The Ice Aircraft Carrier — Project Habakkuk

British inventor Geoffrey Pyke proposed building an aircraft carrier from 'Pykrete' — a mixture of 86% sawdust and 14% water frozen together. Pykrete was as strong as concrete but would float and would self-repair — you could shoot a hole in it and it would freeze shut. The ship, code-named Habakkuk, would have been 2,000 feet long, 300 feet wide, and weighed 2 million tons. Sixty feet of ice would have been required to protect it from bombs and torpedoes. A 60-foot prototype was built at Patricia Lake in Alberta, Canada, and it worked — it lasted the entire summer. But the project was cancelled when it became clear that building the full-scale ship would require 300,000 tons of insulation materials (more than any shipyard could supply), 84,000 tons of wood pulp, and 30,000 tons of insulation. The refrigeration system alone would have weighed as much as a conventional aircraft carrier.