History of nuclear weapons
A nuclear weapon is a weapon of enormous destructive potential, deriving its energy from nuclear fission or nuclear fusion reactions.
These weapons were initially developed in the United States during World War II in what was called the Manhattan Project. The Soviet Union followed suit shortly thereafter with their own atomic bomb project. During the Cold War, these two countries each acquired nuclear weapons arsenals numbering in the thousands, placing many of them onto rockets which could hit targets anywhere in the world. Currently there are at least seven countries with functional nuclear weapons (see List of countries with nuclear weapons). A considerable amount of international negotiating has focused on the threat of nuclear warfare and the proliferation of nuclear weapons to new nations or groups.
This article discusses the historical development of nuclear weapons, from the scientific breakthroughs in the 1930s which led to their development, through the nuclear arms race and nuclear testing of the Cold War, and finally with the question of proliferation and terrorism in the early 21st century. For more details about the effects and design of nuclear weapons, see the articles nuclear weapon and nuclear weapon design.
Prelude: Physics and politics in the 1930s
- See the main article at History of physics.
In the first decades of the twentieth century, physics was revolutionized with developments in the understanding of the nature of atoms. In 1898, Madame Curie and her husband Pierre had discovered that present in pitchblende, an ore of uranium, was a substance which emitted large amount of radioactivity, which they named radium. This raised the hopes of both scientists and lay people that the elements around us could contain tremendous amounts of unseen energy, waiting to be tapped.
Experiments by Ernest Rutherford in 1911 indicated that the vast majority of an atom's mass was contained in a very small nucleus at its core, made up of protons, surrounded by a web of whirring electrons. In 1932, James Chadwick discovered that the nucleus contained another fundamental particle, the neutron, and in the same year John Cockcroft and Ernest Walton "split the atom" for the first time, the first occasion on which an atomic nucleus of one element had been successfully changed to a different nucleus by artificial means.
Great changes were also mounting on the political scene as well. Adolf Hitler was appointed chancellor of Germany in January 1933, and within only three months had asserted dictatorial control over the country. As part of the anti-semitic ideology of Nazism, all Jewish civil servants were fired from their posts, including university professors, many of which fled to Great Britain and the United States, if they could find jobs.
In 1934, French physicists Irène and Frédéric Joliot-Curie discovered that artificial radioactivity could be induced in stable elements by bombarding them with alpha particles, and in the same year Italian physicist Enrico Fermi reported similar results when bombarding uranium with neutrons.
In Germany, Hitler passed the first of the Nuremberg laws in 1935, officially stating that Jews were no longer citizens of the German state and preventing from marrying non-Jews. After a failed coup by Francisco Franco's Nationalists in 1936, the Spanish Civil War broke out, backed by Hitler and Italian Fascist dictator Benito Mussolini.
In 1938, Germans Otto Hahn and Fritz Strassman released the results of their finding proving that what Fermi had witnessed in 1934 was no less than the bursting of the uranium nucleus: nuclear fission. Immediately afterwards, Lise Meitner and Otto Robert Frisch described the theoretical mechanisms of fission and revealed that large amounts of binding energy was released in the process. Hungarian Leo Szilard confirmed with his own experiments that along with energy, neutrons were given off in the reaction as well, creating the possibility of a nuclear chain reaction, whereby each fission created two or more other fissions, exponentially releasing energy.
As the Nazi army marched into first Czechoslovakia in 1938, and then Poland in 1939, officially beginning World War II, many of Europe's top physicists had already began to flee from the emminent conflict approaching. Scientists on both sides of the conflict were well aware of the possibility of utilizing nuclear fission as a weapon, but at the time no one was quite sure how it could be done. In the early years of the first world war, physicists abruptly stopped publishing on the topic of fission, an act of self-censorship to keep the opposing side from gaining any advantages.
From Los Alamos to Hiroshima
- See the main article at Manhattan Project.
