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Light, Heat and Blast
Light and Heat
A nuclear explosion produces a blaze of light brighter than the sun, which lasts for about 15 seconds. Temporary blindness and eye injury can result from the glare if eyes are not shielded. The heat rays from the explosion travel at the speed of light or about 186,000 miles per second. It can start fires up to 20 miles away.
The following are some examples of the predictable effects on unprotected skin of the heat flash of a 5-megaton weapon exploded on a clear day:
- Skin is badly burned up to 15 miles from the explosion.
- Skin is blistered up to 18 miles from the explosion.
- Sunburn types of burns up to 23 miles from the explosion.
Nuclear explosions in the air rather than on the ground are more likely to produce a greater number of serious burns through the heat flash. Clothing will give some protection. A shield between you and the light will give protection against burns from the heat flash.
Blast
The blast wave travels more slowly than the heat flash. Several seconds may pass after you have seen the light or felt the heat before the blast wave reaches you, depending on the distance you are from the explosion. It is like the time between seeing the flash of lightning and hearing the sound of thunder. For example, at ten miles from the center of an explosion, it would take about 35 seconds for the blast wave to reach you. If caught in the open during a nuclear explosion, this time can be used to find some protection from the blast wave.
You will be injured by being thrown about by the blast; therefore, keep low. The greatest danger is from flying glass, bricks and other debris. The blast from a 5-megaton explosion could injure people as far away as 15 miles.
The kinds of damage that the blast can do to buildings are:
- Complete destruction of all buildings three miles from the center of the explosion.
- Damage beyond repair to buildings three to five miles distant. They would have to be torn down.
- Major repairs required to buildings five to 10 miles distant before they could be occupied.
- Light to moderate damage to buildings 10 to 15 miles distant. They could be occupied during repairs.
A 20-megaton bomb increases the approximate ranges of damage described above to five, eight, sixteen and twenty-four miles. These are approximate distances as the strength of buildings is not uniform.
Reinforced concrete buildings are more blast resistant than wood frame structures. In some areas four miles away from the explosion, concrete buildings might be repairable, while wood frame buildings would be completely destroyed. Windows, of course, are very vulnerable and are apt to be blown in as far away as 25 miles from the explosion.
Radiation
A nuclear explosion causes both