WINSTON CHURCHILL said it was the only thing that ever really frightened him. During the second world war, Britain relied on essential supplies shipped over from the US and the Germans knew it. So threatening were the attacks by German submarines that the prime minister feared the country would starve. Long, grinding and grim, the Battle of the Atlantic featured some of the war’s great scientific innovations, such as sonar and short-wave radar.
Aircraft were effective U-boat hunters, but their limited range left a gap in the mid-Atlantic where the subs could prowl freely. Aircraft carriers might have solved the problem, but they were too precious and vulnerable to be risked in mid-Atlantic patrols, so convoys remained exposed.
For one man, the solution was clear. Geoffrey Pyke was the very model of the eccentric scientist. Absent-minded, forthright, manic and keen to help the war effort, he had already put forward a plan to harry the Nazi occupiers of Norway using snowmobiles propelled by giant screws. In September 1942, he sent a 232-page memo to Lord Louis Mountbatten, head of combined operations, describing his plan for aircraft carriers made of ice.
Advertisement
Pyke named the idea Habbakuk, after the biblical prophet who foretold amazing works (though he misspelled the name). He imagined bergships, as he called them, 600 metres long and 100 metres wide. With an icy hull 12 metres thick, it would be unsinkable. Any damage from torpedos could be fixed by refreezing the ship and the cost was estimated at less than half the price of a conventional aircraft carrier.
Scientific adviser John Bernal told Mountbatten it was “not a mad idea”. They presented a one-page version to Churchill, who was dazzled.
Churchill’s own inclination was to let nature do most of the work. Why not just break off a flat piece of ice from the Arctic and tow that around as a mobile airbase? Naval advisers pointed out that launching aircraft in stormy seas requires a flight deck 15 metres clear of the water. For that, a solid iceberg would have to extend at least 150 metres beneath the surface, making it almost impossible to move. Instead, as Pyke had suggested, it would have to be a hollow ice hull to make it more buoyant.
Ice the mainbrace
But pure ice would not be strong enough for such a giant vessel. Hope came from chemist Herman Mark, a refugee from Austria who had found a place at the Polytechnic Institute of Brooklyn in New York. Mark had discovered that adding wood pulp to water before freezing it created a strong icy composite.
In a secret lab underneath Smithfield meat market in London, chemist Max Perutz tested this new material, which his group named pykrete (although markrete would perhaps have been more just). Weight for weight it was as strong as concrete. A bullet would shatter a block of ice, but bounce off pykrete. According to Perutz, in one demonstration the ricochet grazed a visiting admiral.
Pykrete had other advantages: it could be sawed into shape and would melt much more slowly than pure ice thanks to an insulating woody layer that soon accumulated on its surface. Churchill saw this for himself when Mountbatten visited him while he was taking a bath and threw a block of the material into the steaming water.
“Mountbatten visited Churchill while he was taking a bath and threw a block of pykrete into the steaming water”
Even before this intimate encounter, Churchill had given project Habbakuk a high priority. Somewhere cold was needed to test the idea, so Canada lent its climate and expertise. Work began on a model ice ship at Patricia Lake near Jasper, Alberta, in February 1943. The head of the National Research Council in Canada, Chalmers Mackenzie, directed a team which included drafted pacifists, mainly Mennonites. They built a 20-metre long box of ice, based around a refrigeration unit, a network of pipes and various layers of internal insulation. Most of the team assumed it was a kind of house, a glorified igloo. But they must have caught some whiff of boatiness, because they called it Noah’s Ark.
And the ark floated – although it remained moored to the shore and confined by ice on the lake. “They never let it drift around,” says Susan Langley, who was the first archaeologist to dive down and look at the ice boat’s remains back in 1985. There, under 20 metres of near-freezing water, she found it remarkably well preserved. The skeleton of insulation and refrigeration pipes formed two walls that were still standing, and one more was intact but had fallen over. “Only the north wall had disappeared down into the darkness,” says Langley.
The ark’s success prompted Bernal to report from Canada that the construction of an ice vessel “will not offer any particular difficulties”. The ships were considered for use not only in the north Atlantic, but even in the warm waters of the Mediterranean Sea and Pacific Ocean. Blueprints were drawn up for the basic bergship and a series of variants.
Langley says that in the 1980s she was shown two drawers full of these papers at the National Research Council’s archive in a suburb of Ottawa. One drawing was labelled “Habbakuk Mark 3-D”, and showed a colossal ice trimaran. But the records seem to have been lost. “Now if I contact them, they say they don’t know what I’m talking about,” she says.
When the British government actually put in an order for 11 full-size vessels, Mackenzie was horrified. As an engineer, he understood that scaling up from 20 metres to 600 would bring immense complications. For a start, the model had only involved plain ice. “It was just to see if a refrigeration unit could sustain the ice structure,” says Langley. The full-size carrier would need a hull of much stronger stuff.
Pleasingly mad
As it turned out, even pykrete would have been inadequate. At temperatures above -15 °C, pykrete slowly deforms. Even with enough refrigeration plants to keep it cold, it still wouldn’t have been able to support a 600-metre ship. Steel reinforcement would be needed too. Probably a lot of it. And, of course, a vast quantity of wood pulp would be needed, the equivalent of a small forest for each carrier. Perutz later said he had come to realise that the construction and navigation of a bergship might prove “as difficult as a voyage to the moon”.
In any case, this pleasingly mad idea was soon made redundant by somewhat more mundane developments, including longer-range bombers and new airbases in Iceland. In December 1943, project Habbakuk was dropped.
Since the war, a few engineers have toyed with the idea of using pykrete for other purposes – such as protecting Arctic oil rigs from stormy seas, or making a quay in Oslo harbour. Although nothing has come of it so far, Langley is hopeful that pykrete will one day make more than an icy bath toy. “It still has amazing possibilities, but it has not found its niche yet,” she says. “We just have to get the right people interested.” In the spirit of Pyke’s original plan, perhaps some aspiring seasteaders will see the material’s potential, and build themselves a floating city of ice.
