The massive cloud that billows underneath rockets during takeoff is not the rockets’ exhaust. Rather, it is millions of liters of mist that is sprayed out from the launchpad. The reason? To prevent the engines from tearing themselves apart. It is all part of NASA’s ingenious sound suppression system.
Space is immensely difficult to reach. Achieving a low Earth orbit requires hundreds of thousands of pounds of thrust from incredibly powerful rockets. The engines need to be incredibly robust to withstand the heat and power that comes out of the nozzles.
Though, it is not the heat that causes the greatest problem. In fact, it is the sheer noise of the engines that threaten to compromise the integrity of the engine. The engines create a lot of propulsion, however, they also generate a ton of sound energy. The engines create vibrations so violent, they threaten to compromise the structural integrity of the rockets.
To prevent the components from disintegrating, NASA has devised an ingenious sound suppression system.
NASA’s Sound Suppression System
NASA’s rocket engines generate over 30-times the total thrust that a 747 jet produces. Their newest engines produce 20 percent more thrust than the Saturn V at liftoff. Unsurprisingly, the rockets generate an incredible amount of noise.
To prevent catastrophic failure during liftoff, NASA turns the launch pad into a raging river. Encircling the launch pad are massive trenches which contain the blast of the rockets.
NASA’s sound suppression system in effect [Image Source: NASA]
To prevent a disastrous explosion, NASA must contain the energy using water. Lining the blast pad are massive pipes which eject copious amounts of water. At the time of liftoff, the flow rate exceeds 900,000 gallons a minute.
To supply the colossal amount of water necessary, NASA has constructed an elevated water tank city of 300,000 gallons (1,135,620 liters). The tank stands at 290 feet (88 meters) and stands adjacent to the launch pad.
Multiple 7-foot-diameter (2.1-meter) pipes carry the torrent of water to the pad.
Although NASA extensively uses the technique, the technology was derived from a rather surprising field – stealth submarines.
Applying Stealth Submarine Technology
The invention of sonar enabled navies around the world to detect submerged submarines. The technology works by sending a signal that bounces off of objects and returning the signal. By measuring how long the return signal takes, the distance of the object can be determined.
However, if a signal does not return, an object cannot be detected.
During both World Wars diesel submarines were extensively used. However, so was sonar. The diesel engines create a lot of vibrations which propagated through the ocean. Microphones and sonar systems easily pick up the disturbances, allowing them to initiate a counter-attack. That is unless the submarines use stealth technologies. One of the most effective ways to capture sound energy underwater is by creating bubbles – and lots of them.
How it Works
Bubbles have the ability to absorb a remarkable amount of sound. As sound waves propagate through the water and encounter an air bubble, it causes the bubble to compress. The compression converts the sound energy into heat, substantially dampening the noise.
Naval engineers use the technique on diesel engines by using some of the exhaust to create bubbles near the engines. The bubbles absorb the sound signature coming from the vessel, as well as capture incoming sonar waves. The sound is almost entirely absorbed, making the submersible completely invisible to sonar.
NASA makes use of the effect by spraying water molecules into the surrounding air at the Mobile Launcher Platform. Similar to the compression of the bubbles, when water molecules encounter a sound wave, they begin to vibrate, converting the sound energy into heat.
16 massive nozzles release thousands of liters of water onto the launch pad. [Image Source: NASA]
The water system protects massive rockets during launch. Seconds before launch, 16 nozzles create a cascade of water which absorbs most of the sound energy. The system is effective enough to reduce the noise by half. It reduces acoustical levels within the orbiter payload bay to about 142 decibels, below the design requirement of 145 decibels.