Although no other country has used such a weapon of mass destruction since World War II, experts say it would be even more catastrophic if a hydrogen bomb were to be dropped instead of an atomic one. Simply speaking, experts say a hydrogen bomb is the more advanced version of an atomic bomb. An atomic bomb uses either uranium or plutonium and relies on fission, a nuclear reaction in which a nucleus or an atom breaks apart into two pieces. To make a hydrogen bomb, one would still need uranium or plutonium as well as two other isotopes of hydrogen, called deuterium and tritium.
The hydrogen bomb relies on fusion, the process of taking two separate atoms and putting them together to form a third atom. In both cases, a significant amount of energy is released, which drives the explosion, experts say. However, more energy is released during the fusion process, which causes a bigger blast.
Morse said the atomic bombs dropped on Japan were each equivalent to just about 10, kilotons of TNT. Hydrogen bombs are also harder to produce but lighter in weight, meaning they could travel farther on top of a missile, according to experts. Both bombs are extremely lethal and have the power to kill people within seconds, as well as hours later due to radiation. This is the manner in which energy and material, emitted by the warhead at detonation, travel through the medium in which the blast occurs.
When the propagation of a payload is uniform in all directions, it is called isotropic. If not, it is called non-isotropic.
See figure For convenience of discussion, warheads will be classified into five major groups: blast including air and underwater burst , fragmentation, shaped charge, continuous rod, and special-purpose. When a high explosive detonates, it is converted almost instantly into a gas at very high pressure and temperature.
Under the pressure of the gases thus generated, the weapon case expands and breaks into fragments. The air surrounding the casing is compressed and a shock blast wave is transmitted into it.
The detonation characteristics of a few high explosives are presented in table Table It is followed by a much slower hundredths of a second decline to atmospheric pressure. This portion is known as the positive phase of the shock wave. The pressure continues to decline to subatmospheric pressure and then returns to normal. This portion is called the negative or suction phase. A pressure-time curve is shown in figure The durations of these two phases are referred to as the positive and negative durations.
The area under the pressure-time curve during the positive phase represents the positive impulse, and that during the negative phase, the nega- tive impulse. For a fixed-weight explosive, the peak pressure and positive impulse decrease with distance from the explosion.
This is due to the attentuation of the blast wave. The rate of attenuation is proportional to the rate of expansion of the volume of gases behind the blast wave. Blast attenuation is somewhat less than this in-side, approximately 16 charge radii from blast center.
It should also be noted that there will be fragmentation when the warhead casing ruptures. When a bomb is detonated at some distance above the ground, the reflected wave catches up to and combines with the original shock wave, called the incident wave, to form a third wave that has a nearly vertical front at ground level. This third wave is called a "Mach Wave" or "Mach Stem," and the point at which the three waves intersect is called the "Triple Point.
In the Mach Stem the incident wave is reinforced by the reflected wave, and both the peak pressure and impulse are at a maximum that is considerably higher than the peak pressure and impulse of the original shock wave at the same distance from the point of explosion. Using the phenomenon of Mach reflections, it is possible to increase considerably the radius of effectiveness of a bomb.
Of course, all nuclear warheads are blast warheads, and on most targets they would be detonated at altitude to make use of the Mach Stem effect. The mechanism of an under-water blast presents some interesting phenomena associated with a more dense medium than air.
An underwater explosion creates a cavity filled with high-pressure gas, which pushed the water out radially against the opposing external hydrostatic pressure. At the instant of explosion, a certain amount of gas is instantan-eously generated at high pressure and temperature, creating a bubble.
In addition, the heat causes a certain amount of water to vaporize, adding to the volume of the bubble. This action immediately begins to force the water in contact with the blast front in an outward direction. The potential energy initially possessed by the gas bubble by virtue of its pressure is thus gradually communicated to the water in the form of kinetic ener-gy.
The inertia of the water causes the bubble to overshoot the point at which its internal pressure is equal to the external pressure of the water. The bubble then becomes rarefied, and its radial motion is brought to rest. The external pressure now com-presses the rarefied bubble. Again, the equilibrium configura-tion is overshot, and since by hypothesis there has been no loss of energy, the bubble comes to rest at the same pressure and vol-ume as at the moment of explosion in practice, of course, energy is lost by acoustical and heat radiation.
