Instruct: Given a question, retrieve passages that answer the question.
Query: Who developed the first thermonuclear weapon?
The first full-scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons. The design of all modern thermonuclear weapons in the United States is known as the "Teller–Ulam configuration" for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist John von Neumann. Similar devices were developed by the Soviet Union, United Kingdom, France, and China.
The primary application to date has been military (i.e. nuclear weapons), and the remainder of explosions include the following:Only two nuclear weapons have been deployed in combat—both by the United States against Japan in World War II. The first event occurred on the morning of 6 August 1945, when the United States Army Air Forces dropped a uranium gun-type device, code-named "Little Boy", on the city of Hiroshima, killing 70,000 people, including 20,000 Japanese combatants and 20,000 Korean slave laborers. The second event occurred three days later when the United States Army Air Forces dropped a plutonium implosion-type device, code-named "Fat Man", on the city of Nagasaki. It killed 39,000 people, including 27,778 Japanese munitions employees, 2,000 Korean slave laborers, and 150 Japanese combatants. In total, around 109,000 people were killed in these bombings. (See "Atomic bombings of Hiroshima and Nagasaki" for a full discussion). Nuclear weapons are largely seen as a 'deterrent' by most governments; the sheer scale of the destruction caused by a nuclear weapon has prevented serious consideration of their use in warfare, rendering the concept of total war completely useless.
Much of the stimulus for the treaty was increasing public unease about radioactive fallout as a result of above-ground or underwater nuclear testing, particularly given the increasing power of nuclear devices, as well as concern about the general environmental damage caused by testing. In 1952–53, the US and Soviet Union detonated their first thermonuclear weapons (hydrogen bombs), far more powerful than the atomic bombs tested and deployed since 1945. In 1954, the US Castle Bravo test at Bikini Atoll (part of Operation Castle) had a yield of 15 megatons of TNT, more than doubling the expected yield. The Castle Bravo test resulted in the worst radiological event in US history as radioactive particles spread over more than , affected inhabited areas (including Rongelap Atoll and Utirik Atoll), and sickened Japanese fishermen aboard the "Lucky Dragon" upon whom "ashes of death" had rained. In the same year, a Soviet test sent radioactive particles over Japan. Around the same time, victims of the atomic bombing of Hiroshima visited the US for medical care, which attracted significant public attention. In 1961, the Soviet Union tested the Tsar Bomba, which had a yield of 50 megatons and remains the most powerful man-made explosion in history, though due to a highly efficient detonation fallout was relatively limited. Between 1951 and 1958, the US conducted 166 atmospheric tests, the Soviet Union conducted 82, and Britain conducted 21; only 22 underground tests were conducted in this period (all by the US).
The United States is known to have possessed three types of weapons of mass destruction: nuclear weapons, chemical weapons, and biological weapons. The U.S. is the only country to have used nuclear weapons in combat, when it detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki during World War II. It had secretly developed the earliest form of the atomic weapon during the 1940s under the title "Manhattan Project". The United States pioneered the development of both the nuclear fission and hydrogen bombs (the latter involving nuclear fusion). It was the world's first and only nuclear power for four years (1945–1949), until the Soviet Union managed to produce its own nuclear weapon. The United States has the second largest number of deployed nuclear weapons in the world, after Russia.
The most notable event of "Operation Castle" was the "Castle Bravo" test. The dry fuel for "Bravo" was 40% Li-6 and 60% Li-7. Only the Li-6 was expected to breed tritium for the deuterium-tritium fusion reaction; the Li-7 was expected to be inert. Yet J. Carson Mark, the head of the Los Alamos Theoretical Design Division, had speculated that "Bravo" could "go big", estimating that the device could produce an explosive yield as much as 20% more than had been originally calculated. It was discovered, because of the unexpected larger yield, that the Li-7 in the device also undergoes breeding that produces tritium. In practice, "Bravo" exceeded expectations by 150%, yielding 15 Mt — about 1,000 times more powerful than the "Little Boy" weapon used on Hiroshima. "Castle Bravo" remains to this day, the largest detonation ever carried out anywhere by the United States, and the fifth largest H-bomb detonation in the world.
