Mars Settlement Design
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Generation II Mars Settlement Study Update
2nd Atlanta Workshop, Part 2
Report Date: July 2007
Meeting Date: March 9-12, 2007
Reported by Brian Enke, Gen II Documentation Lead
On a beautiful Saturday afternoon in Atlanta, our Gen-II heroes ended part one of this report by… eating lunch. Little did they suspect the sheer terror awaiting them in the afternoon session!
Seriously, I knew the afternoon session would be “challenging” when one of the scheduled speakers approached me at lunchtime saying, “I hope they don’t toss me out the airlock when I raise some serious issues in my presentation.” I forget my exact response, but it was something like, “Don’t worry. This group is all about solving problems… and you can’t solve a problem you don’t know you have.”
Any problem solver worth her beans will tell you the importance of getting the issues out on the table, as quickly and clearly as possible. Once those nasty issues are sitting out there, exposed and defenseless, you can take a baseball bat (or whatever problem-solving tool you care to use) and beat them into… opportunities. You see, the flip side of every problem is a golden opportunity.
So… I hereby declare the theme of the afternoon to be: “Turning problems into golden opportunities.”
Through the Looking Glass…
Beginning the afternoon session at 1:00 pm, Bob Milligan discussed manufacturing cement and glass on Mars. Necessary raw elements for glass include basalt, which is common, and silica, which might be rare.
[NEWS FLASH: The Spirit rover has just discovered a deposit of 90% pure silica in Gusev Crater! Perhaps silica is not so rare after all? Thank you, Spirit! We now return you to our regularly scheduled report…]
Martian greenhouses will require large sheets of a very strong plexiglass, but should the glass be transparent or translucent? Blocking or diffusing certain wavelengths of light might be highly desirable, and the transparency requirements will determine the optimal manufacturing process and the raw materials required.
Despite Spirit’s discovery, no silica sources on Mars are quantified. We should rely upon another source for structural fiber if we are to filament wind structures and tanks. Basalt has been used as a structural fiber on Earth, and an industry has grown around this technology. Why not use it on Mars where basalt is plentiful? The basalt would be mined, crushed and beneficiated to remove water soluble contaminants. Beneficiated material is then heated in a furnace until molten and drawn into fibers through spinnerets.
Participants raised two challenges to this proposal:
  1. We have no convenient source of basalt near the proposed settlement at Meridiani.
  2. Martian basalt does not contain the right type of olivine to form a good fiber.
The first comment currently has no firm answer. The proposed settlement location is a dry seabed consisting primarily of kieserite. Locating a good source of basalt might require some traveling.
The second challenge requires up-front planning. Whatever basalt source the settlers tap must be pre-analyzed by robotics or by an exploratory manned mission. Based on this analysis, we can create a similar basalt back on Earth and determine its fiber properties. We can then calculate the number of windings needed to meet the expected loads with the appropriate margins of safety. After the colony has matured and sources of other materials have been found, the colonists can improve the fiber by melting the basalt with additives such as silica, alumina, titania or zirconium oxide.
Walking Through Cement
Bob requests a 100x100 meter facility for mineral-receiving beneficiation, manufacturing, and storage adjacent to the existing processing and storage facility (the tank farm).
He presented MOS Sorel cement as a possible alternative to Portland Cement. Calcining magnesium sulfate to magnesium oxide and mixing the result with magnesium sulfate in an aqueous solution forms MOS cement. Two drawbacks: the cement will dissolve in running water, and it has to be mixed to the right stoichiometry or it has a tendency to effloresce. Both drawbacks seem minor because the colonists will be an intelligent group of people and Mars is a very dry planet.
Bob also mentioned a Magnesium Phosphate (MAP) based Sorel cement that does not have the water problem and can be used outdoors on Earth. It cures very quickly – perhaps too quickly for some applications. Its main disadvantage: it is made with phosphates, and a convenient source of phosphates has not been located on Mars.
As discussed in part one, future settlement builders may prefer Portland-style cements because these cements can survive prolonged exposure to moisture. We leaned toward using only one type of cement throughout the entire settlement, if possible, and additives like gypsum, silica fibers, and/or propylene might broaden the versatility of a common recipe.