By the beginning of World War II, there was concern amongst scientists in the Allied nations that Nazi Germany might have their own project to develop fission-based weapons. Organized research first began in Britain as part of the "TUBE ALLOYS" project, and in the United States a small amount of funding was given for research into uranium weapons starting in 1939. At the urging of British scientists, though, who had made crucial calculations indicating that a fission weapon could be completed within only a few years, by 1941 the project had been wrested into better bureaucratic hands, and in 1942 came under the auspices of General Leslie Groves as the Manhattan Project. Scientifically led by the eccentric American physicist Robert Oppenheimer, the project brought together the top scientific minds of the day (many exiles from Europe) with the production power of American industry for the goal of producing fission-based explosive devices before Germany could. Great Britain and the U.S. agreed to pool their resources and information for the project, but the other Allied power—the Soviet Union under Joseph Stalin—was not informed.
A massive industrial and scientific undertaking, the Manhattan Project involved many of the world's great physicists in the scientific and development aspects. The United States made an unprecedented investment into wartime research for the project, which was spread across over 30 sites in the U.S. and Canada. Scientific knowledge was centralized at a secret laboratory known as Los Alamos, previously a small ranch school near Santa Fe, New Mexico.
Uranium appears in nature primarily in two isotopes: uranium-238 and uranium-235. When the nucleus of uranium-235 absorbs a neutron, it undergoes nuclear fission, splitting into two "fission products" and releasing energy and 2.5 neutrons on average. Uranium-238, on the other hand, absorbs neutrons and does not fission, effectively putting a stop to any ongoing fission reaction. It was discovered that an atomic bomb based on uranium would need to be made of almost completely pure uranium-235 (at least 80% pure), or else the presence of uranium-238 would quickly derail the nuclear chain reaction. The team of scientists working on the Manhattan Project immediately realized that one of the largest problems they would have to solve was how to remove uranium-235 from natural uranium, which was composed of over 99% uranium-238. Two methods were developed during the wartime project, both of which took advantage of the fact that uranium-238 weighs microscopically more than uranium-235: electromagnetic separation and gaseous diffusion. Another secret site was erected at rural Oak Ridge, Tennessee, for the large-scale production and purification of the rare isotope. It was a massive investment: at the time, it was the largest factory under one roof, and employed thousands of employees at its peak, most of whom had no idea what they were working on.
Though uranium-238 cannot be used inside an atomic bomb, when it absorbs a neutron it transforms first into an unstable element, uranium-239, and then decays into neptunium-239 and finally the relatively stable plutonium-239, an element which does not exist in nature. Plutonium is also fissile and can be used to create a fission reaction, and after Enrico Fermi achieved the world's first sustained and controlled nuclear chain reaction in the creation of the first "atomic pile"—a primitive nuclear reactor—in a basement at the University of Chicago, massive reactors were secretly created at what is now known as Hanford Site in the state of Washington, using the Columbia River as cooling water, to transform uranium-238 into plutonium for a bomb.
For a fission weapon to operate, there must be a critical mass—the amount needed for a self-sustaining nuclear chain reaction—of fissile material bombarded with neutrons at any one time. The simplest form of nuclear weapon would be a "gun assembly" weapon, where on sub-critical mass of fissile material (such as uranium-235) would be shot at another sub-critical mass of fissile material. The result would be a critical or super-critical mass which, when bombarded with neutrons, would undergo fission at a rapid rate and create the desired explosion.
But it was soon discovered that plutonium cannot be used in a "gun assembly," as it has too high a level of background neutron radiation. If plutonium were used in a "gun assembly," the chain reaction would start in the split seconds before the critical mass was assembled, blowing the weapon apart before it would have any great effect (this is known as a fizzle). After some despair, Los Alamos scientists discovered another approach: using chemical explosives to implode a sub-critical sphere of plutonium, which would increase its density and make it into a critical mass. The difficulties with implosion were in the problem of making the chemical explosives deliver a perfectly uniform shock-wave upon the plutonium sphere—if it was off by only a little, the weapon would fizzle (which would be expensive, messy, and not a very effective military device).
