Pykrete
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Pykrete is a composite material made of approximately 14% sawdust (or, less frequently, wood pulp) and 86% ice by weight, invented by Max Perutz and proposed during World War II by Geoffrey Pyke to the Royal Navy as a candidate material for making a huge, unsinkable aircraft carrier, Project Habakkuk, actually more of a floating island than a ship in the traditional sense. Pykrete has some interesting properties, notably its relatively slow melting rate (due to low thermal conductivity), and its vastly improved strength and toughness over pure ice, actually closer to concrete. Pykrete is slightly harder to form than concrete, as it expands while freezing, but can be repaired and maintained from the sea's most abundant raw material.
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[edit] History
Pyke managed to convince Lord Mountbatten of the worth of his project some time around 1942, and trials were made in two locations in Alberta. Blocks of Pykrete were attacked with various explosives and it was found that a charge corresponding to a torpedo warhead would have made only a minor dent in the planned Habbakuk carrier.
At the Quebec Conference of 1943 Mountbatten brought a block of Pykrete along to demonstrate its potential to the bevy of admirals and generals who had come along with Winston Churchill and Franklin D. Roosevelt. Mountbatten entered the project meeting with two blocks and placed them on the ground. One was a normal ice block and the other was Pykrete. He then drew his service pistol and shot at the first block. It shattered and splintered. Next, he fired at the Pykrete to give an idea of the resistance of that kind of ice to projectiles. The bullet ricochetted off the block, grazing the trouser leg of Admiral Ernest King and ending up in the wall. The Admiral was impressed by Mountbatten's unorthodox demonstration.[citation needed] Thus, the small pilot project was given the go-ahead, but the main Project Habbakuk was never put into action. The funds simply were not available due to other WWII projects, as well as the belief that the tides of the war were beginning to turn in favour of the Allies using more conventional methods.[citation needed]
[edit] Durability
Pykrete has a crush resistance of greater than 21 megapascals (3,000 psi) so a 25 mm (1 in) column could support the weight of a typical car. The wood pulp also makes the pykrete stable at higher temperatures. If a .303 caliber bullet is fired at the pykrete, it will penetrate only 16 cm (6.5 in).
For example:
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| The above image shows a 1 gallon milk jug filled with a 10% mixture (by weight using sawdust). | The above image shows that same milk jug after being shot with a .243 rifle at approximately 100 meters. The Winchester catalog lists stats for a .243 bullet: 100 gr bullet 1,945 ft-lbs energy. |
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| The above image shows a one inch thick 50% mixture (by volume using shredded wood mulch) hit by a single 7.62 x 39 mm rifle round fired from 30 feet which bounced off the surface. It took an additional 15 rounds of .223 fired from 15 feet to crack the block. | The above image shows a two inch thick 50% mixture (by volume using shredded wood mulch) hit by a single 7.62 x 39 mm rifle round fired from 30 feet which bounced off the surface. It took an additional 7 rounds of 7.62 x 39 mm fired from 15 feet to penetrate the block. |
[edit] Construction
Pykrete can be easily formed using water and any porous and fibrous material, such as shredded paper or sawdust. Anything that can be molded with this wet pulp will freeze and become strong and non brittle.
[edit] External links
[edit] References
- Collins, Paul (2002).The Floating Island. Cabinet Magazine, Issue 7, Summer 2002. Retrieved 23 July 2004.
- Perutz, M. F. (1948). A Description of the Iceberg Aircraft Carrier and the Bearing of the Mechanical Properties of Frozen Wood Pulp upon Some Problems of Glacier Flow. The Journal of Glaciology, 1 (3), 95–104
