This presentation "Propellant Depot Requirements Study - Status Report - HAT Technical Interchange Meeting - July 21, 2011" is a distilled version of a study buried deep inside of NASA. The study compared and contrasted an SLS/SEP architecture with one based on propellant depots for human lunar and asteroid missions. Not only was the fuel depot mission architecture shown to be less expensive, fitting within expected budgets, it also gets humans beyond low Earth orbit a decade before the SLS architecture could.
Moreover, supposed constraints on the availability of commercial launch alternatives often mentioned by SLS proponents, was debunked. In addition, clear integration and performance advantages to the use of commercial launchers Vs SLS was repeatedly touted as being desirable: "breaking costs into smaller, less-monolithic amounts allows great flexibility in meeting smaller and changing budget profiles."
- Using Commercial Launchers and Fuel Depots Instead of HLVs" (March 2011), earlier post
- The HLV Cost Information NASA Decided Not To Give To Congress (January 2011), earlier post
- Discuss this post at the new SpaceRef Forum