Everything about Nuclear Weapon totally explained
A
nuclear weapon is an explosive device that derives its destructive force from the
nuclear reaction of
fission or from a combination of fission and
fusion. As a result, even a nuclear
weapon with a small
yield is significantly more powerful than the largest conventional
explosives available, with a single weapon capable of destroying an entire city.
In the
history of warfare, only two nuclear weapons have been detonated offensively, both by the
United States of America during the closing days of
World War II. The first was detonated 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 was detonated three days later when the United States dropped a
plutonium implosion-type device code-named "
Fat Man" on the city of
Nagasaki. These
bombings resulted in the immediate deaths of around 120,000 people from injuries sustained from the explosion and acute radiation sickness, and even more deaths over time from long-term effects of radiation. The use of these weapons was and remains controversial. (See
Atomic bombings of Hiroshima and Nagasaki for a full discussion.)
Since the Hiroshima and Nagasaki bombings, nuclear weapons have been detonated on over two thousand occasions for
testing purposes and demonstration purposes. The only countries known to have detonated such weapons are (chronologically) the
United States, the
Soviet Union, the
United Kingdom,
France, the
People's Republic of China,
India,
Pakistan, and
North Korea.
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, who has modern airborne delivery systems and appears to have an extensive nuclear program with hundreds of
warheads (see
Israel and weapons of mass destruction), officially maintains a policy of "
ambiguity" with respect to its actual possession of nuclear weapons. According to some estimates, it possesses as many as 200 nuclear warheads.
Iran currently stands accused by the
United States of attempting to develop nuclear weapons capabilities, though its government states that its
acknowledged nuclear activities, such as
uranium enrichment, are for non-weapons purposes.
South Africa also secretly developed a small nuclear arsenal, but disassembled it in the early 1990s. (For more information see
List of states with nuclear weapons.)
Apart from their use as weapons,
nuclear explosives have been tested and used for various
non-military uses. Synthetic elements, such as
einsteinium and
fermium, created by neutron bombardment of uranium and plutonium during thermonuclear explosions, were discovered in the aftermath of the first hydrogen bomb test.
History
The first nuclear weapons were created in the United States by an international team, including many displaced scientists from central Europe, which included Germany, 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. The
first test was conducted on
July 16,
1945 at a site near
Alamogordo,
New Mexico. 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 (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 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 four other countries (
India,
South Africa,
Pakistan, and
Israel) developed or acquired 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 performing a test in 2006. 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.
There have been (at least) 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 2006, there are estimated to be at least 27,000 nuclear weapons held by at least eight countries, 96 percent of them in the possession of the
United States and
Russia.
Nuclear weapons have been at the heart of many national and international political disputes, 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. Dozens of movies, books, television shows, plays, and other cultural productions have been made with nuclear weapons as either the explicit subject or an implied leitmotiv.
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,
A-bombs, or
fission bombs. In fission weapons, a mass of
fissile material (
enriched uranium or
plutonium) 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 sub-critical material into another (the "gun" method), or by compressing a sub-critical sphere of material using
chemical explosives to many times its original density (the "implosion" method). The latter approach is considered more sophisticated than the former, and only the latter approach can be used if plutonium is the fissile material.
A major challenge in all nuclear weapon designs is to ensure 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 (500
kilotons) 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 as fusion reactions release much more energy per unit of mass than fission reactions. 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
India—have detonated hydrogen bombs.
Hydrogen bombs work by using the energy of a fission bomb in order to compress and heat fusion fuel. In the
Teller-Ulam design, which accounts for all multi-megaton yield hydrogen bombs, this is accomplished by placing a fission bomb and fusion fuel (
tritium,
deuterium, or
lithium deuteride) in proximity within a special, radiation-reflecting container. When the fission bomb is detonated,
gamma and
X-rays emitted at the speed of light first compress the fusion fuel, then heat it to thermonuclear temperatures. The ensuing fusion reaction creates enormous numbers of high-speed
neutrons, which then can induce fission in materials which normally are not prone to it, such as
depleted uranium. Each of these components is known as a "stage," with the fission bomb as the "primary" and the fusion capsule as the "secondary." In large hydrogen bombs, about half of the yield, and much of the resulting
nuclear fallout, comes from the final fissioning of depleted uranium.
There are many 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 isn't a hydrogen bomb. In the boosted bomb, the neutrons produced by the fusion reactions serve primarily to increase the efficiency of the fission 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; such a device could theoretically be used to cause massive casualties while leaving infrastructure mostly intact and creating a minimal amount of fallout. 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, and in manipulating design elements to attempt to make weapons extremely small.
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 doesn't 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 (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 several targets from any one missile, reducing the chance of any successful
missile defense. Today, missiles are 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.
(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.
Governance, control, and law
Because of the immense military power they can confer, the political control of nuclear weapons has been a key issue for as long as they've existed; in most countries the use of nuclear force can only be authorized by the
head of government. In the United States, the President and the Secretary of Defense, acting as the
National Command Authority, must
jointly authorize the use of nuclear weapons.
In the late 1940s, lack of mutual trust was preventing the United States and the Soviet Union from making ground towards international arms control agreements, but by the 1960s steps were being taken to limit both the
proliferation of nuclear weapons to other countries and the environmental effects of
nuclear testing. The
Partial Test Ban Treaty (1963) restricted all nuclear testing to
underground nuclear testing, to prevent contamination from
nuclear fallout, while the
Nuclear Non-Proliferation Treaty (1968) attempted to place restrictions on the types of activities which signatories could participate in, with the goal of allowing the transference of non-military
nuclear technology to member countries without fear of proliferation. In 1957, the
International Atomic Energy Agency (IAEA) was established under the mandate of the
United Nations in order to encourage the development of the peaceful applications of nuclear technology, provide international safeguards against its misuse, and facilitate the application of safety measures in its use. In 1996, many nations signed and ratified the
Comprehensive Test Ban Treaty which prohibits all testing of nuclear weapons, which would impose a significant hindrance to their development by any complying country.
Additional treaties have governed nuclear weapons stockpiles between individual countries, such as the
SALT I and
START I treaties, which limited the numbers and types of nuclear weapons between the United States and the Soviet Union.
Nuclear weapons have also been opposed by agreements between countries. Many nations have been declared
Nuclear-Weapon-Free Zones, areas where nuclear weapons production and deployment are prohibited, through the use of treaties. The
Treaty of Tlatelolco (1967) prohibited any production or deployment of nuclear weapons in
Latin America and the
Caribbean, and the
Treaty of Pelindaba (1964) prohibits nuclear weapons in many
African countries. As recently as 2006 a
Central Asian Nuclear Weapon Free Zone was established amongst the former Soviet republics of Central Asia prohibiting nuclear weapons.
In the middle of 1996, the
International Court of Justice, the highest court of the United Nations, issued an Advisory Opinion concerned with the "
Legality of the Threat or Use of Nuclear Weapons". The court ruled that the use or threat of use of nuclear weapons would violate various articles of
international law, including the
Geneva Conventions, the
Hague Conventions, the
UN Charter, and the
Universal Declaration of Human Rights.
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