Carbon and Water Shipped as Reactants >> Methane and Oxygen

tahanson43206 · 2023-11-09 14:33:54

After extensive interaction with ChatGPT(4) I have overcome a starting idea to use glucose.

That idea was panned by kbd512 almost immediately, but it took me until now to work my way through the challenges that arise from the idea. The solution worked out by ChatGPT(4) was to ship carbon powder with pure water at the ratio of 1.5 water to 1.0 carbon.

Powder can be poured into the container of water, and while the container must be designed to safely handle freezing of the water, that challenge is going to confront anyone who ships water away from Earth.

Update later: It makes more sense to keep the water and carbon separate. Since the idea in the background of this topic is take advantage of the efficiency of ballistic launch services when they come online, the packages in each launch are likely to be (comparatively) small for quite some time. It seems reasonable to ship 3 containers of water for every 2 containers of carbon (going by mass). it might turn out that for volume reasons, the ratio of shipments/launches might be different. In any case, the idea of mixing the carbon into the water would appear to complicate operations at the destination, where the water has to be separated into hydrogen and oxygen, so retaining the purity of the water at shipment time would appear to be an overriding consideration.

(th)

tahanson43206 · 2023-11-09 14:36:49

Here is a Python program that shows the results of collaboration over a number of days:

# 2023/11/09 Revised Iterative program to show mass of ingredients
def process_carbon_and_water():
# Constants
water_molar_mass = 18.01528 # g/mol
carbon_molar_mass = 12.0107 # g/mol
methane_molar_mass = 16.04 # g/mol
oxygen_molar_mass = 32.00 # g/mol
# Mole counters
moles_water = 0
moles_carbon = 0
moles_methane = 0
moles_oxygen = 0
# Atom counters
hydrogen_atoms = 0
oxygen_atoms = 0
# Mass counters
mass_water = 0
mass_carbon = 0
# Mass processed (in grams)
mass_processed = 0
# Safety check
iterations = 0
max_iterations = 1000
while mass_processed < 1e6 and iterations < max_iterations: # 1 ton = 1e6 grams
# Process one mole of water
moles_water += 1
hydrogen_atoms += 2
oxygen_atoms += 1
mass_water += water_molar_mass
mass_processed += water_molar_mass
# Process one mole of carbon
moles_carbon += 1
mass_carbon += carbon_molar_mass
mass_processed += carbon_molar_mass
# Produce methane and oxygen
while hydrogen_atoms >= 4 and moles_carbon > 0:
moles_methane += 1
moles_carbon -= 1
hydrogen_atoms -= 4
while oxygen_atoms >= 2:
moles_oxygen += 1
oxygen_atoms -= 2
iterations += 1
print(f"Iteration {iterations}: Water: {moles_water}, Carbon: {moles_carbon}, Methane: {moles_methane}, Oxygen: {moles_oxygen}, Mass Water: {mass_water:.2f} g, Mass Carbon: {mass_carbon:.2f} g, Total Mass: {mass_processed:.2f} g")
return moles_methane, moles_oxygen, mass_water, mass_carbon, mass_processed
# Run the function
moles_methane, moles_oxygen, total_mass_water, total_mass_carbon, total_mass = process_carbon_and_water()
print(f"\nTotal Methane: {moles_methane} moles, Total Oxygen: {moles_oxygen} moles, Total Mass Water: {total_mass_water/1000} kg, Total Mass Carbon: {total_mass_carbon/1000} kg, Total Mass Processed: {total_mass/1000} kg")

The program will run on any computer that is running Windows, Linux or Apple .... It can also run on Chromebook, if the model is recent enough to install Linux as an option.

(th)

SpaceNut · 2023-11-09 20:36:01

Chemical reactions are more than the elements as they require other things to cause the reaction to happen.

So, break down 2H2O (l) → 2H2(g) + O2(g)

Next change (2C) + O2 = CO2 is a Synthesis reaction that we can feed into the Sabatier reactor,
or we go with C (s) + 2H 2 (g) <==> CH 4 (g)

Its about energy to creat the reaction that needs to be known with the rate of through put

tahanson43206 · 2023-11-09 21:25:32

Thanks for giving this new topic a boost!

A question I have that you might be interested in tackling is: What happens if we drop fine carbon powder into a container of pure water?

