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

110. Memorandum From the President’s Special Assistant for Science and Technology (Wiesner) to President Kennedy⁰

Washington, December 19, 1961.

I have reviewed Dr. Brown’s letter of 12 December¹ to you setting forth his views on the need for atmospheric tests. Dr. Brown has prepared a thoughtful document which makes the best case for atmospheric testing that I have seen. I believe that he has focused on the most important technical and military issues involved and has correctly identified the relative priorities of the tests. Nevertheless, my assessment of the proposed tests leads me to the conclusion that, while these tests would certainly contribute to our military strength, they are not critical or even very important to our over-all military posture. I believe that our most important task is to maintain an extremely effective deterrent and that we have the capability to do so without conducting atmospheric tests. I believe, therefore, that you have the flexibility to make whatever decision on this matter best supports your broader foreign policy and national security objectives.

I agree with Dr. Brown that the proposed effects tests are the most important part of the proposed atmospheric test series. These tests relate to significant problems on which our knowledge is far from complete. I do not believe, however, that the proposed effects tests will be nearly as significant as Dr. Brown’s analysis would indicate. Specifically, while the proposed effects tests relating to warhead vulnerability would certainly increase our knowledge on this important military problem, I do not believe these tests are critical to our understanding of this problem or that they would as stated result in the elimination of major causes of vulnerability. This problem was studied last Spring in great detail by an Ad Hoc Panel of your Science Advisory Committee² whose report on this subject was in a large part responsible for stimulating the present justifiable concern within the DOD about the vulnerability of our missiles. With regard to the vulnerability of our own warheads, the Panel’s investigation showed that we have considerable knowledge on this subject from calculations and laboratory experiments and could obtain a great deal more knowledge both by these techniques and by highly instrumented underground tests. In fact, unless full advantage is taken of the information we already have on this subject, the proposed atmospheric tests will probably simply confirm what we already know about our weapons, namely that they are quite vulnerable to certain nuclear effects. Improvement of the “hardness” of our missiles to nuclear effects is an engineering problem which requires tests of a large variety of structures; such a program clearly has to rest primarily on laboratory experiments. With regard to any future nuclear AICBM defense that we might develop against Soviet missiles, our lack of knowledge concerning the specific design of Soviet missiles probably will introduce, as Dr. Brown points out, a much larger factor of uncertainty than our lack of knowledge concerning the effects themselves.

I consider that the effects tests concerned with nuclear “blackout” of certain regions of the radar and radio frequencies spectrums to be the most significant aspect of the proposed test series since additional data on these phenomena probably cannot be obtained without atmospheric tests. In view of the complex nature of this problem, I have asked an Ad Hoc Panel of highly knowledgeable scientists to meet on 19-20 December³ in order to examine the actual state of our knowledge on this problem and to evaluate the proposed experiments. It must be recognized, however, that we already know the general nature of these effects on radar and communications as the result of previous high altitude nuclear tests and extensive calculations and that this factor has been taken into account in technical planning for the last year or two. For example, in view of the severe effects anticipated on high frequency radio communication, SAC has already modified their communication procedures so that they are confident that they will not be affected by any nuclear blackout phenomena associated with high altitude nuclear explosions. As another example, Nike-Zeus radars have also been modified to the extent that appears possible to minimize the effects of nuclear blackout.

I also consider that the proposed small surface test to determine whether the resulting electromagnetic signal in the ground will affect command links at an ICBM site to be an important experiment. However, as Dr. Brown indicates, calculations indicate that this effect will not introduce any serious problems and special equipment is being incorporated in these systems to protect them against this effect even if it were to prove considerably larger than expected. With regard to the question of ground shock on hard ICBM sites, as Dr. Brown indicates, the proposed surface tests would give only limited information on a problem on which there is already a great deal of general knowledge. In addition, a rather elaborate underground test has been included in the present underground series to provide specific data on this problem.

With regard to the proposed development shots, I would agree with Dr. Brown that the most interesting development area is that of achieving [less than 1 line of source text not declassified] in weights of 50-100 lbs. This could prove of real value in permitting the use of multiple warheads or allow incorporation of additional penetration aids in some of our smaller missile systems such as Polaris and Minuteman if there should be concern at some future date that they were too vulnerable to a future Soviet AICBM system. This would also provide an option for smaller more mobile missile systems if these should be desired. It should be recognized, however, that tests in this yield range could be conducted underground. This would result in some, but certainly not prohibitive, increases in cost in the test program and a stretch out in the test program. The resulting delay in availability of weapons would not be out of phase with the long range nature of these requirements. While I have always thought that underground testing would be more difficult than many of its advocates claimed, the current problem that the AEC is having with underground testing appears to be part of the normal learning process, and I am confident that adequately instrumented testing at these higher yields could be accomplished if there were a real need to do so. At yields above a megaton, underground testing will always be extremely difficult if not impossible as a practical matter. However, I do not believe that the higher yield tests proposed are particularly important to our military posture. Increasing the yield of our larger strategic warheads for Atlas and Titan by a factor of two is of little military significance as these vehicles have adequate payload capacity to carry large yield weapons and significant quantities of penetration aids if these prove necessary because of any future Soviet AICBM systems.

If we begin atmospheric testing, I would agree that the tests of some of the higher yield weapons which are based on the extrapolation of proven designs would be justified so that the laboratories could have confidence in extrapolating further improvements in these designs. However, in themselves these tests are not necessary to establish confidence in the weapons since they have been certified by the AEC for stockpiling and there is a very high degree of confidence that they will give yields very close to those estimated.

I think that it should be recognized that, if it is considered important to test weapons of higher yield than can reasonably be tested underground (above a few hundred kilotons), the technical option exists to test such weapons in outer space. While this possibility has been largely ignored in recent discussions, it is clearly within our present technical capability. The penalty for space testing would be an initial delay of a year or so and considerably higher costs than of atmospheric testing. However, these costs would not be prohibitive if the requirements were considered important.

In these comments on Dr. Brown’s paper, I have attempted to put the various proposed atmospheric tests in proper perspective as to their importance. However, I agree with Dr. Brown that the significance of atmospheric testing should be judged not by the criticality of any individual test but by the over-all significance of the proposed series. Clearly the cumulative significance of the proposed tests is greater than that of any individual test. Nevertheless, I believe that a realistic appraisal of the proposed test series even when taken as a whole, indicates that it is not only not critical to our military posture but would not, in fact, be particularly significant to it. I believe this to be a particularly valid conclusion when one considers the alternative paths of weapon development available to us in aggressive use of underground testing, imaginative laboratory work, and possibly even space testing if it should prove necessary. Therefore, I have concluded that, while the proposed atmospheric tests would be desirable as part of our over-all military development effort if there are no political objections, the military security of the U.S. would not be endangered in the event that you determine that our longer range national policy would be better served by a decision not to test in the atmosphere at this time.

J. Wiesner

0. Source: Kennedy Library, National Security Files, Subjects Series, Nuclear Weapons Tests, 12/19-20/61. Secret; Restricted Data.
1. Document 109.
2. Apparent reference to the Ad Hoc Panel on Nuclear Testing (Panofsky Panel); see Document 42.
3. Not further identified.