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.
Solid boosters are used with the SLS (Space Launch System) in pairs, with one on each side flanking the SLS Core stage to provide around 75% of the total thrust power used during the take-off phase of its launch. They essentially take their design from those used during the Space Shuttle program, but with added oomph to help the heavier and larger SLS out of Earth's atmosphere and into space.
NASA has also been in the process of procuring new RS-25 engines and core stages needed for missions in the Artemis program beyond the initial three, and continues to prepare for Artemis 1, with the rocket assembly process for that at the point where the boosters are nearly ready to stack. Artemis 1 is currently targeting a November 2021 timeframe for launch.