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Janis Jaunbergs - Latvian Astronomical Society - "The Starry Sky" The possibilities for Mars colonization Mars was elevated to the status of another inhabitable world already
in the We are pretty sure now, that native Martians are no more than microbes in deep underground, if they exist at all. However, Mars can support a highly developed civilization. Mars is the second most inhabitable place in our Solar system after Earth. Although crewed expeditions and temporary research bases can be imagined on the Moon, asteroids, Mercury, the outer planet satellites, and even Kuiper belt objects, only Mars can provide all the necessary resources for independent branch of our civilization. Mars is warmer than most asteroids, and has relatively benign thermal environment, compared to the Moon or Mercury. Humans on the Martian surface would not be endangered by solar flares, and would be shielded from more than half of galactic cosmic rays. Wind and solar energy together with the carbon dioxide atmosphere, permafrost water, sand and, possibly, more specific ores, is a solid foundation for Martian plastic, ceramic, glass and metal industry. Most importantly, Mars is the only known place beyond Earth, where large scale greenhouse agriculture is possible in natural sunlight. The lunar 672 hr cycle of +100C days and -170C nights is not suitable for terrestrial plants. Simple and robust locally produced inflatable greenhouses would allow Martian civilization not only to grow independently, but eventually to compete with Earth for supplying any future industrial operations in the asteroid belt. Creating the second major branch of our civilization on Mars will mark the permanent spreading of terrestrial life beyond the gravity well of Earth. Along with the enormous emotional and philosophical significance that will also be a major step towards security from natural or artificial disasters that may threaten us, if we forever remain a single planet civilization. Piloted round-trip expeditions to Mars should be a logical beginning of Martian colonization. In order to understand, why Apollo lunar flights were not followed by simple flights to Mars on the same 140 ton LEO lifting capacity Saturn V launchers, we need to take a look into the post-Apollo politics. From the first ICBM's up until the Moon race piloted spaceflight served the superpowers as source of military and technological prestige. After Apollo there was no more need for setting new "altitude records" by going to Mars. Space seemed to hold more promise for zero-G industry than interplanetary sports. Orbital industrial complexes was the dream resulting in Space Shuttle and orbital stations. Unfortunately, piloted LEO activities have failed to result in much more than lucrative $5 billion/year subsidies to the aerospace industry, long term employment source for NASA and a very serious financial competition for going to Mars. The orbital station supporters need Mars only to justify the necessity for orbital stations, while dedicated Mars hardware validation and crew training missions in LEO would be cheaper and much more relevant. The efforts to combine orbital stations with piloted Mars missions, such as assembling Mars bound hardware in orbit, or, worse still, on the Moon, in 1989 resulted in a monstrous sketch, called Space Exploration Initiative, with $450B price tag rivaling Strategic Defense Initiative. It is clear that human flight to Mars can happen only as a narrowly focused project. The search for such realistic scheme was begun in early 1980's by Mars Underground, a group of mainly aerospace and planetology students. The project created by Mars Underground relies exclusively on existing technology and needs no orbital infrastructure, therefore it is accordingly called Mars Direct. The flight to Mars is not the hardest part of a Mars expedition: although a 6 month flight from Earth to Mars requires 4.3km/s excess speed over LEO, aerocapture at Mars would not require major propulsive maneuvers. Saturn V class launcher with 140 ton capacity to LEO can inject about 40 tons in trajectory to Mars, and roughly 25 tons could be delivered to the surface, the rest being heat shield, parachutes and small terminal descent propulsion system. The 25 ton payload would include habitat, life support resources, crew rover and a crew of 4. Using atmosphere for braking makes the Martian surface more accessible for cargo than the much closer but airless lunar surface. It is much harder to deliver the Earth Return Vehicle (ERV) within the mass limitations of 25 tons. Return vehicle has to accelerate the crew cabin almost to 8km/s, practically the same as achieving low orbit from the surface of Earth. Short of thinking about nuclear thermal rockets or similarly exotic technologies, for a crew of four in a 10 ton Earth return capsule that means at least 100 ton (full mass) two stage rocket, or somewhat smaller single stage rocket to Mars orbit, where it would dock with additional