Inside the Artemis ground launch sequencer—a system crucial for the launch of the Moon mission
NASA is all but ready for lift-off of its landmark Artemis II mission, with the launch window opening at 6:24 pm EDT tonight. Along with many of the countdown activities, such as powering on the Orion capsule, the core stage, and the upper stage, the activation of the ground launch sequencer (GLS) has also been completed, with the tanking process currently underway.
What is the ground launch sequencer?
The GLS is an automated system that operates thousands of commands in the final minutes of the launch countdown and manages valve movements and timing cues that prepare the rocket for the terminal count. At T-33 seconds to liftoff, the GLS passes the command over to the automated launch sequencer.
Background of GLS
The GLS was first demonstrated for use in the Artemis program by the Ground and Flight Application Software team in 2017, with the Artemis Launch Director, Charlie Blackwell-Thompson, overseeing the demonstration in Firing Room 3 in the Launch Control Center at the Kennedy Space Center in Florida. Part of the GLS's function is to support the suppression stage that releases a deluge of water when over 8 million pounds of thrust is released by the rocket’s RS-25 engines and the boosters during liftoff. This ensures that the vehicle remains protected from the vibrations it creates at launch.
Further development of GLS took place as the preparations were ramping up for Artemis I, the only flight of SLS prior to this first crewed mission. In December 2021, the Exploration Ground Systems team carried out a demonstration of the GLS again for conducting countdown sequencing. The GLS ran without any issues, and so engineers conducted another test to take the variations between the emulator and flight hardware identified during the initial countdown sequencing test into consideration. Thanks to these validations, during the launch of Artemis I on November 16, 2022, the GLS performed nominally and helped make the SLS test flight a success.
NASA will be hoping that everything, including the GLS, functions nominally today, especially given how the mission has already suffered a number of delays. Artemis II will validate the systems aboard the Orion spacecraft and provide invaluable learnings for the development of Artemis III and subsequent missions for building a Moon Base.