A thermonuclear weapon, or fusion weapon, is a second-generation nuclear weapon design which affords vastly greater destructive power than first-generation atomic bombs. Modern fusion weapons consist essentially of two main components: a nuclear fission primary stage (fueled by Uranium-235 or Plutonium-239) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium and tritium, or in modern weapons lithium deuteride. For this reason thermonuclear weapons are often colloquially called hydrogen bombs, or H-bombs.
The United States developed the first nuclear weapons during World War II in cooperation with the United Kingdom and Canada as part of the Manhattan Project, out of the fear that Nazi Germany would develop them first. It tested the first nuclear weapon on July 16, 1945 ("Trinity") at 5:30 am, and remains the only country to have used nuclear weapons in war, devastating the Japanese cities of Hiroshima and Nagasaki. It was the first nation to develop the hydrogen bomb, testing an experimental prototype in 1952 ("Ivy Mike") and a deployable weapon in 1954 ("Castle Bravo"). Throughout the Cold War it continued to modernize and enlarge its nuclear arsenal, but from 1992 on has been involved primarily in a program of Stockpile stewardship. The U.S. nuclear arsenal contained 31,175 warheads at its Cold War height (in 1966). During the Cold War, the United States built approximately 70,000 nuclear warheads, more than all other nuclear-weapon states combined.
On 10 June 1948, Tamm headed a new group of theorists which included Andrei Sakharov, Vitaly Ginzburg, S.Z. Belenky and Romanov. They followed up Sakharov's ideas for a new thermonuclear weapon and went to KB-11 (now the All-Russian Scientific Research Institute of Experimental Physics) in the closed city of Sarov, Nizhny Novgorod. He started as a junior researcher, then senior, then head of department. In 1952, he received a degree in Physical and Mathematical Sciences with a thesis on kinetic processes of neutrons. This work on neutrons and efficiency continued, along with calculations on nuclear reaction kinetics and energy release of the Soviet Union's first thermonuclear weapon, the RDS-6, tested in 1953; for this he was awarded the Stalin Prize, the first of several awards. He was a leading developer of the RDS-37 - the first Soviet two-stage thermonuclear weapon - most specifically concerned with the power output. Romanov transferred to the new Scientific Research Institute-1011 as head of the theoretical department in 1955. Two years later, his team had developed a new megatonne-yield bomb design. He gained a Ph.D. in Physical and Mathematical Sciences in 1958 and was appointed to professorship of theoretical physics in 1962.
Only six countries—United States, Russia, United Kingdom, China, France, and India—have conducted thermonuclear weapon tests. (Whether India has detonated a "true" multi-staged thermonuclear weapon is controversial.) North Korea claims to have tested a fusion weapon , though this claim is disputed. Thermonuclear weapons are considered much more difficult to successfully design and execute than primitive fission weapons. Almost all of the nuclear weapons deployed today use the thermonuclear design because it is more efficient.
In the United States, where Fermi and Szilárd had both emigrated, the discovery of the nuclear chain reaction led to the creation of the first man-made reactor, the research reactor known as Chicago Pile-1, which achieved self-sustaining power/criticality on December 2, 1942. The reactor's development was part of the Manhattan Project, the Allied effort to create atomic bombs during World War II. It led to the building of larger single-purpose production reactors, such as the X-10 Pile, for the production of weapons-grade plutonium for use in the first nuclear weapons. The United States tested the first nuclear weapon in July 1945, the Trinity test, with the atomic bombings of Hiroshima and Nagasaki taking place one month later.
