Sunday, 28 June 2009

Sources of information about Project Habbakuk

The Wikipedia article on Pykrete cites these properties. While its crushing strength is inferior to concrete, it compares favourably weight-for-weight. It has greater tensile strength, and is far less dense.

Interestingly, it is slightly denser than ice (0.98g/ml, compared with 0.91g/ml for pure ice), and a simple chunk of pykrete would float far lower in cold water than a similar-sized chunk of ice. I should be able to confirm this with my own samples, using the Archimedes principle.

Polymer scientist Herman Mark was the first to propose using wood pulp to strengthen ice, and describes the proposal in his 1993 autobiography, From Small Organic Molecules to Large.

Max Perutz published this schematic diagram of the bergship and described further properties of pykrete in his 1948 paper, A Description of The Iceberg Aircraft Carrier, in The Journal of Glaciology, volume I. In my next post, I shall discuss data from this paper.

Perutz discusses his wartime experience and his work on the project in his essay Enemy Alien published in I Wish I'd Made You Angry Earlier and in Is Science Necessary? His biographer, Georgina Ferry, expands further in Max Perutz and the Secret of Life (2007).

J D Bernal
's part in the project is described in two biographies: J.D. Bernal: A Life in Science and Politics by Brenda Swann and Francis Aprahamian, and Andrew Brown's J. D. Bernal: The Sage of Science.

While David Lampe's 1959 biography, Pyke, the Unknown Genius, gives a particularly fanciful account, it does provide this fabulous cutaway diagram of the proposed HMS Habbakuk.

There are apparent discrepancies between the various accounts. I hope to make a trip to Kew to visit the National Archives soon. They have various documents relating to the project, including Adm. Noble's reports on Habakkuk/Tentacle and Proposals and inventions of Mr Geoffrey Pyke; gravity propelled ball bomb, pykrete and power driven rivers which may help to clarify the history. Or else muddy the waters still further with a mush of wood pulp.

Thursday, 4 June 2009

The Berg Ship

In future posts, as well as my home experiments, I will delve further into some of the fantastic personalities and myths behind Project Habbakuk, but here’s a brief introduction.

In 1942, the Allies were under attack by Axis forces in the Atlantic. They needed a way to improve the efficacy of their short-range aircraft, and started to look at ways to provide floating platforms to act as aircraft carriers in the North Atlantic.

Projecy Habbakuk was the brainchild of Geoffrey Pyke, an eccentric who had managed to get the ear of Lord Mountbatten and Winston Churchill. He proposed the construction of vast ships made of ice – its natural buoyancy would protect them from sinking in the event of enemy shelling, and the raw material (water) for their repair was virtually free. However, its brittleness and tendency to creep presented difficulties.

Pyke gained scientist J D Bernal’s support to develop the project. Bernal suggested his former student, Max Perutz, who had worked extensively on the properties of ice. Work was slow to start with, until Pyke sent Perutz a paper referring to the reinforcement of ice with microfibres derived from wood pulp. Tests on this material (given the name “Pykrete”, in honour of Geoffrey Pyke) were encouraging, and Perutz was set up in a lab in the cold stores below Smithfield Market in London.
Smithfield Market

Pykrete was dramatically stronger than ice and resistant to melting. Military chiefs were so impressed that they instigated a pilot project to build a model ship in Patricia Lake in Canada. The technical issues were extreme, however, and the cost of machinery needed to freeze the wood pulp and of iron for reinforcement of the bergship negated the cheapness of the raw materials. Furthermore, developments in aircraft design and deals made with the Portuguese to use the Azores for refuelling stations had effectively made the project redundant, and the model ship was scuttled in 1943.