The Mk/B53 was a high-yield
bunker buster
A bunker buster is a type of munition that is designed to penetrate hardened targets or targets buried deep underground, such as military bunkers.
Armor piercing shells Germany
Röchling shells were bunker-busting artillery shells, developed ...
thermonuclear weapon
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
developed by the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
during the
Cold War
The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
. Deployed on
Strategic Air Command
Strategic Air Command (SAC) was a United States Department of Defense Specified Command and a United States Air Force (USAF) Major Command responsible for command and control of the strategic bomber and intercontinental ballistic missile compon ...
bombers, the B53, with a
yield of 9 megatons, was the most powerful weapon in the
U.S. nuclear arsenal after the last
B41 nuclear bombs were retired in 1976.
The B53 was the basis of the W-53 warhead carried by the
Titan II missile, which was decommissioned in 1987. Although not in active service for many years before 2010, fifty B53s were retained during that time as part of the "hedge" portion of the
Enduring Stockpile until its complete dismantling in 2011. The last B53 was disassembled on 25 October 2011, a year ahead of schedule.
With its retirement, the largest bomb currently in service in the U.S. nuclear arsenal is the
B83, with a
maximum yield of 1.2 megatons. The B53 was replaced in the
bunker-busting role by the
B61 Mod 11
The B61 nuclear bomb is the primary thermonuclear gravity bomb in the United States Enduring Stockpile following the end of the Cold War. It is a low-to-intermediate yield strategic and tactical nuclear weapon featuring a two-stage radiation im ...
.
History

Development of the weapon began in 1955 by
Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...
, based on the earlier
Mk 21 and
Mk 46 weapons. In March 1958 the
Strategic Air Command
Strategic Air Command (SAC) was a United States Department of Defense Specified Command and a United States Air Force (USAF) Major Command responsible for command and control of the strategic bomber and intercontinental ballistic missile compon ...
issued a request for a new Class C (less than five tons, megaton-range) bomb to replace the earlier
Mk 41.
A revised version of the Mk 46 became the TX-53 in 1959. The development TX-53 warhead was apparently never tested, although an experimental TX-46 predecessor design was detonated 28 June 1958 as
Hardtack
Hardtack (or hard tack) is a type of dense Cracker (food), cracker made from flour, water, and sometimes salt. Hardtack is inexpensive and long-lasting. It is used for sustenance in the absence of perishable foods, commonly during long sea voyage ...
Oak, which detonated at a yield of 8.9
Megatons.
The Mk 53 entered production in 1962 and was built through June 1965.
About 340 bombs were built. It entered service aboard
B-47 Stratojet
The Boeing B-47 Stratojet (Boeing company designation Model 450) is a retired American long- range, six-engined, turbojet-powered strategic bomber designed to fly at high subsonic speed and at high altitude to avoid enemy interceptor aircraft ...
,
B-52G Stratofortress
The Boeing B-52 Stratofortress is an American long-range, subsonic aircraft, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the ...
,
and
B-58 Hustler
The Convair B-58 Hustler, designed and produced by American aircraft manufacturer Convair, was the first operational bomber capable of Mach 2 flight.
The B-58 was developed during the 1950s for the United States Air Force (USAF) Strategic Air ...
bomber aircraft
A bomber is a military combat aircraft that utilizes
air-to-ground weaponry to drop bombs, launch torpedoes, or deploy air-launched cruise missiles.
There are two major classifications of bomber: strategic and tactical. Strategic bombing is d ...
in the mid-1960s. From 1968 it was redesignated B53.
Some early versions of the bomb were dismantled beginning in 1967. After the Titan II program ended, the remaining W-53s were retired in the late 1980s. The B53 was retired in 1986, but in 1988 50 units were brought back into service and received the B53 Mod 1 safety upgrade so the air force could cover certain targets previously covered by Titan II.
These weapons remained in the active stockpile until the deployment of the
B61-11 in 1997. At that point the obsolete B53s were slated for immediate disassembly; however, the process of disassembling the units was greatly hampered by safety concerns as well as a lack of resources.
