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#101 2020-07-04 20:48:30

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,708

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

Calliban wrote:
SpaceNut wrote:

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....

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#102 2020-07-04 22:55:29

Calliban
Member
From: Northern England, UK
Registered: 2019-08-18
Posts: 532

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

SpaceNut wrote:

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)


Interested in space science, engineering and technology.

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#103 2020-07-05 08:48:49

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,708

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.

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#104 2020-08-06 20:26:22

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 19,708

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/

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