Author Topic: Making Liquid Methane on the Moon  (Read 6353 times)

Offline Rocket Surgeon

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Making Liquid Methane on the Moon
« on: 07/02/2018 04:37 AM »
So for a number of reasons, but mainly as a way of refuelling the BFR, I've been trying to find out what sort of Carbon Dioxide and/or other sources of Carbon are available on the Moon for making Liquid Methane/Liquid Oxygen (Methalox) Fuel.

We generally know that there is water ice in the Polar Craters, which could be used to make Hydrolox Fuel, but is there a decent source of carbon for making Methalox? I would expect that the same mechanism for water arriving on the poles (asteroids hitting and making permanently shadowed craters) would also work for Carbon Dioxide as well as water, and that Carbon Dioxide can generally be found on comets and asteroids.

The reason I ask is that I believe this will help define which fuel ends up being dominant in the future. Regardless of the benefits/draw backs of Hydrolox vs. Methalox, if you can't make Methane, than Liquid Hydrogen wins by default.

Offline ncb1397

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Re: Making Liquid Methane on the Moon
« Reply #1 on: 07/02/2018 04:43 AM »
Quote
LCROSS is fascinating not just due to water on the Moon, less
controversial by 2009, but other substances: 5.7% carbon monoxide, 1.4%
molecular hydrogen, 1.6% calcium, 1.2% mercury, 0.4% magnesium.
Sulfur is detected as hydrogen sulfide (H2S) and SO2, at levels 1/6th and
1/30th of water, respectively. Nitrogen is seen within ammonia (NH3), at
1/16th water’s abundance. Trace amounts (less than 1/30th of water) are
detected for ethane (C2H4), CO2, methanol (CH3OH), methane (CH4) and
OH. [62] Volatiles compose at least one-tenth of the soil mass. The
poles differ radically from any part of the Moon we have visited or
sampled.
https://arxiv.org/ftp/arxiv/papers/1205/1205.5597.pdf

Offline Rocket Surgeon

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Re: Making Liquid Methane on the Moon
« Reply #2 on: 07/02/2018 05:25 AM »
Quote
LCROSS is fascinating not just due to water on the Moon, less
controversial by 2009, but other substances: 5.7% carbon monoxide, 1.4%
molecular hydrogen, 1.6% calcium, 1.2% mercury, 0.4% magnesium.
Sulfur is detected as hydrogen sulfide (H2S) and SO2, at levels 1/6th and
1/30th of water, respectively. Nitrogen is seen within ammonia (NH3), at
1/16th water’s abundance. Trace amounts (less than 1/30th of water) are
detected for ethane (C2H4), CO2, methanol (CH3OH), methane (CH4) and
OH. [62] Volatiles compose at least one-tenth of the soil mass. The
poles differ radically from any part of the Moon we have visited or
sampled.
https://arxiv.org/ftp/arxiv/papers/1205/1205.5597.pdf

Oh wow! Thanks!

So from LCROSS it looks like Carbon Monoxide is just as, if not slightly more, abundant than water in shadowed craters at 5.7% by weight as oppose to 5.6% for water. Along with other Carbon rich chemicals in trace amounts.

So if these ratios hold generally true for similar regions on the Moon, it should be of a similar difficulty to make Methalox fuel on the Moon as it is on Mars, allowing for refuelling from local fuels and even exports back to LEO!

Thanks again!

Offline johnfwhitesell

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Re: Making Liquid Methane on the Moon
« Reply #3 on: 07/02/2018 05:43 AM »
So if these ratios hold generally true for similar regions on the Moon, it should be of a similar difficulty to make Methalox fuel on the Moon as it is on Mars,

I dont think that pulling carbon and water from sandy dirt is going to be as easy as the Sabatier process.

Offline Rocket Surgeon

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Re: Making Liquid Methane on the Moon
« Reply #4 on: 07/02/2018 05:45 AM »
So if these ratios hold generally true for similar regions on the Moon, it should be of a similar difficulty to make Methalox fuel on the Moon as it is on Mars,

I dont think that pulling carbon and water from sandy dirt is going to be as easy as the Sabatier process.

