Checkmate detonation as seen from another camera
Above: following on from the first post on this blog, here is another view (looking almost directly upward from near ground zero) of Checkmate, a 7 kilotons burst at 147 km altitude over Johnston Island on 20 October 1962.
Dr Herman Hoerlin writes in Los Alamos National Laboratory report LA-6405, United States High Altitude Test Experiences, p. 1:
'The prompt thermal effects on the ground were negligible, with the exception of those from the Orange event [this 3.8 Mt burst at only 43 km altitude produced 3.0 cal/cm2 of thermal radiation at ground zero, whereas 3.8 Mt Teak at 77 km altitude only produced 1.0 cal/cm2 at ground zero, and all of the other high altitude detonations produced merely 0.1 cal/cm2 or less at ground zero]. 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 people looking in the direction of the explosion, with a clear view] 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 [eye retina] burns, however, due to inadvertent exposure [during the 410 kt Bluegill test at 48 km altitude]. ...
'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 [high altitude] explosions [Teak, Orange, and Starfish]. 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 Starfish event was unexpected; so were the damages sustained by three satellites in orbit [the Ariel, Traac, and Transit 4B satellites failed; Cosmos V, Injun I and Telstar suffered only minor degradation, moderate solar cell damage by electrons].
'However, the vast amount of knowledge gained by the observations of the artificial belts generated by Starfish, Argus, and the Russian high-altitude explosions [notice that America had data on the Russian tests back in 1976, when this report was written] far outweighed the information which would have been gained otherwise. A few extrapolations are made to effects on manned space flight under hypothetical circumstances[page 26 says: 'for a satellite in a polar circular earth orbit, the daily dose would have been at the very least 60 rads in a heavily shielded vehicle at Starfish time plus four months']. 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 prompt fallout from high-altitude explosions was zero. The residence time in the stratosphere of special tracers—Rh-102 and Cd-109—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.'
The burst altitudes and dates given in Table 1 of that report are useful in regard to current conflicting statements over the burst altitudes of Argus tests: three 1.7 kt weapons were detonated at altitudes of 200 km, 240 km, and 540 km, respectively, on 27 and 30 August and 6 September 1958. (These altitudes are taken from R. W. Klib's Mission Research Corporation reports about data from the tests, MRC-R-112 and -176, dated January 1974 and March 1975.)
Page 16 mentions that research with rhesus monkeys since the tests shows the approximate range at which it would have been safe to watch the 77 km altitude 3.8 Mt Teak nuclear test from the ground in exceptionally clear weather:
'irreversible [eye retina] damage occurs for a temperature increase of 20 °C, while a 5 °C temperature rise is safe. Applying these criteria to the Teak case, the threshold (20 °C) dose at ground zero would [be] 1 cal/cm2 on the retina and the safe dose 0.2 cal/cm2. Then, taking the postevent source data and assuming an exceptionally clear day, the safe slant distance would have been 450 statute miles.'