If you use a Shuttle based first stage the entire second stage could be used to reach an orbit and thrusters and maneuvering engines on the stage could be used to reach a LEO Station, or transfer point. Detach the CEV, or cargo container, use the CEV to return people and cargo to the surface and the cargo containers as elements for future missions. You have perfectly good LH and LOX tanks as well as proven re-usable engines and Cargo Containers at a central location where they could be used for future missions beyond orbit. This, of course, assumes they are all the same basic Module. <br /><br />Using a Shuttle based first stage would also allow more robust Modules that could have multi-purpose uses, if every Module is man rated it would be a simple matter to outfit it as needed in orbit with equipment brought up in other Modules.<br /><br />Using the Moon as an example a three Module Vehicle, with cargo Modules attached could go from LEO to LLO and back on a scheduled basis. Once in LLO a landing vehicle could bring up cargo Modules and passengers and take down cargo Modules and passengers. It would be a lot more cost effective to base them on the Moon than bringing them from LEO on every mission.<br /><br />Think about it, once you are in LEO nowhere we could reasonably think of going needs anything beyond a simple cylinder, or Module. Attach them to one another like legos and you can build any configuration you need. <div class="Discussion_UserSignature"> </div>