Operation Grapple was a series of tests carried out by the UK to develop a working Thermonuclear bomb, more commonly known as a H-Bomb.
Previously UK nuclear bomb tests had been carried out in Australia. However due to issues of contamination caused by these tests etc., plus the fact that the H-bombs were expected to produce more fallout, a decision was made to conduct the tests in a more remote location.
Therefore, 2 islands in the Pacific Ocean were selected. Christmas Island, which would be the base for the test force, and Malden Island, located some 360 miles south would be the test site.
Commencing in 1956 a base was constructed on Christmas Island. It featured a new 7,000 foot runway, plus an additional 25 miles of new roads, together with buildings and housing (mostly tents) for the 1200 personnel. This was sited on the northern end of the Island
Number of tests and locations
However, after the first round of tests, to save time and money, the second round of tests would be carried out, offshore of Christmas Island.
In total 9 tests were conducted, all air burst to reduce the risk of fallout. For 7 of the tests, the device was deployed from Vickers Valiant bombers. The other 2 were tethered from barrage balloons.
Task Force 308 (Operation Grapple)
A Tri-Service task force: “Task Force 308” was formed, and the RAF element, No.160 wing was formed at RAF Hornchurch in the spring of 1957.
This Task Force was composed from the following units:
- No.206 and No.240 Squadrons RAF provided Avro Shackleton Mk2s for Maritime Search and Reconnaissance.
- No.49 Squadron RAF provided Vickers Valiant bombers for the drop tests.
- No.76 Squadron RAF provided 6 EE Canberra B.6 for radiation sampling.
- No.100 Squadron provided 4 EE Canberra PR.7 for long range weather reconnaissance.
- No.58 Squadron provided to EE Canberra PR.7 to fly radioactive samples back to the UK.
Operation Grapple 1
15 May 1957, codename ‘Short Granite’, Valiant XD818 dropped a 1 megaton device which exploded 8,000 feet above Malden Island. Only a 300 kiloton yield was achieved from the device.
31 May 1957 codename ‘Orange Herald’, this was actually a fission bomb, which detonated with a 720 kiloton yield.
19 June 1957, codename ‘Purple Granite’, another poor yield of 200 kilotons.
The Grapple 1 tests were a disappointment to the British government as the yields were much lower than expected. However, much had been learned and changes made for the next round of testing.
It was decided to do another set of testing as part of Grapple X, Grapple Y and Grapple Z.
Operation Grapple X
8 November 1957, Valiant XD824 dropped a device offshore of Christmas Island, the yield was much bigger than expected at 1.8 megatons. The blast caused some structural damage to the base on the north of the island, 24 miles away.
Operation Grapple Y
28 April 1958, Valiant XD825 dropped the UKs first true Hydrogen bomb, the yield was 2 megatons.
operation Grapple Z
Grapple Z was a series of 4 tests of lower yields, 2 tests were air dropped and 2 were balloon deployed.
22 August 1958, codename ‘Pendant’, the device was suspended under 4 barrage balloons, a yield of 24 kilotons was recorded.
2 September 1958, codename ‘Flagpole’, dropped by Valiant XD822, a yield of 1.2 megatons was achieved.
11 September 1958, codename ‘Halliard 1’, dropped by Valiant XD827, a yield of 800 kilotons was achieved.
23 September 1958, codename ‘Burgee’, the device was suspended under barrage balloons and yielded 25 kilotons. This was the UKs last ever atmospheric nuclear test.
After the tests
Britain never developed any H-bombs from the Grapple designs. However the later Green Grass atomic fission bomb was developed from the ‘Orange Herald’ fission device.
Another benefit from the testing, is that the USA realised that it was time to start sharing nuclear weapon technology with the UK. This benefited both sides, as the USA soon realised that the UK was ahead in some areas such as electronics and circuitry for thermonuclear weapons.
The Aircraft (images not to scale)
Royal Air Force Vickers Valiant, No 49 Squadron.
Christmas Island, now called Kiritimati