Titan, remember Titan and the excitement America once felt over it? Titan is the only moon/natural satellite known to have a dense atmosphere similar to Earth. While the similarities don’t end there, it would still present some challenges but also offer some solutions that the other potential outposts do not have. With a distance from Earth that ranges from 1,200,217,664 km to 1,666,681,075 km depending on where Titan is in its orbit, Titan is certainly not a non-stop flight. With Mars only 56,000,000 km from Earth it would be a good resting point for what would be an incredibly long road. Now consider taking off from an outpost on the moon. It would mean that less propellant would be required for a space ship given that the moon has an escape velocity of 1.4 km/s whereas from Earth it is 11.2 km/s. (Simply put the Escape Velocity is the speed needed to break free of a gravitational field.) Of course there would still need to be fuel brought along for the trip; Unless it were to be provided along the way.
Figure Mars has an escape velocity of 5.0 km/s and then when one gets to Titan a return is likely required so enough fuel to handle 2.639 km/s. Although each of those rates is lower than Earth’s, they still would need to be considered. Think of each of the stops as a rest area on the Interstate. Fuel could be manufactured ‘locally’ and picked up at each stop.
So, the trip is begun at the Moon. The outpost there has been sustaining itself with local resources thanks to RASSOR (a robot being tested by NASA now.) Oxygen was extracted from the soil, water was obtained from the soil and more from moon ice, and yet another processing of the moon dust for the fuel. On to Mars -Mars is a regular cornucopia of raw materials. It is rich in carbon, nitrogen, hydrogen and oxygen, and all in biologically readily accessible forms such as CO2 gas, nitrogen gas, and water ice and permafrost. As a matter of fact the abundance of raw materials on Mars is what makes having an outpost there so exciting. It is probably the best location out of all the planets, Earth excluded of course.
That leaves Titan. Titan claims dozens of giant Lakes, most likely more as Saturn’s orange moon has not been mapped in entirety as yet. These lakes are just a portion of the liquid hydrocarbons found on Titan and can easily be compared to Earths once abundant oil and natural gas reserves.
While there are many other things to consider, one by one NASA has been looking into them and so has private industry. Between them several ideas will take hold. One consideration is to provide a break between Mars & Titan, an outpost that is robotic, not bound to any planet or moon, but offers the capability of constantly expanding our reach further in space; A cosmic leap frog if you will!