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SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: In-Situ Propellant Production, design a opensource demonstrator

https://upload.wikimedia.org/wikipedia/ … cesses.jpg

starting with mars co2 and h2o we are going to make methane and or methanol (syngas) this is the Sabatier reactors output which is the starting to convert to kerosene,

Very similar reactions

https://en.wikipedia.org/wiki/Sabatier_reaction

https://en.wikipedia.org/wiki/Fischer%E … ch_process

http://www.digipac.ca/chemical/mtom/con … atier2.htm

https://en.wikipedia.org/wiki/Gas_to_liquids

jet fuel or RP1 is kerosene...

A while back, I used JPL data on ultimate expected yields for methane-oxygen synthesis from CO2 and H2O to calculate the efficiency of the process.  It came out to be 5-8% - electrical energy to chemical product.  If one assumes that the power used in this process is provided by PV arrays with 20% efficiency; then the overall efficiency (sunlight to chemical fuel) is 1.0 - 1.6%.  It really would be almost as efficient to grow biomass in greenhouses and convert it into a liquid fuel.  Or maybe a solid fuel that could be used in a hybrid rocket.

Maybe Void's ice ponds will eventually be used to grow aquatic biomass.  This could then be dehydrated by leaving outside in the low pressure Martian atmosphere.  The dry biomass could then be compressed into fuel slugs using some sort of organic binder and loaded into a hybrid rocket.  There are quite a lot of byproducts from agricultural systems that could be converted into rocket fuels on Mars.  We could in fact grow algae for that exact purpose.  Dehydrating the algae would be easy on Mars, as all water would rapidly sublime in the low pressure atmosphere.

Agreed that a more efficient means to make methane is required since the level of co2 is so low is got to expend precious energy just to gather that and then water is the next hurtle in the string of processes that consume even more energy just to gather that commodity. All of which when we have both is still in need of even more energy to produce the chemical separations so that we can mash them up in a different combination..

The water ponds sure would use less energy over all since we are only expending the initial to gather the water and then wait for mother nature to do the remaining but man is impatient....

Calliban

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From: Northern England, UK

Registered: 2019-08-18

Posts: 3,789

Re: In-Situ Propellant Production, design a opensource demonstrator

The water ponds sure would use less energy over all since we are only expending the initial to gather the water and then wait for mother nature to do the remaining but man is impatient....

I suppose the big problem with the water pond is the large upfront energy expenditure.  In addition to the need for excavating a big enough hole for the pond; a huge amount of water would be needed.  Water is present on Mars as ice, frozen hard as stone, at around -60 degrees C.  It would take at least 0.5MJ/kg of heat energy to melt the ice.  Probably more like 1MJ/kg when thermal conduction losses are accounted for.  And we would need tens of thousands of tonnes of water for a decent sized pond of sufficient depth.

It would work if we had a nuclear reactor producing waste heat that we could use to harvest a lot of water.  To melt enough ice for a pond 100m aside and 7m deep, would take about 1MW-year of heat, assuming 0.5MJ/kg.  An achievable investment for a Martian base, if they have a nuclear reactor.  Solar power is not up to a job like that.

Last edited by Calliban (2020-07-04 22:57:22)

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

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: In-Situ Propellant Production, design a opensource demonstrator

If it were me I would target the methane leaks that we have observed for a starting point as these could be of a biological caused means to our use if its there. It would several processes with minimal energy input.. And if its just a vet then we might try to understand its source.

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: In-Situ Propellant Production, design a opensource demonstrator

https://nrt.org/sites/2/files/ignitor%20oct%2095.pdf
IGNITERS AND IGNITION TECHNOLOGY FOR IN SITU BURNING OF OIL

https://ntrs.nasa.gov/archive/nasa/casi … 001421.pdf
An ISRU Propellant Production System to Fully Fuel a Mars Ascent Vehicle

https://www.sae.org/publications/techni … 8-01-1963/

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: In-Situ Propellant Production, design a opensource demonstrator

Risk-value optimization of performance and cost for propellant production on Mars
https://smartech.gatech.edu/handle/1853/55584

Re-inventing the Wheel
https://ytprivate.com/watch?v=t2iHopdlFBg
https://hooktube.com/watch?v=t2iHopdlFBg

making propellant is a big deal at this point as we have not the power density to be able to achieve it when a mans life is at stake...

