Nuclear Artillery - United States Nuclear Artillery

United States Nuclear Artillery

United States developments resulted in nuclear weapons for various artillery systems, after the short-lived M65 Atomic Cannon standard howitzers were used. Delivery systems include, in approximate order of development:

• MGR-1 Honest John free flight rocket delivering W7 nuclear weapon, 1953
• M65 Atomic Cannon delivering 280mm W9 and W19 nuclear shells, 1953
• MGM-5 Corporal missile delivering W7 nuclear weapon, 1955
• M110 howitzer delivering 203mm W33 nuclear shell, deployed in 1957
• M-28 Davy Crockett (nuclear device) M-388 warhead derived from W54, 1961-1971
• MGM-18 Lacrosse missile with nuclear warhead. It was deployed in West Germany from 1959 to 1963.
• M109 self-propelled and M114 towed howitzers delivering 155mm W48 nuclear weapon starting in 1963
• MGM-29 Sergeant missile delivering W52 nuclear weapon, 1963
• MGM-31 Pershing missile delivering W50 nuclear weapon, 1969
• MGM-52 Lance missile delivering W70 nuclear weapon, 1972
• Pershing II missile delivering W85 nuclear weapon, 1983

The first artillery test was on May 25, 1953 at the Nevada Test Site. Fired as part of Operation Upshot-Knothole and codenamed Shot GRABLE, a 280 mm (11 inch) shell with a gun-type fission warhead was fired 10,000 m (6.2 miles) and detonated 160 m (525 ft) above the ground with an estimated yield of 15 kilotons. This was the only nuclear artillery shell ever actually fired in the U.S. nuclear weapons test program. The shell was 1384 mm (4.5 ft) long and weighed 365 kg (805 lb). It was fired from a special, very large, artillery piece, nicknamed the "Atomic Annie", built by the Artillery Test Unit of Fort Sill, Oklahoma. About 3,200 soldiers and civilians were present. The warhead was designated the W9 nuclear warhead and 80 were produced in 1952 to 1953 for the T-124 shell. It was retired in 1957.

Development work continued and resulted in the W19. A 280 mm shell, it was a longer version of the W9. Only 80 warheads were produced and the system was retired in 1963 coinciding with the introduction of the W48 warhead.

The W48 was 846 mm long and weighed 58 kg; it was in a 155 mm M-45 AFAP (artillery fired atomic projectile) for firing from standard 155 mm howitzer. The fission warhead was a linear implosion type, consisting of a long cylinder of subcritical fissile material which is compressed and shaped by explosive into a supercritical sphere. The W48 yielded an explosive force of just 100 tons of TNT.

The W48 went into production beginning in 1963, and 135 Mod 0 version projectiles were produced by 1968 when it was replaced by the Mod 1. The Mod 1 was manufactured from 1965 through 1969. 925 of these were produced.

Only one type of artillery round other than the W48 was produced in large numbers. It was the W33 nuclear warhead for use in an 8-inch-diameter (200 mm) artillery shell. About 2,000 of these warheads were produced from 1957 to 1965. Each XM422 projectile was 940 mm long, it and had a projectile weight of 243 pounds. XM422 were fitted with a triple-deck mechanical time-base fuze. They were to be fired from a standard eight-inch howitzer, if the use of this weapon had ever been called for.

The W33's four explosive yields were all greater than that of the W48. M422 projectiles were hand-assembled in the field to provide the required yield, three yielding 5 to 10 kilotons and one with 40 kilotons. There was also a ballistically matched spotting round (HES M424) and a special white bag charge system, M80, composed of charges one through three. The M423 ordnance training rounds and their associated "bird cages" can be seen at the National Atomic Museum in Albuquerque, New Mexico.

Efforts were made to update the warheads: the 155 mm W74 and 203 mm W75 were developed from about 1970, and it were intended to have a yield of 100 tons or more. These versions were canceled in 1973. A further development program began in the 1980s: the W82, for the XM-785 (a 155 mm shell), was intended to yield up to two kilotons with an enhanced radiation capability. Its development was halted in 1983. A W82-1 fission-only type was designed but was canceled in 1990.

Other developments also continued. In 1958 a fusion warhead was developed and tested, the UCRL Swift. It was 622 mm long, 127 mm diameter, and weighed 43.5 kg. At its test it yielded only 190 tons; it failed to achieve fusion and only the initial fission explosion worked correctly. There are unconfirmed reports that work on similar concepts continued into the 1970s and resulted in a one-kiloton warhead design for 5-inch (127 mm) naval gun rounds; these, however, were never deployed as operational weapons.

In 1991 the US unilaterally withdrew its nuclear artillery shells from service, and Russia responded in kind in 1992. The US removed around 1,300 nuclear shells from Europe and reportedly dismantled its last shells by 2004. Focus has since moved to development of nuclear bunker buster munitions.