NASA’s Space Launch System, the other Saturn V-class heavy lift vehicle launched this decade, is being prepared for its second flight and its first crew-carrying flight, even as issues with the Orion spacecraft threaten to further delay Artemis II. While Artemis II preparations are underway, future upgrades to SLS are also being worked on.
Artemis II’s core stage, solid rocket booster (SRB) segments, and launch vehicle stage adapter (LVSA) are at the Kennedy Space Center (KSC) and being stored prior to stacking. The core stage and all four RS-25 engines arrived on the barge Pegasus to the KSC turn basin as a unit on July 23 this year while the SRB segments arrived by train to KSC from Utah on Sept. 25, 2023.
The LVSA, fabricated at the Marshall Space Flight Center (MSFC) in Alabama, arrived aboard Pegasus at KSC on July 29, six days after the core stage’s arrival. The core stage is in the VAB transfer aisle and has had its mass and center of gravity measured. The SRB segments are in the rotation, processing, and surge facility (RPSF) while the LVSA is in the VAB’s high bay 4.
The SLS Artemis II core stage is being moved into the VAB on July 23, 2024. (Credit: NASA/Isaac Watson)
The ICPS-2 upper stage, based on the Delta IV second stage, is in the ULA Delta Ops Center at the Cape Canaveral Space Force Station, while the Orion launch abort system (LAS) is in the launch abort system facility at KSC. The only part of the Artemis II SLS launch vehicle that still needs to be delivered is the Orion stage adapter, currently at MSFC, that connects the ICPS to the Orion service module.
The Mobile Launcher 1 (ML1) rolled back from Pad 39B to the Vehicle Assembly Building (VAB) on Oct. 3 and was placed inside High Bay 3 the following day. The ML1 rollback has been considered a watch item for when stacking would begin for Artemis II, but the stacking timeline is now uncertain due to issues with the Orion command module’s heat shield.
ML1 is in High Bay 3 for the first time since January 2023. After the Artemis I flight, repairs were needed to the structure due to damage incurred from the launch. Elevators on the tower were damaged, and some pneumatic lines were damaged. This prevented a 35-minute automatic washdown of the structure after launch to prevent corrosion damage from the exhaust of the solid rocket boosters.
The emergency crew egress system on ML1 is shown here during testing. (Credit: NASA/Kim Shiflett)
Corrosion developed in ML1’s piping due to a five-day delay of the washdown, which was performed manually. While ML1 was at the west park site near the VAB, repairs to the piping were started on the structure. After ML1 was rolled out to Pad 39B in August 2023, the crew emergency egress system was installed. Upgrades to the sound suppression system and other items were also conducted along with a number of tests.
Prior to ML1’s rollback to the VAB, an I-beam was installed on the tower. This will enable the installation of a contingency pad access system, which is still being designed. NASA wants to use this access system to allow for changing an expired flight termination system (FTS) on the pad.
The need to roll back to the VAB for changing the FTS was a point of discussion during the Artemis I launch delays after its initial launch attempt.
ML1 is now being prepared for stacking the Artemis II launch vehicle, and these preparations would take approximately three to four weeks. However, NASA wants to make its decision on the forward path for the Orion heat shield before starting the stacking process. After Artemis I’s return, divots were found in the Orion heat shield, and NASA needs to understand this – and any redesigns or other mitigations needed – before proceeding with Artemis II.
Ten booster segments for Artemis II arriving at KSC by train. (Credit: NASA)
There will be a checkpoint meeting two to four weeks before stacking begins, whenever that might be, and this meeting could theoretically happen as early as the end of October. This is an item to watch along with the heat shield decision. NASA typically wants to stack the SRBs no more than one year before launch, though this was analyzed and waived before Artemis I’s flight due to repeated delays.
Artemis II is currently scheduled for launch in September 2025 with a crew of four astronauts, though the schedule is subject to change pending NASA’s decision on the Orion heat shield. Astronauts Reid Wiseman, Victor Glover, Christina Koch, and Canada’s Jeremy Hansen are currently in training for the flight.
Some SLS hardware for Artemis III and Artemis IV is at KSC as well. The Artemis III SLS engine section and boat-tail are in the Space Systems Processing Facility (SSPF) while the other elements of the core stage are scheduled for delivery in 2025. If they arrive later in that year, then the Artemis III core stage won’t be complete until 2026.
The engine section for Artemis IV is shown leaving the Pegasus barge at KSC. (Credit: NASA/Justin Robert)
Artemis IV requires a new ML – ML2 – due to the mission being the first use of the Block 1B variant of SLS. The Block 1B will use a new upper stage known as the Exploration Upper Stage (EUS). ML2 is designed to accommodate the EUS and is currently under construction at KSC with fabrication 70 percent complete and construction 25 percent complete, though the project is dealing with cost overruns and delays.
Artemis III, the first human lunar landing of the program, is currently scheduled for September 2026 while Artemis IV, the first flight of Block 1B and a Gateway assembly flight, is scheduled for September 2028. However, those dates are subject to change as many elements of these missions are still in work.
The core stage engine section for Artemis IV is also at KSC, having arrived on the Pegasus barge at the same time as the Artemis II LVSA and Artemis III engine section boat-tail. The engine section will be added to the core stage once the core has arrived at KSC, as opposed to being delivered as a single unit as was done with Artemis I and II.
A BOLE segment is shown being transported for final assembly. (Credit: Northrop Grumman)
Besides a new upper stage, which will allow the crew and heavy cargo to be flown to the Moon with one launch, an upgraded solid rocket booster with composite cases is also planned for future SLS missions. The Block 2 SLS will use the same core stage and EUS as Block 1B but will replace the SRBs with upgraded versions that will use lighter composite cases.
The first full-scale test article of the upgraded SRB, known as the Booster Obsolescence and Life Extension motor (BOLE), is currently scheduled to be fired in the spring of 2025 at the Northrop Grumman facility in Promontory, Utah. Block 2 and its BOLE boosters are scheduled to be used for Artemis IX, the ninth mission of SLS, which could occur sometime in the 2030s if the program is still operational.
(Lead image: The SLS Mobile Launcher 1 is moving into High Bay 3 on Oct. 4, 2024. Credit: NASA/Ben Smegelsky)
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