Operation Habbakuk: The Iceberg Aircraft Carrier

By Neil Taylor

A small, picturesque lake nestled in the Canadian Rockies just outside the Jasper townsite harbours a mysterious secret dating from the Second World Lake.

Patricia Lake, named after Princess Patricia of Connaught, a granddaughter of Queen Victoria, was the site of wartime experiments examining the feasibility of building an aircraft carrier out of ice.

An artist’s concept of the proposed pykrete aircraft carrier.

The idea was born at the low point of the Second World War when the German U-boat fleet was threatening to starve the British Isles of food and war materials. Despite the growing effectiveness of convoys and hunter “Support Groups” of Allied warships, German wolf pack attacks were particularly successful in the mid-Atlantic where a gap in Allied airborne coverage existed.

Desperate times called for desperate measures, and in mid-1942 eccentric British scientist Geoffrey Pyke began to promote a bizarre scheme to build an unsinkable aircraft carrier out of ice that could guard the mid-Atlantic shipping routes. He brought his idea, code named Operation Habbakuk, to Lord Louis Mountbatten, Chief of Combined Operations. Always open to the unorthodox, Mountbatten was struck by Pyke’s plan and immediately supported the venture.

The key to Pyke’s proposal was the use of pykrete, a mix of 15 per cent wood pulp and 85 per cent water, that was stronger than concrete, resistant to thawing and largely immune to heavy blows (as might be inflicted by a torpedo). Yet amazingly, it could be easily molded into different forms and shaped by saw or wood plane.

Mountbatten took Pyke’s proposal to British Prime Minister Winston Churchill where he demonstrated pykrete’s unique characteristics by floating a block of the material in the Prime Minister’s bathtub. Churchill was struck by the audacity of the plan and called for construction of a pykrete aircraft carrier 2,000 feet long and 300 feet wide with a draft of 150 feet, and capable of carrying 200 fighter planes and 100 twin-engine bombers.

The first layer of ice blocks are laid at the Patricia Lake test site.

Before committing to construction of such a colossus, a test model was required to prove the concept. Neither the British Admiralty nor American naval officials were enamored by the proposal so the Canadian Government was approached to determine both the feasibility and cost of a “bergship”.

The project was assigned to Dr. C. J. Mackenzie of the National Research Council who initially regarded it as “another of those mad wild schemes” for which the British were famous. Nevertheless Dr. Mackenzie proceeded, with assistance from western universities including the University of Alberta, to research the properties of ice. Initial ice testing was conducted at Lake Louise but a less visible locale was needed for the secret project.

Dr. Mackenzie chose Patricia Lake because it was already closed to the public for ski paratrooper training, it was close to rail facilities, and labourers were available from a nearby camp for conscientious objec­tors. Work began on the test model in mid-February 1943 when a patch of the frozen lake was cleared of snow and wooden framing and flooring was erected. The first layer of ice was laid on the flooring in early March. The entire test model was covered by a roof giving the test site the appearance of a boat house.

Problems arose almost immediately with the proposed coolant system – a brine coolant circulated through ducts in the pykrete hull. Nevertheless, a scale model, measuring 60 feet long and 30 feet wide, weighing 1000 tons, and kept frozen by the use of air circulation from a 1-horsepower motor, was completed that summer.

The ‘Boathouse’ at Patricia Lake.

While the test model did in fact float, other engineering and design problems had arisen. The complex coolant system would require piping throughout the icy structure doubling or tripling construction costs. Three hundred thousand tons of wood pulp would be required to produce the necessary quantities of pykrete causing severe impacts on the pulp and paper sector. Additionally, there was no possibility of building the full-size pykrete aircraft carrier by spring 1944, the originally established target date. Other technological innovations such as the introduction of longer range patrol aircraft with improved radar detection capabilities had eliminated the “Atlantic gap” and shipping losses were declining rapidly. By mid-May 1943 German U-boats were ordered to leave the mid-North Atlantic.

In June 1943 all testing in Canada was stopped, and despite some flagging support for the project at the August 1943 Quebec Conference involving Churchill, Roosevelt and Mackenzie King, by October 1943 the project was essentially dead. The test model on Patricia Lake had been abandoned over the summer but it took another year before it melted and sank to the bottom of the lake.

Today, metal piping and asphalt strewn across the lake bottom are all that remain of the would-be aircraft carrier. Divers can visit the wreckage, and a commemorative plaque along the shoreline of Patricia Lake memorializes one of Canada’s more unusual wartime projects.