On April 20, 2026, the upper four-fifths of NASA's Artemis III Space Launch System core stage began its journey from the Michoud Assembly Facility in New Orleans to Kennedy Space Center in Florida. Engineers loaded the 212-foot section onto the agency's Pegasus barge, sending the hardware on a roughly 900-mile waterway transit that will set the stage for one of the most consequential rocket builds in NASA history. The section carries the liquid hydrogen tank, liquid oxygen tank, intertank structure, and forward skirt — the structural backbone of the SLS rocket that will carry the Artemis III crew toward the Moon. It is the first core stage hardware to leave the factory under the revised Artemis architecture , which reassigns the translunar injection burn to SpaceX's Starship while SLS delivers Orion to low Earth orbit. AI-generated image The Pegasus barge moves SLS hardware along inland waterways to Kennedy Space Center. Credit: AI illustration What Left the Factory on April 20 The section that rolled onto Pegasus is not the complete core stage. NASA is using a new parallel-integration approach for Artemis III: the upper portion ships from Michoud now, while the engine section, housing all four RS-25 engines, ships separately from Stennis Space Center in Mississippi. The two pieces will be mated at KSC's High Bay 2 for final outfitting before the stage moves to the Vehicle Assembly Building for stacking with solid rocket boosters. NASA confirmed the engine section delivery to KSC is targeted for mid-July 2026. That timeline gives technicians roughly three months to complete the engine section work at Stennis, arrange barge transit, and arrive at the Cape ahead of stacking operations. The approach differs from previous Artemis campaigns, where the full assembled core stage arrived at KSC as a single unit. AI-generated image Technicians working inside Michoud's high bay alongside SLS core stage hardware. Credit: AI illustration Boeing, which builds the core stage under a NASA contract, flagged several production improvements baked into this unit. Transporters used for the April 20 rollout carry safety upgrades learned from previous core stage moves. Boeing manufacturing director Rick Hoepfner told reporters the team's guiding principle remains what he called "moving at the speed of safe," a phrase the company has leaned on through a production program that stretched years beyond its original schedule. Core Stage 3 by the Numbers The upper section that departed Michoud on April 20 is 212 feet tall and contains the propellant tanks that hold 537,000 gallons of liquid hydrogen and 196,000 gallons of liquid oxygen — enough cryogenic propellant to power all four RS-25 engines through the roughly eight-minute ascent to Earth orbit. SLS in the Post-Artemis II Architecture The core stage hardware heading to KSC will power a mission profile that looks quite different from what NASA originally planned. Under the architecture revision NASA announced in March 2026, SLS's job for Artemis III is to deliver the Orion capsule and crew to low Earth orbit, not to fire the translunar injection burn. Starship takes over from there, docking with Orion in LEO and executing the burn that pushes the combined stack toward the Moon. The change was driven partly by schedule, partly by Starship's expanding role in NASA planning. SpaceX's Human Landing System contract was already worth billions before the architecture shift. Now Starship carries even more of the operational weight. Artemis III, targeted for 2027, will not attempt a lunar surface landing. That milestone moves to Artemis IV in 2028, once the Lunar Gateway has been deployed and a full surface access architecture has been flight-tested. 2027 Artemis III target launch year 212 ft Upper core stage section height ~900 mi Barge transit distance to KSC 4 RS-25 engines (shipping separately) Jul 2026 Engine section target delivery 2028 Artemis IV crewed lunar landing target What this means for the hardware now on Pegasus: the core stage arriving at KSC will be stacked and processed for a mission that proves out the new Earth-orbit rendezvous procedure between Orion and Starship HLS. NASA has never flown a rendezvous-and-docking in this configuration before. Getting it right in 2027, without a surface landing to complicate the risk picture, is the whole point of the Artemis III mission as restructured. The Ground Campaign Taking Shape at Kennedy AI-generated image The Vehicle Assembly Building at KSC, where SLS stacking will take place. Credit: AI illustration Several Artemis III ground milestones have already been ticking over at KSC this month. On April 17, NASA rolled the mobile launcher back from Launch Pad 39B to the VAB, clearing the launch complex and beginning the turnaround sequence after Artemis II. The first left-hand solid rocket booster segment arrived at the Rotation, Processing and Surge Facility even earlier, meaning SRB stacking can begin well before the core stage arrives from Michoud. The Pegasus barge typically takes several weeks to complete the transit from New Orleans to Port Canaveral. Once it arrives, teams will offload the upper core section and move it to High Bay 2 for the join with the engine section. That mating operation, along with functional testing and systems checkouts, will run in parallel with SRB work in the VAB before the fully assembled stack is moved to the high bay for integration. Artemis III KSC Milestone Sequence • Apr 17, 2026: Mobile launcher rolls back to VAB from LC-39B, Artemis II turnaround begins. • Apr 20, 2026: Upper core stage section departs Michoud on Pegasus barge. • May 2026 (est.): Upper core stage arrives at Port Canaveral, begins High Bay 2 processing. • Jul 2026 (est.): Engine section departs Stennis Space Center for KSC. • Late 2026 (est.): Core stage mating complete, SRB stacking underway in VAB. • 2027 (target): Artemis III launch window; Orion and crew to LEO for Starship rendezvous test. Cadence, Costs, and Whether This Schedule Holds The Artemis II crew returned to Earth in mid-April after the successful lunar flyby, giving NASA a post-mission glow that has been conspicuously absent from previous program phases. Administrator Jared Isaacman's team moved quickly to translate that momentum into visible forward progress, and the core stage rollout one week after splashdown is the clearest sign yet that the agency intends to treat turnaround cadence as a communication tool, not just an engineering objective. Whether the schedule holds is a different question. The SLS program has rarely met its original timelines. The Artemis I core stage spent years at Michoud before shipping. Artemis II's core stage required a rollback and repair for a helium fault. The production lessons from those experiences are baked into Core Stage 3, at least on paper, but the parallel engine section approach introduces a new integration challenge at KSC that has not been attempted before under Artemis. Mission Core Stage Shipped Launch Objective Artemis I Jan 2021 Nov 2022 Uncrewed Orion lunar flyby Artemis II Oct 2022 Apr 1, 2026 Crewed lunar flyby, heat shield validation Artemis III Apr 20, 2026 (upper section) 2027 (target) LEO rendezvous with Starship HLS Artemis IV TBD 2028 (target) First crewed lunar surface landing since Apollo Budget pressure adds another variable. Congress has directed NASA to hold SLS production costs flat or reduce them, a difficult ask when Boeing and Aerojet Rocketdyne (which manufactures the RS-25 engines) face their own supply chain challenges. The Centaur 5 upper stage, which ULA is now contracted to provide starting with Artemis IV after the Boeing Exploration Upper Stage program was canceled, is proceeding on its own development track and not a factor for Artemis III. What Artemis III Actually Has to Prove AI-generated image Artistic rendering of an SLS night launch from LC-39B at Kennedy Space Center. Credit: AI illustration The revised Artemis III m