New Mars Forums

I apologize, but I don't completely understand. You note that conditions on Mars will be tough. In what sense? For example, when the Erie Canal, Transcontinental Railroad, and Panama Canal were built, conditions were tough; i.e., food was dangerous to eat, no one was treated for disease adequately, and thousands died of illnesses (especially on the two canals listed). But I doubt anyone will be eating rotten (literally) food on Mars, nor will there be huge problems with illnesses. Because of the potential media coverage such problems will receive, they will be avoided.

People will have to work hard, and there will be shortages of necessary items. But if a mining company on Earth wanted to open a Mars operation, the reaction wouldn't be to refuse the offer or confiscate the equipment after it arrived. Rather, the extra hands and equipment would be welcomed. And since the sending agency would be embedded in terrestrial culture, capitalism would be alive and well; in other words, refusal to allow capitalism on Mars would simply dry up the investment capital that will expand the place.

Do you see my confusion?

                       -- RobS

There have been many speculations about Martian government in science fiction novels, Mars Society conventions, e-mail listservs and bulletin boards, and even in NASA reports. The subject of government is dictated by several related variables: population size, economic basis for settlement, the extent and nature of terrestrial involvement, the legal basis for government and ownership, and other factors. In exploring the evolution of Martian government and society over time, it might be useful to think in terms of three or four time periods. They could be labeled chronologically: initial, medium term, and eventual. Or they could be labeled demographically: the station, the hamlet, the village, the town, and the nation. The first stages are smallest, closest to us in time, and the most predictable, while the last stages are the most speculative, the possibilities cover the greatest range, and the possible departure from Earth models is the greatest. In the following I will use the demographic terms, which reflect the size of the Mars population (less than about 12; 12 to about 150; 150 to about 1000; 1000 to several thousand; more than several thousand).

1. The Station. Whenever a crew touches down on Mars for the first time?probably four people, though it could be three or as many as six?the ?government? will be quite simple. Someone will be the commander, someone else the vice commander. Both of those people will also be occupied full time by other tasks: geologist, mechanic, or whatever. They will stay one ?cycle? (that is, arrive on one opposition and depart on the next) and will be replaced by a second crew of similar size. But at some point a crew will be able to stay more than one cycle. This is probably dependent on partial food production and recycling of wastes on Mars. It could occur as quickly as Mars 2. Note that currently the travel opportunities between Earth and Mars mean that the first crew leaves Mars about nine months before they are replaced. The nine-month gap could be covered if recycling was available to stretch supplies, there was more than one Hab for backup, and an entire crew (or at least two members of one) signed up to stay two cycles. If eventually one aimed for an average stay of three cycles, recruiting crews only from those willing to commit at least six years to Mars, with four people being replaced every cycle, Mars would have a population of twelve. At this size, there is still no need for a ?government? per se, though there will be a need for staff meetings. If the missions were being sent out the way NASA sends them now, we can roughly predict the sort of structure the Mars station would have, with a couple of heads of departments (?bosses?) and a fairly informal, egalitarian environment. If the crew is ethnically diverse, one hopes the Mars experience will weld them into a more or less unified whole.

2. The Hamlet. The Mars population could grow beyond a dozen or so if the Hab (as described in The Case for Mars) were expanded into a three or four story ?Habcraft? (as described in The Case for Mars, pages 231-232). A habcraft can hold 24 people and would weigh about twice as much as a Hab, or seventy tonnes. It would require a nuclear rocket or a solar thermal rocket supplemented by chemical engines to get to Mars on the same 145-tonne lift vehicle as Mars Direct uses. Presumably for safety purposes it would be wisest to send two Habcraft at once, so if trouble developed with one, the other could serve as an emergency shelter. It might also be wise to send the Earth Return Vehicle along in parallel, so that three vehicles were available in emergencies. It would probably also be important to launch a ?cycler? which would be a space vehicle in a permanent twenty-four month orbit around the sun. It would pass Earth when the mission departed from there and would fly to Mars in six months. The Habcrafts and ERV would dock to it. It could be as simple as a spare Habcraft with a docking module, emergency consumables, fuel, and solar panels. It could even have a greenhouse that could be operated remotely when no one was on board. The cycler might need some fuel to modify its orbit to reach Earth at the right time; I don?t know celestial mechanics well enough to know how much Mars?s gravity can do.

