Today in 1962, the US conducted Frigate Bird, the only US nuclear proof test of a live warhead on an operational ballistic missile. In the Pacific, the USS Ethan Allen (SSBN 608) launched a Polaris A1 SLBM toward Christmas Is. (Kiritimati). Yield of the W47Y1 warhead was ~600kt.

— Stephen Schwartz (@AtomicAnalyst) May 6, 2019