a Block 1B and Block 2, but cancelled these plans in February 2026, aiming to standardize on Block 1, to "reduce risk and maintain schedule stability". Block 1B was to use the Exploration Upper Stage, and Block 2 would have used new solid rocket boosters.

While SLS has the highest liftoff thrust of any rocket to ever carry humans, , SLS's payload capacity to trans-lunar injection of is only around half that of the Saturn V's