At Mars, that planet?s gravity would bend the cycler?s orbit so it returned to Earth in twenty months instead of eighteen, in time for the next mission. Another cycler with a Habcraft attached to it would pass Mars at the time a flight was returning to Earth to provide a similar backup capacity and ample space for the return trip. On reaching Mars, one of the two Habcraft could remain on Phobos to provide a return vehicle; the other Habcraft and the ERV would land on Mars, together carrying all the passengers down.

Under these circumstances, the Mars population, renewed at the rate of 48 people per cycle, and assuming an average stay of three cycles, would grow to 144. If Habcrafts cost about the same as Habs, the budget for the operation would be similar to the budget to send four to Mars, except it might involve three heavy lift vehicles every cycle. Presumably at some point as tourism develops in Earth orbit, the cost of Mars flights will drop. The biggest expense for any space venture is to reach to low earth orbit. Right now with the Space Shuttle the cost runs about $10,000 per kilogram. If the cost drops to $1,000 per kilogram, then the big expense is cut to a tenth of what it is currently.

What government does a hamlet of 13-144 need? Presumably at this size, agriculture has been developed and it may be possible for some couples to stay and raise a family. Small children probably should not fly in interplanetary space, but college students could, so once a couple had children on Mars they?d have to stay at least 15-20 years. If their living quarters were under several meters of regolith, radiation levels would be close to Earth normal, so it is feasible to have children. There are possible problems: Martian gravity may be bad for developing bodies; and children exposed to no cold and flu germs for twenty years might have to spend their first year on the Earth in the hospital, battling all sorts of microorganisms.

A hamlet will need a clinic, a school, family housing, and probably a store, among other things. The school might include provisions for graduate education, as people might arrive half way through their doctorates and would have to finish them up under the watchful eyes of a local geologist or exobiologist. It would definitely have to include full day care for children as young as three months, so as to free up as many people to do work as possible. In many ways, it might function like an Israeli kibbutz. A hamlet would also have the ability to process local materials to fabricate metal, plastic, fiberglass, and glass parts, an ability that could require the importation of hundreds of tonnes of additional cargo. Some of that would include automated equipment and robots. We are close to developing robots to carry out tasks like picking tomatoes; presumably tasks such as that will fall to robots on Mars.

It may make sense for the Commander (appointed by the sending space agency) to have to interact with a Council elected by the hamlet?s residents. If the elections occurred every cycle several months after the new mission arrived, it could represent the new arrivals as well as the old hands. At this point, since the people arriving are not all staying a long time and because the weight of terrestrial cultures will still be heavy, it seems likely that the elections will be similar to those on Earth. An alternative would be to use a New England-style town meeting to serve as a legislative body. With a population of 144 (perhaps 200, if there are a lot of children) there will also be the need to register marriages and births, oversee divorces, and settle disputes. A part-time judge may be needed, who would receive legal advice from terrestrial judges selected by the space agency. The hamlet would therefore possess rudimentary executive, legislative, and judicial branches.

Even at the hamlet level, economic forces will play a role in the further development of Martian settlement. Antarctica?s population balloons to several thousand people every summer, a demonstration of the money attached to pure science; but each Antarctic resident costs tens of thousands of dollars to put there, not tens of millions. If, when Mars gets to the hamlet level, it costs two billion dollars per cycle to send 48 people there, then the cost would be $40 million per person. It would be possible to get many nations to shell out $40 million to place a national citizen on Mars, so that might be one source of funds. The development of scientific and tourist facilities on the moon will also help drive down the cost of Mars settlement because travel times to the moon are much shorter and the same equipment could be used in both environments. But further expansion of Mars inevitably will require some economic incentives and return on the money invested there. Where can those economic incentives be found? Several come to mind.

