| scheduled shots do not give the necessary data to meet the early capability POLARIS requirement. 4, It has been necessary also to add to the program one other laboratory test. It was previously believed that the data required for the design of one warhead for the NIKE HERCULES could be obtained from the test of a basically similar device already included in the program. However, it is now felt necessary to test this second device in order to obtain the required data. 5. One other test of the original program has been deferred to the underground test series of very low-yield devices planned for the fall 1958 at the Nevada Test Site which I described in my November 23 letter, and which will be conducted as a separate test series to be known as Operation MILLRACE, 6, In summary, the over-all change to the HARDTACK program has been an increase of two scheduled shots, making a total of 19 scheduled laboratory and 5 scheduled DOD effects shots. In addition, there will be three contingent shots whose firing depends on the outcome of other shots in the series. Attached to this letter is a summarization of the scheduled and contingent nuclear shots. in the HARDTACK and MILLRACE programs and their objectives, 7. In addition to these nuclear firings, we must fire some two to ten safety tests of certain designs to establish that, detonated accidentally, no nuclear reaction would occur. if These safety tests will be conducted at the Nevada Test Site, three in the spring 1958 and seven in the fall 1958. Earliest firing of two of the three is necessitated by the expedited POLARIS program, -~ 18 - Appendix "c"