The M121 was a very large
air dropped bomb used by the
U.S. military
The United States Armed Forces are the military forces of the United States. U.S. federal law names six armed forces: the Army, Marine Corps, Navy, Air Force, Space Force, and the Coast Guard. Since 1949, all of the armed forces, except th ...
during the
Vietnam War
The Vietnam War (1 November 1955 – 30 April 1975) was an armed conflict in Vietnam, Laos, and Cambodia fought between North Vietnam (Democratic Republic of Vietnam) and South Vietnam (Republic of Vietnam) and their allies. North Vietnam w ...
. Originally developed from the British World War II-era
Tallboy bomb to be dropped from the
Convair B-36
The Convair B-36 "Peacemaker" is a strategic bomber built by Convair and operated by the United States Air Force (USAF) from 1949 to 1959. The B-36 is the largest mass-produced piston-engined aircraft ever built, although it was exceeded in span ...
bomber
A bomber is a military combat aircraft that utilizes
air-to-ground weaponry to drop bombs, launch aerial torpedo, torpedoes, or deploy air-launched cruise missiles.
There are two major classifications of bomber: strategic and tactical. Strateg ...
, it weighed 10,000 lb (4,500 kg) and contained an 8,050 lb (3,650 kg)
Tritonal
Tritonal is a mixture of 80% TNT and 20% aluminium powder, used in several types of ordnance such as air-dropped bombs. The aluminium increases the total heat output and hence impulse of the TNT – the length of time during which the b ...
warhead
A warhead is the section of a device that contains the explosive agent or toxic (biological, chemical, or nuclear) material that is delivered by a missile, rocket (weapon), rocket, torpedo, or bomb.
Classification
Types of warheads include:
*E ...
. Production of the M121 ceased in 1955, but stockpiles were retained until the Vietnam War.
Vietnam War
In December 1967, the
U.S. Air Force
The United States Air Force (USAF) is the air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its origins to 1 ...
began a testing program to use large bombs for
explosively clearing jungle areas for
landing
Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or " spl ...
of helicopters. After tests in the United States, the
U.S. Army
The United States Army (USA) is the primary land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of the United Stat ...
began dropping the bombs using
CH-54
The Sikorsky CH-54 Tarhe is an American twin-engine heavy-lift helicopter designed by Sikorsky Aircraft for the United States Army. It is named after Tarhe, an 18th-century chief of the Wyandot people, Wyandot Indian tribe whose nickname was "T ...
helicopter
A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and ...
s. Use of the helicopters was expensive, time consuming and inefficient due to the CH-54's limited
range
Range may refer to:
Geography
* Range (geographic), a chain of hills or mountains; a somewhat linear, complex mountainous or hilly area (cordillera, sierra)
** Mountain range, a group of mountains bordered by lowlands
* Range, a term used to i ...
. In October 1968, a
C-130
The Lockheed C-130 Hercules is an American four-engine turboprop military transport aircraft designed and built by Lockheed Corporation, Lockheed (now Lockheed Martin). Capable of using unprepared runways for takeoffs and landings, the C-130 w ...
crew
A crew is a body or a group of people who work at a common activity, generally in a structured or hierarchy, hierarchical organization. A location in which a crew works is called a crewyard or a workyard. The word has nautical resonances: the ta ...
from the
29th Tactical Airlift Squadron of the
463rd Tactical Airlift Wing flew a series of test drops while under the guidance of MSQ-77 radar controllers; additional test drops were made in December. In March 1969, the 463rd commenced Project
Commando Vault, and
bomb
A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechan ...
drops became a regular occurrence. Besides clearing the jungle and preventing the ambush of helicopters that were approaching the
landing zone
In military terminology a landing zone (LZ) is an area where aircraft can land.
In the United States military, a landing zone is the actual point where aircraft, especially helicopters, land (equivalent to the commonwealth landing point.)The Han ...
(the M121's blast diameter was 60 meters), the explosion also stunned the
NVA or
Viet Cong
The Viet Cong (VC) was an epithet and umbrella term to refer to the communist-driven armed movement and united front organization in South Vietnam. It was formally organized as and led by the National Liberation Front of South Vietnam, and ...
personnel within 500 meters and revealed or destroyed
booby trap
A booby trap is a device or setup that is intended to kill, harm or surprise a human or an animal. It is triggered by the presence or actions of the victim and sometimes has some form of bait designed to lure the victim towards it. The trap may b ...
s in the landing area.
[Frankum, Roland Bruce. ''Like rolling thunder: the air war in Vietnam, 1964-1975''. Rowman & Littlefield, 2005. .]
Due to the bomb's weight and powerful effects, ordnance handlers would chalk mark the bombs as "
Excedrin
Aspirin/paracetamol/caffeine is a combination drug for the treatment of pain, especially tension headache and migraine. It contains aspirin, a non-steroidal anti-inflammatory drug; paracetamol (acetaminophen), an analgesic; and caffeine, a stim ...
Headache #10,00x" where x was the sequence number of the bomb;
[John Brennan, Chris Evans. ''Vietnam War Helicopter Art: U.S. Army Rotor Aircraft''. Stackpole Books, 2012. .] a reference to the well known (at the time) advertising campaign promoting the efficacy of the Excedrin brand of extra strength pain relievers.
Use of the M121 to clear a jungle zone was a technical success, but the weapon did not satisfy
MACV
The U.S. Military Assistance Command, Vietnam (MACV) was a joint-service command of the United States Department of Defense, composed of forces from the United States Army, United States Navy, and United States Air Force, as well as their respecti ...
's command requirement to clear a jungle area for five helicopters at the same time.
[Thigpen, Jerry L. ''The Praetorian STARShip: the untold story of the Combat Talon''. DIANE Publishing, 2001. ] Despite this, the United States continued to use the M121 to clear helicopter landing zones in the jungle until stockpiles were depleted while a more powerful bomb was developed for jungle-clearing purposes. The new
BLU-82
The BLU-82B/C-130 weapon system, known under program "Commando Vault" and nicknamed " Daisy Cutter" in Vietnam for its ability to flatten a section of forest into a helicopter landing zone, was an American conventional bomb, delivered from eit ...
, developed in 1969, entered service later in the Commando Vault program. Unlike the M121, which used
TNT
Troponin T (shortened TnT or TropT) is a part of the troponin complex, which are proteins integral to the contraction of skeletal and heart muscles. They are expressed in skeletal and cardiac myocytes. Troponin T binds to tropomyosin and helps ...
, the BLU-82 used a slurry mixture of
ammonium nitrate
Ammonium nitrate is a chemical compound with the formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, but does not form hydrates. It is predominantly us ...
and powdered
aluminum
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
. It had a slightly bigger blast diameter (80 meters).
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Notes
{{reflist
References
* https://web.archive.org/web/20070124145412/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=1013
* http://members.aol.com/samc130/bc130.html
Commando Vault report at University of Texas Vietnam War archive
Cold War aerial bombs of the United States
Military equipment introduced in the 1950s