Project Nekton

Project Nekton was the codename for a series of very shallow test dives (three of them in Apra Harbor) and also deep-submergence operations in the Pacific Ocean near Guam that ended with the United States Navy-owned research bathyscaphe Trieste entering the Challenger Deep, the deepest surveyed point in the world's oceans.

The series of eight dives began with two harbor dives, then a Pacific Ocean test dive at Guam, by the newly modified Trieste, which had been modified to dive far deeper than before. After two checkout dives, the first abyssal dive reached a record of 5,530 m (18,150 ft) on 15 November 1959. The series included a record deep dive to near the bottom of the Nero Deep in the Mariana Trench at 7,300 m (24,000 ft), and finally culminated with a trip to the bottom of the Challenger Deep at 10,911 m (35,797 ft), on 23 January 1960.

The project name was proposed by oceanographer Dr. Robert S. Dietz in early 1958, as plans to modify the Trieste bathyscaphe to go to the deepest part of the oceans were being contemplated. It is in reference to ocean life that actively swims (nekton) as opposed to the plankton organisms that only drift. The bathyscaphe Trieste to be used for Project Nekton was able to move independently, in contrast to tethered bathyspheres. The Trieste featured two electric motors, each with a propeller, of 1.5 kilowatts (2 hp) each. These allowed it to move forward, backward and to turn horizontally. A maximum speed of one knot (0.5 m/s) was attainable over a few miles distance.

Aside from the prestige of being the first to make the deepest dive, the Navy Electronics Laboratory held the following objectives for Project Nekton in furtherance of its underwater sound research for SOSUS and sonar development:

Trieste departed San Diego on 5 October 1959 for Guam aboard the freighter SS Santa Mariana to participate in Project Nekton, a series of very deep dives near Guam, culminating in a descent to the Mariana Trench. It had been modified with a larger gasoline float, larger ballast tubs, and a newly designed heavy pressure sphere (made by Krupp in Germany), after having been purchased by the Office of Naval Research, which undertook the modification.

Guam was selected for the test dives because it was a major naval base with complete facilities only 200 mi (320 km) from the Challenger Deep. The tug USS Wandank (ATA-204) towed Trieste between Guam and the dive sites where project flagship USS Lewis (DE-535) tracked the submerged Trieste with sonar. The first two test dives in the Nekton series were conducted at Guam in the Apra Harbor, then a third dive off the Western flank of Guam reached 4,900 feet (1,500 m). This dive was intended to have the same duration as the deep dive for an endurance test to reveal material failures or hazards not encountered during shorter dives. Trieste could surface in 20 minutes from this depth if problems arose, but no problems were encountered.

The fourth dive in the Nekton series was a very deep dive into the Nero Deep of the Marianas Trench. This deep had been discovered in 1899 by the USS Nero (AC-17) in a search for a deep sea cable route to the orient. It was dive 61 in a long series of bathyscaphe dives supervised by Jacques Piccard. Trieste reached 18,600 feet (5,700 m), later recalibrated to 18,150 feet (5,530 m) depth, to the sea floor, on 15 November 1959. This dive set a new world record depth formerly held by the French Navy for the 13,440 ft (4,100 m) descent on their bathyscaphe FNRS-3 off Dakar, Senegal in 1954.

Northeasterly trade winds caused high seas slowing the tow to the dive site, and raising concern about damage to Trieste's topside equipment as she nosed into the waves. Seas moderated on the day of the dive, and pre-dive inspection found no damage. The surface vessels lost underwater telephone contact with Trieste as the bathyscaphe descended below 6,000 ft (1,800 m) and communication below that depth was limited to a few manually keyed signal codes from the bathyscaphe transducer. A small boat remained over the dive site while the tug and destroyer stood off 2 mi (3.2 km) to avoid damaging Trieste if the bathyscaphe surfaced beneath them. Just before the bathyscaphe surfaced, its crew was startled by a loud "bang" as the expanding bathyscaphe segments broke their epoxy joint seals at a depth of 30 ft (9.1 m). Inspection after returning to Guam revealed some water leakage along the seals between the three sections of the sphere. Trieste was taken out of the water to replace the epoxy glue seals and augment them with mechanical holding ring bands. Some new instrumentation was also installed during this repair period.