A-bomb
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A-bomb, short for Atomic bomb, is a type of Nuclear weapon.
A fission type nuclear weapon is commonly known as an A-bomb. A-bombs can be fueled by several different fissionable elements, and fissionable istopes . These include U-235, U-233, Pu-239, Pu-240, Pu-242, Americanium, Californium, and others.
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Key elements
Plutonium 239, and Uranium 235 are almost always the fissionable elements on the periodic table that are used to fuel the atomic bomb. The mean neutron free path (MNP) is the maximium distance that a free neutron can travel after its emission , before it will either be absorbed by a non fissionable atom, or it will be absorbed by a fissionable atom. The length of the MNP is generaly 12.68 centimeters . When a free neutron is absorbed by a fissionable atom it will cause the atom to devide into two or more pieces known as fission fragments. This will result in less then .10 % of the mass of the fissioned atom being converted into atomic energy.
Physics
The amount of energy contained in a kilogram of matter is equal to
E = MC^2. The amount of energy contained in 1 kg of mass is approximately 9 * 10 ^16 joules. The nuclear fission of a single kilogram of fuel will therefore release approximately 9 * 10 ^ 14 joules of energy. This is equivelent to the energy that would be released by the detonation of from 17,000 - 23,000 tons of tnt
(Tri-nitrotoulene).
The eqaution for U-235 fission may be summarized as follows: U-235 + 0 N1 = Fission fragments + 2.5 0N1 + 180 Mev. The equation for Pu-239 fission is generally as follows. Pu-239 + 0 N1 = fission fragments + 3 0N1 + 200 mev. Weapons grade U-235 is obtained by refining natural uranium ore, and by enriching the U-235 content of natural uranium metal from .7% to 80% U-235 or more. Plutonium 239 is bred in atomic fission reactors from natural uranium 238 atoms that capture neutrons and then change into Pu239 atoms via the following nuclear reactions .
- U-238 + oN1 = U=239 :
- U-239 + b = Np239 :
- Np 239 + b = Pu239 :
The reactions that produce Pu-239 from U-238 that is irradiated
by neutrons are beta particle decay processes. U-235 atoms naturally undergo spontaneous nuclear fission at a certian rate over time . Pu-239 undegoes an alpha particle decay process. Its half life is 24,000 years. The half life of U-235 is about 250,000 years. The half life of U-238 is 4,500,000,000 years. To learn more about all the nuclear, physical, and chemical properties of the elements of Uranium, and Plutonium , and also about their various istopes look them up, and read about them.
A beta particle is a relatavistic electron, or positron that
that is released when a neutron decays, and thus changes into a proton. A beta particle is symbolized by the Greek letter Beta , which corresponds to the letter B in the latin alphabet.
An alpha particle is a positively charged high energy helium ion such as He3 ,or He4+. The symbol for an alpha particle is the Greek letter Alpha which corresponds to the letter A
in the Latin alphabet. A gamma ray (Y) is a very high energy, and high frequancy form of electromagnetic radiation (light). Nuclear radiation consists of 4 basic types. These are free high energy neutrons, Beta particles, alpha particles, and gamma rays.Certian materials, such as lead, iron, steel, and concrete can be used to absorb nuclear radiation and thus block it. Such materials can be used to thus make nuclear radiation shields, to provide protection against nuclear radiation..
A self sustaining nuclear fission chain reaction requires
that k = 1/3 for each of of the 2.5 to 3 neutrons released per fission event must cause another fissionable atom to actually undergo nuclear fission . So when K = 1/2.5 , or K = 1/ 3 this condition is known as a critical mass.
When K < 1/2.5 or K > 1/3 this defines a sub-critical mass.
K defines the statistical probability that a lone neutron
will cause an atom to undergo nuclear fission by the time it is absorbed. In order to have a 100 % probability of being absorbed a free neutron must travel a distance of 12.68 centimeters from the point of its origion.The assembly of a supercritical mass of fissionable material requires that k = 1.68 /2.5 or K = 2/3. 12.68 centimeters * .67 = 8.4956 cm which is a radius of 3.345 inches .
