Do you know why space is so expensive? There’s no Amazon Prime free shipping.
Engineers express that fact as delta-V, change in velocity, and it costs a lot to change the velocity of every kilogram of cargo in the vacuum of space. Even considering a massive economic efficiency boost through reusable rockets, sending any material object beyond Earth and landing it safely on the moon or Mars will cost about the same as the value of that item’s weight in gold.
Moving mass across space from one celestial body to another is hard. It won’t get much easier as on-the-horizon rocket technology advances.
It makes sense to avoid doing it as much as possible. Nevertheless, space enthusiasts often imagine moon bases and Mars colonies receiving shipments of supplies from Earth as a matter of necessity. Food, clothing, construction materials, complex equipment—regardless of the cost, won’t all that have to be shipped across space?
Fortunately, no. At least not for Mars. And I think Mars is where the action will be, for this reason and plenty of others.
Everything Mars colonists need can be created on site, on Mars, from “locally sourced” materials. Complex equipment, even spacesuits and medical gear and labor-saving robots, can be “printed” (additive manufacturing) from simple feedstock, quickly and with little human guidance.
I believe this is a key gateway scenario for the 21st century and our current stage in human history—the expansion of human civilization across the solar system and then the stars.
This is nothing like the space-borne civilizations envisioned in contemporary science fiction, which are usually enabled by a freight-based economy. Freighters haul finished goods from Earth and raw materials from asteroid mines. Maybe there is a 22,236 mile high orbital tower stretching up from the Earth’s equator to help move the freight. There are smugglers, and of course space pirates. Space is imagined to be like an ocean plied with vessels hauling necessary and valuable cargoes—this familiar and plausible freight system often playing a central role in the plot.
We Won’t Need to Ship Building Materials
If we don’t haul living quarters or habitats from Earth, what are the people on Mars going to use for houses and workshops? If they’re staying long term, we can’t expect them to live inside the tiny spacecraft that brought them there. So surely we need to ship them building materials.
We don’t—it would be too expensive anyhow. Mars settlers can build large, comfortable, safe quarters (even privately owned houses) that are shielded from surface radiation using bricks, one of the most common building materials over the last five thousand years.
The fine dust that makes up most of the top 10 cm of Mars will likely make excellent bricks due to the heavy concentrations of calcium and gypsum. Mix with water, possibly add plastic fibers for binding, put into molds, dry at 200 C (recover the water), then bake at 300 – 900 C using the waste heat of a small nuclear reactor. This yields strong, durable bricks—and most of the tedious process can be automated with robots. The process should be no more complex than having a Roomba vacuum your carpet.
But wait . . . we’re going to pressurize buildings on Mars, right? Yes, to about five pounds per square inch. Won’t our brick buildings explode?
Yes, they would—because brick has little strength in tension. The idea is to keep our brick houses under compression. This can be done using an old Roman invention: arches.
After our bots dig trenches, we line the floors and sides with brick and erect arches across the tops, using Mars dust and water as mortar. Before the inside is pressurized, cover the arches with two or three meters of Mars regolith (the sandy mix of dust and pebbles that covers Mars). This not only keeps the arches in compression after the interior is pressurized, it shields the inhabitants from solar and cosmic ionizing radiation too, cutting total radiation exposure.
This is how we can make roomy places to live and work, without importing massive inflatable habitats from Earth.
Bricks? Air pressure? Those bricks aren’t airtight. What about leakage?
They will leak. We’ll need to coat the inside with plastic, which fortunately will be very cheap on Mars.
The Secret of the Future: Plastic
It’s not just a line from the film The Graduate. The easy availability of CHON (carbon, hydrogen, oxygen, and nitrogen) all over Mars will make plastics and fertilizers and many other useful products cheap and abundant, without freighting anything from Earth except for compact reaction containers that can also be reproduced later with on-site materials.
A vast array of useful organic products can be created from simple combinations of chemical elements, most of them CHON. These elements are on Mars in available form, ready to be used as raw materials for well-established processes that are already widely used in factories on Earth.
The Mars atmosphere is 95-percent carbon dioxide (CO2). In 2008 we discovered that Mars harbors far more water (as ice and permafrost) than previously imagined, almost across the entire planet. Water is H2O, which can be electrolyzed to release the hydrogen and the oxygen as separate gasses.
Nitrogen is available on Mars too, and it will be needed to manufacture both plastics and fertilizers. In 2015 NASA’s Curiosity rover discovered nitrous oxide in the Mars regolith, the product of nitrates broken down by heating. Nitrates are molecules that contain nitrogen in forms that can be used by living organisms. We can harvest free nitrogen from the Mars surface grit as a raw material.
Aerospace engineer Robert Zubrin’s firm Pioneer Astronautics has conducted tests on manufacturing useful fuels, plastics, and other products using materials available on Mars. Their tests used compact equipment with modest energy requirements on the order of what would be available at an early Mars settlement.
We have CHON on Mars, a lot of it. What can we do with it?
Take hydrogen that’s been electrolyzed from water. Combine it with CO2 (Mars atmosphere) and heat it.
Hydrogen + carbon dioxide + heat = water + carbon monoxide
Carbon monoxide (CO) is toxic, so what good is it? It’s actually a useful ingredient in a lot of organic chemistry reactions.
We use the carbon monoxide as an ingredient in this reaction:
Carbon monoxide + hydrogen = C2H4 + water
C2H4 is an organic compound called ethylene, a simple alkene that makes good fuel, plus it’s a valuable ingredient in making plastics, lubricants, and a wide range of other petrochemical products.
