Pykrete
Encyclopedia
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
made of approximately 14 percent sawdust
Sawdust
Sawdust is a by-product of cutting lumber with a saw, composed of fine particles of wood. It can present a hazard in manufacturing industries, especially in terms of its flammability....
or some other form of wood pulp
Wood pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
(such as paper) and 86 percent ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
by weight. Its use was proposed during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
by Geoffrey Pyke
Geoffrey Pyke
Geoffrey Nathaniel Joseph Pyke was an English journalist, educationalist, and later an inventor whose clever, but unorthodox, ideas could be difficult to implement...
to the British Royal Navy as a candidate material for making a huge, unsinkable aircraft carrier
Project Habakkuk
Project Habakkuk or Habbakuk was a plan by the British in World War II to construct an aircraft carrier out of pykrete , for use against German U-boats in the mid-Atlantic, which were beyond the flight range of land-based planes at that time.The idea came from Geoffrey Pyke who worked for Combined...
. Pykrete has some interesting properties, notably its relatively slow melting rate (because of low thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
), and its vastly improved strength
Strength of materials
In materials science, the strength of a material is its ability to withstand an applied stress without failure. The applied stress may be tensile, compressive, or shear. Strength of materials is a subject which deals with loads, deformations and the forces acting on a material. A load applied to a...
and toughness
Toughness
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing; Material toughness is defined as the amount of energy per volume that a material can absorb before rupturing...
over unmodified (crystalline) ice; it is closer in form to concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
.
Pykrete is slightly more difficult to form than concrete, as it expands during the freezing process. However, it can be repaired and maintained using seawater. The mixture can be moulded into any shape and frozen, and it will be extremely tough and durable, as long as it is kept at or below freezing.
History
Geoffrey PykeGeoffrey Pyke
Geoffrey Nathaniel Joseph Pyke was an English journalist, educationalist, and later an inventor whose clever, but unorthodox, ideas could be difficult to implement...
managed to convince Lord Mountbatten
Louis Mountbatten, 1st Earl Mountbatten of Burma
Admiral of the Fleet Louis Francis Albert Victor Nicholas George Mountbatten, 1st Earl Mountbatten of Burma, KG, GCB, OM, GCSI, GCIE, GCVO, DSO, PC, FRS , was a British statesman and naval officer, and an uncle of Prince Philip, Duke of Edinburgh...
of the worth of his project (actually prior to the invention of pykrete) some time around 1942, and trials were made in two locations in Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. The idea for a ship made of ice impressed the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada enough that a 60 feet (18.3 m)-long, 1,000-ton ship was built in one month on Patricia Lake
Patricia Lake (Alberta)
Patricia Lake is a lake in Jasper National Park, Alberta, Canada, near the town of Jasper.Pyramid Lake is connected by hiking trails to the town of Jasper, and other tourist sites such as Pyramid Lake and Pyramid Mountain.- Project Habbakuk :...
in the Canadian Rockies
Canadian Rockies
The Canadian Rockies comprise the Canadian segment of the North American Rocky Mountains range. They are the eastern part of the Canadian Cordillera, extending from the Interior Plains of Alberta to the Rocky Mountain Trench of British Columbia. The southern end borders Idaho and Montana of the USA...
. It was, however, constructed using plain ice (from the lake), before pykrete was considered. It took slightly more than an entire summer to melt.
Plain ice proved to be insufficiently strong. Pyke
Geoffrey Pyke
Geoffrey Nathaniel Joseph Pyke was an English journalist, educationalist, and later an inventor whose clever, but unorthodox, ideas could be difficult to implement...
learned from a report by Herman Mark
Herman Francis Mark
Herman Francis Mark was an Austrian-American chemist regarded for his contributions to the development of polymer science. Mark's x-ray diffraction work on the molecular structure of fibers provided important evidence for the macromolecular theory of polymer structure...
and his assistant that ice made from water mixed with wood fibres formed a strong solid mass— much stronger than pure water ice. Max Perutz
Max Perutz
Max Ferdinand Perutz, OM, CH, CBE, FRS was an Austrian-born British molecular biologist, who shared the 1962 Nobel Prize for Chemistry with John Kendrew, for their studies of the structures of hemoglobin and globular proteins...
later recalled:
Perutz would later learn that Project Habakkuk was the plan to build an enormous aircraft carrier, actually more of a floating island
Floating island
A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from a few inches to several feet. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less commonly as a man-made phenomenon...
than a ship in the traditional sense. The experiments of Perutz and his collaborators in Smithfield Meat Market
Smithfield, London
Smithfield is an area of the City of London, in the ward of Farringdon Without. It is located in the north-west part of the City, and is mostly known for its centuries-old meat market, today the last surviving historical wholesale market in Central London...
in the City of London
City of London
The City of London is a small area within Greater London, England. It is the historic core of London around which the modern conurbation grew and has held city status since time immemorial. The City’s boundaries have remained almost unchanged since the Middle Ages, and it is now only a tiny part of...
took place in great secrecy behind a screen of animal carcasses. The tests confirmed that pykrete is much stronger than pure ice and does not shatter, but also that it sags under its own weight at temperatures higher than -15 C.
