Glucose as Rocket Fuel/Oxidizer Shipment Method

tahanson43206 · 2023-10-30 06:57:28

For SpaceNut ... we only had one topic that contained the word "glucose", and it was Louis' topic on synthesizing the molecule.

This topic is offered for those who would like to collect information on or to comment upon the efficacy of using glucose as a way of efficiently transporting rocket fuel to remote locations in the solar system. Glucose has the distinct advantage that it can be shipped in any of the ballistic launch systems currently under development. It can be restored to oxygen and methane using nothing more than solar power, but having a nuclear reactor available to make propellant would certainly be advantageous.

Pending correction by a ** real ** chemist, I will concede that the atoms in glucose are NOT a one-for-one match with those needed to make methane/oxygen propellant. Instead, only about 1/3 of the mass of a shipment can be converted to propellant. The balance can be made into propellant using insitu resources.

Updated: It will be understood that glucose as a shipping method for rocket propellant assumes the equipment that will use it is designed to burn methane and oxygen.

As it happens, the rocket design for Dr. Zubrin's book "The Case for Mars" was based upon methane/oxygen.

Dr. Zubrin proposed to carry Hydrogen along on a trip to Mars, and to make propellant using CO2 from the atmosphere.

This topic is proposed as a way to ship hydrogen to Mars, and at the same time, to eliminate part the fuss and bother of capturing CO2 from the atmosphere.

*** Update 2023/11/05 (th) This topic has the potential to contain the information an entrepreneur would need to develop a business plan for sale of propellant at any location away from Earth. Glucose has many advantages over competing proposed ingredient shipment forms. It can be delivered to destinations using the most cost effective method available, since time does not diminish the quality or quantity of glucose in any way.

All that is required at the destination is energy to re-create needed molecules from the feed stock. As is shown in Post #2, the atoms in a shipment of glucose may be re-arranged into methane and oxygen, with no loss of atoms.

Update 2023/11/06 (th) I'd like to give credit to kbd512 for suggesting the "Atom Count" method of explaining how glucose converts to methane and oxygen without loss of atoms along the way. The "secret" is to start with six glucose molecules:

This equation shows that two molecules of glucose (each with 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms) can produce four molecules of methane (each with 1 carbon and 4 hydrogens) and three molecules of oxygen (each consisting of two oxygen atoms), ensuring all the atoms from the reactants are conserved in the products.
Update inserted into quote: The six oxygen atoms are the limiting factor for sales of the material delivered to customer site. Only three of the methane molecules can be sold with the oxygen, so three molecules are left over along with three free carbon atoms.
The correct representation of the reaction in a tabular form with the final count of atoms explicitly shown would be:
+---------------------------------+-----------+---------+----------+----------+
| Reactant/Product | Carbon | Hydrogen | Oxygen | Methane | Oxygen |
+---------------------------------+-----------+---------+----------+----------+
| Initial Molecules | | | | | |
| Glucose | | | | | |
| (C6H12O6) x 1 | 6 | 12 | 6 | 0 | 0 |
+---------------------+-----------+---------+----------+----------+---------+
| After Reaction | | | | | |
| Methane (CH4)x4| 3 | 12 | 0 | 3 | 0 |
| Oxygen (O2) x 3 | 0 | 0 | 6 | 0 | 3 |
| Carbon(free) | 3 | | | |
+---------------------+-----------+----------+---------+----------+---------+
| Final Atom Count | 6 | 12 | 6 | | |
+---------------------+----------+-----------+---------+----------+---------+
| Molecule Count | | | | 3 | 3 |
+---------------------+---------+-----------+---------+-----------+---------+
This table reflects the atom economy of the process, showing that starting with one molecule of glucose can yield three molecules of methane and three molecules of oxygen, plus 3 carbon atoms with all atoms accounted for.
Credit for this table: ChatGPT4 (as edited / revised / corrected )

In the initial stages of this process, ChatGPT4 did not account for the excess carbon atoms.

(th)

tahanson43206 · 2023-10-30 06:59:27

This post is reserved for a chemical analysis (and comparison) of glucose vs methane/oxygen rocket propellant.

If we still have a ** real ** chemist in the membership, and that person is still engaged with the forum, I'd appreciate a post confirming or falsifying my assertion in Post #1.

Here is a link to an excerpt of a discussion with ChatGPT4 ...
https://docs.google.com/document/d/1oFq … sp=sharing

The formatting may look better if you try the link ... here is a part of the excerpt...

Let's proceed without introducing external oxygen and stick to breaking down glucose directly.
Given 1 mole of glucose (
), you can extract:
6 moles of Carbon
6 moles of Water
The breakdown is:
Electrolysis of 6 moles of water:
Combining 6 moles of hydrogen with the 6 moles of carbon:
Given:
Methane (CH₄) = 16.04 g/mol
Oxygen (O₂) = 32 g/mol
From 1 mole of glucose:
Methane produced = 6 moles of CH₄ = 96.24 g
Oxygen produced = 3 moles of O₂ = 96 g
For 1 ton (1,000,000 g) of glucose:
CH₄ produced = 96.24 g
180.16 g/mol × 1,000,000 g
180.16 g/mol
96.24 g ×1,000,000 g = 534,288 g or 534.3 kg
O₂ produced = 96 g
180.16 g/mol×1,000,000 g
180.16 g/mol
96 g ×1,000,000 g = 533,312 g or 533.3 kg
The results remain the same:
534.3 kg of CH₄
533.3 kg of O₂
The ratio for methane to oxygen when directly breaking down glucose is roughly 1:1.

(th)

kbd512 · 2023-10-30 14:31:31

The Glucose molecule is nominally, C6H12O6, I think. Glucose is storable, but would require on-orbit processing into fuels and oxidizers. If it readily converts to lighter hydrocarbons, I'm not aware of the process. I know it can be done, but at what energy cost?

LCH4 (LNG) is 25.3MJ/L and 55MJ/kg.
LC3H8 (LPG) is 26.8MJ/L and 50MJ/kg.
C12H24 (RP-1) is 35.2MJ/L 43.7MJ/kg (numbers for pure kerosene substituted- everybody's swill has an additives package).

Maybe GW can stop by and educate us about how much KNO3 is required to make sugar-based solid rockets.

I've been looking to see if there's something comparable for Glucose (I'm sure there is):
The Properties of RP-1 and RP-2, by Thomas J. Bruno, Physical and Chemical Properties Division, National Institute of Standards and Technology

LPG is the lightest truly storable liquid fuel, for a small hit in gravimetric energy density and small gain in volume metric energy density. If you're going to spend the money to process fuels, on-orbit, then LOX/LH2 is the best performer by a significant margin, because the lightest molecule (H2O), is being thrown out the back of the rocket nozzle at a greater velocity than heavier combustion products. H2O is also storable and far cheaper than Glucose.

Edit:
The Energy and Fuel Data Sheet, by Iain Staffell, University of Birmingham, UK

Last edited by kbd512 (2023-10-30 14:40:51)

SpaceNut · 2023-10-30 17:51:48

If I recall sugar rocket engines are a solid that kit form engines can be made with as a hybird type with injected extra oxygen to make it burn directly.

GW Johnson · 2023-10-30 19:55:02

As I recall, sugar nitrate was a concoction with a deserved bad rap for killing and injuring people in kitchen explosions. It's a mixture of sugar and sodium or potassium nitrate, heated on the stove to melt the sugar, for casting into motors where it hardens upon cooling. The problem was that the temperature to melt the sugar was very nearly the autoignition temperature of the propellant. It's just not something you want to mess with. And the Isp is in the same range as ordinary fireworks (only around 80 sec).

