Story by Jean Wright; KENNEDY SPACE CENTER, FL – NASA has completed stacking of the twin Solid Rocket Boosters (SRBs) motor segments destined for use on NASA’s Artemis III mission launching to low Earth orbit targeting NET later summer 2027 from NASA’s Kennedy Space Center in Florida.

Media including myself were taken on a tour inside the NASA’s Vehicle Assembly Building (VAB) in early October to capture the progress of the Artemis III five segment SRB assembly and stacking operations atop the mobile launcher inside the VAB High Bay 3 at NASA KSC

“Teams have completed the integration of the final solid rocket booster motor segments onto the mobile launcher for the “short stack” configuration that will be used during a tanking test,” NASA confirmed in a blog post on Oct. 13.

“Teams also completed installation of all four RS-25 engines on the SLS core stage.”

Enjoy our SRB stacking photos and core stage photos taken by Jean Wright for Space UpClose

“Each forward assembly contains an aerodynamic top, a forward skirt housing avionics, and frustum housing motors that allow the boosters to separate from the SLS core stage after launch.”

The twin solid boosters will help support the remaining rocket components and the Orion spacecraft during final assembly of the Artemis III rocket and provide more than 75 percent of the total SLS thrust during liftoff from NASA Kennedy’s Launch Pad 39B

“Teams now will install the systems tunnel that runs the length of the core stage and is used to route pyrotechnic cabling, a system of wiring that allows the single-use, quick disconnect for controlled movements during liftoff, on the massive stage. In the coming weeks, the stage will be integrated with the solid rocket boosters, completing the rocket’s “short stack” configuration,” NASA reported.

Thereafter the core stage will be transferred to High Bay 3 for integration with the twin stacked SRBs

Teams will then complete the assembly of the short stack configuration of NASAs SLS Artemis III rocket minus an upper stage and Orion crew capsule

NASA hopes to move the short stack to Launch Comple-39B by years end for tanking test with the cryogenic propellants to ensure their readiness for flight

“NASA will roll the short stack SLS rocket from the spaceport’s Vehicle Assembly Building to Launch Pad 39B for a tanking test in the coming months, where the Artemis launch team will practice procedures and timelines for loading propellant.”

Meanwhile at the pad, “the Artemis III crew, NASA astronauts Randy Bresnick, Frank Rubio, Andre Douglas, and ESA (European Space Agency) astronaut Luca Parmitano, also will conduct a launch day rehearsal and emergency exit walkdown. This will include suiting up in astronaut crew quarters, driving to the launch pad, ascending the mobile launcher, and then walking through the exit route they would take in the unlikely event of an emergency during launch countdown.”

Artemis III is projected to fly sometime in the second half of 2027 – but no specific target date has been announced

During a media event in Aug 2026, NASA Administrator Jared Isaacman told Ken Kremer of Space UpClose that he is “extremely confident” that NASA’s Artemis III mission will launch next year in 2027 where NASA’s Orion crewed spacecraft is scheduled to dock with both of the commercial human lunar landers being built by SpaceX and Blue Origin – under contract to NASA.

“I’m extremely confident that we are we are going to be able to launch Artemis III next year. That’s why we stepped into stacking operations,” Isaacman said to Ken Kremer.

The Artemis III SLS core stage was transported inside NASA’s Pegasus barge from NASA Michoud and arrived at the KSC Complex 39 Turn Basin Wharf at KSC Press Site on April 27th, to NASA’s Kennedy Space Center.

Enjoy our core stage arrival, offloading and Pegasus tour photos taken by Ken Kremer and Jean Wright for Space UpClose

The 900-mile journey from NASA’s Michoud Assembly Facility in New Orleans – where the core stage is manufactured – took 6 days. There are 6 crew members on board Pegasus during its maritime travels

Next day the stage was offloaded from Pegasus on a wheeled transporter and  transported into the VAB via the KSC Press site parking lot

Originally built in 1999, Pegasus transported shuttle ET’s (External Tanks) to KSC.

The ET holds the over 700,000 gallons of liquid oxygen (LOX) and liquid hydrogen (LH2) propellants that fuel the four RS-25 engines located at the base of the SLS core stage

The SLS core stage at 212 ft length remains the largest cargo the ship has ever carried.

NASA hopes to launch the crewed Artemis 3 later next year into Earth orbit to test rendezvous and docking capabilities between Orion and both of the commercial lunar landing spacecraft from SpaceX and  Blue Origin needed to land astronauts on the Moon sometime in 2028.

Inside the VAB the core stage was joined to the previously delivered boat-tail and engine section in the facility’s High Bay 2 for outfitting and vertical integration to complete the full stage.

The Artemis III core stage was moved and placed horizontally in the transfer aisle of the VAB before being lifted into High Bay 2, where it was connected to the engine section and its boat-tail, which were integrated in August 2025.

At 212 feet tall when fully assembled, the core stage houses two propellant tanks that collectively hold more than 733,000 gallons of super-chilled liquid propellant to fuel four RS-25 engines, as well as the flight computers, or avionics, that act as the brains of the rocket to control flight during ascent.

This marks the first time core stage assembly operations were taking place at NASA Kennedy.

The Artemis I & II core stages were fully assembled at Michoud before shipping to KSC

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