Earth return rocket stage. Mars Direct uses the first option, preferring not to leave mission critical hardware in Mars orbit. The second option is nicknamed Mars Semi-Direct, and it starts to attract some interest from NASA. Mars Direct 100 ton full mass ERV would be delivered to the Martian surface without the ascent fuel as a separate 25 ton cargo. After automated landing it would unload Earth controlled rover with a compact 100kW uranium reactor, similar to those used on navy subs. The rover with reactor on it would move some 100 meters away, unreeling power cable in the process. As the reactor is activated, it would start supplying energy for a compact carbon dioxide electrolysis plant, built into the ERV. During one Earth year some 70 tons of oxygen would be produced and liquefied to fill the oxidizer tanks of the ERV. The electrolysis side product carbon monoxide is too weak a fuel for the ERV. Liquid hydrogen would be the best, and it may be produced on Mars from Martian permafrost. For the beginning, however, methane can be used, as it is both a very powerful fuel, and can be easily made from either Martian carbon dioxide or the electrolysis side product carbon monoxide. The latter option is the well known industrial Fischer-Tropsch process, used to make synthetic fuels from carbon monoxide and hydrogen. Although initially hydrogen would have to be imported from Earth along with the empty ERV, hydrogen is very light substance, and merely 6 tons would suffice to produce 20 tons methane, all that is needed along with the 70 tons of oxygen to fuel the ERV for the trip home. Later use of the local permafrost hydrogen in a modified Fischer-Tropsch process would let to produce raw materials for Martian plastics and rubber industry, the same way as fossil fuels serve these industries on Earth. Only in the next launch window, when ERV would have converted its hydrogen feedstock into fuel and oxidizer for the return flight, crew would be launched in its Hab with enough life support consumables for the trip and for 500 days of intensive work on Mars. Another ERV would be launched on another 140 ton LEO capacity launcher for the second crew, which, in turn, would be launched after two more years. The crew Hab, basically a tin can design, would remain tethered to the spent third launcher stage, and with a small rocket maneuver would start rotating around the common center of gravity, with high enough speed to imitate the 0.38g Martian gravity. Only if tether snaps, crew would be left weightless, but that is a very unlikely inconvenience. More likely, astronauts would occasionally have to hide for a few hours in solar particle storm shelter, protected by layer of food and water. Hard cosmic rays, however, can not be stopped that easily, and Mars travelers will have to accept approximately one percent additional risk of a lethal cancer in later life. That is, however, much less than what tobacco smokers risk, while staying on Earth. The prolonged isolation, code named "psychological factors", is not a critical problem, either. The success of Arctic and Antarctic explorers has proved better than any psychological research that it is not that hard to form a good Mars exploration team. Two engineers, responsible for the hardware, and two experienced field geologists after couple years of training in some desolate corner of Antarctica would definitely know if they are up to the task of going to Mars. 6 months after the launch the crew Hab would graze the outer atmosphere of Mars, and, after loosing some speed, they would remain captured into Martian orbit. Going higher, they would have the option of flyby and free return back to Earth. Going deeper, they would aerobrake below orbital velocity and land. Aerocapture may be the best decision, allowing to wait for the perfect landing weather. Landing precision with a good autopilot should not be less than couple hundred meters from the ERV, the feat achieved by Apollo 12, landing near the Surveyor 3 on the Moon in 1969. If the distance is much greater, the crew rover would allow to reach the ERV anyway. In the case of a major mistake, let's say, if landing occurs on the opposite side of the planet, the second ERV, trailing the first expedition crew in its trajectory to Mars, would be diverted to save the first crew, and the second crew would land by the first ERV two years later. Finally, the crew would have enough resources to survive until the third ERV arrives with extra supplies two years later. Hardware accumulation on the Martian surface allows possibilities for improvisation in the case of unexpected difficulties, and, in longer term, makes the whole Mars accessible for human travel. If every expedition lands within a rover's reach from another Hab and fuel production plant, left behind by some older expedition, Mars would gradually become enveloped in a network of inhabitable bases. Crew rovers therefore are a crucial tool for Mars development. Long excursions from the base will also be needed to reach a large