After D-Day, General Groves had ordered a team of scientists—Project ALSOS—to follow Eastward-moving victorious Allied troops into Europe in order to assess the status of the German nuclear program (and to prevent the Westward-moving Russians from gaining any materials or scientific manpower). It was concluded that while Nazi Germany had also had an atomic bomb program, headed by Werner Heisenberg the government had not made a significant investment in the project, and had been nowhere near success.
By the unconditional surrender of Germany on May 8, 1945, the Manhattan Project was still months away from a working weapon. That April, after the death of American president Roosevelt, former vice-president Harry S. Truman was told about the secret wartime project for the first time.
Because of the difficulties in making a working plutonium bomb, it was decided that there should be on test of the weapon, and Truman wanted to know for sure if it would work before his meeting with Joseph Stalin at an upcoming conference on the future of postwar Europe. On July 16, 1945, in the desert north of Alamogodo, New Mexico, the first nuclear test took place, code-named "Trinity." The test released the equivalent of 19 thousand tons (kilotons) of TNT, far mightier than any weapon ever used before.
The news of the test's success was rushed to Truman. At the Potsdam Conference, held near Berlin, Truman told Stalin in confidence that he had a "powerful new weapon," but was shocked at Stalin's apparent disinterest. The truth was that Stalin already knew: the Soviet Union had been informed of the American and British weapons research from the beginning through volunteer spies amongst the Los Alamos scientists, most notably Klaus Fuchs, Theodore Hall, and David Greenglass. Their information was being processed under the guidance of Russian physicist Igor Kurchatov, though the country was still too involved in the fighting of World War II to begin an all-out effort.
After hearing arguments from scientists and military officers over the possible uses of the weapons against Japan (though some recommended using them as "demonstrations" in non-populated areas, most recommended using them against "built up" targets, a euphamistic term for populated cities), Truman ordered the use of the weapons on Japanese cities, hoping it would send a strong message which would end in the capitulation of the Japanese leadership and avoid a lengthy invasion of the island. On August 6, 1945, a uranium-based weapon, "Little Boy", was let loose on the Japanese city of Hiroshima. Three days later, a plutonium-based weapon, "Fat Man", was dropped onto the city of Nagasaki. Hundreds of thousands of Japanese, most of them civilians, were killed outright by the intense fireball, radiation, and shock-wave of the atomic bombs. Many tens of thousands would die later of radiation sickness and related cancers. Truman promised a "rain of ruin" of Japan did not surrender immediately, threatening to eliminate Japanese cities, one by one; Japan surrendered on August 15.
The weapons had been developed, and their power had been demonstrated to the world. The United States held a monopoly on nuclear weapons, but nobody thought this could last forever—the principles were based in fundamental research, which could be duplicated almost anywhere. The atomic age had begun.
See also: Norwegian heavy water sabotage, Atomic bombings of Hiroshima and Nagasaki
Red bomb on the horizon
- See the main article at Soviet atomic bomb project.
The Soviet Union may not have been invited to share in the new weapons developed by the United States and the other Allies, but they were not to be left out of the nuclear club for long. All during the war, information had been pouring in from a number of volunteer spies involved with the Manhattan Project, and the Soviet nuclear physicist Igor Kurchatov was carefully watching the Allied weapons development. As such, it came as no surprise to Stalin when Truman had informed him at the Potsdam conference that he had a "powerful new weapon." Truman was shocked at Stalin's apparent disinterest.
Those in the U.S. project were all volunteers and none were Russians. One of the most valuable, Klaus Fuchs, was a German émigré theoretical physicist who had been a part in the early British nuclear efforts and had been part of the UK mission to Los Alamos during the war. Fuchs had been intimately involved in the development of the implosion weapon, and passed on detailed cross-sections of the "Trinity" device to his Soviet contacts. Other Los Alamos spies—none of whom knew each other—included Theodore Hall and David Greenglass. The information was kept but not acted upon, as Russia was still too busy fighting the war in Europe to devote resources to this new project.
