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Operation Grapple

First British H-bomb test - Operation Grapple X Round C1, which took place over Kiritimati.
Country United Kingdom
Test site Kiritimati (Christmas Island), Kiribati; Malden Island, Kiribati
Period 1957-1958
Number of tests 9
Test type air drop, balloon
Max. yield 3 megatonnes of TNT (13 PJ)
Previous test series Operation Antler
Next test series Operation Vixen

Operation Grapple, and operations Grapple X, Grapple Y and Grapple Z, were the names of British nuclear weapons tests of very-early hydrogen bombs. These tests were carried out from 1956 until 1958 at Malden Island and Christmas Island in the Central Pacific Ocean. Nine nuclear explosions were executed during these series of nuclear weapon tests, culminating in the United Kingdom's becoming the third recognised possessor of thermonuclear weapons.[1]

All of these nuclear bombs were exploded high in the atmosphere, rather than being detonated on the ground, in order to reduce the production of nuclear fallout.

The unproven H-bomb designs being developed by British weaponeers required full-scale testing of their capabilities, hence Operation Grapple was carried out as a massive military operation in the Central Pacific, and this was the largest British military operation carried out since World War II. The preparations for Operation Grapple, including building the necessary structures on Kiritimati, began at the end of May 1956. About 1,200 civilians and servicemen were sent to Kiritimati during 1956. The first deliveries to Kiritimati were made by the troopship Devonshire, which steamed to the Central Pacific from East Asia and took construction troops aboard at Fiji. These men had flown there from the UK on commercial airliners. The first project on Kiritimati, which was finished in October, was to rebuild the main runway at the airport . The majority of troops and civilians were then flown in from the UK, via Canada and Hawaii, in chartered airliners. The original troops began to be flown out in mid-1957.

While Kiritimati was the main base, three other islands supported Operation Grapple. The area around Malden Island, located about 330 kilometres south of Kiritimati, was to be the site for the bomber-dropped tests, and Penrhyn Island, 320 kilometres farther south was used as a technical monitoring site and as a weather station. Air deliveries of cargo for Operation Grapple were generally sent via Hickam Air Force Base (of the United States Air Force) in the American Territory of Hawaii, where a transport group of the Royal Air Force was assigned.

Seaborne supplies for Operation Grapple were usually shipped via Australia or New Zealand, using freighters of the Royal Fleet Auxiliary (RFA). The British Royal Navy built a seawater processing plant on Kiritimati early during Operation Grapple, and this provided freshwater for drinking and cooking, and semi-saline water for bathing.


  • Summary 1
  • Individual explosions 2
  • Grapple X 3
  • Grapple Y 4
  • Grapple Z 5
  • Cooperation with the United States 6
  • Health effects 7
  • Environmental effects 8
  • See also 9
  • Notes 10
  • References 11
  • External links 12