Looking deeper into the issues, Portland cement is prepared by mixing calcium oxide, alumina, iron oxide and silica in a kiln at temperature to form clinker. The clinker is pulverized and mixed with a small amount of gypsum. Deposits of silica, which comprise approximately 50% of the clinker weight, have not been found at Terra Merdiani. Alumina is also questionable but is more promising. Like gypsum, the iron ore will have to be beneficiated. The result is a gray powder.
Mixing magnesium oxide with an aqueous solution of magnesium sulfate creates MOS Sorel cement… hence it is a solution. One would be hard pressed to confuse a bucket of MOS Sorel cement with a bag of Portland cement. Settlers will be walking on magnesium sulfate at Terra Meridiani, and magnesium oxide is just a calcination away.
In keeping with the theme of the afternoon, the various issues associated with concrete production on Mars contain seeds of opportunity. Concrete and cement production are mature industries on Earth, but prices are skyrocketing due to shortages of raw materials. Perhaps a new formula for a future Mars-cement will find a home back on Earth?
Hot Times on Mars: Mining, Refining, and Manufacturing (MRM):
At 1:40 pm, Frank Crossman delivered the status of the Gen-II mining, refining, and manufacturing (MRM) efforts, referring to the current level as “Gen 1.5”. Frank noted some major changes to Gen-I assumptions:
  • Extract water from hydrated minerals rather than drilling for water (see part one).
  • Mine higher-grade deposits of hematite and gypsum rather than low-grade regolith.
  • Don’t assume the presence of local deposits of high-grade silica for window and fiber construction. In fact, we can assume the availability of only small quantities of silica extracted from regolith for small mass uses in electronics. (note: Spirit’s recent silica discovery half a planet away offers future promise).
  • Replace most Gen-I in-situ brick production with concrete reinforced with steel rebar.
  • Use oxides (calcined from sulfates) rather than carbonates as fluxing agents in steel refining because carbonates are rare on Mars.
  • Don’t count on manufacturing aluminum from Bytownite through a modified Bayer process, due to finely distributed impurities. However, aluminum could be recycled from the hulls of cargo spacecraft or refined through different processes using high alumina clays or phenocrystic plagioclase. These processes must be scaled up and proven.
  • Require all-electric, continuous power as input to the MRM processes, rather than a mix of electric and thermal power. Via the Sabatier reaction, electric power can generate methane and oxygen to be burned in high temperature furnaces.
  • Use less pressurized volume/footprint and more unpressurized volume/footprint for MRM processes.
  • Metal parts cannot be produced from continuous casting. Metals require plastic working to develop strength, toughness, and ductility that are needed in structural components, and plastic working requires massive milling equipment.
  • By the latest analysis, we need to import from Earth a mass of MRM equipment and materials six times greater than was assumed in Gen-I. The required mass of equipment for water extraction from hydrated minerals, metal manufacturing equipment, and mining equipment is a large fraction of the imported mass.

In a side discussion about architecture, we noted that shifting the emphasis from bricks to steel, concrete, and cement in Gen-II helps to visualize the Gen-II settlement; whereas a Gen-I settlement might look more like a Romanesque village, a Gen-II settlement could resemble an early 1900’s urban center? Bricks will probably remain a niche construction material, just as some builders still use bricks on Earth. Steel, concrete, and cement require a greater up-front investment into labor and massive equipment, but those needs can be met during a Gen-II timeframe when a minimal infrastructure already exists on Mars.

Due to the small quantity of materials needed on Mars, we must miniaturize the massive MRM equipment currently used on Earth. Settlers might prefer to use Earth technology when low mass and low production rate equipment is available, but even in those cases, huge transportation cost incentives will encourage redesigns that minimize mass. For example, reducing the mass of a rolling mill from 6 tonnes to 3 tonnes saves at least $45 million in transportation costs, based on future projections at $15,000 per kilogram (1/10th current costs).
Manufacturing large diameter rebar or wide, thick metal sheets by plastic working of metals requires mega-massive equipment that can’t be miniaturized. Settlers must use narrower sheets and smaller diameter pipes and bars produced by lower-mass metal-working equipment imported from Earth. The Gen-II settlement must strive to replace bulk strength with alternative, smarter design at an architectural level.
Rebar rolling mill (copyright: Jaime Clark / the planet)
Frank also emphasized that the MRM equipment must be repairable and rebuildable on Mars, requiring Earth-based training in assembly, teardown, and repair plus a sufficient supply of spare parts that cannot easily be produced on Mars in the near term. Examples are roller assemblies, ball bearings and electronic circuits.
