Martian air breathing engine

Antius · 2014-12-03 06:47:38

NB: This discussion started under the ‘New idea for Mechanical Counter Pressure suit’ thread. I have started a new thread to avoid corrupting the original thread intent, which was to discuss pressure suits.

The Martian atmosphere is predominantly CO2, but significant trace gases exist. An average composition is provided below. The actual composition varies depending upon altitude, latitude and time of year.

Atmosphere of Mars.
Chemical species Mole fraction[1]
Carbon dioxide 96.0%
Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%
http://en.wikipedia.org/wiki/Atmosphere_of_Mars

Two of the most significant minor constituents are CO and O2. These are produced by radiolysis of the Martian atmosphere, predominantly due to solar UV radiation. The two gases are destroyed by free radical reactions involving hydrogen ions. This maintains the concentration of both gases in low equilibrium.

Carbon monoxide is a fuel gas and O2 is an oxidiser. The possibility exists to draw useful power from these minor gases, by compressing Martian air and burning it within a gas turbine. This is obviously complicated by the low concentrations at which these gases exist on Mars. However, the average temperatures on Mars (220K) are far beneath the CO2 critical temperature of 308K and are close to its triple point, as indicated by the phase diagram for CO2. The CO2 content of Martian air can therefore be liquefied with very little compressor work, by compressing to 700KPa (7bar).

http://www.chemistry-blog.com/wp-conten … ramco2.png

The remaining gas has a mole fraction of 1.39% CO and 3.6% O2. The CO concentrations are far beneath its ordinary flammable limits in air and the adiabatic flame temperature of CO at such a low O2 concentration would appear to be too low to allow free burning at any pressure. The gas may however be combustible at high temperatures and pressures existing in a high compression ratio diesel engine or gas turbine. The required temperature of the reaction can be reduced through the use of metallic catalysts. The energy required to compress and liquefy the CO2 can be partially recovered by injecting the CO2 into a regenerator, prior to injecting it into the exhaust.

A cycle analysis is needed to determine whether this concept is capable of generating net power. If so, it may provide a useful power source for Mars Direct and early Martian bases. The total energy content of CO in the Martian atmosphere is 28,000TWh. Assuming a natural half-life of ~100 years, this would appear to permit several GW of sustained power generation to be raised in this way before CO atmospheric concentrations were substantially drawn down.

Antius · 2014-12-03 14:32:58

I've made a few back of the envelope calcs. The results are not too promising and they limit the operating cycles that could be employed.

After removal of the CO2, the remaining 'air' is 1.2% CO and 3.6% O2 by weight. Argon is 58%. N2 makes up the bulk. The heat capacity of the mixture is 0.723KJ/K. Complete combustion of the CO yields 115.9KJ of heat per kg of air. Hence, the maximum temperature rise of the gas from combustion is 160K.

Since the autoignition temperature of CO is 880K, the gas cannot be burned in a normal compression ignition engine. Spark ignition would also appear to be unworkable, as the heat capacity of the inert gas is too high to allow sustained combustion.

The most promising option would appear to be to pass the gas mixture through a catalyst. On Earth, catalytic converters use palladium coated aluminium oxide to combust any residual CO in a car exhaust. A similar principle could be used in this application, with the gas passing through a porous block made from sintered Pd coated Aluminium oxide spheres. Liquid CO2 would be sprayed into the exhaust, thereby achieving full re-expansion and driving the compressor.

The low energy content of the fuel, the low pressure ratio of the engine and the generally low temperatures achieved, would limit the engine efficiency and reduce power density. So this is unlikely to be a good candidate for vehicle engine.

Terraformer · 2014-12-03 16:31:58

What about the use of membranes to extract the CO and O2? If it takes less energy per kilogram produced to extract them from the atmosphere than it does to split CO2, then even if it takes energy, it might be useful as an in-situ fuel source.

SpaceNut · 2014-12-03 18:52:26

I have been here to long now and remember another topic discussion which imparts the same thoughts from long ago.

Air breathing engines on Mars

That said the engines fuels depend on the application whether they are surface bound, in the air or in orbital use.

Last edited by SpaceNut (2014-12-03 19:00:53)

Impaler · 2014-12-03 22:15:17

I'd be very doubtful that the CO and O2 could be filtered from the atmosphere for less energy then simply cracking the bulk CO2. Their are fundamental thermodynamic limits to separation of gas and they are proportional how rarefied the desired gas is in the source gas. A device capable of the gas separation your looking for would be an example of Maxwell's Daemon.