In 2010 authorization was given to disassemble the 50 bombs at the
Pantex plant in Texas.
The process of dismantling the last remaining B53 bomb in the stockpile was completed in 2011.
Specifications
The B53 was long with a diameter of . It weighed , including the W53 warhead, the
parachute
A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...
system and the honeycomb aluminum
nose cone
A nose cone is the conically shaped forwardmost section of a rocket, guided missile or aircraft, designed to modulate oncoming fluid dynamics, airflow behaviors and minimize aerodynamic drag. Nose cones are also designed for submerged wat ...
to enable the bomb to survive
laydown delivery. It had five parachutes:
one
pilot chute
A pilot chute is a small auxiliary parachute used to deploy the main or reserve parachute. The pilot chute is connected by a bridle to the deployment bag containing the parachute. Pilot chutes are a critical component of all modern skydiving and B ...
, one extractor chute, and three main chutes. Chute deployment depends on delivery mode, with the main chutes used only for laydown delivery. For free-fall delivery, the entire system was jettisoned.
The W53 warhead of the B53 used
oralloy (highly enriched
uranium
Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...
) instead of
plutonium
Plutonium is a chemical element; it has symbol Pu and atomic number 94. It is a silvery-gray actinide metal that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four ...
for fission, with a mix of
lithium
Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...
-6
deuteride fuel for fusion. The
explosive lens
An explosive lens—as used, for example, in nuclear weapons—is a highly specialized shaped charge. In general, it is a device composed of several explosive charges. These charges are arranged and formed with the intent to control the sha ...
comprised a mixture of
RDX
RDX (Research Department Explosive or Royal Demolition Explosive) or hexogen, among other names, is an organic compound with the formula (CH2N2O2)3. It is white, odorless, and tasteless, widely used as an explosive. Chemically, it is classified ...
and
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 ...
, which was not
insensitive. Two variants were made: the B53-Y1, a "dirty" weapon using a U-238-encased secondary, and the B53-Y2 "clean" version with a non-fissile (
lead
Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...
or
tungsten
Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...
) secondary casing. The explosive yield for the Y1 version was declassified in 2014 as being 9 Mt.
In 1988, some B53s were upgraded to the B53 Mod 1 (B53-1) variant to improve weapon safety and to provide compatibility with the G/H variants of the B52 bomber. During this upgrade the weapon lost full-fuzing capability, retaining only the laydown fuzing mode. The B53-1 had a selectable laydown time of 30 to 240 seconds in 30 second increments.
Role
It was intended as a
bunker buster
A bunker buster is a type of munition that is designed to penetrate hardened targets or targets buried deep underground, such as military bunkers.
Armor piercing shells Germany
Röchling shells were bunker-busting artillery shells, developed ...
weapon, using a surface blast after laydown deployment to transmit a
shock wave
In physics, a shock wave (also spelled shockwave), or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a me ...
through the earth to collapse its target. Attacks against the Soviet deep underground leadership shelters in the
Chekhov
Anton Pavlovich Chekhov (; ; 29 January 1860 – 15 July 1904) was a Russian playwright and short-story writer, widely considered to be one of the greatest writers of all time. His career as a playwright produced four classics, and his b ...
/
Sharapovo area south of
Moscow
Moscow is the Capital city, capital and List of cities and towns in Russia by population, largest city of Russia, standing on the Moskva (river), Moskva River in Central Russia. It has a population estimated at over 13 million residents with ...
envisaged multiple B53/W53 exploding at ground level. It has since been supplanted in such roles by the earth-penetrating
B61 Mod 11
The B61 nuclear bomb is the primary thermonuclear gravity bomb in the United States Enduring Stockpile following the end of the Cold War. It is a low-to-intermediate yield strategic and tactical nuclear weapon featuring a two-stage radiation im ...
, a bomb that penetrates the surface to deliver much more of its explosive energy into the ground, and therefore needs a much smaller
yield to produce the same effects.
The B53 was intended to be retired in the 1980s, but 50 units remained in the active stockpile until the deployment of the B61-11 in 1997. At that point the obsolete B53s were slated for immediate disassembly; however, the process of disassembling the units was greatly hampered by safety concerns as well as a lack of resources.