variety of interesting research sites, and the crew will thus depend on their rover as on a small, mobile base. For high power to mass ratio and long distance capability internal combustion engine is the leading choice, with the same methane/oxygen fuel combination that would be readily available from the ERV fuel plant. Breathing atmosphere in the pressurized crew cabin then could be maintained directly from the oxidizer tank. After a suitable site is found for more serious development, the newly arriving Habs would be concentrated there. Much of the effort would then be shifted from research and merely surviving to building permanent infrastructure for permafrost mining, greenhouse agriculture and materials production. It would probably be cheaper to switch from imported uranium reactors to locally produced solar cells or wind turbines then. As the base gradually becomes independent of Earth imports for most of its basic needs, many of its inhabitants might choose to stay in their highly paid jobs on Mars longer than the initial 500 days, and probably would not plan for return at all, effectively becoming Martians. The contradiction between the NASA investment in Space Shuttle and Mars development is not absolute. Any heavy lift vehicles suitable for Mars missions would most probably be based on the Shuttle heritage. If instead of the Shuttle orbiter a hydrogen/oxygen third stage would be mounted on the external tank, a configuration known as Shuttle-Z would be obtained, capable of launching 130 tons into LEO, appropriate for a minimalistic 4 person Mars Direct mission. Ten years from now, when International Space Station will be old and everybody will be finally bored with it, Mars missions might be the next big NASA project. The current NASA Mars expedition sketch utilizes a Mars Semi-Direct scheme, calling for three Shuttle-Z launches: one for a crew of 6, one for ERV, and one for the additional Earth return rocket stage that would be left in Mars orbit while crew does its job on the surface. Assuming the average price of each launch, including the payloads, to be $1 billion, Mars Semi-Direct flights would cost $3B every two years, or 50% of the current Shuttle program. The classic Mars Direct is cheaper, and could be accomplished by private enterprise. The main short term commercial value of Mars flights would be entertainment and national pride. Those countries, which are interested in sending their representatives to Mars, as well as supporting their aerospace industry and securing themselves respectable place in history, could award, for example, a $20 billion prize to the organization which first builds a manned base on Mars. $20 billion certainly is a serious amount of money, but it is only half of the recent International Monetary Fund $40 billion help to South Korea, and merely 36% of the $55 billion help to Indonesia. The chief advantage of private Mars base would appear later. Private enterprise doesn't have to spend time and money for political maneuvering, its resources can be instead devoted to establishing financial profitability and therefore independence from Earth's governments. After the initial $20 billion investment Martians should be able to manufacture enough oxygen, water, food, fuel and other basic materials, so that the need for Earth imports would be reduced mainly to specific machinery and more people. The main export would be information about Mars: its climate, geology and the possible underground life. Mars rocks and property rights could be also sold to Earthlings. The most unique export, possible only from a manned base, would, however, be the adventures and impressions of our first extraterrestrial colonists. If Martians would manage to capture a decent share of the Earth's science fiction market, that alone would provide enough funds for the import of several tons from Earth in every launch window. Regardless of the exact financial and technical scheme, popular interest is the main force necessary to achieve piloted Mars expeditions. In order to popularize the idea of affordable Martian colonization, Mars Society was founded in August 1998 by the members of the initial Mars Underground group. The first project of this non-profit group is a simulated Mars base in the Canadian Arctic, and further projects will probably be small research or engineering payloads on the robotic Mars missions by NASA, in order to conduct research, to gain credibility, membership base and political influence. The readers of "The Starry Sky" are, of course, invited to join this growing movement towards Mars. Closer information is available from the Mars Society website (http://www.marssociety.org/). Mars Direct mission architecture is described in excellent detail in the popular book "The Case for Mars" by Dr. Robert Zubrin. "The Case for Mars" book, on which is also based much of this article, is available in the Latvian Astronomical Society at the wholesale (half) price. Janis Jaunbergs |
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