When HMNZ Ships PUKAKI and ROTOITI, two of our Loch-class frigates, departed Auckland for Christmas Island at 0900 Thursday, 14 March, 1957 they became an essential part of Operation Grapple, Britain’s hydrogen bomb tests in the Pacific. Britain’s determination to retain its status as a great power in a Cold War context, demanded the development of nuclear weapons to deter the USSR and to have parity with the USA. After successfully developing an A bomb, the British resolved to build a Hydrogen bomb as the primary weapon of their deterrent jet V-bombers. Their search for an isolated test site led to the Pacific and Captain James Cook’s Christmas Island. Britain asked the New Zealand government to provide two RNZN frigates as weather ships to provide meteorological reporting for the British testing programme.
All of the four deployments by our two frigates during Operation Grapple were similar. Departing Devonport, Auckland they all had stops in transit at Fiji, Western Samoa or the Cook Islands, and often they dropped off stores or mail at Raoul Island.
As they closed on the equator and crossed it towards Christmas Island the lack of air-conditioning on the frigates made the increasing heat and humidity an escalating problem for all in the ships. The tedium of shipboard life at sea was relieved in the manner that only sailors know, with the combined effect of maintaining both morale and efficiency.
But in addition the internal preparations, drills and exercises relating to shutting down the ship when passing through a zone of radioactive fall-out were practised regularly. Action stations and damage control states were exercised frequently, usually followed by “shelter stations” which simulated the ship being covered in nuclear radiation. With the exception of the essential crew needed to maintain the ship’s cruising state, everyone went below the water-line – to avoid horizontal radiation – while the external air supply was closed down, re-circulating the air between decks in the ‘citadel’ and squeezing everyone into the confined areas of the lowest mess decks, storerooms and even in magazines.
The crew regularly exercised the routine to be followed when inside the Test Area with a nuclear explosion imminent. The upper deck hoses were used to pre-wet the decks as the ship went to the highest damage control state. The ship’s company was mustered on the upper deck with only the engine and boiler rooms running.
Everyone was dressed in their AWDs with their anti-flash balaclavas and gloves. Trousers were tucked into socks, cuffs of sleeves into gloves and sun-glasses donned to protect any exposed skin and eyes from flash. When the warning order came from the bridge they all sat down with backs to the rail or a bulkhead with their backs to the site of the explosion. They placed their hands over their eyes as the countdown began. At the conclusion of the weapon test the ship was covered in a shower of spray to wash away any radiation before monitoring teams in AWDs, face masks and breathing gear searched for radiation hot-spots. The drills became very serious business as the ships entered the Grapple Restricted Area around Christmas Island.
On arrival at Christmas Island the frigates joined the Royal Navy flotilla in the anchorage at London Roads. The ship went on to tropical routine and all faced the monotony of watch-keeping with the problem of filling in the spare hours at anchor. Officers and sailors hosted social occasions in their respective messes which established an easy rapport with the ships of the Royal Navy. The Task Force Commander regularly addressed each ship’s company prior to each Bomb Test while Royal Navy staff officers were frequent visitors to the frigates. Afternoon shore leave was granted for swimming parties, and canteen leave ashore granted to give sailors a break from the ship. The only place to visit was the wet canteen in Port London, a steel Nissan hut with steel tables and chairs and English beer served in tins, but it became a popular meeting place for sailors, soldiers and airmen from the UK and New Zealand.
The coral on Christmas Island was a major handicap for sporting contests as it caused nasty wounds which were slow to heal. On-board entertainment was primarily British films –the Grapple task force was well supplied with movies from the UK. But a considerable amount of time was spent perfecting the prime function of the RNZN frigates for the operation – weather reconnaissance and reporting.
The weather ships were supplemented by RAF Canberra bombers, which made high and low level flights to produce additional weather observations. Ideal Test requirements demanded weather conditions that ensured the mushroom cloud would disperse over the nearly 5,000 miles of empty sea, away from any Pacific Islands or Japan. So the ship’s task was essentially wind-tracking, which was carried out by launching hydrogen-filled meteorological balloons to a height of 60,000 feet which were tracked by the frigate’s height-finding Type 277 radar.
Weather balloon runs were carried out prior to each Bomb Test, when a balloon was launched every six hours from the balloon hut built aft on the upper deck of the frigates. The balloon ascended 6,000 feet (1.8km) every six minutes at which point it recorded wind direction and speed, air temperatures and barometric pressure which were transmitted to the Weather Centre on Christmas Island. Tracking terminated after an hour or so, when the balloon exploded at about 70,000 feet (21 km). It was an important function and demanded considerable expertise of the radar plotters responsible. At least one balloon was tracked to 119,000 feet!
The actual nuclear bomb tests occasioned considerable tension and excitement throughout the ships. As the vapour trail of the Vickers Valiant carrying the bomb loomed over the horizon the ship went into countdown to the explosion. The aircraft reported the bomb release. The flash was intense and many sailors recall that for a moment the bones of their fingers were visible through closed eyes. Then came the heat, like a warm breeze on everyone’s back. With the explosion, a ‘count up’ began, until the command came from the bridge to stand up and turn around. Typically there was an awed silence among the ship’s company, as they watched the gigantic fireball glowing intensely and growing larger as it rose into the sky – then the double crack of the explosion which came racing across the water with a dull thud. As the cloud rose it transformed into the characteristic white mushroom cloud, expanding until the upper atmospheric winds flattened off the top.
The Royal New Zealand Navy’s contribution to Operation Grapple came to an end when PUKAKI sailed into Devonport on Thursday, 9 October 1958. While the sailors willingly did their duty, we know now that few of the New Zealand sailors who were at the bomb tests have emerged unscathed from their experience.
|Grapple 1||15 May 57||Air dropped bomb||300KT*||PUKAKI & ROTOITI|
|Grapple 2||31 May 57||Air dropped bomb||700KT**||PUKAKI & ROTOITI|
|Grapple 3||19 Jun 57||Air dropped bomb||200KT||PUKAKI & ROTOITI|
|Grapple X-ray||08 Nov 57||Air dropped bomb||1.8MT***||PUKAKI & ROTOITI|
|Grapple Yankee||28 Apr 58||Air dropped bomb||3.0MT||PUKAKI|
|Grapple Zulu 1||22 Aug 58||Suspended from balloon||24KT||PUKAKI|
|Grapple Zulu 2||02 Sep 58||Air dropped bomb||1.2MT||PUKAKI|
|Grapple Zulu 3||11 Sep 58||Air dropped bomb||800KT||PUKAKI|
|Grapple Zulu 4||23 Sep 58||Suspended from balloon||25KT||PUKAKI|
|Notes:KT = kilotons; thousands of tons of TNT equivalent
MT = megatons; millions of tons of TNT equivalent
* Grapple 1 was a failure, no fusion reaction occurred, only a fission explosion.
** Grapple 2 was a fission weapon (A-bomb) Britain’s largest ever.
*** Grapple X-ray was Britain’s first successful H-bomb.
Subsequent tests proved variations of weapon design