The last remaining B53 bomb began the disassembly processes on Tuesday, 25 October 2011 at the Energy Department's
Pantex Plant.
An April 2014
GAO
Gao (or Gawgaw/Kawkaw) is a city in Mali and the capital of the Gao Region. The city is located on the River Niger, east-southeast of Timbuktu on the left bank at the junction with the Tilemsi valley.
For much of its history Gao was an imp ...
report notes that the
National Nuclear Security Administration (NNSA) is retaining canned sub-assemblies (CSAs) "associated with a certain warhead indicated as excess in the 2012 Production and Planning Directive are being retained in an indeterminate state pending a senior-level government evaluation of their use in
planetary defense against earthbound asteroids." In its FY2015 budget request, the NNSA noted that the B53 component disassembly was "delayed", leading some observers to conclude they might be the warhead CSAs being retained for potential planetary defense purposes.
W-53

The W-53 nuclear warhead of the
Titan II
The Titan II was an intercontinental ballistic missile (ICBM) developed by the Glenn L. Martin Company from the earlier Titan I missile. Titan II was originally designed and used as an ICBM, but was later adapted as a medium-lift space ...
ICBM
An intercontinental ballistic missile (ICBM) is a ballistic missile with a range (aeronautics), range greater than , primarily designed for nuclear weapons delivery (delivering one or more Thermonuclear weapon, thermonuclear warheads). Conven ...
used the same
physics package
Nuclear weapons design are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types:
# Pure fission weapons are the simplest, least technically de ...
as the B53, without the air drop-specific components like the parachute system and crushable structures in the nose and sides needed for lay-down delivery, reducing its mass to about .
The Mark-6 re-entry vehicle containing the W53 warhead was about long, in diameter and was mounted atop a spacer which was in diameter at the missile interface (compared to the missile's core diameter of ). With a yield of 9
megatons, it was the highest yield warhead ever deployed on a US missile. About 65 W53 warheads were constructed between December 1962 and December 1963.
On 19 September 1980 a fuel leak caused a Titan II to
explode within its
silo
A silo () is a structure for storing Bulk material handling, bulk materials.
Silos are commonly used for bulk storage of grain, coal, cement, carbon black, woodchips, food products and sawdust. Three types of silos are in widespread use toda ...
in
Arkansas
Arkansas ( ) is a landlocked state in the West South Central region of the Southern United States. It borders Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, Texas to the southwest, and Oklahoma ...
, throwing the W53 warhead some distance away. Due to the safety measures built into the weapon, it did not explode or release any
radioactive material
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...
. Fifty-two active missiles were deployed in silos prior to the beginning of the retirement program in October 1982.
Effects

Assuming a detonation at optimum height, a 9-megaton blast would result in a fireball with an approximate diameter. The radiated heat would be sufficient to cause lethal
burns
Burns may refer to:
Astronomy
* 2708 Burns, an asteroid
* Burns (crater), on Mercury
People
* Burns (surname), list of people and characters named Burns
** Burns (musician), Scottish record producer
Places in the United States
* Burns, ...
to any unprotected person within a radius (). Blast effects would be sufficient to collapse most residential and industrial structures within a radius (); within () virtually all above-ground structures would be destroyed and blast effects would inflict near 100% fatalities. Within a 500-
rem (5-
sievert
The sievert (symbol: SvPlease note there are two non-SI units that use the same Sv abbreviation: the sverdrup and svedberg.) is a derived unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizin ...
) dose of
ionizing radiation
Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...
would be received by the average person, sufficient to cause a 50% to 90% casualty rate independent of thermal or blast effects at this distance.
Accidents
* January 13, 1964 -
1964 Savage Mountain B-52 crash (involved two B53-0 Y1 bombs being shipped in ferry configuration)
* December 8, 1964 - USAF B-58 aircraft carrying a B53 nuclear bomb internally, and four B43 nuclear bombs externally, caught fire while taxiing after its landing gear collapsed. The B53 burned, causing contamination of the crash area. Two of the B43s caused some plutonium and uranium contamination.
