Launching Fuel from Earth

The primary drawback to using many SSTO rockets to stockpile fuel in Earth orbit is the number of flights required.

Suppose the useful load of an SSTO is 5% of its gross lift-off weight, and its mass ratio is 90%. (That's optimistic, but it demonstrates the point.) Then, to completely refuel the rocket in LEO, we would need 18 flights to carry fuel tanks to orbit, and then one more to launch the one we're going to send to the moon.

Now, using the preliminary numbers for the proposed commercial SSTO, each launch costs us about $4 million. So those 19 launches would cost $76 million. That means our cost per passenger (assuming 50 paying passengers) would be $1.52 million, which is a tad higher than the $96,000 we were shooting for.

Hence, the argument that we should develop the lunar fuels industry first, and then open a gas station in LEO. We're using lunar resources as a leveraging technology, and its a really useful lever!