Prime contractor Boeing rolled out the second Space Launch System (SLS) Core Stage on July 16 from the Michoud Assembly Facility (MAF) and secured it to NASA’s Pegasus barge for transportation to the Kennedy Space Center (KSC) in Florida over the next several days. The stage will control the beginning of the Artemis II mission that will send a four-person crew on an Orion spacecraft on a lunar flyby; the question now is when that mission will happen.
Launch of Artemis II was retargeted for September 2025 this past January, but NASA is still reviewing results from Artemis I and monitoring the progress of Artemis II Orion spacecraft assembly and test. An overall status review is currently planned for mid-September of this year to see if stacking of the SLS for Artemis II can begin.
Core Stage-2 leaves Michoud
The stage was rolled out of the transfer aisle of Michoud’s Vertical Assembly Building, Building 110, beginning around daybreak on July 16. It was backed out of the building on NASA’s transportation equipment and self-propelled modular transporters (SPMT).
After the whole stage was out of the building into the tarmac area, the Boeing move team swung it around so that the forward end was pointing out the area gate. The move went smoothly and faster than expected.
A ceremony to celebrate the workforce’s completion of the stage started as it left the area and by the time the festivities were over, the stage was well out of view and the Boeing move team had already covered nearly half of the over one-mile trip to the Pegasus barge. By mid-day, the core stage was rolled on the barge and securing operations began.
Core Stage-2 rolls onto NASA’s Pegasus barge on July 16. Credit: NASA/Evan Deroche.
Rollout of the Artemis II core stage occurred four and a half years after rollout of the first unit. Turmoil from the COVID pandemic and continued effects on the supply chain of parts for the vehicles delayed delivery from 2022 until now.
Final integrated testing of Core Stage-2 was completed in late January of this year, but the stage was kept in storage at Michoud in New Orleans for the first half of the year. NASA delayed Artemis II from late 2024 to September 2025 in January to provide more time for teams to work on understanding the in-flight performance of the Artemis I mission and resolving other issues discovered during production of hardware for future flights.
In early June, NASA and Boeing set a rollout date of mid-July and began the final few weeks of shipment preparations. “The weather looked good, the path looked good, and we have more work to do [at Michoud], we have more rockets coming through [the factory], so we wanted to clear this one out,” Amit Kshatriya, NASA deputy associate administrator for the Moon to Mars Program, said in a media question and answer session at the July 16 rollout.
Internal work platforms were removed and access doors to the intertank and engine section areas were bolted in place, covers were placed over umbilical plates, engine heatshields, antennas, and other exterior equipment, and scaffolding surrounding the vehicle was moved out of the way.
That allowed the stage to be rotated around its long axis to facilitate pre-shipment thermal protection system (TPS) work and installation of fairings on the engine section and boattail. Following completion of all that work in the final assembly area, the stage was moved to the Building 110 transfer aisle.
The Artemis II core stage rolls out of final assembly at MAF on July 6 for final shipment preparations. Credit: NASA/Michael DeMocker.
In the transfer aisle, the two heavy cranes in the building lifted the stage up so that the factory handling equipment and transporters could be exchanged for the outdoor, overland versions. A temporary weather cover was also placed on the front of the stage, over the forward skirt; it is different from the white weather cover that was used for the first core and will be used on the first Exploration Upper Stage (EUS) flight article.
Both core stage and EUS first flight articles go through a Green Run design verification campaign at the Stennis Space Center, where they will be in the B-2 Test Stand outside for months. In contrast, the Artemis II core stage is only expected to be outside in this configuration for a handful of hours.
When will the Core Stage be stacked for Artemis II?
Pegasus will be towed from New Orleans out into the Gulf of Mexico, around the Florida Peninsula, and then eventually to Port Canaveral and the Kennedy Space Center. The trip is expected to take somewhere around a week; for security, NASA typically does not provide progress reports on the trip.
After the stage arrives at the KSC Turn Basin dock on Pegasus, Boeing will officially transfer ownership to Exploration Ground Systems (EGS) for launch processing. Arrival at KSC will leave only the two connecting adapters for SLS that need to be shipped to the launch site, the Launch Vehicle Stage Adapter (LVSA) and the Orion Stage Adapter (OSA).
The solid rocket booster (SRB) hardware is stored in the Rotation Processing and Surge Facility (RPSF) and the Interim Cryogenic Propulsion Stage (ICPS) is stored at nearby Cape Canaveral Space Force Station (CCSFS); both are ready to support stacking when the decision is made.
The SLS program is continuing to analyze the performance of the rocket during the Artemis I launch on November 16, 2022, updating models and making improvements. NASA and Boeing will finish work at KSC to closeout in-flight anomalies (IFA) identified with vibrations measured on the core stage and debris liberation during the launch.
“[Boeing did] most of the work here at Michoud [and] we’re going to finish it up in the [Vehicle Assembly Building] transfer aisle or in the High Bay when we get it out to Kennedy,” Kshatriya said. “So they’re going to be able to get those anomalies resolved before we even start the stacking process.”
In addition, EGS and prime launch processing contractor Jacobs will make final stacking preparations, installing flight termination system (FTS) components in the stage’s systems tunnel.
The Artemis II Orion spacecraft is moved to an altitude chamber for vacuum testing on June 28. Credit: NASA/Rad Sinyak.
Final assembly and test of the Orion spacecraft for Artemis II, the first, all-up, crewed build, is the critical path to begin launch processing and eventually readiness for launch next year. The spacecraft was recently moved back into an altitude chamber in the Neil Armstrong Operations and Checkout Building at KSC to begin vacuum testing.
That testing was expected to start in late June shortly after installation into the altitude chamber and take a couple of weeks to setup, execute, and wrap-up; an update was anticipated after the test and the spacecraft was removed from the chamber. The investigation and findings about the Orion heatshield performance during the Artemis I re-entry, and recommendations about corrective actions are also still under independent review.
In addition, Mobile Launcher-1 is still out at Launch Pad 39B, continuing integrated systems verification and validation testing; the ML will need to be rolled back to VAB High Bay 3 at KSC to get ready for stacking of the Artemis II vehicle.
The Moon to Mars Program Office will hold a checkout review near the end of the summer to decide when to begin stacking, beginning with the SLS boosters. “There’s a lot of things that factor into that stacking decision,” Kshatriya noted.
“Of course once we get the boosters up we start a clock on the migration of the propellant, so we need to make sure we do that smartly and kind of manage that with the processing of the spacecraft. [That] is going well, they’re working really hard but all roads are kind of heading to that mid-September timeframe [to review progress and make a decision].”
(Lead image: The Artemis II core stage rolls out of the Michoud Assembly Facility on July 16. Credit: Philip Sloss for NSF.)
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