Does the presence of that much carbon in the mixture change the freezing point?

The ratio is 1.5 water to 1.0 carbon..

(th)

SpaceNut · 2023-11-10 11:19:50

It becomes a solution as the carbon if it dissolves at all, but I think you are looking for activated carbon which is not just water and carbon.

tahanson43206 · 2023-11-10 15:01:21

For SpaceNut re #5

Thanks for your insight on the question. After thinking about it further, since the needed ratio is 3 parts water to 2 parts carbon, it makes sense to divide a shipment into five containers, of which 3 are water and 2 are carbon.

Since I am looking to ballistic launch systems to reduce the cost of delivering these materials to orbit, containers filled with separate loads of the two materials should be able to carry their contents all the way to Mars at the least cost.

To reduce bursting force on the walls of the shipping container due to high gravity forces, the water can be frozen before launch. It will freeze in any case once it is in orbit.

I would be interested in seeing a layout of a processing facility that can take in these materials and deliver 5 tons of methane and oxygen per day for 240 days. Due to the inevitable inefficiency, I am guessing the facility will need to be sized to process 10 tons per day, in order to achieve a throughput of 5 tons per day.

Calliban just posted an interesting assessment that a light water reactor should be able to deliver sufficient heat in the right temperature range to support the NACL process described by kbd512.

I'm wondering if that reactor can be shipped to Mars in a single vessel.

(th)

SpaceNut · 2023-11-10 17:50:40

https://marspedia.org/Sabatier/Water_El … is_Process

Schematic of Methane production system for a Single SpaceX Starship over a period of two years, at about 150 tonnes of methane per year.

Take what is not part of the system out of this and you can get close to the design and factors for operations.

https://www.mdpi.com/2076-3417/10/9/3144

Efficiencies of 97.6% of CO2 to CH4 conversion and 13.8% for solar to methane on a clear sunny day were obtained by utilizing highly efficient CPV modules connected with multiple converters,...

https://ntrs.nasa.gov/api/citations/201 … 016419.pdf
Compact and Lightweight Sabatier Reactor for Carbon Dioxide Reduction

tahanson43206 · 2023-11-10 22:23:52

For SpaceNut re #7

Thank you for the interesting chart, and for the links you provided.

Here is a link to a chat with ChatGPT4 about making methane directly from hydrogen and carbon. It seems the Earth has been making methane that way for millions of years.

https://docs.google.com/document/d/1vgq … sp=sharing

(th)

SpaceNut · 2023-11-11 09:40:38

The reaction of Carbon with Steam Under Pressure: A study showed that methane can be formed when carbon, in the form of coconut char, reacts with steam under pressure. The rate of methane formation was found to be a linear function of the steam pressure. In experiments, methane formation occurred at temperatures between 650–950°C under high pressure. The rate of methane formation was also influenced by the hydrogen pressure, and small amounts of steam in the hydrogen atmosphere didn't significantly affect the methane production rate. This suggests that methane can indeed be synthesized directly from carbon and hydrogen under specific high-temperature and pressure conditions.
Synthesis at Extreme Thermobaric Conditions: Other research supports the possibility of synthesizing hydrocarbons, including methane, from inorganic carbon and hydrogen donors under extreme thermobaric conditions. In experiments, methane and heavier hydrocarbons were formed from CaCO3 and H2O in the presence of iron compounds at temperatures up to 1800 K and pressures up to 11 GPa. These conditions are indicative of the upper mantle thermobaric conditions and demonstrate the synthesis of methane and other hydrocarbons from methane at high temperatures and pressures.
Effect of Heating Duration: Increasing the duration of heating in experiments did not significantly change the composition of the reaction products produced at similar pressure and temperature. However, increasing exposure time led to the growth of heavier hydrocarbons (pentane and hexane isomers) in the product mixture. This indicates that while methane can be formed under these conditions, the reaction conditions also allow for the formation of heavier hydrocarbons.

That's what we are doing inside the reactor chamber which takes in the elements in liquid to gaseous forms to have methane created. Of course, it is depending on the sources of these and the energy requirement to get to the ability to put them into the chamber as well as the starting of that chamber's energy requirements. Out comes a gas so it's got to have more energy put into it to liquify it so that we can use the methane output. That however is only half of the fuel needs which while water is a byproduct one still needs more energy is something that puts the energy requirements for the total process back into the nuclear supplied range of energy required.