Process flow will also differ on Mars. For example, automation accomplished on Earth by multiple stands of rolling mills (pictured above) will require robotic assistants working with a single rolling mill to reset mill heights and move processed slabs back and forth during the multiple pass reduction process from slab to sheet.
Break Time… Then Rockets!
After a 15 minute break, Grant Bonin and Jeremy Sotzen took center stage at 2:40 pm with their presentations on Gen-II space transportation. One of Grant’s key messages was the need for flexibility. We don’t want to marry ourselves to a single transportation architecture at this early stage. Instead, we need a plan that accommodates various mission assumptions (including robotic precursor missions) and new technologies likely to be available during the Gen-II timeframe.
In particular, Grant is closely watching the evolution of launch vehicles. With NASA’s Ares V in the early design stages and private industry considering alternatives, heavy-lift vehicles seem the most obvious choice for Gen-II material shipments. However, smaller rockets will continue to offer numerous advantages as well, including perhaps a lower overall cost achieved through higher flight rates.
Splitting the crewed Mars transits into 3-person (maximum) teams appears to be the most flexible approach, at least with current technology. After the numbers are crunched, the conservative transit mass of a 3-person habitat plus consumables is low enough (40 to 55 mT) that a mission could leave Earth via two heavy-lift launches or a reasonable number of medium-lift launches. Returning settlers to Earth is a complex endeavor that should be addressed later.
Cargo transits offer greater opportunities for flexibility and high flight rates. Transporting the total cargo mass of the initial Gen-I settlement (from 250 to 500 metric tonnes) requires many launches, regardless of the launch vehicle capacity.
Typical ratios of cargo payload mass (Copyright 4Frontiers)
After many detailed graphs and mass tables, Grant’s primary take-away messages for both crewed and cargo launches boiled down to:
  • “This is hard (in case you didn’t know)"
  • Recommend small payloads and mixed launch vehicle fleets with three-person crews, maximum.
  • The greatest choke point on the critical path is NOT the launch vehicle. It’s the Entry, Descent, and Landing (EDL) assumptions.
With that final point heard loud and clear, Grant gave the floor to Jeremy who elaborated the current status and concerns with the EDL process on Mars.
Using current EDL systems, most of which date back to the 1970’s Viking era, we can safely land about 1.8 metric tonnes of useful cargo within a 10 kilometer wide landing ellipse. Let’s see… if we need to split 500 tonnes of cargo into 1.8 tonne chunks… that adds up to a LOT of Mars landings! Yikes!!
Jeremy discussed aerobraking and aerocapture entry options, noting that traditional aerobraking takes far too long (on the order of 180 days) to be practical for crewed missions. Aerocapture is a better option but has not been demonstrated yet.
Descent requires new technologies: a 15-meter aeroshell, either a hypercone or an inflatable ballute, and a 30-meter supersonic parachute. Researchers have offered potential solutions since the 1960’s, but years of up-front development and testing would probably cost billions of dollars. A hypercone should allow us to land at least 10 tonnes of mass, and possibly 20 tonnes, reducing cargo landings to a more reasonable number (less than 50, worst-case).
Hypercone descent system (Vertigo Inc & Vorticity, Ltd.)
The Martian atmosphere, our best resource on Mars, also presents several challenges for descent and landing. We need plenty of safety margin during the descent phase because the density of the Martian atmosphere can vary by as much as 30% over single-day intervals. At lower altitudes, wind drift can increase the size of the landing ellipse. Steerable parachutes may provide a low-cost, low-mass option for shrinking the landing ellipse down to 1 km.
The numerous challenges in the EDL process lead to golden opportunities for new technology development. We need an end-to-end strategy for landing larger payloads on Mars because the Viking approach (or newer strategies devised for the Mars Science Laboratory) just won’t suffice. Also, we can’t feasibly divide the nuclear power subsystems into chunks smaller than 10 tonnes (see below)… so nuclear power within the settlement requires a reactor redesign or an up-front investment into hypercones or ballutes.
Field and Stream: Martian Munchies…
After delving into the implications of rocket launches and landings for an hour, we switched gears and talked about future Martian food production. Nathan Owen-Going discussed the latest greenhouse and crew diet research, followed by Pablo Rivera’s presentation on aquaculture.
