"On This Day" In Engineering History

On this day in engineering history, the U.S. Air Force began operations at its second Texas Tower (TT-2), a massive radar platform that was fixed to the ocean floor to protect the northeastern U.S. against a surprise air attack. Located on the Georges Bank some 100 miles east of Massachusetts, this Texas Tower was one in a series of manned radar stations that were so named because they resembled the oil-drilling platforms of the Gulf of Mexico. The Aerospace Defense Command (ADC), the branch of the Air Force that was responsible for the air defense of the United States, estimated that the Texas Towers would help extend contiguous East Coast radar coverage some 300 to 500 miles seaward. In terms of Soviet military capabilities, this would provide the United States with an extra 30 minutes of warning time in the event of an incoming bomber attack.

During the 1950s, the Lincoln Laboratory of the Massachusetts Institute of Technology (MIT) studied the feasibility of putting radar towers on giant metal platforms along the bottom of the North Atlantic. By the spring of 1955, Bethlehem Steel had finished the first such platform, shaping it like an equilateral triangle with cropped ends. Measuring 210 ft. along all three sides, the 6,500-ton steel platform provided a half-acre of surface area and was welded to 20-ft. high structures with decks for living quarters and storage. The platform also contained a helicopter landing pad and an operations station for two sets of radar antennas. To prevent electronic interference, the FPS-3A search set was elevated high above two FPS-6 height finders. The FPS-6 antennas were also pointed in opposite directions, with one facing toward land and the other facing toward sea. By the end of 1955, Bethlehem Steel had assembled the first two Texas Towers (TT-1 and TT-2).

Erecting a Texas Tower was an arduous task. After the platform was hauled out to sea, temporary supports were dropped to the ocean floor and positioned to provide support. With the platform now in place, the Raymond and De Long Companies sited the tower's three permanent legs. Measuring 160-ft. long, these tubular caissons were buried 50-ft. into the shoal. The leg's middle 50 ft. remained underwater, but the top 60 ft. rose high above the ocean's surface. Each steel leg also contained a 140-ft. long tube that measured 6-ft. in diameter. Jacketed by over 2-ft. of concrete, Texas Tower legs could hold either water or fuel. Typically, one leg was used to store the seawater that was converted to drinking water for the crew of 6 officers and 48 airmen.

Life aboard Texas Tower 2 (TT-2) was difficult. Both the structure and its crew suffered from the near-constant vibration caused by rotating radar antennas and diesel generators. The surrounding ocean and tower footings also transmitted distant sounds along the steel legs, amplifying them throughout the entire structure. Although the first three Texas Towers were relatively stable, Texas Tower 4 (TT-4) failed under the stress of and waves. On January 15, 1961, TT-4 was battered by a fierce storm with 85 mph winds and waves up to 35 ft. high. After one of its three legs snapped in half, both platform and crew sank to the ocean floor. By the end of 1963, the U.S. Air Force decommissioned the remaining three Texas Towers, hiring contractors to blast the legs but salvage the metal platforms.

Resources:

http://www.texastower.com/history_new.htm

http://www.radomes.org/museum/documents/TexasTower.html

http://en.wikipedia.org/wiki/Air_Defense_Command