Almost forgotten in the more than forty years since we set foot on the Moon is the fact that NASA then had an aggressive plan for lunar exploration that would have culminated in a Moon base by 1980. Over the course of six Apollo landings, the time spent on the surface was extended from one to three days, the space suits were upgraded to allow moon walks of up to seven hours, and the electric-powered rover was added to the mix. In 1968, as NASA prepared for its first piloted Apollo flight, it formed a working group to study the idea of a lunar station. After three exploratory missions to different landing sites, NASA would have sent six or more missions to a single site as preparation for a permanent base. The working group began its report by declaring that a twelve-astronaut International Scientific Lunar Observatory should be a major goal for the agency. The working group's recommended option was to develop new hardware to form the nucleus of a future base. A new Lunar Payload Module with a descent stage but no ascent stage would carry 7,000 pounds to the surface. Its heaviest item of cargo would be a one-ton shelter capable of housing two people for two weeks. It would also deposit two snazzy personal jet packs for ranging over the surface and a rover or Moon buggy that could be driven by an astronaut or by flight controllers in Houston. The payload would also have included a solar furnace to test the extraction of useful ingredients from the soil, a one-foot telescope, a bioscience package, and various pieces of lab equipment. NASA's advisory group estimated that doing the groundwork for a lunar base would add a billion dollars to the projected cost of the Apollo program.
Concept art from NASA showing astronauts entering a lunar outpost. Click here for original source URL
It was a great idea but it ran into the buzz saw of political reality. NASA's budget peaked in 1965, during the white heat of development for the Moon landings, at $5.25 billion, or 5 percent of the federal budget. President Lyndon Johnson was a staunch NASA supporter, but the cost of the Vietnam War soared to $25 billion in 1967 and Congress was looking to cut costs. After the euphoria of Neil Armstrong's historic step, public interest waned and NASA's budget went into sharp reverse.
In 2009, the Center for Strategic and International Studies (CSIS) produced an estimate of the cost of a lunar base. They assume that a heavy-lift rocket will exist, and since at least three countries are likely to have such a capability, it's a fairly safe assumption. They project development costs of $35 billion, which is much cheaper than the $110 billion price of the ISS and, if spread over a decade, is no more than the costs of flying the Space Shuttle. Base operating costs are estimated at $7.4 billion per year. Half of the operating costs come from assuming that no local resources would be available, so four tons of supplies per person per year would have to be shipped from the Earth to the Moon. Basic requirements per day per astronaut (assuming water is efficiently recycled) would be 2.5 liters (or 2.5 kg) of water for drinking and adding to food, 0.8 kg of oxygen, and 1.8 kg of dried food. The other central requirement is energy in the form of solar power.
Clearly, a lunar base would be more attainable if it could be as self-sufficient as possible. The Moon was always thought of as a sterile, arid, meteor-blasted rock, so there was much excitement when orbiters sent back evidence of water in the mid 1990s. In 2010, an Indian satellite found ice in the permanently shadowed regions of craters near the Moon's North Pole. This led to research showing that the Moon contains 600 million tons of ice in nearly pure sheets several meters thick. The other key ingredient for a lunar base is oxygen to breathe. The lunar soil or regolith is 40 to 45 percent oxygen by mass; it's fairly simple chemistry to heat it to 2500 Kelvin using solar power and unlock it from minerals to generate 100 grams of breathable oxygen for every kilogram of soil. Water could also be split into oxygen and hydrogen, the main components of rocket fuel. Even the material for a habitat could be created locally. Lunar soil is a unique blend of silica and iron-bearing minerals that can be fused into a glasslike solid using microwaves. Fairly simple technology can turn the dirt into hard ceramic bricks. The European Space Agency is developing a 3-D printer that can create wall blocks at three meters per hour, fast enough to build a whole habitat in a week.
The cost of a Moon base shrinks dramatically if air, water, and building materials can be generated locally. All of the technologies needed to do it have been demonstrated in the lab. There's no projection or wishful thinking of the kind invoked for space elevators, for example. Location is as crucial when buying a home as when planning a Moon base. The best spots are high mountains on the rims of large craters near the poles. They would be close to abundant water ice but high enough to be peaks of eternal light, always illuminated by the Sun so with access to solar energy all the time. At low latitudes, colonists would have to contend with extreme temperature variations, plus the 354-hour-long lunar night. But they could make use of one of the tunnels formed long ago when basaltic lava flowed on the Moon. The lava tubes can be as wide as 300 meters. They maintain a stable temperature of 20 °C as well as provide protection from cosmic rays and meteorites.
A Moon base would be most valuable as a waypoint between Earth and Mars, and points far beyond. The Moon's low gravity and slow rotation mean that a space elevator could be built with materials already available. The honeycomb fiber called M5 is lighter and stronger than Kevlar; a ribbon 3 centimeters wide and 0.02 millimeter thick could support 2,000 kilograms on the lunar surface or 100 climbers with a mass of 600 kilograms each, evenly spaced along the ribbon. We could build a lunar elevator right now. The $35 billion development cost mentioned earlier does not assume a space elevator; it would reduce this cost by 20 to 30 percent. Bill Stone has formed the Shackleton Energy Company to prototype technology to separate lunar water into hydrogen and oxygen for rocket fuel. He knows that producing the fuel on the Moon will slash the cost of going elsewhere in the Solar System. To man his base, he won't be looking for typical NASA hires; he wants people with the spirit of wildcatters. To get back home, the first crew will need to produce the fuel for their journey.
With all this potential, it's safe to predict that the long hiatus in lunar exploration is over. In early 2014, China's Jade Rabbit rover arrived at the Bay of Rainbows in the northern part of the Mare Imbrium or Sea of Rains. The private sector is showing interest. The Google Lunar XPrize was announced in 2007, with a $30 million grand prize to any team that lands a robot on the Moon and sends it 500 meters across the surface while sending back high-definition images and video. There are eighteen teams in the running, and several might reach the Moon before the deadline of December 31, 2015. India and Japan have plans for a lunar base by 2030; while Europe and the United States are currently dithering, they may collaborate on a base with a similar time frame.
Meanwhile, the space miners have their eyes on helium-3, an isotope of helium that's a key ingredient in a viable fusion power reactor. Helium-3 is extremely rare on Earth but more abundant in the lunar soil, where it's been generated over billions of years by the solar wind. The idea is that fusion is the future of energy generation when coal, gas, and oil start running out, as they will around mid-century. Fusion is a clean form of energy that leaves no radiative waste and has a high energy yield per kilogram of fuel. But fusion is extremely challenging. Europe and the United States each have been investing about $1 billion per year, with no energy-producing reaction sustained for more than a fraction of a second. Most fusion research involves two isotopes of hydrogen: deuterium and tritium. The technical challenge is to contain the reaction, which takes place at a temperature of millions of degrees, far above the melting point of any known material. Helium-3 fusion requires even higher temperatures, but it has the advantage of generating most of the reaction energy in the form of charged particles, whose energy can readily be harnessed. The levelheaded view is that the Moon isn't going to rescue us from energy profligacy. Helium-3 presents three unproven realms of technology: harvesting it from the Moon, transporting it back to the Earth, and using it in a fusion reaction.