Firestorm - Nuclear Weapon Induced City Firestorms in Modern Cities

Nuclear Weapon Induced City Firestorms in Modern Cities

Unlike the highly combustible WWII cities that firestormed, from conventional and nuclear weapons, fire experts suggest that due to the nature of modern U.S. city design and construction, a firestorm is unlikely to occur after a nuclear detonation. The explanation for this is that fire storms are not likely in areas where buildings have been totally collapsed. and more importantly there is a sizable difference between the fuel loading of WWII cities that firestormed, including Hiroshima, and that of modern cities, were the quantity of combustibles per square meter in the fire area in the latter is below the necessary requirement of 40 kg of combustibles per square meter for a firestorm to form. Therefore firestorms are not to be expected in modern US or Canadian cities, following a nuclear detonation, nor are they to be likely in modern European cities.

Similarly one reason for the lack of success in creating a true firestorm in the Bombing of Berlin in World War II was that the building density, or builtupness factor in Berlin was too low to support easy fire spread from building to building. Another reason was that much of the building construction was newer and better than in most of the old German city centers. Modern building practices in the Berlin of WWII led to more effective firewalls and fire resistant construction. Mass firestorms never proved to be possible in Berlin. No matter how heavy the raid or what kinds of firebombs were dropped, no true firestorm ever developed.

The incendiary effects of a nuclear explosion do not present any especially characteristic features. In principle, the same overall result, as regards destruction by fire and blast, can be achieved by the use of conventional incendiary and high-explosive bombs. It has been estimated for example that the fire damage suffered at Hiroshima after the dropping of the ~16 kiloton Little Boy nuclear weapon could have been produced by about 1 kiloton/1000 tons of incendiary bombs distributed over the city. It may appear counterintuitive that the same amount of fire damage caused by a nuclear weapon could have instead been produced by a smaller total yield of conventional incendiary bombs, however WWII experience supports this assertion. A greater area of fire damage resulted after the conventional Bombing of Dresden in World War II where in total ~ 4.5 kilotons of conventional American ordnance was dropped over many nights and this resulted in 15 square miles (39 km2) of the city being destroyed by fire and firestorm effects. Whereas after the Atomic bombing of Hiroshima where a single 16 kiloton nuclear weapon was dropped yet a relatively smaller area of only 4.5 square miles (12 km2) of the city was destroyed. Similarly Major Cortez F. Enloe, a surgeon in the USAAF who worked on the United States Strategic Bombing Survey (USSBS), said that the atomic bomb dropped on Nagasaki did not do as much fire damage as the extended conventional airstrikes on Hamburg.

This break from the linear expectation of more fire damage to occur after greater explosive yield is dropped can be easily explained by noticing that the order of blast and thermal events during a nuclear explosion are not ideal for the creation of fires. In a conventional incendiary bombing raid, incendiary weapons followed after high explosive blast weapons were dropped, in a manner designed to create the greatest probability of fires from a limited quantity of explosive and incendiary weapons. The so-called two-ton "cookies", also known as "blockbusters," were dropped first and were intended to rupture water mains, and blow off roofs, doors, and windows, creating an air flow that would feed the fires caused by the incendiaries that would then follow and be dropped, ideally, finding their way into holes created by the prior blast weapons, that is, into attic and roof spaces etc. On the other hand nuclear weapons produce effects that are in the reverse order, with thermal effects, 'flash' occurring first, which is then followed by the slower blast wave. It is for this reason that conventional incendiary bombing raids are considered to be a great deal more efficient at causing mass fires than Nuclear weapons of comparable yield. It is likely that this fact led the Nuclear weapon effects experts Samuel Glasstone and Philip J. Dolan to state that the same fire damage suffered at Hiroshima could have been produced by only about 1 kiloton/1000 tons of incendiary bombs.