Artemis III Booster Stacking Reaches Four of Five Segments as Orion Heat Shield Fix Confirmed

Teams at NASA's Kennedy Space Center have stacked the next pair of solid rocket booster segments for the Artemis III Space Launch System inside the Vehicle Assembly Building, advancing hardware toward flight readiness. The progress coincides with post-flight analysis of Orion's Artemis II heat shield, which confirmed that a modified reentry profile sharply reduced the char loss seen after Artemis I.

The Artemis Safety Advisory Panel reviewed the Orion results after nearly five months of analysis. NASA had chosen not to remanufacture the Artemis II heat shield, which was already installed, and instead flew a steeper, non-skip reentry to address the permeability issue that caused char loss on Artemis I. That decision avoided a mission delay while imposing higher heat loads on the vehicle.

NASA completed mating of the center segments on the twin five-segment boosters for Artemis III and has begun stacking the forward center segments on top of those. Only the forward assemblies remain to complete each booster stack. Photographs from the base of Mobile Launcher 1 show the Tail Service Mast Umbilicals missing their quick-disconnect plates, which may reflect a design change to address leaks found during Artemis II processing, or may be part of post-Artemis II refurbishment of the launcher.

Inside the VAB, teams completed installation of all four RS-25 engines on Core Stage-3, opening the remaining outfitting work before the stage can be transferred onto Mobile Launcher 1 between the boosters. Artemis IV hardware is also moving in parallel. NASA's Pegasus barge delivered the boattail, the last major piece needed for the Core Stage-4 engine section, which has been in processing at Kennedy for years. The boattail attaches to the engine-section barrel and provides aerodynamic support for the RS-25 engines in flight. NASA is targeting a 2028 lunar landing on Artemis IV.

Artemis II lifted off April 1, becoming the first crewed Artemis flight and the first human mission around the Moon since 1972. It flew with the same class of Avcoat heat shield already installed when inspection of Artemis I revealed unexpected char loss. The issue was permeability. During reentry, Avcoat heats, gasifies, and ablates, but if the outer layers are too permeable, gas from below cannot escape, building pressure that can blow out upper layers in a process known as spallation.

Panel member Paul Hill, a former NASA flight director and MOD Director, said Artemis I's heat shield had more than 100 spallation sites, while Artemis II had only nine, a reduction of more than 90 percent from changing the entry profile alone. The trade is operational. Skipping the skip shortens the distance from entry interface to splashdown and reduces the area NASA can target, cutting mission-planning flexibility. To restore skip-entry capability, NASA has changed Avcoat manufacturing so the material is more permeable and can vent gases rather than trap them.

The revised process will fly first on Artemis III next year and will be used on subsequent Orion heat shields. Steady stacking progress plus the confirmed Orion fix are concrete milestones shaping the mission's timeline.

The VAB work now underway is the next test of whether the hardware cadence can keep Artemis III and IV on their intended paths, including the remaining components still to be integrated into the stacks.