perfidy

The first three parts of this series are here, here and here.

In the first post, I discussed how we could quickly and relatively cheaply develop the means to launch people and large cargos into orbit. That is the necessary precursor to any significant endeavor in space. While the methods I outlined would reduce costs to orbit, they would not make them exactly cheap. But they would give us a ladder while others could work on building an escalator. The second post discusses, in broad outline, one idea for developing the life support technology that the Mars mission would require. The third post talks about propulsion options and precursor missions to Near Earth Asteroids.

Getting to the Moon

President Bush mentioned a return to the moon as a primary goal. This is one of the few things he got right. A permanent presence on the moon will allow us to conduct research and development that will directly aid a future Mars expedition. The utility of a lunar research outpost falls into two general categories:

• Developing technology and skills for the exploration of a hostile environment.
• Research into the production of materials and fuel that could be used in a Mars mission.

Before we discuss how a lunar base will be useful to us, let’s discuss how we might get there. In the first post, I mentioned the development of a variant of the Orbital Space Plane that could be used as an Earth/Moon shuttle. Unlike a standard OSP, this model would be wingless – saving mass by eliminating wings that will never be needed. It will be a small pressurized cabin, with life support for several crew for perhaps a week. By adding a service module along the lines of that used by the old Apollo capsules, we can extend the life support duration by a couple weeks, and also add a rocket motor that will give our shuttle the ability to leave Earth orbit and travel to Lunar orbit.
Back with Apollo, we had to launch everything needed for the mission all in go. Since there is no need for the massive thrust necessary to leave the earth’s surface, a much smaller rocket will allow us to move crew and cargo back and forth between Earth and Lunar orbit. Since we now have an orbiting space station, we no longer have to worry about getting everything we need into orbit all at once. Empty Shuttle-C fuel tanks can be used as refueling depots to top off the tanks of the inter-orbit shuttles. Cargo and crew will reach orbit on OSPs and conventional disposable rockets. All of these will be assembled together at the ISS, and depart for Lunar orbit.

Once we reach Lunar orbit, we have the problem of getting to the surface. To establish a Lunar base we need to get habitat modules, crew and supplies down to the moon. In keeping with the idea that specialized vehicles are better than general purpose ones (as long as you have the lift capacity that frees you from the necessity of doing everything in one launch) we can develop one or two more vehicles. But to save on design effort, we should make them modular, so that we can get the most use out of our design dollar. We’ve already adapted the OSP for a crew and small cargo shuttle. The immense cargo payload of the Shuttle-C will allow us to lift something bigger into orbit – something more on the lines of a truck rather than a taxi. This vehicle would have a rocket and fuel tanks at the back, an open framework for cargo in the middle, and a crew module at the front. The rocket would be powerful enough to land the vehicle on the lunar surface, and be equipped with landing gear and a crane.

The cargo shuttle could carry a standardized habitat module and land it wherever we intend on setting up a base. Once on the moon, the crane would lower the hab to the ground where it could be linked to other modules, forming a small outpost. Once free of the habitat module, the now empty shuttle would begin service as a shuttle between the lunar surface and lunar orbit. Subsequent moon bound cargos could even be automated – launched from Earth on a Shuttle-C, and boosted toward the moon by a smaller rocket. Once in Lunar orbit, the cargo shuttle could dock, load up the cargo and return to the lunar base. Crew transfers would also be done in lunar orbit. (In time, it might be worth the expense to deploy a small lunar orbiting space station – something much smaller than the ISS – basically a habitat module, a docking port and a solar array. This would simplify the process of cargo and crew transshipment, and give a refuge for emergencies in Lunar Orbit.)

For the first few years, there might be only one or two cargo shuttles, both likely in use on and around the moon. (The cargo shuttles would also be the best means for long range transportation on the moon.) Three or four of the OSP-derived interorbit crew shuttles would meet the needs of transporting crew between different locations in Earth orbit; and to lunar orbit. But as time goes by, we could slowly add more of each of these vehicles, steadily increasing our space transportation infrastructure as our presence in space expands. At no point is there a need for large, single expenditures. There is no reason why a simple OSP – either the space variant or the regular earth landing style – should cost more than a single jet fighter; and the cargo shuttle should not be that much more.

