Shot Franklin Prime was the 16th atomic test of Operation Plumbbob, detonated on 30 August 1957 from a balloon at 750 feet above Yucca Flat, Nevada Test Site. It was a Los Alamos Scientific Laboratory development test of the XW-30 warhead — a retesting of the earlier Shot Franklin, which had fizzled at just 7% of its predicted yield. For Franklin Prime, the gas-boosted all-oralloy implosion device was enlarged and its core augmented with additional enriched uranium, producing a yield of 4.7 kilotons. This Lookout Mountain Laboratory photograph — AEC-57-5828 — shows the cloud at a mature stage, the mushroom cap fully separated from the stem, its cauliflower structure visible against the dark sky. At ground level the base surge of disturbed desert soil spreads outward from the stem. Franklin Prime detonated the day before Shot Smoky — the 44-kiloton tower shot that would become one of the most consequential and controversial tests of the entire series.