A solid ball of U-235 metal that has a radius of 3.45 inches will thus be a critical mass. The radius of a sphere is eqaul to 1/2 * the diameter of the sphere.
The purity of the fissionable material directly effects the
value of K. The density, and shape of the fissionable material also directly effects the value of K. Whether or not a mass of fissionable material is surrounded by a neutron reflector also directly effects the value of K
Therefore a supercritical bare metal ball of 100 % pure U-235 will have a diameter of 7.69 inches which is 17 centimeters. The density of Uranium is 18.9 gm/cm^3, and the density of plutonium is 19.1 gm/cm^3. The volume of a solid sphere is eqaul to 4/3 * 3.14259 * R ^3 . These numbers allow us to calculate the exact dimensions, shape , and the mass of a ball of critical, or supercritical fissionable material.
By calculation it can be shown that 1/2.5 = .40, and .40 * 100 % = 40 %. Therefore a neutron must travel through a solid sphere of fissionable material that has a radius = .4 * 12.68 Centimeters in order to have a 40% probability of fissioning an atom and thus make a single atomic critical mass. This is a distance of 5.072 cm. which is a radius of 1.9968 inches.
The smallest ball of U-235 or Pu-239 that will barely constitute one single critical mass must therefore have a diameter of 10.144 cm. This calculation applies only to bare metal spheres that do not have a neutron reflector wrapped around them. * In order to trigger an efficient atomic explosion it is necessary to assemble a solid sphere made of two or critical masses of metallic fissionable material.
The critical mass for a bare metal ball of pure U-235 ball with no neutron reflector wrapped around it is approximately 50 kg. The critical mass for a bare metal ball of Plutonium 239 with no neutron reflector wrapped around it is 16 kilograms. The gun method of detonating an atomic bomb creates a super critical mass by blowing enough fissionable material together into a common metal ball to create a supercritical size.
Elements of fission type nuclear weapon design
In the gun method the pit is assembled by bringing two or more sub critical masses of fissionable material together using a chemical explosive such as cordite. This may be done in the following manner: Place two 30 kg hemispheres of 90% pure U-235 metal at opposite ends of a 2 meter long, and two inch thick steel gun(artillary) barrel.Plug one end of the barrel with a steel block, and insert a screw on cartidge containing a 30 kg hemisphere of U-235 , backed by a charge of cordite (white smokeless gunpowder),placed at the other end of the steel gun barrel.
The cordite charge should be just the right mass to propell the U-235 hemisphere through the gun barrel at a muzzle velocity of 300-400 m/sec when it explodes. In order to ensure that the explosion of the cordite will not rupture the gun barrel, the
hollow cylindrical steel gun barrel should have at least 100 times the mass of the U-235 Hemisphere (bullet). This will assemble the equivelent of at least two critical masses in the pit. This will result in an 8-10 kiloton atomic explosion.
The mass, and size of a basic, and primative devices like the little Boy A-bomb of 1945 is usually very large .For this reason the primative versions of this kind of device are probably useless to anyone other then mid 20th century style, moderately developed industrial nation states.
It is however, possible to produce advanced gun type atomic
weapons that have a much lower mass, and a much smaller size. This is possible if your nuclear weapon technology is sufficiently sophisticated, and modern. Some advanced, and modern gun type atomic weapons may have only 5% or 10 % of the mass of the origional Little Boy A-bomb of 1945. Such advanced designs have often been used to create atomic artillary shells, atomic land mines, atomic depth charges, and military special operations atomic weapons.
The atomic fission yield can be increased by 1. adding more fissionable fuel to the pit, 2. using fusion neutron boosting on the pit, 3. using a more efficient neutron reflector wrapped around the pit such as tungsten carbide, or berylium metal. It is also possible to add a secondary fusion charge, and use the gun type atomic bomb as the primary to trigger a thermonuclear explosion via the teller ulam-radiation implosion technique.
It is important for the mass of the steel gun barrel to be at least 3000 kg if a 30 kg projectile is fired in the barrel. By the time atomic radiation shielding, the fuze, and any secondary physics package is added the device may mass 4000- 5000 kg like the little Boy A-bomb of 1945.
