Background and Overview
The advantage of being a nuclear power is derived from the massive amount of destruction that can be wrought with a ludicrously low number of weapons in a very short time span, and from the fact that once released, there is no system or armor in existence that can successfully defend against them. And so, during the Cold War, nuclear powers held each other hostage. Large numbers of nuclear weapons were aimed at one another to ensure destruction of the enemy, the enemy’s nuclear weapons, and so on. But with the end of the Cold War, such concerns faded. However, in light of North Korea’s recent nuclear test, the specter of a nuclear attack by a hostile nation has once again been catapulted to the forefront of the national consciousness. Although the test weapon likely “fizzled” and failed to fully detonate, even the relatively small 4-kiloton yield that North Korea had intended could have devastating effects. For comparison, the first nuclear weapons detonated by nuclear powers generally fall in the 15 kiloton range because smaller weapons are more difficult to produce (1). It is also important to bear in mind the fact that while the detonation of kilotons of TNT would produce a similar apparent explosion, nuclear weapons also produce a plethora of side effects due to the radioactive materials required. Nuclear weapons can contaminate a detonation site and create clouds of radioactive fallout that can be carried by wind and water.
Nuclear detonations can be varied by altitude to alter the effects. As a result, they are grouped into four general categories: air bursts, surface bursts, subsurface bursts, and high altitude bursts. Air bursts detonate in midair at a height below 30 kilometers, but still high enough to prevent the fireball from reaching the ground. Within these parameters, air bursts can be further altered to tailor the blast effects as required. Air bursts are considered useful for tactical purposes due to the fact that they produce relatively little fallout, and are thus unlikely to contaminate the detonation site. Only a small area near ground zero would pose a threat to advancing armies.
Surface bursts detonate near or on the ground, reducing the radius of the blast and thermal effects, but focusing those effects onto the smaller area. While the initial radiation emitted by surface bursts will be lessened, the fallout produced will be much more dangerous and will contaminate a much larger area.
Subsurface bursts involve detonating a weapon below ground or underwater. Subsurface bursts that fail to penetrate the surface of the medium will devastate local areas through shockwaves propagating through the ground or water. Subsurface bursts that do penetrate the surface will present lessened initial detonation effects, but fallout in the region will be comparatively heavy.
Finally, high altitude bursts occur above 30 kilometers in altitude. At this altitude, the lower air pressure allows the fireball to expand very rapidly to a much greater size than for other bursts. The radiation emitted by the burst will have a far greater range. The resulting “electromagnetic pulse” (EMP) is capable of destroying unshielded electronic equipment (2). Fallout is eliminated since no solid material is drawn up into the blast. As a result, this type of application has the potential to destroy an enemy’s capabilities without contaminating territory or massacring the inhabitants.
Blast Propagation
The energy produced in the nuclear reaction of the blast is partitioned in the following manner: 50% produces the blast energy, 35% forms the thermal energy, and the remaining 15% produces nuclear radiation. Of the 15% of energy producing nuclear radiation, one-third is released as the initial radiation dose of gamma rays and neutrons. The remaining energy is released as residual radiation causing the resulting fallout (2, 3).
The resulting blast effects occur with disorienting rapidity. The majority of the damage from a nuclear weapon results from the shockwave. The blast pushes the air into a compressed wall that radiates out from ground zero, crushing and tearing apart anything in its path. The wall of air destroys mainly large buildings, while the following winds generally destroy smaller objects and people. This “overpressure” effect can also rip material from the earth if the blast is close enough to the surface. A crater is produced at ground zero, and the material is sucked up into the air and returned later as radioactive fallout (4). As the fireball rises into the familiar mushroom cloud, however, a vacuum is generated. As a result, the blast wave reverses direction, subjecting the same areas to another wave of destruction from the opposite direction (2). The overpressure effects can be optimized for particular radii from ground zero by tailoring the altitude of a blast (4).
Thermal radiation is released simultaneously, but since the blast effects propagate at Mach 1, the thermal radiation, propagating at the speed of light, arrives at targets in the target area seconds before the overpressure wave. Those looking in the direction of the blast at the moment of detonation will be subjected to instant retinal burn, permanently destroying the section of the retina receiving the light. Others who receive a somewhat lower intensity will be subjected to “flashblindness”, a temporary condition lasting only a few minutes. For individuals closer to ground zero, the thermal radiation will cause burn injuries of varying degrees. Flammable materials may be directly ignited by the radiation (4). Since this energy is transported and transferred by the electromagnetic spectrum, some of the most peculiar damaging effects observed in nuclear detonations involve thermal radiation release. Burning occurs only on the sides of objects facing the explosion, and is subject to the varying light-absorption properties of the surface. Burn injuries may be patterned in the same way as the clothing worn by the individual (5).
