Why do we "spray" lots of water during a rocket launch?

Written By KYNNMASTER 123

Water, a compound composed of one hydrogen atom and two oxygen atoms, hence its chemical formula H2O. It is truly one of the most precious resources that we use in our everyday lives. From the early days when living things existed, water was used. Fast forward to this day, we have rockets, such pieces of engineering that we use today to explore what is above and beyond the cosmos. Just watching a rocket launch is truly spectacular. Little did we know, water is also being in every rocket launch. Just below the rocket, we can observe huge amounts of water being dumped before the launch starts. So, why do we "spray" lots of water during a rocket launch? What does it serve to the sensitive and expensive pieces of technology we have?

The Sound and Fire Suppression System

The sound and fire suppression system (also called the water deluge system) is the system that works hard on the bottom of the rocket during each rocket launch. It is an important system that is needed for each rocket launch to succeed (judging if there is no proper flame trench and the rocket is too powerful for the concrete below it). This system protects the sensitive equipment that is hit by the immense power that rocket engines produce. To understand more of the reasons why deluge systems are needed during a rocket launch, let's talk about these reasons one by one. Spoiler alert, these reasons are basically in the name of the system itself, which is both for sound and fire suppression.

 

1. Sound Suppression

The primary reason for dumping large amounts of water during a rocket launch is to suppress sound and vibration. Rocket engines produce immense sound and vibration that has the power to destroy the launch infrastructure around it and also the rocket itself. It works in a way that water is like a buffer to the sound waves, which dampens the sound and reduces the risk of damage.

According to NASA, the launch of the Space Shuttle produced around 195 decibels without a proper sound suppression system, which was powerful enough to damage some of the protective tiles on the Shuttle's hull because of its unique design. However, after adding the water deluge system with water bags below the shuttle, they found a way to lower the sound energy to 142 decibels, a better amount of sound energy, equivalent to a fighter jet taking off.

 

2. Fire Suppression

Another reason why dumping large amounts of water during a rocket launch is important is for fire suppression. Aside from the sound that rocket engines produce, they also produce extreme heat due to rocket fuel combustion. The water deluge system helps to cool down these surfaces, which prevents overheating and potential damage to the launchpad.




As the hot rocket plume interacts with water, it creates a layer of steam, which helps to dissipate heat more effectively, which protects the launchpad below the rocket. That steam is actually what causes the massive cloud that is produced by rockets during liftoff, NOT the rocket exhaust.

A scenario where a deluge system was needed (Before)

Look at this photo of the first SpaceX Starship launch, this photo shows how damaging it was while launching the rocket for the first time because of the lack of a water deluge system. The dust on the ground was kicked everywhere due to the immense power of the engines. It was also assumed that dust went to the engines, which made some of them get damaged and shut down. The vibrations and the high temperatures of the rocket and its engine plume also contributed to structures getting destroyed on the launchpad. Some notable vehicles and properties such as the NASASpaceflight van, the cameras that watched the launch up close, and the vertical tank farm were also slightly damaged or worse, destroyed. The immense power of the Starship rocket was surely underestimated in this launch, which needed the addition of a water deluge system below the rocket, which works both as a deluge system and a flame diverter (but water diverting the flame, not a structure).

 

A scenario where a deluge system was needed (After)

Left: Starship Integrated Flight Test 2 (SpaceX) Right: Water-cooled steel plate testing (SpaceX)


After this launch, SpaceX decided to add a water-cooled steel plate below the rocket, which works as a deluge system and a flame diverter (but water diverts the flame outwards, not a structure). After loads of testing, this system proved to be very useful as the second, third, and fourth Starship launches were less damaging to the launchpad than before because of the new system in place. As you compare the photo of the First Starship IFT vs Second Starship IFT, you can see how cleaner the rocket plume is, which means, less dust is now kicked everywhere. The deluge also works well because of the white-colored plume, which is steam properly interacting with the rocket plume as expected, lowering the vibrations and temperatures of the rocket while it is on the ground.

Conclusion

Using a water deluge system during a rocket launch is a useful measure to protect the launchpad and the rocket itself. This simple solution helped us to improve our launchpads for safer and more effective launch operations. By learning how to safeguard our launch infrastructures, we save more time and money on major launchpad refurbishments. It is also important to research more into efficient water usage while using these deluge systems so we enable a sustainable future for spaceflight while also taking care of the resources that we use here on Earth. These innovations will help us pave the way to continue the next generation of space exploration.



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This is KYNNMASTER 123 for The Weekly Spaceman, see you in the next one! 😊

KYNNMASTER 123
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