So, launching a rocket with fine carbon question is, does it lower the required energy, or does it just move it to a provided source not on mars so that the power system gets smaller in deliverable mass?

tahanson43206 · 2023-11-11 11:12:03

For SpaceNut .... re Post #9 but including others....

There appear to some folks who think that there is a way to cheat Nature by producing rocket fuel with less energy than Nature requires.

It takes energy to free oxygen from hydrogen in water, precisely matching the energy that was released when the water was created in the first place.

There are no magic procedures that are going to change that.

The same is true of methane burned with oxygen. The amount of energy released is going to precisely equal the amount of energy invested to create methane and to separate the oxygen in the first place.

There is no magic wand that is going to change that. The amount of energy needed is knowable. The amount of energy that must be invested in making rocket propellant is greater than the amount eventually released, due to losses that occur during the manufacturing process.

We humans have been enjoying the benefit of all the energy stored eons ago by Nature, when methane and other hydrocarbons were "manufactured" in the mantle of the Earth. Those days are coming to an end. When we humans move to Mars, NOTHING will be available for free! If you want to make methane, you're going to have to invest the energy that's needed. There is no magic wand that is going to change that.

This topic is focused upon just ONE of many ways of delivering supplies to the manufacturing facility. If we need other topics to discuss and to document other processes, we can create as many as are needed.

As it happens, this topic has the advantage that reactants can be shipped without having to worry about maintaining pressure if you are shipping gas, or keeping your tanks chilled if you are sending a cooled liquid.

This topic has the overarching advantage that everything you need to make rocket fuel is included. You don't have to scrounge around at the destination trying to collect atoms you need. All you need is equipment, and enough energy to invest so that you end up with the propellant you need to return home, or to explore further if that is you preference.

(th)

SpaceNut · 2023-11-11 11:53:06

Starship needs 800 mT to 1100 mT for the return trip home depending on how large a payload we bring home.
Of course, going from earth to mars with max payload requires 1200 mT with the 100 mT to land on mars surface with maybe 10 mT remaining in the tanks as margin for the landing zone.

with methane being about 240mT or 240,000 kg or 240,000,000 grams

CH4 is 12 + 4 = 16 grams
For 240 mT of fuel we need
carbon content is 180 mT
Hydrogen is 60 mT

did a google for Starship mars surface methane requirement to return home to firm up what we know.
Can Elon’s Mars Mission Return Home Using Farts? Can we travel back to Earth under our own ‘steam’?

1*uxmH_lWJOSjsUMv__wi5BA.jpeg

required to launch from the Martian surface holds 171.84 tonnes of methane must be near the 800 mT that I gave for the total fuel for methane as 180 mT is close enough

KkD9R3iafTYGPfYuUNugSQ-650-80.jpg.webp

In all a starship fully loaded with cargo on orbit needs 3x 100 mT launches from earth surface to get max cargo to mars from Gw's numbers which is the total of 1 cargo ship to mars with nothing to process or power the system once there.

kbd512 · 2023-11-11 15:49:52

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 Edit: bulk density figure is WRONG! DO NOT USE! Engineer's Toolbox says 849.5kg at -203.99C
LCH4 = 657kg/m^3 Edit: bulk density figure is equally WRONG! DO NOT USE! LCH4 can be densified to 448kg at -180C, but if the temperature is any lower then LCH4 will freeze solid

Ignore all bulk density figures from this point forward. The mixture ratios are still correct, the Delta-V values used are dimensionless and still correct. The propellant tonnage figures are also still correct.
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.

Last edited by kbd512 (2023-11-12 21:57:16)

Calliban · 2023-11-12 07:00:36

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?