Also their seems to be a considerable excess of O2 vs what would be needed to fully oxidize the CO portion of the atmosphere by about an order of 6, so having your own fuel and trying to burn it with the latent O2 seems to give much better power density to the engine, if the latent CO in the air burns too that's extra power but it's not the main fuel.

A jet engine operating in such a lean manor in which fuel and oxidizer are tiny traces of the total air mixture probably requires the engine to have inconceivable compression and or size or for the internal friction losses to be inconceivably low. Generally very dispersed energy takes a larger and larger machine to gather and yields a lower and lower power to weight ratio. Maybe the power to weight is so low it can't fly and you just get some kind of big stationary generator taking in the atmosphere in this way and spinning an output shaft, it would have the advantage of not being sun-light dependent like solar and would presumably be more powerful the denser the air is so best in the Norther basins.

Tom Kalbfus · 2014-12-04 00:06:49

How about a nuclear reactor simply superheating the Martian atmosphere and using it for reaction mass? That could be quite handy for getting around on the planet's surface, and if the reactor ever approached the end of its operational lifetime, one could send it on a one way journey to one of the Martian poles.

Antius · 2014-12-04 06:32:45

Impaler wrote:

I'd be very doubtful that the CO and O2 could be filtered from the atmosphere for less energy then simply cracking the bulk CO2. Their are fundamental thermodynamic limits to separation of gas and they are proportional how rarefied the desired gas is in the source gas. A device capable of the gas separation your looking for would be an example of Maxwell's Daemon.
Also their seems to be a considerable excess of O2 vs what would be needed to fully oxidize the CO portion of the atmosphere by about an order of 6, so having your own fuel and trying to burn it with the latent O2 seems to give much better power density to the engine, if the latent CO in the air burns too that's extra power but it's not the main fuel.
A jet engine operating in such a lean manor in which fuel and oxidizer are tiny traces of the total air mixture probably requires the engine to have inconceivable compression and or size or for the internal friction losses to be inconceivably low. Generally very dispersed energy takes a larger and larger machine to gather and yields a lower and lower power to weight ratio. Maybe the power to weight is so low it can't fly and you just get some kind of big stationary generator taking in the atmosphere in this way and spinning an output shaft, it would have the advantage of not being sun-light dependent like solar and would presumably be more powerful the denser the air is so best in the Norther basins.

I would certainly agree that this cycle only appears workable as a power station. And it is only workable at all if the energy needed to compress and liquefy the CO2 is close to zero. Since most of the equipment must come from Earth, would the cycle compete with an S-CO2 gas cooled fast reactor when weight budgets are taken into account? I think its doubtful.

I have done a little background reading. It would appear that pd/pt catalysts need to reach a temperature of 250C before they are able catalyse CO oxidation at a significant rate. Try to lower that temperature significantly and the surface area of the catalyst bed increases exponentially.

As we are assuming an inlet temperature of -60C and a maximum temperature rise from complete combustion of 160C, this leaves us with a bit of a problem. Some foreseeable options are:

1) Use a centrifuge to remove most of the argon. It is significantly denser than the other gases at comparable temperatures, so centrifugal enrichment may be workable at an acceptable energy cost. As it represents about 53% of the mass and 40% of the heat capacity of the gas, removing it might just allow the gas to combust at 250C when passed over a catalyst;

(2) Add an additional fuel to top up the energy content and burn with the residual O2. Not a desirable option, as the combustion temperatures are low, which limits efficiency. Since making the fuel would also tend to liberate and oxidiser, it may be better to burn both in a more power dense, high temperature engine.

(3) Preheat the air in some other way to ~100C prior to it entering the catalyst bed. Solar heat or an RTG could be used in a hybrid cycle. This dilutes the benefits of the cycle, but allows it to double the gain of a low temperature solar thermal collector and turns a low quality heat source into a electrical generator. Overall efficiency might be 25%.

(4) Use some other means to enrich the CO (membranes?) burning it with the oxygen at stoichiometric ratios. This would be enough to push combustion temps above 250C and since CO is the smallest molecule, it could be made to work. But we are adding complexity and cost to the cycle.

(5) Some combination of the above, i.e. removing part of the argon, preheating the air using stored solar / geothermal heat and adding a small amount of hydrogen to accelerate the reaction.

