The M139 bomblet was a U.S. sub-munition designed for use in warheads as a chemical cluster bomb

Cluster bomb

A cluster munition is a form of air-dropped or ground-launched explosive weapon that releases or ejects smaller sub-munitions. Commonly, this is a cluster bomb that ejects explosive bomblets that are designed to kill enemy personnel and destroy vehicles...

. Each bomblet held a little more than one and a quarter pounds of sarin

Sarin

Sarin, or GB, is an organophosphorus compound with the formula [2CHO]CH3PF. It is a colorless, odorless liquid, which is used as a chemical weapon. It has been classified as a weapon of mass destruction in UN Resolution 687...

 nerve agent.

History

In 1964, a new warhead size was standardized for the 318 mm Honest John rocket

MGR-1 Honest John

The MGR-1 Honest John rocket was the first nuclear-capable surface-to-surface rocket in the US arsenal.The first nuclear-authorized guided missile was the MGM-5 Corporal. Designated Artillery Rocket XM31, the first such rocket was tested 29 June 1951 and the first production rounds were delivered...

, the warhead held 52 M139 bomblets. When the MGM-29 Sergeant

MGM-29 Sergeant

The MGM-29 Sergeant was an American short-range, solid fuel, surface-to-surface missile developed at the Jet Propulsion Laboratory. Activated by the US Army in 1962 to replace the MGM-5 Corporal it was deployed overseas by 1963, carrying the W52 nuclear warhead or alternatively one of high explosives...

 was deployed in the 1960s, it had the capacity to deliver a warhead carrying 330 M139 bomblets. Subsequent missile systems, including the Pershing missile

Pershing missile

Pershing was a family of solid-fueled two-stage medium-range ballistic missiles designed and built by Martin Marietta to replace the PGM-11 Redstone missile as the United States Army's primary nuclear-capable theater-level weapon. The Pershing systems lasted over 30 years from the first test...

, had the capability to carry warheads with the M139 inside. In total, about 60,000 M139s were produced, and stored; almost all were destroyed between April and November 1976.

Specifications

The M139 was a 4.5 inches (11.4 cm) spherical bomblet that was filled with 1.3 pounds (589.7 g) of sarin

Sarin

Sarin, or GB, is an organophosphorus compound with the formula [2CHO]CH3PF. It is a colorless, odorless liquid, which is used as a chemical weapon. It has been classified as a weapon of mass destruction in UN Resolution 687...

 (GB). On the outside of the device were "vanes", the vanes created a spin which armed the impact fuze. This "spin-to-arm" type fuze required between 1,000 and 2,000 rotations per minute to arm, which made handling the bomblets simpler because they were insensitive to normal movements. The bomblet's interior contained a central explosive burster charge, containing 0.16 pounds (72.6 g) of composition B

Composition B

Composition B, colloquially "comp B", is an explosive consisting of castable mixtures of RDX and TNT. It is used as the main explosive filling in artillery projectiles, rockets, land mines, hand grenades, sticky bombs and various other munitions...

, and two outer compartments which contained the sarin.

Tests involving the M139

The M139 bomblet was used by the U.S. Army in at least two instances of chemical weapons testing. In 1967 there were two series' of tests which sought to learn the effects of Sarin dropped in the bomblets over two different types of forest environment. The first series of tests, known as Green Mist, took place March 25–April 24, 1967. Conducted in Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, the purpose of the tests was to ascertain the effect of Sarin-filled M139s being dropped and disseminated over a canopy rain forest. The Hawaii tests used both sarin

Sarin

Sarin, or GB, is an organophosphorus compound with the formula [2CHO]CH3PF. It is a colorless, odorless liquid, which is used as a chemical weapon. It has been classified as a weapon of mass destruction in UN Resolution 687...

 nerve agent

Nerve agent

Nerve agents are a class of phosphorus-containing organic chemicals that disrupt the mechanism by which nerves transfer messages to organs...

 and the simulant methylacetoacetate.

Another test using the M139 took place at the Gerstle River test site, near Fort Greely

Fort Greely

Fort Greely is a United States Army launch site for anti-ballistic missiles located approximately 100 miles southeast of Fairbanks, Alaska. It is also the home of the Cold Regions Test Center , as Fort Greely is one of the coldest areas in Alaska, and can accommodate cold, extreme cold, or...

, Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

, from June to July 1967. The purpose of these tests was to determine the effectiveness of Sarin-filled M139 and BLU-19/B23 bomblets when dropped from a SADEYE

CBU-75

The CBU-75 Sadeye was a United States cluster bomb used during the Vietnam War. It could hold 1,800 one pound BLU-26 anti-personnel bomblets, each of which containing 0.7 pound of explosives with impact or time delay fuzes that would produce around 600 fragments....

 dispenser in a summer forest environment. The tests were collectively known as "Dew Point". Both 1967 testing operations were overseen by the U.S. Army's Deseret Test Center

Deseret Test Center

The Deseret Test Center was a U.S. Army operated command in charge of testing chemical and biological weapons during the 1960s. Deseret was headquartered at Fort Douglas, Utah.-History:...

. Both M139 tests were part of Project 112

Project 112

Project 112 was a biological and chemical weapons experimentation project conducted by the US Army from 1962 to 1973. The project started under John F. Kennedy's administration, and was authorized by his Secretary of Defense Robert McNamara, as part of a total review of the US military. The name...

.