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Written and Edited by Cliff Lethbridge




Configuration: Single Blockhouse, Three Flat Launch Pads, One Ship Motion Simulator




Current Status: Inactive


First Launch: April 18, 1958


Final Launch: March 5, 1965


Number of Launches: 60


Vehicles Launched: Polaris FTV, Polaris A1, Polaris A2, Polaris A3




Current Status: Inactive


First Launch: August 14, 1959


Final Launch: August 2, 1960


Number of Launches: 8


Vehicles Launched: Polaris A1




Current Status: Inactive


First Launch: August 16, 1968


Final Launch: January 23, 1979


Number of Launches: 34


Vehicles Launched: Poseidon, Trident I




Current Status: Inactive


First Launch: September 17, 1969


Final Launch: September 17, 1969


Number of Launches: 1


Vehicles Launched: Poseidon


Launch Complex 25 was built in support of Polaris missile testing. It originally consisted of a blockhouse and two launch pads, flat pad 25A and ship-motion simulator 25B, of which Launch Pad 25B is described below. The site was later modified in support of the Trident I missile testing program. Two launch pads were constructed more distant of the blockhouse, and the blockhouse was reinforced on its front, facing newly constructed Launch Pads 25C and 25D. The blockhouse was converted for office space, and all four launch pads still exist. The site has been slated for refurbishment for future Navy use, although the specific dates and new vehicle types have not been announced.


One of the most interesting and unique features of Launch Complex 25 was Launch Pad 25B, not in fact a traditional launch pad but an ingenious and sophisticated Ship Motion Simulator (SMS).


Nicknamed the "Shaker", the SMS was designed to simulate the effects of ship motion on a missile before, during and after launch. When the SMS was built and tested in late, 1958 the Navy still considered deploying solid-fueled missiles on ships.


Because a ship is more subject to motion than a submerged submarine, engineers needed to be certain that missiles could be safely handled and launched at sea. To do this, the $3 million SMS was installed at Launch Complex 25.


The SMS could simulate roll, pitch and heave. These are just three of the six motions a ship is subject to at sea, but the only three motions considered to have an effect on the handling and launching of a missile.


Designed, built and installed by Loewy-Hydropress Division of Baldwin-Lima-Hamilton Corporation, the 400,000-pound SMS was housed in a 55-foot deep pit measuring 33 feet long by 33 feet wide. A total of 23,000 cubic yards of sand needed to be removed during construction.


A seven-foot tall concrete plug was poured at the bottom of the pit. On top of it was placed a square, 47-foot tall box having concrete walls four-feet thick on all four sides. A total of 3,800 cubic yards of concrete was required to complete the structure.


Because the average underground water level at the site is just eight feet, an elaborate series of pumps needed to be installed. Adjacent underground equipment rooms and access passageways were also constructed.


The SMS itself consisted of two gimbal-mounted circular rings attached to a series of guides located on the inside walls of the pit. These guides were able to provide a simulation of the vertical heave, or "up and down" motion of a ship. Roll and pitch motion were simulated through the use of four cylinders arranged in opposing pairs.


The entire SMS assembly was supported by four hydraulic cylinders. Power was provided by two underground electrical generators, one producing 2,250 horsepower and one producing 700 horsepower. Control of the mechanisms that produced the ship motion was provided by hydraulic pumps operating at 2,000 gallons-per-minute capacity and 3,000 pounds-per-square-inch pressure.


The missile itself was positioned atop the SMS, at more or less ground level. Engineers used three-channel magnetic data tape to record roll, pitch and heave motion at sea, and this relative data was programmed into the SMS. The SMS could simulate roll and pitch to a maximum of plus or minus eight degrees, and heave to a maximum of plus or minus seven feet.


Although it was a technical marvel, the SMS was reported to have produced disappointing scientific results. It could only cycle movements in six to 14-second intervals, and so could not accurately simulate the fluid motion of a ship. The SMS did, however, demonstrate that ship motion did not adversely affect the handling or performance of a missile.


While the actual SMS hardware has long since been dismantled and removed, the SMS pit and its associated underground equipment rooms remain at Launch Complex 25. Now completely flooded with water, the SMS pit is well known to be a frequent haunt of Florida alligators.






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