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Did you ever hear of an aircraft carrier, made from ice?
During World War II, there were a lot of technologies proposed that seem outlandish by today’s standards.
One of them was by a British inventor named Geoffrey Pike, who wanted to build an aircraft carrier that was mostly composed of ice. He wanted to build it using Pykrete, a material that is 86 percent ice and 14 percent sawdust.
You might be thinking that the only place to build a carrier made of ice would be in Arctic regions. There might not be a reason to defend this cold area, but this ice carrier is actually made for warmer waters, too. Yes, it would begin to melt, but it can be repaired while at sea using the waters around it. Don’t ask me how it is supposed to do that.
If Pyke’s HMS Habbakuk was ever constructed, it would have been one of the largest crafts at sea. It would be 2,000 feet long, 300 feet wide, and 200 feet tall. It could hold 200 fighter planes or 100 bombers, with a crew of about 3,700. It would have been pretty impressive, but only a 60-foot prototype was made, and didn’t go off very well.
Initial concept
Geoffrey Pyke was an old friend of J.D. Bernal, and had originally been recommended to Lord Mountbatten, Chief of Combined Operations, by the Cabinet minister Leopold Amery. Pyke worked at Combined Operations Headquarters (COHQ), alongside Bernal, and was regarded as a genius by Mountbatten.
Pyke conceived the idea of Habbakuk while in the US organising the production of M29 Weasels for Project Plough, a scheme to assemble an elite unit for winter operations in Norway, Romania, and the Italian Alps. He had been considering the problem of how to protect seaborne landings and Atlantic convoys out of reach of aircraft cover. The problem was that steel and aluminium were in short supply and required for other purposes. Pyke realized that the answer was ice, which could be manufactured for only 1% of the energy needed to make an equivalent mass of steel. He proposed that an iceberg, natural or artificial, be levelled to provide a runway and hollowed out to shelter aircraft. From New York, Pyke sent the proposal he had composed on Habbakuk via diplomatic bag to COHQ with a label forbidding anyone apart from Mountbatten from opening the package. Mountbatten in turn passed Pyke's proposal on to Churchill, who was enthusiastic about it. Pyke was not the first to suggest a floating mid-ocean stopping point for aircraft, nor even the first to suggest that such a floating island could be made of ice: German scientist Dr. Gerke of Waldenberg proposed the idea and carried out some preliminary experiments in Lake Zurich in 1930. The idea was a recurring one: in 1940 an idea for an ice island was circulated round The Admiralty but was treated as a joke by officers, including Nevil Shute, who circulated a memorandum that gathered ever more caustic comments. The document had to be retrieved just before it reached the Sea Lord's inbox.
Code name and spelling
The project's code name seems to have been consistently (mis)spelled Habbakuk in the Admiralty and Government documents at the time. This may in fact have been Pyke's own error, as at least one early document apparently written by him (though unsigned) spells it that way. (However, post-war publications by people concerned with the project [e.g., Perutz and Goodeve] all restore the proper [one 'B' and three 'K's] spelling.) The name is a biblical
reference to the project's ambitious goal: "...be utterly amazed, for I am going to do something in your days that you would not believe, even if you were told." (Habakkuk 1:5, NIV)
David Lampe, in his book, Pyke, the Unknown Genius, states that the name was derived from Voltaire's Candide and was misspelt by his Canadian secretary. However, the word does not actually appear in that text, so this is probably inaccurate.
In early 1942 Pyke and Bernal called in Max Perutz to determine whether an ice floe large enough to withstand Atlantic conditions could be built up fast enough. He 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, except for the invention of pykrete, a mixture of water and woodpulp which frozen together was stronger than plain ice, was slower melting, and of course would not sink. It has been suggested that Pyke was inspired by Inuit sleds reinforced with moss. This is probably apocryphal, as the material was originally described in a paper by Mark and Hohenstein in Brooklyn, NY. 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 which protected its interior from further melting. However, Perutz found a problem: ice slowly flows, in what is known as plastic flow, and his tests showed that a pykrete ship would slowly sag unless it was cooled to −16 °C (3 °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.
