Brett do I hear this correct? Are you willing to go your self on a one way mission to Mars? Yah we could get there but aint no coming back yet. Unless there is something I have missed.
Well, yes, I would go one-way (and volunteered for a potential one-way right after the Challenger - as did every single *real* astronaut and everyone on the program who might be qualified; that was actually a plan for about a month or two, to launch a few critical payloads regardless of the risk).
But the technological basis for going, staying for the required time (on the order of a year) and coming back is well in hand for *a long* time now. It would be a massive and every expensive effort but Apollo-era capabilities and mild extrapolations would have been more than adequate. For example, Skylab would have made the *perfect* spacecraft for the travel to and from Mars and could easily carry sufficient supplies. You would need a HUGE pair of external boost and brake stages to boost it out of Earth orbit, stop it at Mars, and then send it back. But big is all that would be required, nothing particularly sophisticated. So well within our capabilities.
The lander is pretty high-zoot but you have some advantage that you can use aerobraking and parachutes so it's not inordinately worse than landing on the moon. The ascent stage would be huge, of course.
Von Braun had it pretty much worked out by the time he got moved out of Apollo, and it was a fun bit of work for us in junior high science class to determine the required propellant quantities. For the braking and Mars escape insertion that was a lot of propellant since you had to use hypergolics. If you could convince yourself that you could insulate the tanks long enough to use LOX/RP1 for at least the braking, that would tremendously reduce the size of the Mars boost stage.
And this is for a "giant Apollo" EOR-MOR mission without aerobraking into orbit. If you could develop some of the trickier in-situ propellant, oxygen, and water generation, then the entire thing shrinks dramatically, as does some of the risk. The beauty of that is that if you screwed it up the first time, you could keep trying until you got something that worked with no risk of people. That's probably just a matter of research, not advanced technology.
Note that if we went back to the moon, we would almost certainly use EOR-MOR now, too. They thought it was too complicated at the time but they also had never done a rendezvous in space when they decided. If you just wanted to repeat Apollo you could do it with much smaller boosters because you would assemble the stack in orbit. We could have done it with three Titan 4 or Delta 4 heavy launches - one for the LM, one for the S-IVb and one for the CSM (probably in that order) and maybe with three Atlas 552 launches although I haven't done the math. I think the Saturn 1b was just a bit too small for three launches (because the fully-fueled CSM was too heavy - no problem for the LM).
Brett