Designation System     Courtesy of: Andreas Parsch - Webmaster of http://www.designation-systems.net/W-76 Warhead

All U.S. nuclear weapons (missile warheads, free-fall bombs, artillery shells, etc.) are numbered in a single, consecutive series. The numbers are assigned by the organization controlling the design and manufacture of nuclear weapons. From 1946 to 1974, this was the Atomic Energy Commission (AEC). In 1974, the AEC was abolished and its tasks being taken over by the newly formed Nuclear Regulatory Commission. In 1977, the Department of Energy (DOE) was founded and took over, among many other things, the responsibility for nuclear weapons.

When designating nuclear weapons, a variety of prefixes and suffixes are used with the numbers. However, I don't have any official, first-hand source describing or regulating their use. The following prefixes were used at least once:

• XW - Warhead in the development and test phase
• W - Warhead (production)
• Mark (MK, Mk) - Bomb (until 1968)
• B - Bomb (after 1968)
• TX - "Test Experimental" (prototype bomb or warhead)
• EC - "Emergency Capability" (bomb prototype design stockpiled in very limited numbers)
• S - Artillery shell (rarely used)
• BA - "Basic Assembly" (used only for bombs specially adapted to the B-58's pod)

The first four designs used roman numerals, but this was soon changed to arabic numerals with the MK-IV/MK-4. A dash is usually written between the prefix and the number. In newer references, however, the dash is frequently omitted. Especially the reference to bombs as Bn instead of B-n is quite common, presumably to avoid confusion with US Air Force bomber designations. The warhead (i.e. the nuclear package) of a free-fall bomb always retained its W designation, using the same number as the bomb itself. E.g. the nuclear components of the MK-28 bomb were known as W-28 (in the strictest sense, the MK nomenclature applied only to the non-nuclear bomb components).

Suffixes are used to designate variants of a weapon. The basic suffix is a "Mod" designator. This is used in the same way as in the US Navy's MARK/MOD Nomenclature System, i.e. the first version is designated "Mod 0", followed by "Mod 1", etc. The Mod suffix is often abbreviated to a dash and a number, e.g. B61-11 or W80-1. Different yield options for a weapon can be indicated by a Yn (n = 1, 2, ...) designator immediately behind the number. Of course, Y and Mod suffixes can be combined, as in W-39Y1 Mod 2. Modifications of bomb and warhead prototypes were often indicated by a -Xn (n = 1, 2, ...) suffix, as in TX-7-X1. If an -Xn design was put into production, the -Xn usually became a Mod number (e.g. TX-7-X1 became MK-7 Mod 1).

Courtesy of: Andreas Parsch - Webmaster of http://www.designation-systems.net/

Last updated 3 April 1997     

The Mk/B-53 is the oldest and highest yield nuclear weapon in the U.S. arsenal. It is currently being removed from service as it is replaced by the B61-11.

Design Features

Two stage radiation implosion weapon

Basic warhead design the same as in the W-53 warhead deployed on the Titan-II ICBM (now out of service).

Rear portion of bomb consists of parachute system, weighing 800-900 lb. The nose is made of a frangible aluminum honeycomb "shock absorber" for laydown delivery and weighs more than 150 lb.

Characteristics of the W-53, and the Hardtack Phase I test devices, indicate that the actual warhead "physics package" is no more than 102 inches long by 36.52 inches in diameter, with a weight of ~6000 lb. The skin on the 50 inch in diameter bomb is described as "fragile", consistent with it being only a light weight structure housing a smaller diameter weapon. The added length comes primarily from the B-53 parachute system and frangible nose, the excess weight from these and the dummy body.

Although there is only one reported yield for this weapon, the two variants produced - the "dirty" Y1 and the "clean" Y2 - suggest that two different yields may exist.

Materials

Fissile material is all-oralloy (highly enriched uranium), no plutonium
Lithium-6 (95% enrichment) deuteride fusion fuel
Cyclotol or Composition B high explosive (castable RDX/TNT mixtures), not insensitive

The B53-Y1 is a "dirty" version (with a U-238 encased secondary). The B53-Y2 is a "clean" version, perhaps with a lead or tungsten secondary casing.

Delivery Method

B-52G strategic bomber (internal bomb bay)

Safeguards and Arming Features

Originally lacked modern arming and safing features, but has been given a life extension upgrade. Probably uses mechanical lock on firing system.

Fuzing and Delivery Mode

Selected on ground prior to mission.
Four fuzing options:

• Laydown delayed surface burst
• Free fall air burst
• Parachute retarded air burst
• Immediate contact surface burst

Five parachutes are used:

• three 48 ft main chutes
• one 16 ft extractor chute
• one 5 ft "pilot" chute.

The three main chutes are deployed only for laydown delivery. The entire parachute system is jettisoned for free fall delivery.

Development

Designed and developed by Los Alamos Scientific Laboratory (LASL). The Mk-53 apparently can trace a design lineage back to the very first solid-fuel radiation implosion device ever tested, the Shrimp detonated in the Castle Bravo test. The Shrimp design was weaponized into the lighter and more compact Mk-21. Later, an even smaller and lighter high yield weapon designated the Mk-46 was developed from the Mk-21. After a test failure in Operation Hardtack I, the TX-46 secondary was redesigned and generated a high yield on a retest. This revised design was assigned the designation TX-53, and developed into a deployed weapon. Although opportunity to test the production version of the Mk-53 existed during Dominic I and II, it appears that the only test of the Mk-53 design at full yield was the Hardtack I retest, before the TX/Mk-53 designation had even been assigned.

Current models are the B53-Y1 and the B53-Y2, which are "dirty" and "clean" versions. The last 50 B-53 bombs finally began retirement from active service at the beginning of 1997 (although they remain part of the enduring stockpile). The role assigned to the B-53, destroying buried command centers, is being taken over by the B61-11 ground penetrating warhead.

Deployment

Initial manufacture August 1962
Initial deployment 1962
Approximately 340 B-53 bombs were manufactured between August 1962 and June 1965 at the AEC's Burlington , Iowa final assembly plant.

Retirement of the initial model began in July 1967

In the mid-80s plans were made to retire and dismantle the B-53 and replace it with the B-83. On 5 August 1987, with 25 remaining in service, it was decided to halt retirement, and return to service another 25 that had been retired but not dismantled (the only time this has happened in the U.S.). The stated reason for this decision was to retain the ability to destroy deeply buried hard targets.

In the late 80s a life extension program for the B-53 was begun, which included upgrades to the safing equipment.

The new earth-penetrating B-61 modification, the Mod 11, began entering service in January 1997 and is replacing the B-53 in active service. Under current plans the B-53 will be retained indefinitely as part of the hedge stockpile.

65 W-53s originally deployed, now withdrawn and dismantled

The W-53, sister warhead to the B-53

Courtesy of: Andreas Parsch - Webmaster of http://www.designation-systems.net/