GW

kbd512 · 2023-11-01 07:03:06

GW,

Oh, come on. Live dangerously. What is life without a little fire and fury?

I like the idea of sending solids to orbit because they're so easy to store relative to cryogens, but I don't see how it's any better than delivering the propellants we already use. Unless the propellant material is directly consumable as a propellant, it seems like an added complication with little tangible benefit, apart from storage / stockpiling.

I can readily explain why RobertDyck's large ship has to be built on-orbit. It's far too large to fit in the payload fairing of any rocket, never mind far too heavy. Even if it was weightless, it still wouldn't make it to orbit on any existing rocket. That means it must be built on-orbit, and no other construction method is nearly as practical. Given the amount and total duration of complex assembly work already done to construct the ISS, this is an engineering challenge rather than a showstopper.

I can't as easily explain why we would want to ship a complex partially oxidized hydrocarbon foodstuff like Glucose, that has to be chemically reacted to synthesize a bi-propellant combination. It's not like shipping LNH3 to then strip the Hydrogen, either, which has the H2 density of LH2, but without the near absolute zero temperatures. We already have a commercial process and equipment to do that as well. Nobody turns sugar directly into fuel.

The N2 from LNH3 also has plenty of other necessary uses, so it's coming along for the ride regardless of the propellant combo. Glucose has the precursors for LOX and a light hydrocarbon fuel of some kind, but there's no use case where you don't end up shipping a lot of additional oxidizer, whether the end goal is to make Methane or RP-1. I still like the LOX / Paraffin Wax hybrid solids. The fuel is indefinitely storable, it can be re-cast into any number of desired boosters, and it's capable of being throttled like a liquid rocket.

The oxidizer seems to be the only part of a propellant combo that's particularly difficult to store in a compact way. KNO3, however is about 54% O2, it decomposes by about 400C, so maybe that's one easily storable oxidizer. The N2 has plenty of uses (pressurant, human consumption, purging, and fertilizer in the case of NH3). Potassium or pure Potassium Nitrate also has similar human / crop fertilization uses. Beyond that, how are you supposed to have a decent fireworks show on the 4th without KNO3?

KNO3 is 2.109g/cm^3, LOX is 1.141g/cm^3, which is just about as dense as LOX per unit volume, with the Nitrogen and Potassium included as a bonus. The only kind of oxidizer we typically use for interplanetary rockets is LOX, so that should do the trick. Paraffin wax is 0.9g/cm^3, so not much lighter than the heaviest grades of crude oil. I'm not sure how many uses we'd have for tar on Mars, but all the lighter grades of petroleum products make great fuels.

Calliban · 2023-11-01 08:07:18

Glucose melts at 150°C.
https://en.m.wikipedia.org/wiki/Glucose

So you could use it as part of a liquid bipropellant. As an oxygenated fuel, there may be problems with polymerisation blocking valves and nozzles. That is definitely a problem with pyrolysis oils from biomass. I don't know if that would be a problem or not with glucose, but it would need to be precisely defined. Density is 1.54g/cm3 - which is about 60% higher than kerosene. That is a plus. Heat of combustion is 15.6MJ/kg. That is not good. Only one third as much as kerosene.

Hydrocarbons could be produced by reacting glucose with a suitable reducing agent. Unfortunately, one of the oxygen atoms forms a C-O-C ether bond in the ring structure. So hydrogenation will tend to break the ring into smaller molecules. But using a suitable catalyst, like zeolite, you could build the reduced products into longer chain hydrocarbons. The only question is how much energy and equipment you would need to convert this food stuff into diesel? On Mars, Roberts seperated chloroplasts could convert sunlight into glucose with 4% efficiency.

Last edited by Calliban (2023-11-01 08:17:21)

GW Johnson · 2023-11-03 10:45:19

Glucose being a sugar already edible to most forms of animal life, I would think it might be better used as some sort of shippable form of a predecessor for food production than rocket propellant production. It would take a lot of energy and equipment to convert glucose into, say, methane and oxygen. It might only take a warm tank of water with microbes and plants to convert it into other forms of food.

GW

tahanson43206 · 2023-11-03 14:40:18

For GW Johnson ....

Thank you for helping to bring this topic back on point .... excursions about food or anything else are interesting but beside the point.

You have asked a reasonable question: What equipment, and how much energy is required to convert a ton of glucose into a ton of propellant?

In contrast to the lucky Mars lander who has a load of glucose on board, and the equipment needed to convert it back into fuel, our unlucky Mars lander with a load of hydrogen carried along to make methane has to collect all the CO2 that will be needed to make methane and LOX.

While the unhappy Mars lander with the hydrogen has many months of hard labor ahead, our lucky lander with everything needed for the return flight can get right to work.

Things will be even better for the lucky glucose return lander, if the glucose was landed some time before the current landing. Since glucose is a stable solid, it will have remained ready for use as long as needed, but our unlucky hydrogen carrying lander will find to dismay that half the hydrogen leaked out during the long flight from Earth.

(th)

tahanson43206 · 2023-11-03 17:29:58

Invitation for Chemical Engineer to Join Forum ....

At one time this forum included a ** real ** Industrial Engineer in the active membership, but that skill set appears to be unfilled at the moment. This is an invitation for someone with a background and experience in Chemical Engineering to join the creative and opinionated members who keep this forum perking along.

This topic is about chemical engineering, with space transportation applications. It is not about food or even beverages. It is not about agriculture or any of the other possible applications for glucose.

I'd like to see a comparison of the equipment needed to achieve a return flight from Mars, using the plan published long ago by Dr. Zubrin, in "A Case for Mars". That plan (as I remember it) involved carrying a load of Hydrogen to Mars, along with a nuclear reactor. The idea (as I remember it) was to compress Martian atmosphere to accumulate a supply of CO2, which would be split into Carbon and Oxygen. The Carbon was to be combined with the Hydrogen from Earth to make methane, while the oxygen would be compressed and cooled to make LOX.

It'd like to see an estimate of the energy required for preparation of a ton of propellant.

In comparison, I am proposing to make the same propellant by shipping glucose to Mars. Preparing the same propellant will require similar processes but different ones, since all the ingredients needed will be immediately at hand.

I'd like to seen an estimate of the energy required to make a ton of propellant.

The comparison should be written to stand up to scrutiny by professionals in the field of Chemical Engineering.

(th)

SpaceNut · 2023-11-03 17:44:56

Breaking down the Glucose molecule C6H12O6 can be done by contained gas burn and storage followed by separation but I am sure there are other methods.

tahanson43206 · 2023-11-03 19:34:42

For SpaceNut ....

In the absence of a ** real ** Chemical Engineer, your investigation of what would be required would be most welcome.

We have two processes on the table:

1) Describe the plan provided by Dr. Zubrin in "Case for Mars". That book has celebrated it's 25th anniversary (I saw a mention of that on the Mars Society web site (I think)).
2) Describe the ** best ** plan for converting glucose back into methane and LOX in the fewest possible steps, using the least amount of energy, and taking the least amount of time.

I am hoping the glucose solution will prove more cost effective, reliable and easier to do than any competing solution, even taking into account the use of CO2 from Mars as an input.

(th)

tahanson43206 · 2023-11-03 20:40:29

This will be an attempt to paste a transcript of a session with ChatGPT4 ... if the attempt fails, I'll put the source document on Dropbox.