Almost immediately after World War II, relations between the United States and the Soviet Union began to sour. The United States had shown itself to have a weapon of great military strength, and was declining to share it with other countries (including its wartime allies) or to submit to programs of international control for nuclear weapons. Efforts were made to attempt to secure the American monopoly on nuclear weapons, including the buying up of known worldwide uranium reserves where possible. Shortly after the bombings of Hiroshima and Nagasaki, however, the United States released the Smyth Report, a sanitized summary of their wartime efforts which focused on their production facilities and scale of investment.
Under the watch of former secret police boss Lavrenty Beria, the Soviet atomic program gathered steam. Aided by their volunteer espionage activities in the United States during and after the war, as well as the production blueprint provided by the Smyth Report, the Soviet program was a deliberately conservative attempt to mimic the Manhattan Project, to the point of rejecting more efficient designs for weapons if they were not similar to the American models. In Beria's logic, the U.S. model had worked, and that was all that mattered. On August 29, 1949, the Soviet Union detonated its first atomic device, known in the West as "Joe-1", years ahead of Western predictions. Thus began officially the nuclear arms race, shortly thereafter President Truman announced a decision to begin a crash program to develop an even more powerful weapon: the hydrogen bomb (see next section).
The hydrogen bomb
The notion of using a fission weapon to ignite a process of nuclear fusion can be dated back to 1942. At the first major theoretical conference on the development of an atomic bomb hosted by J. Robert Oppenheimer at the University of California, Berkeley, participant Edward Teller directed the majority of the discussion towards Enrico Fermi's idea of a "Super" bomb. It was thought at the time that a fission weapon would be quite simple to develop and that perhaps work on a hydrogen bomb would be possible to complete before the end of the second World War. However in reality the problem of a "regular" atomic bomb was large enough to preoccupy the scientists for the next few years, much less the more speculative "Super." Only Teller continued working on the project -- against the will of project leaders Oppenheimer and Hans Bethe.
After the atomic bombings of Japan, many scientists at Los Alamos rebelled against the notion of creating a weapon thousands of times more powerful than the first atomic bombs. For the scientists the question was in part technical -- the weapon design was still quite uncertain and unworkable -- and in part moral -- such a weapon, they argued, could only be used against large civilian populations, and could thus only be used as a weapon of genocide. Many scientists, such as Oppenheimer and Bethe, urged that the United States should not develop such weapons and set an example towards the Soviet Union. Promoters of the weapon, including Teller, Ernest Lawrence, and Luis Alvarez, argued that such a development was inevitable, and to deny such protection to the people of the United States -- especially when the Soviet Union was likely to create such a weapon themselves -- was itself an immoral and unwise act.
In the end, President Truman made the final decision, looking for a proper response to the first Soviet atomic bomb testing in 1949. On January 31, 1950, Truman announced a crash program to develop the hydrogen (fusion) bomb. At this point, however, the exact mechanism was still not known: the "classical" hydrogen bomb, whereby the heat of the fission bomb would be used to ignite the fusion material, seemed highly unworkable. However due to an insight by Los Alamos mathematician Stanislaw Ulam, that the radiation of the fission bomb could first compress the fusion material before igniting it. Teller pushed the notion further, and used the results of the boosted-fission "George" test (a boosted-fission device used a small amount of fusion fuel to boost the yield of a to confirm the fusion of heavy hydrogen elements before preparing for their first true multi-stage), Teller-Ulam hydrogen bomb test. Many scientists initially against the weapon, such as Oppenheimer and Bethe, changed their previous opinions, seeing the development as being unstoppable.
The first fusion bomb was tested by the United States in Operation Ivy on November 1, 1952, on Elugelab Island in the Enewetak (or Eniwetok) Atoll of the Marshall Islands, code-named Mike. It yielded 10.4 megatons of explosive power (equal to 10.4 million tons of TNT), which is over 450 times the power of the bomb that fell on Nagasaki. Mike used liquid deuterium as the fusion fuel and had a 92 point ignition system. It was 20 ft (6 m) high, 6 ft 8 in (2 m) wide, and weighing 140,000 lb (64 t) or 164,000 lb (74 t) including attached refrigeration and measuring equipment. The detonation obliterated Elugelab, leaving an underwater crater 6240 ft (1.9 km) wide and 164 ft (50 m) deep where the island had once been. Truman had initially tried to create a media blackout about the test -- hoping it would not become an issue in the upcoming presidential election -- but on January 7, 1953, Truman announced the development of the hydrogen bomb to the world.
