Taking the Pulse:
Nuclear Warheads

The U.S. nuclear arsenal consists of some 8,400 operational warheads of 12 types.

Alterations and modifications are underway on almost all nuclear warhead types. This effort ranges from re-manufacturing of entire warheads to installment of individual components, and includes:

  • production of W88 warheads;
  • overhaul of the W76 warhead for the Trident SLBMs;
  • modernizations/alterations of various types of the B61 bomb including the planned production of primaries;
  • completing certification of the new B61-11 earth-penetrating bomb;
  • overhaul of the W87 warhead for the MX/Peacekeeper; and
  • modernizations to the B83 and the B83 Mod 1 bombs.

Many of these warheads and the fissile materials in them up are subject to a variety of tests and experiments in upcoming years. Types of tests include:

  • Hydro Tests, or hydrodynamic tests, are, according to the Deparment of Energy (DOE), "high-explosive nonuclear experiments to investigate hydrodynamic aspects of primary function up to mid to late stages of pit implosion." "Hydrodynamic" refers to the study of the motion of fluids.
  • Subcritical nuclear tests are, again according to the DOE, "scientific experiments to obtain technical information in support of DOE's responsibility to maintain the safety and reliability of the U.S. nuclear weapons stockpile without nuclear testing. They will involve chemical high explosives to generate high pressures that will be applied to nuclear weapon materials, such as plutonium." See Nevada Test Site and Subcriticals section of the Nuclear Weapons Complex page for more information.

Below is the status of operational warheads in the U.S. arsenal:


Some 384 W88 warheads are deployed on Trident II (D-5) missiles. There are approximately 400 total in the stockpile. Seven laboratory and three stockpile surveillance tests are scheduled for FY1999. All spare warheads will be used for ground and Hydro Tests, and a pit rebuild program to replace those warheads expended in surveillance will start in FY1998. Small-scale re-manufacturing is scheduled to begin at Los Alamos in FY2001. A development flight test for a remanufactured pit-warhead is scheduled for FY2000, and another development flight test is planned for FY2002 under the Replacement Warhead Project.


About 525 W87s are in the stockpile, of which 500 are operational on MX/Peacekeeper missiles. The warhead is described by the DOE as "the most modern and safe warhead in the stockpile," but the W87 is nonetheless undergoing a Life Extension Program (Alt 342) which will modify the design to enhance structural integrity of the warhead.

W87 Warheads
for the MX missile

The W87 is the first warhead in the U.S. arsenal to undergo this process. The project includes above ground experiments and flight testing. Production of replacement parts will begin in FY1999 and the first refurbished warhead is scheduled to be completed in February 1999. Eight laboratory, three flight stockpile surveillance tests, and two Retrofit Evaluation System ground tests are scheduled for FY1999, and an annual Hydro Test is planned for the following three years. After the Peacekeeper is retired, modernized W87 warheads are scheduled to be transferred to some of the Minuteman III missiles the U.S. plans to retain under the START II agreement. This redeployment is scheduled to begin in FY2004. Rebuilding of W87 warheads intended for surveillance will resume in FY2010.


Previously deployed on Ground-Launched Cruise Missiles (GLCMs), B84 warheads are now held in storage in the inactive stockpile. Two Hydro Tests were conducted in 1991 and one in 1998. Another is scheduled for FY2000. Surveillance samples are planned to be retired and the DOE is currently assessing whether to maintain the warhead in the inactive stockpile.


Some 600 B63 warheads are in the arsenal, with about 480 operational on long-range bombers. Under project Alt 750, the bomb is being equipped with a new radar. An upgraded version, designated as B83 Mod 1, is scheduled to begin production in FY1999. Ten laboratory and three flight tests are planned for FY1999.

A B83 after a test drop
by parachute.

Five Hydro Tests were conducted in FY1998, and annual Hydro Tests are scheduled to begin in FY2000 alternating between warheads from the inactive and active stockpile. A new design neutron generator is scheduled to begin production in FY2013.


Some 400 W80-1/ALCM warheads on Air-Launched Cruise Missiles (ALCMs) are earmarked for delivery by B-52H bombers. ALCMs are being converted to conventional missions and about 940 are in storage with their warheads removed.

For this warhead and the two W80 warheads below, planning is underway to replace the neutron generator, with production scheduled to commence in late 2004. Six laboratory, six flight, and one Hydro Test are scheduled for FY1999.


ACM in flight

Approximately 400 W80-1/ACM warheads in the operational arsenal are deployed on Advanced Cruise Missiles (ACMs) and assigned to long-range bombers. These warheads were originally deployed on ALCMs. The ACM first flew in 1985. It is approximately 20 feet long, 10 feet wide, and weighs in the neighborhood of 3,700 pounds.Its range is purported to be approximately 1,800 miles.