Experiments on the viability of pykrete and the optimum composition of it were conducted by Perutz in a secret location underneath Smithfield Meat Market in the City of London. The research took place in a refrigerated meat locker behind a protective screen of frozen animal carcasses.
Scale model
The decision was made to build a large scale model at Jasper National Park in Canada to examine insulation and refrigeration techniques, and to see how it would stand up to artillery and explosives. At Lake Louise, Alberta, large ice blocks were constructed, and a small prototype was constructed at Patricia Lake, Alberta, measuring only 60 by 30 feet (18 by 9 m), weighing in at 1,000 tons and kept frozen by a one-horsepower motor. The work was done by conscientious objectors who did alternative service of various kinds instead of military service. They were never told what they were building. Bernal informed COHQ that the Canadians were building a 1,000 ton model, and that it was expected to take 8 men 14 days to build it. The Chief of Combined Operations (CCO) responded that Churchill had invited the Chiefs of Staff Committee to arrange for an order to be placed for one complete ship at once with the highest priority, with further ships to be ordered immediately if it appeared the scheme was certain of success.
The Canadians were confident about constructing a vessel for 1944. The necessary materials were available to them in the form of 300,000 tons of wood pulp, 25,000 tons of fibreboard insulation, 35,000 tons of timber and 10,000 tons of steel. The cost was estimated at £700,000. Meanwhile, Perutz had determined via his experiments at Smithfield Market that the optimum structural properties were given by a mixture of 14% wood pulp and 86% water. He wrote to Pyke in early April 1943 and pointed out that if certain tests were not completed in May, there would be no chance of delivering a completed ship in 1944.
By May the problem of plastic flow had become serious and it was obvious that more steel reinforcement would be needed as well as a more effective insulating skin around the vessel's hull. This caused the cost estimate to increase to £2.5 million. In addition, the Canadians had decided that it was impractical to attempt the project "this coming season", and Bernal and Pyke were forced to conclude that no Habbakuk vessel would be ready in 1944. Pyke was excluded from the planning for Habbakuk in an effort to secure American participation, a decision which Bernal supported. Pyke's earlier disagreements with American personnel on Project Plough, which ultimately caused his removal from that project, were the main factor in this decision. In the early summer of 1943, naval architects and engineers continued to work on Habbakuk with Bernal and Perutz. The requirements for the vessel became more demanding: it had to have a range of 7,000 miles (11,000 km) and be able to withstand the largest waves recorded, while the Admiralty wanted it to be torpedo-proof, which meant that the hull had to be at least 40 ft (12 m) thick. The Fleet Air Arm decided that heavy bombers should be able to take off from it, which meant that the deck had to be 2,000 ft (610 m) long. Steering also raised problems; it was initially projected that the ship be steered by varying the speed of the motors on either side, but the Royal Navy decided that a rudder was essential. However, the problem of mounting and controlling a rudder over 100 ft (30 m) high was never solved.
Variants
Naval architects had produced three alternative versions of Pyke's original concept, which were discussed at a meeting with the Chiefs of Staff in August 1943:
• Habbakuk I (soon discarded) would have been made of wood.
• Habbakuk II was closest to the COHQ model and would be a very large, slow, self-propelled vessel made of pykrete with steel reinforcement.
• Habbakuk III was a smaller, faster version of Habbakuk II.
Air Chief Marshal Portal asked about potential bomb damage to Habbakuk III, and Bernal suggested that a certain amount of deck covering might be ripped off but could be repaired by some kind of flexible matting. It would be more difficult to deal with bomb holes in the centre portion, though the roof over the aircraft hangars would be made proof against 1,000 kg bombs. Bernal considered that no one could say whether the larger Habbakuk II was a practical proposition until a large scale model could be completed and tested in Canada in the spring of 1944. He had no doubts about the suitability of pykrete as a material, but said that constructional and navigational difficulties remained to be overcome. The final design of Habbakuk II gave the bergship (as it was referred to) a displacement of 2.2 million tons. Steam turbogenerators were to supply 33,000 hp (25,000 kW) for 26 electric motors mounted in separate external nacelles (normal, internal ship engines would have generated too much heat for an ice craft). Its armament would have included 40 dual-barrelled 4.5" DP (dual-purpose) turrets and numerous light anti-aircraft guns, and it would have housed an airstrip and up to 150 twin-engined bombers or fighters.