United Kingdom's Grapple series tests and detonations
Name [note 1] Date time (UT) Local time zone [note 2][2] Location [note 3] Elevation + height [note 4] Delivery, [note 5]
Purpose [note 6]
Device [note 7] Yield [note 8] Fallout [note 9] References Notes
1/Short Granite 15 May 1957 19:37:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Malden Island, Kiribati ~ 3 m (9.8 ft) + 2,200 m (7,200 ft) air drop,
weapons development
Green Granite Small "Tom + Dick" 300 kt [3][4][5] Attempted thermonuke, most of output from the secondary, but disappointing small yield, overall.
2/Orange Herald 31 May 1957 19:41:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Malden Island, Kiribati ~ 3 m (9.8 ft) + 2,400 m (7,900 ft) air drop,
weapons development
720 kt [3][4][5] Small Orange Herald design, attempt to get a one megaton explosion for political reasons, but didn't quite get there.
3/Purple Granite 19 June 1957 19:40:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Malden Island, Kiribati ~ 3 m (9.8 ft) + 2,400 m (7,900 ft) air drop,
weapons development
200 kt [3][4][5] Possibly a large Orange Herald design.
X/Round C 8 November 1957 17:47:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Kiritimati (Christmas Island), Kiribati 3 m (9.8 ft) + 2,250 m (7,380 ft) air drop,
weapons development
1.8 Mt [4][5] First successful British thermonuclear bomb.
Y 28 April 1958 19:05:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Kiritimati (Christmas Island), Kiribati 3 m (9.8 ft) + 2,350 m (7,710 ft) air drop,
weapons development
3 Mt [4][5]
Z1/Pennant 2 22 August 1958 18:00:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Kiritimati (Christmas Island), Kiribati 3 m (9.8 ft) + 450 m (1,480 ft) balloon,
weapons development
24 kt [4][5]
Z2/Flagpole 1 2 September 1958 17:24:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Kiritimati (Christmas Island), Kiribati 3 m (9.8 ft) + 2,850 m (9,350 ft) air drop,
weapons development
1 Mt [4][5]
Z3/Halliard 1 11 September 1958 17:49:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Kiritimati (Christmas Island), Kiribati 3 m (9.8 ft) + 2,650 m (8,690 ft) air drop,
weapons development
800 kt [4][5]
Z4/Burgee 2 23 September 1958 18:00:?? LINT (-10.67 hrs)
(-10 hrs, 40 min)
Kiritimati (Christmas Island), Kiribati 3 m (9.8 ft) + 450 m (1,480 ft) balloon,
weapons development
25 kt [4][5]
  1. ^ The US, France and Great Britain have code-named their test events, while the USSR and China did not, and therefore have only test numbers (with some exceptions – Soviet peaceful explosions were named). Word translations into English in parentheses unless the name is a proper noun. A dash followed by a number indicates a member of a salvo event. The US also sometimes named the individual explosions in such a salvo test, which results in "name1 – 1(with name2)". If test is canceled or aborted, then the row data like date and location discloses the intended plans, where known.
  2. ^ To convert the UT time into standard local, add the number of hours in parentheses to the UT time; for local daylight saving time, add one additional hour. If the result is earlier than 00:00, add 24 hours and subtract 1 from the day; if it is 24:00 or later, subtract 24 hours and add 1 to the day. All historical timezone data are derived from here:
  3. ^ Rough place name and a latitude/longitude reference; for rocket-carried tests, the launch location is specified before the detonation location, if known. Some locations are extremely accurate; others (like airdrops and space blasts) may be quite inaccurate. "~" indicates a likely pro-forma rough location, shared with other tests in that same area.
  4. ^ Elevation is the ground level at the point directly below the explosion relative to sea level; height is the additional distance added or subtracted by tower, balloon, shaft, tunnel, air drop or other contrivance. For rocket bursts the ground level is "N/A". In some cases it is not clear if the height is absolute or relative to ground, for example, Plumbbob/John. No number or units indicates the value is unknown, while "0" means zero. Sorting on this column is by elevation and height added together.
  5. ^ Atmospheric, airdrop, balloon, gun, cruise missile, rocket, surface, tower, and barge are all disallowed by the Partial Nuclear Test Ban Treaty. Sealed shaft and tunnel are underground, and remained useful under the PTBT. Intentional cratering tests are borderline; they occurred under the treaty, were sometimes protested, and generally overlooked if the test was declared to be a peaceful use.
  6. ^ Include weapons development, weapon effects, safety test, transport safety test, war, science, joint verification and industrial/peaceful, which may be further broken down.
  7. ^ Designations for test items where known, "?" indicates some uncertainty about the preceding value, nicknames for particular devices in quotes. This category of information is often not officially disclosed.
  8. ^ Estimated energy yield in tons, kilotons, and megatons. A ton of TNT equivalent is defined as 4.184 gigajoules (1 gigacalorie).
  9. ^ Radioactive emission to the atmosphere aside from prompt neutrons, where known. The measured species is only iodine-131 if mentioned, otherwise it is all species. No entry means unknown, probably none if underground and "all" if not; otherwise notation for whether measured on the site only or off the site, where known, and the measured amount of radioactivity released.

Individual explosions

Grapple 1

The first trial was Grapple, also known as Grapple 1. All of these nuclear bombs were dropped and detonated over Malden Island. The first test of this trial was code-named Short Granite. It was a two-staged nuclear weapon that had a predicted yield of about one megaton. This bomb was dropped by a Vickers Valiant bomber XD818,[6] piloted by Kenneth Hubbard, off the shore of Malden Island on 15 May 1957.

Weighing about 4,550 kilograms, this bomb exploded with a power of about 300 kilotons, a yield far below its designed capability. Despite this problem, the British government hailed this test as a successful thermonuclear explosion, and the government announced to the world that the UK had become a thermonuclear power. While the results of this test were disappointing, the British learned much about radiation implosion in H-bombs.

The Orange Herald test on 31 May 1957, as reported by Universal International Newsreel

The next test was Orange Herald. This was a large fission bomb which was hoped to arm a future ballistic missile. The bomb was dropped and detonated by a Valiant bomber on 31 May 1957. It exploded with a force of about 720 kilotons. The yield was the largest ever achieved by similar bomb designs. This bomb was hailed by the government as a new type of hydrogen bomb and the fact that it was a fission bomb was kept secret by the government until the end of the Cold War. A 400 kiloton very-large atomic bomb code-named Green Grass was derived from Orange Herald, and it was deployed during the period before an H-bomb became available. The last shot of Grapple was Purple Granite. This was a last minute addition to the operation and was hoped to give an improved yield over Short Granite. The bomb was detonated on 19 June 1957, with a 150 kiloton yield.

