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#51 2021-04-17 07:56:35

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

For Louis re #50...

The idea of using CO and oxygen to operate internal combustion engines on Mars was explored at some length not long ago.  The recommendation I recall from that time (from GW Johnson ? ) was to be sure to conbine CO2 in the fuel component to serve the same role as Nitrogen serves on Earth.  The neutral gas serves as a buffer between the energy producing gases and the material comprising the engine. 

Regarding the boil off ... that scenario presumes you have gone to the trouble of liquefying the gases ... and if you've gone to the trouble of liquefying the gases, then you have on hand the means of capturing any gases leaked from the storage tanks due to heat leakage into the tanks, and if you have that capability I imagine you'd use it, in which case there would be NO boil off.

Perhaps I've missed something, so look forward to feedback that might arrive from yourself or other members.

(th)

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#52 2021-04-17 18:08:29

SpaceNut
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Re: Carbon Monoxide - a way to power Mars?

The IVF system of the ULA rockets use the boiloff to generate power in a as covered in the combustion topic boiloff is actively controlled on mars via the colder mars air during the night and isolated during the day to keep the storage from warming.

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#53 2021-04-18 01:56:18

kbd512
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Re: Carbon Monoxide - a way to power Mars?

Louis,

It could work, but a buffer gas like CO2 is still required to serve as the working fluid for any kind of piston engine to perform mechanical work with.  The Integrated Vehicle Fluids (IVF) hardware that ULA came up with is a massively de-rated all-Aluminum straight six racing engine that provides a mere 26kWe of output to use (vs 100s of kWs in racing form) to slow the boil-off rate of the LH2 to such an extent that running the engine consumes significantly less LOX/LH2 than using batteries or doing nothing at all.  IVF eliminates heavier batteries previously used for that purpose, which would still be required with the addition of solar panels, since the Centaur upper stage is orbiting Earth until it's ready to depart.  The net result was extending the time that the upper stage could remain on-orbit, without unacceptable propellant boil-off affecting throw capability to other planets or boost to GEO, from a mere 24 hours or less to about a month or so, by powering an integrated cryocooler and using the vapor pressure reduction to cool the remaining propellant tank contents.

I proposed using an O2/CO burner to power a SCO2 gas turbine for the heavy off-road vehicle for the following reasons:

1. The "burner", essentially a rocket engine injector pintle, does not require a significant quantity of diluent gas because it transfers heat from the flame to a closed loop SCO2 gas turbine.  The comparatively minor quantity of CO2 required to reduce the O2/CO flame temperature, relative to the quantity of CO2 working fluid required by a piston engine, can be provided by the hot CO2 effluent from combustion exhaust.

2. A SCO2 gas turbine is extremely compact, has an extremely low parts count, has a single moving part not subject to full torque reversals the way all reciprocating piston engines are (the Wankel is the only piston engine exception to the rule), and requires no lubricants apart from highly compressed CO2 used by the gas bearings.  The gas turbine and housing for 250kWe is something you can easily pick up with one hand.  The turbine wheel itself is slightly larger than an American 25 cent piece, roughly the size of a 50 cent piece.  The high temperatures and pressures require high grade Nickel-steels, primarily Inconel alloys, but tiny quantities of that material nonetheless.

3. On a pound-for-pound basis, as compared to O2/CH4, O2/CO driving a SCO2 gas turbine in a closed loop represents a lower total input power requirement (ECoE) to perform a given amount of mechanical work, especially if the CO2 is captured for re-use.  O2/CO will weigh more than O2/CH4 for equivalent energy content, but the tankage required to store the combination of the oxidizer and the fuel is more compact unless both the oxidizer and the fuel are stored as cryogenic liquids.

4. The LCO fuel is not cryogenic, so at least the fuel can be stored indefinitely without the use of a cryocooler.  If the oxidizer and fuel are consumed on a daily basis during construction activities, then the power loss to the cryocooler apparatus for storing the cryogenic oxidizer is minimal.  It's always half of what it would be for LOX/LCH4.  The extreme strength and therefore weight penalty associated with 10,000 bar storage of the gaseous forms of O2/CH4 is not required.

