Operation Grapple was the name of four series of British nuclear weapons tests Testing of early atomic bombs and hydrogen bombs Attack carried out Action in 1957 and 1958 at Malden Island and Kiritimati ( Christmas Island ) in the Pacific Ocean as part of the British hydrogen bomb programme .

In the first , Grapple 1 , a version of Green Granite known as Short Granite was dropped Motion_directional from a Vickers Valiant bomber flown by Wing Commander Kenneth Hubbard .

The second test Testing was Grapple 2 , of Orange Herald .

Grapple 3 tested Testing Purple Granite , a Short Granite with some fixes .

This consisted of a single test Testing , known as Grapple X , in November 1957 .

In a third series with a single test Testing , known as Grapple Y , in April 1958 , another design was tested Testing .

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

A final series of four tests Testing in August and September 1958 , known as Grapple Z , tested Testing techniques for boosting Cause_to_make_progress and making Manufacturing bombs immune to predetonation caused Causation by nearby nuclear explosions .