Nathan suggested 25 greenhouse-grown crops that would provide an adequate balance of proteins, fats, and carbohydrates for a crew of hungry settlers. He recommends a diet of 2,729 grams of crops per settler, occupying 72 square meters of greenhouse space and allowing a per-person diet of 2,975 calories. His energy level targets are nearly twice the Biosphere II goals, due to his belief that hard-working settlers must burn extra calories. Nathan’s targets are close to the caloric intake for farmers or active US military field-soldiers.
Since each greenhouse includes about 200 square meters of growing space, one greenhouse is needed for every three settlers. We can increase the food density by combining water-crops or allowing for alternate sources of protein within the settlement. However, we also should maintain at least a 20% buffer on top of the diet requirements so we can build a dependable supply of excess food.
The key concerns of future Martian farmers are bio-diversity, safety from solar flares, and energy usage. Some of the greenhouses would be covered with regolith, while others aren’t. LED lighting is greatly preferred because the systems are less massive, last longer, use less power, and can be optimized to output the best wavelengths for photosynthesis.
Several in-progress brainstorming ideas involving various team members might lead to a significant increase in crop density, so the original estimates (above) appear to be quite conservative. We will also assess the relevance of key innovations toward terrestrial greenhouse applications. A complete, portable, diversified, efficient greenhouse system integrated with a water recycling system could open up tracts of hostile terrain on the Earth to off-the-grid habitation.
Integrating the wastewater systems remains a key challenge, especially when aquaculture is added as a primary protein source for the settlers. Pablo has sketched some feasible aquaculture system diagrams and has itemized the materials that are needed in-situ or from Earth. He aims for an 8 to 1 food conversion ratio, with 28 weeks required to raise fish 500 grams in size. A crew of twelve would consume about 1800 fish (900 kilos) every four months, with excess capacity of 300 kilos. This works out to roughly one fish per person per day. Other biomass in the system includes algae and plankton.
The New Jamestown…
Though the afternoon was long and exhausting, most of us were still “on Mars” and wanted to continue. During a short break, we decided to push through the remaining topics before splitting into smaller groups and dining out. Next on the agenda was nuclear power, and the title of John Graham’s presentation conveyed the importance of this topic: “Enabling the New Jamestown.”
A growing Martian settlement will have ever-increasing power needs, with the largest amounts of energy consumed by the agriculture and manufacturing subsystems. Diverse systems are important (solar, RTGs), but most of the settlement’s power requirements will be met by tripleredundant (internal and external), 4 megawatt nuclear reactors. John outlined a new design utilizing a 91-pin core mesh with 6 control cylinders. The new reactor would achieve twice the electrical output of a system designed at MIT in 2003.
CO2 from the Martian atmosphere would cool the system. Dust is a problem, so filters must prevent clogged coolant channels. The system must be safe, redundant, portable, seismic tolerant, and able to survive landing stresses. It must also be small (3x3x2 meter footprint) and modular. If the system is shipped to Mars in pieces, putting it back together would require a clean room and several nuclear-capable engineers, hence the importance of designing the reactor to accommodate our Mars descent capabilities (see above).
Footprint of the nuclear subsystem, vastly simplified
Longer term operation poses additional safety concerns. Once the reactor is running, maintenance techs can’t approach the reactor unless it is shielded. The heaviest components require a crane for lifting and moving, but trucks could deploy the system initially.
Continuing the energy we had built up, Kristin Showalter led a discussion about alternate energy sources and surface transportation. Part of the challenge with energy is transport, i.e. getting the energy to the right location in the right form.
Remote mining facilities will require large amounts of energy, and tying these sites into the main grid isn’t feasible. However, settlers could generate methane and ethane at the central settlement, transport these fuels to remote locations, and produce electricity and heat with portable generators. Modular pressurized container-trucks could transport the fuels to the remote mining sites and haul ores back to the settlement. Transporting the ores already requires an infrastructure of roads and grading equipment, so energy transportation doesn’t add much complexity into the transportation system.
Kristin will consider other on-site alternatives too, including solar, wind, and even geothermal energy. None of these options currently looks very attractive. Beaming power to remote locations might assist some applications.
Who Will Do All This Work???
By 6:00, stomachs were rumbling and thoughts were beginning to stray toward dinner. However, two extremely important topics remained – and both were human-focused. Ned Chapin began his presentation by pointing out that all this talk about equipment was fine but pointless unless we also focus on the people running the equipment.
Psychology, communications, and work dynamics enable the systems to run efficiently. Our strategy of enabling Mars settlement by combining the best of humans and robotics/systems will only work if we pay equal attention to the human factors.
