Plasma reactors could create oxygen on Mars
science.org
science.org
Using plasmas is interesting for ISRU because they may work at Mars ambient atmospheric conditions. I'm quite surprised that this plasma reactor approach is more energy efficient than the solid electrolysis technique used by the MOXIE experiment.
Producing materials from other materials such as extracting oxygen from various compounmds is ultimately an energy problem. Better processes might reduce the ultimate cost by reducing the capital cost or reducing the running cost. For example: we can make hydrocarbons from the atmosphere. It's just uneconomic because of the energy cost.
The energy source itself presents issues. If you need a $50 billion fusion reactor that takes 20 years to build and a thousand people to maintain then that's a problem to bootstrap on Mars.
I personally believe that on Mars, much like on Earth, the future is solar. Solar has a lot of benefits on places like Mars. It's the only form of power generation that reduces electricity directly rather than boiling water and turning a turbine.
So mars still has the two big problems it always has had:
1. It's further from the Sun so solar is less effective. This just increases the cost of energy, ultimately. Of course, there'll occassionally be a months-long dust storm that'll stop you producing any power or just a shorter one that covers all your panels in dust; and
2. What are you going to do with this oxygen? You're going to be living underground because living above ground exposes you to radiation and the Martian surface itself is toxic (eg perchlorates). If you're living underground anyway, why are you living on Mars instead of the Moon?
Mars just makes zero sense to colonize.
ITER is a research facility, not a practical reactor. We have new (relatively) high temperature superconductors that are much better than what was state of the art when ITER was originally designed, meaning we ought to be able to build much smaller and cheaper reactors going forward once the basic technology is worked out. The MIT ARC and SPARC reactors are an example.
> If you're living underground anyway, why are you living on Mars instead of the Moon?
Mars has air that be used to manufacture rocket fuel. It has closer to Earth-standard gravity. The temperature swings are less dramatic. Water is more abundant. It's closer to the asteroid belt, which means it functions as the local gas station and resupply depot for asteroid mining. It has close to an Earth-normal day/night cycle. Basically, it's a much more hospitable environment for humans than the moon. The main thing the moon has going for it is that it's far quicker and easier to get there from Earth.
Later on that could be accomplished just by routing the exhaust down into the canyons, but early on that may have to go through greenhouses, which either vent above a certain pressure or aren't quite hermetically sealed.
While mars may have been geologically dynamic at one point, it either is drastically much less so now or pretty much dead. Terraforming by means of burning through the surface would have to be an ongoing thing process because not everything we’d burn would be beneficial for our understanding of life (us and the ecosystems we are used to on earth), but it would also be very hard to keep what we generate on Mars in an atmosphere. Could be wrong, though.
So the thermal decomposition of the rocks will require much more energy.
As you say, the thermal decomposition could be done directly with solar light, bypassing the conversion efficiency of the photovoltaic cells.
That brings the energy requirements to similar values. Which would be the more efficient process would depend on details, e.g. the type of photovoltaic cells, the exact composition of the rocks whose decomposition is attempted, the usefulness of the byproducts, e.g. reduced carbon or reduced metals, and so on.
When taking into account the byproducts, it is likely that both processes will be needed anyway.
The council of extraterrestrial life has acknowledged that.
For those wondering, the gravity, temperature, and air pressure in the cloud tops of Venus are all near Earth-normal. And, breathing air is buoyant.
Mars is a frozen, dry dump. There is really no value in sending live people there. They would take one trot around the lander and want to go home.
The moon, on the other hand, has many advantages:
1. shallow gravity well
2. only a couple days away
3. interactive radio
Since you'll need a spacesuit anyway on Mars, what's the point over the moon?
Day/night cycles near identical to Earth differing by less than an hour (2 week long day/nights on moon).
A land surface area near identical to Earth's land area, which means room for vast expansion. (moon is a bit more than 2x Russia)
Somewhat more tolerable gravity at 0.38g compared to .17g on the moon.
Vastly more tolerable temperature ranges. A day on the equator in summer can get up to around 70 degrees F, though nights hit -100 F. The large difference owing to no atmosphere. The moon ranges from nearly absolute zero at night, to greater than boiling during the day.