Shooting incident
According to some accounts, at the Quebec Conference of 1943 Lord 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 ricocheted off the block, grazing the trouser leg of Admiral Ernest King and ended up in the wall.
Sir Alan Brooke's diariessupport this account, telling how Mountbatten brought two blocks, one of ice and one of pykrete. After first shooting at the ice, with a warning to beware of splinters, Mountbatten said "I shall fire at the block on the right to show you the difference". Brooke reports, "the bullet rebounded out of the block and buzzed round our legs like an angry bee." The meeting in question was a high-level summit with a US delegation in the Château Frontenac in Quebec.
Max Perutz gives an account of a similar incident in his book, I Wish I Made You Angry Earlier: a demonstration of pykrete was given at Combined Operations Headquarters (COHQ) by a naval officer, Lieutenant Commander Douglas Grant, who was provided by Perutz with rods of ice and pykrete packed with dry ice in thermos flasks and large blocks of ice and pykrete. Grant demonstrated the comparative strength of ice and pykrete by firing bullets into both blocks; the ice shattered, but the bullet rebounded from the pykrete and hit the Chief of the Imperial Staff (Sir Alan Brooke) in the shoulder. Brooke was unhurt.
End of project
Later that year Habbakuk began to lose priority. Mountbatten listed several reasons
• The great demand for steel.
• Permission had been received from Portugal to use airfields in the Azores which facilitated the hunting of U-boats in the Atlantic
• The introduction of long-range fuel tanks that allowed British-based aircraft extra patrol time over the Atlantic
• Increased numbers of escort carriers
In addition, Mountbatten himself had withdrawn from the project. The final Habbakuk Board meeting took place in December 1943 and it was announced that "The large Habbakuk II made of pykrete has been found to be impractical because of the enormous production resources required and technical difficulties involved".
The use of ice had actually been falling out of favour before that, with other ideas for "floating islands" being considered, such as welding Liberty Ships or landing craft together (Project TENTACLE). It took three hot summers to completely melt the prototype constructed in Canada.
Perutz, in his account, writes that he sojourned in Washington D.C. while U.S. Navy engineers evaluated the viability of Habbakuk. He concludes: "The U.S. Navy finally decided that Habakkuk was a false prophet. One reason was the enormous amount of steel needed for the refrigeration plant that was to freeze the pykrete was greater than that needed to build the entire carrier of steel, but the crucial argument was that the rapidly increasing range of land-based aircraft rendered floating islands unnecessary."
Criticism
The Habakkuk design received criticism, notably from Sir Charles Goodeve, Assistant Controller of Research and Development for the Admiralty during World War II. In an article published after the war Goodeve pointed out the large amount of wood pulp that would be required, enough to affect paper production significantly. He also claimed that each ship would require 40,000 tons of cork insulation, thousands of miles of steel tubing for brine circulation, and four power stations, but that for all those resources (some of which could be used to manufacture conventional ships of more effective fighting power) Habakkuk would only be capable of six knots of speed. Much of his article also contained extensive derisive comments about the properties of ice as used for ship construction.
Recent recreations
In the 15 April 2009 episode of Mythbusters, Jamie Hyneman and Adam Savage built a small boat out of a modified formulation of pykrete (using newspaper instead of wood pulp). They successfully piloted the boat in Alaskan waters at a speed of 25 miles per hour (40 km/h). Based on this success, they determined that it is possible to build a boat out of pykrete. They also determined that pykrete lived up to its purported properties of being bulletproof, stronger than ice, and taking longer to melt than ice. However, they expressed doubt that an aircraft carrier made of pykrete could have survived long. In September 2010, the BBC programme Bang Goes The Theory also attempted to recreate a pykrete boat. A hull using 5,000 kg of hemp fibre pykrete was frozen in a cold-store, then launched in Portsmouth harbour for a planned trip across the Solent to Cowes. The hull immediately started to leak, due to holes that had been cut in its rear side to mount an outboard motor.
