Re: Nice idea
NASA needs to focus its budget on the technologies that aren't being developed by the private space industry and get the basis of true interplanetary vehicles worked out; the main theme has to be low-thrust, long-duration engines with high specific impulse.
Low thrust/high impulse engines are certainly useful, but it's worth looking at them in conjunction with lunar-sourced resources, too. The whole issue of interplanetary travel gets a lot easier when most of your mass, like propellants, doesn't come from Earth.
A more-certain alternative to lunar hydrogen is lunar oxygen and lunar sulfur. The resulting brimstone rocket has a low impulse - about 250 - but that's sufficient to escape the moon and operate a transport network between Earth, the moon, and LaGrange points, where ion engined spacecraft might park.
Luna's resources have an advantage over the asteroids and Mars in the short travel time, even though velocity requirements are similar. Everything's easier in a pioneering in situ resource facility when you're 3 days (or less) away. Whenever something breaks or doesn't work as planned - and vacuum mining operations will get something wrong initially - the replacement can be delivered more quickly. Three days is also short enough for an evacuation of an ill or injured astronaut.
Which brings up another role for the NASA beyond engines: building infrastructure. Governments have a track record of building infrastructure projects that private industry won't invest in. Sometimes those projects turn out to be white elephants, sometimes they're grossly over budget and off schedule, but they wouldn't be built by entirely private industry and funding. A lunar mining operation is a candidate.
Biting the hand that feeds IT