A. Methane/oxygen fuel from Phobos. In another paper posted on the bulletin board I describe the value of developing a refueling station on Phobos. A Hab, a 4.5 tonne nuclear reactor, a drill, some tanks, and a gas processing unit?mostly items developed for Martian exploration or possibly lunar polar exploration?could inject reactor waste heat into a shaft drilled a hundred or more meters into Phobos, breaking down hydrated minerals and carbonaceous compounds, releasing water vapor, carbon dioxide, methane, and hydrocarbons that could be processed into methane and oxygen fuel. The first use of the fuel would be to replace the two-stage ERV proposed for Mars Direct with a reusable single-stage-to-orbit vehicle of roughly the same mass. A twenty-tonne vehicle (empty) fueled with a hundred tonnes of methane and oxygen fuel could carry about thirty tonnes of cargo to Phobos, where the vehicle could refuel with another hundred tonnes of fuel and head for Earth.

Extra methane and oxygen could be accumulated on Phobos and sent to Earth every cycle. A hydrogen tank used by a solar thermal or nuclear thermal rocket and storing one hundred tonnes of hydrogen propellant could store about 1,600 tonnes of liquid methane and liquid oxygen instead. If some of the fuel were burned to get the rest on a minimum energy course back to Earth, and more burned to lower it into low earth orbit, and if gentle aerobraking were used over a six month period to lower the orbit without use of fuel, one could get about a third of the total into low earth orbit, or about 500 tonnes. That would be more than enough propellant to send the entire next Mars expedition to Mars. If the fuel were worth $1,000 per kilogram in low earth orbit, its total value would be a half billion dollars.

B. Rare materials from the Martian surface. A reuseable ERV/Mars shuttle and a Phobos refueling station would allow transportation of very large loads back to low Earth orbit. Gold is worth about $10,000 per kilogram (ten million dollars per tonne) and if remote sensing allowed the discovery of a Martian Klondike or Sutters Mill, astronauts might be able to pick up a tonne or more of gold as nuggets on the surface. It would be well worth importing a centrifugal sorting machine into which a Martian front-end loader could pour gold-rich regolith. Deuterium is of a similar value and is easier to extract from Martian water than terrestrial water because of a six-fold enrichment factor. The Martian surface is littered with millions of tonnes of nickel-iron meteorites; the first asteroid mining will occur on its surface.

If uranium deposits are found, it might make sense, in the hamlet or village phase, to send to Mars either compact centrifugal separation equipment to concentrate the useful Uranium 235 isotope from the far less reactive U-238, or to send a small breeder reactor to Mars to convert U-238 to Plutonium. The transport of radioactive substances into space is one of the most controversial aspects of space flight in general and the Mars Direct project specifically, because of the perceived danger to the terrestrial environment if the rocket explodes. If Mars could provide the fuel for reactors, RTGs (radioactive heat sources for making electricity), and nuclear engines, then unfueled devices could be lifted to low earth orbit and fueled there. But the ability of a Mars base to supply uranium and plutonium is a function of how much the necessary tasks can be automated (to reduce the personnel necessary), how much the equipment?s weight and power demands can be reduced, how much money can be invested in the necessary technology, and how much the resulting technology can be declassified. Otherwise, Mars could have security agents and spies disguised as planetary geologists before it has policemen.

The final, obvious export Mars has is rocks. A search of the web reveals that right now Mars rocks recovered from Antarctica sell for hundreds of dollars per gram. If Mars rocks were flown to Earth and sold at the local mall for $25 for a one-ounce (25 gram) sample, and $10 made its way back to the Mars mission, and a million people worldwide bought such samples, then 25 tonnes of rocks would be needed and they would raise $10 million dollars. If fossils are ever found on Mars, a large fossiliferous rock outcrop could be chopped up and sent here and sold for possibly several times more.