The request was to compare the original proposal (hydrogen shipped and CO2 local) to my proposal.... all glucose shipped.

Please note that equations did not translate as originally written.

User
Tom Hanson
GPT-4
User
Hello Again! It is Friday evening 2023/11/03 at about 22:20 local time .... I'm hoping you might be willing to assist with a bit of chemical engineering ... not deep ... this is just a preliminary draft for a proposal .... You've already helped by confirming the chemicals involved will yield the desired output. This inquiry is about the processes needed to produce the desired output. Are you willing to give this a try?
ChatGPT
Hello! I'd be glad to help you with your chemical engineering query. Please go ahead and provide the details of the chemicals and the desired output, and I'll do my best to assist you with the processes involved.

User
OK ... we have two competing proposals. Both would produce methane and liquid oxygen as end products. The first solution was published 25 years ago, and it is considered the accepted method. The first solution carries a supply of hydrogen to the work site, where there is a supply of CO2 available. The first solution would collect the CO2 from the atmosphere, and make methane using carbon from the CO2 and the hydrogen that was brought along. The second solution would take a supply of glucose to the job site, and make the same quantity of methane and liquid oxygen. If you can, please show the processes that would be required, and estimate the energy required. If I have failed to provide enough information, please do not attempt to complete this request, but instead, let me know what is needed.
ChatGPT
To compare the two proposals for the production of methane (CH₄) and liquid oxygen (O₂), let's outline the chemical processes and the associated stoichiometry for both methods. Then we can discuss the energy considerations for each process.
First Solution: Sabatier Reaction and Water Electrolysis
The first proposal seems to employ the Sabatier reaction, which is commonly proposed for producing methane on Mars using the Martian atmosphere's CO₂ and imported hydrogen. The overall process involves two steps:
Sabatier Reaction:
Text removed because it did not translate to text format
the Sabatier reaction is exothermic, releasing about
−
165.0
kJ/mol
−165.0kJ/mol of energy.
Water Electrolysis:
The water produced in the Sabatier reaction is then electrolyzed to produce oxygen and hydrogen. The hydrogen is recycled back into the Sabatier reactor.
Equation removed because it did not translate to text
The electrolysis of water is endothermic and requires approximately
+
237.13
kJ/mol
+237.13kJ/mol of energy for each mole of water.
The net process yields methane and oxygen:
Equation removed because it did not translate to text
For the energy requirement, the Sabatier reaction itself is exothermic, providing some energy, but the electrolysis of water requires significant energy input. The energy needed for water electrolysis is substantial and typically involves electricity, which might be generated through solar power or another energy source.
Second Solution: Glucose Fermentation and Water Electrolysis
In the second proposal, glucose (C₆H₁₂O₆) is used as the source of carbon and hydrogen. The process likely involves two key steps:
Anaerobic Fermentation:
Glucose is converted to methane and carbon dioxide via a series of biological reactions, typically involving microbial action. The simplified overall reaction for anaerobic fermentation can be represented as:
Equation removed because it did not translate to text

This process is exothermic, releasing energy, but the exact amount can vary based on the conditions and microorganisms used.
Water Electrolysis (same as in the first solution):
In this case, the CO₂ produced in fermentation is not utilized to produce more methane (unlike the Sabatier reaction in the first proposal), so we focus only on the oxygen production:
Equation removed because it did not translate to text
The glucose-derived CO₂ could potentially be captured and utilized in a separate process to produce additional methane via the Sabatier reaction if hydrogen were available.
For the energy requirement of this solution, the anaerobic fermentation itself may not need external energy input since it is exothermic. However, the water electrolysis part requires the same substantial energy input as in the first solution.
Energy Considerations
Energy for Sabatier Reaction: The Sabatier reaction is exothermic, but it requires catalysts and specific conditions of temperature and pressure to proceed efficiently.
Energy for Water Electrolysis: Electrolysis requires significant electrical energy, which is a major factor in the overall energy balance.
Energy for Glucose Fermentation: The fermentation process can be considered energetically favorable, but it's not 100% efficient. The energy content of the glucose is higher than the energy content of the methane produced, meaning some energy is lost as heat or in non-methane byproducts.
Energy Input for System Operation: Both systems need energy for maintaining reaction conditions, separating products, and handling reactants and byproducts.
Without more specific data on reaction conditions, system efficiencies, and actual energy costs for each process, a precise calculation isn't possible. However, it's clear that electrolysis is the major energy consumer in both processes, and any proposal would need to account for the substantial energy required to perform water electrolysis to produce oxygen. If renewable energy sources are available, such as solar power, they could offset some of the energy requirements.
Do you have specifics on the scale of the operation, energy availability, or desired purity of the products? That information would be essential for a more detailed proposal.

User
Thank you! I think your reply will be helpful to stimulate discussion. Best wishes for similar success as you assist your thousands of other fans, world wide!
ChatGPT
You're very welcome! I'm glad to hear that the information provided will be useful for your discussions. If you have any more questions or need further assistance in the future, whether it's about chemical engineering or any other topic, don't hesitate to reach out. Best of luck with your proposal, and I hope it leads to a successful outcome. Thank you for your kind wishes!
ChatGPT can make mistakes. Consider checking important information.

(th)

tahanson43206 · 2023-11-03 20:44:12

Regarding ChatGPT's attempt in #13

The surprise (for me) was that ChatGPT4 proposed to ferment glocose .... that would imply the presence of water.

A supply of water was NOT included in my proposal, so I'll have to return to ChatGPT to clarify that fermentation is not a solution.

Whatever process is used is limited to the glucose itself. It contains all the atoms needed to make methane and LOX,. but getting from here to there is going to be challenging.

(th)

tahanson43206 · 2023-11-04 06:50:28

In the transcript below, ChatGPT(4) summarizes the Mars Direct plan to prepare methane and oxygen on site at Mars, using hydrogen brought along for the purpose...

User
Tom Hanson
GPT-4
User
Hello Again! It is Saturday 2023/11/04 at about 8:33 local time - I'd like to resume our conversation about de-composition of a chemical compound, and creation of two daughter compounds. Yesterday, you surprised me (in a good way) with a suggestion to use biological processes to decompose the substance we are working with. Your solution also presumed the presence of water, which is not available. Would you be willing to try again? I will attempt to frame the problem more accurately.
ChatGPT
Hello! I'd be glad to continue our conversation and try to assist you further. To provide a more accurate suggestion, it would be helpful to know the specific characteristics of the chemical compound you're interested in decomposing and the conditions under which this process is meant to take place, considering the absence of water. If you could provide:
The chemical formula or the name of the compound.
The conditions you're working with (e.g., temperature, pressure, other environmental conditions).
The desired outcome or the daughter compounds you aim to create.
Any constraints or limitations (e.g., no water, no high temperatures, etc.).
With this information, I can attempt to provide a more targeted suggestion.