The critical mass can be reduced by placing a hollow spherical tamper made of U-238, Berylium 9, or Tungsten carbide around a solid, or hollow sphere of the fissionable material. The critical mass for a ball of U-235 surrounded by a steel neutron reflector is 27 Kg. In addition to reducing the critical mass, the tamper
can also increase the yield of the A-bomb when it explodes by slowing down the dis-assembly of the core during an atomic explosion . The longer it takes to dis-asemble a core that is surrounded by a heavy massive tamper ,the larger the fraction of the mass of the atomic fuel that will be fissioned during the explosion.
If we surround the U-235 ball with tungsten carbide the critical
mass is 23 kg. If we surround the U-235 ball with a berylium
neutron reflector the critical mass is reduced to 20 kg. If we surround a ball of plutonium 239 with a neutron reflector made of U-238, the critical mass is reduced to 10 kg of Pu239.
If we surround the plutonium core with a berylium neutron reflector the critical mass is reduced to 6.82 kg of Pu239. If the core of fissionable fuel is for example: only 90% pure then the above critical masses must be actually multiplied by 1.1.
Also if we increase the density of the fissionable material by a factor of two this will assemble the equivelent of 4 critical masses of fissionable material. This is how the implosion method of detonating an A-bomb converts its atomic core or (pit) into a super critical mass. In the implosion method of detonating an Atomic bomb , a hollow sphere of U-235 or Pu-239 is placed inside of a hollow spherical tamper made of U-238. berylium 9 , or tungsten carbide, which is then placed inside a hollow spherical metal pusher. A neutron source can also be placed inside the hollow sphere of fissionable material if a solid core christy device design is used. The origional Fat Man A-bomb of 1945 used a solid core christy device design.
The concentric hollow spheres discussed above make up the pit. Then the pit is placed inside of the center of a hollow sphere of high explosive . This explosive hollow sphere is made of a castable explosive such as TNT ,or a plastic bonded high explosive such as C-4 plastic explosive. To improve implosion efficiency the explosive hollow sphere may be made of a combination of both the slowest, and fastest detonating chemical high explosives.
A hollow sphere of castable high explosive can be made of one hollow steel sphere , that is filled with Liquid TNT or liquid preperation B. After half of the liquid castable explosive has be been poured and has nearly hardened the pit may be inserted through a polar service cap on top of the hollow sphere of steel.
Then the rest of the explosive is inserted, the cap is sealed,
and the explosive then hardens into a hollow sphere around the pit. This will create a spherical high explosive shaped charge in which the hollow steel sphere serves as a spherical lense that will reflect 100 % of the shock waves created by the detonation of the high explosive onto the pit at the center of the hollow sphere.
The behavior of all the kinds of waves that exist in the universe, are governed by the same universal physical laws. The laws of physics that govern the behavior of all waves , allow us to know exactly how to shape, focus , and control the shock waves that
are created by the detonation of any configuration of high explosives. All high explosive lenses use curved parabolic, conical or spherical wave reflectors to focus all of their shock waves to their focal point. High explosive lenses are often called high explosive shaped charges. There are spherical, conical, tetragonal, hexagonal, octagonal, cutting, and scissors type high explosive lenses et el .To learn more about this look up , and read about shaped high explosive charges. Also look up, and read about high explosives.
There are up to 100 symmetrical high explosive detonators placed on the outer surface of the hollow steel sphere. They are wired into series circuits. These detonators are exploded simultaneously by a pulsed electric current of high amperage. This results in the simultaneous detonation of 100 % of the hollow sphere of high explosive. The hollow sphere of steel then serves as a spherical mirror that reflects the shockwaves to it's focus which is the atomic pit at its center.
In this way the hollow sphere of steel actually serves as a spherical high explosive lense. The diameter of the hollow spherical assembly of high explosives may be from 18 inches to
up to 60 inches which is 152.4 cm. In order to achieve at least
a two fold increase in the density of the atomic pit, the mass
of the high explosive sphere should be at least six times the mass of the amount of of U-235, or Pu239 that is actualy used in the pit. The mass of the high explosive sphere should not exceed 60 times the mass of the fissionable fuel used in the pit.