Last edited by Calliban (2023-11-12 07:05:22)

tahanson43206 · 2023-11-12 07:49:15

This topic is set up to focus on the production of methane directly from free carbon and free hydrogen liberated from water by electrolysis or other suitable means .... ChatGPT(4) found a paper on doing exactly that:

Please note that the presence of steam appears to be an artifact of pressure creation, and that the steam itself does not appear to take part in the reaction described. The steam appears to provide the conditions necessary for formation of methane. I am looking for a method of achieving direct merger of hydrogen and carbon without the complication of steam as a pressure creating mechanism. However, if the use of steam turns out to be the most efficient way to achieve the desired result, then so be it.

nature letters article
Production of Methane from Carbon
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Published: 11 October 1958
Production of Methane from Carbon
J. D. BLACKWOOD
Nature volume 182, page1014 (1958)Cite this article
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Abstract
THE recent work of Blackwood and McGrory1 has shown that methane is formed when carbon, in the form of coconut char, is allowed to react with steam under pressure. The rate of formation of methane is a linear function of the steam pressure and appeared to be independent of the partial pressure of hydrogen when the latter is small. A similar study2 of the reaction of hydrogen and carbon under pressure at temperatures of 650–950° C. has shown that the rate of formation of methane is a linear function of the hydrogen pressure and that the addition of small amounts of steam to the atmosphere of hydrogen has no apparent effect on the rate of formation of methane. It is suggested that the mechanism of methane formation is the same. The rate of formation of methane, for the same carbon, prepared at 950° C., with 30 atm. of steam at 870° C., is 16 × 10−5 gm.mol./min./gm. carbon, and with hydrogen under the same conditions is 10 × 10−5 gm.mol./min./gm. carbon. The rate varies with the temperature of preparation of the carbon and lower-temperature carbons are more reactive, reaching a maximum reactivity to hydrogen when prepared at about 750° C.
References
Blackwood, J. D., and McGrory, F., Aust. J. Chem., 11, 16 (1958).
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Blackwood, J. D., Aust. J. Chem. (in the press).
Goring, G. E., Curran, G. P., Tarbox, R. P., and Gorin, E., Pittsburgh Consolidated Coal Co. Library (Pennsylvania, 1951).
Zielke, C. W., and Gorin, E., Indust. Eng. Chem., 47, 820 (1955).
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Authors and Affiliations
Division of Industrial Chemistry, Commonwealth Scientific and Industrial Research Organization, Melbourne
J. D. BLACKWOOD
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I'm hoping one of our members with mechanical engineering as an available discipline might be able to design a machine able to produce methane directly from carbon and hydrogen without going through convoluted and inefficient alternative processes that were discovered centuries ago by researchers working with coal.

I expect (hope) there is an optimum configuration of equipment and quantities of reactants that will result in the greatest possible efficiency. The reaction would be notable for it's production of energy when the needed conditions are created. As I understand the process, atoms of carbon and hydrogen are repelled by the electron shells at their exterior surfaces. When these atoms are brought into proximity under conditions of pressure and temperature as described in the paper cited above, covalent bonds will be established, resulting in the emission of thermal energy which should be measurable. The energy release will (apparently) take place via emission of photons in the infrared range. If the process is carried out in a batch form, as with a piston, the emission of photons in the expected range would indicate completion of the reaction for at least one hydrogen atom.

The first method of direct production of methane I would like to see explored is a simple mechanical piston. The quantity of reactants to be processed in a batch might be small, which would mean that the size of the mechanism would be correspondingly small. Ideally, it might be possible to build a demonstration compressor in a home workshop. This would allow many experimenters to stretch their skills at building precision machinery at modest expense.

(th)

tahanson43206 · 2023-11-12 13:35:53

tahanson43206 wrote:

In the session at the link below, ChatGPT(4) and I opened what I hope will become a series of interactions that will lead to understanding of a possible process for making methane and directly from carbon and hydrogen, without wasteful intermediate processes. This opening session sets the stage for a deeper dive into the chemistry and physics involved.
https://docs.google.com/document/d/1tU4 … sp=sharing
The discussion should be accessible to the average person, and certainly to the folks who are members of this forum.
Update several hours later .... It appears that persistence and ChatGPT's talents have allowed us to reach the goal I'd hoped might be achievable.
The transcript at the link below includes the one above, but it includes a set of data points that anyone can feed into a modern calculator or into a spreadsheet program to find the "Magic" numbers needed to make methane from simple carbon and hydrogen atoms.
https://www.dropbox.com/scl/fi/tfifi1pz … ckgwn&dl=0
There is plenty of work ahead... To design a practical machine to utilize this method will require the talents, knowledge and experience of professional level mechanical engineers, but there appear to be no roadblocks standing in the way. As nearly as I can tell, everything needed has been done before on Earth, to the point that most of it is routine.