User
Thank you for your encouragement, and for your patience as we attempt to enlist your support to explore a new idea for a business opportunity. The context is safe return of a space craft from Mars. A solution proposed by Dr. Zubrin 25 years ago, was(is) to use the Sabatier process to make methane and oxygen from the atmosphere of Mars. In order for the method to work, Dr. Zubrin proposed to bring hydrogen along in the vessel. His vessel would carry all the equipment needed to perform the compression of atmosphere, the Sabatier process itself, and all related activities. His proposal included a small nuclear reactor to provide power. Let;s begin with a short review from you database, of what you know about that plan.
ChatGPT
Dr. Robert Zubrin's proposal, known as Mars Direct, is a concept for relatively low-cost manned missions to Mars, which he developed in the 1990s. A central feature of this plan involves using in-situ resource utilization (ISRU) to produce the return-trip fuel directly on Mars, which significantly reduces the mass—and thus the cost—of sending humans to Mars.
The key chemical process at the heart of Zubrin's Mars Direct plan is the Sabatier reaction. Here's how it works:
Sabatier Reaction: This is a chemical process where carbon dioxide (CO2) from the Martian atmosphere is reacted with hydrogen (H2) to produce methane (CH4) and water (H2O). The reaction typically requires a catalyst, such as nickel, and optimal temperatures of 300-400°C to proceed efficiently.
The general reaction is:
See text version below...
Methane Production: The methane produced can be liquefied and stored as fuel for the return trip.
Water and Oxygen Production: The water byproduct from the Sabatier reaction can be split into hydrogen and oxygen via electrolysis. The oxygen is collected for breathing or rocket oxidizer, while the hydrogen is recycled back into the Sabatier process.
Hydrogen Import: In Zubrin's original plan, the hydrogen needed to kickstart the Sabatier process would be brought from Earth. However, carrying hydrogen all the way to Mars is not efficient due to its low density and the difficulty of keeping it cryogenically frozen for the entire trip.
Power Requirements: A small nuclear reactor, as you mentioned, would provide the necessary power for all the processes involved, including the operation of equipment for compressing Martian atmosphere, maintaining reaction conditions for the Sabatier process, and electrolysis for water splitting.
Dr. Zubrin's plan is notable for its elegance and simplicity, reducing the need to carry all the return fuel from Earth. The overall idea has influenced NASA's designs for Martian exploration, particularly in the development of technologies for producing propellant on Mars, which is a cornerstone of mission planning for future human missions.
It should be noted that while Dr. Zubrin's plan has not been realized in its original form, the fundamental concepts of ISRU and the Sabatier process are being incorporated into actual mission planning for Mars, such as NASA's Perseverance rover which carries an experiment named MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) to produce oxygen from the Martian CO2 atmosphere.

User
Thank you for this helpful review of Dr. Zubrin's plan, and for the summary of related developments in mission planning since publication of Mars Direct.. As a small request, could you show equations in a format suitable for publication in a text only venue? Your elegant formatting displays well on the browser window, but I have found it does not make the trip from the browser window to other formats.
ChatGPT
Certainly! I can present the chemical equations in a plain text format that should be compatible with most text-only venues.
The Sabatier reaction is represented by the chemical equation:
CO2 (g) + 4H2 (g) -> CH4 (g) + 2H2O (l)
In this equation:
CO2 (g) represents carbon dioxide in its gaseous state.
H2 (g) is hydrogen gas.
CH4 (g) is methane gas, the desired product for use as fuel.
H2O (l) is water in its liquid state, which can be further electrolyzed.
The electrolysis of water can be represented by the equation:
2H2O (l) -> 2H2 (g) + O2 (g)
Here, electrical energy is used to split water into:
H2 (g), hydrogen gas, which can be recycled back into the Sabatier reaction.
O2 (g), oxygen gas, which can be used for life support or as an oxidizer for rocket fuel.
These text-based equations should transfer well into text-only documents and publications.
User
This it ** so ** helpful. I am going to pause this conversation, and post your reply as amended.
ChatGPT
Absolutely, feel free to use the information as you need it. If you have more questions later on or need further assistance, don't hesitate to return. Good luck with your work and your posting!
ChatGPT can make mistakes. Consider checking important information.

ChatGPT

(th)

tahanson43206 · 2023-11-04 07:41:51

In the excerpt below, ChatGPT(4) shows a process that can make methane and oxygen from glucose, using a small quantity of water as a part of the process. The water may be obtained from supplies carried onboard an exploration vessel for life support. The water is not consumed, and it may be returned to the exploration vessel after propellant manufacture is complete.

I am back after attempting to prepare your transcript to share with others. I am disappointed to have to report that your experiment with use of Python text blocks to hold text did not translate for presentation. Earlier in the transcript, you had successfully shown equations in text form without using the Python Copy blocks. Please regenerate this session so that all the equations are delivered in text directly in the manuscript.
ChatGPT
I apologize for the confusion. Let's reformat the chemical equations involved in the proposed process of converting glucose into methane and oxygen without using code blocks.
Pyrolysis of Glucose:
General reaction (specific products can vary): C6H12O6 (s) → x CH4 (g) + y CO (g) + z H2 (g) + other products
Water-Gas Shift Reaction:
CO (g) + H2O (g) → CO2 (g) + H2 (g)
Sabatier Reaction:
CO2 (g) + 4 H2 (g) → CH4 (g) + 2 H2O (l)
Electrolysis of Water:
2 H2O (l) → 2 H2 (g) + O2 (g)
Methanation of Any Remaining CO:
CO (g) + 3 H2 (g) → CH4 (g) + H2O (l)
These reactions represent the overall chemical processes that could potentially be involved in the conversion of glucose to methane and oxygen on Mars, assuming the availability of water and an abundant energy source. Each reaction would take place in its respective reactor or unit as part of an integrated system for fuel production.
I think that adjustment will meet our needs! Thanks!
ChatGPT
You're very welcome! I'm glad that the adjustments fit your requirements. If you have any further questions or need additional assistance as you move forward with your project, feel free to reach out. Good luck with your work on this exciting venture!

(th)

kbd512 · 2023-11-04 14:27:20

tahanson43206,

Glucose doesn't contain enough O2 to become an all-in-one bi-propellant combination.

How about something like Acetic acid (CH3COOH)?

You can make 1 CH4 molecule and 1 O2 molecule from Acetic acid. You're only down 1 O2 molecule to completely combust 1 CH4 molecule.

Acetic acid and Sodium Hydroxide form Sodium acetate. Then you heat the Sodium acetate with Sodium hydroxide to yield Methane and Sodium carbonate. We can use Sodium peroxide to obtain the missing but required Oxygen.

Methane Upgrading of Acetic Acid as a Model Compound for Biomass Derived Liquid over Modified Zeolite Catalyst

There's also this option:
Lawrence Berkeley Laboratory - CALCIUM OXIDE AND POTASSIUM HYDROXIDE CATALYZED LOW TEMPERATURE METHANE PRODUCTION FROM GRAPHITE AND WATER. COMPARISON OF CATALYTIC MECHANISMS

The general idea is to ship a set of simple materials that are as dense or denser than water, either solid or liquid at room temperature, which can then be readily converted into LOX and LCH4, right?

Unfortunately, glucose is less than ideal for that purpose. It's a foodstuff and contains lots of Carbon and Hydrogen, which is great, but not much Oxygen. 1 CH4 molecule requires 4 Oxygen atoms to completely combust Methane.

Most of what Starship or simiarly powered vehicles require is Oxygen, not fuel. LOX/CH4's Oxidizer / Fuel mass ratio is 3.6:1.

Starship loaded with 260t (396m^3) of CH4 (657kg/m^3) will require 936t (820m^3) of O2 (1,141kg/m^3).

Acetic acid is 1,051kg/m^3 at room temperature.
Pure Carbon is 2,266kg/m^3 at room temperature.
Liquid CO2 is 1,101kg/m^3 at -35C.
Liquid Ammonia / LNH3 is 730kg/m^3 at -34C.
Liquid Nitrous Oxide / N2O is 1,220kg/m^3 at -89C.

