Over the past year, we’ve considered what it will take to create a permanent human presence on Mars. We’ve evaluated ground transportation, oxygen and carbon dioxide cycles, water recycling, thermal management, and food production. But we’ve danced around what will make it all possible: energy. This edition we’ll examine several options available for operating our Red Planet base, then decide which makes sense to deploy.
First up is
fusion. This is the sexy power source. It’s the first that comes to mind by most futurists and planners for long-term human occupation.
Fusion combines the atomic nuclei of two isotopes of hydrogen: deuterium (one proton and one neutron) and tritium (one proton and two neutrons). The reaction creates one helium atom (two protons and two neutrons), one free neutron, plus energy. Lots of energy, and efficient. Just half a pound of fuel per year will provide 1 MW of clean, dependable power. A typical “starter” base will use about 40 kW, a mere 4% of such a reactor’s output.
Deuterium is relatively common. Shortly after the Big Bang, a quark-gluon plasma condensed into protons and neutrons, some of which then fused to form deuterium nuclei as the universe cooled. Most of it in existence today is believed to have been produced during this event. It can be found in any molecule that contains hydrogen, including water. Deuterium-containing water, known as heavy water, can be separated from regular water by distillation. Electrolyzing the heavy water yields deuterium and oxygen.
Tritium is less common. It’s mildly radioactive (it emits a weak beta particle) with a short half-life of 12 ½ years, making it quite rare in nature. But, it can be manufactured by bombarding lithium with neutrons. This is the process in nuclear fission breeder reactors. And the same will be true for fusion reactors, utilizing a thick bed of lithium-containing ceramic beads called a breeder blanket.
Unlike tritium, lithium is abundant. Here on Earth, lithium exists as a salt. Many commercially viable sources are either lithium brine aquifers, or deposits leftover from such geologic features. On Mars, subterranean brines will be likely sources for both deuterium in the water and lithium in the saline fraction.
But fusion has never been achieved for more than a few seconds. The technology is not mature enough to maintain a stable, reliable burn. The reactor itself must be miniaturized by orders of magnitude smaller than today’s behemoth experimental reactors to make transfer to Mars viable. I deem this unlikely until well after 2050, possibly even decades later.
Nuclear fission is a well-developed technology that has been miniaturized for space travel and exploration. NASA’s 10 kW Kilopower fission reactor uses uranium-235 to generate heat that is piped to an integrated Stirling electric generator by molten sodium. These compact devices can power nuclear electric ion propulsion drives in spacecraft. Or can serve as stand-alone power generation plants on the Moon or Red Planet.
An even smaller fission energy source is a radioisotope thermoelectric generator(RTG). Less powerful than a Kilopower generator, it’s a type of nuclear battery employing an array of thermocouples to convert the heat released by radioactive decay into electricity. Most Mars rovers employ RTGs.
Solar is another power source used on the Red Planet. Photovoltaic cells on Mars produce about half of the output they would on Earth. The maximum solar irradiance is about 590 W/m2 compared to about 1000 W/m2 at the Earth's surface. Therefore, it will require twice as many cells to generate a comparable output on Mars as here.
A 50 kW photovoltaic system on Earth needs around 100 5-foot by 3-foot panels. Roughly 200 panels would be required for the same output on the Red Planet. Shipping weight, less mounting hardware, would be 4 tons. That’s a lot of weight for a system that would be available for a fraction of each day, and not at all during an extended dust storm.
Scientists have evaluated the feasibility of
wind power on Mars. They studied a medium-sized Enercon E33 wind turbine with a rotor diameter of 33 m and a rated output of 330 kW. The turbine could operate at an average output of about 10 kW there.
Winds on the Red Planet are more reliable for longer durations, both day and night, than the sun. But some sort of battery backup would still be required to get through the inevitable outages. Delivering the bulky equipment will be difficult. The rotor diameter requires a minimum 16.5 m (55 ft!) tower. Add another 10 feet so no one walks into a spinning blade, plus three 16.5 m blades and the generator. Then add to that the bulk and mass of the batteries.
