Nuclear weapon
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A nuclear weapon is a weapon which derives its destructive force from the nuclear reactions of nuclear fission. Besides fission, a different kind of nuclear reaction called fusion can be used to create an even more powerful explosion. As a result, even a nuclear weapon with a relatively small yield is significantly more powerful than the largest conventional explosives, and a single weapon can be capable of destroying or seriously disabling an entire city.
In the history of warfare, nuclear weapons have been used on two occasions, both during the closing days of World War II. The first event occurred on the morning of 6 August 1945, when the United States dropped a uranium gun-type device code-named "Little Boy" on the Japanese city of Hiroshima. The second event occurred three days later when a plutonium implosion-type device code-named "Fat Man" was dropped on the city of Nagasaki. The use of the weapons, which resulted in the immediate deaths of at least 120,000 individuals (mostly civilians) and about twice that number over time, was and remains controversial — critics charged that they were unnecessary acts of mass killing, while others claimed that they ultimately reduced casualties on both sides by hastening the end of the war. (See Atomic bombings of Hiroshima and Nagasaki for a full discussion.)
Since that time, nuclear weapons have been detonated on over two thousand occasions, mostly for testing purposes, chiefly by the following seven countries: the United States, Soviet Union, United Kingdom, France, People's Republic of China, India and Pakistan. These countries are the declared nuclear powers (with Russia inheriting the weapons of the Soviet Union after its collapse).
Various other countries may hold nuclear weapons, but they have never publicly admitted possession, or their claims to possession have not been verified. For example, Israel has modern airborne delivery systems and appears to have an extensive nuclear program (see Israel and weapons of mass destruction); North Korea has recently stated that it has nuclear capabilities (although it has made several changing statements about the abandonment of its nuclear weapons programs, often dependent on the political climate at the time) and Iran was accused by a number of governments of attempting to develop nuclear capabilities, and now acknowledges that it is trying to obtain nuclear power for peaceful purposes. (for more information see List of countries with nuclear weapons).
Apart from their use as weapons, nuclear explosives have been proposed for various non-military uses.
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Types of nuclear weapons
- Main article: Nuclear weapon design
There are two basic types of nuclear weapons. The first are weapons which produce their explosive energy through nuclear fission reactions alone. These are known as colloquially as atomic bombs or A-bombs. In fission weapons, a mass of fissile material (enriched uranium or plutonium) is rapidly assembled into a critical mass, in which a chain reaction begins and grows exponentially, releasing tremendous amounts of energy. This is accomplished by rapidly creating supercriticality, either by shooting one piece of subcritical material into another, or compressing a subcritical mass. A major challenge in all nuclear weapon designs is ensuring that a significant fraction of the fuel is consumed before the weapon destroys itself.
The second basic type of nuclear weapon produces a large amount of its energy through nuclear fusion reactions, and can be over a hundred times more powerful than fission bombs. These are known as hydrogen bombs, H-bombs, thermonuclear bombs, and fusion bombs. They work by utilizing the Teller-Ulam design, in which a fission bomb is detonated next to fusion fuel. The X-rays of the fission explosion compress and heat a capsule of tritium, deuterium, or lithium, starting a fusion reaction. Each of these components are known as "stages". A final fission stage is often included as well for multi-megaton fusion weapons.
There are other types of nuclear weapons as well. For example, a boosted fission weapon is a fission bomb which increases its explosive yield through a small amount of fusion reactions, but it is not a hydrogen bomb. Some weapons are designed for special purposes; a neutron bomb is a nuclear weapon that yields a relatively small explosion but a relatively large amount of radiation. The detonation of a nuclear weapon is accompanied by a blast of neutron radiation. Surrounding a nuclear weapon with suitable materials (such as cobalt or gold) creates a weapon known as a salted bomb. This device can produce exceptionally large quantities of radioactive contamination. Most variety in nuclear weapon design is in different yields of nuclear weapons for different types of purposes.
Effects of a nuclear explosion
- Main article: Nuclear explosion
The energy released from a nuclear weapon comes in four primary categories:
- Blast – 40-60% of total energy
- Thermal radiation – 30-50% of total energy
- Ionizing radiation – 5% of total energy
- Residual radiation (fallout) – 5-10% of total energy
The amount of energy released in each form depends on the design of the weapon, and the environment in which it is detonated. The residual radiation of fallout is a delayed release of energy, while the other three forms of energy release occur immediately.
