W78
Encyclopedia
Warhead
The term warhead refers to the explosive material and detonator that is delivered by a missile, rocket, or torpedo.- Etymology :During the early development of naval torpedoes, they could be equipped with an inert payload that was intended for use during training, test firing and exercises. This...
used on most of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
LGM-30G Minuteman III
LGM-30 Minuteman
The LGM-30 Minuteman is a U.S. nuclear missile, a land-based intercontinental ballistic missile . As of 2010, the version LGM-30G Minuteman-III is the only land-based ICBM in service in the United States...
intercontinental ballistic missile
Intercontinental ballistic missile
An intercontinental ballistic missile is a ballistic missile with a long range typically designed for nuclear weapons delivery...
s (ICBMs), along with the MK-12A reentry vehicle which carried the warhead. Minuteman III's initially deployed with the older W62
W62
The W62 is an American thermonuclear warhead designed in the late 1960s and manufactured from 1970 to 1976, used on some Minuteman III ICBMs and retired in 2010....
warhead; the W78 was deployed starting in December 1979 onto 300 missiles, three warheads per missile. Declassified
Declassification
Declassification is the process of documents that formerly were classified as secret ceasing to be so restricted, often under the principle of freedom of information. Procedures for declassification vary by country...
records indicate a total of 1,083 W78s were produced.
The W78 was designed at Los Alamos National Laboratory
Los Alamos National Laboratory
Los Alamos National Laboratory is a United States Department of Energy national laboratory, managed and operated by Los Alamos National Security , located in Los Alamos, New Mexico...
starting in 1974. The design is thought to combine the secondary (fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
) stage design of older ICBM warheads such as the W50
W50 (atomic weapon)
The W-50 or W50 thermonuclear warhead was a nuclear bomb used on the MGM-31 Pershing intermediate range nuclear missile.There were two major variants produced , in three yield options .All variants were in diameter and long, weighing .The W50 used the Tsetse primary design...
with a more modern primary stage (see Teller-Ulam design
Teller-Ulam design
The Teller–Ulam design is the nuclear weapon design concept used in most of the world's nuclear weapons. It is colloquially referred to as "the secret of the hydrogen bomb" because it employs hydrogen fusion, though in most applications the bulk of its destructive energy comes from uranium fission,...
for more details).
The W78 has a publicly announced yield of 335-350 kilotons of TNT
TNT equivalent
TNT equivalent is a method of quantifying the energy released in explosions. The ton of TNT is a unit of energy equal to 4.184 gigajoules, which is approximately the amount of energy released in the detonation of one ton of TNT...
(kt).
Dimensions of the W78 are unknown, but it fits within the MK-12A reentry vehicle, which is conically shaped, 21.3 inches in diameter at its base and 71.3 inches long. The W78 is estimated to weigh 700-800 pounds.
The W78 does not use insensitive high explosives, such as TATB
TATB
TATB, or triaminotrinitrobenzene, is an aromatic explosive, based on the basic six-carbon benzene ring structure with three nitro functional groups and three amine groups attached, alternating around the ring....
, which are used in many nuclear weapons because of their high resistance to accidental detonation due to shock or fire or impact. As a result, the W78 is considered a somewhat dangerous warhead, and cannot be transported by air unless there is no other safe option.