And many more. These are just a handful off the top of my head.
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And some would consider the distance to be a feature, not a bug. It creates a necessity for a large degree of self sustainability which is ultimately a prerequisite to becoming a multiplanetary species. On the Moon, self sustainability not only more challenging, but ultimately not really necessary given it's just a stone's throw away from a resupply. And necessity really is the mother of invention.
Ultimately I also don't even view Mars as a goal (though it may be able to over millennia developed into an amazing place, and I would be the first to sign on for a mission to such), so much as a stepping stone. By the time the first human settlement is established on Mars, we should be looking outward from there as well. Titan being a possible next destination.
If fuel and machinery can be made on the moon, with its lower gravity well, it becomes far more practical to build big ships to go to Mars and elsewhere.
But you will need that sulfuric acid for the hydrogen it carries. Carbon from CO2 for structural members, hydrocarbon for plastics and fabric for gas bags, oxygen to breathe. There is thin gaseous silicides, in case you need any silicon.
It will be hard to keep the concentration of CO2 in the breathing air thin enough not to make everyone stupid, with so much of it outside.
But there is a surprising quantity of metal compound gases in the atmosphere.
I've been wondering about the feasibility of self-replicating floating comet factories that make dry ice comets that could be launched to mars. You could even wrap them in some sort of carbon based exterior to prevent them from boiling off too much in transit.
The composition of Mars' atmosphere is less important then getting the pressure right - at 1 atmosphere, humans don't need suits just respirators, and Earth-microbes will be more then happy to normalize things to suit them (they did it here, after all).
For Venus the big problem is water: Venus is dry. The reason it's in run-away greenhouse is because all that CO2 just will not precipitate into carbonate minerals, which to do so needs water. Again: something comets have plenty of.
The difference between the two in suitability though is the tidal lock: Mars has a day-night cycle. Venus has a day-night cycle but it's 116 Earth-days long - half the planet, if you got the atmosphere under control, would be in a freezing night for 3 and half months. You could settle it, but life would only really survive at the polls. While we can process a planetary atmosphere with plausible near-future technology and local resources, there's no known way we could "spin up" Venus (ironically a fully-tidally locked planet would have much more usable surface area as an oculus-world).
Shipping in enough hydrogen from (say) Neptune might be possible in principle using billions of automated, self-reproducing nuclear powered spacecraft.
If its atmosphere could be precipitated and the carbon freed of oxygen and somehow permanently protected from runaway combustion, the planet's low (2.64°) axial tilt and solar proximity might make a polar existence possible. But the overwhelming excess of oxygen would need to be removed or bound up in water. (The carbon might then be safely kept under water. Or, be crystallized out as diamond, which is hard to ignite.)
Quadrillions of aluminum foil balloons full of nitrogen bobbing in the stratosphere might suffice to bring temperature down.
Perhaps surprisingly, the present 3.5% of its atmosphere that is nitrogen is more than Earth's total.
As noted elsewhere, Venus's magnetic field is not much like Earth's, although it stretches almost to Earth's orbit, and might have crossed it in the past. (Such events might account for Venus's baleful reputation in to the oldest myths.)
Importing enough hydrogen to take up excess released oxygen will be difficult.
On earth we have a magnetosphere that protects our atmosphere from erosion from the deluge the sun gives us (hello Auroras!) but Mars doesn't have that. It's size is an issue too plus it's distance and orbit around the sun now. It didn't used to be so barren, it had massive lakes and oceans and possibly life once upon a time. To terraform it now would take a level of engineering that we don't have, but could, if we manage to not nullify ourselves in the next 200 years.
Titan can. But its surface gravity is less than a seventh of Earth's. It seems unlikely people can live on Titan or the Moon for long without fatal loss of skeletal tone. (Mars might be possible, but why bother?)
https://en.wikipedia.org/wiki/Surface_gravity
Anyways, Mars is an outlier with respect to the "about 1G" crowd, but it's almost identical to Mercury. 0.379g vs 0.377g respectively.
Jupiter is a true outlier at 2.528g.
Unfortunately nobody wants to live on Venus, in part because of that much denser atmosphere, so there's not much interest in making oxygen there.
