SLS Water Suppression Can Create Dangerous Pressure Spikes, NASA Simulations Show

Before Artemis II leaves the ground, NASA ran the numbers twice on what happens when a giant rocket plume meets a wall of water.

NASA released details this week of a computational fluid dynamics study using its in-house LAVA framework — Launch, Ascent, and Vehicle Aerodynamics — applied to the Artemis II launch environment at Kennedy Space Center. The work focused on the interaction between SLS's exhaust plume and the mobile launcher's sound suppression system: up to about 450,000 gallons per minute of water dumped onto the deck at ignition to protect the rocket and ground equipment from acoustic loads that can exceed 170 decibels.

The simulation work, conducted at NASA's Ames Research Center using flight data from the 2022 Artemis I launch, showed that the water suppression does what it's supposed to do — it cuts the peak sound pressure at the pad. But the plume doesn't simply dissipate into the water curtain. The exhaust gas flow can redirect the water in ways that create localized pressure spikes in specific areas of the launch platform structure.

That finding drove real hardware changes. Engineers at Kennedy used the LAVA output to refine the design plume pressure estimates for the mobile launcher and adapted the platform to handle those loads for crewed flight. NASA is not describing the modifications in detail, but the agency confirmed the work affected structural considerations for the mobile launcher that supports SLS and Orion before and during launch.

The LAVA framework itself is notable apart from this specific application. It handles compressible flow — the regime where gases move at speeds comparable to or faster than sound, which is exactly what's happening in a rocket exhaust plume at sea level. Running that kind of simulation with enough fidelity to capture the water-gas interaction at the pad required validated models against Artemis I data. NASA says it plans to release LAVA to the aerospace community in the coming weeks, hosted through its Aeronautics research program, so companies and researchers can run their own plume and acoustics simulations.

This is the unglamorous end of pre-flight preparation: not the headline hardware, not the astronaut quarantine, but the invisible engineering work that keeps the headline hardware and the astronauts from getting shaken apart by their own launch. The sound suppression system is easy to take for granted — water goes up, noise goes down, everyone is happy. The plume interaction problem took a proper CFD tool and actual flight data to characterize, and it produced changes that NASA apparently considered load-bearing for a crewed mission.

Artemis II is currently at Pad 39B after an overnight rollout Friday. The April 1 launch window opens in less than two weeks.