Will settlers spend as much time in meetings (requiring meeting rooms with built-in audiovisual equipment) as their Earthly colleagues? Will they control vehicles and machines remotely through telerobotics? With the nearest paper mill millions of miles away, will the Martian workplace be paperless out of necessity? How will we avoid accidents on the roadways around the settlement? Will all door keys be electronic? Will sign-language be used extensively outside the settlement? We must address dozens of similar questions throughout the settlement design process.
Paul Graham echoed many of Ned’s concerns when he discussed spacesuit design. Technologies like wireless broadband internet and voice-over-internet (VoIP) might allow seamless interpersonal communications out on the surface of Mars, as well as efficient interaction with robots and other equipment. The infrastructure requires flawless navigation and reliable communications via solar-powered relays. To avoid accidents, all mobile equipment must have the intelligence to recognize and avoid humans and other equipment.
Due to the importance of tele-operation, perhaps we should build tele-op equipment directly into each spacesuit? Again, numerous questions were raised. We noted the importance of Mars Society research into analogue field procedures and human factors.
Regarding the actual space suits, mechanical counter-pressure (MCP) suits seem superior to existing hard-shelled suits. MCP suits potentially offer greater flexibility, comfort, and ease of use/re-use. However, no one has built a fully functional MCP suit yet… so some skepticism is warranted too. (For more information, click here to explore Innovative Technology).
A Mars MCP suit design (Dava Newman)
And Now, an Unpaid Advertisement for Applebees
The afternoon session ended at 6:45. Our group broke apart into small hunting parties and ventured out into the wilderness of the Atlanta suburbs, foraging for food at several local restaurants. Our initial efforts met with little success, due to overhunting by natives, but some of us eventually found a welcome oasis at Applebees.
During dinner, we discussed a wide range of topics from art to literature to habitat design – yes we did sneak in some business talk too. The conversations continued after we returned to headquarters… see part one for more about that!
For those who eventually went to sleep, Sunday morning arrived an hour too early due to the daylight savings time change.
Throughout most of Sunday we discussed the open issues and planned ahead to the next steps. Work will continue on the Gen-II issues, and we’ll keep everyone apprised of the latest status through these updates.
A grab-bag of specific issues were discussed on Sunday morning as we went around the room and gave everyone five minutes to say what was on their mind. The comments and issues below are reported in no particular order or level of completeness...
  • One of the outputs of the Gen-II study will be a book that summarizes the effort, as well as the process along the way. Each participant should consider putting together a 10 page “final report” to facilitate the collection of information. Brian Enke, Tom Hill, and Michael Carroll will write and edit the book, with help from anyone else who is interested.
  • Each participant in the Gen-II study should promote the work within their technical communities and continue researching various open issues.
  • For Entry, Descent, and Landing (EDL), we need to find the “sweet spot” between maximum payloads to Mars, cost-efficiency, and flexibility, today and optimistically tomorrow. Perhaps there’s a perfect solution… perhaps not.
  • Navigation issues on Mars – does adequate satellite and repeater technology exist today?
  • We need a two-person rover on Mars with a range of 1000km before the main base build-up.
  • Perhaps the current 3 – 5 tonne EDL payload limit will increase the motivation for spreading out the mission and splitting it into phases (others agreed).
  • Lubricants must be manufactured on Mars.
  • Skepticism due to the early "androsite" result from MGS - the kieserite might not really be there? Or it might be a disguise for some other mineral? We need to know mineral concentrations!
  • Nitrogen balance in the aquaculture system remains an open question. We should determine what kind of bacteria strains we will be dealing with. We also need different ways of cooking fish, different spices, any way to break up the monotony of a fish a day.
  • Greenhouse reorganizations and light sensitivities remain open issues, but diversity in the growing area between protected/unprotected greenhouses might be a bigger issue.
  • Possibly inject 3 to 6 inches of water between the double greenhouse layer and circulate the water, plus inject it with an ethanol antifreeze? As a radiation protection measure, this might be overkill – and structurally difficult. Perhaps we only put radiation-resistant plants in the transparent part of the greenhouse?
  • The mass of biological building materials (wood?) and the area it takes to grow them might make that technology prohibitive.
  • Every square inch of the greenhouse is critical. Only the most important crops get to be grown inside the greenhouses.
Are we there yet?
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