So far, two nuclear weapons have been used in the course of warfare, both by the United States near the end of World War II. On August 6, 1945, a uranium gun-type device (code name "Little Boy") was detonated over the Japanese city of Hiroshima. Three days later, on August 9, a plutonium implosion-type device (code name "Fat Man") was detonated over the Japanese city of Nagasaki. These two bombings resulted in the deaths of approximately 120,000 people.
The only country to have used a nuclear weapon in war is the United States, which dropped two atomic bombs on the Japanese cities of Hiroshima and Nagasaki during World War II. There are eight countries that have declared they possess nuclear weapons and are known to have tested a nuclear weapon, only five of which are members of the NPT. The eight are China, France, India, North Korea, Pakistan, Russia, the United Kingdom, and the United States.
In January 1933, Adolf Hitler was appointed Chancellor of Germany and it quickly became unsafe for Jewish scientists to remain in the country. Leó Szilárd fled to London where he proposed, and in 1934 patented, the idea of a nuclear chain reaction via neutrons. The patent also introduced the term critical mass to describe the minimum amount of material required to sustain the chain reaction and its potential to cause an explosion. (British patent 630,726.) He subsequently assigned the patent to the British Admiralty so that it could be covered by the Official Secrets Act. In a very real sense, Szilárd was the father of the atomic bomb academically.
Also in 1934, Irène and Frédéric Joliot-Curie discovered that artificial radioactivity could be induced in stable elements by bombarding them with alpha particles; Enrico Fermi reported similar results when bombarding uranium with neutrons.
Since the atomic bombings of Hiroshima and Nagasaki, nuclear weapons have been detonated over two thousand times for testing and demonstration. Only a few nations possess such weapons or are suspected of seeking them. The only countries known to have detonated nuclear weapons—and acknowledge possessing them—are (chronologically by date of first test) the United States, the Soviet Union (succeeded as a nuclear power by Russia), the United Kingdom, France, China, India, Pakistan, and North Korea. Israel is believed to possess nuclear weapons, though, in a policy of deliberate ambiguity, it does not acknowledge having them. Germany, Italy, Turkey, Belgium and the Netherlands are nuclear weapons sharing states. South Africa is the only country to have independently developed and then renounced and dismantled its nuclear weapons.
On August 6, 1945, the uranium-type nuclear weapon codenamed "Little Boy" was detonated over the Japanese city of Hiroshima with an energy of about , destroying nearly 50,000 buildings (including the headquarters of the 2nd General Army and Fifth Division) and killing approximately 70,000 people, including 20,000 Japanese combatants and 20,000 Korean slave laborers. Three days later, on August 9, a plutonium-type nuclear weapon codenamed "Fat Man" was used against the Japanese city of Nagasaki, with the explosion equivalent to about , destroying 60% of the city and killing approximately 35,000 people, including 23,200–28,200 Japanese munitions workers, 2,000 Korean slave laborers, and 150 Japanese combatants. The industrial damage in Nagasaki was high, partly owing to the inadvertent targeting of the industrial zone, leaving 68–80 percent of the non-dock industrial production destroyed.
Research into the development of nuclear weapons was initially undertaken during World War II by the United States (in cooperation with the United Kingdom and Canada), Germany, Japan, and the USSR. The United States was the first and is the only country to have used a nuclear weapon in war, when it used two bombs against Japan in August 1945. After surrendering to end the war, Germany and Japan ceased to be involved in any nuclear weapon research. In August 1949, the USSR tested a nuclear weapon, becoming the second country to detonate a nuclear bomb. The United Kingdom first tested a nuclear weapon in October 1952. France first tested a nuclear weapon in 1960. The People's Republic of China detonated a nuclear weapon in 1964. India conducted its first nuclear test in 1974, which prompted Pakistan to develop its own nuclear program and, when India conducted a second series of nuclear tests in 1998, Pakistan followed with a series of tests of its own. In 2006, North Korea conducted its first nuclear test.
