NASA has completed integration of the Space Launch System (SLS) core stage with its two solid rocket boosters for the Artemis III mission, establishing the rocket’s short-stack configuration ahead of a planned propellant-loading test.
The assembly took place inside High Bay 3 of the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida.
NASA photographs document the integration on October 25, 2026, and the agency published its official completion announcement on October 28.
The completed assembly combines the 212-foot-long core stage with the twin five-segment solid rocket boosters, which were previously stacked on the mobile launcher.
NASA will now conduct testing and checkout activities before transporting the short stack to Launch Pad 39B for a cryogenic propellant-loading demonstration.
How NASA Assembled the Artemis III Short Stack
The core stage was initially positioned horizontally inside the Vehicle Assembly Building.
Technicians used specialized lifting equipment to raise the stage into a vertical position and prepare it for installation between the two boosters.
The operation required a purpose-built lifting beam capable of handling the stage’s substantial size and mass.
The stage was moved from High Bay 2 into High Bay 3, where the solid rocket boosters had already been assembled on the mobile launcher.
Engineers carefully positioned the core stage between the boosters and completed the mechanical connections needed to form the short-stack assembly.
The boosters provide structural support for the central stage and, when the rocket is fully assembled, help carry the weight of the vehicle through the mobile launcher’s support system.
NASA’s SLS technical documentation describes how the boosters connect to the core stage through structural attachments designed to transfer forces during launch.
The completed short stack is an intermediate assembly configuration. It does not yet include the Orion crew spacecraft or the remaining hardware needed for the complete Artemis III launch vehicle.
The 212-Foot Core Stage
The SLS core stage is the central propulsion element of the rocket.
It contains two large cryogenic propellant tanks, one for liquid hydrogen and the other for liquid oxygen.
The stage also includes four RS-25 engines, propulsion feed systems, avionics, structural components, and connections to the ground launch infrastructure.
The engines are derived from the propulsion system originally developed for NASA’s Space Shuttle program.
Each RS-25 burns liquid hydrogen and liquid oxygen to generate thrust.
Together, the four engines provide sustained propulsion during the early ascent after liftoff.
The solid rocket boosters operate alongside the engines during the initial portion of flight.
NASA completed installation of all four RS-25 engines on the Artemis III core stage before the October integration operation.
The agency’s October 13 hardware update also identified remaining systems work needed to prepare the stage for assembly.
This included installation of a systems tunnel running along the core stage that carries cabling associated with launch vehicle operations.
The Twin Solid Rocket Boosters
Each Artemis III solid rocket booster consists of five motor segments, with additional structural and aerodynamic components.
The motors are manufactured by Northrop Grumman and use solid propellant.
Unlike liquid-propellant engines, solid rocket motors contain their fuel and oxidizer in a prepared mixture inside the motor casing.
Once ignited, the propellant burns and produces high-pressure gases that are expelled through the nozzle to generate thrust.
The two boosters provide more than 75% of SLS thrust at liftoff.
They operate during the initial ascent before separating from the core stage.
The booster structures also incorporate flight control equipment, avionics, separation motors, and mechanisms for steering the rocket.
NASA completed stacking the Artemis III booster motor segments and forward assemblies on September 30, 2026.
That milestone allowed technicians to proceed with preparations for mating the core stage to the boosters.
The October integration completed the central portion of the rocket assembly required for the planned ground test.
Why NASA Is Conducting a Tanking Test
NASA plans to transport the short stack to Launch Pad 39B for a test involving the loading of liquid hydrogen and liquid oxygen into the core stage.
The operation will reproduce important parts of the launch countdown without launching the rocket.
Liquid hydrogen must be maintained at approximately minus 253 degrees Celsius, and liquid oxygen at approximately minus 183 degrees Celsius.
These extremely low temperatures place substantial demands on the ground equipment, valves, seals, piping, and connections used to transfer propellant into the vehicle.
During a tanking test, engineers can examine the performance of these systems under operating conditions that closely resemble those encountered during an actual launch countdown.
The Artemis launch team will also practice the procedures and timing used to prepare the rocket for flight.
NASA has been working on updated liquid-hydrogen ground connections following leakage problems encountered during earlier Artemis launch preparations.
The propellant-loading demonstration provides an opportunity to evaluate the integrated hardware and ground systems.
The test is intended to use the core stage and boosters without Orion or the mission’s remaining upper structural elements.
This allows the agency to conduct the propellant-loading evaluation before completing the full flight vehicle.
Transporting the Rocket to Launch Pad 39B
Following the remaining tests and checkouts inside the Vehicle Assembly Building, NASA plans to move the short stack to Launch Pad 39B.
The assembly will remain attached to the mobile launcher during transportation.
NASA uses its crawler-transporter system to carry the mobile launcher and rocket assembly between the Vehicle Assembly Building and the launch pad.
The crawler moves slowly along a specially prepared roadway designed to support the substantial weight of the vehicle and launch platform.
Once the assembly reaches Pad 39B, technicians will connect the relevant ground support systems.
These include the equipment needed to supply cryogenic propellants, electrical power, data connections, and environmental support.
The launch team will then conduct the planned propellant-loading demonstration.
NASA has targeted the tanking test for late 2026 as part of its preparations for Artemis III.
The October 28 announcement confirms completion of the short-stack assembly but does not establish a revised tanking test date.
Artemis III’s Modified Launch Vehicle Configuration
Artemis III is now planned as a low-Earth-orbit demonstration mission rather than a crewed lunar landing.
The mission will test rendezvous and docking operations between Orion and commercial lunar lander spacecraft developed by Blue Origin and SpaceX.
Because Artemis III will remain in Earth orbit, NASA has revised the rocket configuration to reflect the mission’s propulsion requirements.
The vehicle will use a structural spacer instead of the Interim Cryogenic Propulsion Stage used on earlier Artemis missions.
The spacer provides the necessary structural interface between the rocket’s core stage and Orion without the upper-stage propulsion system previously required for a lunar trajectory.
The short-stack tanking test is being conducted before that additional hardware and Orion are installed.
NASA’s revised approach to Artemis III was described in its October 23 Artemis acceleration announcement.
The agency plans to use Artemis III to demonstrate the spacecraft operations required for subsequent lunar missions.
Four Astronauts Will Fly on Artemis III
NASA has assigned four astronauts to Artemis III.
Randy Bresnik, Frank Rubio, and Andre Douglas will represent NASA, and Luca Parmitano will represent the European Space Agency.
The crew will travel aboard Orion and conduct demonstrations involving the two commercial landers.
NASA plans to test docking with Blue Origin’s Blue Moon Mark 2 spacecraft and SpaceX’s Starship Human Landing System.
The mission will allow astronauts and ground teams to evaluate spacecraft interfaces, docking operations, communications, and crew procedures before future lunar landing missions.
NASA is targeting summer 2027 for Artemis III.
The agency’s longer-term schedule calls for crewed lunar landing missions beginning in 2028.
Remaining Ground Processing Milestones
With the core stage and solid rocket boosters joined, NASA’s immediate work involves completing short-stack testing and preparing the vehicle for transportation to the launch pad.
The tanking test provides data about the cryogenic propellant systems and allow launch teams to rehearse operational procedures.
After that campaign, NASA will complete the remaining integration activities required for the flight configuration.
These activities include installing the mission-specific spacer and structural adapters, integrating Orion, and conducting additional checks before launch.
The October 25 integration operation establishes that the major propulsion elements required for the Artemis III ground test have been assembled at Kennedy Space Center.
The next announced hardware milestone is the planned propellant-loading demonstration at Launch Pad 39B.
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