Caption:
Oak shot was a prototype test of the LASL designed TX-46 system fired June 28, 1958. The test was conducted in very shallow water (12 feet). The device was horizontal on the barge, with the axis 3 feet above the barge deck, which was in turn 5.6 feet above the water line. The barge weighed 223 tons and was unballasted to provide a shallow draft. The subsurface crater produced was 5740 feet diameter and 204 feet deep. Operation Hardtack I was a series of 35 nuclear tests conducted by the United States in 1958 at the Pacific Proving Grounds. In 1958 the arms race proceeded apace, with the enormous weapons production infrastructure and both weapons labs operating at full speed. Partly this burst of testing activity was due to building pressure for an imminent test moratorium, leading the weapons labs to rush as many device types to the test range as possible. A total of 35.6 megatons were shot during this series. The lab tests centered on ICBM and SLBM missile warheads and high yield strategic bombs. The DOD conducted high altitude multi-megaton tests to study their usefulness for ABM (anti-ballistic missile) warheads, and discovered the high-altitude EMP (electromagnetic pulse) effect in the process. Effects tests of underwater explosions were also conducted.