In July 1954, the Cabinet decided to develop the hydrogen bomb. The United Kingdom Atomic Energy Authority Atomic Weapons Research Establishment at Aldermaston produced three designs: Orange Herald, a large boosted fission weapon; Green Bamboo, an interim thermonuclear design; and Green Granite, a true thermonuclear weapon. The first test series consisted of three tests in May and June 1957. In the first, Grapple 1, a version of Green Granite known as Short Granite was dropped from a Vickers Valiant bomber flown by Wing Commander Kenneth Hubbard. The bomb's yield was estimated at , far below its designed capability. Despite its failure, the test was hailed as a successful thermonuclear explosion, and the government did not confirm or deny reports that the UK had become a third thermonuclear power. The second test was Grapple 2, of Orange Herald. Its yield made it technically a megaton weapon. It was the largest ever achieved by a single stage device. Grapple 3 tested Purple Granite, a Short Granite with some fixes. Its yield was a very disappointing .
Before the Castle Bravo nuclear weapons test in 1954, it was thought that only the less common isotope lithium-6 would breed tritium when struck with fast neutrons. The Castle Bravo test showed (accidentally) that the more plentiful lithium-7 also does so under extreme conditions, albeit by an endothermic reaction.
After the bombings of Hiroshima and Nagasaki, the world’s nuclear weapons stockpiles grew, and nuclear weapons have been detonated on over two thousand occasions for testing and demonstration purposes. Countries known to have detonated nuclear weapons—and that acknowledge possessing such weapons—are (chronologically): the United States, the Soviet Union (succeeded as a nuclear power by Russia), the United Kingdom, France, the People's Republic of China, India, Pakistan, and North Korea.
The power of large bombs is typically measured in kilotons (kt) or megatons of TNT (Mt). The most powerful bombs ever used in combat were the two atomic bombs dropped by the United States to attack Hiroshima and Nagasaki, and the most powerful ever tested was the Tsar Bomba. The most powerful non-nuclear bomb is Russian "Father of All Bombs" (officially Aviation Thermobaric Bomb of Increased Power (ATBIP)) followed by the United States Air Force's MOAB (officially Massive Ordnance Air Blast, or more commonly known as the "Mother of All Bombs").
As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above , virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using the Teller–Ulam design.
McCormack became involved in discussions with Edward Teller over the possibility of developing thermonuclear weapons, then known as the "Super". McCormack became an early advocate of the Super, which promised yields in the megaton range, and directed Norris Bradbury at the Los Alamos National Laboratory to proceed with its development even at the detriment of other weapons. The debate over the merits of the Super pitted the United States Air Force against the other services, which wanted more small, tactical weapons. Concurrently, there was a technical debate between Teller and other scientists like Robert Oppenheimer over the feasibility of the Super, because there was no guarantee that it would work, and even after Operation Greenhouse, the processes involved in thermonuclear reactions were not fully understood. It ultimately became apparent that the Super design would not work, but the development of the Teller-Ulam design provided a new path to high yield thermonuclear weapons. For his services as Director of Military Applications, McCormack was awarded the Army Distinguished Service Medal.
Test No. 6 is the codename for China's first test of a three-staged thermonuclear device and, also its sixth nuclear weapons test. The device was detonated at Lop Nur Test Base, or often dubbed as Lop Nur Nuclear Weapon Test Base, in Malan, Xinjiang, on 17 June 1967. With successful testing of this three-stage thermonuclear device, China became the fourth country to have successfully developed a thermonuclear weapon after the United States, Soviet Union and the United Kingdom. It was dropped from a Hong-6 (Chinese manufactured Tu-16) and was parachute-retarded for an airburst at 2960 meters. The bomb was a three-stage device with a boosted U-235 primary and U-238 pusher. The yield was 3.3 megatons.
