21 April 1955
Top Secret
(Special File)
Copy No. 1

To Comrade A.P Zaveniagin,

It is necessary at this time to determine the type of main compression device that will be chosen for strategic use.

Calculations made throughout 1954–5 showed that within the [parameters of the] overall dimensions of the RDS-6 system, and at the expense of (…) kg U²³⁵, it is possible to make the following products:

1. One SD type device with a yield of 1.8 million tons, with a zone of destruction of 12.2 kilometers in diameter (the area of the zone of destruction would be 117km²).
2. Two SD type device, with a yield of 1 million ton each, with a zone of destruction of 10 kilometers in diameter (the total area of the zone will be 156km²).
3. Five RDS-27 device with a yield of 0.35 million tons each, with a zone of destruction 7 kilometers in diameter (total area=190 km²).

If one takes into account the cost of the carrier (the R-7 rocket), and of lithium deuteride six, then the cost of one SD device with a yield of 1.8 million tons would equal the cost of 4 RDS-27 devices. Thus the ratios between the zones of destruction of the two devices will not be 190:117, but 152:117.

In our opinion, the RDS-27 is the optimal normal compression strategic device. This system gives us the greatest area of destruction, will provide great flexibility, and the opportunity to destroy a maximal number of targets. It also increases the likelihood of hitting the target in case of the downing of the delivery vehicle, or in case of a significant [unclear] under fire.

An important practical implication of our view is the necessity of the deployment of long-range rockets and aircraft, in accordance with the production of the U²³⁵ as outlined in our calculations.

A. Alexsandrov
Iu. Khariton
A. Sakharov
Ia. Zel’dovich
21 April 1955