The damage from each of the three initial forms of energy release differs with the size (or "yield", see below) of the weapon. Thermal radiation drops off the slowest with distance, so the larger the weapon the more significant the impact of this effect. Ionizing radiation is strongly absorbed by air, so it is only dangerous by itself for smaller weapons. Blast damage falls off more quickly than thermal radiation but more slowly than ionizing radiation.
The energy released by a nuclear weapon is generally measured by the explosive power of an equivalent amount of trinitrotoluene, known as the weapon's yield. The yield of nuclear weapons may be rated as equivalent to several kilotons or megatons of TNT. The first fission weapons had yields measurable in the tens of kilotons, while the largest practical hydrogen bombs have yields around 20 megatons. In practice, nuclear weapon yields will vary significantly, from fractional kiloton weapons designed for tactical use on the battlefield (eg. the man-portable Davy Crockett warheads developed by the United States), to the record Tsar Bomba created by the Soviet Union which had a theoretical maximum design yield of around a hundred megatons.
Although a nuclear weapon is capable of causing the same destruction as conventional explosives through the effects of blast and thermal radiation, it does so by releasing much larger amounts of energy in a much shorter period of time. Most of the damage caused by a nuclear weapon is not directly related to the nuclear process of energy release, and would be present for any explosion of the same magnitude.
In human terms, nuclear weapons are enormously destructive. A weapon with a ten-megaton yield can destroy most of the buildings of a modern city, while a weapon with a hundred-megaton yield (although the deployment of such a weapon would be considered impractical) would set wooden structures and forests alight up to 60-100 miles (100-160 km) from ground zero1. A nuclear weapon detonated in the upper atmosphere will also generate an electromagnetic pulse which can disrupt or disable electronic communications and instruments over a wide area, causing more difficulties for those who survive the effects of a detonation. Concerns over the health and environmental effects of nuclear testing led to the passing of the Partial Test Ban Treaty in 1963 which prohibited atmospheric (above-ground), underwater, or outer space nuclear tests (underground testing continued, however).
Since most of the effects of nuclear weapons are blast, thermal, or fallout, well-known civil defense efforts could greatly reduce the total loss of life in a nuclear war.
Nuclear strategy
- Main article: Nuclear warfare
Nuclear warfare strategies are ways for either fighting or avoiding a nuclear war. The policy of trying to ward off a potential attack by a nuclear weapon from another country by threatening nuclear retaliation is known as the strategy of nuclear deterrence. The goal in deterrence is to always maintain a second strike status (the ability to respond to a nuclear attack against your country with a nuclear attack of your own) and potentially to strive for first strike status (the ability to completely destroy an enemy's nuclear forces before they could retaliate). During the Cold War, policy and military theorists in nuclear-enabled countries worked out models of what sorts of policies could prevent one from ever being attacked by a nuclear weapon.
Different forms of nuclear weapons delivery (see below) allow for different types of nuclear strategy, primarily by making it difficult to defend against them and difficult to launch a pre-emptive strike against them. Sometimes this has meant keeping the weapon locations hidden, such as putting them on submarines or train cars whose locations are very hard for an enemy to track, and other times this means burying them in hardened bunkers. Other responses have included attempts to make it seem likely that the country could survive a nuclear attack, by using missile defense (to destroy the missiles before they land) or by means of civil defense (using early warning systems to evacuate citizens to a safe area before an attack). Note that weapons which are designed to threaten large populations or to generally deter attacks are known as "strategic" weapons. Weapons which are designed to actually be used on a battlefield in military situations are known as "tactical" weapons.
There are critics of the very idea of "nuclear strategy" for waging nuclear war who have suggested that a nuclear war between two nuclear powers would result in mutual annihilation. From this point of view, the significance of nuclear weapons is to purely deter war because any nuclear war would immediately escalate out of mutual distrust and fear, resulting in Mutual Assured Destruction. This threat of national, if not global, destruction has been a strong motivation for anti-nuclear weapons activism.