C. Land. The sale of Martian land would be feasible as soon as Mars has a permanent settlement, and as the population and facilities there grow, demand for land will gradually increase. One psychologically important factor would be to develop ?roads? on Mars as soon as possible. These need only be bulldozer tracks that push rocks aside and smooth the surface for wheeled vehicles. It would relatively simple to develop vehicles on Mars that can drive themselves down cleared roads, either navigating from barcoded pole to barcoded pole, or using image recognition software and an image of the entire route, or following the coordinates fed to it from a Mars global positioning system. Roads connecting stations to each other and to interesting geological sites would be the most intensively photographed sections of the planet, and thus if the land were sold, the owners would have access to images of their property. If land were sold for $1,000 per square kilometer, it would be possible for Mars enthusiasts to buy their own little corner of desert. Multinational corporations could spend millions and buy thousands of square kilometers. If owners had to pay an annual claim maintenance fee of $25 per square kilometer, the money could be used to provide them services or to pay for the hamlet?s budding school. Some of the residents in the Mars hamlet would devote their time to exploring the planet, with a priority given to purchased land so that the owners acquire more information about their property. If something valuable was found on someone?s land?say, exposed chunks of nickel-iron meteorite?those resources could be given priority for exploitation and the owners paid a royalty for them. While this approach costs money, it probably would generate more money than it costs, because people are more likely to buy something if they think they might get a return on it.

The ultimate right of a landowner is the voting right. As landowners begin to increase in number, it would make sense to create a second legislative body that they would elect. Thus a ?Mars Council? would be elected by the residents, a ?Mars Assembly? by the landowners. This approach again makes the ownership of Martian land attractive. If even small-scale owners have a vote, one has the potential to create a large, diverse, grassroots movement on Earth that supports Martian settlement. Individuals with great enthusiasm could buy their own square kilometer and vote. Those wishing to keep Mars red could buy a square kilometer and be heard. Multinational corporations could have one vote as well, and would be heard.

3. The Village. The village will develop when the various economic returns listed above gradually mature, developing a stronger financial basis for Martian settlement. The village will have something the hamlet and station might never have had?senior citizens, persons who arrived in their early adulthood, raised families, and remained. The village (population, 150-1,000) will be possible only if transportation costs continue to drop. The use of solid core nuclear engines could reduce the cost of flying hydrogen to low earth orbit from the moon, or an airbreathing, fully reusable single stage to orbit vehicle might have been developed. If launch costs to low earth orbit fall to the $100 to $200 per kilogram range, tourism to hotels in low Earth orbit will be possible for $50,000 to $100,000. Flights to the moon will drop under $1 million per passenger, meaning that rich tourists could go for a month at a time, and university professors teaching lunar geology could get research grants to spend their summer hiking around Tycho. One-way flights to Mars could drop to $2 million (150 tonnes of fuel would cost $30 million to put into orbit and a nuclear engine could use it to push a Habcraft with 24 people plus maybe forty tonnes of cargo to Mars), meaning faculty with large research grants and a two-year leave of absence could go to Mars, corporations wishing to develop a presence on the Red Planet could send teams, media conglomerates could send a journalist, and wealthy private settlers could be accepted.

One consequence is that the entire population, or the vast majority, would no longer be working for the sending agency, forcing new questions to arise: can corporations own their own property? What about individuals? Should residents be allowed to buy their apartments and sell them later to the highest bidder? Should individuals who paid their own way to Mars be charged income and property taxes? Should agency employees be allowed to quit, stay on Mars, and set up their own companies to mine minerals, raise crops, or provide services to other residents? Under what nation?s laws would they incorporate and sign contracts? If an individual wanted to stay on Mars permanently and wanted to fly up grandmother?s Steinway piano, how much should he or she be charged? Should antiquated agency equipment be sold to a resident who wanted to set up her own company? What if the aging equipment were a Mars shuttle and the person or company wanted to set up a private flight service to Phobos and Deimos? What currency should be used in the village store? What if someone wanted to open a competing store? If a Hollywood company wanted to shoot a movie on Mars, could agency employees moonlight as actors and extras? What if a family wanted to buy an old Hab and roll it 1,000 kilometers down Route 7, and settle way out in the wilderness, all by themselves? What if Denmark?or North Korea?wanted to fly up a dozen people to set up their own station? At what point should the village have its own public access cable television channel? How will health care and retirement costs be paid for? When will welfare and unemployment services be needed? At what point should one resident be allowed to sue another, requiring the establishment of a formal court? When will Mars need resident lawyers, heart surgeons, acupuncturists, a ballet troupe (whose dancing would be spectacular in Martian gravity), an intramural basketball league, a professional hair stylist, and an undertaker? Where will churches worship, and can they buy or build their own structures? When will Mars get its first McDonalds?