5. It's easier to re-capture and cool the hot / dry CO2 effluent from the burner for reuse, to further lower the power requirement, when no corrosive H2O is added to the exhaust effluent.  It would be more difficult to re-capture both CO2 and H2O from O2/CH4 combustion, although still possible.  More importantly, the combustion product of O2/CO is exactly what was taken out of the atmosphere, so no precious water is lost in the process, and even if we don't recapture the CO2, we're not losing any difficult-to-come-by H2O.

You've lamented our "profligate" energy usage a number of times.  The use of O2/CO combustion for stationary generators and land vehicles is one way to reduce energy consumption.  If battery energy density and cell life improves by an order of magnitude over the next decade, which seems very unlikely given all historical context, then batteries would obviously be more desirable, given their electrical efficiency.

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#54 2021-04-18 04:27:45

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

For kbd512 re #53

Nice!

SearchTerm:CO heater for SCO2 turbine
SearchTerm:SCO2 turbine heated by CO/O2 flame

I asked Google for help with the term SCO2

Supercritical carbon dioxide - Wikipedia
en.wikipedia.org › wiki › Supercritical_carbon_dioxide
^ "Supercritical CO2 Power Cycle Developments and Commercialization: Why sCO2 can Displace Steam" (PDF). ^ Talbot, David (April 11, 2016). "Desk-Size ... Applications · Solvent · Manufactured products · Working fluid
sCO2 Technology | netl.doe.gov
netl.doe.gov › coal › sco2
The supercritical carbon dioxide (sCO2) power cycle operates in a manner similar to other turbine cycles, but it uses CO2 as the working fluid in the ...
[PDF] SUPERCRITICAL CARBON DIOXIDE POWER ... - OSTI.GOV
www.osti.gov › servlets › purl
Jun 30, 2016 · efficiency high temperature supercritical CO2 (sCO2) cycles. ... This report addresses the concept definition of the sCO2 power generation ...
[PDF] Fundamentals and Applications of Supercritical Carbon ... - OSTI.GOV
www.osti.gov › servlets › purl
combustion process is transferred into the supercritical CO2 (sCO2) cycle via a ... Impurities in the working fluid as defined by anything other than CO2 can have ...
What Are Supercritical CO2 Power Cycles? | IEA Clean Coal Centre
www.iea-coal.org › what-are-supercritical-co2-power-cycles
Apr 5, 2019 · “The high density and volumetric heat capacity of sCO2 with respect to other working fluids make it more energy dense, meaning that the size of

There is also SCO2 gene, which is responsible for coding a protein used by humans, but that was the only citation ahead of a block of relevant ones.

(th)

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#55 2021-04-18 08:48:06

Calliban
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Re: Carbon Monoxide - a way to power Mars?

louis wrote:

I'd forgotten about this. It does seem that my original thought, that you could capture CO and oxygen from the atmosphere   and have a ready made energy store when humans landed a couple of years later is not so crazy and could work. Whether it's worth going to that trouble compared with just loading 30 tons of methane and oxygen on a Starship is another matter. I guess boil off over two months might be an issue?

If I read this correctly, Louis is suggesting the capture of CO and O2 already in the atmosphere on Mars.

It could be done, but it is no trivial undertaking.  The Martian atmosphere is 95% CO2, 2% Argon, 2.8% Nitrogen, 0.174% O2 and 0.0747% CO.  For this to work, you must first separate the CO2 from the other gases.  The CO2 in the Martian atmosphere is close to its triple point temperature, so relatively little compressor work would be needed to increase its density relative to the other components.  The remaining gases would be 40% Argon, 56% N2, 3.48% O2 and 1.49% CO, by volume.  The CO would be about 1% by mass.  On this basis, the calorific value of the non-CO2 content of the Martian atmosphere is about 100KJ/kg ( CO heat of combustion is 10MJ/kg).  At 1bar, the mixture would have volumetric energy density of 150KJ/m3.  At 300bar, it would be 45MJ/m3.  Because the CO and O2 are present in low concentration, you could probably store the mixture in a single tank, without risk of explosion.  To burn it, you would may need to pass it through a heated catalyst bed, as the concentration of fuel and oxidiser is too low to support flaming combustion, even under extreme compression.

