Gene pool, skills pool, redundancy, etc. I can suggest a way of getting 10,000 people into Earth orbit, but not to Mars just yet. That really is a problem for future generations to solve.

As for an ARMXER being a fantasy, it's amazing how realistic the computer simulation looks.....

If it were merely 30% improvement in performance over the Shuttle, it probably wouldn't be worth investing in a completely new technology. We might as well invest in something we know, like scramjets, or SSTO, or whatever.

But the dynamics of the ARMXER Orbital Skyhook technology suggests approximately 5000-fold improvement in performance. With five ARMXERs (one tether each) orbiting it would be a 20,000-fold improvement, and with 4 tethers each would be 250,000-fold increase in mass launched into space. I strongly believe that considering the payoff, whatever technical problems exist are worth solving.