Take a closer look at a rocket launch site before liftoff, and you will notice several tall structures around the launchpad. One of them is the water tower, which raises the question of what its purpose is at a launch facility.
Water towers are predominantly used during a rocket launch to provide the necessary water volume to the sound suppression system at sufficient pressure. This system protects a launch vehicle from damage by the acoustic energy generated by the rocket thrusters and reflected off the launch platform.
The billowing clouds of white “smoke” observers typically see expanding rapidly from a launchpad as a rocket lifts off are, in fact, clouds of steam forming as the heat from the rocket thrusters vaporizes the thousands of gallons of water sprayed onto the launchpad.
The tall water towers next to launchpads are the source of these large quantities of water. They serve two essential purposes: To supply an adequate supply of water to the sound suppression system & reduce heat damage, and prevent the spread of fire on the pad.
The Use Of Water Towers In Sound Suppression Systems On A Launchpad
The noise produced by a rocket’s thrusters during launch can reach sounds in excess of 200 decibels. (Compared to the 120 decibels of the sound created during amplified rock concerts or the 130 decibels generated by a commercial jet aircraft during takeoff.)
Considering the fact that rocket engines designed to reach Low Earth orbit and beyond produce several hundred thousand to millions of pounds of thrust, it comes as no surprise that they produce some of the loudest artificiality-generated sounds on the planet.
(The Delta IV’s thruster produces approximately 600 000 pounds of thrust, while the combined output of the liquid and solid rocket boosters of the Space Shuttle resulted in approximately 7 million pounds of thrust.)
This deafening noise also travels at extremely high velocities as the hot gases accelerate through a rocket’s nozzle at supersonic speeds. This creates a shockwave (or acoustic energy) that reflects off the launch platform back to the launch vehicle.
It is so powerful that the shockwave can damage both the rocket and launch structure. During the launch of the Space Shuttle Columbia in 1981, 16 thermal tiles were dislodged, and another 148 were damaged due to the reflected acoustic energy.
As a result, multiple nozzles are placed on the launchpad to start spraying large volumes of water at high velocities between the rocket nozzles and launch platform just before and during the launch to significantly reduce the effect of the acoustic energy.
The jets of high-speed waterdrops can absorb and suppress the effect of the shockwave to a large extent. The sound suppression system works so well that it can reduce the noise level from 200 decibels to a more manageable and less damaging 142 decibels.
To transport and spray such a large quantity of water (up to and exceeding 1.4 million liters or 300 000 gallons) in such a short period of time onto the launchpad, a lot of pressure is needed, which is the main reason why water towers at launch facilities are so tall.
The higher these towers are placed off the ground, the more pressure they can produce as a result of the Earth’s gravitational force. It explains why water towers (also known as Horton Spheres) are some of the biggest and tallest structures at any major launch facility.
For example, Blue Origin’s tower at Cape Canaveral Air Force Base stands 107 meters (351 feet) tall, eclipsing the water tower at Wallops Flight Facility in Virginia, previously thought to be the world’s tallest at a height of 93.5 meters (307 feet).
The water tower used at Launch Complex 39A at the Kennedy Space Center during the Space Shuttle Program was 88.3 meters (290 feet) tall and stored 1.4 million liters (300 000 gallons) in its spherical tank.
The water from this tower was pumped through a network of pipes to the launchpad, where 16 nozzles (known as rainbirds) situated on top of the platform would spray it between the thrusters and the platform. It was capable of emptying the entire water tank in only 41 seconds.
(The height of the water tower generated enough pressure to allow the nozzles on the platform to spray the water at a rate of 4 million liters (900 000 gallons) per minute underneath the Shuttle’s main and solid rocket boosters.)
The Use Of Water Towers To Reduce Heat And Prevent Fires On Launchpads
It may not be the primary purpose of water towers situated at rocket launch facilities, but reducing heat buildup and preventing a fire on launchpads are considerations that further emphasize the necessity of these structures near launchpads.
Although some first-stage rocket boosters are expendable while others are reused, almost all launch platforms will be reused multiple times, and it only makes sense to protect and preserve as much of the launch structure as possible.
NASA and other space agencies are keenly aware of this fact and use the thousands of gallons of water pumped to the launchpad for this very purpose.
Rocket engines easily generate temperatures of 2 200 – 2 800° Celsius (4000–5000° Fahrenheit) on a launch platform during liftoff. Almost all artificially created materials, even asbestos, melt at these temperatures, so it can severely damage a launch platform.
Apart from structures like flame trenches used to deflect exhaust flames down and away from the launchpad, launch facilities rely on the large volume of water sprayed onto the launchpad to reduce heat buildup & protect as much of the pad as possible.
Reducing the risk of fire is another priority during a rocket launch. Hundreds of thousands of gallons of highly flammable liquid fuel and oxygen are stored on opposite sides of a launchpad and only pumped to the launch vehicle minutes before liftoff.
(Learn more about the different types of fuel rockets used in this article.)
Any leakage or malfunction can result in a fire or explosion that can destroy the spacecraft and payload and severely damage the launchpad. The water that is being sprayed onto a launch platform assists in reducing the risk of such an event.
(Another system that forms a crucial part in protecting an orbital rocket and launch structure alongside the sound suppression system is the flame trench-deflector system. Learn more about this system and the role a flame trench plays in it in this article.)
Conclusion
As illustrated in this article, it is clear that water towers play a crucial role at any rocket launch facility. It provides the thousands of gallons of water that drive the sound suppression system, which protects the vehicle from acoustic energy during liftoff.
Not only does it help to protect the vehicle and tower structure from the shockwave, but it also reduces heat buildup on the launch platform and helps to reduce the risk of a fire starting and spreading during liftoff.
This article was originally published on headedforspace.com. If it is now published on any other site, it was done without permission from the copyright owner.
