144. Letter from President Kennedy to Prime Minister Macmillan, September 71

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Dear Prime Minister:

I have just completed a careful review of the plans for completing our atmospheric test series, which as you know was interrupted in mid-summer by a failure at the launching pad in Johnston Island, with substantial damage to the immediate installations.

In reviewing the proposals, we have been faced with a number of new considerations. One is the quite unexpected magnitude of the deposit of high energy electrons in addition to the Van Allen Belt. This experience has led us to a drastic downward revision of the planned yields for high altitude tests.

We have also been reviewing the results of the earlier atmosphere series in Christmas Island and have reached the conclusion that very promising technical developments affecting yield-to-weight ratios should be followed up promptly, and accordingly we plan not more than four additional atmospheric tests, to be carried out by air drops near Johnston Island, along with the resumed high altitude tests.

The total number of tests thus authorized is seven, three at high altitudes and four by air burst from aircraft drops. I am reserving decision on an eighth test which would be at a high [Facsimile Page 2] altitude, with a yield which might affect the radiation belts and is not yet adequately calculated.

None of these tests is proposed for Christmas Island, but I do wish to let you know that this is our general plan, well before public announcement which is now expected to be made early in the week after next.

Our object here is to complete the interrupted series, and to include a modest number of additional tests which I hope will have the effect of making it much easier for us to avoid atmospheric testing for a substantial time after November. That may allow us to make further progress along the lines of the exchange we have just had about a test ban (on this latter subject we are still working out our proposed answer to Khrushchev and will be in touch with you shortly).

The total fallout from the resumed series should be on the order of 15% of that involved in our earlier tests this year, and it will remain [Typeset Page 381] true that our whole series has very much less radioactive fallout than the Soviet tests in the two series which they have conducted.

Our current plan is that these last tests will be conducted beginning about 30 September and ending early in November. Our impression is that Soviet tests will continue through approximately [Facsimile Page 3] the same period of time, and thereafter there may be a renewed opportunity for some agreement, in a situation in which no atmospheric tests are going forward.

Our underground testing program is now scheduled to continue routinely. I want you to know quite privately that I am prepared to interrupt this program for a limited time if at any point that appears to be a useful step in getting forward toward a test ban agreement. We have just received your Government’s request for the inclusion of a British underground test at Nevada, and I am sure that as long as our own testing underground continues, there will be no difficulty in scheduling such a test for you. A proper diplomatic answer will be coming back to you on this last point through the usual channels.

  1. U.S. atmospheric and underground nuclear testing schedule. Top Secret. 3 pp. Department of State, Presidential Correspondence: Lot 66 D 204, KennedyMacmillan, Vol. II.