SLS Undergoing Final Test Before Launch

By: Michael Piper, Junior

Starting on April 1st, NASA’s SLS, or Space Launch System, began its final and biggest test before it launches the Artemis 1 mission. This test, called the Wet Dress Rehearsal, is the final checkout of a fully integrated rocket and all the systems that enable a launch – including the ground crew. The test simulates a full launch procedure from 45 hours prior to T-0, but stops short of igniting the four main engines or the two solid rocket boosters.

  The mission control team were summoned to their stations at 5 PM on April 1, 45 hours before a simulated T-0. The water tank for the sound suppression system was filled shortly after, and the Orion spacecraft and core stage were powered up over the next few hours.

   The next day, final checkouts of the main engines were completed and flame deflectors were moved into launch positions. That night, four lightning strikes hit the launch complex, but caused no damage thanks to the three massive lightning towers arranged around the launch pad.

   April 3 marked the day for T-0. At L-12 hours the second stage was powered up and the launch complex was evacuated. The launch team then reviewed the weather and polled on whether to begin filling the propellant tanks. Before tanking preparations could begin, however, the launch team was unable to pressurize the mobile launcher and scrubbed for the day.

   On April 4, the team resolved the pressurization issue and conducted propellant line chilldown, cooling down the oxygen and hydrogen transfer lines to prevent damage from sudden contact with the cryogenic fluids during fuelling. Shortly after oxygen began to flow into the rocket, the team encountered an issue with an oxygen temperature sensor, but were able to fix the issue and continue tanking. They managed to fill the oxygen tank around halfway, at which point hydrogen was supposed to begin filling its own tank. However, a hand-operated valve in the hydrogen fill system had accidentally been left closed, and tanking was aborted.

   At this time, the wet dress rehearsal has been delayed to after SpaceX’s Axiom-1 launch, which will launch the first all-private space station crew this Friday.

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