Why do we have to send the whole ascent vehicle in advance? Why not just send the fuel tanks and some fuel making equipment, then use the cabin, life support, maybe even the rocket motors etc. from the descent vehicle to finish the craft?
Going even further, if a combined descent/ascent vehicle could bring down empty fuel tanks, the fuel making equipment could stay on mars and make fuel to supply the next mission.
Going even further, if a combined descent/ascent vehicle could bring down empty fuel tanks, the fuel making equipment could stay on mars and make fuel to supply the next mission.