The second reaction is exothermic—it releases heat—and that waste heat can be used to drive the first reaction. Electricity is needed only for gas compression and to get the cycle started.
Ethylene is a gas, but it has a high boiling point, so it will be a liquid if we compress it to several atmospheres and store it outside in Mars ambient temperatures. Not only is it a good fuel for Mars rovers and trucks and other portable equipment, it can be converted to plastic by reacting it with different catalysts, a well-understood process that’s been used for decades.
It’s how your plastic trash bags were made.
We can convert ethylene to polyethylene (the most common kind of plastic) with various densities. Not only can we use this stuff to line our brick houses so they are airtight, we can use it as feedstock for 3-D printers and create almost anything we need. Ultra High Molecular Weight polyethylene makes good machine parts, tools, bearings, gears, even ultra-tough fibers that can be woven into inflatable greenhouse domes.
Less dense polyethylene can be “printed” into furniture, utensils, electrical insulators, equipment casings, synthetic fabrics, most anything you can find on the shelves of your local Target.
We can do this on the moon too, right?
We cannot. Our CHON ingredients aren’t available on the moon in forms we can use—oxygen, for example, is tightly bound with silicon and other elements that would require a lot of electricity to reduce. Water may be available in extremely cold deposits deep within craters near the moon’s north and south poles. It would require considerable effort and power to locate and liquify lunar ice, and if you did, you would still lack carbon and nitrogen. Those elements are so rare on the moon that plastic manufacture is impractical. A humble plastic spoon would cost so much to freight to the lunar surface it would be worth its weight in gold.
We’re Not Going to Make Everything Out of Plastic, Right?
Fortunately, no. The Mars regolith is rich with useful compounds and elements that can be obtained in useful forms with well-know processes that require modest amounts of electricity and equipment. This will provide our 3D printers with a wide variety of feedstock, increasing the range of equipment that can be printed.
Mars regolith is about 40-percent sand by weight, and just like Earth sand, we can make it into glass. The glass would not be optically pure because it would have a lot of iron oxide (17-percent of the regolith by weight) but that’s a good thing, because we can react hot Mars glass with carbon monoxide to get carbon dioxide and iron, which we can separate with magnets.
Mars has plenty of iron and other metals in obtainable form. Made into wires or pellets, it’s 3D printer feedstock. The printers of the 2030s and beyond will be able to make objects from a mixture of materials—plastic, glass, metals—as one piece, as long as we supply the feedstock.
Thanks to the Curiosity rover, we know that Mars regolith also contains other useful materials, and there are deposits of copper, zinc, nickel, plus metalloids and rare earths.
We can print the equivalent of an iPhone or better if we want (using the 3D printers of the mid-21st century) but surely we can’t print food. Does that mean we have to haul food from Earth? We can have space freighters and smugglers and pirates after all?
Growing Food on Mars
At a minimum, CHON can be reacted into simple carbohydrates that will keep humans alive (their long-term health is another matter). But we won’t need to. The physical characteristics and resources of Mars allow us to grow food using sunlight.
There is sunlight on the moon too, and in space itself, but the sunlight there is not useful for growing food. Without an impractically thick covering of ten centimeters of solid glass shielding, plants in space or on the moon would be killed by intense ultra-violet radiation and by the radiation released by solar flares. On the surface of Mars, the atmosphere (thin as it is) attenuates both the UV radiation and the solar flares so that a greenhouse needs only a thin plastic cover to hold in air.
Mars is the only place in the solar system besides Earth where we can grow food with sunlight. By coincidence, the length of a Mars day is only three percent longer than an Earth day. Plants that evolved on Earth can adopt to the 24 hour 39 minute length of the Martian day—but on the moon, one day is 28 Earth days (14 days of light followed by 14 days of darkness) and that is well outside the range where plants can adopt.
Plants cannot grow in the thin Mars atmosphere, so we will need to enclose them under a pressurized canopy or structure of some kind, made from plastic or glass parts 3D printed from feedstock manufactured from native Mars material. Because Mars is further from the sun than Earth, the sunlight is only 43-percent as intense. This alone should not prevent growth, as most plants can grow in this light level, but we can compensate by greatly increasing the percentage of carbon dioxide in the greenhouse air, making the photosynthesis as efficient as on Earth.
Ammonia for artificial fertilizer can be synthesized by reacting nitrogen and hydrogen directly.
Why Does All this Matter?
Given the wide variety of resources available on Mars, plus the Earth-length days, we’ll be able to combine 20th century chemical engineering with 21st century robotics and 3-D printing to establish independent settlements early on—I suspect almost immediately.
This is a game changer because it offers a means and a reason for humans to make the journey without waiting for a chance to be selected for a large and expensive government space program.
History shows that as soon as technological advances make it possible for small groups to fund their own one-way journey to a new frontier, they will do so. All that’s needed is a reasonable chance of autonomous survival. The prize is freedom from the constraints and prejudices of the Old World—history also shows that humans will bear many dangers and privations in exchange for the chance to live a free and independent life in a small, self-governing community.
SpaceX and Blue Origin are developing economical reusable launch systems capable of throwing one hundred ton-plus payloads toward Mars. In the near future the price may be low enough so that companies can sell launch services and Mars settlement equipment as a package affordable to middle class individuals and families willing to liquidate their assets and strike out for a New World. People in high school and college today can explore the mountains and valleys of Mars well before they are middle-aged, and without having to compete for a tiny number of slots available to professional astronauts.
We’re on the cusp of a new era of innovation and exploration.