NASA Spaceflight by Philip Sloss September 26, 2023
NASA and its advisory bodies remain concerned about the low flight rate planned for its crewed Orion spacecraft and Space Launch System (SLS) rocket, but the space agency doesn’t have enough vehicles to fly more often this decade. Hardware to launch only two more SLS vehicles is available until development of the Exploration Upper Stage (EUS) upgrade is completed, which isn’t expected to be ready to launch on Artemis IV until late 2028 at the earliest.
Following the Artemis II lunar flyby test flight planned late next year, the Artemis III Orion and crew could be the only one flying to the Moon in the following four years, but NASA still has the option to buy more Interim Cryogenic Propulsion Stages (ICPS) built by United Launch Alliance and continue flying the current Block 1 version SLS. ULA has noted that the ICPS production line will remain open until next year, when the Delta IV that ICPS is derived from retires; however, NASA once again affirmed its choice not to buy any more ICPS units in mid-September.
Not enough SLS hardware to fly annually until EUS upgrade is readyThe gap between Artemis III and Artemis IV in the Artemis manifest has increased in the last year. Artemis III will see the final launch of the initial, Block 1 version of SLS, which uses the ICPS as an in-space second stage. Artemis IV will be the debut launch of the SLS Block 1B version, which replaces ICPS with the Exploration Upper Stage, which is still in development and will also require a new mobile launcher.
In the NASA OIG report on Mobile Launcher-2 (ML-2) in June 2022, Artemis IV had a notional, planning date of August 2026, which would only be months after aspirational/notional Artemis III launch date in late 2025.
ML-2 finally started construction in the last few months, but the project is late and the OIG audit on ML-2 detailed issues that realistically would delay its completion and delivery well past 2025, possibly as far as late 2027. Development of the EUS upgrade to the SLS Block 1B vehicle must also be completed for Artemis IV and that has also seen delays in the last few years.
By the government budget request released in February, NASA’s planning date for Artemis IV had moved out to September 2028. The current Artemis manifest shows the final two Block 1 missions, Artemis II and Artemis III, flying at the end of 2024 and the end of 2025, respectively, which leaves almost three years between Artemis III and IV.
More:
https://www.nasaspaceflight.com/2023/09/lack-of-sls-rockets-limit-nasa-artemis-manifest/
