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LC-25C First Trident launch January 18th 1977 (picture credit USAF)
Launch complex 25 is a four launch pad site which was built in two stages. Launch Pads 25A and 25B were constructed in the late 1950s with launch pads 25C and 25D being added in 1967.
All four launch pads share the same blockhouse. The cabling channels for each pad can be clearly seen on the Google image.
LC-25 was built for the US Navy to test and develop Sea Launched Ballistic Missiles AKA Submarine Launched Ballistic Missiles or SLBMs.
Initially the pads 25A and 25B launched a combined total of 68 missiles with the majority from pad 25A. All of these were variants of the Polaris launch vehicle. On launch pad 25B there are 2 pits separated by a distance of about 100 feet. One of the pits is obviously a subterranean launch facility, the other seems to house equipment rooms. It is possible that these were designed to simulate a submarine.
Launch Pads 25C and 25D were constructed in 1967. Connecting to the same blockhouse they were built with more infrastructure. Pads 25C and 25D were connected by a rail system enabling the use of a retractable service structure. Indeed this service structure is still in place on pad 25C today. The pads were built to support the Poseidon and Trident programs. 34 missiles were launched from 25C and just one from 25D.
Today the subterranean launch facility is still in existence, the metalwork is rusting and the launch rails have been removed, but a few of the blast doors still flap around in strong winds. On pad 25C the retractable service structure is still in place.
LC-25 Aerial view as of today (Image credit Google)
SLC-25 View from pad 25B to the blockhouse
SLC-25 subterranean missile launch pad.
SLC-25 Blast doors heading to the launch pit
SLC-25B Blast doors to equipment areas
LC-25C Retractable service structure
The undergound launch pit at Pad 25B housed a ship’s motion simulator. Hydraulically-actuated gimbals tilted and rocked the Polaris missiles as a surfaced submarine would move in wind-swept seas. This testing was done to ensure that the missiles’ guidance systems would not be adversely affected by the motions of the launching vessels. The test missiles were launched from the Ship’s motion simulator as it moved back and forth.