Editing Project Habakkuk (section)

=== Pykrete ===
{{Main|Pykrete}}
[[File:Block of pykrete.jpg|thumb|A block of pykrete]]
In early 1942 Pyke and Bernal called in [[Max Perutz]] to determine whether an icefloe large enough to withstand Atlantic conditions could be built up fast enough. Perutz pointed out that natural icebergs have too small a surface above water for an airstrip, and are prone to suddenly rolling over. The project would have been abandoned if it had not been for the invention of [[pykrete]], a mixture of water and woodpulp that when frozen was stronger than plain ice, was slower-melting and would not sink. Developed by his government group and named after Pyke, it has been suggested that Pyke was inspired by [[Inuit]] sleds reinforced with moss.<ref>{{cite book |last=Gay |first=Hannah |title=''The History of Imperial College, London, 1907–2007'' |publisher=Imperial College Press |year=2007 |page=273 |isbn=978-1-86094-708-7}}</ref>  This is probably apocryphal, as the material was originally described in a paper by [[Herman Francis Mark|Mark]] and Hohenstein in Brooklyn.<ref name="perutz" />

Pykrete could be machined like wood and cast into shapes like metal, and when immersed in water formed an insulating shell of wet wood pulp on its surface that protected its interior from further melting. However, Perutz found a problem: ice flows slowly, in what is known as [[Creep (deformation)|plastic flow]], and his tests showed that a pykrete ship would slowly [[Hogging and sagging|sag]] unless it was cooled to {{convert|-16|C|F}}. To accomplish this the ship's surface would have to be protected by insulation, and it would need a refrigeration plant and a complicated system of ducts.<ref name="perutz" />

Perutz proceeded to conduct experiments on the viability of pykrete and its optimum composition in a secret location underneath [[Smithfield, London|Smithfield Meat Market]] in the [[City of London]].<ref>{{cite journal |last=Gratzer |first=Walter |title=Max Perutz (1914–2002) |journal=Current Biology |volume=12 |issue=5 |pages=R152–R154 |date=2002-03-05 |doi=10.1016/S0960-9822(02)00727-3 |s2cid=30263181 |df=dmy-all |doi-access=free }}</ref><ref>{{cite journal |last=Ramaseshan |first=S |title=Max Perutz (1914–2002) |journal=Current Science |volume=82 |pages=586–590 |date=2002-03-10 |publisher=Indian Academy of Sciences |issn=0011-3891 |hdl=2289/728}}</ref>  The research took place in a refrigerated meat locker behind a protective screen of frozen animal carcasses.<ref name="cabinet">{{cite journal |last=Collins |first=Paul |title=The Floating Island |journal=Cabinet Magazine |issue=7 |year=2002 |url=http://www.cabinetmagazine.org/issues/7/floatingisland.php |access-date=2008-01-12}}</ref>