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: In-Situ Propellant Production, design a opensource demonstrator

MARS Return Fuel Production Using Table Top Electrolysis & Sabatier Reaction

IN-SITU PROPELLANT PRODUCTION ON MARS: A SABATIER/ ELECTROLYSIS DEMONSTRATION PLANT

Towards Earth Independence – Tradespace Exploration of Long-Duration Crewed Mars Surface System Architectures

Dry Reforming: A Unique Flowsheet for Fuel Production on Mars

Mars_B4_Moon

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Registered: 2006-03-23

Posts: 9,776

Re: In-Situ Propellant Production, design a opensource demonstrator

Methanol an alternative biofuel or source of plastic and clothing?  a fuel for internal combustion engines

Engineers Want to Make Methanol by Pulling Carbon Right Out of the Air
https://www.universetoday.com/163200/en … f-the-air/

It’s used as a solvent, a pesticide, and in combination with other chemicals in the manufacture of plastic, clothing, plywood, and in pharmaceuticals and agrochemicals.

Last edited by Mars_B4_Moon (2023-09-16 07:08:17)

tahanson43206

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Registered: 2018-04-27

Posts: 19,363

Re: In-Situ Propellant Production, design a opensource demonstrator

For Mars_B_Moon re # 107

Thanks for the link to the story (written for a wide audience) on the work done with rooftop CO2 capture.

The reporter explains how a system like this is needed for extended travel beyond Earth.

As a reminder, this forum has a topic dedicated to a book on the subject of making methanol.  The book is focused upon industrial scale operations.  What I like about Professor Liu's design is it is able to operate on the much smaller scale of a single building.

A team of researchers led by Professor Xingbo Liu at Western Virginia University is working on a technology that can harness carbon from air exhausted from office buildings and use it for a more ecologically sound method of producing methanol. If successful, their system would also remove a harmful greenhouse gas.

(th)

kbd512

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Registered: 2015-01-02

Posts: 7,850

Re: In-Situ Propellant Production, design a opensource demonstrator

I don't think very many Starships are actually coming back from Mars, because the colonists need a source of high quality metals to fabricate pressurized living spaces, tools, storage tanks, and a slew of other machines that make life possible in an otherwise uninhabitable planet.  100t to 150t of total mass allocation between the colonists and their consumables won't cut it.  The Starship itself provides another 150t of mass in the form of construction materials of the highest quality, because Starships are primarily constructed from some of the finest steel Earth has to offer.  There's enough mass between the payload and rocket itself to create new homesteads on Mars.

If we're going to go to the trouble of making methanol and plastics on Mars, then we may as well make RP1 while we're at it.  A lot of the impurities from refined hydrocarbon fuels are not present in synthetic fuel equivalents.  For example, there is almost no Sulfur present in biodiesel.  If you're not going to obtain the dramatic Isp and vehicle wet mass improvements from using LH2, then RP1 is the least technologically challenging fuel to store.  Everything from piston engines to solid oxide fuel cells can burn jet fuel.  Long-term storage of cryogenic liquids is simply not done at an industrial scale.  There is an established LNG industry here on Earth to support Starship flights, but no such industry exists on Mars.  If we found Methane or oil on Mars, of course that would be a game-changer.  Mars has abundant CO2 and water, so that possibility still exists.

I don't see much point to bringing the Starships back to Earth, though.  An enormous amount of energy has to be spent to make the propellants, which could otherwise be used to create sufficient energy reserves for the fledgling colony.  The performance increase of LCH4 over RP1 is marginal at best, and has posed significant operational problems for SpaceX.  LCH4, much like LH2, it can be made to work if you spend enough money to overcome the storage and handling problems.  Since SpaceX can and does fly RP1 fueled reusable rockets here on Earth, why not use RP1 on Mars as well?

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: In-Situ Propellant Production, design a opensource demonstrator

The cargo ships are not likely to have many returns even after a decade of them arriving. The crew ships will be a different question as we do not have sufficient data for the long term reduced gravity on man. So, to err on the side of caution until we have that few cycles of going and returning, we will not know.