The W78 is an American
thermonuclear warhead
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 lo ...
with an estimated yield of , deployed on the
LGM-30G Minuteman III intercontinental ballistic missile
An intercontinental ballistic missile (ICBM) is a ballistic missile with a range greater than , primarily designed for nuclear weapons delivery (delivering one or more thermonuclear warheads). Conventional, chemical, and biological weapo ...
(ICBM) and housed in the Mark 12A
reentry vehicle
Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the e ...
. Minuteman III initially carried the older
W62
The W62 was an American thermonuclear warhead designed in the 1960s and manufactured from March 1970 to June 1976. Used on some Minuteman III ICBMs, it was partially replaced by the W78 starting in December 1979, and fully replaced by W87 warh ...
warhead with a yield of , but starting in December 1979 and ending in February 1982, some W62 were replaced with the W78. It is publicly estimated that 1083 warheads were manufactured.
History
The W78 was designed at
Los Alamos National Laboratory
Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
(LANL) starting in 1974. It is thought that the warhead has never been tested at full yield, with the weapon producing a "disappointing" yield shortly before the 1976
Threshold Test Ban Treaty came into force, leading to a redesign of the weapon that was not complete before the treaty came into force. This led to a dispute between LANL and
Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory (LLNL) is a federal research facility in Livermore, California, United States. The lab was originally established as the University of California Radiation Laboratory, Livermore Branch in 1952 in response ...
who estimated the weapon's yield below that of LANL. The dispute was resolved by a panel led by former LLNL director
John Foster who found in favor of LANL's yield estimate.
[
The final W62 warhead was not removed from service until March 2010.]W87
The W87 is an American thermonuclear missile warhead formerly deployed on the LGM-118A Peacekeeper ("MX") ICBM. 50 MX missiles were built, each carrying up to 10 W87 warheads in multiple independently targetable reentry vehicles (MIRV), and wer ...
warheads as the only warheads carried by Minuteman III. Downloading of the Minuteman III missile (reducing the number of warheads carried) was completed in June 2014, reducing the warheads carried by each missile from three to one.
Design
Dimensions of the W78 are unknown, but it fits within the Mark 12A reentry vehicle
Atmospheric entry is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. There are two main types of atmospheric entry: ''uncontrolled entry'', such as the e ...
which is conically shaped. The RV is in diameter at its base and long, and total warhead and reentry vehicle weight is estimated to be .[
It is speculated that the weapon combines the secondary (]fusion
Fusion, or synthesis, is the process of combining two or more distinct entities into a new whole.
Fusion may also refer to:
Science and technology Physics
*Nuclear fusion, multiple atomic nuclei combining to form one or more different atomic nucl ...
) stage design of an older warhead such as the W50, with a more modern primary stage.[
]
See also
* List of nuclear weapons
This is a list of nuclear weapons listed according to country of origin, and then by type within the states.
United States
US nuclear weapons of all types – bombs, warheads, shells, and others – are numbered in the same sequence starting wi ...
References
External links
W78 Warhead page
at nuclearweaponarchive.org
{{United States nuclear devices
Nuclear warheads of the United States
Military equipment introduced in the 1970s