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The Shuttle, in addition to the water deluge system, used a series of red nylon bags filled with water at the base of each SRB for additional sound suppression. Does the SLS, whose boosters produce ~300,000lbs more thrust, have the same system? It’s not clear to me from images or footage.

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    $\begingroup$ nasatech.net/SSSTest4_PAGE.html and other pages suggests that the bags were part of the IOP/SS design to alleviate the damage to the platform seen after STS-1, and that this was based on empirical data that was superseded by new computational fluid dynamic data produced for SLS that subsequently led to a redesign of the system - and may have removed the requirement for the bags (though not explicitly stated); nas.nasa.gov/upload/files/sc18posters/… $\endgroup$
    – blobbymcblobby
    Commented Feb 6, 2023 at 21:59
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    $\begingroup$ @blobbymcblobby agreed, I can't find a reference, but IIRC the red "water sausages" were provided mainly to alleviate sound pressure effects on the Orbiter's wings, which wouldn't be needed for SLS. SLS also has a single opening in the MLP for all the engines unlike STS which had 3, so it's pretty different. $\endgroup$
    – Organic Marble
    Commented Feb 6, 2023 at 22:06
  • $\begingroup$ Ah, yes, you made it much clearer actually; I read something about alleviating potential damage back to the shuttle but I forgot about the wings (no bags under the orbiter)! My comment is obviously incorrect - but the links were interesting! :P (I suppose the answer would be along the lines of: no wings, no bags) $\endgroup$
    – blobbymcblobby
    Commented Feb 6, 2023 at 22:58

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The SLS launch pad does not have the same system.

I haven't found a source with an explicit statement that says no, but I can give a sourced explanation of why the shuttle pad had the red water sausages, and why the SLS does not need them.

The red water sausages were on the shuttle pad because:

Specifically, the red water bags are used to dampen the wave of sound energy that is reflected back up toward the Space Shuttle when the Solid Rocket Boosters ignite during launch. If this powerful pulse of pressure were not suppressed, it would create a dangerous stress on the wings of the orbiter.

Source: Red Water Sausages

Note that the holes in the shuttle pad for the SRB plumes are elongated towards the left of the picture. If the holes were not so big, the pulse couldn't reflect up through them, and the red water sausages would not be needed. So why are the holes so big?

They had to be elongated to the left, because when the shuttle lifted off, it translated to the left due to the angle that the Space Shuttle Main Engines were mounted at. There was a horizontal component of thrust that pushed the stack to the left when it was still low over the pad; so low that the SRB plumes would still have damaged the pad surface.

The impingement pattern in the SRB exhaust holes changes during the 1.5 - 4 sec interval because the Vehicle is rising and also because it drifts in the Vehicle body axis plunging direction, Pad north (Vehicle -ZT coordinate direction), due to the thrust vector of the SSMEs.

Source: Space Shuttle and Launch Pad Computational Fluid Dynamics Model for Lift-off Debris Transport Analysis

You can see this northward drift in the following slow motion launch video starting at 17:47

Put your cursor on the SRB system tunnel and leave it in place. By the time it leaves the field of view at 18:40, the leftward drift is obvious.

This graph shows some actual northerly drift values (BET stands for Best Estimate Trajectory):

graph of altitude vs drift. Max drift is about 35 feet over 350 feet of rise

Source: Space Shuttle and Launch Pad Lift-Off Debris Transport Analysis - SRB Plume-Driven

The SLS doesn't have this built-in drift at launch phenomenon - its engines and motors point straight down - so its launch pad hole does not have to be so elongated. It only has to allow for drift due to ground winds and vehicle dispersions.

photo of hole in SLS launch pad

Photo source: Teams Assess Mobile Launcher and Pad After Successful Artemis I launch

So

  • The red water sausages were provided mainly to protect the Orbiter's wings
  • The SLS doesn't have wings
  • The extra protection was required because of the elongated holes in the MLP deck that allowed the pressure wave to reflect up through them.
  • The SLS hole is not elongated

Finally, if the red water sausages were placed in the SLS launch pad hole, they would instantly be destroyed when the engines / motors lit, since they would be directly in the plume. You can see in the linked video that the red water sausages survive the moment of liftoff...until the SRB plumes drift over them.

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