At the village level regulations and policies will proliferate. The job of Commander would be a full time. Possibly his/her appointment by the agency would have to be affirmed by the Mars Council and Assembly, or by popular vote. It seems inevitable that there will be private property, mortgages, taxes, health insurance, and a bank branch with ATMs. Consumer goods will still be rare and expensive, but a few will now be manufactured on Mars, and some of them might bear designer labels.

4. The Town. Expansion of the Mars population over 1,000 will require the establishment of a real economy. While Mars might still be receiving annual subsidies?probably of billions of dollars?it would also be exporting by the time it reaches the town phase. With automated manufacturing, a population of 1,000 could provide considerable support for asteroid missions. It might be providing occasional flights to Venus orbit and Mercury to ship fuel, cheap manufactured goods, and raw materials to stations there. A Venus orbital station studying that planet robotically and by remotely controlled aircraft and balloons might be growing their food and recycling their wastes in agricultural units using reprocessed regolith from Phobos. The Venus station might be accumulating water in the Venus clouds using solar powered aircraft, concentrating the deuterium?which is far richer on Venus than on Mars?then selling the deuterium to Earth. The Mercury station might be mining Helium 3 from the Mercury regolith, where it should be far more concentrated than in lunar soils, and the equipment it uses might be made on Mars and shipped via Phobos.

By the time Mars has a town, advanced nuclear or ionic propulsion will have reduced travel times and transportation costs further. It might be possible to send an item from the Earth to Mars for $100 per kilogram. Gaseous core nuclear engines or high-powered plasma engines might be able to fly to Mars in three months, wait a month, then fly back to Earth in three more months, making tourism, grant-funded individual scientific research, and the visits to Mars of medical specialists possible.

5. The Nation. It is difficult to say how many more steps would be necessary before a nation-state (or several nation states) emerge on Mars. Because of the extreme shortage of services, for a long time Mars will probably have a single large population center where the hospital, high school, bank, store, etc., are located. This argues in favor of the eventual emergence of a single nation. Alternately, if Earth?s age-old rivalries are transplanted to the Red Planet, a single central population concentration might not emerge; rather, separate American, European, Chinese, and perhaps Russian villages and towns could emerge, speaking their own languages and selling goods and services to each other. There is likely a relationship between financial self-sufficiency and independence; once the colonies begin to cover their own costs, independence becomes likely.

A nation state might be possible with only a few thousand people. When the Massachusetts Bay Company set out with less than a thousand settlers for New England in 1630, it was setting up a de facto independent settlement that was not brought under royal control for a generation. Cleverly, the charter of the Massachusetts Bay Company?approved by the King?did not specify where the annual meeting of the stockholders would be held. Thus while wealthy English merchants owning shares in the Virginia Company met in London every year to select a governor of their private colony, the middle class Puritan small businessmen investing their life savings in the Massachusetts Bay Company boarded the ships themselves, sailed for Boston, and held their annual stockholders? meeting there, and the company?s governor was elected by the colonists themselves. By 1640 religious persecution had driven 10,000 Puritans to New England, where they had imported America?s first printing press, established its first college, elected its first local and regional governments, and built an economic base on the export of codfish and foodstuffs to the Caribbean.

For Mars, a planet of unexploited mineral wealth and the promise of mineral wealth in the asteroid belts might provide a similar economic base. The promise of an entire planet of land to settle, the prospect of nearly free land, and mature technologies for reliably extracting water and oxygen from local resources could open much of Mars to settlement, and if relatively inexpensive transportation becomes available, millions could emigrate to Mars, just as they did to the Americas in the late nineteenth century. The steady development of economies of Earth may make it inevitable. If per capita productivity in the United States were to grow 3% per year?as it did in the 1990s--in twenty-four years Americans will be twice as wealthy in real terms as they are today; in forty-eight years, four times as wealthy; in seventy-two years, eight times as wealthy; in ninety-six years, sixteen times wealthier than they are today. As fantastic as this seems, Americans in 2000 are about sixteen times as wealthy as their grandparents were in 1900. Average national annual incomes of half a million dollars in current dollars may be seen by the end of this century. How many will want to save for a trip to Mars? How many parents might help their children buy a ticket for Mars as a graduation present? Only time will answer these questions.