Combustion has been a mainstay energy source for humankind for millions of years. There is evidence that Australopithecus(recall the famous Lucy skeleton) used fire. But it’s not a good idea inside the confines of a Mars habitat without careful control of the oxygen feed, and the flue gasses. Outside, there’s no free atmospheric oxygen to sustain a reaction.
A variation would be an internal combustion engine using compressed oxygen. Two fuels are available on Mars: compressed hydrogen and compressed methane. Both fuels require energy to produce, making them advantageous for transportation uses, but impractical for base power.
I’ll add a hydrogen fuel cell electric vehicle here. But an HFCEV requires a small RTG to maintain a warm enough operating temperature
So, that’s the rundown of possible energy sources on the Red Planet. And the winner is: It depends on the application.
For vehicles, RTGs have been used to power the various Mars rovers. Earth-moving equipment will likely need an ICE or HFC power source. For large fixed facilities like habitats, greenhouses or industrial sites, 10 kW Kilopower units are designed for that very application. For smaller facilities such as weather stations or communications relays, solar arrays or RTGs should continue to be used.
My personal preference is nuclear fusion. But until the tech is matured and miniaturized, it would be a waste of valuable shipping capacity to deploy it to Mars. It won’t be practical within my lifetime, or that of my children. But my grandkids could help install a 1 MW unit to be shared by several bases. Or they’ll drill the Red Planet’s briny aquifers for lithium and deuterium, or work in the refineries to extract them. Or maybe they’ll pilot the spacecraft that instead deliver those fuels directly from Earth.
Until then,
Happy Reading,
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Want a deeper dive? Check out these sources.
https://www.iaea.org/newscenter/news/fusion-energy-future#:~:text=Deuterium%20can%20easily%20be%20extracted,distributed%20in%20the%20Earth's%20crust.https://www.nasa.gov/directorates/stmd/tech-demo-missions-program/kilopower-hmqzw/https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generatorhttps://physicsworld.com/a/wind-energy-could-power-human-habitations-on-mars/#:~:text=Hartwick%20says%20that%20they%20%E2%80%9Cwere,solar%20to%20boost%20power%20generation.
https://www.google.com/search?q=is+combustion+possible+on+Mars&sca_esv=76c8920d8a4a7859&sca_upv=1&sxsrf=ADLYWIK7MC07YQHyoSzvctYLDP_MK6hsjA%3A1721857504504&ei=4HWhZqC6Huvw0PEPvMmMqAU&ved=0ahUKEwigqqOH08CHAxVrODQIHbwkA1UQ4dUDCA8&uact=5&oq=is+combustion+possible+on+Mars&gs_lp=Egxnd3Mtd2l6LXNlcnAiHmlzIGNvbWJ1c3Rpb24gcG9zc2libGUgb24gTWFyczIFECEYoAEyBRAhGKABMgUQIRirAjIFECEYnwUyBRAhGJ8FMgUQIRifBTIFECEYnwVIhDZQAFisLnAAeAGQAQCYAXCgAcASqgEEMjguMrgBA8gBAPgBAZgCHqACoBPCAgoQIxiABBgnGIoFwgIEECMYJ8ICCxAAGIAEGJECGIoFwgIOEAAYgAQYsQMYgwEYigXCAgsQABiABBixAxiDAcICCBAuGIAEGLEDwgIKEAAYgAQYQxiKBcICCxAuGIAEGLEDGIMBwgIFEAAYgATCAgsQLhiABBjHARivAcICDRAuGIAEGEMY5QQYigXCAggQABiABBixA8ICBhAAGBYYHsICCBAAGBYYHhgPwgILEAAYgAQYhgMYigXCAggQABiiBBiJBcICCBAAGIAEGKIEmAMAkgcEMjcuM6AH3N0B&sclient=gws-wiz-serp