Methane is 74.87% Carbon by weight, so Carbon is 194,662kg out of the 260,000kg of Methane fuel, so 65,338kg of Hydrogen.

CO2 is 27.27% Carbon by weight, so bringing enough CO2 to obtain 936t of O2 would mean 1,287t of LCO2 is required to make 936t of LOX, or 1,169m^3 and contains 350t worth of Carbon for making Methane. The volume of Starship propellant is 1,216m^3 for reference purposes. NH3 is 17.65% Hydrogen by weight.

370,187kg of NH3 is required to net 65,338kg of Hydrogen. H2O is 11.1% Hydrogen by weight, so 588,631kg of water would be required to obtain the same amount of Hydrogen from water.

Propane, the lightest storable hydrocarbon fuel, has an O/F mass ratio of 4.5:1, and a bulk density of 581kg/m^3 just below its boiling point, to just over 700kg/m^3 at the same cryogenic temperature as LCH4.

N2O is 36.36% O2 by weight, so 2,574t of LN2O is required to provide 936t of LOX.

We can see from basic math that no matter what we use as a fuel source, the oxidizer, which is always LOX, represents the lion's share of the tonnage of delivered materials, if we're going to send all the propellant materials to come back to Earth.

If we used Propane and fabricated Starship from a much stronger and cheaper steel than pitifully weak 304L stainless, such as Eglin ES-1 (which retains most of its room-temperature strength up to 930F), that's a at least a drastically stronger rocket for the same weight and a readily storable fuel requiring zero energy input to remain liquid. ES-1 yields at 193.9ksi at room temperature and 191.4ksi at 900F / 482C, with a Charpy V-notch of 56.2ft-lbs at room temp and 42.7ft-lbs at -40C. 304L yields at 30.5ksi at room temperature, with a Charpy V-notch of 159ft-lbs at room temp. Stainless is very tough, as the Charpy V-notch test indicates, but also as soft as taffy. ES-1 is more than 6X stronger, but it's yield strength is pedestrian compared to something like Aermet 100 or C350 steel.

Starship's propellant tanks were tested to rupture at ~120psi. ES-1 of equivalent thickness should rupture at 720psi, Aermet 100 at 960psi, and C350 maraging steel at 1,320psi. The welds would fail long before achieving that pressure level, but my point stands. By yield strength, C350 is almost 11.5X stronger than 304L at equivalent weight. You should be able to pressure cycle these inordinately stronger propellant tanks forever and they would never fail so long as they were kept inside the normal operating pressure limits of a Starship propellant tank. IIRC, all of these materials are also lighter per unit volume than 304L. The 40% Manganese steel I suggested is also cryogenic temperature compatible (doesn't become brittle and retains impact strength), and although its YS is only in the 100ksi range, IIRC, it would still be much much stronger than any 300 series stainless that hasn't been subjected to a rapid 50%+ deformation / thickness reduction. This is a room temperature forging processes that would deform a 1" rod into a 0.5" diameter bolt shank in a fraction of a second, for example, and then you see 100ksi to 150ksi YS, at the cost of ruining impact toughness and thus cryogenic impact performance. It's an irreversible grain structure alteration of the stainless steel (unless you melt it back down into liquid stainless steel). This is also what makes stainless and high Manganese steels unique. When they get super cold or super hot, their tensile strength doesn't change because their crystalline grain structure doesn't start to convert into Martensite, unlike high strength structural steel. This is what ARP does to all of its stainless engine bolts / studs / nuts to increase yield strength up to usable values for high-stress fasteners. Inert aerospace ceramic coatings is how we deal with the corrosive effects of LOX. Did I mention that these steels are easier to weld to aerospace quality standards than stainless?

YS of the 26% Manganese steel below is 400MPa / 58ksi:

The cryogenic high manganese steel is a new material POSCO developed with the storage and transport of LNG specifically in mind. POSCO undertook the project back in 2010 finalizing the development in 2013. The material contains 22.5% to 25.5% of manganese and can withstand temperatures as low as -196 °C.

High Manganese steel not "new" at all, it dates back to the early 1900s bank safe / vault steel:
Strain behavior of very new high manganese steel for 200,000 m3 LNG cryogenic storage tank

The simple answer is that Starship isn't coming back. The tonnage of materials required, plus energy input, both being as extreme as they are, represent pure fantasy. Once you go to Mars to live in a colony, you're not coming back.

That is why RobertDyck proposed the larger ship. That is why I second his proposal. Rob and GW have all the right ideas, but the propulsion technology doesn't exist to do what they want done. Even solid core nuclear thermal rockets only modestly reduce the propellant consumption. Until Isp is around 2,500 seconds, colonization isn't practical, but we're no longer talking about chemical propulsion or even existing nuclear thermal propulsion at that point.

Shipping a material like Glucose can provide a fuel, and Glucose is storable, but Propane is storable, it requires no conversion to rocket fuel, and the bulk of the mass is always the oxidizer, regardless of the fuel selection. Only toxic storable propellants like NTO and MMH, which are all Nitrogen-based, begin to approach 50/50 O/F mass ratios.

Unless this is another "pure scientific curiosity" experiment with little hope of a practical application (no different than battery powered cars and photovoltaics being used to power everything here on Earth), use a much stronger steel and room-temperature storable fuels like Propane to solve the cryogenic fuel transport and storage problem. Propane won't coke the injector pintles or turbomachinery. The oxidizer must come from the Martian atmosphere, as it represents the bulk of the propellant tonnage. It's not practical to ship everything to Mars. Something has to come from Mars, or there's no point to living there.

tahanson43206 · 2023-11-05 06:41:58

For kbd512 re #17

Thank you for continuing to assist with development of this topic by arguing passionately for alternatives.

It would help if you could support your arguments with chemistry.

I appreciate your statement quoted below:

Glucose doesn't contain enough O2 to become an all-in-one bi-propellant combination.

After dealing with an error involving omission of free carbon atoms in study of the decomposiion of glucose, I have established that a single glucose molecule can supply three methane molecules matched with oxygen. The balance of the glucose molecule consists of three carbon atoms and three methane molecules that have no oxygen available.

Thus, your statement is correct. Only about a third of the mass of the glucose molecule can be used immediately as propellant.

If there is a market for an alternative shipment method, we can open as many new topics as are needed to contain the information that would allow a business to exploit that market.

This topic is focused upon use of glucose as a practical way of delivering propellant to a distant location anywhere in the Solar system.

All that is needed to make propellant from the (approximately 1/3) of glucose at the destination is energy.

There are no losses due to leaking of liquids or gas along the way.

There are no expensive and massive pressure tanks needed.

No energy is needed to maintain liquids in a liquid state for shipment.

****

All solutions offered in this category (making propellant at destination) must include chemistry, energy requirements, equipment requirements, and procedure.

***
The business opportunity I see is very common on Earth.... There are thousands upon thousands of filling stations distributed over most continents.

Customers do not bring their own fuel to these stations. Instead, the stations hold the fuel for customers to purchase as needed.

In the case of any location away from Earth, the customers are going to need oxygen as well as fuel.

The business will have many choices about how to make fuel and oxidizer available.

The business about which ** this ** topic revolves will ship glucose to Mars (or anywhere) at the most cost effective way possible, so that the profit from sale will be as great as possible.

The alternative business ventures will deliver the exact same product, and will do all they can to maximize profits from the technology in which they invest.

A robust discussion carried out in the topics of this forum has the potential to be helpful for future entrepreneurs to study.