If your goal is to build an exotic resort for billionaires go to Venus. If you're trying to ensure the survival of humanity in the event of a planet-scale catastrophe go to Mars.
Any attempted Mars colony would die out not long after the last shipment, as materials necessary to its continued survival remain unobtainable there.
Furthermore, Starship is anyway wholly inadequate to establish a continued presence on Mars. If it works fully l as well as promised, it might suffice to maintain a Lunar outpost.
Anyone who hopes to establish a sustainable presence off-Earth must look to O'Neill Cans.
Much like the moon missions, the side-effect benefits that it encourages will likely end up making such a mission worthwhile for the tech alone.
I don't understand your criticism of starship though, would you clarify why you think it's not suitable?
All the choices after that become very unpleasant, of questions about who gets to continue living. The supportable number declines inexorably to zero.
For solar power, you need storage for the long night. A heavy weight on a cable could be played out at night to spin a generator, and then wound back up in the daytime.
A nuke power plant, if you would rather, could be as simple as a naked pile hung inside a big fabric tube with a wind turbine at the top. No need for shielding, cooling, or containment.
https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmo...
The article is unclear whether this is 1 or 2 Tesla at a point, or if what's needed is a field that's 1 or 2 Tesla over a large area, which would be a lot more than "an MRI machine's worth". Interesting idea anyways.
Also suspiciously absent is any mention of how long this kind of change would be expected to take... I would be legitimately surprised if it'd take less than 20 years though, which is somewhat implied by the paragraphs that follow:
>"A greatly enhanced Martian atmosphere, in both pressure and temperature, that would be enough to allow significant surface liquid water would also have a number of benefits for science and human exploration in the 2040s and beyond," ...
A lot of it does seem to be very carefully avoiding making any clear statements or connections between critical bits of info though. There's room for "that wasn't claimed" arguments, but it's certainly standing very close to some lines...
I don't have the technical expertise to estimate if such a project would require mere billions, or planetary sized piles of money.
I'll point out you couldn't just park it at L1. If it's deflecting the solar wind, then it's acting as a solar sail. You would need active propulsion to keep it on station.
https://solarsystem.nasa.gov/resources/754/what-is-a-lagrang....
Assuming the solar wind is constant, you could presumably park it somewhere other than L1. That's certainly not a valid assumption, though, so propulsion is going to be necessary.
Superconductors stop superconducting at very high B field strengths, which limits them to carrying less than an infinite current.
The main issue after simply having oxygen is that the martian atmosphere has so much CO2 and so little everything else. Considering that subsurface temperatures can get low enough to sublimate CO2 into dry ice, you could potentially (and I say potentially because this isn't my specialty by any means) build an air production loop that uses relatively little power other than to drive the plasma reactor itself and a thermal pump to bring cold fluid to the surface to chill the oxygenated air so that the CO2 sublimates out. Of course here you could also just use energy to chill the gas via a compression chiller or make some tradeoff between the two. This process would move you along the following steps:
Standard Atmosphere with 95% CO2, 2.5% N2, and 2.5% trace elements (mostly argon, also a very small amount of O2, and a tiny amount of CO).
After Plasma Reactor: 65% CO2, 30% O2, 2.5% N2, and 2.5% trace elements.
After Sublimation: Lower volume of gas with 85% O2, ~7% N2, 5.5% argon (from trace elements), and the rest of the trace elements. And the CO2 is now dry ice.
Then it's just a matter of diluting the "purified air" with nitrogen or other inert gasses, adjusting the pressure, and preventing buildup of any nasties in the trace elements (such as the carbon monoxide). Now you should have breathable, earth-like atmosphere for suits and cabins.
This is mainly based on my knowledge of processes we use on earth already for extracting stuff from the air so caveat that I could be missing important details.
Of course “Corey” (The Expanse) are probably right that each colony will develop her own personality, and it will be difficult to abandon any of them. The cultural trauma of such an event could be profound.
If one were to make a hole like the one described in the video, I wonder how much that would affect the atmospheric pressure on the rest of Mars?
What many people forget is that the martian atmosphere has massive total amounts of gaseous oxygen, even if it makes just 0.16% of a very thin atmosphere, if you could capture it and store it would be more than enough for centuries of human colonization. NASA is investigating this very scenario with some low energy adsorption methods, that promise to be very energy efficient: https://www.reddit.com/r/spacex/comments/vhnuqa/nasa_funding...