(th)

SpaceNut · 2023-11-12 18:06:19

kbd512 · 2023-11-12 21:39:49

tahanson43206,

The source I used was way off, regarding the density of Liquid Carbon Monoxide. Lesson learned. Don't use random Google searches without doing more reading and cross-checking of sources.

I'm using the Engineer's Toolbox this time.

Liquid Carbon Monoxide (LCO), bulk density is 849.5kg/m^3 at -204.99°C:
Carbon Monoxide Density and Specific Weight vs Temperature and Pressure

Liquid Oxygen (LOX), bulk density is 1,237kg/m^3 at -203°C:
Oxygen Density and Specific Weight vs Temperature and Pressure

Liquid Methane (LCH4), bulk density is 438.9kg/m^3 at -173°C:
Methane Density and Specific Weight vs Temperature and Pressure

I need to figure out what LCH4's bulk density is when sub-cooled to -203°C.

I need to recalculate the propellant tank volumes required. Apologies.

Edit: LCH4 apparently can't be sub-cooled below -180°C, or it freezes solid. This makes all the LCH4 bulk density figures I see highly suspect, because they appear to show values far above what LCH4 can be densified to when sub-cooled below -173°C. This makes me think the engineers who have done this have used LNG with some constituent parts of Butane and

From UniTrove Engineering:

LNG has a density of around 430 kg/m³ to 480 kg/m³ and a gross calorific value of around 54 MJ/kg to 56 MJ/kg depending on the composition.

I finally figured out where these "real engineers" are getting their numbers from. I'm not one of those and don't even play one on TV, unless it pertains to software engineering. Look at what these engineering students and engineers are doing!. They're substituting the bulk density of Liquid Propane (LPG), for the bulk density of Liquid Natural Gas (LNG)! Gadzooks!

Liquid Propane (LC3H8), bulk density is 657.2kg/m^3 at -113°C:
Propane Density and Specific Weight vs Temperature and Pressure

A Comparison of Preliminary Design Concepts for Liquid, Solid and Hybrid Propelled Mars Ascent Vehicles Using In-Situ Propellants, Rowan University Department of Mechanical Engineering, by Jordan Conley, Devon Lefler and Steve Shaw; Faculty Advisor: Anthony Marchese

Flip to Page 17 (last page / appendix) of the paper linked to above. It lists CH4 as the fuel, for comparison with using CO / Carbon Monoxide in the LOX/LCO powered vehicle appendix from Page 16, yet in propellant characteristics it lists 717kg/m^3 as the bulk density of the fuel (which could only be correct for C3H8 / Propane sub-cooled to -172°C, according to the Engineer's Toolbox) and 1,140kg/m^3 as the bulk density of the oxidizer (which is demonstrably correct).

From the document:

Outreach
As engineers it is our duty not only to innovate but also to educate. With that in mind we looked to inform faculty members, our peers, the public, and the media regarding the scope of this project and the human exploration of Mars. Through presentations at local elementary schools we hope to inspire further interest in children to investigate the world around them and beyond.

How can you begin to educate the non-engineers out there, such as myself, when you, your colleagues, and your faculty advisor are all conflating the bulk density of sub-cooled LPG vs LNG?

I've seen this same mistake repeated in multiple different forums and documents (sub-cooled LPG bulk density substituted for sub-cooled LNG density). I'm sure it's just an honest mistake, but LNG and LPG are NOT the same thing! All this time I thought I was going crazy, thinking that LNG bulk density wasn't much different than LPG bulk density. That was clearly very wrong.

Last edited by kbd512 (2023-11-12 22:30:48)

Calliban · 2023-11-13 02:28:07

Kbd512, I share your frustration. Referencing the wrong fluid properties is unproffesional, especially for an academic institution. I recommend using NIST fluid properties database. I have always found it quite useful.
https://webbook.nist.gov/chemistry/fluid/

kbd512 · 2023-11-13 04:15:39

Let's try this again with the correct data (my inert mass assumption was for 50,000kg / 50t of dry mass for the vehicle plus payload):

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

Note: If you try to go much colder, then you will freeze these cryogens solid!
LOX = 1,237kg/m^3 at -203°C
LCO = 849.5kg at -203.99°C
LCH4 = 448kg at -180°C

To burn 1t (2.232m^3) of LCH4 in a Raptor-like full-flow staged combustion engine, you need 3.6t (2.910m^3) of LOX. 46.3t (103.5m^3) of LCH4 combusts with 166.68t (134.75m^3) of LOX, all told 238.25m^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 (255.05m^3) of LCO combusts with 108.333t (87.58m^3) of LOX, 342.63m^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/LCO powered rocket's propellant tank volume is almost exactly 44% larger than a similarly-sized LOX/LCH4 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.