As we build this infrastructure, we can create a lunar base and keep it staffed and supplied. The lunar base at the start would be one or two habitat modules approximately the size and shape of the ones making up the ISS, and similar in construction. Once on the moon, a lunar bulldozer would cover them with soil to protect the inhabitants from solar radiation. As needs require, more habitat modules can be launched and integrated into the base. From this small but safe outpost, the astronauts could begin the research that will allow us to successfully explore Mars.

What to do on the Moon

What research will they be doing? As I mentioned above, there are two main avenues: exploration technology and skills, and materials and fuel. First, exploration. Research has already been started on the construction of Mars rovers – and prototype vehicles will be tested in desolate areas like Canada, the Antarctic and Detroit. But there can be no better place to test than the moon, which has the dual advantages of being in some respects a harsher environment than Mars and yet is close enough to allow for the rescue of our astronauts in case of accident. As we develop rovers, models for Mars habitats, new space suits, Mars rated exploration gear and so on, we will ship them to the moon. There, astronauts will use these vehicles to explore the vicinity of the lunar base and gain practical skills in exploring a hostile environment. These skills will be necessary when we get to Mars.

As far as materials go, many have proposed that we could mine for minerals on the moon, and use those materials in the construction of our Mars bound spaceship. The advantage of using lunar materials for deep space activities is that they only have to be launched out of a gravity well one-sixth as deep as Earth’s, with the cost in fuel proportionally lower. Aluminum, silicon and oxygen are the major components of the lunar regolith, or soil. Using relatively simple techniques, the loose soil of the moon could be baked to remove the oxygen, and smelted for aluminum and other elements. It is conceivable that lunar aluminum could be used for structural components for a Mars mission, but on the whole I think this is unlikely in the timeframe we’re talking about here - though in future decades, there is little doubt that lunar building materials will play an important role in our expansion through the solar system.

The first usable export from the moon will likely be oxygen, and it is possible that some lunar oxygen might find it’s way into a Mars mission. The major problem is that even with the smaller gravity well, the transportation infrastructure would not be up to bulk shipment of oxygen for use as fuel or for life support. The small number of landers will be used to deliver crew and materials to the lunar surface, and deadheading the landers back to orbit will save precious fuel. If lunar oxygen was being produced, the quantities in the early stages would be small. These would be small prototype facilities, designed to learn how to best use the moon’s resources, and not geared toward mass production.

There is one exception to this general forecast – if large quantities of ice were discovered at the lunar poles, hidden from the sun at the bottoms of craters that have not seen daylight in billions of years. This would present a wonderful opportunity. With a small amount of electricity – easily available on the moon for two weeks at a time – water ice could be directly converted into rocket fuel. (Of course, the water can also be used for life support – but in much smaller quantities.) Lunar landers could refuel at the moon, saving the cost of shipping fuel from Earth, and load their cargo bays with fuel for use elsewhere. One of the worst logistical bottlenecks in space development is getting sufficient supplies of fuel into orbit, because for every pound of fuel you end up with in orbit, you have to burn ten times as much to get it into orbit. Then, to get a store of fuel to the moon, you have to burn more fuel to leave earth orbit, and more again to get down to the lunar surface. Finding a convenient source of fuel on the moon would greatly ameliorate that bottleneck, and reduce the cost of any endeavor we undertake in Earth orbit or beyond.

There are of course other reasons to go to the moon. If we established a presence on Mars, we could use that foothold to pursue several scientific endeavors. Selenology, or lunar geology would keep many planetologists busy, and teach us much about the origins of the solar system. The lunar farside would be an ideal place to look into the heavens. A farside observatory would be shielded from Earth by the entire bulk of the moon, have no interference from atmosphere, have a low gravity to make large mirrors easier to construct and install, a stable base free of the problems of orientation that had to be solved on Hubble, and (given a regular human presence) easier to keep in good working order. Space several of these around the edge of the farside, and you could use interferometry to get resolution far in excess of anything we’ve done so far. These scientific projects and others would be made possible by a human presence on the moon.