Right now I’m not so convinced that SpaceX needs a Falxon X. The Falcon 9 Heavy is large enoguh to deliver most satellites to space that the market wants.Also, two Falcon 9 Heavies can deliver 64,000 kg to LEO. That’s enoguh to deliver any single component of a Sustainable Space Development (SSD) architecture which ultimately involves bringing lunar water ice to LEO. At that point, who even needs a super heavy lift rocket for any purpose?It seems to me as though the purpose for a Falcon XX is for a single shot for manned missions beyond LEO. Again, if you can fuel an Earth Departure Stage (EDS) using an LEO fuel depot, then the rest of the stack can be lifted using Falcon 9 Heavies. However, if NASA insists on building a heavy lift vehicle, then I’d rather SpaceX & other commercial companies build it due to the proven cost-effectiveness of the COTS/CRS/(CRS)-approach. But my perspective is, Develop SSD first then we’ll realize what we do and don’t need next .