RGClark · 2014-12-04 08:42:54

It is likely to get high power density as a rocket you would want to liquefy the fuel and oxidizer anyway, so you might want to find the temperature and pressure to liquify all of CO2, CO, O2, and N2. Then use a centrifuge to separate them.
For an air-breather you don't normally need to liquidfy the air but still it might be doable on the fly.
Also, for rocket or air-breather you want the fuel and oxidizer delivered at high pressure so maybe the cenrifuge and turbopumps or compressors can be done by the same device.

Bob Clark

Antius · 2014-12-04 09:40:31

Eureka. I foolishly missed a sixth option which provides a much more elegant and simple solution to the problem. This is to use a recuperator.

Basically, we start the engine rotating with an electric motor and use an electric heater to pre-heat the catalyst bed and incoming air stream to 250°C. The fuel then burns in the catalyst bed raising temperature to 410°C. The hot exhaust gases then pass direct through a tube nest which preheats the incoming air stream to 250°C. This works quite well because the specific heat of argon does not increase significantly with increasing temperature. Hence, the temperature drop of the exhaust gases is therefore virtually identical to the temperature rise in the incoming air stream. The exhaust gas exits the tube nest at a temperature of ~100°C. The gases then enter a boiler where they are used to boil the liquid CO2, which drives the compressors. The electric power input can gradually be tapered down to zero as the system approaches thermal equilibrium.

Based upon a hot source temperature of 373K and a cold source temperature of 220K (Mars ambient), Carnot efficiency is 41%. Efficiency of real power plants is typically 50-60% of the Carnot efficiency. Given that this power plant is low power density, requires substantial power for start-up and inevitably consumes some power in CO2 compression irreversibility, an efficiency of 15% is about as much as can be expected. The system is also sensitive to changes in turbine flow rate and requires significant internal heat capacity, so cannot be used for load following. But the fuel is free and the system should work without the need for argon removal, additional fuel addition or solar preheating, although these things may enhance efficiency and power density.

Void · 2014-12-04 11:15:37

Nice

I feel intimidated to intrude, but I will anyway.

It appears to me that your exhaust has an excess of unburned Oxygen and all the other gasses, but maybe you will correct me. Please correct me and forgive me if I am wrong.

Argon 1.9%
Nitrogen 1.9%
Oxygen 0.145%
Carbon monoxide 0.0557%

It seems to me that if that can be collected it can be useful. One thought would be to extract it and breath it, but I think that is complex and undesirable.

The other option is if you could get some hydrogen or other fuel in a energy effective manner, and add it in then you could consume nearly all the Oxygen.

There could be several options:
If this actually works:
http://phys.org/news/2014-11-protons-fu … pects.html
Or Methane off Anaerobic digestion of organic matter,
Or perhaps use electrolysis of water or CO2 to provide a fuel, use the Oxygen for humans.

Or maybe you will find a way to capture more CO as in the methods being discussed in the spacesuit thread (Condensing the gases and perhaps using a centrifuge).

Last edited by Void (2014-12-04 11:35:46)

Antius · 2014-12-05 05:21:33

Excess hydrogen would certainly be useful in this way, as would excess CO. Methane might be problematic, as the low combustion temperatures would result in soot build up, which would clog the catalyst bed. If combustion temperatures can be raised to 500C by adding hydrogen, a much cheaper iron oxide catalyst could be used oxidise the CO.

Anaerobic methane would be a useful resource for a martian base. For steel production: heat it to 1000C and it will reduce Fe2O3 to FeO, which can then be reduced to Fe in an electric furnace. As for rocket fuel, most engines burn fuel rich in order to maintain a reducing environment, so additional methane is always a good thing.

Void · 2014-12-05 08:02:07

Helpful information.

I have suggested a biosphere powered by CO and Oxygen from the Martian atmosphere, a Chemosynthesis method.

If no other source of hydrocarbons was available at a reasonable cost, then collecting the biomass and digesting it by an anaerobic method, then using a solar powered reforming method to extract Hydrogen from the Methane. I believe a variation on that would be to combine a gas mix of Methane and H20, at a high temperature, perhaps involving a catalyst.

http://en.wikipedia.org/wiki/Catalytic_reforming

So then Hydrogen.

Of course I am also hoping that the other methods of obtaining Hydrogen are available at a reasonable cost.

