[Cincinatus]

The problem with using existing EELVs, like Delta-IV, is that you still have to launch 150 mT to LEO for a manned lunar mission. That means about 10 Delta-IV heavys, just to get the stuff into space. Then you have to assemble your vehicle in orbit.

One thing that Station has taught us that while it's possible to do on-orbit assembly, it's not desirable. It increases risk and cost. It creates numerous problems of its own. The real lesson of ISS is to minimize on-orbit assembly. Developing a real Heavy Lift vehicle does just that.

[chimera]

One thing that Station has taught us that while it's possible to do on-orbit assembly, it's not desirable. It increases risk and cost. It creates numerous problems of its own. The real lesson of ISS is to minimize on-orbit assembly. Developing a real Heavy Lift vehicle does just that.

I have read that this very point was one of two that brought Von Braun around to the LOR concept for Apollo, having been previously an apostle of EOR. The other being the massive size of the landing vehicle that would be wrought by going the EOR route. All very valid points. The challenges of assembly in zero gravity vacuum are quite daunting compared with tinkering things together in a terrestrial environment. That's not to say it can't be done, because we and others have done it. It's just lot more bother.