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From vantage points on the Fixed Service Structure (left) on Launch Pad 39A, workers and the media look down upon the Mobile Launcher Platform (MLP) waiting for the start of a water sound suppression test. This test is being conducted following the replacement of the six main system valves, which had been in place since the beginning of the Shuttle Program and had reached the end of their service life. Also, the hydraulic portion of the valve actuators has been redesigned and simplified to reduce maintenance costs. The sound suppression water system is installed on the launch pads to protect the orbiter and its payloads from damage by acoustical energy reflected from the MLP during launch. The system includes an elevated water tank with a capacity of 300,000 gallons. The tank is 290 feet high and stands on the northeast side of the Pad. The water is released just before the ignition of the orbiter's three main engines and twin solid rocket boosters, and flows through parallel 7-foot-diameter pipes to the Pad area.