Answer: Sound Dampening

If you’ve ever watched a shuttle launch, you’ve inevitably seen the giant billowing clouds of steam that roll off the launch pad. The steam is generated as a result of water, pumped in massive quantities from a nearby water tower, that douses the Mobile Launcher Platform (MLP) and flame trench under the shuttle during launch—in the image seen here, NASA engineers oversee a test of the water system that douses the Mobile Launcher Platform with over 300,000 gallons of water in less than a minute.

At first glance, it would be easy to assume that the water is used for cooling, but the launch pad and the flame trench underneath it are designed to easily withstand the intense heat and exhaust from the rocket boosters. Instead, the water jets and the resulting billowing clouds of steam are used to dampen the roaring sound of the enormous boosters.

The purpose of the sound suppression isn’t to protect the astronauts or the launch observers from the sound, however, as they are sufficiently protected by their equipment and distance from the launch site, respectively. Instead, it’s to protect the shuttle’s payload. The water system reduces the total energy of the sound low enough that it can’t harm delicate electronics and other equipment in the payload bay of the shuttle.