An extremely important factor is altitude. The northern cap is built on top of the northern lowlands, the southern cap on top of the cratered highlands. The southern cap is thus at a much higher altitude than the northern and experiences a lower atmospheric pressure. The vapor pressure of CO2 is very sensitive to temperature. According to my CRC, page D-150, the vapor pressure of CO2 at -135C is 1 millimeter of Mercury, but at -110C it is 34 millimeters of Mercury. Thus at high altitude, a CO2 cap will sublimate away; while it is colder at a higher altitude, it is not colder enough.

                -- RobS

These are very interesting questions. Zubrin's book gives a formula for calculating the radius and revolutions per minute for any particular amount of gravity. I seem to recall seeing in a book about space colonies that one can get 1 Earth gee at 1 rpm when the radius is about 900 meters. I'll try to find the details and post them in a few days.

I've never seen what the plan is for the Mars Direct Project's return. Astronauts have spent six months in zero gee before and they adjust fine over a week or two (well, some have longer term problems, but minor ones). I was wondering whether the burnt out upper stage of the ERV could be used as a counterweight vis a vis the crew cabin. One could gradually spin up the rotation rate from Mars gee to Earth gee, so that the astronauts gradually adjust to the higher gravity.

                  -- RobS

Josh, thank you for these data. I wish I could give you a source for this additional information, but it was preweb; probably something I read 1975-77 when I was a graduate student in planetary science at Brown. Or maybe it was in the 1980s. Someone calculated that under the north polar cap, the pressure from the overburden soon gets too high for solid carbon dioxide to exist; it sublimates under pressure unless the temperature gets lower (and with geothermal heat, with increased burial the temperature goes up).

So this makes it impossible for the northern cap to be CO2. But it might be a CO2/H2O "clathrate," which is a combination of the two compounds. There has been some research done on clathrates. One could check the old Icarus abstracts if they are on line, like the new ones are. The article about clathrates on Mars may have been there. I think there have been Icarus articles about clathrates in the Jupiter and Saturn systems, too.

Even if they are clathrates, though, it does not change the total water in the polar cap by an order of magnitude. Maybe by an order of two; but that's still a LOT of water!

                     -- RobS

Can you give a web address where more information can be found? If not, don't worry about it. I am curious how the engine works and how much energy it uses. If it could get us to Mars in three months but it takes six or eight months of energy to power the engine, it doesn't actually speed up the trip. Currently nuclear reactors weigh something like 45 tonnes per thousand kilowatts of electrical output, so if you need 10,000 kilowatts, the reactor gets extremely large (450 tonnes); or you need about 100,000 square meters of solar panels at a minimum of 4 kg per square meter, which is 400 tonnes of solar panels. This may explain why NASA doesn't spend much money on the process, too; there's no reason developing an engine that cannot currently be powered.

                  -- RobS

P.S.: I should add, though, that the figure for the weight of a reactor comes from a 1977 publication about space colonies. Maybe we can do better now (by a factor of 2 or 3?). And solar panels are getting more efficient as well.

Bill White makes some excellent points. Zubrin, in Case for Mars, also assumes that one would not use hemispheres, but "flatter" structures that do not go as high. I did my calculations with hemispheres because I do not know how to calculate volumes and surface areas of "flatter" structures. Zubrin said the thing to do is to use a portion of a sphere less than a hemisphere, like slicing the "top" or "bottom" off a globe.

Yes, a flattened hemisphere has less surface area and therefore would generate less upward pull, decreasing the amount of dirt needed to anchor a dome somewhat. Since I do not have the ability to calculate the area, I do not know what it will be. Consider that the surface area being domed over is a function of pi r squared but a hemisphere is 2 pi r squared. A flattened hemisphere would fall between those numbers, depending on the flattening.