This could enable, for example, the creation of suits that extract unlimited oxygen from the surrounding atmosphere as long as they have electric power - say a few solar panels.
So the greenhouse is going to be a better option, though having backup plans is good.
Finding evidence of previous life on mars would make it all worth it.
People are so proud of being able to get there at all that they forget to consider whether there is anything there to get to.
I wonder when will the first cigarette be smoked on Mars, and the first butt dropped on the ground.
CO typically only lasts for a few months in the atmosphere, but only because CO molecules react with oxygen, forming CO2.
So I think no, this could not be used to sequester CO2 from the atmosphere.
Apparently there are also bacteria that consume perchlorates.
C O is deadly when inhaled
https://bookshop.org/books/we-can-remember-it-for-you-wholes...
Fusion power doesn't need the kind of incremental advances and smart marketing that Musk's companies have benefitted from, it needs huge fundamental advances in science and engineering.
That said, by the time anyone actually tries to establish any kind of base on Mars, we may well have figured fusion (my money is still on ITER's follow-ups, the DEMO plants, being the first to actually do anything, in 2050 at the earliest). Musk's "plans" for Mars are just part of his pretty smart marketing / outright lying to bolster his companies.
It is systems engineering - take the available science and engineering and combine into an actually working thing. That is exactly what we need with fusion today.
This doesn’t describe the present situation. For example, high-temperature superconducting magnets open design space which simply didn’t exist a decade or two ago.
Then, even if all current plans go right, current designs have no realistic hopes of being economical. Plants will cost extreme amounts of money, as they require state of the art technology at every level, and the irradiation caused by the fusion reaction will turn all materials in close contact with the fusion core brittle (reactor vessel, support structure, possibly even magnets) in a few years, requiring a complete replacement.
Not to mention, an accident can easily be catastrophic for the entire reactor, making the whole thing an extremely risky endeavor. Even the environmental risk is large, even if not nearly as bad as fission - if such an explosion occurs, it will send radioactive materials (concrete, steel, cooling agents), plus radioactive tritium, all around the plant, requiring expensive cleanup and risking the future of the whole plant.
An alternative is to gather the reactor fuel on Mars, but that sounds like a difficult undertaking.
I think the expectation is that the energy needed to make methane on Mars will be provided by a lot of solar panels.
(I would be curious to know how the math works out. For instance, if you send a Starship fully loaded with solar panels to Mars and spread them out on the ground, how long will it take those solar panels to gather enough energy to make enough methane to return the rocket to Earth? Is it one year? 10 years? 100 years?)
https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
The risks weren't purely theoretical either. They had one nuclear-powered satellite that re-entered over Canada.
I suppose one way to mitigate the risk is to use the same kind of "emergency escape" systems that humans use during rocket launches. I.e. if the rocket fails to achieve orbit, a capsule is ejected and floats down on parachutes. I wonder if that sort of thing is already done with RTG launches?
My bet is on nuclear vs solar as the nuclear is the next rocket engine type after chemical and will loose the dependency on launch windows and shorten the trip time.
Nuclear rocket engines are tricky. Nuclear reactors don't actually work very well in space because there isn't any convenient way to get rid of the excess heat. A vacuum is a very good insulator, so usually your only option is just to radiate it away as infrared light.
With a rocket there's another option which is to transfer all the heat to the reaction mass you're expelling out the back of the ship. That sounds like a hard engineering problem though.
Using a reactor on the Mars surface is a lot more straightforward because you can use the local air and ground to transfer heat. And since Mars is so cold, you might even get better steam generator efficiency there than on Earth, where the ambient temperatures are higher.
One of the hopes with fusion is that if it pans out it might be reasonable to send a fusion reactor to Mars since you wouldn't need to send radioactive fuel rods. In fact, maybe the first practical fusion reactors will be used on Mars before they're used in more than a demonstrative capacity on Earth because they fit a very specific need, there are barriers to using the alternatives, and cost per kw/h isn't the most important constraint.