This looks more like what I was initially expecting from a LOX/LCH4 propellant combination with a specific impulse 80 seconds higher than LOX/LCO, which is quite a lot. All that excitement on my part over faulty LCO bulk density data!

At least now I know why LOX/LCH4 is the favored propellant. The only remaining question is how much energy is required to synthesize LOX/LCH4 vs LOX/LCO. The same document from above, also quotes wildly unrealistic propellant tank inert mass fraction figures for both LOX/LCO and LOX/LCH4, as well as wildly optimistic specific impulse values for LOX/LCH4 (406s at 1,000psi, or almost as good as LH2; Raptor operates at 4,410psi, yet only manages 380s).

I'm not normally in the habit or proof reading the work of engineers and college faculty, but it seems I must, because their inert mass fractions are completely absurd, even for Mars gravity- 402kg for a LOX tank containing 32,500kg of propellant. Tank / oxidizer volume 28.5m^3, material density 2,800kg/m^3 - a generic Aluminum-Copper alloy, tank wall thickness of 6.35mm or 0.00635m as they put it, but the thing only weighs 402kg? I get 812kg (0.29^m3 * 2,800kg/m^3 = 812kg). 28.79m^3 - 28.5m^3 = 0.29m^3.

For an entire group of engineers, that's pretty sloppy work for a vehicle that 4 astronauts are betting their lives on. I sure hope they were taught the value of double-checking their own work before someone hired them to do real aerospace engineering.

The Delta-IV's 5m diameter cryogenic upper stage / Artemis Interim Cryogenic Propulsion Stage has a tank volume of about 95m^3 for comparison purposes. My proposed LOX/LCH4 vehicle contains, 2.51X as much propellant volume. My proposed LOX/LCO vehicle contains 3.61X as much propellant volume.

kbd512 · 2023-11-13 04:44:23

Calliban,

I can forgive the propellant density error as conflating LNG with LPG. It shouldn't have happened, but lots of other people have made the same error, so this is obviously quite common.

I can't forgive their LOX tank mass error. I'm pretty sure I know what they did, but that shouldn't have happened with 3 engineering students and 1 faculty member to check work. Somebody wasn't doing their job. That was very simple math, and their own numbers show their error, plain and simple. Nobody double-checked their own work.

LOX Tank Radius:
(3.79 + 0.00635) / 2 = 1.898175 <- rather than (3.79 + 0.0127) / 2 = 1.90135, which is what they should've done
LOX spherical tank volume = 28.65m^3 (using a tank wall either half as thick as they stated, or only enclosing 1/2 of the sphere)
28.65m^3 - 28.5m^3 (the volume of their LOX for their LOX/LCO rocket design) = 0.15m^3
0.15m^3 * 2800kg/m^3 = 420kg

Their tank mass was shown as 401.87kg in Appendix I on Page 16, so they clearly rounded somewhere, but unless 1/2 of the LOX tank is enclosed in Aluminum or the tank wall is only half as thick as stated, their math is clearly wrong.

tahanson43206 · 2023-11-13 07:25:03

For kbd512, Calliban and all ....

From my perspective, making a mistake is often more useful for a group project than not making one, since the mistake provides an opportunity to study a natural phenomenon more intently that might otherwise have been the case.

It doesn't matter (from that perspective) who makes the mistake, because the chase for the right answer is what is beneficial.

Thanks for several recent posts that help us all improve our understanding of the "real rocket science" we are attempting here.

While this topic will remain focused tightly on a very specific business concept, it has become host to some useful discussion about the properties of matter.

(th)

Calliban · 2023-11-13 09:07:24

Don't forget the pressure drop in the propellant lines and immiediately ahead of the pump impeller. With pressure drop comes temperature drop. So you need some margin between tank temperature and freezing point. We are dealing with liquids, so 10K should be sufficient.

