Almost two generations ago, a dozen men walked the moon’s surface. Soon afterward, political priorities shifted and the world's attention turned elsewhere for decades. But now, with new players joining the community of space-capable nations, the moon is again being discussed as a serious destination for future explorers. The notion this time is not to just plant a flag, but to set up a long-term manned presence on our planet’s closest neighbor.
A permanently-manned moonbase has been part of the popular imagination for well over half a century now, and has been one of the long-range goals of manned space exploration for almost as long. This article will examine both the likely character of the first moonbase and the steps needed to get there.
THE LUNAR FLEET
It still costs over ten thousand dollars per pound to put a payload into low earth orbit. Breaking out of Earth’s gravity entirely consumes even more resources and fuel, requiring very large and powerful rockets such as the Apollo program’s Saturn V. The Saturn V remains the largest space vehicle ever built, capable of sending fifty ton payloads onto a lunar-bound trajectory.
In order to return to the moon, the various space agencies involved would have to re-invest in such powerful launch vehicles once again. The heaviest rocket currently in use, Russia’s Energia rocket, is capable of inserting a 32 ton payload into a lunar transfer orbit. Not surprisingly, it is the vehicle of choice for a number of private and international interests looking to launch a new wave of probes at Earth’s natural satellite in the near future.
However, the US may not be content with relying on foreign launch vehicles for its would-be resurgence to the moon. Harrison Schmitt, one of the last astronauts on the moon and a leading advocate for its commercial development, predicted in a recent Popular Mechanics article that a modern Saturn V-style booster could be developed for about $5 billion dollars. Using improved technologies, these new, larger Saturn-like rockets would be capable of delivering 100-ton payloads to the lunar surface for a per-pound cost cheaper than the Energia.
China, with ambitious plans to land taikonauts on the moon in the next generation, is also developing a large, Energia-like rocket for just such a purpose.
The ESA, NASA, Japan, India, and China are all planning on launching new spacecraft to the moon in the next few years.
The ESA already has SMART-1, an orbital surveyor, circling the moon and mapping it. SMART-1 was meant primarily as a testbed for experimental technology, particularly its miniaturized ion rocket engine.
India is planning on launching its first lunar probe, Chandrayaan-1, in late 2007. Meant primarily as a means of pushing the limits of Indian technical capability, the Chanrayaan probe will map the moon and send back high-resolution images of its surface.
Around the same time, China will launch the first of its Chang’e series of lunar surveyor craft, named after a Chinese legend of a fairy who flew to the moon. It is also designed to produce high-resolution maps of the moon.
A year later, in late 2008, NASA will follow up with its Lunar Reconnaissance Orbiter. It is designed to scout for potential landing sites for future manned missions using, among other sensors, an advanced synthetic-aperture radar.
The launch of Japan’s Lunar-A probe has been repeatedly delayed because of technical problems and is currently under review by the country’s space agency. The Lunar-A carries instruments to monitor moonquakes, measure near-surface heat flux, and study the lunar core and interior structure.
The Japanese are also planning to launch a general mapping mission of the moon with its SELENE (SELenological and ENgineering Explorer) probe, scheduled for a 2007 launch.
There are also plans by NASA and some private interests to deploy small rovers to more closely examine areas of interest on the moon’s surface.
LOCATION, LOCATION, LOCATION
If all probes mentioned carry out their missions as planned, the Moon will be far more extensively mapped than ever before by the dawn of the next decade. Using this data, future mission planners will decide on the monumental next step: where and how to send the first manned missions back to the Moon.
NASA and other space agencies are especially interested in the polar regions, where earlier survey satellites detected the presence of water ice lurking deep in the eternal shadows of ancient craters. The presence of what may be thousands of tons of water ice could be crucial to a future manned presence on the moon. This ice could not only provide drinking water, but by separating its basic elements it would allow a moonbase to extract oxygen for breathing and hydrogen for fuel.
However, not everyone is confident the ice will be able to be harvested as a useful resource. The temperature in the perpetual dark of those craters are hundreds of degrees below zero, making the ice steel-hard and razor-sharp. This is in addition to astronauts working in hazardous super-frigid temperatures for extended periods of time, hundreds of meters down in pitch-blackness. Even using advanced autonomous vehicles may not be enough to overcome the extreme conditions in order to bring significant amounts of ice back for use by a lunar base.
Assuming the ice-gathering problem can be overcome, however, the northern lunar pole looks especially attractive to NASA. Unlike Earth, the moon has very little axial tilt, and rotates about a near-vertical axis in respect to the sun. At certain points near the northern lunar pole, particularly around the rim of Peary Crater, the sun never sets; it forever skims just above the horizon. This could greatly ease energy-gathering requirements through solar cells, and would maintain most of the landscape at a steady temperature of -50 degrees Centigrade.
Tech Level: 12
The first few manned missions back to Luna will probably closely resemble the Apollo landings in character; a handful of astronauts in small landers, a ceremonial planting of the flag, and many surveys and scientific experiments. However, it is beyond these that the true challenge lies: setting up long-term facilities on a barren, airless rock over 230,000 miles away.
