At some point during World War II, loony solutions to practical problems really started to shine. There were pigeon-guided missiles, shark repellent, and giant aircraft carriers made of ice. Well, almost. The ice aircraft carrier was a legitimate plan in World War II, mostly because military intelligence discovered Pykrete, the substance that melts so slowly it might as well be concrete.
Geoffrey Pyke invented Pykrete as a response to the steel shortage at the beginning of World War II. Pyke was a remarkable man, who became a war correspondent during World War I and traveled secretly into Berlin under a false American passport. When he was captured and sent to an internment camp, he and a friend that he made at the camp obsessively planned for escape. When they finally managed to slip past the fences, they walked to Holland, through occupied territory and driving rain, becoming the first English men to escape from Germany. Pyke went on to become the academic eccentric, founding an infant school at his house when his son was born, and dabbling in whatever profession he thought might make him some money.
When World War II broke out, he went to work for the war effort, and was most concerned with the lack of steel. The substance was used in everything, and so constantly in short supply. Pyke went looking for the perfect, cheap, and easy-to-make substance to replace it, and stumbled on Pykrete. Put a mix of water and fourteen percent sawdust in a mold, let it freeze, and you have Pykrete. It doesn't shatter like ice, it's strong enough to use in building projects, and strangely, it doesn't appear to melt.
Although Geoffrey Pyke seemingly had the kind of life that would make for a fantastic action movie, he's overshadowed in the Pykrete narrative because there's an even better story associated with the substance. In order to get Pykrete to be taken seriously, Pyke badgered Lord Mountbatten, the Chief of Command Operations, to check out what the substance could do. Whatever he showed Mountbatten impressed the man so much that he showed it to Winston Churchill - while he was in the bath. There is probably no greater way to show how nutty World War II was than contemplating the fact that a man, even a high-ranked man, was able to sweep past security, walk into a room with a naked, wet, and reclining wartime Prime Minister, and drop an unidentified object into his bathwater. Both men looked at the block of Pykrete. Time passed, and things probably got a little awkward between them, but the Pykrete didn't melt — or rather, it melted at such a slow rate that it proved to be as sturdy as steel.
Pykrete can be planed like wood, it has the same resistance to bullets as brick walls, and a one-inch column of it can support a car. The British Military took at look at all these qualities and came up with Project Habbakuk, a sort of Navy by Mister Freeze. Although Pykrete was heavy and unwieldy on land, it has the exact properties needed in the water. It was strong, shatter resistant, and would be floating on an ocean of repair materials. All ships had to do was keep refrigeration units aboard to reverse the minimal melting that their Pykrete hulls experienced and freeze new pieces of Pykrete to use in repairs.
The Pykrete could also be used in offense. Many of the ships at the time expended a lot of energy and time keeping ice off. The refrigeration units could be used to spray other vessels and freeze their weapons and instruments until they were disabled. That's right, the ice boats would come complete with freeze guns. The center of this project would the The HMS Habbakuk, a 2000 foot long aircraft carrier made with forty foot blocks of Pykrete, weighing over 2 million tons. (By comparison, the largest ship out at that time was 86,000 tons.) They even built a 60 foot prototype, under Pyke's direction.
The British Military eventually decided that the ten million pound price tag for a carrier was not something they were willing to risk. Although Pyke pushed for Pykrete to be used in everything from ships to skyscrapers, the substance never really caught on, despite being fairly practical. Perhaps the outright guarantee of constant maintenance scared people off?
Still, the idea will always be out there. Perhaps, one day, there will be Pykrete spaceships. Or Pykrete installations on Saturn's moon Enceladus. Pyke might be vindicated in the end.