Today The New Atlantis published A Space Program for the Rest of Us - the best space policy paper I've read this year. Author Rand Simberg plans for a civil space program that is affordable and scales towards opening the high frontier for the rest of America, potentially the lead nation in a embryonic spacefaring civilization. Key passage:
The critical requirement of a reusable space system is refuelability. Consider a thought experiment from an earlier frontier. Imagine that, on the settlers’ hard trek to the western United States, there had been no vegetation along the way for the wagon-pulling horses or oxen to eat. To get across the country, each Conestoga would have to carry enough hay to feed the animals (not to mention supplies for the pioneers for months). The wagon would have been so large that the animals wouldn’t have been able to pull it. The longest distance that could be traveled would be dictated by the largest size of wagon that they could pull when it was full, and the initial speed would be very slow, picking up as the wagon grew lighter. Once the final destination was attained, the wagon and the animals would be useless without more fuel, so presumably the wagon parts would be used to build a cabin or saloon. In reality, of course, such a system would never have been affordable; had the settlers not been able to avail themselves of food and water along the way, the West would never have been settled.
Now apply that logic to space. The vast majority of the payload for heavy-lift launch vehicles is the propellant needed to send a relatively miniscule spacecraft to the Moon (or Mars or whatever destination) and back. Recall the Apollo missions’ gargantuan Saturn V rocket; the tiny capsule atop it was all that came back. And much of the propellant used by Saturn V was needed just to deliver into space the propellant that will be used for the trip back, since there were no gas stations on the Moon. The Apollo missions’ marginal costs were astonishingly high—but acceptable in the context of a race, since we did not have the time to set up the infrastructure, the needed service stations for fuel and food, along the way.