The Soviet Union exploded its first thermonuclear device on August 12, 1953. This created concern within the U.S. government and military, because, unlike "Mike," the Soviet device was a deliverable weapon, which the U.S. did not yet have (however the 1953 Soviet bomb was arguably not a "true" hydrogen bomb in that it was not a multi-stage weapon). By 1954, though, the United States had detonated the "Shrimp" device during the Castle Bravo test, marking the first deployable hydrogen bomb. The device yielded almost twice as much power as was expected, and contaminated island natives and a Japanese fishing boat with deadly nuclear fallout. The Soviet Union detonated its first "true" hydrogen bomb in 1955.
Other thermonuclear devices were exploded by the United Kingdom on May 15, 1957, (Operation Grapple, test off Malden Island), France (February 13, 1960), and the People's Republic of China (October 16, 1964 - a nuclear device, June 14, 1967 - a hydrogen bomb). India claims to have exploded a thermonuclear device in 1998, though some (non-Indian) experts are unsure of whether it was a true hydrogen bomb or simply a boosted-fission device.
Cold War
During the Cold War, more countries joined the "nuclear club." On February 26, 1952, Prime Minister Winston Churchill that the United Kingdom also had an atomic bomb—not a too surprising development, considering how many UK scientists worked at very high levels in the Manhattan Project. By the mid-1960s, both France and the People's Republic of China had also demonstrated nuclear capability, and these five countries were considered to be the 'Nuclear Powers' throughout the Cold War period.
After World War II, the balance of power between the Eastern and Western blocs, resulting in the fear of global destruction, prevented the further military use of atomic bombs. This fear was even a central part of Cold War strategy, referred to as the doctrine of Mutually Assured Destruction ("MAD" for short). So important was this balance to international political stability that a treaty, the Antiballistic Missile Treaty (or ABM treaty) was signed by the U.S. and the USSR in 1972 to curtail the development of defenses against nuclear weapons and the ballistic missiles which carry them. This doctrine resulting in a large increase in the number of nuclear weapons, as each side sought to ensure it possessed the firepower to destroy the opposition in all possible scenarios and against all perceived threats.
Early delivery systems for nuclear devices were primarily bombers like the American B-29 Superfortress and B-36 Peacemaker, and later the B-52 Stratofortress. Ballistic missile systems, based on designs used by Germany under Wernher von Braun (specifically the V2 rocket), were developed by both American and Soviet teams (in the case of U.S., effort was directed by the captured German scientists and engineers). These systems, after testing, were used to launch satellites, such as Sputnik, and to propel the Space Race, but they were primarily developed to create the capability of Intercontinental Ballistic Missiles (ICBMs) with which nuclear powers could deliver that destructive force anywhere on the globe. These systems continued to be developed throughout the Cold War, although plans and treaties, beginning with the Strategic Arms Limitation Treaty (SALT I), restricted deployment of these systems until, after the fall of the Soviet Union, system development essentially halted, and many weapons were disabled and destroyed (see nuclear disarmament).
There have been a number of potential nuclear disasters. Following air accidents U.S. nuclear weapons have been lost near Atlantic City, New Jersey (1957), Savannah, Georgia (1958) (see Tybee Bomb), Goldsboro, North Carolina (1961), off the coast of Okinawa (1965), in the sea near Palomares, Spain (1966) and near Thule, Greenland (1968). Most of the lost weapons were recovered, the Spanish device after three months' effort by the DSV Alvin and DSV Aluminaut. The Soviet Union was less forthcoming about such incidents, but the environmental group Greenpeace believes that there are around forty non-U.S. nuclear devices that have been lost and not recovered, compared to eleven lost by America, mostly in submarine disasters. The U.S. have tried to recover Soviet devices, notably in the 1974 Operation Jennifer using the specialist salvage vessel Hughes Glomar Explorer.