The remaining energy released by the blast takes the form of an initial radiation dose. Whereas blast and thermal effects can be observed on a much smaller scale in conventional detonations, radiation release is a phenomenon limited to nuclear weaponry in modern weapons stocks. The range of intense radiation is limited, but the effects can be varied and difficult to predict for those caught within that range. Biological responses to the initial irradiation can range from rapid onset of radiation poisoning symptoms and death to normal development followed later by delayed effects (6). The range of delayed effects covers both mutagenic and carcinogenic consequences. Genetic damage may occur, with mutagenized genes passed to the children of survivors (7). The survivors who receive comparatively low doses of radiation may be further irradiated by the radioactive fallout that delivers the last of the energy produced by the detonation. Alternatively, the fallout may irradiate or contaminate areas far removed from ground zero if spread by prevailing winds, or even by runoff water from the blast area. Rain and other weather conditions may also concentrate fallout in particular areas. As a result, it is extremely difficult to formulate any predictions on the effects of the fallout. This is important to note since radioactive contamination by minute fallout particles can prevent recovery and reconstruction from occurring (4).
Detailed Scenario: Surface Burst at the Empire State Building
Location: New York City, NY
A surface burst opens up the potential for large amounts of radioactive fallout, focused blast effects within a reduced radius, and a reduced initial radiation dose. For this example, a 150 kiloton weapon will be detonated at the base of the Empire State Building in Manhattan. Ideal formulas will be used to estimate damage. To estimate the range of fallout, the scenario includes clear weather with a slight easterly breeze. In this scenario, the detonation is timed for noon on a business day. The population density is assumed to be about 125,000 individuals per square mile, and is idealized such that the density is uniform. One quarter of these individuals will be caught outdoors at the moment of the blast, perhaps on their way to or from lunch. The scenario is based on the New York City Scenario at Atomicarchive.com (8) and HYDESim projections (9).
Within one second of the detonation, a 20 pounds per square inch (psi) overpressure will be generated out to a distance of 0.4 miles from the Empire State Building. Everything in this circle is utterly demolished. Those within this circle will be exposed to sudden pressure effects that destroys lungs and ear drums, shrapnel from nearby objects, and a thermal emission of such intensity that immediate death results. Any possible survivors perish in the collapse of the buildings. At this point, 75,000 have died, and a fireball has reached its maximum radius of 0.2 miles. The blast and overpressure effects have already destroyed more than the fireball will. Mere seconds later, a 15 psi overpressure has been established out to 0.81 miles. All concrete buildings in this radius, reinforced or not, will be destroyed.
At 12:00:04, a 10 psi wall of air has struck out to a distance of 1 mile. At this range, some reinforced buildings may stay standing, but everything will be severely damaged. No usable buildings will remain. The thermal effects will still light fires at this range, but the following shock front will immediately extinguish those flames. Some 300,000 have died, and 100,000 have received some degree of injury. The Chrysler Building, Rockefeller Center, United Nations, and several hospitals will either be demolished or will need to be razed.
Two seconds later, a 5 psi shockwave has reached a range of 1.49 miles from the Empire State Building. Reinforced structures are still heavily damaged at this range. Of the 500,000 people included in this stage, those individuals unfortunate enough to have an unobstructed view of ground zero will be subjected to a thermal pulse still intense enough to kill. Those indoors will be injured by flying debris from shattered windows and the like. Roughly half may die. Flying debris will injure many outside, but tens of thousands of the fortunate will survive without injury for now. This area will be highly vulnerable to subsequent fires from damaged buildings and infrastructure. Broken gas lines will combine with ignition sources to start fires in a large number of structures.
By 12:00:10, the overpressure has reduced to 2 psi at a range of 2.61 miles. Structural damage is falling off, with some reinforced buildings at the outer edge of this ring receiving little or no damage. Perhaps 15% of the 525,000 people in this stage will be casualties. Unprotected individuals will be burned by the thermal pulse, and may still perish. The degree of injury will depend on the clothing of those outdoors. Dark clothing and colors will absorb the thermal radiation more readily, literally burning the pattern of the clothing into the skin of the wearer. The thermal radiation here will light fires, but the overpressure wave is unlikely to put out these flames. At this point, the detonation effects have reached New Jersey.
Finally, an overpressure of 1 psi reaches out to a blast radius of 3.85 miles only 16 seconds after detonation. Since much of this band occurs over water, the population is only 500,000 in this area. There will be few fatalities here, but some will be injured by the thermal radiation. Ordinary houses at this point may survive with light damage, but this is by no means the end to the deaths caused by damage to buildings. The blast will shatter windows at a range of nearly 10 miles from the Empire State Building, and these glass shards may kill or injure. Flashblindness and retinal damage are possible 20 miles out, although the number injured in this manner is much lower than for an air burst. Lower Manhattan from Central Park down has been crushed and set alight. Fallout fills the air over New York City.