A two fold increase in the density of the atomic pit will tend to result in a 10-20 kiloton atomic explosion. A 3 fold compression may produce a 40-45 kiloton atomic yield, a four fold compression
may produce a 60-80 kiloton atomic yield , and a five fold compression of the pit which is very hard to get, may produce an 80 - 100 kiloton atomic yield. Getting a 5 fold compression of the pit requires a very strong, massive , and very efficient ,
lense implosion system.
The degree of compression, and thus density increase achieved by
the lense implosion system has a direct effect on the atomic yield , of an A-bomb . Pure fission yields from Implosion type A-bombs, with out using fusion neutron boosting rarely exceed 100,000 tons of TNT equivelent . The atomic yield for a weak lense implosion system can be as low as 100 tons of TNT equivelent,
or even less. The atomic yield for a strong, and good lens implosion system can be as high as 100,000 or even 150,000 tons of TNT equivelent.
The basic, primative, and rudimentary versions of these implosion type atomic weapon designs tend to result in large, massive weapons like the origional 10,200, pound fat man A-bomb of 1945 . For this reason primative implosion type nuclear devices are in fact useful only to moderately developed mid 20 th century style industrial nation states . There are however, modern , and advanced implosion type atomic weapon designs, that are only 5% or 10 % of the size , and mass, of devices like the Fat Man A-bomb of 1945.The arsenals of
most modern nuclear weapon states are dominated by such low mass, and compact modern nuclear weapon designs. Since the late 1950s almost all nuclear weapon test , have been done for the purpose of producing, smaller,more efficient, and more lite weight nuclear weapons.
The United States ceased live fire under ground nuclear
weapons tests in the year 1994. Now, highly sophisticated computer simulations, and computerized mathemathical models of weapon physics are used to evalute nuclear weapon designs.These computer models are called nuclear codes. These models, and codes have been compiled from 50 years of data, and calculations that were obtained from live nuclear weapon tests. The united States has conducted more 1400 live nuclear weapon tests underground, underwater, in the atmosphere, and in space since the first test (Trinity )on July 16,1945 near Alamogardo, New Mexico.
Alternatively the hollow sphere of high explosive used to trigger Implosion type A-bombs can be constructed by assembling three layers , of overlapping high explosive charges, around the pit. Each of these specially shaped high explosive charges will be a curved parabolic segment that will serve as a high explosive lense, by reflecting its shock waves to its central focus. Each shock wave from each explosive segment will have a point of convergence with the other high explosive shock waves.
In order to prevent premature dis-assembly of the pit by the sqeezing, and jetting of the pit through the points at which the shock waves converge it is neccessary for the shock waves of the second high explosive layer to overlapp and reinforce the shock waves of the first layer at the 1st layer shock wave convergence points.
Then the shock waves of the third and last layer of explosive charges will overlapp and reinforce the shock waves of the second layer at its shock wave convergence points. This allows all the individual shock waves to be merged into one perfect ingoing spherical implosion wave. This implosion wave compresses the pit and thus increases its density by forcfully pushing its atoms closer to each other for a microsecond or so. This renders the pit supercritical , and results in an atomic explosion that could be be eqaul to force of the detonation of 20,000 tons of TNT or more.
Alternatively a hollow sphere of fissionable material that contains a spherical vacume cavity inside of it may be used as the pit in an implosion type A-bomb . A gram or so of tritium gas can be inserted inside the vacume cavity to achieve fusion neutron boosting if this is desired when the A-bomb is detonated.. Many modern atomic weapons use hollow core pits, and fusion neutron boosted hollow core pits.
The conclusion :
Look at the articles about the effects of nuclear explosions to learn more about the actual results of an atomic explosion. Look at the H-bomb articles to learn more about thermonuclear weapons designs, and principles. In addition to their military uses nuclear weapons also have some peaceful uses. Look up the Orion project, and look up the Plow share project * . Also look up the use of nuclear weapons to deflect asteroids, and comets, that might other wise destroy almost all life on earth if they hit it. This has already happened at least one time in the geologic history of the earth. An asteroid or comet impact caused the mass extinction of life on earth at the end of the Cretacous period in Geologic time. The point of impact was at Chixielube in the ocean near the Yucatan penninsula of present day Mexico.