The bubble of compressed gas then expands again, and the cycle is repeated. The result is a pulsating bubble of gas slow-ly rising to the surface, with each expansion of the bubble creating shock wave. This phen-omenon explains how an underwater explosion appears to be fol-lowed by other explosions. The time interval of the energy being returned to the bubble the period of pulsations varies with the intensity of the initial explosion.
The rapid expansion of the gas bubble formed by an explo-sion under water results in a shock wave being sent out through the water in all directions. The shock wave is similar in gener-al form to that in air, although if differs in detail. Just as in air, there is a sharp rise in overpressure at the shock front. However, in water, the peak overpressure does not fall off as rapidly with distance as it does in air.
Hence, the peak values in water are much higher than those at the same distance from an equal explosion in air. The velocity of sound in water is nearly one mile per second, almost five times as great as in air. Con-sequently, the duration of the shock wave developed is shorter than in air.
The close proximity of the upper and lower boundaries between which the shock wave is forced to travel water surface and ocean floor causes complex shock-wave patterns to occur as a result of reflection and rarefaction. Also, in addition to the initial shock wave that results from the initial gas bubble expansion, subsequent shock waves are produced by bubble pulsation. The pulsating shock wave is of lower magnitude and of longer duration than the initial shock wave. Another interesting phenomenon of an underwater blast is surface cutoff.
At the surface, the shock wave moving through the water meets a much less dense medium--air. As a result, a reflected wave is sent back into the water, but this is a rarefaction or suction wave.
At a point below the surface, the combination of the reflected suction wave with the direct incident wave produces a sharp decrease in the water shock pressure. This is surface cutoff. The variation of the shock overpressure with time after the explosion at a point underwater not too far from the surface is illustrated in figure After the lapse of a short interval, which is the time required for the shock wave to travel from the explosion to the given location, the overpressure rises suddenly due to the arrival of the shock front.
Then, for a period of time, the pressure decreases steadily, as in air. Soon thereafter, the arrival of the reflected suction wave from the surface causes the pressure to drop sharply, even below the normal hydrostatic pressure of the water. This negative pressure phase is of short duration and can result in decrease in the extent of damage sustained by the target. The time interval between the arrival of the direct shock wave at a particular location or target in the water and that of the cutoff, signaling the arrival of the reflected wave, depends upon the depth of burst, the depth of the target, and the distance from the burst point to the target.
It can generally be said that a depth bomb should be detonated at or below the target and that a target is less vulnerable near the surface. The study of ballistics, the science of the motion of projec-tiles, has contributed significantly to the design of frag-mentation warheads. Specifically, terminal ballistics studies attempt to determine the laws and conditions governing the vel-ocity and distribution of fragments, the sizes and shapes that result from bursting different containers, and the damage aspects of the bursting charge fragmentation.
The balance of available energy is used to create a shock front and blast effects. The fragments are pro-pelled at high velocity, and after a short distance they overtake and pass through the shock wave.
The rate at which the velocity of the shock front accompanying the blast decreases is generally much greater than the decrease in velocity of fragments, which occurs due to air friction.
Therefore, the advance of the shock front lags behind that of the fragments. The radius of effective fragment damage, although target dependent, thus exceeds consid-erably the radius of effective blast damage in an air burst. Herein lies the principle advantage of a fragment-ation payload: it can afford a greater miss distance and still remain effective because its attenuation is less. The velocity of the fragments can be looked at in two parts: a the initial velocity, and b the velocity as a function of distance from the origin.
Table illustrates the relationship between the charge-to-metal ratio and the initial velocities V 0 of the fragments, and table lists typical Gurney Constants. In this case cylinders of 5.
Notice that as the charge-to-metal ratio increases, the fragment velocity also increases. Thus, during flight through the air, the velocity of each fragment decays because of air resistance or drag. The fragment velocity decreases more rapidly with distance as the fragment weight decreases. For an assumed initial fragment velocity of 1, meters per second, a five-grain.
For determining the effectiveness of almost all fragmenting munitions, the sub-sonic trajectory of the fragments can be ignored. As a result, the density of fragments in a given direction varies inversely as the square of the distance from the weapon. The fragments of a warhead travel outward in a nearly perpendicular direction to the surface of its casing for a cylindrical warhead there is a 7- to degree lead angle.
Hence, every atomic bomb is a nuclear bomb, but every nuclear bomb is not an atomic bomb. Spotlight Blockchain a game changer for seed funding? Coronavirus outbreak Covaxin vaccine Cowin vaccine registration Coronavirus live news Corona cases today Covshield vaccine Sputnik V vaccine.
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