In terms of total work output, one needs to compress 19kg of CO2 for every 1kg of stored gas mixture, which would release 100KJ of energy when released.  Put another way, the chemical energy content of the Martian atmosphere is 5KJ/kg or 65J per cubic metre at 6.1mbar.  This is almost certainly too little for any release of net energy from compressing and combustion of the Martian atmosphere.  None the less, it may be interesting to consider this as an energy storage mechanism.  The compressed CO2 has its own value as a CAES working fluid.  Heating it above 31°C would produce high pressure gas that could drive a compact gas turbine.  The stored compressed residual CO containing mixture has chemical energy density 100KJ/kg.  Taking the Cv of the gas to be 1KJ/Kg.K, complete combustion would raise the temperature of the gas by 100°C.  So along with its internal pressure energy, it could be a useful energy storage mechanism for short range vehicles and compressed air tools.  It is worthy of further investigation, I think.

Last edited by Calliban (2021-04-18 09:13:03)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#56 2021-04-18 10:56:30

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

For Calliban re #55 ...

I hope Louis will clarify what he meant.  I have not previously noted ** anyone ** suggesting anything other than converting CO2 to CO and O2.

My guess (admittedly ** only ** a guess) is that Louis is/was simply overlooking the (to me obvious) source of CO2.

However, there ** is ** a small chance that what he ** said ** is what Louis meant, for which your reply was generous and thorough.

SearchTerm:CO extracted from atmosphere: Calliban careful analysis Post #55

(th)

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#57 2021-04-18 11:09:03

SpaceNut
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Re: Carbon Monoxide - a way to power Mars?

This was discussed as well in the combustion engine topic as a plausible way to make use of the waste co byproduct of oxygen creation...
Keep in mind that once we use the co + o2 combinations that we are going to capture the exhaust function at a higher pressure that what was its starting point for taking it out of the mars atmosphere. This reduces the energy embodied levels when reusing the co, co2 and o2 in subsequent uses.

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#58 2021-04-18 17:48:32

louis
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Re: Carbon Monoxide - a way to power Mars?

Thanks for that analysis. Glad to have your agreement it could work as a precursor energy storage system.  There was work done on concentrating atmospheric water vapoour - which is present in far smaller quantities than CO. That would involve 885 watts constant power to produce 3 Kgs per sol (in season, since water vapour varies a lot during the Mars year). But that does add up over a couple of Earth years. Deploying PV panels (well they are on the Starship anyway) to produce the power to extract the gas from the atmosphere should not be a problem.


Calliban wrote:
louis wrote:

I'd forgotten about this. It does seem that my original thought, that you could capture CO and oxygen from the atmosphere   and have a ready made energy store when humans landed a couple of years later is not so crazy and could work. Whether it's worth going to that trouble compared with just loading 30 tons of methane and oxygen on a Starship is another matter. I guess boil off over two months might be an issue?

If I read this correctly, Louis is suggesting the capture of CO and O2 already in the atmosphere on Mars.

It could be done, but it is no trivial undertaking.  The Martian atmosphere is 95% CO2, 2% Argon, 2.8% Nitrogen, 0.174% O2 and 0.0747% CO.  For this to work, you must first separate the CO2 from the other gases.  The CO2 in the Martian atmosphere is close to its triple point temperature, so relatively little compressor work would be needed to increase its density relative to the other components.  The remaining gases would be 40% Argon, 56% N2, 3.48% O2 and 1.49% CO, by volume.  The CO would be about 1% by mass.  On this basis, the calorific value of the non-CO2 content of the Martian atmosphere is about 100KJ/kg ( CO heat of combustion is 10MJ/kg).  At 1bar, the mixture would have volumetric energy density of 150KJ/m3.  At 300bar, it would be 45MJ/m3.  Because the CO and O2 are present in low concentration, you could probably store the mixture in a single tank, without risk of explosion.  To burn it, you would may need to pass it through a heated catalyst bed, as the concentration of fuel and oxidiser is too low to support flaming combustion, even under extreme compression.