Critics from the peace movement and within the military establishment have questioned the usefulness of such weapons in the current military climate. The use of (or threat of use of) such weapons would generally be contrary to the rules of international law applicable in armed conflict, according to an Advisory Opinion issued by the International Court of Justice in 1996.
Perhaps the most controversial idea in nuclear strategy is that nuclear proliferation would be desirable. This view argues that unlike conventional weapons nuclear weapons successfully deter all-out war between states, as they did during the Cold War between the U.S. and the USSR. Political scientist Kenneth Waltz is the most prominent advocate of this argument.
Weapons delivery
- Main article: Nuclear weapons delivery
Nuclear weapons delivery— the technology and systems used to bring a nuclear weapon to its target—is an important aspect of nuclear weapons relating both to nuclear weapon design and nuclear strategy.
Historically the first method of delivery, and the method used in the two nuclear weapons actually used in warfare, is as a gravity bomb, dropped from bomber aircraft. This method is usually the first developed by countries as it does not place many restrictions on the size of the weapon, and weapon miniaturization is something which requires considerable weapons design knowledge. It does, however, limit the range of attack, response time to an impending attack, and number of weapons which can be fielded at any given time.
More preferable from a strategic point of view are nuclear weapons mounted onto a missile, which can use a ballistic trajectory to deliver a warhead over the horizon. While even short range missiles allow for a faster and less vulnerable attack, the development of intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) has allowed some nations to plausibly deliver missiles anywhere on the globe with a high likelihood of success. More advanced systems, such as multiple independently targetable reentry vehicles (MIRVs) allow multiple warheads to be launched at a number of targets from any one missile, reducing the chance of any successful missile defense. Today missiles are by far the most common among systems designed for delivery of nuclear weapons. To make a warhead small enough to fit onto a missile, though, can be a difficult task.
"Tactical" weapons (see above) have involved the most variety of delivery types, including not only gravity bombs and missiles but also artillery shells, land mines, and nuclear depth charges and torpedoes for anti-submarine warfare. An atomic mortar was also tested at one time by the United States. Small, two-man portable tactical weapons (somewhat misleadingly referred to as suitcase bombs), such as the Special Atomic Demolition Munition, have been developed, although the difficulty to combine sufficient yield with portability limits their military utility.
History
- Main article: History of nuclear weapons
The first nuclear weapons were created by the United States, with assistance from the United Kingdom and Canada, during World War II as part of the top-secret Manhattan Project. While the first weapons were developed primarily out of fear that Nazi Germany would first develop them, they were eventually used against the Japanese cities of Hiroshima and Nagasaki in August 1945. The Soviet Union developed and tested their first nuclear weapon in 1949, based partially on information obtained from Soviet espionage in the United States. Both the USA and USSR would go on to develop weapons powered by nuclear fusion (hydrogen bombs) by the mid-1950s. With the invention of reliable rocketry during the 1960s, it became possible for nuclear weapons to be delivered anywhere in the world on a very short notice, and the two Cold War superpowers adopted a strategy of deterrence to maintain a shaky peace.
Nuclear weapons were symbols of military and national power, and nuclear testing was often used both to test new designs as well as to send political messages. Other nations also developed nuclear weapons during this time, including the United Kingdom, France, and China. These five members of the "nuclear club" agreed to attempt to limit the spread of nuclear proliferation to other nations, though at least three other countries (India, South Africa, Pakistan, and most likely Israel) developed nuclear arms during this time. At the end of the Cold War in the early 1990s, the Russian Federation inherited the weapons of the former USSR, and along with the USA pledged to reduce their stockpile for increased international safety. Nuclear proliferation has continued, though, with Pakistan testing their first weapons in 1998, and the state of North Korea claiming to have developed nuclear weapons in 2004. Nuclear weapons have been at the heart of many national and international political disputes, and have played a major part in popular culture since their dramatic public debut in the 1940s, and have usually symbolized the ultimate ability of mankind to utilize the strength of nature for destruction.
There have been (at least) four major false alarms, the most recent in 1995, that almost resulted in the US or USSR/Russia launching its weapons in retaliation for a supposed attack.[1] Additionally, during the Cold War the US and USSR came close to nuclear warfare a number of times, most notably during the Cuban Missile Crisis. As of 2005, there are estimated to be at least 29,000 nuclear weapons held by at least seven countries, though 96% of these are in the possession of just two (the United States and the Russian Federation).
