Cold War Close Call: 1961 B-52 Crash Revealed How a Safety Switch Prevented Nuclear Detonation

New Sandia accident reports released in 2021 detail the January 1961 B-52 crash over North Carolina in which two Mk 39 thermonuclear bombs survived the breakup. Both were reportedly kept in safe configurations by arm-safe switches (MC-772/MC-788), preventing detonation; one bomb deployed a parachute, its batteries fired, timer ran out, and its nose was crushed, while the other fell without a parachute, leaving a crater but not detonating. The reports also note that the arm-safe mechanism blocked the firing capacitor, and they discuss ALT 197’s proposed replacement of the arm-safe switch to ensure safety even if a weapon is released in the safe condition. These component-level findings, which align with Parker Jones’s 1969 assessment, enrich the public record beyond earlier, heavily redacted accounts.