Hmmm, good point, but if they are there in the right quantities, it could be as easy as heating the soil to different temperatures using solar furnaces and siphoning off what you need. Still harder than just pulling in CO2 from the air, but easier than having to import carbon.

Offline ncb1397

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Re: Making Liquid Methane on the Moon
« Reply #5 on: 07/02/2018 06:00 AM »
So if these ratios hold generally true for similar regions on the Moon, it should be of a similar difficulty to make Methalox fuel on the Moon as it is on Mars,

I dont think that pulling carbon and water from sandy dirt is going to be as easy as the Sabatier process.

Hmmm, good point, but if they are there in the right quantities, it could be as easy as heating the soil to different temperatures using solar furnaces and siphoning off what you need. Still harder than just pulling in CO2 from the air, but easier than having to import carbon.

You don't need a solar furnace. Just simply moving the material from the crater will create an atmosphere within a pressure vessel. Crushing any rocks is advised as gases will expand from the inside...potentially causing projectiles. The carbon monoxide can be burned with oxygen from the very common aluminum oxides(or water) to generate carbon dioxide. From there, the process is the same as martian methalox production using the Sebatier reaction. This is assuming you can't find some rich deposit of Methane/CO2 to simply the process.
« Last Edit: 07/02/2018 06:05 AM by ncb1397 »

Offline Spaniard

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Re: Making Liquid Methane on the Moon
« Reply #6 on: 07/02/2018 06:35 AM »
Polar craters are a very small zones inside the Moon. so we can exhaust the deposits quickly if we try to build exponential infrastructure.

It's logical at the beginning, but I don't see too much future in a industrialized solar system.

It's different if we see as oxygen, aluminium, silicium and other abundant elements. So abundant that we could ignore long term depletion.

I hope we discover that there is a lot more reserves underground. Moon should have underground freezing temperatures up to a significant depth, and enough pressure to maintain the reserves as solid.

With enough reserves, the projection of future resource use grown a lot.

In any case, I think that non-maneed transport will be mostly sustained a lot more in non-fueled ways of transport, like lunar elevator to orbit, laser sails and other similar concepts.

If we will go to manage civilization level of moving mass, we can amortize a lot of infrastructure. I guess that avoid mass use will turn into savings on long term. When you move high volumes of raw elements, local reserves allow to use slow but cheaper routes to move mass.

Offline Lar

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Re: Making Liquid Methane on the Moon
« Reply #7 on: 07/02/2018 07:10 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline Rocket Surgeon

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Re: Making Liquid Methane on the Moon
« Reply #8 on: 07/02/2018 10:22 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

Offline ncb1397

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Re: Making Liquid Methane on the Moon
« Reply #9 on: 07/02/2018 10:25 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

I haven't found anything with a quick google search, but you would imagine it has to do with using a hydrolox upper stage as your impactor. It was a super cheap experiment measured in tens of millions of dollars. I more scientific test would use a solid brick of whatever pure metal.
« Last Edit: 07/02/2018 10:27 PM by ncb1397 »

Offline Rocket Surgeon

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Re: Making Liquid Methane on the Moon
« Reply #10 on: 07/02/2018 11:16 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

I haven't found anything with a quick google search, but you would imagine it has to do with using a hydrolox upper stage as your impactor. It was a super cheap experiment measured in tens of millions of dollars. I more scientific test would use a solid brick of whatever pure metal.

True, but the impact threw up an estimated 10,000 tonnes of regolith and 5,000 tonnes of that was analysed spectrally, so 2.5 tonnes of aluminium, electronics, waste Hydolox and etc. would be fairly trace to all that, about .05%.

Another problem with the analysis from my questions perspective at least, was that fact that the site was specifically chosen for looking for water, not carbon as well for making Liquid Methane. I feel it highlights that, at least conceptually, making Methalox Fuel from local resources on the Moon is possible. Maybe not as easy as Mars, but still it probably won't require the import of Carbon.