So your engine would really be a great asset for dust storm conditions, and at night and of course in the winter time at high latitudes. And the machine could be partially sheltered by being in a building or cave. To me this is much better than solar.

Nuclear? I think that also will be less desirable. I don't think I would have to list the problems involved with that.

Really amazed at your technical capabilities.

I wonder about using the engine in a Lava Tube? That's sheltered. As long as the entrance will circulate atmosphere sufficiently, that could be a good deal I think. Need water, but can probably get that figured out.
In fact maybe there is ice buildup in the lava tubes, but other methods will also be available I am sure.

Ice Caves:
http://en.wikipedia.org/wiki/Ice_cave

The rock of the cave having been cooled for eons buy night air, winter air? (In some cases). Maybe really a good heat sink for your engine? Or maybe the radiator would be at the "Window" where the universe is in view.

Martian Lava Tubes:
http://en.wikipedia.org/wiki/Martian_lava_tube

These natural shelters would also reduce the landed payload mass for manned missions which would be economically advantageous.[1]

Notice that there is a "VOID" in the lava tube

Last edited by Void (2014-12-05 08:57:41)

SpaceNut · 2014-12-05 20:56:45

[url=CO and O2 can be http://en.wikipedia.org/wiki/Solid_Oxid … Cell]solid oxide fuel cell (or SOFC)

A type of fuel cell in which the electrolyte is a solid, nonporous metal oxide, typically zirconium oxide (ZrO2) treated with Y2O3, and O2− is transported from the cathode to the anode. Any CO in the reformate gas is oxidized to CO2 at the anode. Temperatures of operation are typically 800–1,000 °C

Void · 2014-12-06 10:20:05

http://www.ceramatec.com/technology/cer … -cells.php

I think I may know where you are going with this Spacenut.

The above link suggests how to get hydrocarbons out of CO2. I am hoping that the Mars mix reduced of much of CO2 or all of it but containing O2 and CO might behave in a similar manner, and require less electrical power.

To justify my posting to this thread, a great deal of the purpose of this would be to produce a Hydrogen fuel to augment what Antiius has proposed, his "Martian air breathing engine".

I was never before a advocate of the notion of inhabiting lava tubes, but the engine of Antius, should it be viable, changes that for me. Previously in lava tubes I saw a lack of electrical power. Sure you could build solar panels, and power lines or pipelines, but how could such mass be transported? Conversely if you first inhabited the surface and then built enough resources to then inhabit the lava tubes, it seems like a silly process, since you have to first champion a more hostile environment to inhabit a less hostile environment.

So, I propose the method of a butterfly.
1) Land what you need to the surface of Mars.
2) Included will be a nuclear source. I am supposing Plutonium power, a minimum source to start with. Such as Curiosity has.
3) Land the air breathing engine and all other needed starter devices and resources. Get them into the lava tube.
4) Boot the air breathing engine with the plutonium power source.
5) Then we hope it has sufficient surplus of energy to power the reverse fuel cell device. That device then should provide Oxygen to the humans. It should also provide hydrocarbons from acting on a mix of CO, O2, and H2O, with perhaps some CO2. If possible, the N2 and Argon will not be filtered out and will also be involved.
6) Then if there is enough surplus electrical energy from the Antius engine, the reverse fuel cell can be activated to provide O2 for the population to breath, and also hydrocarbons.
7) Then the Antius engine would have to provide energy to reform the Hydrocarbons, and if the following actually works, then Hydrogen could be extracted:
http://phys.org/news/2014-11-protons-fu … pects.html
8) Then if you have extracted Hydrogen, you can inject it into the Antius engine to consume the remaining Oxygen, which as far as I can tell cannot be utilized very well, in any other manner.

Should all of this work then you have a functioning prelude to the butterfly, the butterfly being when humans emerge with their machines to utilize solar power.

I would think that then you could afford power lines and pipelines to channel energy and chemicals into the lava tube habitat, to develop a civilization further.

Of course the lava tube section inhabited will need to breath with the surface sufficiently to avoid suffocation. If the Oxygen and CO are depleted, then there is no point to trying to do this.

Also, if the energy gained from adding Hydrogen to the Antius engine is less than the gain obtained, there is some question as to it's value. Of course if it is providing Oxygen to people and mobile devices (cars, rovers, etc), then an energy loss might be tolerated.

