NASA stacks Artemis III's SLS boosters for pad tanking test

Inside the Vehicle Assembly Building at Kennedy Space Center, the two five-segment boosters of NASA's Space Launch System now stand complete. Engineers finished the stack on September 30, when the nose cones were mated to the left and right forward assemblies in High Bay 3. The work had started in mid-July on Mobile Launcher 1 with the aft segments, then continued through August with the center sections before the forward assemblies closed the stacks.

The Core Stage, the large tank that feeds the engines, has kept pace in High Bay 2. After the tank section arrived from the Michoud Assembly Facility and was joined to the engine section, teams installed all four RS-25 engines. The next task is fitting the systems tunnel, a passage that runs the length of the stage and carries the cabling for the single-use quick-disconnects used at liftoff. Only then will the Core Stage be mated to the boosters, in the coming weeks, to form what NASA calls the short stack: the rocket without its upper-stage adapters, spacer and Orion spacecraft.

That short stack is destined for Launch Pad 39B, where it will undergo a tanking test, expected in the coming months, to rehearse propellant loading timelines and procedures. The launch team will practice on a real vehicle at the pad before the flight itself. The crew will use the same visit for its own rehearsal: commander Randy Bresnik, mission specialists Frank Rubio and Andre Douglas, and ESA pilot Luca Parmitano will suit up, ride to the pad, climb the mobile launcher and walk the emergency exit route they would use during an off-nominal countdown.

For the astronauts, this is the difference between a checklist and a dress rehearsal. For the program, it is a way to retire risk early. Artemis III, targeted no earlier than June 2027, will remain in low Earth orbit, where Orion and its four-person crew will test docking and other operations with the commercial lunar modules built by SpaceX and Blue Origin. NASA says these objectives are intended to clear key risks before the first crewed lunar landing attempt on Artemis IV. Pad work is already moving: at Launch Pad 39B, the flame deflector is being refurbished after the Artemis II launch, with damage described as minimal.

The rest of the hardware is on the same track. At Marshall Space Flight Center, the spacer's primary structure is complete and is being checked before it ships to Kennedy early next year. The Orion Stage Adapter is painted and awaits cable and bracket installation, and the Launch Vehicle Stage Adapter is nearing the end of corrosion removal, with nondestructive evaluation scheduled for this fall. NASA says the adapters remain on schedule to join the short stack after the tanking test.