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See also
| Weapons of | |
| mass destruction | |
| By Type | |
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| Biological weapons | |
| Chemical weapons | |
| Nuclear weapons | |
| Radiological weapons | |
| By country | |
| Brazil | Canada |
| China (PRC) | France |
| Germany | India |
| Iran | Iraq |
| Israel | Italy |
| Japan | Netherlands |
| North Korea | Pakistan |
| Poland | Russia |
| South Africa | Taiwan (ROC) |
| United Kingdom | United States |
| See also | |
| Dirty bomb | |
| Biodressing | |
| Radiological warfare edit |
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- More technical details
- History
- Related technology and science
- Military strategy
- Proliferation and politics
- Nuclear proliferation
- Nuclear Non-Proliferation Treaty
- Comprehensive Test Ban Treaty
- Nuclear disarmament
- International Court of Justice advisory opinion on legality of nuclear weapons
- List of countries with nuclear weapons
- Nuclear weapons and the United States
- Nuclear weapons and the United Kingdom
- List of nuclear weapons
- Popular culture
- Aftermath
References
- Note 1: p. 54. Bethe, Hans Albrecht. The Road from Los Alamos. New York: Simon and Schuster, 1991. ISBN 0-671-74012-1
- Glasstone, Samuel and Dolan, Philip J. The Effects of Nuclear Weapons (third edition). Washington, D.C.: U.S. Government Printing Office, 1977. Available online (PDF).
- NATO Handbook on the Medical Aspects of NBC Defensive Operations (Part I - Nuclear). Departments of the Army, Navy, and Air Force: Washington, D.C., 1996.
- Hansen, Chuck. U.S. Nuclear Weapons: The Secret History. Arlington, TX: Aerofax, 1988.
- Hansen, Chuck. The Swords of Armageddon: U.S. nuclear weapons development since 1945. Sunnyvale, CA: Chukelea Publications, 1995. [2]
- Smyth, Henry DeWolf. Atomic Energy for Military Purposes. Princeton, NJ: Princeton University Press, 1945. (Smyth Report – the first declassified report by the US government on nuclear weapons)
- The Effects of Nuclear War. Office of Technology Assessment, May 1979.
- Rhodes, Richard. Dark Sun: The Making of the Hydrogen Bomb. New York: Simon and Schuster, 1995. ISBN 0684824140
- _________. The Making of the Atomic Bomb. New York: Simon and Schuster, 1986 ISBN 0684813785
- Weart, Spencer R. Nuclear Fear: A History of Images. Cambridge, MA: Harvard University Press, 1988.
External links
- General
- Nuclear Weapon Archive from Carey Sublette is a reliable source of information and has links to other sources and an informative FAQ.
- The Federation of American Scientists provide solid information on weapons of mass destruction, including nuclear weapons and their effects
- Alsos Digital Library for Nuclear Issues – contains many resources related to nuclear weapons, including a historical and technical overview and searchable bibliography of web and print resources.
- Nuclear Files.org covers the history of nuclear weapons and explores the political, legal and ethical challenges of the Nuclear Age.
- Historical
- "The Race to Build the Atomic Bomb", educational resource.
- Effects
- Nuclear weapon simulator for several major cities
- Fallout Calculator for various regions
- Step by step scenario of a 150 kiloton bomb exploding in Manhattan - click on the Next >> button at the bottom of each slide.
- Issues
- "Nuclear Power and Nuclear Weapons: Making the Connections" – an article about the connections between nuclear power and nuclear weapons development by an anti-nuclear group.
- Nuclear War Survival Skills is a public domain text about civil defense.
- IPPNW: International Physicians for the Prevention of Nuclear War – Nobel Peace Prize-winning organization with information about the medical consequences of nuclear weapons, war and militarization.
- Bulletin of the Atomic Scientists – Magazine founded in 1945 by Manhattan Project scientists. Covers nuclear weapons proliferation and many other global security issues. See this page for comprehensive data on nuclear weapons worldwide.
- 50 Facts About U.S. Nuclear Weapons – Largest, smallest, number, cost, etc.
