AFOAT- 2 discovered USSR's first A-bomb was US Mark VI3859 Reads  

Shortly after the end of WWII the US Air force established a group called AFOAT-ONE that flew regular air sampling flights around the periphery of the Soviet Union. I understand their mission was to pinpoint the site of plutonium production and more importantly the rate of production of Pu.

The team used the ratio of 2 argon isotopes to monitor the rate which was very slow (verified by historian Richard Rhodes). It was already 1949 and although the Klaus Fuchs design was in their posession they lacked the thirty pounds of fuel required.

Meanwhile back in the US Los Alamos, having abandoned the inefficient gun-gadget designed a bomb core which used less Pu in the center surrounded by a shell of uranium-235 and by which the desired alpha was controlled by the Pu and which was a way to include U-235 in an implosion device. This geometry was termed as "composite". Many people outside the inner sanctum reasoned that composite referred to the presence in early models of a depleted uranium "tamper".

Of a sudden and out of the blue the AFOAT-ONE mission was at an end and a new name and mission happened because the USSR had detonated their first nuclear bomb. Most everyone at the Lab presumed that the Russian bomb was a clone of the Trinity bomb fired in New Mexico 7/16/45. I thought so too until I attended a staff meeting in old Delta Building near the West end of the main tech area. The speaker was an Airforce officer who reported a couple of things that turned up in the air samples followeing the USSR event. This officer reported that the bomb was "composite" and not only was the ratio of the two fuels similar to the US Mark VI but that the ratios of the fission fragments were likewise.

I have been frustrated for over 50 years because I wonder if I am the only one alive who even believes there was an AFOAT-TWO. Later the composite core was used in the US Mark-13 torpedo atom bomb. Any of you old-timers ever hear about AFOAT-TWO and its mission? Thanks, Galois