Cowboy R and the Question of Destination

I'm listening to Planetary Radio, the podcast of the Planetary Society. It's an episode from a few weeks ago, recorded after the announcement of the discovery of water on Luna. Bill Nigh, in addition to being the widely heralded "Science Guy," is also the vice-president of the Planetary Society, and he contributed an opinion piece to the show, about Luna being a dead end for science; that the "real action" would be on Mars.

This caught my attention for a couple of reasons. First, the Augustine Commission Report was recently published, which suggested not returning to Luna, and abandoning the Ares rocket development because of budget restrictions. As it happens, I agree with the suggestion that we should make use of commercially available space lift, but the rest of it, I have issues with.

And to explain why, I'm going to have to use some numbers. Those of you who are math-phobic, avert your eyes for a paragraph or so. I believe it was Robert Heinlein who first said that, once you reach geosynchronous transfer orbit (GTO) you're halfway to anywhere in the solar system. And it's true, in terms of energy expended. In space, energy is expended to speed up and slow down, but it's not necessary to continue expending energy to continue moving. In the vacuum of space, there's nothing to cause friction which would cause you to slow down (although, ask me about the Pioneer Anomaly, some time). This expenditure in energy is measured in terms of change of velocity, or ΔV.

To go from the Earth's surface to low Earth orbit (LEO) you need a ΔV of about 9,300-10,000 meters per second. To get from LEO to Luna? 5,700 meters per second, or somewhere on the order of 60%. The same holds true for the return from Luna to LEO.

Now, here's the interesting thing. To go from the surface of Earth to the Surface of Mars, you're looking at a ΔV in the neighborhood of 20,000 meters per second... which is a lot. However, to go from Lunar surface to Martian surface? Approximately 9,000 meters per second. It takes less than half the energy.

Obviously, people are going to have to come all the way from Earth. But all the stuff they'll need on Mars (or any other area of exploration) doesn't have to. Regolith, the Lunar soil, contains iron, aluminum, titanium, and many other things. But the best thing it contains is hydroxyl, which is a molecule formed of one hydrogen and one oxygen atom. With a process such as vapor-phase pyresis, these materials could be extracted.

Ultimately, unfortunately, I do think that NASA is going to abandon manned spaceflight. It's expensive, it's dangerous, and NASA is a government agency, which shies away from both of those things. If we're going to see human exploration of the solar system, it's going to rely on private industry, which will have to pay for its own weight at every step. Whether that means groups such as Bigelow Aerospace that want to put hotels on-orbit, or foundations such as The Artemis Society which leverage the wealth of large groups of individuals, remains to be seen.

Unless the Chinese show that they're making a serious go of reaching Luna. Then all bets are off... but that's a subject for another day.