OVERVIEW: A U.S. tactical air-dropped nuclear bomb developed during the early Cold War era. The M57 was intended for multipurpose use, including against ground forces and fortified targets, with a sub-strategic yield of approximately 20 kilotons.

DETAIL: The M57 was developed as a lightweight, tactical fission bomb suitable for fighter-bomber deployment. It utilized a plutonium-based implosion design and incorporated conventional explosive lenses for core compression. The bomb's designation followed the U.S. Army’s ordnance nomenclature, and it was intended to fill the gap between conventional munitions and larger strategic nuclear weapons. It measured under 14 inches in diameter and weighed less than 850 lb, making it compatible with a wide array of aircraft.

The M57 Mod 0, featured a fixed yield of ~20 kilotons and was equipped with airburst or contact fuzing options. This version was optimized for battlefield deployment and incorporated enhanced safety mechanisms for transport and handling.

The M57 was intended for tactical use by fighter-bombers like the F-84F and F-100 Super Sabre, using low-level penetration or toss-bombing techniques. It could be employed against troop concentrations, airfields, or hardened structures with precise targeting through visual delivery.

NOTE:
IOC: ~1956
Operators: United States
Platform: F-84F, F-100, F-105, F-4 Phantom II, F-15E, F-16A/C, and other compatible tactical aircraft
Conflicts: Cold War (deployed, not used in combat)

SOURCE:
U.S. Department of Energy: https://www.energy.gov/
National Museum of the USAF: https://www.nationalmuseum.af.mil/
Atomic Heritage Foundation: https://www.atomicheritage.org/
Federation of American Scientists (FAS): https://fas.org/nuke/guide/usa/bomber/m57.htm