Mk7

Began with a study made by Group W-4 of the Los Alamos Scientific Laboratory in late 1949, early 1950. The results of these studies were presented to the May 26, 1950, meeting of the TX-5 Steering Committee by W-4, who noted that the Group was interested in the development of small-diameter bombs for tactical military use.^7.1 A TX-5 Steering Committee meeting was held July 17, 1950, followed by a joint meeting August 2, 1950, with the Sandia Weapons Development Board. In-flight insertion problems required study and Sandia prepared both forward and rear insertion proposals, ultimately deciding on the former, resulting in a considerable shift of the bomb center of gravity during insertion. Later it was decided to place the relatively heavy cartridge at the forward face of the sphere assembly and a horizontally operating insertion mechanism aft of the sphere. Controls were installed in the cockpit of the carrying aircraft, so that insertion or retraction of the capsule could be remotely accomplished in flight.^7.3

At the recommendation of the TX-5 Steering Committee, the Mk7 Mod 0 bomb was released September 1, 1951, and early production achieved July 1952, however an emergency capability program had been proposed, to provide some Mk 7 weapons in advance of regular production. These weapons would contain either production or development components, and it was requested that all possible support be given to this program, called “7N“^7.5

Weighing 2,700lbs^3.1 or 1,800lbs^6.2 , being 183″ long and being 30.5″ in diameter^7.4, the Mk7 was the first tactical nuclear bomb.^5.1

Proof tested in shot Climax of Operation Upshot-Knothole with a yield of 61Kt^6.1 and shot Easy of Operation Buster-Jangle with a yield of 31Kt ^6.2

Donald Cotter served as the project engineer.^5.1

Completion of wind-tunnel model tests at speeds up to Mach 1.2 demonstrated that the shapes possessed adequate stability, and full-scale drops were started. The first such drop at the Salton Sea Test Base, coupling of roll and pitch frequencies, resulted in the bomb’s going into gyrations of 45 degrees and shedding its tail assembly, while another drop produced severe pitching action.^7.4 To mitigate roll-pitch coupling, that the Mk7 (and Mk12) were encountering, the use of fin-tabs was employed and later, canted fins.

The beginning of February 1952, a limited number of 7N bombs entered the stockpile. The Mk7 Mod 0 officially entered stockpile in July 1952.^4.1

Mk7 warhead used within the Corporal missile.^1.1 The Army also requested a 30-inch diameter variant of the Mk7 warhead be developed for implementation into the Nike missile in December 1954 with the Division of Military Application approving authorization January 1955.^2.1

TX-7 was to be used with the Thor IRBM, eventually evolving into the TX-7-X1 design. The major differences from the Mk7 was in the fuzing system. The TX-7-X1 would provide the following in-flight options:^4.1

1. Radar 1 with safe separation time 1
2. Radar 2 with safe separation time 1
3. Radar 1 with safe separation time 2
4. Radar 2 with safe separation time 2
5. Time of fall setting 1
6. Time of fall setting 2
7. Contact burst

The contact fuze was used as a clean-up feature in the event the primary fuze should fail.^4.2