On January 27, 1967, more than 60 nations signed the Outer Space Treaty banning nuclear weapons in space.
The end of the Cold War failed to bring an end to the threat of the use of nuclear weapons, although global fears of nuclear war reduced substantially.
In a major move of deescalation, Boris Yeltsin on January 26, 1992 announced that Russia planned to stop targeting United States cities with nuclear weapons.
Nuclear proliferation
- See the main article at Nuclear proliferation.
France made a point of conducting above-ground tests of nuclear weapons in the 1990s.
India's first test atomic explosion was in 1974 with Smiling Buddha, which it initially described as a 'peaceful nuclear explosion'. India tested fission and perhaps fusion devices in 1998 and Pakistan successfully tested fission devices that same year, raising concerns that they would use nuclear weapons on each other. All of the former Soviet bloc countries with nuclear weapons (Belarus, Ukraine, and Kazakhstan) returned their warheads to Russia by 1996, though recent data has suggested that a clerical error may have left some warheads in the Ukraine.
In January 2004, Pakistani metallurgist and weapons scientist Abdul Qadeer Khan confessed to having been a part of an international proliferation network of materials, knowledge, and machines from Pakistan to Libya, Iran, and North Korea.
South Africa also had an active program to develop uranium based nuclear weapons, but dismantled its nuclear weapon program in the 1990s. It is not believed that it actually tested such a weapon though it later claimed to have constructed several crude devices which it eventually dismantled. In the late 1970s American spy satellites detected what appeared to be a flash of gamma rays which have been speculated to be a South African atomic test, but a later scientific review of the data suggested it may have been caused by natural events.
Israel is widely believed to possess an arsenal of potentially up to several hundred nuclear warheads, but this has never been officially confirmed or denied (though the existence of their Dimona nuclear facility was more or less confirmed by the leaks of dissident Mordechai Vanunu in 1986).
The United Kingdom has not run an independent development program since the failure of Blue Streak missile in the 1960s, buying American delivery systems and fitting British warheads instead (Polaris Sales Agreement).
The People's Republic of China possesses an arsenal of nuclear warheads estimated to be around 400 strong (in 2002). In 2003, North Korea announced it also had several nuclear explosives though it has not been confirmed and the validity of this has been a subject of scrutiny amongst weapons experts.
Nuclear testing
- See the main article at Nuclear testing.
There have been around 2,000 nuclear explosions:
- United States: 1,030 tests (involving 1,125 devices), at Alamagordo, New Mexico, Nevada Test Site and different islands like the Bikini Atoll.
- Soviet Union: 715 tests, including tests at Semipalatinsk, Novaya Zemlya and Kapustin Yar Test Sites.
- France: 210 tests, at the Mururoa Atoll and in Algeria.
- United Kingdom: 45 tests (21 in Australian territory, including 9 in mainland South Australia at Maralinga and Emu Field). Including tests at different islands and test cooperations with the United States.
- People's Republic of China: 45 tests (23 atmospheric and 22 underground, all conducted at Lop Nur Nuclear Weapons Test Base, in Malan, Xinjiang)
- India: 6 tests.
- Pakistan: 6 tests.
See also
- Manhattan Project
- Los Alamos National Laboratory
- Nuclear explosion
- Nuclear test explosion
- Nuclear weapon
- Nuclear weapon design
- Nuclear warfare
- Nuclear arms race
- Nuclear proliferation
- List of nuclear accidents
- Japanese atomic program
References
- Rhodes, Richard. Dark Sun: The Making of the Hydrogen Bomb. Simon and Schuster, New York, 1995.
- Rhodes, Richard. The Making of the Atomic Bomb. Simon and Schuster, New York, 1986.
External links
- Timeline of atomic age events
- Nuclear History Documents from the National Security Archive
- Federation of American Scientists - Worldwide Nuclear Forces Guide
- Nuclear Weapons Archive - includes the nuclear weapon histories of many countries