The competing plans for delivery of propellant to customers at Mars will ** all ** have to deal with issues of:

1) Supply of ingredients
2) Shipment of ingredients if shipped
3) Collection of ingredients of locally procured
4) Storage of ingredients in various stages of manufacture
5) Mechanisms and processes
6) Delivery to customers (eg, hoses, nozzles, connectors, measuring equipment)
7) Financial transactions management and control
8) Financing the entire venture
9) Collecting payments from customers

There may well be other considerations that are universal in nature.

If fhis topic, and competing topics, are to have value to future readers, they must include accurate information to the extent it is available.

(th)

GW Johnson · 2023-11-05 11:54:39

The question is whether the methane and oxygen can be made from glucose as cheaply as methane can be separated from natural gas, and oxygen liquified from air. Up to now, that answer has been "no", because those methods are exactly where those materials come from, and they have for nearly a century now. Those techniques are very well-developed, but they absolutely do not transfer to Mars.

For Mars, the question is different: how cheap is the Sabatier process making methane and oxygen from water and CO2, versus how cheap will it be to make methane and oxygen from sugar? I don't think anyone knows the answer yet, because nobody yet knows exactly how to do the sugar-based process, and the Sabatier thing has (as yet) not been scaled up to industrial quantities.

There is this: sugar would have to be shipped to Mars, while water and CO2 are already there. I think that may be very important. But I know nothing, otherwise.

But in the long run it pays never to rule anything out. There have been surprises. Given a local supply of sugar on Mars, it may be cheaper and easier to use the sugar process, whatever it turns out to be. One possible source could be farming sugar cane on Mars, although I cannot feature how to actually do that on a large scale.

GW

Last edited by GW Johnson (2023-11-05 11:58:45)

kbd512 · 2023-11-05 16:01:15

tahanson43206,

1CH4 + 2O2 (or 4O) = 1CO2 + 2H2O (the combustion products of Oxygen and Methane)

Glucose is C6H12O6 (C3H12 = 3CH4)
12O = complete oxidation / combustion of 3CH4, but Glucose gives us half of that to work with
Ratio of 2O2 (4O):1CH4 = 0.5:1

O6 = enough O2 to completely combust 1.5CH4 (Each CH4 completely combusts with 4O; 2O per 1CO2 and 2O per 2H2O)
3C = leftover Carbon (which will coke the interior of the chemical processor when the Glucose processor splits the Glucose molecules, no different than Carbon coking a piston engine from incomplete combustion of gasoline or diesel fuel, except the result is more expensive, unless we introduce more 3O2 to make 3CO2 or 6H2 to make another 3CH4 from the 3 spare Carbon atoms)

Acetic acid is CH3COOH (1CH4, 0.5X O required to completely combust 1CH4)
Ratio of 4O:1CH4 is 0.5:1

O2 = enough O2 to completely combust 0.5CH4
1C = leftover Carbon (which will also coke-out the interior of the chemical processor, albeit at a slower rate, and again we must supply 1O2 to make 1CO2 with this spare Carbon atom or 4H to make another Methane molecule)

To me, what this means is that we must split 6 water molecules if we use Glucose, or 2 water molecules if we use Acetic acid. Alternatively, we split 3CO2 molecules with Glucose or 1 CO2 molecule using Acetic acid.

Naturally, there's an energy cost and input material cost associated with doing this. Neither Acetic acid nor Glucose contains the correct proportion of Carbon / Hydrogen / Oxygen to make Oxygen and Methane in a ratio suitable for complete combustion of Methane, despite your assertion to the contrary. There may be some energetically favorable chemical synthesis process to go from Glucose to Methane, but if so then I'm not aware of what that is, and nobody does it at scale in the real world. I think they're not doing that already, because it's not energetically and thus monetarily favorable (i.e.- no good reason to do it).

Acetic acid is made from Methanol, which is itself made from Methane. Methanol is CH3OH. Methanol contains precisely enough Carbon and Hydrogen to make 1 Methane molecule, plus 1 lonely atomic Oxygen hanging out. That means we need to provide 3O, from splitting 3CO2 molecules, as energy and material inputs for complete combustion of Methane in a rocket engine, and then we end up coking-out the interior of the machine doing that, with pure Carbon (our expensive and delicate electro-chemical reactor, as opposed to a piston crown and combustion chamber valves that can be cleaned with a solvent and scrub brush).

Combined with Oxygen (which will have to be soured from CO2 on Mars), Methanol has a direct fuel cell application. We already make and store Methanol to burn in fuel cells or combustion engines, at significant scale, at this very moment.

Oak Ridge National Laboratory - Found: The ‘holy grail of catalysis’ — turning methane into methanol under ambient conditions using light

Energy.gove - Converting Methane to Methanol—With and Without Water

From the Chemistry Stack Exchange:
Converting methanol into methane

Question:

I know that methane to methanol is a common practice, but is it possible to convert methanol back into methane, and would it be a relatively easy process to achieve?

Answer:

Methanation is a process whereby synthesis gas is converted to methane.
Methanol, like nearly all organic molecules, can be gasified to form synthesis gas at elevated temperatures.
(Note: the gasification reaction is actually a complex balance of many types of reactions. Often times mixtures of CO, H2, H2O, and CO2 are obtained. The reaction above is the ideal case where complete conversion is achieved.)
Thus a process for converting methanol to methane could proceed via gasification followed by methanation.
However, since methanol is made commercially from methane by essentially the reverse process, this route is unlikely to be economically viable!

That response was from Curt F. He then received a "green religion" diatribe about how "green" the process might be (without evidence, of course, merely vague references to natural processes in plants, which humans have struggled to replicate). This was Curt's response to him / her:

That's all true. But it's worth noting that the partial oxidation of methane, that is, converting methane to methanol, has been a "holy grail" of chemical engineering for many decades. That is, an oxidative, (comparatively) low-temperature, low-pressure process to achieve CH4+12O2⟶CH3OH efficiently & economically, has been a goal of industrial chemistry for a long, long time. That's because methanol is easy to transport and store, and people are willing to pay more for that. And because natural gas is very, very cheap. So methanol -> methane isn't likely to be practical...

Emphasis added was mine.

Q: Why use Acetic acid instead of Methanol?
A: It already contains more of the O2 required for complete combustion. The ratio of leftover / unreacted Carbon (from Acetic acid or Methanol) is lower with Acetic acid than it is with Glucose. Typically, as in almost all cases, that means less input energy is required to convert it into 100% pure product that you actually want (Oxygen and Methane). That's it. Nothing else.

Q: Why not use the more complex Glucose molecules for making Oxygen and Methane?
A: The "complex series of side reactions" that the chemist noted in the above Stack Exchange question posed to him about making Methane from Methanol. Unless you can come up with energy-favorable reactions or reactions with greatly reduced energy input, then you need a lot more energy and a lot more input materials. If I had to guess, and I do since I know very little about chemistry, 3X greater for Glucose vs Acetic acid, by only looking at the ratios of elemental inputs to molecular outputs.

I then proceeded to tell you what the military's answer would be to a fuel shipping problem:
When the problem is that you need a readily usable fuel, then you ship a finished fuel product to your troops in the field. You don't ship some sort of precursor chemical requiring a science experiment to convert into fuel.

