Orange Herald was a British
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...
, tested on 31 May 1957. At the time it was reported as an
H-bomb
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 ...
, although in fact it was a large
boosted fission weapon
A boosted fission weapon usually refers to a type of nuclear bomb that uses a small amount of fusion fuel to increase the rate, and thus yield, of a fission reaction. The neutrons released by the fusion reactions add to the neutrons released du ...
and remains to date, the largest fission device ever detonated.
Technical
![Orange Herald warhead](https://upload.wikimedia.org/wikipedia/commons/b/bd/Orange_Herald_warhead.jpg)
Orange Herald was a fusion boosted British
fission nuclear weapon (called a core-boosted device by the British), comprising a
U-235
Uranium-235 (235U or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists ...
core containing a small amount of lithium deuteride (
LiD
A lid, also known as a cover, is part of a container, and serves as the closure or seal, usually one that completely closes the object. Lids can be placed on small containers such as tubs as well as larger lids for open-head pails and drums. S ...
). 'Herald' was suitable for mounting on a missile, utilizing 117 kg of U-235. However, Britain's annual production of U-235 was only 120 kg at this time, which would have made such weapons rare and very expensive.
[The Real Meaning of the Words: A Very Pedantic Guide to British Nuclear Weapons Codenames](_blank)
/ref>
Two versions were designed - an "Orange Herald Large" with an overall diameter of 39 inches (1.0 m), and an "Orange Herald Small" with overall diameter of 30 inches (0.75 m). The difference between the two was in the size of the high explosives; the fissile cores were similar. Orange Herald Small was intended as a warhead for a ballistic missile. Orange Herald Large was designed as a device which would have the most certainty to give a yield in the megaton range. However, due to its size it was not suited as a warhead for the ballistic missile and was more of an insurance which could be used if other devices failed to achieve the desired yield.
The Orange Herald Small version was tested once, yielding 720 kt of explosive power on 31 May 1957, during the Grapple 2/Orange Herald tests on Malden Island
Malden Island, sometimes called Independence Island in the 19th century, is a low, arid, uninhabited atoll in the central Pacific Ocean, about in area. It is one of the Line Islands belonging to the Republic of Kiribati. The lagoon is entir ...
in the Pacific.[British Nuclear Testing](_blank)
Carey Sublette, a
nuclearweaponarchive.org
Accessed 2009-04-28 Orange Herald remains the largest fission device ever tested.
It is thought that the fusion boosting failed to increase the yield. A higher compression but smaller fission pit American weapon, the Mark 18 Super Oralloy Bomb, had a yield of 500 kilotons from a pit with slightly over 60 kilograms of highly enriched uranium
Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U ...
, around 8 kilotons per kilogram of uranium, about the practical maximum 50% fission yield efficiency for very large or very highly boosted fission weapon
A boosted fission weapon usually refers to a type of nuclear bomb that uses a small amount of fusion fuel to increase the rate, and thus yield, of a fission reaction. The neutrons released by the fusion reactions add to the neutrons released du ...
s. Even with less compression, the larger 117 kg pit of HEU in the Orange Herald Small should have had a roughly similar efficiency, but the observed 720 kiloton yield equals only just over 6 kilotons per kilogram of uranium.
Orange Herald was the first British nuclear device to use an external neutron source.
History
Britain rushed the development of these predicted-megaton
Megaton may refer to:
* A million tons
* Megaton TNT equivalent, explosive energy equal to 4.184 petajoules
* megatonne, a million tonnes, SI unit of mass
Other uses
* Olivier Megaton (born 1965), French film director, writer and editor
* ''Me ...
class weapons because in 1955 it seemed that atmospheric testing could soon be outlawed by treaty. As a result, the UK wanted to demonstrate its ability to manufacture megaton class weapons by proof-testing them before any legal prohibitions were in place. According to an article in ''New Scientist
''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publishe ...
'', Prime Minister Harold Macmillan
Maurice Harold Macmillan, 1st Earl of Stockton, (10 February 1894 – 29 December 1986) was a British Conservative statesman and politician who was Prime Minister of the United Kingdom from 1957 to 1963. Caricatured as "Supermac", he ...
was also hoping to convince the US to change the McMahon Act
The Atomic Energy Act of 1946 (McMahon Act) determined how the United States would control and manage the nuclear technology it had jointly developed with its World War II allies, the United Kingdom and Canada. Most significantly, the Act ruled ...
, which prohibited sharing information even with the British, by demonstrating that the UK had the technology to make a thermonuclear weapon (an H-bomb), and he put William Penney
William George Penney, Baron Penney, (24 June 19093 March 1991) was an English mathematician and professor of mathematical physics at the Imperial College London and later the rector of Imperial College London. He had a leading role in the d ...
, a British professor who had worked in the Manhattan Project
The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons. It was led by the United States with the support of the United Kingdom and Canada. From 1942 to 1946, the project w ...
, in charge of developing this bomb. In this the test of the Orange Herald was successful.
It is believed by some that the large requirements of tritium
Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus o ...
that Orange Herald needed (actually it contained only a small amount of thermonuclear material) was a major cause of the Windscale fire
The Windscale fire of 10 October 1957 was the worst nuclear accident in the United Kingdom's history, and one of the worst in the world, ranked in severity at level 5 out of a possible 7 on the International Nuclear Event Scale. The fire was in ...
. It was unpopular with the scientists who worked on the project. One of the workers in the British nuclear program, Dr. Bryan Taylor, is quoted as saying "I thought that Orange Herald was a stupid device. It wasn't elegant, it couldn't be developed any further, it was a dead end design. And it consumed an enormous amount of very expensive fissile material".[Windscale. Britain's biggest nuclear disaster (2007, BBC)](_blank)
/ref> This is the thesis of a BBC documentary on the topic of the fire, ''Windscale: Britain’s Biggest Nuclear Disaster''.
See also
* Rainbow Code
The Rainbow Codes were a series of code names used to disguise the nature of various British military research projects. They were mainly used by the Ministry of Supply from the end of the Second World War until 1958, when the ministry was broke ...
* Windscale fire
The Windscale fire of 10 October 1957 was the worst nuclear accident in the United Kingdom's history, and one of the worst in the world, ranked in severity at level 5 out of a possible 7 on the International Nuclear Event Scale. The fire was in ...
* Mark 18 nuclear bomb The Mark 18 nuclear bomb, also known as the SOB or Super Oralloy Bomb, was an American nuclear bomb design which was the highest yield fission bomb produced by the US. The Mark 18 had a design yield of 500 kilotons. Noted nuclear weapon designer ...
* Ivy King
Ivy King was the largest pure- fission nuclear bomb ever tested by the United States. The bomb was tested during the Truman administration as part of Operation Ivy. This series of tests involved the development of very powerful nuclear weapons i ...
Notes
External links
Colour video footage of the Orange Herald detonation
Aircrew member's account of dropping Orange Herald
References
*
{{Strategic nuclear weapon systems of the United Kingdom
Nuclear bombs of the United Kingdom
Weapons of the Cold War
Nuclear weapons of the United Kingdom
Articles containing video clips
May 1957 events in Oceania