Last edited by Void (2014-12-06 10:55:18)

SpaceNut · 2020-12-11 18:48:17

This seems to be a version of the same problem in that we can make a fuel and get the oxiding agent but at what cost to a crews safety level on mars.
Not much in the topic for the engine thou....

Calliban · 2022-06-07 09:36:52

NASA is working on ways of directly extracting O2 from the Martian atmosphere.
https://www.nasa.gov/directorates/space … _Mars_Air/

Although present in concentrations of only 0.1%, this is energetically much easier than attempting to chemically reduce CO2 using hydrogen. Carbon monoxide is present in even smaller concentrations 0.05%. If this can also be extracted using energy cheap thermal swings, then we have a fuel and also a reducing agent for iron production. By passing hot CO at 800°C through crushed hematite, reduced iron powder is formed. This can be removed from the ore using a magnet and then heated to liquid in an electric furnace.

Fe2O3 + 3CO = 2Fe + 3CO2.

Cast iron can be used to make framework for huge gravity stabilised pressurised habitats on Mars. You make a cross-braced iron framework, heap about 5m of dirt over the top and around the edges and then pressurise to 0.5bar with an oxygen, nitrogen, argon mix.

Void · 2022-06-07 11:18:15

That sounds very good. As I understand it the energy needed for chemicals humans will need, is very critical.

In place of the typical methods contemplated for getting Oxygen and Methane/Hydrocarbons. If this works, then fabulous.

Even if only the Oxygen part works, then I suggest getting Methane/Hydrocarbons from growing bulk plant materials and processing them in various ways.

I hope they can get the CO as well.

As a terraforming trick, it may be possible to enhance the effect of radiation on the upper atmosphere by putting a fine dust that has catalyst properties. This might be in conjunction with cloud seeding and also trying to add water vapor to the upper atmosphere with orbital mirrors.

So, then perhaps even more O2, and CO, and maybe even some Methane from that.

So, then the whole planet becomes effectively a solar power plant, with storage included.

Fabulous, we can hope.

And the Iron too, I hope. We need something like that.

Done.

SpaceNut · 2022-06-07 20:21:48

The basis for TSSD is a two-step thermally-driven cycle operating below ~260 C. thermal swing sorption/desorption (TSSD)--to generate oxygen from the Mars atmosphere with 10x less energy than the state of the art.
Our approach is motivated by thermodynamics: the minimum theoretical work to separate oxygen from the Mars atmosphere is ~30-50 times lower than to obtain it by splitting carbon dioxide.
Efficiency: TSSD is expected to be ~10x more efficient than MOXIE. For MOXIE, the target power requirement for oxygen propellant production is 30 kW. The TSSD estimate is only 4 kW; i.e., 90% less than MOXIE. Applying TSSD in rovers, the estimated power for oxygen pro-duction is only ~50 W/person.

2022_ph_i_ermanoski.png?itok=09TSp8rG

https://www.space.com/16907-what-is-the … -mars.html

A summer day on Mars may get up to 70 degrees F (20 degrees C) near the equator, but at night the temperature can plummet to about minus 100 degrees F (minus 73 degrees C)

magical absorbent material required, unless making use of mar temperatures requires energy to make the material to work.

Void · 2022-06-08 06:36:06

Here is one possible magical substance

https://www.nanowerk.com/nanotechnology … 20a%20room.
Quote:

New material steals oxygen from air

It has been criticized, that the amount of O2 and CO is so small, but look at all the water animals that breath dissolved Oxygen from the water itself.

This conversation might be joined with "Atmospheric Separations", but I think I will work on this a bit in my lair over in terraforming.

Quote:

The material is so effective at binding oxygen, that only a spoon of it is enough to suck up all the oxygen in a room. The researchers' work indicates that the substance can absorb and bind oxygen in a concentration 160 times larger than the concentration in the air around us.

https://eos.org/research-spotlights/cur … atmosphere
Quote:

0.161%
On average, the data revealed, the equatorial Martian atmosphere consists of 95% carbon dioxide, 2.59% nitrogen, 1.94% argon, 0.161% oxygen, and 0.058% carbon monoxide.
Curiosity Rover Reveals Oxygen Mystery in Martian Atmosphere
eos.org/research-spotlights/curiosity-rover-reveals-oxygen-mystery-in-martian-atmosphere

If it is possible that the substance will not clog up with other Martian gasses in Martian atmosphere, and if a concentration of 160 * 0.161% = 25.76 of concentration vs. 0.161 Martian atmosphere. But lots of if's there.

