A Sound Suppression Water System has been installed
on the pads to protect the orbiter and its payloads from damage by acoustical
energy and rocket exhaust reflected from the flame trench and Mobile Launcher
Platform during launch. The Shuttle orbiter, with its payloads in the cargo
hold, is much closer to the surface of the Mobile Launcher Platform than the
Apollo spacecraft was at the top of a Saturn V or Saturn 1B vehicle.
The Sound Suppression System includes an elevated
water tank with a capacity of 300,000 gallons (1,135,620 liters). The tank is
290 feet (88 meters) high and is located adjacent to each pad. The water
releases just prior to the ignition of the Shuttle engines, and flows through
7-foot-diameter (2.1-meter) pipes for about 20 seconds. Water pours from 16
nozzles atop the flame deflectors and from outlets in the main engines exhaust
hole in the Mobile Launcher Platform, starting at T minus 6.6 seconds. By the
time the solid rocket boosters ignite, a torrent of water will be flowing onto
the Mobile Launcher Platform from six large quench nozzles, or "rainbirds,"
mounted on its surface.
The rainbirds are 12 feet
(3.7 meters) high. The two in the center are 42 inches (107 centimeters) in
diameter; the other four have a 30-inch (76-centimeter) diameter.
The peak rate of flow from all sources is 900,000
gallons (3,406,860 liters) of water per minute at 9 seconds after liftoff.
Acoustical levels reach their peak when the Space
Shuttle is about 300 feet (91 meters) above the Platform, and cease to be a
problem at an altitude of about 1,000 feet (305 meters).