The US did build a nuclear powered ramjet engine and test it. This isn't an insurmountable hurdle, it's an achieved one. The design they used of course has lots of good reasons we should not use it on Earth (namely, the reactor would activate the air, meaning it spews a plume of oxygen and nitrogen isotopes) but it does work.
You can solve the radionucleotide problem by running it off hydrogen instead, which doesn't activate in any meaningful quantity.
Basically, not only do we have the ability, we had it in 1961.
Somewhere around a year.
A Starship, refuelled in Earth orbit, intends to carry 100 tons to Mars [0] using 1200 tons of propellant [1] with an oxidizer/fuel ratio of 78:22 [1], so 265 tons of methane.
Spacex's numbers are likely measured from low Earth orbit to low Mars orbit and assuming aerobraking on the way down. According to [2] that takes 5.8 km/s delta-v, but it's an additional 3.8 km/s to travel from the Mars surface. That's 65% extra, meaning we will need e^0.65 as much fuel because of [3], which is 1.9x, so 500 tons of methane.
So the first answer is, it can't be done by refueling a Starship final stage alone - you'd need a booster, or (simpler) reduce payload by half. I'll assume instead we divided the load between two rockets coming back.
Methane has a specific energy of 55MJ/kg, [4] so we need 28 TJ of energy to fill the tank. That's 8 GWh.
Mars receives about 50% as much sunlight as Earth [5]
Spacefaring solar panels weigh 2kg/sqm and produce 350W/sqm in Earth orbit. [6]. Terrestrial solar panels are cheaper to produce, but heavier. That's baseplate capacity, so make it 1/3 of that to average over day and night, and halve it again for running at Mars light levels, giving 60W/sqm or 30W/kg.
100 tons of that is 3 MW.
Typical conversion efficiency for power-to-methane is 50%. [7]. This is done via hydrogen and requires carbon dioxide, which is abundant in the Mars atmosphere, and water, which is not, but is hopefully available in the quantities we require. So our solar plant produces 1.5MW of methane. I'm going to assume we get our oxygen for free as a by-product without any loss of efficiency, which seems plausible to me but not well documented.
8 GWh/1.5 MW is 5,300 hours or 225 days (either type) or about 8 earth months.
I haven't allowed for the mass cost of the infrastructure for methane refining, or degradation of solar panels in the Mars dust. So all this should be a considered a lower bound for your answer.
[0] https://www.spacex.com/human-spaceflight/mars/
[1] https://www.wevolver.com/specs/spacexs-starship-sn24-bn7
[2] https://i.imgur.com/SqdzxzF.png
[3] https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
[4] https://en.wikipedia.org/wiki/Energy_density
[5] https://www.quora.com/How-bright-is-sunlight-on-Mars
[6] https://www.spectrolab.com/DataSheets/Panel/panels.pdf
[7] https://www.sciencedirect.com/science/article/pii/S030626191...
Before we sent astronauts to the moon successfully we discovered the hard way that astronauts are likely to die if they breathe pure O2.
https://en.wikipedia.org/wiki/Apollo_1
Future Apollo missions mitigated the danger of fires by being really careful about the materials in use, but that's not a good answer for long term missions, particularly if the astronauts are going to conduct industrial activities such as in-situ resource utilization.
If you want to make breathing gas on Mars, O2 covers 20% of it, the rest of it is going to be an inert gas like Nitrogen, Argon, Helium or SF6.
Of course every method of producing O2 in space works by separating O from something else and the "something else" is likely to be useful, such as H2, C, Al, etc.
Sure, the breathing gas for a crewed mission or habitat would need to include an inert gas as well as oxygen. But oxygen is consumed during respiration and the inert gas isn't, so oxygen will be needed in much larger quantities, so in-situ production is a much more pressing problem.
The real thing you’ll need O2 for is an oxidizer for fuel but of course you need to make fuel too.
If you are interested in making anything interesting such as large plastic sails or small biospheres nitrogen is the big missing piece of the puzzle right now in the moon, mars and asteroids.
It’s literally exactly as difficult as cracking out from the air, because breath is in fact made from air.
seems like the kind of thing where there is a bunch of engineering that could be productively done.
https://www.popsci.com/why-did-nasa-still-use-pure-oxygen-af...