Mobile Launcher 2 (ML-2), the launch tower and platform to be used by the Block 1B variant of the Space Launch System (SLS), recently had its tenth and final tower module stacked on July 2. Module 10 will support the Orion crew access arm and related systems, and its installation brings the ML-2 tower’s height to 106 m. The overall ML-2 structure will be over 122 m tall and mass over 5,600,000 kg.
In other good news for the SLS and Artemis programs, Congress recently approved additional funding to preserve the Artemis IV and V missions, thereby maintaining SLS Block 1B and the rationale for using ML-2, which is only compatible with SLS vehicles from Block 1B forward.
NASA's Mobile Launcher 2 (ML-2), designed and built to support SLS Block 1B, completed stacking earlier this morning with its 10th and final module being lifted into place.
Now at its full height, work will continue on ML-2's internals and umbilical structures.
— Max Evans (@_mgde_) July 2, 2025
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Although Module 10’s installation on ML-2 is a significant achievement, the structure is far from complete. ML-2 will host 11 umbilicals and 50 subsystems, and structures like the crew access arm still need to be added. Some umbilicals and systems will support the Block 1B’s new Exploration Upper Stage (EUS), replacing the shorter and narrower Delta IV-based Interim Cryogenic Propulsion Stage (ICPS) used for the first three Artemis missions.
The current work-to-date for prime contractor Bechtel to deliver ML-2 to NASA is November 2026, although NASA’s Office of the Inspector General (OIG) reported that it does not expect ML-2 to be delivered until August 2027. If Bechtel manages to deliver ML-2 to NASA by November 2026, the company will be eligible for a milestone fee payment that would not be available if it were delivered afterward.
If ML-2 is delivered in November 2026, its preparations could conflict with preparations for Artemis III’s launch. ML-2 and the Artemis III stack on ML-1 would need to utilize the same facilities for testing and launch activities, specifically the Vehicle Assembly Building (VAB) and Launch Complex 39B (LC-39B) at the Kennedy Space Center. The earlier baseline for completion was September 2027.
ML-2 construction was started in 2020, with an initial completion date of 2023. However, the COVID-19 pandemic and other issues led to several delays. Even after ML-2 is delivered to NASA, additional work will be needed to prepare the platform for operational launches. OIG’s August 2024 report also projects that ML-2 will not be ready for launches until the spring of 2029.
Rendering of a Block 1B SLS mounted on ML-2 at LC-39B. (Credit: NASA)
Artemis IV, the first mission to use ML-2 and SLS’s Block 1B variant, is currently scheduled to fly in September 2028. Artemis IV will use the Block 1B’s added capability over the original Block 1 SLS to deliver the I-Hab habitation module to the Gateway station in lunar orbit. The four astronauts on that mission will also conduct the program’s second crewed landing on the lunar surface using SpaceX’s Starship-based Human Landing System (HLS) lander.
SLS Block 1B replaces the original SLS Block 1 ICPS upper stage with the EUS, featuring four RL-10 engines, and a wider fairing for carrying heavy cargo. The original Block 1 core and five-segment solid rocket boosters will still be used; however, the EUS will make the Block 1B taller, rendering it incompatible with the Mobile Launcher 1 (ML-1) used for the first three Artemis missions.
Following Artemis IV is Artemis V — a human lunar landing mission, using Blue Origin’s HLS lunar lander, that also will deliver the European Space Agency’s (ESA) ESPRIT refueling and communications module, a Canadian robotic arm, and NASA’s Lunar Terrain Vehicle rover to Gateway. Both missions were funded in the Trump Administration’s “big beautiful bill” supplemental appropriation that passed both houses of Congress this month before being signed into law by the President.
ML-2 next to a Shuttle-era mobile launch platform and the former orbiter processing facility, now repurposed for Boeing Starliner. (Credit: Joe B for NSF)
However, the White House Office of Management and Budget (OMB), which had originally marked Artemis IV and V for cancellation, states that it has the authority to decide how to spend the funds that Congress appropriates. There is currently a “news blackout” from NASA regarding Artemis IV and V milestones as a result.
The OMB is also working on significant personnel cuts at NASA, which may impact Artemis going forward. 2,000 senior managers at NASA may lose their jobs before the end of the year, and the White House is considering withholding funds from NASA for its payroll at year’s end as well.
Other challenges to the Artemis IV and V schedules include possible delays to the Starship-based HLS lander as a result of the recent explosion of Ship 36 at Starbase’s Massey’s test site. There are also ongoing post-pandemic-related supply chain issues affecting core stage production for both missions.
The completed Orion spacecraft for Artemis II. (Credit: Lockheed Martin)
The Artemis II mission, the first crewed flight to the Moon since December 1972, is still being processed at the Kennedy Space Center. Exploration Ground Systems is loading commodities aboard Orion in the Multi-Payload Processing Facility, and loading for a number of these commodities is complete.
Additional commodity loading will be performed in the VAB before the vehicle is rolled out to the pad for launch. Artemis II stacking is scheduled for this fall, with the vehicle expected to be ready for rollout by the end of this year. The Artemis II launch is currently scheduled for no earlier than February 2026.
In other Artemis news, Axiom Space recently tested its lunar spacesuit in pool facilities at NASA’s Johnson Space Center, and a human-in-the-loop test in a vacuum chamber is scheduled for early 2026. This test must be completed before the critical design review for the suit is finished, which is another item on the critical path for Artemis lunar landings.
A roll-out solar array for the Gateway PPE module after successfully being unfurled. (Credit: Redwire Space)
Work is also underway on the Gateway’s first two elements: the Power and Propulsion Element (PPE) module and the Habitation And Logistics Outpost (HALO) module. Redwire Space recently conducted a rollout test of one of the two large solar arrays for the PPE module.
The HALO module is now at the Northrop Grumman facility in Gilbert, Arizona, and the work-to-date for delivery to Florida is October 2026, while the PPE module’s work-to-date for delivery is November 2026. The PPE and HALO modules are scheduled to launch together on a Falcon Heavy in 2027.
(Lead image: ML-2 and the VAB at NASA’s Kennedy Space Center in Florida. Credit: Max Evans for NSF)
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