Multiple layers do not have to decrease the available light. Zubrin says a 1 millimeter thick kevlar layer can hold in air at an entire terrestrial atmosphere of pressure. Let us say we divide the layer into four 1/4 millimeter thick layers, and let each layer approximate a true hemisphere more closely (rise higher and higher from the center of the enclosure). And let us assume that each layer holds in 1/4 of the total pressure underneath. A leak from the bottom layer into the next one would not necessarily exceed its yield strength if the layers were able to accommodate 2 or 3 times their standard design pressure, and by spreading the air out in a larger area the pressure on the second layer would be reduced anyway. Presumably 4 layers 1/4 mm thick block as much sunlight as 1 layer 1 mm thick.

As for multiple levels of plants, this assumes artificial lighting, which assumes an ample source of energy. The surface of the earth receives over 1 kilowatt of sunlight per square meter, constantly during the day. On Mars that is already reduced to less than half, which is a problem for some plants (some vegetables and grains do not grow well when they get only six hours of sunlight per day. I know; my backyard garden is partially shaded). A dome with multiple levels of plants reduces their light exposure even more. If you have to supplement 10,000 square meters of plants with artificial light, you may need 10,000 kilowatts of power to do it! It's easier to spread the plants out under domes and use mirrors to give them some extra light.

                     -- RobS

I was surprised to see that carbonaceous chondrites had so much water in them. The data comes from the web--not always the best source--but I see no reason to assume they're vastly wrong.

As I noted in another posting somewhere, there are stony asteroids, carbonaceous ones, and metallic ones. The metallic ones won't have much carbonaceous content to provide fuel for a return flight, and the carbonaceous ones don't have much metal. Most likely an asteroid can be found that is a fusion of several from collision that will have all the materials one needs for a good mining colony.

But meanwhile, Mars has all three. If one wants to mine asteroids, one can start mining the zillions of tons scattered across the Martian surface; and that effort would have the advantage of a local infrastructure (maybe even a hospital!) to provide support. Yes, Mars has a gravity well, but in terms of fuel it's much less deep than Earth's, and Phobos is smack dab in the middle of it to serve as a permanent "second stage"; Earth's gravity well is 25,000 miles per hour "deep" and that's 2.5 times the exhaust velocity of hydrogen and oxygen, requiring a mass ratio (fuel to payload) of 11.2 to 1. Mar's gravity well is only 12,000 miles per hour "deep," requiring a mass ratio of 2.3 to 1. The Mars Direct's ERV could be modifed into a reuseable "space shuttle" to shuttle back and forth between the surface and Phobos or Phobos and Earth orbit.

This is not to say that the asteroid belt won't be mined. Just that Mars will be the testing ground, because it's cheaper. It could be mined twenty or thirty years before asteroidal mining is tried, giving it a big advantage. And if you want to raise a family, the cosmic radiation and zero gravity may make that impossible in the asteroid belt; those guys (and gals) will have their spouces on Mars or the Earth.

                         -- RobS

On the subject of whether people could live in the asteroid belt, I think the zero gee problem is the big one. Ceres has about one twenty-fifth the gravity of the Earth, I think. I'm not sure resources are that much of a problem. One problem is that some asteroids are nickel iron and great for mining, but would be lousy for agriculture or extracting indigenous fuel; the stony and chondritic asteroids, on the other hand would be adequate for agriculture if you can concentrate the sunlight with mirrors, and could make lots or methane and oxygen fuel, but would lack nickel-iron for construction and export. Fortunately the regolith layer of all asteroids is made out of the stuff that has fallen on them, and that's a mix of the types, so stony asteroids will have chunks of nickel-iron and nickel-iron asteroids will have chunks of stony and chondritic material.

Before you mine the asteroids for metals for Martian factories, remember that there are a few zillion tons of asteroid material littering the Martian surface. Since it's a big place--the size of all of Earth's dry land--explorers will soon know that there's a thousand tons of nickel iron exposed by erosion in crater X and other things exposed in other craters as well. With minimal weather for the last billion years, most of the stuff that's fallen to Mars is still intact, rather like the meteorites in Antarctica.

