Function: Military Sealift Command's Special Missions program supports worldwide oceanographic programs with ships which perform acoustical, biological, physical and geophysical surveys. Ships such as USNS Silas Bent (TAGS 26), USNS Kane (TAGS 27) and USNS Bowditch (TAGS 62) gather data which provides much of the military's information on the ocean environment. Oceanographic and hydrographic survey ships are used to study the world's oceans. The collected data helps to improve technology in undersea warfare and enemy ship detection. The oceanographic and hydrographic survey ships' multibeam, wide-angle precision sonar systems make it possible to continuously chart a broad strip of ocean floor. Two oceanographic ships survey the sea bottom and collect hydrographic data, charting three-fourths of the world's coastlines. USNS John McDonnell (TAGS 51) and USNS Littlehales (TAGS 52) make it easier for navigators to find their way along well-traveled and not-so-familiar shipping routes.





History: The USNS John McDonnell (TAGS 51) was laid down Aug. 3, 1989, and the USNS Littlehales (TAGS 52) on Oct. 25, 1989. The McDonnell launched Aug. 15, 1980, the Littlehales on Feb. 14, 1991. The contract for the Pathfinder class of surveying ships was awarded in January 1991 for two ships with an option for a third which was taken up May 29, 1992. A fourth ship was ordered in Oct. 1994 with an option for two more. A fifth ship was ordered Jan. 15, 1997.





Description: The Silas Bent class of surveying ships were designed specifically for surveying operations. They have a bow propulsion unit for precise maneuverability and station keeping. The John McDonnell class of survey ships carries 34-foot survey launches for data collection in coastal regions with depths between 10 and 600 m and in deep water to 4,000 m. A small diesel is used for propulsion at towing speeds of up to 6 knots. SIMRAD high-frequency active hull-mounted and side scan sonars are carried. The Pathfinder class of survey ships have three multipurpose cranes and five winches plus a variety of oceanographic equipment including multibeam echo-sounders, towed sonars and expendable sensors.





General Characteristics, Silas Bent Class



Builders:

American SB Co., Lorain/Christy Corp, Sturgeon Bay, WI





Power Plant:

Diesel-electric; two Alco diesel generators; one Westinghouse/GE motor; 3,600 horsepower (2.69 MW); one shaft; cp prop; bow thruster; 350 horsepower (261 kW)





Length, Overall:

285.3 feet (86.96 meters)







Beam:

48 feet (14.63 meters)





Displacement:

2,550 to 2,843 long tons (2,590.92 to 2,888.62 metric tons) full load





Speed:

15 knots when towing





Crew:

31 civilians (12 officers) plus 28 scientists











Ships:

USNS Silas Bent (T-AGS 26)

USNS Kane (T-AGS 27)







General Characteristics, John McDonnell Class



Builders:

Halter Marine Moss Point, MS





Power Plant:

One GM EMD 12-645E6 diesel; 2,500 horsepower (1.9 MW) sustained; one auxiliary diesel; 230 horsepower (172kW); one shaft





Length, Overall:

208 feet (63.40 meters)







Beam:

45 feet (13.72 meters)





Displacement:

2,054 long tons (2,086.96 metric tons) full load





Speed:

12 knots (13.8 mph, 22.22 kph)





Crew:

22 civilians plus 11 scientists











Ships:

USNS John McDonnell (T-AGS 51)

USNS Littlehales (T-AGS 52)







General Characteristics, Pathfinder Class



Builders:

Halter Marine Moss Point, MS





Power Plant:

Diesel-electric; four EMD/Baylor diesel generators; 11, 425 horsepower (8.52 MW); two GE CDF 1944 motors; 8,000 horsepower (5.96 MW) sustained; 6,000 horsepower (4.48 MW); two Lips Z drives; bow thruster, 1,500 horsepower (1.19 MW)





Length, Overall:

328.5 feet (100.13 meters)







Beam:

58 feet (17.68 meters)





Displacement:

4,762 long tons (4,838.42 metric tons) full load





Speed:

16 knots (18.4 mph, 29.63 kph)





Crew:

28 civilians plus 27 scientists











Ships:

USNS Pathfinder (T-AGS 60)

USNS Sumner (T-AGS 61)

USNS Bowditch (T-AGS 62)

USNS Henson (T-AGS 63)

USNS Bruce C. Heezen (T-AGS 64)