“Our boosters are ready to launch the first flight of the Space Launch System on the Artemis I mission, and we are making great progress producing boosters for the Artemis II, III, and IV missions. Upgrading the booster’s performance ensures we can improve SLS’s ability to send astronauts and cargo to the Moon as well as making our processes more efficient.”
Source: Bruce Tiller, NASA's SLS booster manager, via comments made as NASA awarded the Booster Production and Operations Contract to Northrop Grumman for the agency's upcoming Space Launch System rockets. The launch system will be the primary system for use in the first 3 Artemis missions, with likely inclusion for the 4th.