Bathyscaphe Trieste
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Trieste was a deep-diving research bathyscaphe ("deep boat") with a crew of two people, which reached a record-breaking depth of about 10,900 m, in the deepest part of the oceans, the Challenger Deep, in 1960. The dive has never been repeated, and presently no manned or unmanned craft exists capable of reaching such depth.
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[edit] Design
Designed by the Swiss scientist Auguste Piccard, the Trieste was launched in August 1953 in the Mediterranean near Naples, Italy. It was purchased by the U.S. Navy in 1958 for $250,000.00.
The Trieste basically consisted of a float chamber filled with gasoline for buoyancy, and a separate pressure sphere. This configuration (dubbed a "bathyscaphe" by Piccard), allowed for a free dive, rather than the previous bathysphere designs in which a sphere was lowered to depth and raised from a ship, via cable.
In the Trieste the pressure sphere provided just enough room for two persons. It provided completely independent life support, with a closed-circuit rebreather system similar to that used in modern spacecraft and spacesuits: oxygen was provided from pressure cylinders, and carbon dioxide was scrubbed from breathing air by being passed through canisters of soda-lime. Power was provided by batteries.
The pressure sphere was built by the Krupp Steel Works of Essen, Germany, in three finely-machined sections (an equatorial ring and two caps). To withstand the high pressure of 8 tons per square inch (110 MPa) at the bottom of Challenger Deep, the sphere's walls were 5 inches (127 mm) thick (it was actually overdesigned to withstand considerably more than the rated pressure). The sphere weighed 13 long tons in air, 8 in water. The float was necessary because the sphere was dense: it was not possible to design a sphere large enough to hold a man which would withstand the necessary pressures, yet also have metal walls thin enough for the sphere to be neutrally-buoyant. Gasoline was chosen as the float fluid because it was lighter than water, yet relatively incompressible even at extreme pressure, thus retaining its buoyant properties.
In appearance at the time of Project Nekton, Trieste was over 50 feet (15 m) long, but the great extent of this was a series of floats filled with 22,500 US gallons (85 m³) of gasoline, and air-filled ballast tanks at either end of the vessel. The crew pressure sphere was 6.5 ft (2.16 m), attached to the underside of the floats and acccessed from the deck of the vessel by a vertical tunnel which penetrated the float and ran down to the sphere hatch.
Observation of the sea outside the craft was conducted directly by eye, via a single highly-tapered cone-shaped block of Lucite (Plexiglas) plastic, the only transparent substance identified which would withstand the needed pressure, at the design hull thickness. Outside illumination for the craft was provided by quartz arc-light bulbs, which proved able to withstand the over-1000 atmosphere pressure without any modification.
Nine tons of iron pellet shot were taken on the craft as ballast, both to speed the descent and allow ascent, since the extreme pressures would not have permitted air-ballast tanks to be refilled with gas at depth. This additional weight was held actively in place at the throats of two hopper-like ballast silos by electromagnets, so that in case of an electric failure the craft would spontaneously rise to the surface.
Transported to the Naval Electronics Laboratory's facility in San Diego, the craft was extensively modified and then used in a series of deep-submergence tests in the Pacific Ocean during the next few years, including a dive to the Mariana Trench, the deepest known part of the ocean, in January 1960.
[edit] The Mariana Trench dives
Image:Bathyscaphe Trieste Piccard-Walsh.jpg Trieste departed San Diego on October 5, 1959 on the way to Guam by the freighter Santa Maria to participate in Project Nekton — a series of very deep dives in the Mariana Trench.
On January 23, 1960, Trieste reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying Jacques Piccard (son of Auguste) and Lieutenant Don Walsh, USN. This was the first time a vessel, manned or unmanned, had reached the deepest point in the Earth's oceans. The onboard systems indicated a depth of 37,800 ft (11 521 m), although this was later revised to 35,813 ft (10 916 m), and more accurate measurements made in 1995 have found the Challenger Deep to be slightly shallower, at 35,798 ft (10 911 m).
The descent took almost five hours before reaching the ocean floor. The two men spent barely twenty minutes there. While on the bottom at maximum depth, Piccard and Walsh (unexpectedly) regained the ability to communicate with the surface ship, USS Wandank II ATA-204, using a sonar/hydrophone voice communications system. [1]. At a speed of almost a mile per second, it took about 7 seconds for a voice message to travel from the craft to the surface ship, and another 7 seconds for answers to return.
While on the bottom, Piccard and Walsh observed small soles and flounders swimming away, proving that certain vertebrate life can withstand all existing extremes of pressure in earth's oceans. They noted that the floor of the Challenger Deep consisted of "diatomaceous ooze".
After leaving the bottom, they undertook their assent, which required 3 hours, 15 minutes. Since then, no manned craft has ever returned to the Challenger Deep. A Japanese robotic craft Kaiko reached the bottom of the Challenger Deep in 1995. This craft was lost at sea in 2003, leaving no craft in existence capable of reaching these most extreme ocean depths (which, however, represent an extremely tiny fraction of the ocean's bottom area).
[edit] Other deep dives by Trieste
In April 1963, Trieste was modified and used in the Atlantic Ocean to search for the missing submarine USS Thresher (SSN-593). In August 1963, Trieste found the wreck off New England, 8,400 feet (2.56 km) below the surface. The bathyscaphe was then retired and dismantled, and her pressure sphere was incorporated into the Trieste II, which also conducted some dives to the USS Thresher site in 1964.
[edit] Retirement
The Trieste class bathyscaphes made their last dives in 1983, and were replaced afterwards by the Alvin class submersibles, best exemplified by DSV Alvin itself. Though the newer design could not dive as deep (a maximum of 20,000 feet for DSV Sea Cliff), they were generally more capable and more durable.
The original Trieste pressure sphere (which had been eventually replaced by a newer sphere in Trieste II) is now on permanent exhibit at the U.S. Navy Museum, Washington Navy Yard in Washington, DC.
[edit] External links
[edit] See also
[edit] Reference
SEVEN MILES DOWN: The Story of the Bathyscaph Trieste. Jacques Piccard and Robert S. Dietz. Copyright 1961, Published 1962, Longmans, Green and Company, London. ISBN 0-471-68018-4.de:Trieste (U-Boot) ru:Триест (батискаф) fi:Trieste (batyskooppi)
