I think you're absolutely right, but where will that resource come from? The Asteroid belt, Phobos, Or Mars? The second question would be, who will use those resources, Mars, Earth, or both? What resources are there that we can't get from the moon? Shall we use Phobos as a staging area, fuel depot, or as a mining quarry? Does a resource objectives generate interest from commercial businesses, such that they would want to join the mission? Like space island group, Mars Society, Mars Homestead Project. Who would you restrict? I like Brian's ideal of taking and evaluation of what's out there. Give real answers about what can and can't be done reasonably. We pretty much need a heavy lift, you get stuck carrying a lot of a little packages to orbit otherwise. Whatever way it works out, I think that getting stuff off the Earth will be cheapest by using an in-line external tank of the space transportation system with either solid or liquid propellant boosters(LPB) that can later be salvaged on-orbit to build various types of space stations, ie; construction platform, orbital refuel platform, and various space stations like the wheeled design. Rick Tumlinson of the space frontier foundation is currently advocating for NASA to give commercial contracts to build and operate a shuttle C or side amount cargo carrier. The shuttle workforce should be fairly efficient at pumping out 27.5ft diameter external tanks. Each tank is comparable to 5 three-bedroom ranch style homes and can be divided up into three floors horizontally. If such a launch system could also be used by others as well, like Bigelow, then the overall cost could be reduced for all. I've also had an interest for many years on wheeled stations built from external tanks. The extended first stage tank would be carried to orbit with the LPB remaining attached. First stage is designed to carry enough fuel to make into orbit with a smaller cargo capacity. The top and bottom sections of the in-line rocket could be designed to join and have a built-in airlock in the pivot joint. The straight top section of tank would pivot around to form an angle and one of the corners to a wheeled space station. By having a station that can vary its pseudo-gravity presence that could operate under normal Earth gravity conditions to weigh down on the occupants of the station resolving some of the medical problems, while new problems are inevitably created. This technologies the only true way that humans will be able to stay in space for extended periods of time barring gravity plaiting anytime soon. This is probably a bigger vehicle than most of you were thinking of, but it could be used as a cycler stations that could be outfitted to carry a lot of people, supplies, and equipment. If multiple stations could be built then one could be left in Mars orbit, while the other is used as a cycler station. Development of this technology would absolutely change human society with multiple stations being built in Earth and Mars orbits, forming their own microcosm societies. The free half of the ship would initially start out empty fuel tank, that on later trips be outfitted. On the initial Mars flight, additional cargo could be placed into these empty tanks from additional equipment placed in orbit by additional flights. Depending on the engines, the station could even slow down into a Mars orbit and have scientists, both on the surface and on the station with spacecraft ferrying crew between the station, Phobos and the Martian surface. A space transport would need to be designed and built for space only operations with a built-in airlock and its surface landing vehicle capable of landing and taking off whole. Other platforms would need to be designed to deploy surface vehicles. The station in this case would act like a mission control for any missions until there was more of a surface or permanent space presents. Of course there's other things that would have to be developed along the way. Like on-orbit space-tugs and an optional construction platform with a large assembly arm running on a track the length of the station. Commercializing the ISS could be upgraded to move tanks around take advantage of the space station's arm. For the space station could defeat incoming radiation, it could be wrapped with a thick matrix of tubes looping running in large water storage tube wrapping around the tanks. The outermost layer would need to be asteroid resistive the high degree. The tubes of water would be frozen around the tanks with a manifold on each to give access to water supply and to allow for freeze him in the up graywater instead. Water gives the best protection for neutrons. Anyway, thanks give me some feedback Allen Crider