Duck and Cover (film) - Accuracy and Usefulness

Accuracy and Usefulness

There is controversy from some people regarding the actual usefulness of the film. Since it has no counterpart in any other country (although the British film Protect and Survive is a much more blunt take on the same theme), it is sometimes regarded as being a red scare political tool, to make children frightened of the Soviet Union and communism. Also often questioned is the film's scientific accuracy; whether or not the tactics shown in the film (such as ducking into a doorway, putting a newspaper over your head, and even just throwing yourself face down on the ground) would actually work.

While this (or any) tactic would be useless for someone at ground zero during a nuclear blast, it would be beneficial to the vast majority of people who are positioned away from the blast hypocenter: both the thermal pulse of some weapons and shrapnel from all weapons (particularly from shattered windows) could be evaded. In particular, higher yield thermonuclear weapons have thermal pulses which last for several seconds. By promptly putting something between yourself and the fireball during these crucial couple of seconds, you could avoid or reduce the severity of the burns you would have otherwise received. For those not at ground zero, like the delay between lightning and thunder, there would be a delay between the flash (indicating the need to duck and cover) and the arrival of the blast wave, which will shatter windows turning non safety glass into shards of sharp missiles, and cause other blast or impact injuries.

To highlight the effect that being indoors can make, despite the lethal radiation & blast zone extending well past her position at Hiroshima, Akiko Takakura survived the effects of a 16 kt atomic bomb at a distance of 300 meters from the hypocenter, with only minor injuries, due in most part to her position of residing in the lobby of the bank of Japan, a reinforced concrete building, at the time of the Nuclear explosion. In contrast, the unknown person sitting outside, fully exposed, on the steps of the Sumitomo bank, next door to the bank of Japan, received lethal third degree burns and was then likely killed by the blast, in that order, within 2 seconds.

The advice to cover one's head with anything available, like the picnic blanket and newspaper used by the family in the film, may seem absurd at first when one considers the capabilities of a nuclear weapon, but even a thin barrier such as cloth can reduce the severity of burns on the skin from the thermal radiation - which is light rays in the ultraviolet, visible, and infrared range, and it is this combination of light rays that delivers the burning energy to exposed skin areas this burning thermal energy would be experienced by people within range for several seconds after the explosion. A photograph taken about 1.3 km from the epicenter of the Hiroshima bomb explosion showed that even leaves from a nearby shrub protected a wooden telephone pole from charring discoloration due to thermal radiation, while the rest of the telephone pole not under the protection of the leaves was charred almost completely black.

Depending on the yield and distance from the explosion the burst of ionising radiation from the fireball would arrive at an observer's position at the same time as the light flash, leaving the observer little to no time to find cover from this aspect of a nuclear detonation, but subsequently some of this radiation is absorbed and re-emitted by heated fireball air molecules at lower wavelengths, so harmful ionising radiation may continue for up to a minute during which time ducking and covering would go some way in limiting ones exposure).

One of the most common criticisms of Duck and Cover encountered is the opinion that prompt ionising radiation effects would still kill those who Duck and Cover, regardless of any preventive measures taken. However this is generally incorrect when any nuclear weapon more powerful than 10-30 kilotons is detonated, and even in that case, if the person is indoors the absorbed radiation dose is again not life threatening. For example, despite the film not being made in the era of megaton range weapons, for exposed individuals taking no preventive countermeasures the range of harmful ionising radiation effects stays within a circle of radius 2–3 km from ground zero during airbursts of 1 megaton in yield, yet the blast range that would be expected to be lethal to 50% of people is 7.5 km, and the range of thermal effects lethal to 50% of people stretching out to 11 km from ground zero. Naturally within this 3 km range from a 1 megaton airburst the fatality rate would be near total for those caught in the open from the extreme blast pressure alone, before any potential radiation sickness can begin.

However for one caught in the open outside this 3 kilometer radius from ground zero from a 1 megaton weapon, Ducking and Covering would drastically increase one's chance of survival, as at this range the radiation hazard is near zero whereas that from the blast is a chance of 50% fatality at a ~7.5 km range and that of thermal effects 11 km.

For one caught in the open, and by surprise, by the same 1 megaton weapon detonation, but one ducked and covered in 2 seconds time from first noticing the moment of flash, then one would have prevented themselves from being exposed to the full brunt of the 1 megaton explosions thermal energy, instead, approximately 55% of the explosions total thermal flash energy would have been absorbed over these 2 seconds In this example, as there is now a 45% reduction in the amount of heat experienced by one ducking and covering, the 50% lethal thermal range from this 1 megaton weapon can now be more accurately equated to equivalent to the entire flash energy from a 0.55 Mt or 550 kt weapon, if one ducks and covers in 2 seconds, and no longer treated as a 1 megaton weapon.

Henceforth ones chance of survival at 11 km goes from the previous 50% chance of death if they just stood there, gazing at the 1 megaton fireball as it emits all its energy over tens of seconds, to now a mere sunburn, or a 1st degree burn injury on exposed skin. With the 50% lethal thermal range being thus downrated to being equivalent to a 550 kt explosion, the 50% lethal thermal radius goes from the previous 11 km without ducking and convering to ~7 km with prompt duck and covering within 2 seconds. One can think of this as going from a scenario were before the majority of people caught in the open, who just stood there staring at the fireball out to a radius of 11 km would probably die from lethal 3rd degree burns on their unclothed skin, to a scenario now were instead the vast majority of people who 'duck and cover' from 7 km out to 11 km would remain alive, with generally non life threatening 1st degree burns & 2nd degree burns over their exposed skin, with the burn severity naturally depending on their range from the explosion.

Finally, it must be noted that all the lethal ranges given in the referenced graphs, and when discussing the range of Effects of nuclear explosions in general, one must keep in mind what is presented is the most pessimistic of weapon effects ranges. As the scaling laws these tables and graphs were derived from assume a simplistic flat terrain with no intervening skyscrapers or other objects that would attenuate the blast and provide shadowing from the thermal effects. When real world city terrain topography is included in these weapon effects calculations the lethal ranges are downgraded considerably.

According to the 1946 book Hiroshima, in the days between the Hiroshima and Nagasaki atomic bombs in Japan, one Hiroshima policeman went to Nagasaki to teach police about ducking after the atomic flash. As a result of this timely warning, not a single Nagasaki policeman died in the initial blast. This allowed more surviving Nagasaki police to organize relief efforts than in Hiroshima. Unfortunately, the general population was not warned of the heat/blast danger following an atomic flash because of the bomb’s unknown nature. Many people in Hiroshima and Nagasaki died while searching the skies for the source of the brilliant flash.

Recent scientific analysis has largely supported the general idea of sheltering indoors in response to a nuclear explosion Staying indoors can offer protection both from the initial blast as well as the radioactive fallout that accumulates during the aftermath. Additionally, such a response would leave roads clear for emergency vehicles to access the area.

Historians have generally sought to dismiss civil defense advice as mere propaganda. This is despite detailed scientific research programmes laying behind the much-mocked UK government civil defence pamphlets of the 1950s and 1960s, including the advice to promptly duck and cover. The advice to duck and cover has made a resurgence in recent years with new scientific evidence to support it.