This means that the question of Hydrolox/Methalox for a transport infrastructure is more down to details of ISP and production ease vs. mass ratio, re-usability, and store-ability, not availability.
« Last Edit: 07/03/2018 05:56 AM by Rocket Surgeon »

Offline Hop_David

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Re: Making Liquid Methane on the Moon
« Reply #11 on: 07/04/2018 07:48 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

In the September 23 issue of Science the LCROSS team published a correction that they had over estimated volatile percentages in the ejecta by a factor of 5.5.. The page in question seems to be behind a paywall.

http://science.sciencemag.org/content/333/6050/1703.2

Offline johnfwhitesell

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Re: Making Liquid Methane on the Moon
« Reply #12 on: 07/05/2018 12:28 AM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

In the September 23 issue of Science the LCROSS team published a correction that they had over estimated volatile percentages in the ejecta by a factor of 5.5.. The page in question seems to be behind a paywall.

http://science.sciencemag.org/content/333/6050/1703.2


Offline A_M_Swallow

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Re: Making Liquid Methane on the Moon
« Reply #13 on: 07/05/2018 08:15 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

In the September 23 issue of Science the LCROSS team published a correction that they had over estimated volatile percentages in the ejecta by a factor of 5.5.. The page in question seems to be behind a paywall.

http://science.sciencemag.org/content/333/6050/1703.2

We need to send resource prospecting rovers to find out what is there and in what quantities.

Offline turbopumpfeedback2

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Re: Making Liquid Methane on the Moon
« Reply #14 on: 07/05/2018 10:04 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

In the September 23 issue of Science the LCROSS team published a correction that they had over estimated volatile percentages in the ejecta by a factor of 5.5.. The page in question seems to be behind a paywall.

http://science.sciencemag.org/content/333/6050/1703.2


Although the paper about water 5% water:
http://science.sciencemag.org/content/330/6003/463.full
does not have any errata, my confidence in this results is very much shaken.

So LCROSS is yet another mission on the list of ambiguous water detection missions.
I trust they detected water, but they could be a magnitude off about the water concentration.

So until there are rovers digging the poles we will not have any idea how much water or other volatiles are really there.

Offline Rocket Surgeon

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Re: Making Liquid Methane on the Moon
« Reply #15 on: 07/05/2018 10:55 PM »
I seem to recall that there is some controversy about the LCROSS results. They may not be valid or widely applicable so caution is suggested.

Hmmm okay, do you remember what part was disputed? Was it the entire result, or more the specific ratios?

In the September 23 issue of Science the LCROSS team published a correction that they had over estimated volatile percentages in the ejecta by a factor of 5.5.. The page in question seems to be behind a paywall.

http://science.sciencemag.org/content/333/6050/1703.2


Although the paper about water 5% water:
http://science.sciencemag.org/content/330/6003/463.full
does not have any errata, my confidence in this results is very much shaken.

So LCROSS is yet another mission on the list of ambiguous water detection missions.
I trust they detected water, but they could be a magnitude off about the water concentration.

So until there are rovers digging the poles we will not have any idea how much water or other volatiles are really there.

Looks like it. If that's the case then the next best place may very well be Deimos or a Near Earth Asteroid...or just Earth if you can get costs to LEO low enough.

Offline DougSpace

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Re: Making Liquid Methane on the Moon
« Reply #16 on: 07/13/2018 11:33 AM »
Hop is right about the 5.5 factor correction.  But I understand that it doesn’t apply to the water but to the other species.  I would really like to get a definitive list of the corrected percentages.

IF the CO comes to 5.7/5.5 then that cones to 1.0% of the regolith by mass is CO (+/-).  If one does a stoichiometric analysis of the atoms available in the volatiles, one could envision producing methane with a modest amount of extra O2 left over which could otherwise be useful.

However, I still prefer hydrolox propellant from lunar ISRU.  That carbon would be most useful at a growing base.  The hydrogen from electrolyze water could go directly into the hydrogen tank in an ACES-XEUS-like lander and so the handling difficulties of hydrogen would be minimized.  Electrolyzing and refueling a single BFR from lunar resources could take a very long time.  And the BFR’s methane could come with Earth — refueling in high Earth orbit befire coming to the Moon.