There were other designs that were not tested: Green Bamboo was a single stage thermonuclear bomb similar to the Soviet Joe-4, and Orange Herald (large) was a "political bomb": a large fission bomb that was not suitable for use as a weapon but was certain to give a high yield ensuring that Britain would not appear as a failed nuclear power.

The two Granites and Green Bamboo were designed to achieve high yields by using the Li-6 D/U-238 cycle rather than the large-scale fusion of deuterium achieved at Grapple-Y.

Grapple X

The East Point balloon anchor on Kiribati Island. Bombs were hoisted by balloons from here.

Following the disappointing results of the first Grapple trial, Grapple X was conducted at Kiritimati. For Grapple X, the bombs were exploded over Kiritimati instead of over Malden Island to save time and money. With the experience and knowledge gained from the first Grapple tests, the weaponeers had developed a new H-bomb design with a 50 percent more powerful fission primary stage and a simplified thermonuclear secondary. Grapple X was dropped and detonated over the southern end of Kiritimati on 8 November 1957. The two-stage thermonuclear bomb exploded with a yield of about 1.8 megatons. This was close to being the real hydrogen bomb Britain wanted, but used a relatively large quantity of (expensive) highly enriched uranium.

The explosion did some damage to the island, resulting in some demolished and damaged military buildings. This damage was due to the higher-than-expected yield of the explosion.

Grapple X was spectacularly successful, exceeding its predicted yield of one megaton by about 80 percent. The UK had become a thermonuclear power with the detonation of Grapple X.

Grapple Y

Grapple Y sought to develop a more efficient thermonuclear bomb based on the successful Grapple X design. Like Grapple X, only one detonation was conducted during Grapple Y. The bomb was detonated off Kiritimati on 28 April 1958. This bomb had an explosive yield of about 3.0 megatons, and it was the largest British nuclear weapons test ever executed anywhere.[7]

The design of Grapple Y was notably successful because much of its yield came from its thermonuclear reaction instead of from the fast fission of a heavy uranium-238 tamper - hence making it a true H-bomb, and also because its yield had been closely predicted—indicating that its designers understood what they were doing.

Grapple Z

With a nuclear testing moratorium quickly approaching, Operation Grapple Z was carried out at Kiritimati during mid-1958. This was a four-bomb test series, and the largest of the four in the Grapple series. Grapple Z sought to develop lighter nuclear warheads as well as weapons that were radiologically hardened - meaning they would not be destroyed prematurely if exposed to nuclear radiation from other nuclear explosions. Two of the Grapple Z tests were fission bombs tested for development of the primary stage of a two-stage hydrogen bomb.

The first shot, with the code name of Pendant, was detonated on 22 August 1958. Rather than being dropped from a bomber, this bomb was suspended from a string of four vertically stacked barrage balloons. The Pendant test had a yield of about 24 kilotons, and it used solid hydrogen fusion boosting using lithium deuteride.[7] The next shot, called Flagpole, was dropped by a bomber flying over Kiritimati on 2 September 1958. This bomb was a smaller version of the one exploded in Grapple Y, and it detonated with a yield of about 1.2 megatons. This test was followed by one called Halliard 1, on 11 September 1958, which was an unusual three-stage bomb with two nuclear-fission components followed by one thermonuclear stage. This bomb had its predicted yield of 800 kilotons, and it was supposedly immune to exposure from another bomb despite its not using boosting. The final test was called Burgee, on 23 September 1958, another balloon-borne test which was an atomic bomb boosted with gaseous tritium. It had a yield of about 25 kilotons.

The last bomb in the Grapple Z series was the very last nuclear explosion carried out in the atmosphere by the UK.[7] The result of it was that the weapon makers of the UK had demonstrated all of the technologies that were needed to produce a one-megaton hydrogen bomb that weighed no more than one ton (2,200 pounds), and it was also immune to premature detonation caused by nearby nuclear explosions.

Cooperation with the United States

The practical result of the British H-bomb project (in conjunction with other political events [8]) was that the United States became willing to enter into the 1958 US-UK Mutual Defence Agreement. This put an end to independent nuclear weapons development by the UK in favour of a program that was closely based on the American designs. The benefit to the UK was that this was much cheaper than developing its own designs for weapons that could be made in large numbers, and then deployed. An additional benefit was that the UK was able to buy highly enriched uranium from the US and also sell plutonium to it made in British nuclear reactors. This was a deal that was useful to both parties and also profitable for the UK.