In terms of total work output, one needs to compress 19kg of CO2 for every 1kg of stored gas mixture, which would release 100KJ of energy when released.  Put another way, the chemical energy content of the Martian atmosphere is 5KJ/kg or 65J per cubic metre at 6.1mbar.  This is almost certainly too little for any release of net energy from compressing and combustion of the Martian atmosphere.  None the less, it may be interesting to consider this as an energy storage mechanism.  The compressed CO2 has its own value as a CAES working fluid.  Heating it above 31°C would produce high pressure gas that could drive a compact gas turbine.  The stored compressed residual CO containing mixture has chemical energy density 100KJ/kg.  Taking the Cv of the gas to be 1KJ/Kg.K, complete combustion would raise the temperature of the gas by 100°C.  So along with its internal pressure energy, it could be a useful energy storage mechanism for short range vehicles and compressed air tools.  It is worthy of further investigation, I think.


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#59 2021-04-18 18:07:32

louis
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Re: Carbon Monoxide - a way to power Mars?

If you read the original post it's quite clear I am referencing atmospheric extraction and concentration on the model of the work undertaken to create a machine for concentrating water vapour from the Mars atmosphere. As I understand it both CO and oxygen exist freely in the atmosphere.  So, in theory at least, atmospheric concentration could offer a simple energy storage system that could be put in place before humans land.

tahanson43206 wrote:

For Calliban re #55 ...

I hope Louis will clarify what he meant.  I have not previously noted ** anyone ** suggesting anything other than converting CO2 to CO and O2.

My guess (admittedly ** only ** a guess) is that Louis is/was simply overlooking the (to me obvious) source of CO2.

However, there ** is ** a small chance that what he ** said ** is what Louis meant, for which your reply was generous and thorough.

SearchTerm:CO extracted from atmosphere: Calliban careful analysis Post #55

(th)


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#60 2021-04-18 19:23:08

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

For Louis ... re #59

Thanks for clarifying that your meant what you said, and said what you meant.

Calliban's reply was quite generous.

I am under the impression that harvesting CO2 from the atmosphere is how the vast majority of CO will be made.

There might be a residual business in collecting trace gases.

(th)

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#61 2022-06-27 07:31:42

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

Mars_B4_Moon just found an alternative way of making CO ...

Mars_B4_Moon wrote:

Artificial photosynthesis can produce food without sunshine

https://www.thesciverse.com/2022/06/art … oduce.html

Turn CO2, H2O water, and electricity into food through a series of catalyzed reactions. Convert the CO2 into CO through an electrolytic process method with a silver catalyst on carbon paper cathode and an IrO2 anode.

If anyone has the time to investigate further, I am curious to know if the method described can be implemented on an industrial scale. Energy is still needed, of course, but perhaps this process is more efficient than others.

(th)

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#62 2022-06-27 08:37:08

Calliban
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Re: Carbon Monoxide - a way to power Mars?

TH, the method relies upon synthesis of acetic acid, with is produced through the catalytic carbonylisation of methanol.
https://en.m.wikipedia.org/wiki/Acetic_acid

If we can extract CO from the Martian atmosphere, then it can be used to produce acetic acid from nothing other than CO and water.

2CO +2H2O = 2CO2 + 2H2

2H2 + CO = CH3OH

CH3OH + CO = CH3COOH

If acetic acid is the energy source for food production, the Martian atmosphere already contains the key ingredient.  If indeed it is more energy efficient to extract CO rather than break down CO2, then that is what we shall do.

