War planners ignore the fire effects of nuclear bombing

City on fire, Nuclear Darkness, by Lynne Eden, 30 Dec 19, By ignoring the fire damage that would result from a nuclear attack and taking into account blast damage alone, U.S. war planners were able to demand a far larger nuclear arsenal than necessary.

For more than 50 years, the U.S. Government has seriously underestimated damage from nuclear attacks. The earliest schemes to predict damage from atomic bombs, devised in 1947 and 1948, focused only on blast damage and ignored damage from fire, which can be far more devastating than blast effects.

The failure to include damage from fire in nuclear war plans continues today. Because fire damage has been ignored for the past half-century, high-level U.S. decision makers have been poorly informed, if informed at all, about the extent of damage that nuclear weapons would actually cause. As a result, any U.S. decision to use nuclear weapons almost certainly would be predicated on insufficient and misleading information. If nuclear weapons were used, the physical, social, and political effects could be far more destructive than anticipated.

How can this systematic failure to assess fire damage have persisted for more than half a century? The most common response is that fire damage from nuclear weapons is inherently less predictable than blast damage. This is untrue. Nuclear fire damage is just as predictable as blast damage.

One bomb, one city

To visualize the destructiveness of a nuclear bomb, imagine a powerful strategic nuclear weapon detonated above the Pentagon, a short distance from the center of Washington, D.C.1 Imagine it is a “near-surface” burst-about 1,500 feet above the ground-which is how a military planner might choose to wreak blast damage on a massive structure like the Pentagon. Let us say that it is an ordinary, clear day with visibility at 10 miles, and that the weapon’s explosive power is 300 kilotons-the approximate yield of most modern strategic nuclear weapons. This would be far more destructive than the 15-kilotonbomb detonated at Hiroshima or the 21-kiloton bomb detonated at Nagasaki.²

Washington, D.C., has long been a favorite hypothetical target.³ But a single bomb detonated over a capital city is probably not a realistic planning assumption.

When a former commander in chief of the U.S. Strategic Command read my scenario, he wanted to know why I put only one bomb on Washington. “We must have targeted Moscow with 400 weapons,” he said. He explained the military logic of planning a nuclear attack on Washington: “You’d put one on the White House, one on the Capitol, several on the Pentagon, several on National Airport, one on the CIA, I can think of 50 to a hundred targets right off. . . . I would be comfortable saying that there would be several dozens of weapons aimed at D.C.” Moreover, he said that even today, with fewer weapons, what makes sense would be a decapitating strike against those who command military forces. Today, he said, Washington is in no less danger than during the Cold War.

The discussion that follows greatly understates the damage that would occur in a concerted nuclear attack, and not only because I describe the effects of a single weapon. I describe what would happen to humans in the area, but I do not concentrate on injury, the tragedy of lives lost, or the unspeakable loss to the nation of its capital city. These are important. But I am concerned with how organizations estimate and underestimate nuclear weapons damage; thus, I focus largely, as do they, on the physical environment and on physical damage to structures.

With this in mind, let us look at some of the consequences of a nuclear weapon detonation, from the first fraction of a second to the utter destruction from blast and fire that would happen within several hours. This will allow us to understand the magnitude of the damage from both effects, but particularly from fire, which is neither widely understood nor accounted for in damage prediction in U.S. nuclear war plans.

Unimaginable lethality

The detonation of a 300-kiloton nuclear bomb would release an extraordinary amount of energy in an instant-about 300 trillion calories within about a millionth of a second. More than 95 percent of the energy initially released would be in the form of intense light. This light would be absorbed by the air around the weapon, superheating the air to very high temperatures and creating a ball of intense heat-a fireball.

Because this fireball would be so hot, it would expand rapidly. Almost all of the air that originally occupied the volume within and around the fireball would be compressed into a thin shell of superheated, glowing, high-pressure gas. This shell of gas would compress the surrounding air, forming a steeply fronted, luminous shockwave of enormous extent and power-the blast wave.

By the time the fireball approached its maximum size, it would be more than a mile in diameter. It would very briefly produce temperatures at its center of more than 200 million degrees Fahrenheit (about 100 million degrees Celsius)-about four to five times the temperature at the center of the sun.

This enormous release of light and heat would create an environment of almost unimaginable lethality. Vast amounts of thermal energy would ignite extensive fires over urban and suburban areas. In addition, the blast wave and high-speed winds would crush many structures and tear them apart. The blast wave would also boost the incidence and rate of fire-spread by exposing ignitable surfaces, releasing flammable materials, and dispersing burning materials.

Within minutes of a detonation, fire would be everywhere. Numerous fires and firebrands-burning materials that set more fires-would coalesce into a mass fire. (Scientists prefer this term to “firestorm,” but I will use them interchangeably here.) This fire would engulf tens of square miles and begin to heat enormous volumes of air that would rise, while cool air from the fire’s periphery would be pulled in. Within tens of minutes after the detonation, the pumping action from rising hot air would generate superheated ground winds of hurricane force, further intensifying the fire.⁴

Virtually no one in an area of about 40-65 square miles would survive.

