Carry Over from Goldin´s manned Mars plan
Hi -
You need to remember that Dan Goildin, much maligned former NASA Administratot, had planned for the RLV to be operational by next year. At that time, the existing Shuttle fleet would have been converted over to Shuttle C or variants. These improved performance solid rocket motors were planned as part of that.
They have no relevance to the Moon based astronomical facilities, which will be built with launches provided by the currently operational US EELVs.
ep