Ivy King was the highest-yield pure-fission nuclear weapon ever tested, producing 500 kilotons without any thermonuclear boosting.
Key Facts
- Explosive yield
- 500 kilotons of TNT kt
- Delivery aircraft
- B-36H bomber
- Burst altitude
- 1,480 feet (450 m) ft
- HEU core mass
- 60 kg of highly enriched uranium kg
- Mark 18 weapons produced
- 90
- Detonation time
- 11:30 local time (23:30 GMT)
By the Numbers
Location
Cause → Event → Consequence
The United States, responding to Soviet nuclear weapons development, launched Operation Ivy to test advanced nuclear designs. Ivy King was developed as a contingency in case Ivy Mike failed to achieve a thermonuclear reaction, ensuring the U.S. would still demonstrate a dramatic yield increase over existing weapons regardless of the thermonuclear test's outcome.
On November 16, 1952, a B-36H bomber dropped the Ivy King device—designated the 'Super Oralloy Bomb'—over Enewetak Atoll. The weapon, designed by physicist Ted Taylor and using a 92-point implosion system with a 60 kg HEU core, detonated at 1,480 feet altitude and produced a 500-kiloton explosion, the largest ever from a pure-fission device lacking thermonuclear materials.
The design entered production as the Mark 18 nuclear bomb, with 90 units manufactured by the Atomic Energy Commission. Despite proving the upper limit of pure-fission yields, the weapons were costly due to their heavy HEU cores. Primary designer Ted Taylor subsequently became a prominent advocate for nuclear disarmament, and Ivy King's yield record among non-boosted fission devices has never been surpassed.
Political Outcome
The United States successfully demonstrated a 500-kiloton pure-fission weapon, establishing an upper bound for non-boosted fission yields and producing 90 Mark 18 bombs for the nuclear arsenal.
Soviet nuclear advances had narrowed the U.S. strategic advantage in weapon yields
U.S. demonstrated overwhelming yield superiority through both pure-fission and thermonuclear tests in Operation Ivy