Approximately 320 W80-0/SCLM warheads on Submarine-Launched Cruise Missiles (SCLMs) are in the operational arsenal for deployment on submarines. These are stored at Yorktown Naval Weapon Station, Virginia, and Bangor, Washington. The SLCM, also known as the Tomahawk, is a long-range cruise missile that can be used against surface ships or land targets, employing conventional or nuclear warheads.

Tomahawk SLCM

The recent US attacks on Afghanistan and Sudan were carried out with conventional Tomahawks. The missile entered submarine service in1983. Tomahawk missiles can be launched from standard 21-inch torpedo tubes on all submarines and, in the later Los Angeles (688I) class submarines, from vertical-launch tubes in the submarine's bow.


W78 Warheads on
Minuteman III nose

About 915 W78 warheads are deployed on 300 Minuteman III missiles. New reservoirs and neutron generators are planned to modernize the warhead and improve performance. A Joint Life Extension Study will be completed in FY1999 to determine options for extending the life of the W78 for the enduring stockpile. Eight laboratory tests and three flight tests are scheduled for FY1999, and a limited Hydro Test series is currently under development with the first explosion planned for FY2001.


Some 3,072 W76 warheads are on 384 Trident I C-4 and Trident II D-5 missiles, with a total of 3,200 in the stockpile. These warheads began Dual Revalidation in FY1996. The Department of Energy reported in March 1998 that it was half way through the project. Completion is scheduled for FY1999. The project is a robust peer review of the warhead's military characteristics, conducted by two independent review teams from the nuclear labs, assessing and evaluating its performance against revalidated military requirements. Three of six hydrodynamic tests were conducted in 1997 and six of 15 Arming, Fuzing and Firing systems were tested to the original production specifications. The major system tests are scheduled to take place in FY1998 and FY1999. The result will provide a modern baseline of the weapon, an evaluation of its current performance in the arsenal, and a new generation of scientists and personnel trained in its operation to ensure the warhead can remain a reliable part of the enduring nuclear arsenal well into the 21st century. Furthermore, under program Alt 317, the warhead is being refitted with a new neutron generator to improve performance. Production is scheduled to begin in 1999. Eight laboratory tests and three flight stockpile surveillance tests are planned for FY1999. A Hydro Test is proposed for FY2000.


Approximately 610 W62 warheads are deployed on 200 Minuteman III missiles. As recent as in 1994, the Pentagon planned to retire W62 warheads in 2003. The warheads are expected to be replaced by W87s from the MX/Peacekeeper when the START II treaty is implemented. The DOE is evaluating whether to extend the life of the W62 for service in the enduring stockpile. Nine laboratory and two flight tests are scheduled for FY1999, and three Hydro Tests will be conducted in the period 1998-2000.


Some 300 B61-7 are in the operational stockpile. Another 310 are in storage. Approximately 50 were converted to earth-penetrating missions as the B61-11 bomb. An improved 9S actuator is being installed as part of a Limited Life Component Exchange project (Alt 336), and a new radar is being installed.

For both the B61-7 and the B61-11 below, seven laboratory and four flight tests are scheduled during FY1999. A Hydro Test is planned for FY2001. A new primary for the B61-7/11 bombs will begin production in late 2002.


About 50 B61-11 bombs are in the operational stockpile. This weapon is the newest in the US arsenal. First originated in 1993, the Mod 11 is designed as a "bunker buster" - capable of attacking hardened targets underground. The B61-11 is a replacement for the B53, which was assigned the bunker buster role because of its large yield. The Mod 11 is designed to penetrate targets before exploding, and thus in theory does not need as large a yield to fulfil its mission.

A B-2 bomber
drops a B61-11.

Conversion to full operational status of the B61-11 continues at Whiteman AFB, Missouri, and certification activities are expected to be completed in 1998 for standard stockpile acceptance in December 1998. See the B61-7 above for the Mod 11 test schedule.


There are approximately 750 B61-4/5/10 warheads for use on F-15E, F-16, and F-117 aircraft. Several alterations are underway on the B61, including: Alt 335, which installs a Trajectory Sensing Signal Generator; Alt 336, which installs a new CF3087 cable; and Alt 339, which installs a Multiple Code Coded Switch Encryption Translator. A new nose is under development to equip the bomb with a modern radar to maintain system performance. Production is scheduled to begin in late 2002. During FY1999, 11 laboratory and 4 flight tests are scheduled, and the first in a series of biannual Hydrodynamic test is planned for FY2001. Development of a new primary is scheduled for FY2011 with production to begin in FY2012.

New warheads

At the nuclear laboratories, warhead development efforts continue, including a replacement warhead for the Trident II D-5 (Mk5) reentry vehicle, a stand-off glide bomb version (BIOS) of the B61-11 bomb, and several classified projects.

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