* September 18–19, 1980 -
1980 Damascus Titan missile explosion (involved a Titan II missile with a W-53 warhead)
List of B53s on display
Currently, seven actual B53s are on display at the following facilities or museums.
*B53 on display in the free introduction exhibit room at the
Atomic Testing Museum,
Las Vegas, Nevada
Las Vegas, colloquially referred to as Vegas, is the most populous city in the U.S. state of Nevada and the county seat of Clark County. The Las Vegas Valley metropolitan area is the largest within the greater Mojave Desert, and second-l ...
*B53 on display at the
Wings Over the Rockies Air and Space Museum
The Wings Over the Rockies Air and Space Museum (WOTR) is located on the former Lowry Air Force Base in Denver, Colorado, United States. The museum preserves the history of Lowry AFB's operations from 1938 to 1994 in its collections, archives, an ...
at the former
Lowry AFB
Lowry Air Force Base (Lowry Field from 1938–1948) is a former United States Army Air Forces (USAAF) training base during World War II and a United States Air Force (USAF) training base during the Cold War. From 1955-1958, it served as the i ...
,
Denver
Denver ( ) is a List of municipalities in Colorado#Consolidated city and county, consolidated city and county, the List of capitals in the United States, capital and List of municipalities in Colorado, most populous city of the U.S. state of ...
,
Colorado
Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
*B53 on display at the
Grissom Air Museum at
Grissom Air Reserve Base
Grissom Air Reserve Base is a United States Air Force base, located about north of Kokomo, Indiana, Kokomo in Cass County, Indiana, Cass and Miami County, Indiana, Miami counties in Indiana. The facility was established as a U.S. Navy installa ...
, the former
Grissom AFB, in
Peru
Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...
,
Indiana
Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...
*Mark 53 casing is on display in the
Cold War
The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
Gallery at the
National Museum of the United States Air Force
The National Museum of the United States Air Force (formerly the United States Air Force Museum) is the official museum of the United States Air Force located at Wright-Patterson Air Force Base, northeast of Dayton, Ohio. The NMUSAF is ...
at
Wright-Patterson AFB
Wright-Patterson Air Force Base (WPAFB) is a United States Air Force base and census-designated place just east of Dayton, Ohio, in Greene and Montgomery counties. It includes both Wright and Patterson Fields, which were originally Wilbur Wr ...
in
Dayton, Ohio
Dayton () is a city in Montgomery County, Ohio, United States, and its county seat. It is the List of cities in Ohio, sixth-most populous city in Ohio, with a population of 137,644 at the 2020 United States census, 2020 census. The Dayton metro ...
*B53 casing in display yard of
The National Museum of Nuclear Science & History, adjacent to
Kirtland AFB
Kirtland Air Force Base is a United States Air Force base. It is located in the southeast quadrant of the Albuquerque, New Mexico, urban area, adjacent to the Albuquerque International Sunport. The base was named for the early Army aviator C ...
in
Albuquerque, New Mexico
Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...
*W-53 on display in the visitors center of the
Titan Missile Museum near
Tucson, Arizona
Tucson (; ; ) is a city in Pima County, Arizona, United States, and its county seat. It is the second-most populous city in Arizona, behind Phoenix, Arizona, Phoenix, with a population of 542,630 in the 2020 United States census. The Tucson ...
*B-53 in display yard of Freedom Museum USA in
Pampa, Texas
Pampa (from the Quechua: ''pampa'', meaning "plain") is a city in Gray County, Texas, United States. Its population was 16,867 as of the 2020 census. Pampa is the county seat of Gray County and is the principal city of the Pampa micropolita ...
*B-53 (training version) in display at the
Festung Königstein, Saxony, Germany
Notes
References
Bibliography
*
*
External links
The B-53 (Mk-53) Bomb
{{United States nuclear devices
Cold War aerial bombs of the United States
Nuclear bombs of the United States
Military equipment introduced in the 1960s
2011 disestablishments in the United States