Finally, I actually believe that the BFR is overkill for the Moon.  Ideally, the base’s water and organics should be used to replace recycling losses and so relatively little is needed.  ISRU metals should also be produced fairly early on as well.  So, I imagine that within 5-10 years of the start of the base, FH-launched landers could be delivering a good amount of passengers, electronics, and certain items (e.g. copper) that cannot be easily produced on the Moon.  I don’t actually see the need to be shipping 150 tones to the lunar surface per launch.
« Last Edit: 07/13/2018 11:36 AM by DougSpace »

Offline speedevil

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Re: Making Liquid Methane on the Moon
« Reply #17 on: 07/13/2018 11:48 AM »
Hop is right about the 5.5 factor correction.  But I understand that it doesn’t apply to the water but to the other species.  I would really like to get a definitive list of the corrected percentages.

IF the CO comes to 5.7/5.5 then that cones to 1.0% of the regolith by mass is CO (+/-).  If one does a stoichiometric analysis of the atoms available in the volatiles, one could envision producing methane with a modest amount of extra O2 left over which could otherwise be useful.
CO/O2 is quite a respectable propellant, and CO has both liquid density and boiling point in the same range as methane.
The ISP is lots lower, but some 90 tons will get your BFS back to earth.

'Just' O2 alone helps a lot. An empty BFS getting to LLO needs some 50 tons propellant.
You can get 35 tons or so more payload if you only have to take methane down from LLO.

If that payload is not volume constrained, filling the rest of the ship with liquid hydrogen gives an even bigger boost, though requires an additional engine.

Offline johnfwhitesell

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Re: Making Liquid Methane on the Moon
« Reply #18 on: 07/13/2018 08:50 PM »
If you could use solar power to heat up oxygen until you have a jet with an isp of ~130 1/s you could use that to get back to earth with just the oxygen.  You'd still need some fuel for the landing part.  You'd also need 1000 tons of thrust for this which I think is more likely to be a problem.

Offline Rocket Surgeon

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Re: Making Liquid Methane on the Moon
« Reply #19 on: 07/16/2018 05:58 AM »
Hop is right about the 5.5 factor correction.  But I understand that it doesn’t apply to the water but to the other species.  I would really like to get a definitive list of the corrected percentages.

IF the CO comes to 5.7/5.5 then that cones to 1.0% of the regolith by mass is CO (+/-).  If one does a stoichiometric analysis of the atoms available in the volatiles, one could envision producing methane with a modest amount of extra O2 left over which could otherwise be useful.

However, I still prefer hydrolox propellant from lunar ISRU.  That carbon would be most useful at a growing base.  The hydrogen from electrolyze water could go directly into the hydrogen tank in an ACES-XEUS-like lander and so the handling difficulties of hydrogen would be minimized.  Electrolyzing and refueling a single BFR from lunar resources could take a very long time.  And the BFR’s methane could come with Earth — refueling in high Earth orbit befire coming to the Moon.

Finally, I actually believe that the BFR is overkill for the Moon.  Ideally, the base’s water and organics should be used to replace recycling losses and so relatively little is needed.  ISRU metals should also be produced fairly early on as well.  So, I imagine that within 5-10 years of the start of the base, FH-launched landers could be delivering a good amount of passengers, electronics, and certain items (e.g. copper) that cannot be easily produced on the Moon.  I don’t actually see the need to be shipping 150 tones to the lunar surface per launch.

This is sort of what I am trying to figure out. Alot of people do a back and forth between Hydrolox and Methalox fuel based on the higher ISP factor for one versus the better mass ratio's and generally less pain-in-the-ass factor of the other.

However, that conversation is some what moot if you can't make Methalox fuel. You'll be able to make Hydrolox where ever you take humans as you need to water, but if you need to import Carbon to make Methalox, well there are better things to be doing with that carbon like you point out.


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