The Soviet thermonuclear weapons program was aided heavily by Klaus Fuchs. Fuchs’ most valuable contribution to the Soviet weapons program concerned the hydrogen bomb. The idea of a hydrogen bomb arose from discussions between Enrico Fermi and Edward Teller in 1941. From 1943 Teller lectured at Los Alamos on what he called the "super". Following their meeting, Fermi was convinced by Teller to present a series of lectures detailing the current state of research into thermonuclear weapons. In September 1945 Fuchs passed a synopsis of these lectures to the Soviets. This information was important to the Soviets, but not solely for the information about the US bomb project. The importance of this material was in that it confirmed that the United States were working on their own thermonuclear weapon research. Although the information provided by Fuchs regarding the thermonuclear weapons research was not seen as entirely beneficial, it still provided the Soviet Union with knowledge such as the properties of tritium. Tritium is an isotope of hydrogen with two neutrons, which allows for more efficient fusion reactions to occur during the detonation of a nuclear weapon. Discovering the properties of this radioactive material would allow the Soviet Union to develop a more powerful weapon that requires less fuel. Following Fuchs's return, experts from the Soviet Union spent a great deal of time researching his findings for themselves. Even though the Soviets did obtain some original ideas, the findings of this research served to confirm Fuchs's notes from the American lectures on the matter. After his return to England in mid-1946, Fuchs was not again in touch with Soviet intelligence until September 1947, when his controller confirmed the Soviet interest in thermonuclear weapons. In response Fuchs provided details of the "ongoing theoretical superbomb studies in the U.S. under the direction of Teller and Enrico Fermi at the University of Chicago." Fuchs obtained information regardless of the American McMahon Act, which prevented Anglo-American cooperation on nuclear weapons research. Under this act, Fuchs did not have routine access to American collaborators like Fermi and Teller. Fuchs was very close to Teller at Los Alamos, and while there Fuchs had worked on thermonuclear weapons. As Teller later recalled, "he [Fuchs] talked with me and others frequently in depth about our intensive efforts… it was easy and pleasant to discuss my work with him. He also made impressive contributions, and I learned many technical facts from him." Fuchs obtained the information, it energized the Soviets to direct new intelligence activities against research in Chicago. In February 1948 the Soviet Union formally began its hydrogen bomb program. A month later Fuchs again met with Feklisov, an event which "played an exceptional role in the subsequent course of the Soviet thermonuclear bomb program." A report of June 1953 warned that, although no indication of Soviet development of hydrogen bombs had been found, "Soviet research, development and even field testing of thermonuclear reactions based on the disclosures of Fuchs may take place by mid-1953." U.S. intelligence thus recognized for the first time that Fuchs' material held invaluable information for the Soviet thermonuclear weapons program.
In 1953, shortly after the Americans tested a thermonuclear weapon in 1952, followed by the Soviets with Joe 4, and before the UK government took a decision in July 1954 to develop a thermonuclear weapon, the Atomic Weapons Research Establishment at Aldermaston was asked about the possibilities for a very large pure fission bomb with a yield of one megaton. This study referred to the Zodiak Mk.3 bomb, but progressed no further than a rudimentary study. At this time studies were also started that ultimately led to a decision in 1954 to develop a thermonuclear weapon, and the design studies were split into two tracks because the British at that time had not yet discovered the Teller-Ulam technique necessary to initiate fusion. One track led to an intermediate design, the so-called Type A thermonuclear design, similar to the Alarm Clock and layer cake hybrid designs of other nuclear powers; although these designs are now regarded as large boosted fission weapons, and no longer regarded as thermonuclear weapons that derive a very large part of their energy from a fusion reaction, designated by the British as Type B, but as hybrids. The British hybrid weapon was known as Green Bamboo, weighed approx 4,500 lb (2,045 kg) and its spherical shape measured approx 45 inches diameter with a 72-point implosion system. This Green Bamboo weapon was intended as the warhead for all projected British strategic delivery systems of the period; the Yellow Sun Stage 1 air-dropped bomb, and the Blue Steel air-launched stand-off missile. The large girth of these weapons was designed to accommodate the diameter of Green Bamboo's implosion sphere.