While the thermonuclear bomb designs tested by the UK during Operation Grapple were successful, they were never serially produced. The useful effect of the British tests was to increase the quality of information that the American Atomic Energy Commission was willing to share with the UK, and also for British weapons designers to learn how to use that information successfully.

Health effects

In 2005, a

  • BNTVABritish Nuclear Test Veterans Association -
  • AWE (UK government Atomic Weapons Establishment) page on Grapple including picture of Grapple Y mushroom cloud (formerly at but now only available from
  • British Nuclear Testing footage at
  • test seriesGrapplePhotos taken by the journalist "Cassandra" during the
  • Photos and eye-witness accounts
  • Valiant XD818 is preserved at the RAF Museum
  • Britain's Nuclear Weapons Program at the Atomic Forum (includes pictures and videos)
  • are receiving War Disablement Pension (2006)Operation GrappleParliamentary Reply states that 106 New Zealand veterans from

External links

  • Britain's Cold War Super Weapons, Channel 4, 2005-04-24 (note: this has a number of factual errors)
  • House of Commons, enquiry for Nuclear Test Veterans, 2002-09-04
  • Arnold, Lorna, Britain and the H-Bomb


  1. ^ Video: British H-Bomb Fired As Debate On Atom Test Ban Rages, 1957/06/03 (1957).  
  2. ^ "Timezone Historical Database". Retrieved 8 March 2014. 
  3. ^ a b c Andryushin, L. A.; Voloshin, N. P.; Ilkaev, R. I.; Matushchenko, A. M.; Ryabev, L. D.; Strukov, V. G.; Chernyshev, A. K.; Yudin, Yu. A. (1999). Catalog of Worldwide Nuclear Testing (Technical report). Sarov, Russia: RFNC-VNIIEF. Retrieved 18 December 2013. 
  4. ^ a b c d e f g h i Norris, Robert S.; Burrows, Andrew S.; Fieldhouse, Richard W. (1994). Nuclear Weapons Databook, Vol. 5: British, French, and Chinese Nuclear Weapons. Boulder, CO: Westview Press. 
  5. ^ a b c d e f g h i Yang, Xiaoping; North, Robert; Romney, Carl (August 2000). CMR Nuclear Explosion Database (Revision 3) (Technical report). SMDC Monitoring Research. 
  6. ^
  7. ^ a b c Arnold,Lorna, Britain and the H-Bomb, (New York: Palgrave Publishers Ltd., 2001), 174.
  8. ^ Other political considerations from the old version of the AWE website: Dwight D. Eisenhower wanted better relations with the United Kingdom after the Suez Crisis and he was not happy with the morality of the McMahon Act.
  9. ^ Johnston, Martin (23 September 2005). "Genetic damage found among N-test veterans".  
  10. ^ Johnston, Martin (3 April 2006). "Nuclear test veterans call for better Government help".  
  11. ^ "Nuclear test study could help sailors' lawsuit - lawyer".  
  12. ^ MOD datasheet 5
  13. ^ MOD datasheet 1
  14. ^ Analysis of data in The Lancet and The BMJ
  15. ^ Bowcott, Owen (14 March 2012). "Pacific atomic test survivors cannot sue Ministry of Defence".  
  16. ^ ” Meteorogical records , airflow and other factors affecting local fall out from British nuclear tests at Christmas Island in 1957 – 58 .” by Chris Busby and Dai Williams, October 2010


See also

The effects of radioactive fallout from the Grapple tests were being researched coarsely by a 2010 British Government study that concluded the fallout would not reach concentrations that could affect the surrounding nature considerably.[16]

Environmental effects

In March 2012, a group of 1,011 British ex-servicemen were denied permission to sue the UK Ministry of Defence by the Supreme Court, on the grounds that too much time had elapsed since they became aware of their medical conditions, under the terms of the Limitation Act 1980.[15]

The Ministry of Defence maintains that few people were exposed to any radiation or contamination at all, and that studies had shown little or no health effects.[12][13] An analysis of illnesses in veterans of Grapple and other weapons tests produced statistics that are hard to interpret. The veterans showed rates of illness that were slightly higher than the control group, but the control group had lower rates of illness than the population as a whole while the veterans had rates that were about the same. Neither of these results has a clear explanation.[14] Reliable statistical analysis of the data is difficult because the samples are fairly small and incomplete.


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