A micro-nuclear weapon, colloquially referred to as a "micro nuke" or "mini-nuke" is the smallest class of tactical nuclear weapon operated by pre-war militaries. A micro-nuclear weapon is generally defined as a nuclear warhead with a yield equivalent to less than 1 kilotons (1000 tons) of TNT. Micro-nuclear warheads were first developed in the late 1950s and tested in the early 1960s with weapons such as the M28 "Davy Crockett" nuclear recoilless rifle rounds, with a yield of ten tons, and development continued for the next 120 years, culminating the 2076 development and deployment of the M46 "Fat Man" man-portable micro-nuclear launcher. In general, micro-nuclear weapons were used in a tactical role for use against targets such enemy bomber formations, tank formations, artillery batteries, and formations of warships.
First Generation (1950-1980)
The first generation of micro-nuclear weapons were developed in the late 1950s and tested in the late 1950s. Among these weapons were the AIR-2 Genie nuclear air-to-air rocket, first entering service in 1958, intended to destroy entire Soviet bomber formations with a single weapon with a weapon with a yield of about 1.5 kilotons. The W54 nuclear warhead entered service in 1961, initially intended for use in the M28 "Davy Crockett" nuclear recoilless rifle and as a "backpack nuke" placed by special forces. The W54 would later be adopted for used with the AIM-26 Falcon air-to-air missiles, as well as on some models of torpedo. In the 1960s, some nuclear weapons were also developed as "dial-a-yield" devices that, depending on settings, could be considered conventional or micro-nuclear weapons, such as the W-61.
Second Generation (1980-2070)
The second generation of micro-nuclear weapons were developed in the 1970s and 1980s, consisting of primarily of upgrades of the W-61 and the placement of the weapon in more advanced missiles, most notably the AIM-7 Sparrow and AIM-9 Sidewinder air-to-air and Harpoon anti-shipping missiles. In the 2020s, when these weapons were replaces by the AIM-15 Copperhead and AIM-47 air-to-air and AGM-180 supersonic anti-ship missiles, these two had micro nuclear warheads developed for them. In addition, rocket-assisted nuclear shells for 155mm and 203mm artillery pieces with a yield of about 1 kiloton were developed in the 1980s. In 2009, the B-61 nuclear warhead was supplemented by the Mark 28 Micro-Nuclear Weapon, as device specifically designed to be used as an air-dropped micro-nuclear weapon with a yield of between 10 tons and 1 kiloton. In the 2030s, ten ton yield nuclear warheads were also placed on smaller helicopter-launched TOL (Tube launched, Optically-targetted, Laser guided) anti-tank missiles such as those mounted on the AH-56 Cheyenne, ACV-80, and VB-02 Vertibird. With these weapons, the helicopters were capable of wiping out formations of enemy tanks, an capacity considered valuable as US forces expected to face massive waves of thousands of Soviet and later Chinese tanks.
Third Generation (2070-2077)
The third generation of micro-nuclear weapons were characterized by downsizing to the point that some in the military brass considered them absurd, believing that conventional explosives could do the same job more efficiently and without releasing harmful radiation. Nonetheless, the W-94 micro-nuclear weapon, a device the size of a football with a yield comparable to a 155mm artillery shell was developed. The weapon was deployed as an air-dropped cluster bomb and deployed from chutes that could be mounted on aircraft such as the VB-02 Vertibird starting in 2072. At the same time works started on a man-portable launcher for the device. Initial research was in the direction of deploying the device from a man-portable rocket or missile, but the weight of the warhead in addition to a rocket powerful enough to hold it make the launcher prohibitively heavy. The problem of launching the device far enough was solved at a testing facility at Fort Strong, near Boston, Massachusetts. The system adopted used a heavy spring mechanism accompanied by a rear-mounted precussion charge, a design similar to the World War II-era British PIAT anti-tank weapon, to launch the warhead up to about 150 meters.