Mountbatten’s reaction to the breakthrough is recorded by Pyke's biographer David Lampe:
Another tale is that at the Quebec Conference
Quebec Conference, 1943
The First Quebec Conference was a highly secret military conference held during World War II between the British, Canadian and United States governments. The conference was held in Quebec City, August 17, 1943 – August 24, 1943. It took place at the Citadelle and at the Château Frontenac. The...
of 1943 Mountbatten brought a block of pykrete along to demonstrate its potential to the entourage of admirals and generals who had come along with Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
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
Ernest King
Fleet Admiral Ernest Joseph King was Commander in Chief, United States Fleet and Chief of Naval Operations during World War II. As COMINCH, he directed the United States Navy's operations, planning, and administration and was a member of the Joint Chiefs of Staff. He was the U.S...
and ending up in the wall. According to Perutz's own account, however, the incident of a ricochetting bullet hitting an Admiral actually happened much earlier in London and the gun was fired by someone on the project—not Mountbatten.
Despite these tests, the main Project Habakkuk was never put into action because of limitations in funds and the belief that the tides of the war were beginning to turn in favour of the Allies using more conventional methods.
According to the memoirs of British General Ismay
Hastings Ismay, 1st Baron Ismay
General Hastings Lionel "Pug" Ismay, 1st Baron Ismay, KG, GCB, CH, DSO, PC was a British Indian Army officer and diplomat, remembered primarily for his role as Winston Churchill's chief military assistant during the Second World War and his service as the first Secretary General of NATO from 1952...
:
Since WWII pykrete has remained a scientific curiosity, unexploited by research or construction of any significance. In 1985, pykrete was considered for a quay in Oslo
Oslo
Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...
harbour.
New concepts for pykrete however crop up occasionally among architects, engineers and futurists, usually regarding its potential for mammoth offshore construction or its improvement by applying super-strong materials such as synthetic composites
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
or Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
.
Durability
The durability of pykrete is up for debate. Perutz has estimated a value of around 1100 psi (7.6 MPa).A September 1943 proposal for making smaller pykrete vessels included the following table of characteristics:
| Mechanical properties | Ice Ice Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions... |
Concrete Concrete Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word... |
Pykrete |
|---|---|---|---|
| 3.447 | 17.240 | 7.584 | |
| Tensile strength Tensile strength Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract... [MPa Pascal (unit) The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre... ] |
1.103 | 1.724 | 4.826 |
| Density Density The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight... [kg/m³] |
910 | 2500 | 980 |
In the media
In 2009, the Discovery ChannelDiscovery Channel
Discovery Channel is an American satellite and cable specialty channel , founded by John Hendricks and distributed by Discovery Communications. It is a publicly traded company run by CEO David Zaslav...
program MythBusters
MythBusters
MythBusters is a science entertainment TV program created and produced by Beyond Television Productions for the Discovery Channel. The series is screened by numerous international broadcasters, including Discovery Channel Australia, Discovery Channel Latin America, Discovery Channel Canada, Quest...
episode 115 tested the properties of pykrete and the myths behind it. First, the program's hosts, Adam Savage
Adam Savage
Adam Whitney Savage is an American industrial design and special effects designer/fabricator, actor, educator, and co-host of the Discovery Channel television series MythBusters. His model work has appeared in major films, including Star Wars: Episode II - Attack of the Clones and The Matrix...
and Jamie Hyneman
Jamie Hyneman
James Franklin "Jamie" Hyneman is an American special effects expert, best known for being the co-host of the television series MythBusters. He is also the owner of M5 Industries, the special effects workshop where MythBusters is filmed...
compared the mechanical properties of common ice, pykrete and a new material specially created for the show, dubbed "super pykrete", using newspapers instead of woodpulp. Both versions of pykrete indeed proved to be much stronger than the chunk of ice, withstanding hundreds of pounds of weight. The super pykrete was much stronger than the original version.
The MythBusters then built a full-size boat out of the super pykrete, naming it Yesterday's News, and subjected it to real-world conditions. Though the boat managed to float and stay intact at speeds of up to 23 miles per hour (37 km/h), it quickly began to spring leaks as the boat slowly melted. After twenty minutes the boat was deteriorating, and the experiment was ended. The boat lasted another ten minutes while being piloted back to shore. Though the boat worked, it was noted that it would be highly impractical for the original myth, which claimed that an entire aircraft carrier could be built out of pykrete. Their conclusion was "Plausible, but ludicrous". However, the test was done at or slightly above freezing temperatures, and not with refrigeration units keeping the pykrete cold, as the original plans called for.