“Nasa tests out the water deluge system for its new Space Launch System (SLS). The Ignition Overpressure Protection and Sound Suppression (IOP/SS) system releases two million litres (450,000 gallons) during take-off to dampen the huge shockwaves and heat of a rocket launch. It has been in place since the Space Shuttle but has been upgraded for the SLS“
Elon Musk does not use it.