United States High-altitude Test Experiences
A Review Emphasizing the Impact on the Environment
A LASL MONOGRAPH by Herman Hoerlin
The US high-altitude nuclear explosions of the 1955-1962 period are listed chronologically; dates, locations, and yields are given. The major physical phases of the interactions of the weapon outputs with the atmosphere are described, such as the formation of fweballs at the low high-altitudes and the partition of energies and their distribution over very large spaces at the higher high-altitudes. The effects of these explosions on the normal activities of populations and the protective measures taken are documented. Many scientific observations, together with their significance and values, are reviewed.
The prompt thermal effects on the ground were negligible, with the exception of those from the Orange event. That event could have caused minor damage in the Johnston Island (JI) area in the absence of cloud cover. The eyeburn problem at ground zero and up to large slant distances was severe for all events except Starfish, Checkmate, and Argus. Adequate precautions, such as the selection of JI instead of Bikini as the base in the Pacific, were taken. Two military personnel suffered severe burns, however, due to inadvertent exposure. Their case histories are recorded.
The degrading effects of increased ionospheric ionization on commercial and aircraft communications-mainly in the LF, MF, and HF frequency ranges — extended over the whole Pacific Ocean area. They lasted for many days after the three megaton-range explosions. They were less severe — in some cases even beneficial-for VHF and VLF frequencies, thus providing guidance for emergency situations.
The formation of an artificial radiation belt of such high electron fluxes and long lifetimes as occurred after the Startlsh event was unexpected; so were the damages sustained by three satellites in orbit. However, the vast amount of knowledge gained by the observations of the artificial belts generated by Starfish, Argus, and the Russian high-altitude explosions far outweighed the information which would have been gained otherwise. A few extrapolations are made to effects on manned space flight under hypothetical circumstances.
Electromagnetic radiation in the radio-frequency portion of the spectrum (EMP) caused brief outages of a street lighting system in Oahu and of several input stages of electronic equipment, though during the Starfish event only.
The worldwide auroral phenomena produced by the high-yield explosions were spectacular but of no consequence to ordinary human activities. They increased substantially our basic knowledge of auroral-type light-producing processes. Questions were raised but not answered as to the effects of pertinent energy depositions on large-scale weather patterns.
The prompt fallout from high-altitude explosions was zero. The residence time in the stratosphere of special tracers — '02Rh' and 'Cd' — incorporated into the Orange and Starfish devices was 14 years. The fallout of fission products was similarly delayed and was distributed over the whole globe; thus, the biological effects on humans were reduced per unit energy release in comparison with low-altitude atmospheric explosions. The worldwide observation of the tracers led to the development of matching models of global stratospheric air-mass motions and to a better understanding of mixing processes near the tropopause. In fact, the downward motion of the tracers was most pronounced in the polar areas during local winter. No effect on the natural ozone layer could be ascertained.
In summary, the effects of the US high-altitude explosions on the normal activities of the populations were either insignificant or under protective control involving little harassment or irritation. As to the effects on the research activities of the international scientific community, I believe, in retrospect, that the early apprehension both in the US and Great Britain has given way now to a more positive assessment of the scientific returns obtained. However, it is also evident that the consequences of massive military operations in the upper atmosphere would be grave.