The heat of combustion of butane is 92% that of methane, but its liquid density is fully 1.5x greater than of methane. Methane requires insulation around tanks and propellant lines. Butane is a saturated liquid at room temperature under a few bar pressure. Butane appears to be a better rocket fuel, all else being equal. But all else may not be equal. Methane is easier to synthesise than butane. Methane is formed using a simple sabatier reaction. Some kind of addition reaction would be needed to make butane. That is an extea reaction step that consumes more energy. So the choice between the propellants is not straight forward.

Last edited by Calliban (2023-11-13 09:26:26)

tahanson43206 · 2023-11-13 09:53:42

This is an experiment with Google Sheet sharing ....

The data points are for Volume, Pressure, Temperature of hydrogen gas in compression...

The spreadsheet is able to show the curve for one column of numbers, if the operator selects the column range.

There is probably a way to show all graphs at once, but that isn't necessary for this post ...

The point of the exercise is to show that the temperature of hydrogen passes through the critical value of 750 Celsius as pressure increases. It is ** that ** temperature that appears to be where methane forms, as covalent bonds are created and energy is released. it is (apparently) at or near that temperature that natural processes have been making methane in the mantle of the Earth for millions of years.

https://docs.google.com/spreadsheets/d/ … sp=sharing

(th)

tahanson43206 · 2023-11-13 10:45:27

In today's work session, ChatGPT computed the volume of hydrogen if it were reduced to liquid form ....

It turned out that the volume is less than the volume we had arrived at earlier, by compressing the given mass of hydrogen until the pressure reached 750 degrees Celsius.

The next session will pick up at that point, with Carbon and Hydrogen inside a cylinder 1 cm in diameter and 30+ meters long.

We will be resuming our session at this point, later today or tomorrow. Please write a summary of the initial conditions of the next phase of our investigation. Here are the factors of interest: Volume we are working with (Cylinder of 1 cm diameter and length 31.25 meters, the carbon as a solid, and the hydrogen in liquid form. In addition, I assume it is reasonable to estimate the temperature of the cylinder to be the same as the liquid hydrogen. I am unsure of the pressure inside the cylinder, but assume it is STP.
ChatGPT
ChatGPT
Certainly! Here's a summary of the initial conditions for the next phase of your investigation:
Initial Conditions
Cylinder Dimensions:
Diameter:
1 cm
1cm
Length:
31.25 meters
31.25meters
Volume:
0.002454 m3
0.002454m
3
(calculated from the diameter and length)
Carbon (Solid):
Mass:
0.0421 kg
0.0421kg
Volume (previously calculated): Approximately
0.00001913 m3
0.00001913m
3

Hydrogen (Liquid):
Mass:
0.0141 kg
0.0141kg
Volume (calculated at liquid state): Approximately
0.000199 m3
0.000199m
3

Total Volume of Carbon and Liquid Hydrogen: Approximately
0.00021813 m3
0.00021813m
3
Temperature Assumption:
Assuming the temperature of the cylinder matches that of the liquid hydrogen, which is typically at its boiling point of about
20.28 K
20.28K (or
−252.87 °C
−252.87°C)
Pressure Assumption:
Assuming the pressure inside the cylinder is at Standard Temperature and Pressure (STP), which is
1 atm
1atm or
101325 Pa
101325Pa
With these initial conditions, you have a cylinder containing solid carbon and liquid hydrogen, with a total volume that comfortably fits within the available space of the cylinder. The temperature is set to that of liquid hydrogen, and the pressure is assumed to be at STP. This setup forms the basis for the next steps in your experiment, where you might be exploring the conditions under which these elements interact to potentially form methane or other compounds.

In the next session, we will raise the temperature of the cylinder using external heating until it reaches 750 Celsius.

The pressure can be expected to rise to the value computed earlier.

According to a study done in 1958 (as I recall) the conditions inside the cylinder at that point will be favorable for formation of covalent bonds between carbon and hydrogen, to make methane, with release of additional thermal energy.

