Oceanographers have traditionally gone to sea to collect the data for their studies of the world oceans in just about any ship that would float. Some still set out in rusty bottoms, but many more are now enjoying the relative luxury of modern ships which have been built and outfitted exclusively for oceanographic research and surveying. Private and federal organizations are responding to the crucial need for oceanic information through increased outlays for the kinds of ships needed to do the job.
The U. S. Navy’s latest contribution to the modern oceanographic fleet has been the delivery of the USNS Silas Bent (T-AGS-26), a pristine oceanographic survey ship which has thus far elicited nothing but praise from the scientists and crew men who have been on board for her few short runs to date.
The first of a new class, the 285¼-foot Silas Bent is under the technical control of the Naval Oceanographic Office, which also has the technical control of 16 other ships performing either oceanographic or hydro- graphic tasks in support of the Fleet.
Four other recent-vintage ships in the Navy’s oceanographic fleet are oceanographic research ships—AGOR—which are designed for research work in contrast to the oceanographic survey functions of the Silas Bent. These AGORs are smaller ships, 209 feet overall, carry more modest instrumentation, and are used by scientists at Navy laboratories, who schedule specific research projects in them.
The Navy’s Military Sea Transportation Service has operational control of the Silas Bent and all the Navy AGOR-type ships. Civil Service mariner employees of MSTS operate these ships, with this civilian manning concept freeing military personnel for other assignments.
Although there is no other ship like the 285j-foot Silas Bent, her basic function is comparable to that of the USS San Pablo (AGS-30) and USS Rehoboth (AGS-50), both of which were converted after World War II from small seaplane tenders to oceanographic survey ships. Being conversions, neither of these ships has the capabilities of the Silas Bent, although both have been returning valuable survey data.
Features setting the Silas Bent apart from her predecessors are her all-weather, ultraquiet operational capabilities, and an electronic instrumentation known as the Shipboard Survey System. A three-million-dollar electronic complex fully representative of the space era, this system was built by Texas Instruments under contract from the Naval Oceanographic Office. It is now undergoing exhaustive test and evaluation at sea before final acceptance. Data gathered by the Shipboard Survey System is being compared to that obtained from measurements with classical oceanographic instruments and to the results of earlier surveys known to have yielded accurate data.
When planning began for new classes of surveying ships in the late 1950s, pioneering concepts in instrumentation were explored in an effort to develop automated data measuring and recording systems. The result, as reflected in the Silas Bent, is an integrated system of electronic instruments capable of measuring ten different ocean parameters and of providing a data output in digital magnetic tape form. The Shipboard Survey System employs a UYK-1 computer and records and displays data immediately in strip-chart and alpha-numeric form.
Thus, survey data which once required weeks and sometimes months to process will be returned by the Silas Bent in immediately usable computer form.
The “control center” for the Shipboard Survey System is on the main deck, just forward of midships. Data from all subsystems are fed to the maze of electronic equipment situated there. An operator at the central control console, which has a monitor panel and a typewriter to plot the co-ordinates of on-station data (as a function of depth), can prepare an operational events log while measurements are made underway.
With this system, five different parameters can be measured underway, and five additional measurements can be taken on-station or when the ship is hove-to. A specially designed sensor package or “fish” is used for measurements on-station. It is lowered and retrieved through a U-frame on the ship’s spacious fantail, using a 25,000-foot armored electrical cable.
The “fish” is a cage of stainless steel ribs, housing pressure-cased sensors which measure subsurface water temperature, sound velocity, salinity, ambient light, and pressure as a function of depth. The maximum operational depth of the “fish” is almost 20,000 feet.
Sensor outputs are FM signals, which are combined in the “fish” signal mixer and transmitted as a composite FM signal via the armored electrical cable to the main shipboard electronics system. Digitalization of the FM signals for display and magnetic tape recording is accomplished by the input-out- put processor of the Central Data Recording System.
Five subsystems for the underway mode measure bathymetric depth, magnetic field intensity, gravity field intensity, sea surface temperature, and sub-bottom characteristics or seismic profiles. All underway measurements can be made up to 15 knots, the ship’s flank speed.
The bathymetric subsystem consists of a conventional wide-beam echo sounder, a stabilized narrow-beam echo sounder, graphic recorders, and two digital bottom trackers.
For magnetic measurements, a proton precision magnetometer, towed from the stern with a 700-foot cable, provides a readout directly in gammas, visually on a Nixie display, graphically on an analog recorder, and digitally on magnetic tape.
Gravity is measured with a LaCoste-Romberg sensor mounted on a gyro-stabilized platform located near the point of least motion of the ship. The seismic subsystem is an all-electronic, sub-profiler designed for sediment penetrations of up to 4,000 feet in water depths as great as 3,000 fathoms. The sea surface temperature sensor is also cased in a “fish” and towed alongside the ship.
Numerous features not found in other Navy surveying ships have been incorporated in the Silas Bent including:
• Good accommodations for 34 scientists.
• Anti-roll tanks for smoother operations in rough seas.
• A retractable bow propulsion and steering unit for position keeping while on an oceanographic station.
• Strengthened hull to permit operations in floating ice.
• A gas turbine to power the main motor or the ship’s bow thruster during ultra-quiet ship operations.
• Fifteen winch systems and a large hydraulic crane for handling a wide range of oceanographic equipment.
Other facilities in the ship include a drafting room, a photography laboratory, scientific chill and storeroom, electronic workshop, meteorological room, scientific gear storeroom, and explosives and meteorological rocket magazines. There also are spacious laboratories for electronic, chemical, biological, and geological research.
To further aid the scientist in his work, Nansen bottles—a backup to the data- gathering “fish”—are stowed in the wet laboratory rather than in exposed deck racks, and a system of overhead rails provides easy movement of bulky equipment from laboratories to weather decks.
These features are built into a ship 285j feet overfall with a full-load displacement of 2,640 tons. To drive her at a maximum speed of 15 knots the Silas Bent has a 3,000- horsepower diesel electric power plant turning a single screw. Her endurance is on the order of 12,000 miles.
She was built on the Great Lakes by the American Shipbuilding Company of Lorain, Ohio. Laid down on 2 March 1964, she was launched the following May, and delivered to the Navy in July 1965. After completing her shakedown the Silas Bent will make surveys in the Atlantic Ocean.
A sister ship, the Elisha Kent Kane (T-AGS- 27), is now under construction and scheduled to be completed in mid-1966. She will be identical to the Silas Bent, with her cost somewhat less than the “just under” ten million dollar price tag of her predecessor. This ship will probably operate in the Pacific.