Shhhh! Suppressing Sound Waves From Rocket and Space Shuttle Engines
In case you have not noticed, rockets can be really loud. Sound suppression on vertically launched rockets (and the Space Shuttle, back when it was flying) is more important than most of you would think. And for a different reason than most of you would guess.
Every so often I get to talk about my first job which was in the aerospace industry where I first learned about sound suppression systems. Today AFT software is used on several of these systems by our customers in the aerospace industry as well as NASA.
The flowrate of water used in the sound suppression process is enormous. Which is why they are often called "deluge systems".
The peak flow rate on the Space Shuttle deluge system was 900,000 gpm (200,000 m3/hr). That is not a typo! For reliability, the entire system is gravity driven from a 290 ft (88 m) tower. See photo below.
Below, photo I took in 2013 of Space Shuttle Launch Complex 39 with Deluge System Tower at right
The purpose of the deluge system is not to protect the ground systems. It is to protect the flight vehicle. When rocket engines are started the acoustic pressure waves can reflect off the ground and come back and hit the bottom of the vehicle before it is clear of the launch tower. The forces involved can damage the vehicle. The deluge system essentially breaks up the acoustic waves and thus protects the vehicle.
Below, photo I took in 2013 of pipes that delivered water to the Space Shuttle launch pad
Below, photo of me in 2013 in front of pipes that delivered water to the Space Shuttle launch pad - I could not find out the diameter but these look like 36-48 inch (1 - 1.2 m) diameter in size
AFT has two case AFT Impulse studies of sound suppression deluge systems as submitted by Reynolds, Smith & Hill (RS&H):
- AFT Impulse Simplifies Design of Complicated Water Deluge System
- AFT Impulse Allows Space Launch System Expansion with Minimal Environmental Impact
AFT Impulse is used to predict the amount of flow and how the flow distributes spacially and over time.
NASA is currently working on a new deluge system configuration for the Space Shuttle follow-up system the Space Launch System (SLS) at Complex 39b. AFT Impulse is being used on that also. See this link for more info: https://www.nasa.gov/exploration/systems/sls/sls-acoustic-testing-2014.html
Below is a video of the reconfigured deluge system for SpaceX at Complex 39a (one of the old Space Shuttle launch pads).