NUCLEAR WEAPON EFFECTS IN SPACE
When a nuclear weapon is detonated close to the Earth's surface the density of the air is sufficient to attenuate nuclear radiation (neutrons and gamma rays) to such a degree that the effects of these radiations are generally less important than the effects of blast and thermal radiation. The relative magnitudes of blast, thermal and nuclear radiation effects are shown in figure 1 for a nominal fission weapon (20 kilotons) at sea level.1
The solid portions of the three curves correspond to significant levels of blast, thermal, and nuclear radiation intensities. Blast overpressures of the order of 4 to 10 pounds per square inch will destroy most structures. Thermal intensities of the order of 4 to 10 calories per square centimeter will produce severe burns to exposed persons. Nuclear radiation dosages in the range 500 to 5,000 roentgens are required to produce death or quick incapacitation in humans.
1 The Effect of Nuclear Weapons, U. S. Department of Defense, published by the Atomic Energy Commission, June 1957.
First, in the absence of an atmosphere, blast disappears completely.
Second, thermal radiation, as usually defined, also disappears. There is no longer any air for the blast wave to heat and much higher frequency radiation is emitted from the weapon itself.
Figure 2 shows the dosage-distance relationship for a 20-kiloton explosion when the burst takes place at sea level and when the burst takes place in space. We see that in the range 500 to 5,000 roentgens the space radii are of the order of 8 to 17 times as large as the sea-level radii. At lower dosages the difference between the two cases becomes even larger.
The visual displays were accompanied by disruptive effects on radio communications. Specifically, most commercial communication systems operating on the high-frequency (about 5 to 25 megacycles) bands in the Pacific noted substantial disturbances. Most links within a few hundred miles of Johnston Island experienced "outages" for as long as several hours, at various times over a period of about a day. In general, the effects on high-frequency communication links appear to have been quite similar to the effects produced by giant solar flares.
2 Note to Editors and Correspondents, U. S. Atomic Energy Commission, Department of Defense, Joint Office of Test Information, August 1, 1958
3 Note to Editors and Correspondents, U. S. Atomic Energy Commission, Department of Defense, Joint Office of Test Information, August 12, 1958.
4 Atomic-Like Flash Seen Here-Nuclear Rocket Test Indicated, The Honolulu Advertiser, August 1, 1958.
5 Samoa Bulletin, August 1, 1958.
6 Samoa Bulletin August 15. 1958.
7 Cullington, A Man-Made or Artificial Aurora, Nature, vol. 182, No. 4646, November 15, 1958, p. 1365.
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