Operation Crossroads was a series of two nuclear tests, Able and Baker, the first tests conducted at the Pacific Proving Ground, near the Bikini Atoll in the Marshall Islands. These were the fourth and fifth nuclear detonations in history, following the Trinity test in July 1945 and the two weapons dropped on Japan to end World War II.
ABLE operations went smoothly except that the test weapon was dropped between 1,500 and 2,000 feet (457 and 610 meters) off target. The device detonated above Bikini Lagoon at an altitude of 520 feet, but it was off-target by 1500 to 2000 feet to the west of the planned surface zero, marked by USS Nevada (BB 36). Five ships were sunk, 6 seriously damaged, 17 somewhat damaged, and 43 suffered “negligible damage”.
Shot BAKER was expected to cause more damage to the target fleet than did ABLE because it was an underwater detonation and closer to the surface. It was also expected to produce more radioactive contamination in Bikini Lagoon—although no one knew how much more. As it turned out, contamination from BAKER caused major problems that persisted for months and threatened the overall success of the operation.
BAKER inflicted heavy damage on the target fleet. Eight ships, including the aircraft carrier USS Saratoga, were sunk and eight more were seriously damaged. Even more important for the remainder of the operation, the detonation caused most of the target fleet to be bathed in radioactive water spray containing debris from the nuclear device, mixed with material dredged from the lagoon bottom.
Bikini was used for nuclear tests for many more years and 23 tests in all were conducted around the atoll. This included the first hydrogen bomb (BRAVO Blast) - the largest bomb the US Military has ever tested. BRAVO vaporised an island in the Bikini Atoll group and left a crater in the ocean 60m deep and approximately a mile wide. The yeild was 4 times larger than expected and fallout caused the evacuation of other nearby atolls. The bomb had a yeild for 15 megatons - nearly 1000 times more than the Crossroads tests and within seconds of detonation had a fireball over three miles wide. The illumination from the blast was visible for almost one minute on Rongerik, an island 135 miles east of the burst.
Today the background radiation levels around Bikini are lower than you would expect in most major cities, and considerably less than that experienced while flying in a commercial jet. The shipwrecks from Operation Crossroads offer what is possibly the best wreck diving in the world.
The Expedition
What can you say about Bikini Atoll that has not already been written? The sheltered lagoon simply offers some of the best wreck diving in the world, and a group of UK based divers recently visited Bikini for two weeks to explore these wrecks. The names of the wrecks are written in history - Saratoga, Nagato, Arkansas, Lamson - any one of these wrecks would be a magnet to wreck divers, but such a collection with such a historic sinking is irresistable. It's a long haul from London to Bikini, so the group stopped off in Honolulu en route - partly to break the trip, and partly to visit Pearl Harbor.
As well as the moving Arizona memorial and the restored Missouri, Pearl Harbor also houses the USS Bowfin museum, a restored Balao class submarine which is the sister of the USS Apogon and Pilotfish, both of which are sunk in Bikini Atoll. The team took the opportunity to have a good look around this submarine that the would soon be diving, memorising the features so that they could gain a better understanding of the wrecks.
The team had been planning the trip for two years, and during that time a number had started diving the KISS closed circuit rebreather. The KISS is a non-electronic CCR which uses a constant feed of O2 into the loop to compensate for the normal O2 consumption of the diver, so there are no complex electronics to go wrong. The diver is required to directly manage thier own PO2 by monitoring three independent displays and adding O2 or Diluent as required.
A meeting with Fabio Amaral (ex Bikini dive master) at the London Dive Show in spring 2002 gave the team a chance to discuss the logistics of getting the rebreathers and consumables to Bikini. The KISS is quite a compact rebreather so transportation of the units themselves would not be an issue. However, five closed circuit divers would consume a considerable quantity of sodalime during a two week trip, and this would need to be sourced and shipped to Majuro in time to make the supply boat to Bikini in January 2003. Oxygen is manufactured on Bikini, but the process used concentrates highly narcotic Argon into the output gas resulting in something like 96%O2, 4% Argon. The team therefore decided to try to source some Helium to take the edge off the 52m (170 foot) depth of some of the wrecks. Fortunately someone had previously shipped some Helium to Bikini for open circuit use and there was sufficient left for the rebreathers. A suitable price was agreed and the team was now ready to go.
Shortly before the trip Gordon Smith, the manufacturer of the KISS, released a small gas powered booster pump. The boosters are easily portable, measuring just about a foot long by 4 inches square and weighing only 7 pounds. This made the gas logistics of the trip much better - the initial plan was to split the Helium accross something like 7 large cylinders to form a cascade system to decant gas from. With the boosters we could now mix a much richer Heliar into only 3 cylinders and then pump our diluent cylinders directly from these. We generally re-filled the diluent cylinders every other day, and were able to drain the supply cylinders down to less than 500psi thus maximising our use of the Heliair mix.
The diving itself was exceptional - during the first week there were other divers on the Atoll so we did the standard tour of the wrecks, visiting each of the major wrecks. The dive on the Apogon was revealing - with the Bowfin so fresh in our minds it was simple to reconstruct the wreck in our heads as we swam along the length of the sub - in some ways you can get a better look at the Apogon than the Bowfin, as it's impossible to peer down the periscope tubes, sit under the bow or examine the rear torpedo tubes on the boat in Pearl Harbor. There's also a break in the pressure hull of the Apogon which opens into the forward torpedo room - it's just big enough to squeeze head and shoulders into so you can compare the silty interior to the brighly polished museum pieces. Other memorable dives include the HIJMS Nagato with its enourmous 16 inch guns, the destroyers Lamson and Anderson which are bristling with weaponry, the battleship Arkansas and of course the centrepiece of Bikini, the aircraft carrier USS Saratoga CV-3.
For the second week the team had the atoll to themselves, and we were able to choose our dive sites. Additonally we were able to conduct some more extensive exploration inside the Saratoga. At 900 feet long, 100 feet wide and 80 feet from deck to keel the Saratoga is a 3-D labythinth with all the usual hazards of silt-outs, entanglement and disorientation. For this reason penetration diving is usually off limits, but with the atoll to ourselves and careful planning with the Bikini dive masters we were able to agree each pair's penetration route and ensure that safety was not compromised. The team managed to reach various places inside the ship - living, messing and galley areas, senior officer's cabins, dentists offices, sick bay, blackmsith's workshop and a general workshop full of lathes, drills and other machinery. Rather than being stripped bare before the atomic tests, these spaces were all left intact - there is still some highly decorative tableware in the captain's cabin, cupboards are stacked with crockery and the fearsome looking drill still stands in the dentist's. It's easy to imagine corridor's and spaces bustling with ship board life, but the Saratoga is starting to feel the effects of nearly 60 years underwater. Hanging inside the darkness of the ship the silence of a rebreather enabled us to hear her groan and creak as she slowly loses her fight with the sea.
The KISSes worked almost flawlessly during the trip - in total the team logged nearly 120 rebreather dives totalling over 170 hours. The booster pumps required some routine maintenance but were otherwise trouble free. Although there have been individual rebreather divers on Bikini in the past, the team was the first group of rebreathers to visit and was the first to make significant use of Helium to support the diving.
Overall the trip met or exceeded all expectations of the team - quite something after two years of planning and expectation. This would not have been possible without the assistance and cooperation of the Bikini team, especially Tim Williams (chief Dive Master), Jon Salas (assistant Dive Master), Brenda Waltz and Jack Niedenthal (from the Bikini office).
