I hope that everyone is safe and warm; many parts of the US have been hit hard by winter weather. At least you can rest content knowing that you do not live in an iceberg, though it may feel like it.
The era of World War 1 and 2 was a crazy time for inventors. Desperate for any advantage they could get, many countries invested in outlandish lines of research which might have been judged foolhardy before the war. For example, in WW1, the British Royal Navy came up with all sorts of ideas to detect and defeat German U-boats. From training seagulls to poop on periscopes to covering the ocean in paint, these ideas seem quite outlandish now. But at the time, the threat posed by submarines was considerable enough to make the Allies jump at anything which could tip the scales.
With over 1000 ships hit by U-boats by the beginning of 1942, the Royal Navy was desperate for solutions. As Britain is an island nation, it depended on materials being shipped from overseas. However, it could not manufacture ships quickly enough to secure all the shipping lines. In particular, the steel required to create ships was also needed for guns, tanks, and airplanes. So when Geoffrey Pyke suggested a radical new material for building ships, his ideas found interested listeners. Icebergs had sunk ships in the past – but what if they made an iceberg into a ship?
Pyke proposed the use of a material which was simultaneously both cheap and easy to obtain – ice. Or, rather, not just ice but pykrete. To nobody’s surprise, ice is not the best building material. It sags under its own weight, shatters easily, and, of course, melts. But by mixing water with sawdust and woodchips and letting it freeze, the ice becomes much tougher and slower melting. A (potentially apocryphal) story tells of an admiral demonstrating the strength of pykrete by firing a bullet at a block, only to have it ricochet off and nearly hit someone’s legs.
The protential of pykrete intrigued the Royal Navy, and soon Project Habakkuk was born. In Alberta, Canada, the Navy used Patricia Lake in Jasper National Park to create a test ship out of pykrete. Using pykrete, they made a 60 ft. by 30 ft. scale model which they used to test the structural strength and long-term feasibility of such a ship. However, as the tests continued it became apparent that the challenges associated with using pykrete, namely the tendency of ice to deform, meant that the ship would require more steel than initially thought. There were other problems as well, such as the fact that sailors would have to live on a ship that was literally freezing cold. This, combined with the entrance of America into the war, and Portugal allowing the Allies to use its airfields meant that this project was no longer necessary. Despite plans to build a 1.2 km long ship (that’s longer than the Vatican), the project was scrapped. You can still see the remains on the lake floor if you go scuba diving.
Since WW2, pykrete has been proposed as a building material for a variety of projects. However, it has never really gotten used for a large-scale application. However, the Mythbusters did run tests on the strength of pykrete, and even made a boat out of it. So if you have a bunch of snow and sawdust lying around this winter, why not try making an igloo out of the stuff?
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