Methane Production -- Sabatier Process

[Twark_Main]

Another chemical reaction worth noting:

Olivine (Fe,Mg)SiO4 has been reported as being a common component of Martian regolith in the form of basalts, at least in the Southern Highlands. Olivine is an igneous, ultramafic or mafic mineral that's also readily available on Earth, either in aphanitic (small crystals) form as a basalt, or phaneritic (larger crystals) as peridotite or gabbro.

The interesting part is that when olivine is mixed with H2CO3 (carbonic acid), it forms oxygen gas and water. Carbonic acid is easy to make by bubbling CO2 through water. The reaction would allow you to recycle the water, while also generating oxygen. Should take a lot less energy than electrolysis.

The downside is that you still need hydrogen for the Sabatier process, which suggests olivine might be best used as a secondary oxygen source -- but even in that role, it could still be very useful.

That's interesting; if you could find methane on Mars, it might be the cheap way to get oxygen to go with it?
However, a bit of digging suggest the rate may be quite slow, and the amount of carbonic acid held in water quite small?  Catalysts perhaps?  This does sound a bit too magical, if it was that simple, there would be no CO2 problem and therefore no global warming problem....

No magic. There does exist a proposal to combat climate change by artificially accelerating the weathering rate of olivine. https://projectvesta.org/

[Joseph Peterson]

Here are two technical points about electrolysis stacks that I have previously discussed in other threads linked above.

Water for the electrolysis stack needs to be purified.  Most companies trying to sell electrolysis stacks do so with a eye to hydrogen being the final product.  These use reverse osmosis for water purification.  Since our hydrogen is fed into a Sabatier reactor, an exothermic process, waste heat can be used for distillation, saving a lot of complexity.

Most companies trying to sell electrolysis stacks use a chiller system to ensure only hydrogen exits the hydrogen side of the electrolysis system.  As far as I can tell this is because chillers are the way we've always done it.  A simpler and cheaper option is to use membranes[1] to purify the hydrogen and metal hydrides[2] for pressurization and storage.

[1] http://www.tanaka-europe.eu/products/equipment-measuring-devices/palladium-membrane-for-hydrogen-purification/
[2] https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-storage/metal-hydrides

[Genial Precis]

Silly basic questions here. There are clearly deposits of mostly-water at the poles, but if you want to use solar power you definitely don't want to be at the poles. Are there known deposits of high-quality "water ore" at latitudes with reasonable insolation? If not, what are some options if you want to extract water from some lower-quality ore such as a hydrate mineral, and are there some reasonable deposits of those near the equator? I've done a little research but not found anything clear-cut on these issues.

[Mark K]

Silly basic questions here. There are clearly deposits of mostly-water at the poles, but if you want to use solar power you definitely don't want to be at the poles. Are there known deposits of high-quality "water ore" at latitudes with reasonable insolation? If not, what are some options if you want to extract water from some lower-quality ore such as a hydrate mineral, and are there some reasonable deposits of those near the equator? I've done a little research but not found anything clear-cut on these issues.

High areas around the poles are where you definitely want to be for Solar Power on the moon. You get better than every other fortnight insolation. If you are very near the pole only a few stations will keep you having one always in Sun and there is no air to attenuate at low angle.

[Genial Precis]

High areas around the poles are where you definitely want to be for Solar Power on the moon. You get better than every other fortnight insolation. If you are very near the pole only a few stations will keep you having one always in Sun and there is no air to attenuate at low angle.

Uh, I was asking about Mars. TBH putting solar panels on the moon sounds silly, in the long run. The moon is super dusty, and it's relatively easy to ship things in and out of lunar orbit with various fixed installations, so it's probably more cost-effective to put solar panels in orbit and beam power down as soon as you get to a large enough scale to support launch infrastructure.

[high road]

If you think the moon is so dusty it would reduce overall solar power effectiveness by more than the 40% you lose by SBSP power conversions, why would you go with solar power on Mars? Plenty of dust + an atmosphere to carry it.

However, a methane plant on the moon would need a source of carbon dioxide

[Genial Precis]

The moon doesn't have winds to blow dust around, but that's OK because the dust electrostatically levitates! There's a carpet of hovering dust on the moon, and it clings to everything because there's no atmosphere to dissipate charges. You have to account for the dust on Luna and Mars.

If you can easily put things in orbit around the moon, and at a certain scale of settlement this could well be the case, it might be cheaper per unit delivered power to eat the inefficiency and put more solar panels in a dust-free environment. Especially since the solar panels in orbit can produce most of the time, so 60% transmission losses is not such a big hit.

Oviously I don't know if this works out, but there you have it.

[LMT]

...a methane plant on the moon would need a source of carbon dioxide

Some useful carbon source, yes:  e.g., potential endogenous and exogenous sources for carbonaceous lunar ices.

Lunar ice is OT in Mars context; still, refinery methods could be much the same, especially if CO2-rich clathrate is present in martian ice.

[sdsds]

Regarding the off-the-shelf cake mixer they use in their Sabatier process: "We voided the warranty pretty thoroughly."

https://twitter.com/freethinkmedia/status/1895193498107916772

[Slarty1080]

I’ve thought for years that SpaceX would be wise to start testing sabatier hardware by making their own fuel for Raptor and SS/SH.

Get some solar panels from Tesla build a couple reactors and start will some veto tanks at the launch sites.

Yes, absolutely! There's no reason basic reactor flow and function shouldn't be ironed out on Earth long before use on Mars. Issues such as operating at scale are likely to present significant engineering challenges.

Testing will definitely be required for the specifics on Mars, but the basic chemistry and the process is very well known in the chemical industry it's gas light era technology and not something exotic. The main challenges will be in getting a good supply of pure water and enough power for electrolysis. The reaction itself is exothermic so will be self sustaining.