In certain cases, such as aviation fuels received aboard ships, the military will deliver a base fuel stock (kerosene), to which an additives package is mixed in, to obtain desirable chemical properties, such as a corrosion inhibitor, spark energy dissipation additive, and contaminant removal. The additives package is mixed into the fuel, and then the fuel is filtered multiple times before it goes into the jets. This is why our engines have so few problems, last so long in operation, and perform so consistently. There is an onboard laboratory which tests fuel samples multiple times per day. Any result other than what is considered optimal, will result in more filtering or blending-in more of the additives package to the base fuel stock. The same applies to the potable water quality. The avionics and electronics are tested in miniature clean rooms where anything short of fabricating a new microchip can be done.

As of yet, the military doesn't ship methanol, and then tell the onboard personnel to make kerosene from the methanol provided to them. We know that can be done, because it is presently done here in the US to supply bio-kerosene substitute fuels to our airline industry, but the facilities involved are larger than what would fit in an aircraft carrier and they consume power that not even the pair of nuclear reactors aboard an aircraft carrier could provide. The military has thought about this problem extensively and has spent many billions of dollars researching energetically favorable solutions to convert natural gas to methanol and then to kerosene.

Heck, even the oil companies thought of this and tried to do all of what you're talking about doing, back in the 1960s to 1970s. That's where the Socony-Mobil process and use of zeolite catalysts come from. The petroleum industry's organic chemists have been trying to devise alternative fuels (Methanol, bio oils from plants or algae, sugars, etc) ever since we the idea existed that one day the fuel would run out. We have methods to synthesize them from basic elemental or molecular inputs (CO2 and H2O), but they require enormous energy input.

We've made real progress on identifying the alternatives and synthesizing them at a lab scale, but only to the extent of reducing the energy input required to convert one chemical to another. It's a rare and serendipitous moment that an energy-favorable reaction is discovered, and chemists hunt for such reactions endlessly. Who doesn't want a free lunch?

tahanson43206 · 2023-11-05 21:35:13

For kbd512 re this topic ...

First, thank you for supporting the topic with tough questions!

I presented the challenge to ChatGPT, and it pondered the situation for quite a while (more than a few nanoseconds) and came back with this answer:

I'll begin with a review of the previous work:

I apologize for the confusion. Let's reformat the chemical equations involved in the proposed process of converting glucose into methane and oxygen without using code blocks.
Pyrolysis of Glucose:
General reaction (specific products can vary):
C6H12O6 (s) → x CH4 (g) + y CO (g) + z H2 (g) + other products
Water-Gas Shift Reaction:
CO (g) + H2O (g) → CO2 (g) + H2 (g)
Sabatier Reaction:
CO2 (g) + 4 H2 (g) → CH4 (g) + 2 H2O (l)
Electrolysis of Water:
2 H2O (l) → 2 H2 (g) + O2 (g)
Methanation of Any Remaining CO:
CO (g) + 3 H2 (g) → CH4 (g) + H2O (l)
These reactions represent the overall chemical processes that could potentially be involved in the conversion of glucose to methane and oxygen on Mars, assuming the availability of water and an abundant energy source. Each reaction would take place in its respective reactor or unit as part of an integrated system for fuel production.

Here is a table that shows that 6 glucose molecules can be converted cleanly to methane and oxygen with no left overs.

+---------------------+-----------------+------------------+--------------------+------------------------+------------------+
| Reactant/Product | Glucose (C6H12O6| Oxygen (O2) | Methane (CH4) | Carbon Dioxide (CO2) | Water (H2O) |
+---------------------+-----------------+------------------+--------------------+------------------------+------------------+
| Initial Molecules | 6 | 0 | 0 | 0 | 0 |
| Pyrolysis | -6 | 0 | 12 | 6 | 0 |
| Water-Gas Shift | 0 | 0 | 0 | -6 | 6 |
| Sabatier | 0 | 0 | +6 | 0 | -12 |
| Electrolysis | 0 | +6 | 0 | 0 | +12 |
| Final Molecules | 0 | 6 | 18 | 0 | 0 |
+---------------------+-----------------+------------------+--------------------+------------------------+------------------+

However, I will go back and ask for another try, since you have specifically requested atoms to count.

(th)

tahanson43206 · 2023-11-05 21:44:30

I returned to ChatGPT(4) and asked for the same table, but this time showing atoms to count:

+---------------------+----------+----------+----------+-----------+----------+
| Reactant/Product | Carbon | Hydrogen | Oxygen | Methane | Water |
+---------------------+----------+----------+----------+-----------+----------+
| Initial Molecules | | | | | |
| Glucose (C6H12O6) x 6| 36 | 72 | 36 | 0 | 0 |
+---------------------+----------+----------+----------+-----------+----------+
| After Pyrolysis | | | | | |
| Methane (CH4) x 12 | -12 | -48 | 0 | 12 | 0 |
| CO2 x 6 | -24 | 0 | -12 | 0 | 0 |
+---------------------+----------+----------+----------+-----------+----------+
| After Water-Gas Shift| | | | | |
| CO2 x 6 (consumed) | +24 | 0 | +12 | 0 | 0 |
| H2O x 6 (produced) | 0 | +12 | +6 | 0 | 6 |
+---------------------+----------+----------+----------+-----------+----------+
| After Sabatier | | | | | |
| Methane (CH4) x 6 | -6 | -24 | 0 | 6 | 0 |
| H2O x 12 (consumed) | 0 | -24 | -12 | 0 | -12 |
+---------------------+----------+----------+----------+-----------+----------+
| After Electrolysis | | | | | |
| O2 x 6 (produced) | 0 | 0 | +12 | 0 | 0 |
| H2 x 12 (produced) | 0 | +24 | 0 | 0 | 12 |
+---------------------+----------+----------+----------+-----------+----------+
| Final Atom Count | 0 | 0 | 0 | 18 | 6 |
+---------------------+----------+----------+----------+-----------+----------+

Here is the follow up text that goes with the table:

Explanation:
Initial Glucose: We start with 36 carbon atoms, 72 hydrogen atoms, and 36 oxygen atoms from the six glucose molecules.
After Pyrolysis: We are assuming that pyrolysis converts glucose into methane and CO2 without considering other products for simplicity. We subtract the atoms that went into making twelve methane molecules and six CO2 molecules.
After Water-Gas Shift: The six CO2 molecules react with water, so we remove those from our count and add the resultant water molecules.
After Sabatier: We convert the six remaining CO2 molecules into six methane molecules and twelve water molecules.
After Electrolysis: The twelve water molecules are split into six oxygen molecules and twelve hydrogen molecules (reused hydrogen not shown since it balances out).
In the final atom count, all the carbon, hydrogen, and oxygen atoms are accounted for in the form of eighteen methane molecules and six oxygen molecules, indicating that there is neither a surplus nor a deficit of any kind of atom, thereby obeying the law of conservation of mass.
Please note that this table is a simplification and doesn't account for other byproducts or the actual complexity of the chemical reactions. It is meant to provide a conceptual visualization of atom conservation throughout the process.

User
Thank you very much! I am hopeful your hard work on our behalf will prove helpful. However, we cannot know until we offer your work for review by our audience! In the mean time, thank you again, and best wishes for similar success with your thousands of other fans, world wide!
ChatGPT
You're very welcome! I'm glad I could assist you with your project, and I hope the information provided will be valuable to your team. If you have any more questions in the future or need further assistance, feel free to reach out. Best of luck with your business process and the presentation to your audience!
Thank you for your kind wishes, and I look forward to helping you and others again whenever needed. Take care and best of success with your endeavors!1

Note: I have confirmed that editing the table can cause the columns to line up. I will tackle that tomorrow.