The specific spot chosen will likely be a wide, level area near one or more of the previously-discovered repositories of ice. A flat area would make spacecraft landing much easier, as well as facilitate setting up solar cell arrays for energy gathering. Ideally, such an area would also be relatively free of obstructions such as large boulders, and have a minimum of lunar dust astronauts would have to contend with.
It is likely that unmanned predecessor missions will carry many supplies and equipment well ahead of the astronauts to the site previously chosen for the base. Everything the first moonbase astronauts may need will already be there waiting for them, including construction materials, tools, vehicles, batteries, and so on. The moon is close enough to allow slow but reliable teleoperations from Earth, meaning ground control could use remote-controlled maintenance drones to handle much of the preliminary construction. These construction robots could also handle such tasks as removing potential obstructions such as rocks and large amounts of lunar dust.
One proposal is to send an unmanned back-up return vehicle to the site ahead of the first manned crew, so that when the astronauts arrive they have an extra vehicle at their disposal. This would not only provide them with a means to return home should their primary vehicle run into problems, but would also give them extra living space during those first few crucial weeks they may be setting up the primary base structures.
Designers of the first moonbase will likely draw heavily on technology and techniques developed for the International Space Station (ISS) for individual systems, such as recycling, air, water, and so on. Refer to articles, on this site and others, about space stations and their systems.
The most important structure to be built will be the first surface habitat, meant to serve the astronauts’ long-range living needs outside their ship. The exact design will depend on a great many factors, including weight, cost, configuration, and a slew of others. The first habitat might be wholly constructed on Earth like a Space Station module and landed on the moon already fully assembled. The first crew would just have to warm it up, do a systems check, and move in.
The primary surface habitat might also be an inflatable structure. Such a module would be potentially lighter, less bulky, and cheaper than a wholly-constructed hard-frame module. A far cry from thin-skinned balloons, an inflatable module would have a dozen or more layers of reinforced and insulating material around a solid core of interior walls, and would be slowly inflated by attached gas canisters.
A third method for building a primary habitat is simple modular construction, like many military advance bases are made today. This would be the cheapest kind of habitat material-wise. However, this also would require a much greater human presence on the surface to construct, increasing the amount of time astronauts would have to spend on potentially hazardous EVA.
This first habitat, no matter how it is built, is usually envisioned as being a long cylinder or half-cylinder (to better fit into launch vehicles), usually no longer or wider than a modern mobile home. Its visual character is usually very similar to that of ISS modules. The modules are usually also envisioned as being covered over with thick tarps to help act as both insulation and additional radiation shielding.
After the first shelter is operational, astronauts would need to establish a power source. Modular solar-cell arrays would be set up on the surface to take advantage of the unfiltered sunlight the moon receives. These would be deployed in large, tightly-gridded "farms" close to the base. The lunar personnel would have to set up not only enough cells to power the base, but also enough to charge the batteries they will need to run their systems during the lunar night, should it be necessary.
Another option would be to bring along a small, fully-operational nuclear reactor to the moonbase, and use the solar cells as a supplementary energy source. Reactors small and mobile enough to make the trip to the moon were are easy enough to engineer with today’s technology. The main obstacle to supplying a moonbase with one would be political. Even though there is no ecology on the moon to contaminate, the reactor would still have to be launched from Earth, and rockets have a nasty habit of very occasionally exploding upon launch. It was concern over such an explosion spreading radioactive material that led to legal controversy surrounding the launches of the Gallileo and Cassini interplanetary probes, which used nuclear material for power and heat. A full-scale nuclear reactor aboard such a high-profile launch would likely draw even more controversy.
The third major necessity on the lunar surface is a storm shelter. The moon is outside both Earth’s atmosphere and magnetic field, leaving its surface completely exposed to the harsh energies of space. During peak solar activity, astronauts may be exposed to potentially hazardous levels of radiation, even in their primary habitat or return vehicle. They will need a place where they can retreat to in order to ride out these intense solar storms.
The simplest solution is to just dig one; a few meters of solid rock makes a very effective shield. Like Kansas residents a quarter million miles away, moonbase personnel may find themselves huddling occasionally in a storm cellar. Excavation machinery could create the shelter, which would be lined with air-and temperature-tight walls and pressurized. Ideally, it would be attached to the main habitat for quick access. It would even be possible for autonomous construction machines to excavate a shelter ahead of time, and have the astronauts construct or place their main habitat right over it.
An alternate method is to build a surface storm bunker, a heavily-reinforced structure covered over with a few meters of lunar rock or bags of moondust.
Auxiliary structures would be needed to be added afterward to make the base fully functional as an outpost. Cleared landing field for spacecraft. Storage tanks for water and rocket fuel. Communication dishes to facilitate contact with Earth and lunar-orbit satellites. Maintenance facilities for tools and parts. And so on. These will be discussed in a separate article.
Houston, we have a moonbase.
"Mining the Moon" by Harrison H. Schmitt, Popular Mechanics, October 2004
On the Internet:
http://www.space.com/businesstechnology/technology/moonbase_biz_021002-1.htmlhttp://www.space.com/scienceastronomy/050413_moon_perfect.html http://www.newscientist.com/article.ns?id=dn7263 http://www.lpi.usra.edu/expmoon/future/future.html http://vesuvius.jsc.nasa.gov/er/seh/gotomoon.html