NASA officials confirmed that the first SLS core stage had not suffered any damage following an anomalous static fire test that was automatically aborted 60 seconds into an eight-minute burn.
During a January 19 media briefing, agency officials announced that preliminary inspections had shown that the first Space Launch System (SLS) core stage to roll off the assembly line is in excellent condition following the aborted Green Run test. According to officials, the early abort was triggered by intentionally conservative test parameters to ensure the safety of the stage during testing.
The January 16 Green Run static fire test saw the SLS core fired for the first time. The stage’s four RS-25 engines were ignited at 22:27 UTC. Shortly after ignition, teams noted an MFC, or main component failure, in engine number four. Just over 60 seconds later, all four engines were automatically shut down.
As part of the testing, the stage’s thrust vector control (TVC) system gimbaled the engines to simulate how the TVC would be used during flight to direct the rocket’s ascent. Approximately 67 seconds into the test, the hydraulics of the actuators that power the TVC in Engine 2 exceeded pre-set test limits. This in turn triggered an automatic shut down that is designed to ensure the stage does not suffer any damage during testing. If this scenario occurred during flight, redundancy in the system would compensate allowing the mission to continue without incident.
According to NASA officials, the MFC and the engine shut down were the result of two separate issues. The MFC was triggered after the loss of one leg of redundancy in Engine 4 prior to T-0. The testing conditions were such that the startup was allowed to continue despite the loss. Teams will be required to investigate Engine 4 before moving forward.
With the stage largely receiving a clean bill of health, the discussion has shifted to whether an additional static fire test will be conducted before it’s shipped to the Kennedy Space Center (KSC) for launch preparations.
Former NASA Space Shuttle program manager and flight director Wayne Hale weighed in on the debate stating that the agency should retest and get complete data before proceeding. However, according to a January 19 NASA statement, teams are still evaluating if a second static fire test will be necessary.
In addition to the possibility of requiring more data, the number of times the SLS core stage can be loaded with LOX and LH2 will also be a consideration in the final decision.
According to SLS prime contractor Boeing, the stage is designed to accommodate propellant loading a total of nine times. Currently, the stage has already used three of its nine lives – two for wet dress rehearsals and one for a static fire test. Additionally, a second static fire test will be required at KSC before the actual launch. As a result, the stage will use five of its nine propellant loads without any additional testing.
Prior to the January 16 test, NASA officials had stated that the Green Run static fire test would need to be completed without incident in order to allow for a late 2021 launch of the Artemis 1 mission. Despite the anomalous January 16 static fire test, NASA associate administrator of human exploration and operations mission directorate Kathy Lueders said that there was still a chance Artemis 1 could be launched this year.