Good phrase from the article: "selective chemisorptive process"

Query: "selective chemisorptive process"

Response: https://www.bing.com/search?q=selective … e8e97bb1b4

Lots of materials there. I am not going to drill down further, this only shows that it is not impossible to do some of this, but the question is is it practical/economical relative to other options?

Done.

A further speculation.....I have wondered if you could pump Martian atmosphere into a solar oven along with water vapor, and superheat the mix, and if Hydrocarbons might result. I know we have a very capable Calliban, and I do believe there is a chemist who posts here as well.

Her might be a way to separate the outputs, I suspect: https://pubs.rsc.org/en/content/article … 1ta05869j#!
Quote:

Highly selective CO2 separation from a CO2/C2H2 mixture using a diamine-appended metal–organic framework

If a solar thermal oven of very high temperature would result in some Hydrocarbons showing up in the mix, that could be valuable.

But that is speculation on my part.

Hmmmm.....This seems to be in the ballpark!

https://phys.org/news/2017-11-technique … y-h2o.html
Quote:

Technique uses solar thermal energy to split H2O and CO2 for jet fuel

Quote:

Scientists with the SOLAR-JET Project have demonstrated a novel process to make kerosene, the jet fuel used by commercial airlines. The technique uses a high-temperature thermal solar reactor to create syngas. Shell Global Solutions in Amsterdam refined the solar syngas into jet fuel using the new Fischer-Tropsch method.

Picture Quote: https://scx1.b-cdn.net/csz/news/800a/20 … chersd.jpg

For more....Query: "Superheating a mixture of CO2 and H20"

Response: https://www.bing.com/search?q=Superheat … 98c9ea9ede

So, lots of utility there, I think. Methods to create disequilibrium in a gas mixture, and also ways to separate/concentrate component gasses.

This, in part is why I like heliostats, as it may be possible to use a collection of them to do multiple purposes. At some time promoting plant growth, and perhaps at another time creating chemicals, and yet another time heating something up.

I make note that it might be possible to feed a chemosynthesis process using heliostats with oven, Martian atmosphere, and of course water.

Done.

Last edited by Void (2022-06-08 06:58:14)

Calliban · 2022-06-08 08:56:03

If we can seperate CO from the atmosphere relatively cheaply, then the gas shift reaction can be used to make other fuels.

H20 + CO = H2 + CO2. Then:
2H2 + CO = CH3OH

By passing the methanol over a zeolite catalyst, heavier hydrocarbons can be built up.

However, these processes all consume additional energy. For short range vehicles and construction equipment, compressed CO and O2 could be burned directly in spark ignition engines with a CO2 buffer gas.

One thing that interests me - engines produce waste heat. Is there enough surplus energy here for an engine to concentrate its own fuel and oxidiser from the Martian atmosphere, whilst still raising surplus mechanical power? If so, our powerplants on Mars could be CO/O2 burning gas turbines which extract fuel from the Martian atmosphere using their waste heat to heat up the sorbant beds.

Last edited by Calliban (2022-06-08 08:57:23)

tahanson43206 · 2022-06-08 09:13:01

For Calliban (or anyone) ...

Please compare the binding energy of CO2 and perchlorate....

I'm trying to understand the hint/rumor? that it is less energy costly to liberate oxygen from perchlorate in a water brine, than to do the same with CO2.

Update: There are nearly 200 topics with posts that contain the word perchlorate.

(th)

Void · 2022-06-08 11:47:30

I guess I can be "Anyone" for a bit.

I am not strongly comfortable with my abilities in this subject.

Electrolysis:
https://arstechnica.com/science/2020/11 … 20hydrogen.

Biology:
https://pubmed.ncbi.nlm.nih.gov/31020520/

In general, I consider that as worlds age they may lose Hydrogen, and I suspect then become more Oxidizing.

Mars has a low gravity, and very poor magnetic field, so over time Hydrogen may leave at a faster rate than say for the Earth or Titan.

Some people call Perchlorate a "Rocket Fuel" which I think is wrong, it is a propellant that is an Oxidizer, I believe.

https://pubmed.ncbi.nlm.nih.gov/31020520/
Quote:

The dominant use of perchlorates is as oxidizers in propellants for rockets, fireworks and highway flares. Of particular value is ammonium perchlorate composite propellant as a component of solid rocket fuel.