Did you ever hear of an aircraft carrier, made from ice?
During World War II, there were a lot of technologies proposed that seem outlandish by today’s standards.
One of them was by a British inventor named Geoffrey Pike, who wanted to build an aircraft carrier that was mostly composed of ice. He wanted to build it using Pykrete, a material that is 86 percent ice and 14 percent sawdust.
You might be thinking that the only place to build a carrier made of ice would be in Arctic regions. There might not be a reason to defend this cold area, but this ice carrier is actually made for warmer waters, too. Yes, it would begin to melt, but it can be repaired while at sea using the waters around it. Don’t ask me how it is supposed to do that.
If Pyke’s HMS Habbakuk was ever constructed, it would have been one of the largest crafts at sea. It would be 2,000 feet long, 300 feet wide, and 200 feet tall. It could hold 200 fighter planes or 100 bombers, with a crew of about 3,700. It would have been pretty impressive, but only a 60-foot prototype was made, and didn’t go off very well.
Initial concept
Geoffrey Pyke was an old friend of J.D. Bernal, and had originally been recommended to Lord Mountbatten, Chief of Combined Operations, by the Cabinet minister Leopold Amery. Pyke worked at Combined Operations Headquarters (COHQ), alongside Bernal, and was regarded as a genius by Mountbatten.
Pyke conceived the idea of Habbakuk while in the US organising the production of M29 Weasels for Project Plough, a scheme to assemble an elite unit for winter operations in Norway, Romania, and the Italian Alps. He had been considering the problem of how to protect seaborne landings and Atlantic convoys out of reach of aircraft cover. The problem was that steel and aluminium were in short supply and required for other purposes. Pyke realized that the answer was ice, which could be manufactured for only 1% of the energy needed to make an equivalent mass of steel. He proposed that an iceberg, natural or artificial, be levelled to provide a runway and hollowed out to shelter aircraft. From New York, Pyke sent the proposal he had composed on Habbakuk via diplomatic bag to COHQ with a label forbidding anyone apart from Mountbatten from opening the package. Mountbatten in turn passed Pyke's proposal on to Churchill, who was enthusiastic about it. Pyke was not the first to suggest a floating mid-ocean stopping point for aircraft, nor even the first to suggest that such a floating island could be made of ice: German scientist Dr. Gerke of Waldenberg proposed the idea and carried out some preliminary experiments in Lake Zurich in 1930. The idea was a recurring one: in 1940 an idea for an ice island was circulated round The Admiralty but was treated as a joke by officers, including Nevil Shute, who circulated a memorandum that gathered ever more caustic comments. The document had to be retrieved just before it reached the Sea Lord's inbox.
Code name and spelling
The project's code name seems to have been consistently (mis)spelled Habbakuk in the Admiralty and Government documents at the time. This may in fact have been Pyke's own error, as at least one early document apparently written by him (though unsigned) spells it that way. (However, post-war publications by people concerned with the project [e.g., Perutz and Goodeve] all restore the proper [one 'B' and three 'K's] spelling.) The name is a biblical
reference to the project's ambitious goal: "...be utterly amazed, for I am going to do something in your days that you would not believe, even if you were told." (Habakkuk 1:5, NIV)
David Lampe, in his book, Pyke, the Unknown Genius, states that the name was derived from Voltaire's Candide and was misspelt by his Canadian secretary. However, the word does not actually appear in that text, so this is probably inaccurate.
In early 1942 Pyke and Bernal called in Max Perutz to determine whether an ice floe large enough to withstand Atlantic conditions could be built up fast enough. He 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, except for the invention of pykrete, a mixture of water and woodpulp which frozen together was stronger than plain ice, was slower melting, and of course would not sink. It has been suggested that Pyke was inspired by Inuit sleds reinforced with moss. This is probably apocryphal, as the material was originally described in a paper by Mark and Hohenstein in Brooklyn, NY. 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 which protected its interior from further melting. However, Perutz found a problem: ice slowly flows, in what is known as plastic flow, and his tests showed that a pykrete ship would slowly sag unless it was cooled to −16 °C (3 °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.