The surface burst in Manhattan has thrown an extraordinary amount of particulate matter into the air. A crater centered on the former site of the Empire State Building has formed as a result. With an easterly breeze, the irradiated particles in the air will begin to fall in an elongated pattern. Some fallout will actually land upwind of ground zero. Fallout will concentrate enough to deliver 300 rems of radiation in an elliptical area from a point just southwest of ground zero all the way to just short of LaGuardia Airport. Enough fallout to deliver 100 rems will land from the Hudson River to far past LaGuardia. 100 rems and under will subject irradiated individuals to delayed effects, including possible genetic and chromosomal damage and a possible temporary reduction in white blood cells. Those with slightly higher exposures will suffer mild radiation sickness, and may perish from complications. The 300 rems delivered by fallout in the concentrated area delivers serious radiation sickness. 300 rems will kill between 35% and 70% of exposed individuals within 30 days. The others will suffer over the remainder of their lifetimes since the radiation dose has destroyed marrow and intestinal cells. For these individuals, hemorrhaging may also occur.
For this scenario, just less than 3,000,000 people will be involved directly. Perhaps some 830,000 would perish, and 875,000 would be injured. Aid efforts would be hampered by the large scale of the destruction. Much vital infrastructure would simply cease to exist. Many more people will die from lack of treatment or in subsequent fires. Chaos in the area would perhaps claim still more lives.
Final Note
The sheer horror of the above scenario was the basis for the Cold War concept of Mutually Assured Destruction (aptly shortened to MAD), in which stockpiling a massive amount of thermonuclear weaponry and depending upon the sanity of the enemy was the prevailing strategy. However, any informed head of state at the time faced stakes greater still than even those outlined above. The Detailed Scenario here was for a mere 150 kilotons. The largest weapon in service for the United States during the Cold War was capable of a staggering 25 megatons – 25,000 kilotons (10). A 25 megaton blast would produce the following overpressure effects alone: 15 psi at 4.47 miles, 5 psi at 8.22 miles, 2 psi at 14.39 miles, and 1 psi at 21.2 miles. Windows would shatter 111.41 miles away. The USSR once tested a 50 megaton weapon with a total potential yield of 100 megatons (11, 12). So although the nuclear threats most relevant today are horrifying, the sheer number and power of the nuclear weapons possible during a Cold War confrontation are difficult to even imagine. A nuclear exchange would likely have resulted in a nuclear winter that would have destroyed Earth’s ecosystem and may have lead to the extinction of humanity. This, coupled with the possibility of launching “salted” weapons designed to produce radioactive fallout with long half lives for the purpose of intentionally causing long-term contamination, may well have destroyed the majority of life on Earth. The legacy of these facts are the very ideas of MAD and nuclear deterrence – crude Cold War strategies that we still find necessary in a world very different from that of the Cold War. And so, today, much like in the past, the countdown to the launch of the first nuclear bomb of the first nuclear war seems very much to be the final countdown.
References
1. U.S. To Propose NK Sanctions (2006). Available at http://www.cnn.com/2006/WORLD/asiapcf/10/11/korea.nuclear.test/index.html (03 November 2006).
2. J. Pike, Nuclear Weapons Effects (2006). Available at http://www.globalsecurity.org/wmd/intro/nuke-effects.htm (03 November 2006).
3. The Energy from a Nuclear Weapon (2006). Available at http://www.atomicarchive.com/Effects/effects1.shtml (03 November 2006).
4. The Blast Wave (2006). Available at http://www.atomicarchive.com/Effects/effects2.shtml (03 November 2006).
5. Flash Burns (2006). Available at http://www.atomicarchive.com/Effects/effects12.shtml (03 November 2006).
6. J. Pike, Nuclear Weapon Radiation Effects (2006). Available at http://www.globalsecurity.org/wmd/intro/nuke-radiation.htm (03 November 2006).
7. Radiation’s Effects On Human Body Can Range From Nausea to Death (1999). Available at http://www.cnn.com/HEALTH/9909/30/radiation.sickness/ (03 November 2006).
8. Introduction: New York City Example (2006). Available at http://www.atomicarchive.com/Example/Example1.shtml (03 November 2006).
9. HYDESim: High-Yield Detonation Effects Simulator. Available at http://meyerweb.com/eric/tools/gmap/hydesim.html (03 November 2006).
10. Complete List of All U.S. Nuclear Weapons (2006). Available at http://nuclearweaponarchive.org/Usa/Weapons/Allbombs.html (03 November 2006).
112. The Tsar Bomba (“King of Bombs”) (2002). Available at http://www.nuclearweaponarchive.org/Russia/TsarBomba.html (03 November 2006).
12. The Most Powerful Bomb Ever Constructed (2006). Available at http://www.damninteresting.com/?p=214 (03 November 2006).