Last edited by Calliban (2022-06-27 08:41:52)


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#63 2022-06-27 12:03:07

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

For Calliban re #62

Thank you for taking the time to analyze the link found by Mars_B4_Moon.

It turns out to be a false alarm, but a worthy one to know about if it had been placed in a more appropriate topic.

This topic is dedicated to the proposition that CO stored energy will ALWAYS prove the most efficient ever developed on Mars.

All the other proposals require additional investment of energy, and each such investment is inefficient (or not 100% efficient is a better way to put it).

For some reason NewMars members seem to persist in wanting to use hydrogen which is energy costly, and completely unnecessary for most of the primary needs:

1) transportation
2) machinery at a job site
3) machinery at a habitat based facility

Possible:

4) Energy storage if  CO fuel cells prove out .... I've seen hints (from SpaceNut earlier in this topic)

What would be a fun exercise for ** someone ** would be to develop a table showing the energy costs of each competing idea for chemical energy storage.

Most efficient: CO cycle

Example: Imagine a simple internal combustion engine operating with the chosen fuel and a supply of oxygen.
If you make CO with the energy you have, and you run the engine as some reasonable workload, how long will it run
For the sake of making it consistent for all fuels, use one horsepower as the output of the engine.

Less efficient:

(not ordered)

gasoline
methane
diesel

... countless others

Of these, I would expect the order of decreasing efficiency to be:

methane
gasoline
diesel

Thanks again for your contribution to this topic!

For Mars_B4_Moon ... as you search the Internet, please keep a watch for news of anyone (one Earth or elsewhere) developing for the CO energy cycle for Mars (or Earth for that matter).

For the person who will develop the needed table:

Start with a fixed quantity of energy that might be provided by one of Louis' solar panels, or by one of Calliban's nuclear reactors.

It doesn't matter source of the energy ...

See how much energy you can get out at the delivery end:

CO ... will far exceed any other

methane ... will come in above the next

gasoline ... ?

diesel ... ?

Kerosene ?

other?

(th)

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#64 2022-06-28 01:50:48

Calliban
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From: Northern England, UK
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Re: Carbon Monoxide - a way to power Mars?

TH, why was the topic a false alarm?  Is the story fake?
https://www.thesciverse.com/2022/06/art … oduce.html


"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."

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#65 2022-06-28 04:27:39

Mars_B4_Moon
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Re: Carbon Monoxide - a way to power Mars?

I found 2 other articles but the articles more or less say the same thing and experiments seem to be aimed at food production rather than fuel

https://news.ucr.edu/articles/2022/06/2 … t-sunshine

“With our approach we sought to identify a new way of producing food that could break through the limits normally imposed by biological photosynthesis,”

The potential for employing this technology to grow crop plants was also investigated. Cowpea, tomato, tobacco, rice, canola, and green pea were all able to utilize carbon from acetate when cultivated in the dark.

https://scitechdaily.com/artificial-pho … -darkness/

Experiments showed that a wide range of food-producing organisms can be grown in the dark directly on the acetate-rich electrolyzer output, including green algae, yeast, and fungal mycelium that produce mushrooms. Producing algae with this technology is approximately fourfold more energy efficient than growing it photosynthetically. Yeast production is about 18-fold more energy efficient than how it is typically cultivated using sugar extracted from corn.

Last edited by Mars_B4_Moon (2022-06-28 04:27:53)

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#66 2023-11-12 07:14:15

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

We've had some recent interest in Carbon Monoxide as a fuel for transportation, so I thought it might be worth while to bring this topic by Louis back into view.

Louis put the topic in "Human Missions" which would give it a slightly different slant than would be the case for the Technology or Economy Index levels.

