Keith's note: As you can see from these charts taken (out of context) from the 13 July 2010 NASA HEFT presentation "EELV Capacity Analysis", NASA clearly did quite a bit of comparison and contrast between various existing expendable launch vehicles - foreign and domestic - analyses that did not always include use of a SLS-class heavy launch vehicle. Indeed, one chart is titled "International Partners Have Lots of Capacity". The rest of this presentation contains procurement-sensitive information and will not be published here.
That said, it is obvious that even a year ago pragmatic thought was given to how a variety of launchers could be used for human, cargo, and other launch purposes including ways that mission profiles (DRM 4) usually associated with a HLV could be accomplished in whole or in part by the use of expendable launch vehicles. A more detailed look at what was being reviewed last year can be found at "Human Exploration Framework Team Presentation Online".
- NASA Studies Show Cheaper Alternatives to SLS, earlier post
- Using Commercial Launchers and Fuel Depots Instead of HLVs", earlier post
- The HLV Cost Information NASA Decided Not To Give To Congress, earlier post