Experiments on the viability of pykrete and the optimum composition of it were conducted by Perutz in a secret location underneath Smithfield Meat Market in the City of London. The research took place in a refrigerated meat locker behind a protective screen of frozen animal carcasses.
Scale model
The decision was made to build a large scale model at Jasper National Park in Canada to examine insulation and refrigeration techniques, and to see how it would stand up to artillery and explosives. At Lake Louise, Alberta, large ice blocks were constructed, and a small prototype was constructed at Patricia Lake, Alberta, measuring only 60 by 30 feet (18 by 9 m), weighing in at 1,000 tons and kept frozen by a one-horsepower motor. The work was done by conscientious objectors who did alternative service of various kinds instead of military service. They were never told what they were building. Bernal informed COHQ that the Canadians were building a 1,000 ton model, and that it was expected to take 8 men 14 days to build it. The Chief of Combined Operations (CCO) responded that Churchill had invited the Chiefs of Staff Committee to arrange for an order to be placed for one complete ship at once with the highest priority, with further ships to be ordered immediately if it appeared the scheme was certain of success.
The Canadians were confident about constructing a vessel for 1944. The necessary materials were available to them in the form of 300,000 tons of wood pulp, 25,000 tons of fibreboard insulation, 35,000 tons of timber and 10,000 tons of steel. The cost was estimated at £700,000. Meanwhile, Perutz had determined via his experiments at Smithfield Market that the optimum structural properties were given by a mixture of 14% wood pulp and 86% water. He wrote to Pyke in early April 1943 and pointed out that if certain tests were not completed in May, there would be no chance of delivering a completed ship in 1944.
By May the problem of plastic flow had become serious and it was obvious that more steel reinforcement would be needed as well as a more effective insulating skin around the vessel's hull. This caused the cost estimate to increase to £2.5 million. In addition, the Canadians had decided that it was impractical to attempt the project "this coming season", and Bernal and Pyke were forced to conclude that no Habbakuk vessel would be ready in 1944. Pyke was excluded from the planning for Habbakuk in an effort to secure American participation, a decision which Bernal supported. Pyke's earlier disagreements with American personnel on Project Plough, which ultimately caused his removal from that project, were the main factor in this decision. In the early summer of 1943, naval architects and engineers continued to work on Habbakuk with Bernal and Perutz. The requirements for the vessel became more demanding: it had to have a range of 7,000 miles (11,000 km) and be able to withstand the largest waves recorded, while the Admiralty wanted it to be torpedo-proof, which meant that the hull had to be at least 40 ft (12 m) thick. The Fleet Air Arm decided that heavy bombers should be able to take off from it, which meant that the deck had to be 2,000 ft (610 m) long. Steering also raised problems; it was initially projected that the ship be steered by varying the speed of the motors on either side, but the Royal Navy decided that a rudder was essential. However, the problem of mounting and controlling a rudder over 100 ft (30 m) high was never solved.
Variants
Naval architects had produced three alternative versions of Pyke's original concept, which were discussed at a meeting with the Chiefs of Staff in August 1943:
• Habbakuk I (soon discarded) would have been made of wood.
• Habbakuk II was closest to the COHQ model and would be a very large, slow, self-propelled vessel made of pykrete with steel reinforcement.
• Habbakuk III was a smaller, faster version of Habbakuk II.
Air Chief Marshal Portal asked about potential bomb damage to Habbakuk III, and Bernal suggested that a certain amount of deck covering might be ripped off but could be repaired by some kind of flexible matting. It would be more difficult to deal with bomb holes in the centre portion, though the roof over the aircraft hangars would be made proof against 1,000 kg bombs. Bernal considered that no one could say whether the larger Habbakuk II was a practical proposition until a large scale model could be completed and tested in Canada in the spring of 1944. He had no doubts about the suitability of pykrete as a material, but said that constructional and navigational difficulties remained to be overcome. The final design of Habbakuk II gave the bergship (as it was referred to) a displacement of 2.2 million tons. Steam turbogenerators were to supply 33,000 hp (25,000 kW) for 26 electric motors mounted in separate external nacelles (normal, internal ship engines would have generated too much heat for an ice craft). Its armament would have included 40 dual-barrelled 4.5" DP (dual-purpose) turrets and numerous light anti-aircraft guns, and it would have housed an airstrip and up to 150 twin-engined bombers or fighters.