Comparison of CO and CH4 by kbd512:

kbd512 wrote:

325t of LOX/LCO = 4,257km/s of dV, at 300s
213t of LOX/LCH = 4,252km/s of dV, at 380s
112t of propellant weight differential in favor of LOX/LCH4 over LOX/LCO

LOX = 1,141kg/m^3
LCO = 1,250kg/m^3
LCH4 = 657kg/m^3

To burn 1t (1.522m^3) of LCH4 in a Raptor-like full-flow staged combustion engine, you need 3.6t (3.155m^3) of LOX.  46.3t (70.47m^3) of LCH4 combusts with 166.68t (146.08) of LOX, all told 216.55m^3 of propellant.

Mixture ratio for LOX:LCO is 0.5:1, or 1t of LCO requires 0.5t of LOX to completely combust, so to burn 1t of LCO, you need 0.5t of LOX.  This means 216.666t (173.333m^3) of LCO combusts with 108.333t (94.95m^3) of LOX, 268.283m^3 in total.  All told, 325t of CO2 must be collected and stored, at least temporarily.  LCO can be made from CO2, at room temperature, using an Aluminum nanoparticle catalyst coated with Carbon black, and UV from sunlight or a laser or electricity.

Therefore, a LOX/LCH4 powered rocket's propellant tank volume is almost exactly 25% larger than a similarly-sized LOX/LCO propellant tanks, providng the same delta-V capability.  LOX/LCH4 requires a Sabatier reactor, all the equipment to find / extract / purify H2O, and all propellant choices (LOX/LCO or LOX/LCH4) are cryogenic in nature and become liquid at roughly the same temperatures.  LCO requires a device to freeze solid CO2 out of the Martian atmosphere, plus the reactor to cleave atomic Oxygen from CO2.  From there, both solutions have to cool the propellant products to moderately cryogenic temperatures, but the LOX/LCH4 solution only has to cool 2/3rds of the equivalent propellant mass for a LOX/LCO powered rocket.


(th)

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#67 2023-11-12 07:15:25

tahanson43206
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Re: Carbon Monoxide - a way to power Mars?

And this post by Callibon on how to make CO ...

Calliban wrote:

This may be of interest.
https://pubs.rsc.org/en/content/article … c6cc08801e

Using a ZrO2 catalyst, CO2 can be thermally decomposed into CO and O2 at temperatures as low as 1200°C.  This temperature could be attainable using a dish type solar collector or very high temperature reactor.

When we get a nuclear industry up and running on Mars, we can begin reprocessing fuel using nitric acid.  A large fraction of fission products are noble metals like palladium, platinum and rhodium.  If these can be used to coat fuel elements and reactor internals, we can run a CO2 cooled fast breeder reactor without corrosion concerns and covert the CO2 coolant directly into CO and O2.  Finding materials that can retain strength at these temperatures will be challenging.  Stainless steel melts at 1400°C.  Maybe molybdenum?

(th)

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#68 2023-11-12 18:08:59

SpaceNut
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Re: Carbon Monoxide - a way to power Mars?

The moxie experiment shows how to break the co2 atmosphere into co and o2 but its up to add a storage tank and pump to make the best of doing the work.

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#69 2023-11-13 14:32:25

kbd512
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Re: Carbon Monoxide - a way to power Mars?

tahanson43206,

The 1,250kg/m^3 bulk density figure I used for both LCO and the 657kg/m^3 bulk density figure I used for LCH4 was based upon bad data and shouldn't be used.  I completely revised my calculations upon discovering this error, which arose from my use of bad data (bad material properties) from several different sources.  LCO bulk density figure was just plain wrong, and should be 849.5kg/m^3 when sub-cooled.  The 657kg/m^3 I've seen repeated in numerous different places, but actually applies to LPG (Propane), not LNG (Methane).

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#71 2023-11-13 20:03:02

SpaceNut
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Re: Carbon Monoxide - a way to power Mars?

Still looking for an engine to make use of as we appear to not have one.

We also must remember that the liquid is still put to a pressure an if i recall the Lox tank of the shuttle was 20 PSI.

Mars Rocket Propulsion System

Propellant performance of Mars-produced carbon monoxide

Mars In-Situ Resource Utilization Based on the Reverse Water Gas Shift: Experiments and Mission Applications

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#72 2023-11-14 19:11:17

SpaceNut
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#73 2023-11-14 19:12:26

SpaceNut
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Re: Carbon Monoxide - a way to power Mars?

