Foreign Relations of the United States, 1961–1963, Volume VII, Arms Control and Disarmament

42. Report of the Ad Hoc Panel on Nuclear Testing⁰

Washington, July 21, 1961.

INTRODUCTION

At the request of the President, the Panel has considered the technical questions involved in a decision by the U.S. on the resumption of testing. The Panel’s report is divided into two sections: (1) Present and future unilateral U.S. test detection capabilities and (2) Present and future U.S. and Soviet nuclear warhead capabilities. The status of intelligence of Soviet testing during the moratorium is considered in a separate supplement.

The Panel’s task was facilitated by the recent report of the Fisk Panel to Mr. McCloy (2 March 1961),¹ which covered these problems in the context of a possible test ban treaty. After reviewing such new information as had become available since the publication of the Fisk Report, the Panel found that it was able to endorse the relevant portions of the Fisk Report essentially without exception.

In submitting this report, the Panel hopes that it will clarify the technical issues involved in a decision on the resumption of testing. The Panel wishes to emphasize, however, that while these technical issues have an important bearing on this decision, the final decision on whether or not to resume testing also involves very important non-technical or military issues which have not been included in the Panel’s considerations.

The Panel also wishes to express its concern over certain statements which have appeared in the press on the subject of resumption of testing. While some of these statements have been technically highly misleading, they have still given a great deal of information on U.S. programs to the USSR. At the same time, the Panel believes that these statements have seriously detracted from the political gains which have resulted from our constructive position in the Geneva Nuclear Test Ban Negotiations.

SUMMARY

We do not know whether or not the USSR has conducted any clandestine tests since November 1958. While some suspicious activity which might be connected with testing has been noted, this activity is equally compatible with other technical activities not involving nuclear tests. The USSR could have conducted underground nuclear tests without providing any intelligence information.

Despite future improvements in our unilateral detection capability, the USSR could still carry out a limited number of clandestine underground tests in the kiloton range which would very likely escape detection. The USSR could also carry out larger explosions, even up to yields in the megaton class, at an increasing penalty in time, cost and test effectiveness, and at increasing risk of detection. The greater the level of Soviet clandestine activity, the greater the possibility would be that it would be discovered through conventional intelligence, including [less than 1 line of source text not declassified].

Improvements in the yield to weight ratios of strategic warheads that may be achieved through weapons tests would give added flexibility to the designs of U.S. strategic systems, in particular with regard to reduced vulnerability and increased mobility. Proof tests would also remove possible doubts concerning the reliability of certain warheads. The significance of these developments is in part dependent on whether future U.S. strategy will emphasize deterrence or counterforce capability. At the same time, the status of Soviet weapons technology is probably such as to create a strong incentive for Soviet weapons tests, especially if the USSR desires smaller, more mobile strategic weapon systems to compensate for the anticipated loss of security of their present missile force when [less than 1 line of source text not declassified] becomes operational.

The principal areas of weapon improvements in the tactical weapons field involve: a) economy in the use of fissionable materials; b) reduction in diameter to permit interchangeability with conventional ammunition; and c) enhancement of neutron radiation effects. However, it is difficult to evaluate the potential value of nuclear warhead improvements to either the U.S. or the USSR since there is no established doctrine on the use of tactical weapons.

Enhanced neutron radiation weapons which would be relatively more effective against personnel under certain circumstances may have significance in tactical warfare. A prototype [less than 1 line of source text not declassified] which would produce some enhancement in neutron radiation at a cost comparable to a conventional fission weapon, is available for test. [1-1/2 lines of source text not declassified] If such devices can be developed in a militarily useful configuration, the most optimistic estimate for earliest availability of a first device for stockpile is 1965. [2-1/2 lines of source text not declassified] The date for operational availability would, therefore, not be appreciably affected by deferment of test resumption by a year or two. The significance of these developments is strongly dependent on the extent to which future U.S. strategy emphasizes the use of nuclear weapons in tactical warfare.

The present U.S. Nike-Zeus AICBM system is not limited by nuclear warhead performance or lack of knowledge on nuclear kill mechanisms but rather by the highly unfavorable exchange ratio of the cost of Nike-Zeus vs. increased number of enemy ICBM’s, especially if the enemy employs decoys. The known vulnerabilities of U.S. ICBM warheads to potential Soviet AICBM defense can be reduced without additional effects tests; however, nuclear tests to search for overlooked sources of vulnerability may become advisable in the future. Increasing the yield to weight ratios of missile warheads is one method of improving the ability of our ICBM’s to penetrate potential Soviet AICBM defenses by providing additional payload to incorporate measures to reduce warhead vulnerability or to carry penetration aids such as decoys.

One of the most important considerations in further technical developments is the possibility of surprises. In general, as far as yield to weight improvements is concerned, surprises are very unlikely in the strategic warheads beyond predicted developments. There could, however, be overlooked phenomena in weapons effects of various kinds. In the area of tactical nuclear weapons, where the room for invention is large, the possibility of important surprises is correspondingly great.

The range of weapon development tests which can be undertaken would not be seriously impaired if only underground tests were permitted. Nevertheless, it should be recognized that the restriction to underground tests would make some tests more difficult and costly. In addition, some weapons effects tests at high altitude of interest to (but on the basis of present knowledge not critical to) the AICBM problem could not be carried out if testing is only permitted underground.

In the absence of tests by either the U.S. or USSR, the U.S. would retain a degree of technological superiority in nuclear weapons for some time. If the U.S. continues to refrain from testing and the USSR engages in clandestine underground testing, the USSR could gain technological superiority in nuclear weapons to the extent discussed in the body of this report in as little as three to four years of extensive testing. If both the U.S. and USSR resume testing, the two countries will probably both approach the same general level of warhead technology in areas of interest in the relatively near future.

Although the limitations on our weapons progress imposed by lack of nuclear tests can to a considerable extent be compensated by efforts in other fields, such a self-imposed limitation would, in the long run, impair the rate of U.S. military progress. However, none of the specific weapons tests now discussed appear to be of such urgency from the technical and military point of view that a reasonable delay in reaching a formal decision on the resumption of nuclear testing would be critical. Therefore, any decisions in the near future concerning the resumption of nuclear testing can be governed primarily by non-technical considerations.

[Here follows the remainder of the 34-page Report.]

0. Source: Washington National Records Center, RG 330, OSD Files: FRC 65 A 3464, Atomic 400.112 8 Apr 61 (Jun-Nov 61). Top Secret; Restricted Data. Attached to a July 28 letter from Wiesner to McNamara, which states that the Panel made a preliminary report on its findings to the President on July 21, and requested comments by August 4. The panel was known as the Panofsky Panel after its Chairman, Wolfgang K.H. Panofsky. Other members were William A. Baker, Hans A. Bethe, Norris E. Bradbury, James B. Fisk, John S. Foster, Jr., George B. Kistiakowsky, Frank Press, Louis H. Roddis, John W. Tukey, and Walter H. Zinn. Keeny served as Technical Assistant.
1. See Document 4.