At the end of a lecture and presentation that I gave for Starfest 2012 at Bays Mountain Planetarium, I was asked for sources of information concerning practical deep space exploration options that make more budgetary and implementational sense than options that would involve either of the two proposed versions of the SLS launcher.
Next I would suggest NASA’s own groundbreaking study known as Propellant Depot Requirements Status Report. This study was released before SLS was formally named and the designs of both models of SLS were yet to be finalized, though it was already known that the final model of SLS (now known as Block II) would be Shuttle-derived and have an orbital payload capacity in excess of 100 metric tons. The points made in this study are still very relevant if the reader just considers all references to a SDV HLLV as being SLS Block II.
A group of scientists and engineers at Georgia Tech produced the latest paper, which does a direct comparison of using existing commercial launchers for deep space exploration versus using either model or both models of SLS (Block I and Block II) for that purpose. This paper, called Evolved Human Space Exploration Architecture Using Commercial Launch/Propellant Depots starkly reveals both the economic and functional disadvantages of SLS. Anyone who peruses either this study or the earlier NASA study will plainly see what a threat to American spacefaring supremacy that SLS constitutes. In fact, it closes with the conclusion that going the alternate route that does not include SLS “provides experienced and focused workforce to improve safety, operational learning for reduced costs and higher launch reliability, reduce launch costs …”
Many thanks to Clark Lindsey of New Space Watch, for making the last paper available to the public via the internet.