https://techcrunch.com/2020/06/30/nasa-sets-path-for-up-to-six-more-artemis-moon-exploration-missions-with-sls-booster-order/

NASA has laid the groundwork for an order of up to six additional SLS solid core booster rockets, from supplier Northrop Grumman, the agency announced this week. The six additional boosters would join the existing three that NASA previously locked in for use on Artemis 1, Artemis 2 and Artemis 3, which includes the targeted 2024 mission that will bring the next American man and the first American woman to the lunar surface.

While this is essentially a long-lead declaration of intent to help partner Northrop Grumman ensure its supply pipeline can supply the additional boosters in a timeline needed by NASA, rather than an actual order for the boosters themselves, it’s still a big step with a potential total contract value of $49.5 million, with initial funding unlocked now. The schedule currently calls for those additional boosters to be delivered sometime before December 31, 2030, to provide some kind of idea about when Artemis missions 4-9 might potentially actually fly.