitious as the aircraft carrier Habbakuk.
When Britain was taking a pounding from German U-boats they were desperate to build a ship that would not fall victim to Nazi torpedoes. The Habbakuk was destined to be a 2,000 feet long, 300 feet wide, and 2 million ton aircraft carrier with a hull 40 feet thick—made of ice that could take a few Nazi torpedoes. It was formidable enough to be dubbed a floating island.
Ice is relativity easy to come up with, thus should make for easy repairs when needed. Ice should be pretty durable, being the stuff that sank the Titanic, and like that famous predecessor, Habbakuk was purposed to be virtually unsinkable. The ship might have been, but the plans were not.
Originally the Habbakuk was the brainchild of Geoffrey Pyke, a boffin renowned for his difficult-to-realize ideas. That notwithstanding, in 1943 he managed to sell Churchill on the plan of building a super-sized aircraft carrier for the Atlantic that could take on the U-boats. Its armaments would have included 40 dual-barreled 4.5″ DP (dual-purpose) turrets and numerous light anti-aircraft guns, and it would have housed an airstrip and up to 150 twin-engined bombers or fighters.
With steel being at such a shortage, ice was deemed to be the building material of choice because it was easy to acquire, buoyant, and sturdy enough to take a few hits. Problematically, it turned out when ice was frozen into the blocks that were meant to construct the hull, it wasn’t as strong as a glacier. In fact, a blow from a hammer would break the block. There was little hope that the hull could take a torpedo. The plan seemed doomed until a short time later that year when New York Polytechnic redesigned ice to be more durable by adding 14% cellulose—in the form of sawdust, wood chips, and paper shreds—to the ice. The new ice blend was christened Pykrete for the creator of the plan, and it retained the affable cost and buoyancy while adding the desired strength. There was finally a practical means to make the ship.
A smaller scale version of the ice ship was built and tested in Patrica Lake of Alberta, Canada. It lacked the incredible bulk of the Habbakuk, being a mere 30 by 60 feet, and kept refrigerated with a one-horsepower engine. But it floated, and it proved to be able to last through the hot summer months without melting.
However, the Habbakuk itself was never begun. The plans were mothballed once it became apparent that aside from the enormous expense of the project, the amount of wood pulp needed for the pykerete would impact paper production, the amount of steel tubing it would require would deplete reserves for conventional warships, and it required an absurd quantity of cork for insulation. Moreover, the ship’s top speed of six knots made it impractical. It didn’t live up to the biblical book for which it was named (with an accidental spelling flourish added by a clerk): “…be utterly amazed, for I am going to do something in your days that you would not believe, even if you were told.” ( Habakkuk 1:5, NIV)