Encyclopedia
A
nuclear weapon derives its destructive force from
nuclear reactions of
fission or
fusion. 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 is capable of destroying an entire city.
In the
history of warfare, nuclear weapons have been used only twice, both during the closing days of
World War II. The first event occurred on the morning of August 6, 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 these weapons, which resulted in the immediate deaths of around 100,000 to 200,000 individuals and even more 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. This topic has seen increased debate recently in the wake of increased terrorism involving killings of civilians by both state and non-state players, with parties claiming that the end justifies the means .
Since the Hiroshima and Nagasaki bombings, nuclear weapons have been detonated on over two thousand occasions for
testing and demonstration purposes. The only countries known to have detonated such weapons are the
United States,
Soviet Union,
United Kingdom,
France,
People's Republic of China,
India, and
Pakistan. These countries are the declared nuclear powers .
Various other countries may hold nuclear weapons but 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 with hundreds of warheads , though it officially maintains a policy of "ambiguity" with respect to its actual possession of nuclear weapons.
North Korea has recently stated that it has nuclear capabilities but has never conducted a confirmed test and its weapons status remains unclear.
Iran currently stands accused by a number of governments of attempting to develop nuclear capabilities, though its government claims that its acknowledged nuclear activities, such as
uranium enrichment, are for peaceful purposes.
South Africa also secretly developed a small nuclear arsenal, but disassembled it in the early 1990s.
Apart from their use as weapons, nuclear explosives have been tested and used for various
non-military uses.
Types of nuclear weapons
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 colloquially as
atomic bombs,
atom bombs,
A-bombs or
The bomb. In fission weapons, a mass of fissile material is assembled into a
supercritical mass—the amount of material needed to start an
exponentially growing nuclear chain reaction—either by shooting one piece of subcritical material into another, or by compressing a subcritical mass with
chemical explosives, at which points
neutrons are injected and the reaction begins. 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 amount of energy released by
fission bombs can range between the equivalent of less than a ton of
TNT upwards to around 500,000 tons of TNT.
The second basic type of nuclear weapon produces a large amount of its energy through
nuclear fusion reactions, and can be over a thousand times more powerful than fission bombs. These are known as
hydrogen bombs,
H-bombs,
thermonuclear bombs, or
fusion bombs. Only six countries—
United States,
Russia,
United Kingdom,
People's Republic of China,
France, and possibly
India—are known to possess hydrogen bombs. Hydrogen bombs work by utilizing the
Teller-Ulam design, in which a fission bomb is detonated in a specially manufactured compartment adjacent to a fusion fuel. The
gamma and
X-rays of the fission explosion compress and heat a capsule of
tritium,
deuterium, or lithium deuteride starting a fusion reaction.
Neutrons emitted by this fusion reaction can induce a final fission stage in a
depleted uranium tamper surrounding the fusion fuel, increasing the yield considerably as well as the amount of
nuclear fallout. Each of these components is known as a "stage", with the fission bomb as the "primary" and the fusion capsule as the "secondary". By chaining together numerous stages with increasing amounts of fusion fuel, thermonuclear weapons can be made to an almost arbitrary yield; the largest ever detonated released an energy equivalent to over 50 million tons of TNT, though most modern weapons are nowhere near that large.
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 prompt radiation. The detonation of a nuclear weapon is accompanied by a blast of neutron radiation. Surrounding a nuclear weapon with suitable materials 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, and in manipulating design elements to attempt to make weapons extremely small.
Nuclear strategy
Nuclear warfare strategy is a way 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 and potentially to strive for first strike status . 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 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 or by means of
civil defense . 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 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
Soviet Union. Political scientist Kenneth Waltz is the most prominent advocate of this argument.
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, the response time to an impending attack, and the number of weapons which can be fielded at any given time. Additionally, specialized delivery systems are usually not necessary; especially with the advent of miniaturization, nuclear bombs can be delivered by both
strategic bombers and tactical fighter-bombers, allowing an air force to use its current fleet with little or no modification. This method may still be considered the primary means of nuclear weapons delivery; the majority of U.S. nuclear warheads, for example, are represented in free-fall gravity bombs, namely the
B61.
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 and
submarine-launched ballistic missiles 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 allow multiple warheads to be launched at several targets from any one missile, reducing the chance of any successful missile defense. Today, missiles are the most common among systems designed for delivery of nuclear weapons. Making a warhead small enough to fit onto a missile, though, can be a difficult task.
Tactical weapons 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 , such as the
Special Atomic Demolition Munition, have been developed, although the difficulty to combine sufficient yield with portability limits their military utility.
History
The first nuclear weapons were created in the United States, by an international team including many displaced émigré scientists from central Europe 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 develop them first, 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 U.S. and
USSR would go on to develop weapons powered by
nuclear fusion 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 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 U.S., pledged to reduce their stockpile for increased international safety.
Nuclear proliferation has continued, though, with Pakistan testing their first weapons in 1998, and
North Korea claiming to have developed nuclear weapons in 2004. In January 2005, Pakistani metallurgist
Abdul Qadeer Khan confessed to selling nuclear technology and information of nuclear weapons to
Iran,
Libya, and North Korea in a massive, international proliferation ring.
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 four major false alarms, the most recent in 1995, that almost resulted in the U.S. or USSR/Russia launching its weapons in retaliation for a supposed attack. Additionally, during the Cold War the U.S. and USSR came close to nuclear warfare several 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, 96 percent of them in the possession of the United States and Russia.
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See also
- More technical details
- History
- Related technology and science
...
- Military strategy
- Proliferation and politics
- Popular culture
- Aftermath
- Nuclear winter
- Nuclear summer
References
External links
;General
- is a reliable source of information and has links to other sources and an informative .
- The provide solid information on weapons of mass destruction, including and their
- – contains many resources related to nuclear weapons, including a historical and technical overview and searchable bibliography of web and print resources.
- — Provided by New Scientist is a weekly international [i] science magazine [i] covering recent developments in sci ...
. -
;Historical
;Effects
- - Two scenarios of a nuclear explosion on two United States Cities
- These tables describe the effects of various nuclear blast sizes. All figures are for 15-mph winds. Thermal burns represent injuries to an unprotected person. The legend describes the data.
;Issues
- - OneWorld.net's Perspectives Magazine, May 2005