(th)

kbd512 · 2023-11-13 13:05:09

tahanson43206,

I want something that works. I'm not invested in what the correct answer is, but I still want that answer. I was really hoping that some of the smart kids out there did their homework (an assumption I now have to revisit), and that we could start with their basic design workup that a group of engineers or engineering students have already created to satisfy their intellectual curiosity. Someone like our GW is only supposed to be running the show, herding the cats as it were, and making sure that his wiz-kids are checking their answers. It's very difficult to evaluate the merits of one system over another when things as basic as spherical propellant tank weights are grossly incorrect. There's simply not a lot of math involved there (add / subtract / multiply / divide, plus 1 equation for the volume of a sphere). How can I trust that more sophisticated calculations are correct unless someone like GW is looking over their shoulders?

I liked the concept of LOX/LCO a lot more when there was a vehicle design advantage to be had (smaller propellant tanks), but apart from the complexity of the ISRU equipment, which may still be a major stumbling block for LOX/LCH4, there doesn't appear to be any other advantage to using LOX/LCO. That part was very unclear to me from the various academic papers I've read. Multiple people who came before me thought it was a reasonably good idea, to include people at NASA who invested a non-trivial amount of time and money into a basic LOX/LCO technology development program. I didn't come up with this on my own.

I am regaining an appreciation for the exponential nature of the specific impulse function, as well as why NASA has invested so much time / money / effort into LOX/LH2 and zero-boiloff technology. To be perfectly honest, we can easily and readily calculate the total amount of energy to make, cool, and store LOX/LH2. Beyond that, the incredibly well-proven RL-10 engine design is a multi-restart capable engine with deep throttling capability, 111.2kN of thrust, and 450+ seconds of specific impulse in a vacuum, all day, every day.

At this point, I'm inclined to think that LOX/LCH4 is also a waste of time and money, assuming we can find the water on Mars to make Hydrogen to begin with. RL-10 requires zero technology development. It's good-to-go, as-is.

The as-built dual-engine Centaur upper stage has more than enough thrust and delta-V capability to take 4 astronauts to orbit, even if you more than doubled its inert mass fraction (used thicker tank walls and insulation). It also has engine-out capability upon liftoff, to still leave the ground with one engine gone.

It has about 2,300kg of LH2 in that existing configuration, so 41,500Wh * 2,300kg = 95,450,000Wh of electricity supplied to the Hysata's reverse fuel cell technology.

95,450,000Wh / 240,000Wh per day (full output of 1 KiloPower reactor) = 398 days

If we use a bespoke KiloPower reactor design with a sCO2 gas turbine, to produce 20kWe output per reactor (and the existing T-hot and T-cold specifications are more than sufficient to do this), then 199 days.

Let's get opportunistic and include 100m^2 of photovoltaics as well. We could be looking at completion of propellant production in 165 days.

Let's say we devote 2 bespoke reactors to propellant production, then propellant production is complete in 100 days or less.

Let's say we're serious about living on Mars and ship one of those 10MWe reactors that fits in a CONEX box and is fully self-contained. Let's further stipulate that it takes as much energy to cool the propellant as it does to make it. We're done with propellant production and cryocooling inside of 5 hours. That means we can feasibly fly our rocket twice per day, assuming the engine can take the stress of that many flights, which it probably can't.

What was the point of this make-work project related to using LOX/LCH4?

We either have access to the water source on Mars to make LCH4 or LH2 fuel, or we don't. If we don't, then we're right back to using CO2 to make LOX/LCO. If we make a hydrocarbon fuel, then it may as well be storable so we don't have to invest more energy into keeping it cold. There's not much we can do about the requirement to keep the LOX cold. It's an energy sink, plain and simple, just like all rockets launched from Earth. Send a real reactor to Mars so we have real power to work with, and then the rest of this becomes an engineering design exercise, rather than a science experiment. We need 2 reactors for redundancy and as many solar panels and power cables as we can stuff into the 3rd and 4th Starship landers. More power is more better. More backups is more better.

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#1 2023-11-09 14:33:54

Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#11 2023-11-11 11:53:06

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#12 2023-11-11 15:49:52

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#17 2023-11-12 21:39:49

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#19 2023-11-13 04:15:39

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#21 2023-11-13 07:25:03

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#22 2023-11-13 09:07:24

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#23 2023-11-13 09:53:42

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

#24 2023-11-13 10:45:27

Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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Re: Carbon and Water Shipped as Reactants >> Methane and Oxygen

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