I have been advocating modular on this forum for years. The only difference I see in this thread being it is addressing one section of what I have been talking about rather than the entire problem. <br /><br />One simple module design, that can be mass produced and combined with other modules, think the Lego system. As an example the major portion of every vehicle is propellant tanks, why do they all have to be different? The basic design of a cargo or crew module can also be the same module, it depends on how you outfit or load it what it's role is, and a module could fit many roles over a life-time. <br /><br />I would think consolidating launched modules at a LEO station, then moving them to LMO, using LEO based transfer vehicles, or Tugs, would only make sense. Especially from a cost standpoint. <br /><br />The same vehicle could easily make multiple roundtrips, refueling at the LEO station using propellant brought up on multiple launchers. The only other component needed would be a Lunar Landing vehicle, which doesn't have to be that big of a problem, built using a modular system and Tug engines, it could also be used as a Mars Lander by adding a few parts. The only real difference between being in LEO, LMO or enroute between the two is the propellant needed, the basic environment is the same. <br /><br />The modular design can be extended further, if a standard module can be a propellant tank, cargo container, crew module, LEO station element ect., it could be a Lunar Base module, a Mars transit vehicle component or a Mars Base element just as easily. <br /><br />A bare, empty, module could be transformed into any number of Elements and combined with other Elements in any number of ways. A Launcher with a fly-back first stage and a second stage that continues into orbit, ala Delta. Cargo and propellant modules stay in LEO for future uses and a simple return vehicle being used to return people and cargo. Something like the Gemini3 being discussed in the Business for <div class="Discussion_UserSignature"> </div>