                  -- Rob S

I have a few thoughts about domes that might help one visualize them. Zubrin's book on Mars Direct notes that a 100-meter in diameter sphere of kevlar (one of the strongest and toughest plastics ever developed) would weigh 64 tonnes. A hemisphere (half a sphere) would therefore weigh 32 tonnes. It would enclose 7854 square meters or .7854 hectares, which is about two acres. Its volume would be 2/3 pi r3 or 261,800 cubic meters. Since the mass of air at a third of an atmosphere of pressure is about half a kilogram per cubic meter, the air inside would weigh 130,000 kg or 131 tonnes. The reactor Mars Direct postulates could make that much oxygen from CO2 in less than a year.

Another useful statistic: the suface area of a hemisphere is 15,708 square meters. Each square meter, at a third of an atmosphere of pressure, will have about 3.3 tonnes of force on it (33,000 newtons, if you are a purist), so the dome will have an upward force on its outer edge of about 50,000 tonnes. The perimeter is 314 meters long, so that's an upward force of 165 tonnes per meter. If you assume a ten meter wide sleeve on the ground and Martian rock "weighs" about a tonne per cubic meter (the mass is about 2-2.5 tonnes per cubic meter, but the weight is that times Martian gravity, 0.38) then you would have to bury the sleeve under 16.5 meters (54 feet) of dirt and rock to hold it down. You could also anchor stakes in the regolith to help hold it down, reducing the dirt pile to some extent. The obvious place to put housing is under the dirt pile perimeter, so that the housing opens onto the interior space and the regolith reduces cosmic ray and solar radiation exposure to almost terrestrial levels. It's amazing you can do all that with 32 tonnes of kevlar and a bulldozer!

The floor probably should have plastic liner to help make it air tight; on top of that you'd pile processed Martian regolith. You'd want to build the dome somewhere there are ample supplies of eolian drift and clay. The big problem probably is desalting the regolith, though you might find regolith with low enough salt levels so that you don't have to desalt it for plants to grow in it. You'd have to add nitrogen and maybe phosphorous.

A landscape architect friend of mine who was designing a rooftop garden once told me you put 9 inches (23 centimeters) of dirt on a rooftop garden. That would take about half a tonne of soil per square meter, or 15,000 tonnes total. That would take machinery quite a long time to prepare; probably a year or two. Meanwhile, you could get away with less and start on one side of the floor only.

Biosphere 2, in Arizona, had an intensive agriculture area of 2233 square meters that was able to feed eight volunteers inside. Thus this hemisphere could feed about 24 people. Presumably any Mars station building such big enclosures would have several, in case one were temporarily damaged, so a 100-meter hemisphere would be built by stations of 100 or so people.

What shape would you like the dome's floor to take? It could be flat, but probably you want it sloping to a low point for drainage. The obvious thing to do would be to put a pond somewhere at the lowest point--maybe in the middle. You'd raise fish in the pond, flood a rice paddy next to it, swim in the pond for fun, and have a small barbeque patio there as well. A barbeque would put a lot of smoke in the interior, but not a dangerous quantity (assuming you had all 261,000 cubic meters of air space inside).

The dome would probably be layered; in other words, instead of one dome, you'd want a minimum of two, maybe three or four, nested inside each other. That way if one leaks the air just leaks out to the next dome, an alarm goes off, and someone has to go find the leak and fix it. If you had three or four domes, the spaces between the others could be used to store nitrogen, argon, and other inert gasses you might want to use for other purposes. Multiple domes also are essential for insulation against the frigid exterior temperatures.

I am guessing, but you may also want to draw a black insulating shroud over the dome at night to hold in the heat. If that is the case, you'd have to have it retract if you wanted to look at the stars or moons. Maybe the computer could be programmed to pull the shroud over the dome every evening at 9 p.m., giving people two hours to look at the stars.

In the morning, you'd want to pull the shroud back on the east side only and leave the west side covered with the shroud, which would be silvered on the inside. This would reflect the morning light into the dome and increase total sunlight. With skillful computerized control of a silvered shroud over the outer dome, one could raise the total sunlight inside almost to terrestrial levels. In the afternoon, the shroud would cover the eastern side of the dome.

I have two questions about the Energia Launch System:

1. Is there information on the web about the system? I am curious about the sizes and weights of the various stages, thrust, the various options, etc.

2. Does anyone have any idea how much it would cost to launch an Energia with, say, a 140 or 150 tonne payload; that is, the Mars Direct payload?