A little farther away…….

Virtually no one in an area of about 40-65 square miles would survive.

A little farther away……

Three miles from ground zero……..

A hurricane of fire…..

….The first indicator of a mass fire would be strangely shifting ground winds of growing intensity near ground zero. (Such winds are entirely different from and unrelated to the earlier blast-wave winds that exert “drag pressure” on structures.) These fire-winds are a physical consequence of the rise of heated air over large areas of ground surface, much like a gigantic bonfire.

The inrushing winds would drive the flames from combusting buildings horizontally toward the ground, filling city streets with hot flames and firebrands, breaking in doors and windows, and causing the fire to jump hundreds of feet to swallow anything that was not yet violently combusting. These extraordinary winds would transform the targeted area into a huge hurricane of fire.

Within tens of minutes, everything within approximately 3.5 to 4.6 miles of the Pentagon would be engulfed in a mass fire. The fire would extinguish all life and destroy almost everything else.

Firestorm physics

This description of the physics of mass fire is based on the work of a few scientists who have examined in detail the damaging effects of nuclear weapons, including nuclear engineer Theodore A. Postol and physicist Harold Brode. Postol is one of the country’s leading non-government funded technical experts on nuclear weapons, missiles, and arms control. Brode’s five-decade career has been devoted to the study of nuclear weapons effects.

That mass fires have occurred, and that something like the firestorm described here could occur, is not in dispute. What is not widely accepted is that nuclear weapons detonated in urban or suburban areas would be virtually certain to set mass fires, and that the resulting damage is as predictable as blast damage. The much more widely held view is that the probability and range of mass fire depends on many unpredictable environmental variables, including rain, snow, humidity, temperature, time of year, visibility, and wind conditions.

But the work of Postol, Brode, and Brode’s collaborators shows that mass fire creates its own environment. Except in extreme cases, environmental factors do not affect the likelihood of mass fire. Weather can affect the fire’s range, but this can be reasonably well predicted. For nuclear weapons of approximately 100 kilotons or more, the range of destruction from mass fire will generally be substantially greater than from blast. The extraordinarily high air temperatures and wind speeds characteristic of a mass fire are the inevitable physical consequence of many simultaneous ignitions occurring over a vast area. The vacuum created by buoyantly rising air follows from the basic physics of combustion and fluid flow (hydro- or fluid dynamics). As the area of the fire increases, so does the volume of rising air over the fire zone, causing even more air to be sucked in from the periphery of the fire at increasingly higher speeds.

Only a few mass fires have occurred in human history: those created by British and U.S. conventional incendiary weapons and by U.S. atomic bombs in World War II. These include fires that destroyed Hamburg, Dresden, Kassel, Darmstadt, and Stuttgart in Germany, and Tokyo, Hiroshima, and Nagasaki in Japan. History’s first mass fire began on the night of July 27, 1943, in Hamburg-created by allied incendiary raids. Within 20 minutes, two thirds of the buildings within an area of 4.5 square miles were on fire. It took fewer than six hours for the fire to completely burn an area of more than five square miles. Damage analysts called it the “Dead City.” Wind speeds were of hurricane force; air temperatures were 400-500 degrees Fahrenheit. Between 60,000 and 100,000 people were killed in the attack.⁶

A mass fire from a modern nuclear bomb could be expected to destroy a considerably larger urban or suburban area, in a similarly short time.

The unique features of the mass fire fundamentally distinguish it from the more slowly propagating line fire. ……..

Fire environments created by mass fires are fundamentally more violent and destructive than smaller-scale fires, and they are far less affected by external weather conditions. They are not substantially altered by seasonal and daily weather conditions. …..

Average air temperatures in the burning areas after the attack would be well above the boiling point of water; winds generated by the fire would be hurricane force; and the fire would burn everywhere at this intensity for three to six hours. Even after the fire burned out, street pavement would be so hot that even tracked vehicles could not pass over it for days, and buried, unburned material from collapsed buildings could burst into flames if exposed to air even weeks after the fire.

Those who sought shelter in basements of strongly constructed buildings could be poisoned by carbon monoxide seeping in, or killed by the ovenlike conditions. Those who tried to escape through the streets would be incinerated by the hurricane-force winds laden with firebrands and flames. Even those able to find shelter in the lower-level sub-basements of massive buildings would likely die of eventual heat prostration, poisoning from fire-generated gases, or lack of water. The firestorm would eliminate all life in the fire zone.

All publication data from “Whole World on Fire” by Lynn Eden at Google Books http://www.nucleardarkness.org/web/cityonfire/