GW Johnson wrote:

I looked in the first document of the rocket performance tests (second concerned ignition).  I was able to correlate c* vs Pc,  but not r.  At 1000 psia,  c* is near 4150-4160 ft/sec for LOX-LCO,  vs about 5900 for LOX-RP1,  6120 for LOX-LCH4,  and about 7950 for LOX-LH2.  All of these are weak power functions of Pc with exponents near 0.01.  But let's ignore that effect for now.

This figures into Isp along with the nozzle performance as Isp = [c* CF (1-BF)]/[CD gc] when you use the real-world effects.  For a well-designed nozzle CD ~ 0.995,  and gc is just the units conversion constant for the inconsistent units in which Isp is defined,  whether metric or US customary.  BF is the fraction of propellant flowrate drawn from tanks that ends up dumped overboard instead of going through the nozzle.  In a full-flow cycle,  BF = 0. 

CF depends entirely upon the Pc level,  the ambient backpressure,  and the expansion ratio;  the only thing in it related to chemistry is the specific heat ratio,  and that is near 1.2 for all the rocket combustion gases I ever heard of. CF is very sensitive to Pc level and expansion ratio.  It also has the nozzle kinetic energy efficiency embedded in it,  in the momentum term.

The strongest influences on Isp are c* (chemistry),  CF (Pc and expansion),  and BF (every % of bleed is a % right off the top). 

Using the numbers just quoted,  a BF = 0,  and a testable-at-sea-level vacuum (!!!) expansion CF=1.80 at 2000 psia,  we have LOX-LCO Isp = 4155*1.8 (1-0)/.995*32.174 = 4155*.0562269 = 233 sec,  for LOX-RP1 Isp = 5900*.0562269 = 332 sec,  for LOX-LCH4 Isp = 6120*.0562269 = 344 sec,  and for LOX-LH2 Isp = 447 sec.  (BTW,  the CO value of 233 sec is less than the typical sea level (!!!) value of 250-255 sec for a high-solids,  aluminized,  AP-oxidized,  composite solid made with HTPB or CTPB as the binder).

You only get the higher values folks often quote,  if you push the state of the art in terms of nozzle expansion and chamber pressure.  Mostly by higher chamber pressure,  which is limited by the capabilities of the turbopump design.  Which explains the push toward 4400 psia (300 bar) in things like SpaceX's Raptor,  and why Raptor 1 never achieved intended performance. 

One of the lessons in the course teaches how to use c* data and the CF result to get Isp,  where the CF result comes from decisions about Pc,  back pressure,  separation,  and expansion ratio.   All of that plus a database for c* and r models vs propellant combinations,  is in a spreadsheet supplied with the course.

GW

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#74 2023-11-15 10:33:05

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,493
Website

Re: Carbon Monoxide - a way to power Mars?

What I found was poor Isp performance with LOX-LCO,  due to low c*.  But if it is readily available,  you may not care about that.  It won't get you into orbit or halfway around the planet as a rocket propellant,  but it might serve for short-range "local" stuff. 

I suspect that in some sort of internal combustion engine,  it would perform about like methanol.  Just remember,  that on Mars,  you have to carry the oxygen (which outweighs the fuel),  and a diluent gas (which outweighs the oxygen),  to operate internal combustion devices as we know them here. 

If you are willing to undertake the extensive redesign to handle 500-1000 C higher flame temperatures,  you can delete the diluent gas. All fuels burn with air at about the same temperatures at the stoichiometric mixtures,  whether low or high energy.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#75 2023-11-15 18:50:09

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 29,052

Re: Carbon Monoxide - a way to power Mars?

We have looked at a lot of other uses for co2, co and other fuels that can be derived from insitu processing for quite some time but its the requirement to go with nuclear for power which means we must do with less fuel to drop the power requirements back down to go with those other supply systems power designs.

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