(th)

kbd512 · 2023-11-05 22:00:32

Based upon something RobertDyck posted decades ago, you can make Ethylene from Acetic acid:

Google Patents - Ethylene production from acetic acid utilizing dual reaction zone process

Field of the Invention
The present invention relates generally to a process for the production of ethylene from acetic acid. More specifically, the present invention relates to a process including hydrogenating acetic acid utilizing a first catalyst composition in a first reaction zone and dehydrating or cracking hydrogenated intermediates with a second catalyst in a second reaction zone to form ethylene with high selectivity.
Background
There is a long felt need for an economically viable process to convert acetic acid to ethylene. Ethylene is an important commodity feedstock for a variety of industrial products; for example, ethylene can then be converted to a variety of polymer and monomer products. Fluctuating natural gas and crude oil prices contribute to fluctuations in the cost of conventionally produced, petroleum or natural gas-sourced ethylene, making the need for alternative sources of ethylene all the greater when oil prices rise.

There's also this paper about using Nitrous-Oxide and Propane from DARPA:
NITROUS OXIDE / HYDROCARBON FUEL ADVANCED CHEMICAL PROPULSION: DARPA CONTRACT OVERVIEW - Roger Herdy - Qualis Corporation - Huntsville, Alabama

Abstract
This work, in response to DARPA BAA 99-22, topic title “Small Scale Propulsion Systems,” focused on the development of a nitrous oxide (N2O) / propane (C3H8) rocket engine (NOP), that utilizes catalytic decomposition of N 2 O as an ignition system for propane. This propellant combination is proposed as an alternative to the present space propulsion systems that use hypergolic or cryogenic liquids, or solid propellants. Phase I work has resulted in a successful demonstration of the key technologies associated with the development of such a propulsion system. In particular, rocket performance for the NOP propellants and catalytic decomposition of nitrous oxide were demonstrated. The work began with two parallel efforts: the experimental evaluation of rocket performance using nitrous oxide and propane as propellants, and an experimental evaluation of various catalysts for the decomposition of nitrous oxide. The development of a catalytic reactor to efficiently decompose N2O for propane autoignition was central to this research effort. Experiments to demonstrate rocket ignition using the catalytically decomposed nitrous oxide began in late January 2001. These rocket tests were performed using improved rocket hardware (NOP Rocket 2), an improved thrust stand and a new atmospheric pressure test stand, (Test Stand 2) constructed at the Johnson Research Center on the campus of UAH in Huntsville, Alabama. Pitot pressure surveys and radiometric measurements were conducted by AEDC to independently measure thrust and provide spectral signature data. This work resulted in a patent being granted the author (US Patent # 6,779,335 “Burning Nitrous Oxide and a Fuel”).

kbd512 · 2023-11-05 22:05:12

I feel that this chart deserves its own post, because it shows the performance limits of LOX used to combust various hydrocarbon fuels, as it pertains to specific impulse and density impulse of the various propellant combinations:

Edit (I'm including the source for this, a NSF poster named "Proponent", because I think it does a great job of illustrating what matters most for a propellant combination optimized for use on Mars):

Topic: RP-1, methane, impulse density Q&A

Please read the entire topic for greater context.

Last edited by kbd512 (2023-11-05 22:34:40)

kbd512 · 2023-11-06 00:37:00

I started think some more about solid rockets using Glucose, or sugar, and then I remembered what the problem was that NASA encountered using paraffin wax in their solid rocket motor experiments. Paraffin wax is almost transparent to IR radiation. You need to add Carbon or Aluminum to the propellant to absorb some of the IR from combustion.

This leads me back to hybrid rockets, where we ship paraffin wax to Mars as a storable fuel, then heat it up to cast it into shape when required, use Moxie to make O2 from CO2, and then use the Carbon left on the Solid Oxide fuel cell plates, to mix into the paraffin wax to absorb IR radiation, as well as add to the thrust produced by the motor, and also to produce other Hydrocarbon fuels.

HyImpulse's HyPLOX 75/100 hybrid rocket motor is 24% paraffin wax fuel and 76% LOX oxidizer. Vacuum Isp is 321 seconds. They have 625kg of fuel per thrust chamber, occupying 700L of volume, while generating 100kN of thrust in a vacuum. Their 2nd stage LOX tank (operates in a near-vacuum / high altitude here on Earth) is a 6,800L CFRP design that weighs 94kg, feeding 7,758.8kg of LOX into 4 of their 75kN (sea level) / 100kN (vacuum) hybrid motors, for a total of 400kN of thrust on the surface of Mars.

Shipping complete motors to Mars, excluding the oxidizer, would be pretty easy because they don't weigh very much. 76% of the total propellant mass is produced locally on Mars.

Paraffin wax, which comes from crude oil, and Carbon black, which comes from Methane production here on Earth, are both reasonably low-cost and storable. Paraffin wax costs about $0.95 to $1.25 USD per kg, dependent upon grade and source. Carbon black is $1 to $3 USD, also dependent upon grade and source. Both prices are for mid to late 2023. This is a very cheap / non-toxic / non-exotic fuel for the infrequent launches and landings. Carbon black can be made on Mars from CO2. The primary uses for Carbon black are making tires and batteries, such as Lithium-ion batteries. 2023 Glucose sugar prices fell between $2.8 and $4.2 USD per kilogram.

This rocket will primarily be used for travel around the planet, or going to and from orbit a single time. Mars is very cold, so keeping the paraffin solid won't be a problem at all- it'll be as hard as a brick at typical Martian surface temperatures. For 4km/s delta-V hybrid solid rocket, either Glucose or paraffin wax looks pretty attractive. This solution entirely avoids the thorny problem of trying to turn Glucose or some other hydrocarbon back into Methane.

Glucose is 1,560kg/m^3. Paraffin wax is 900kg/m^3 to 930kg/m^3. Sugar definitely has the bulk density advantage. HyPlox 75, an actual rocket motor, is about 893kg/m^3. Glucose and KNO3 Isp is up to 137s, which is far below paraffin wax and LOX. APCP's Isp is up to 260 s.

As RobertDyck pointed out, explosives are the only kind of propellant containing all of the fuel and oxidizer for complete combustion, but specific impulse of high explosives is very pedestrian and they have a nasty tendency to turn your rocket and payload into confetti. This is best understood by comparing the total energy content per kilogram of TNT (4.6MJ/kg) with a kilogram of RP-1 (43MJ/kg). TNT is great for rapidly releasing all of the available chemical energy, but looks like hot garbage in terms of total energy density in comparison to lighter hydrocarbons, ignoring the fact that lighter hydrocarbons occupy more volume per unit of energy available. Hydrogen (120MJ/kg) looks great in terms of energy per unit weight, until you consider the fact that 1kg of LH2 occupies 3.377 gallons of volume. 1kg of RP-1 is about 0.333 gallons, and 3.377 gallons of RP-1 contains 440MJ of energy.

I would once again like to point out that CO2 alone, which can be obtained from the Martian atmosphere, can also be turned into Carbon Monoxide and Oxygen, which are both cryogenic propellants which can be produced on Mars, with a vacuum Isp of about of about 290 to 300 seconds, and an insane amount of thrust and density impulse and frontal thrust density (GW's stated reason for the attractiveness of solids here on Earth for boosters), relative to hydrocarbon fuels of any description, approaching that of solids and hybrid solids. The end byproduct, which goes right back into the Martian atmosphere, is the same thing that came out of the Martian atmosphere.

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#1 2023-10-30 06:57:28

Glucose as Rocket Fuel/Oxidizer Shipment Method

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