The Orion Project, and the Plow Share Project
From 1958 to 1965 The U. S government ran a project to design a nuclear bomb powered nuclear pulse rocket called Orion for carrying large massive crewed spacecraft on fast journeys to the
9 planets of the solar system . This was called the Orion project . The system would have worked by exploding small 1 kiloton - 20 kiloton yield A-bombs behind a massive metal inertial plate backed by massive pneumonic springs. Look up
the Orion project to learn more about it.*
From 1958 to 1973 the U. S government also ran another related project called the Plow Share project. The purpose of the plow share project was to use peaceful nuclear explosions for moving , and lifting enormus amounts of earth and rock during construction projects such building reservoirs, and so on. Look up the plowshare project to learn more about it. *
Orion was determined to be very feasible, very economical,
and very practical for its intended purpose.It could have traveled between the planets of the solar system on round trips at velocities of up to a million miles per hour or more with payloads of thousands, or even millions of metric tons while carrying a human crew in comfort, and luxury after the style of an ocean liner .
An interstellar version of orion was designed in the 1960s that was propelled by exploding 1 - 10 megaton range hydrogen bombs behind its inertial plate to to propell an Orion thermonuclear pulse rocket. The interstellar version of the Orion design is known as the Orion thermonuclear Starship.
Some versions of the Orion thermonuclear pulse rocket propelled star ship design are capable of accelerating a payload of thousands or millions of metric tons to a velocity of from 5% to 10 % of the speed of light. An orion starship could thus carry a crew of hundreds or perhaps thousands of humans to a nearby star system within 10 light years of the solar system with a maximium flight time of 100 years. Orion starships are also very feasible, practical, and economical. At this time there are more then 100,000 nuclear weapons stock piled on the planet earth . These were the result of the U. S / Soviet cold war. Plutonium 239 has a half life of 24,000 years, and Uranium 235 has a half life of up to 250,000 years. Instead of trying to store our nuclear weapon pits for 10s of thousands , and 100s of thousands of years to come on earth, we should revive the Orion project , and use the nuclear weapon stock piles of the world as fuel for interplanetary atomic Orion rockets, and interstellar
thermonuclear Orion rockets.
In the year 1965 The U. S congress canceled funding for the Orion
nuclear bomb pulse propulsion project because of widespread political opposition to it. It was very probably an extremely, foolish , stupid , short sited , and unwise decision for congress to cancel the Orion project in 1965. We need to beat our nuclear swords (nuclear weapons), that we made for fighting an atomic war ,or thermonuclear war of apocalypse into peaceful nuclear plow shares.
Reviving the Orion project may be best, and most productive way to do this. With Orions we can build a true space faring solar system wide civilization. We can even travel to the planets of other
stars within 10 light years of the solar system and colonize them within a maximium of 100 years of flight time using multi-generational Orion thermonuclear starships that can accelerate up to 10 % of the velocity of light, and thus achieve interstellar space flight.
Some versions of the Orion Star Ship design can achieve only
3 % or 4% of light velocity , but other versions of the Orion StarShip can go faster.Look up the Orion starship, and learn more about it. Also look up the related Deadalas fusion microexplosion nuclear pulse rocket project.*
Sources
The information in this article is drawn from many sources : including but not limited to the following sources.
- Smith atomic weapons report to U. S . Congress, and United Nations 1946-1947.
- Los Alamos Primer 1943.
- Encylopedia Brittanica article on nuclear weapons.
- Posted Historys of U.S nuclear weapons development on internet 1945 - 1993
- The summary of the published history, and records of the Manhattan Project as published by Los Alamos laboratory 1967.
- Nuclear weapons archive on internet.
See also
External links and references
- Nuclear Weapons Frequently Asked Questions (http://www.nuclearweaponarchive.org/Nwfaq/Nfaq0.html)