Many things can be propellants, fuels and Oxidizers and inert gasses. Water and CO2 do not carry energy for a chemical reaction, but still can be propellants.

A chemical reaction results in increased molecular vibrations, which then cause a gas expansion our of a rocket nozzle.

For CO2, you have to have some other relative source of energy. Differential pressure from some method such as an external heat source.

On Mars electrical processes in dust storms are thought to create Oxidative chemicals. So an electric source creates an unconsumed chemical potential, of an Oxidizer.

On Earth plants put Oxygen into the atmosphere so that they can build their tissues mostly out of Hydrogen and Carbon. So, then they put that chemical energy into our atmosphere.

This article is particularly encouraging: https://spaceexplored.com/2020/12/01/br … n-on-mars/
Quote:

Perchlorate brine is believed to be in Mars’ soil, and the study has yielded a device that can produce 25 times the oxygen at 4% the energy cost using this brine.
Researchers at Washington University have been testing the device in a controlled environment that mimics Mars.

So, that's about what I know about it.

Done.

Last edited by Void (2022-06-08 12:00:55)

Calliban · 2022-06-08 14:43:27

tahanson43206 wrote:

For Calliban (or anyone) ...
Please compare the binding energy of CO2 and perchlorate....
I'm trying to understand the hint/rumor? that it is less energy costly to liberate oxygen from perchlorate in a water brine, than to do the same with CO2.
Update: There are nearly 200 topics with posts that contain the word perchlorate.
(th)

Apparently Calcium Chlorate thermally decomposes into oxygen and calcium chloride at 700K
https://www.researchgate.net/publicatio … aNH36ClO42

So we can infer that it is not particularly stable. It is an ionic compound as it therefore highly soluble in a polar solvent like water. We should be able to wash it out of soil and heat it to produce oxygen.

tahanson43206 · 2022-06-08 14:55:38

For Calliban re #23

Thanks for explaining the process!

I asked Google about Calcium Chloride, and my impression is generally positive ... it appears to be useful and not particularly harmful.

About 80,300,000 results (0.66 seconds)
A white, crystalline substance, calcium chloride serves an array of purposes from food preservation to highway construction. As far as food goes, calcium chloride is regarded as a safe preservative, commonly used as an anti-browning agent for fruits and vegetables, according to the FDA.
What Are the Dangers of Calcium Chloride? - Livestrong.com
https://www.livestrong.com › article › 253218-what-are-t...
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The Many Surprising Uses for Calcium Chloride - FBC Industries
https://fbcindustries.com › the-many-surprising-uses-for...
Oct 25, 2019 — Calcium chloride is often found as a firming agent in foods, due to its ability to absorb moisture. It helps hold canned vegetables together, ...

(th)

RGClark · 2022-06-16 13:37:28

Calliban wrote:

NASA is working on ways of directly extracting O2 from the Martian atmosphere.
https://www.nasa.gov/directorates/space … _Mars_Air/
Although present in concentrations of only 0.1%, this is energetically much easier than attempting to chemically reduce CO2 using hydrogen. Carbon monoxide is present in even smaller concentrations 0.05%. If this can also be extracted using energy cheap thermal swings, then we have a fuel and also a reducing agent for iron production. By passing hot CO at 800°C through crushed hematite, reduced iron powder is formed. This can be removed from the ore using a magnet and then heated to liquid in an electric furnace.
Fe2O3 + 3CO = 2Fe + 3CO2.
Cast iron can be used to make framework for huge gravity stabilised pressurised habitats on Mars. You make a cross-braced iron framework, heap about 5m of dirt over the top and around the edges and then pressurise to 0.5bar with an oxygen, nitrogen, argon mix.

Thanks for that. Proposals for getting propellant at Mars commonly involve making hydrolox which is energy intensive in requiring breaking down water into H2 and O2 or producing methane with the hydrogen brought all the way from Earth or still breaking down water.

If instead we can get O2 and CO from the air you can have a CO+O2 combustion rocket engine. Not as energetic as H2+O2 or CH4+O2 but since Mars has weaker gravity you don’t need particularly high energy propulsion to escape from Mars.

Robert Clark

Last edited by RGClark (2022-06-16 15:08:33)

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