Shooting incident
According to some accounts, at the Quebec Conference of 1943 Lord 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 ricocheted off the block, grazing the trouser leg of Admiral Ernest King and ended up in the wall.
Sir Alan Brooke's diariessupport this account, telling how Mountbatten brought two blocks, one of ice and one of pykrete. After first shooting at the ice, with a warning to beware of splinters, Mountbatten said "I shall fire at the block on the right to show you the difference". Brooke reports, "the bullet rebounded out of the block and buzzed round our legs like an angry bee." The meeting in question was a high-level summit with a US delegation in the Château Frontenac in Quebec.
Max Perutz gives an account of a similar incident in his book, I Wish I Made You Angry Earlier: a demonstration of pykrete was given at Combined Operations Headquarters (COHQ) by a naval officer, Lieutenant Commander Douglas Grant, who was provided by Perutz with rods of ice and pykrete packed with dry ice in thermos flasks and large blocks of ice and pykrete. Grant demonstrated the comparative strength of ice and pykrete by firing bullets into both blocks; the ice shattered, but the bullet rebounded from the pykrete and hit the Chief of the Imperial Staff (Sir Alan Brooke) in the shoulder. Brooke was unhurt.
End of project
Later that year Habbakuk began to lose priority. Mountbatten listed several reasons
• The great demand for steel.
• Permission had been received from Portugal to use airfields in the Azores which facilitated the hunting of U-boats in the Atlantic
• The introduction of long-range fuel tanks that allowed British-based aircraft extra patrol time over the Atlantic
• Increased numbers of escort carriers
In addition, Mountbatten himself had withdrawn from the project. The final Habbakuk Board meeting took place in December 1943 and it was announced that "The large Habbakuk II made of pykrete has been found to be impractical because of the enormous production resources required and technical difficulties involved".
The use of ice had actually been falling out of favour before that, with other ideas for "floating islands" being considered, such as welding Liberty Ships or landing craft together (Project TENTACLE). It took three hot summers to completely melt the prototype constructed in Canada.
Perutz, in his account, writes that he sojourned in Washington D.C. while U.S. Navy engineers evaluated the viability of Habbakuk. He concludes: "The U.S. Navy finally decided that Habakkuk was a false prophet. One reason was the enormous amount of steel needed for the refrigeration plant that was to freeze the pykrete was greater than that needed to build the entire carrier of steel, but the crucial argument was that the rapidly increasing range of land-based aircraft rendered floating islands unnecessary."
Criticism
The Habakkuk design received criticism, notably from Sir Charles Goodeve, Assistant Controller of Research and Development for the Admiralty during World War II. In an article published after the war Goodeve pointed out the large amount of wood pulp that would be required, enough to affect paper production significantly. He also claimed that each ship would require 40,000 tons of cork insulation, thousands of miles of steel tubing for brine circulation, and four power stations, but that for all those resources (some of which could be used to manufacture conventional ships of more effective fighting power) Habakkuk would only be capable of six knots of speed. Much of his article also contained extensive derisive comments about the properties of ice as used for ship construction.
Recent recreations
In the 15 April 2009 episode of Mythbusters, Jamie Hyneman and Adam Savage built a small boat out of a modified formulation of pykrete (using newspaper instead of wood pulp). They successfully piloted the boat in Alaskan waters at a speed of 25 miles per hour (40 km/h). Based on this success, they determined that it is possible to build a boat out of pykrete. They also determined that pykrete lived up to its purported properties of being bulletproof, stronger than ice, and taking longer to melt than ice. However, they expressed doubt that an aircraft carrier made of pykrete could have survived long. In September 2010, the BBC programme Bang Goes The Theory also attempted to recreate a pykrete boat. A hull using 5,000 kg of hemp fibre pykrete was frozen in a cold-store, then launched in Portsmouth harbour for a planned trip across the Solent to Cowes. The hull immediately started to leak, due to holes that had been cut in its rear side to mount an outboard motor.
