|
Post by nerd1000 on Oct 26, 2016 9:46:32 GMT
Don't forget to keep it frictionless, too! Well, the PTFE is on the materials list for a reason. Funny, I thought it was so I could barbecue spherical beef on my radiators without using excessive amounts of oil.
|
|
|
Post by argonbalt on Oct 26, 2016 14:37:17 GMT
So, under an ideal circumstances, 1 mole of water makes 1 mole of H2 for 285 kj. The sabatier process actually needs 4 moles of H2 per mole of CO2, so about a total of 1.14 MJ. You then mix those 4 moles of H2 plus a mole of CO2 for 1 mole of Methane plus about 165 kj of energy, which might partially be able to offset energy costs, but probably not all that much. So, 1 kg of Methane would be (1,000/16) 62.5 moles, which would require (62.5x4)=250 moles of H2, or close to 500 grams. But, as your link shows, that's inefficient since your actually making two water molecules for every methane molecule. By reusing the water molucules, you can reduce your need to two H2 per methane. Thus, you would only need 125 moles of H2 per Kg of Methane, about 250 grams of H2. So, assuming you had a source of H2 available, you could make 1 kg of methane on mars using 500 g of H2 and require basically no energy, or make 1 kg out of 250g of H2 if you were willing to spend some 318 kj per mole of methane, or about 2 MJ of energy per kg. This is if you have H2 already available. If you need to produce H2 initially from water, that would seem to add some 3.6 MJ per kg if your reusing the water generated. So, from scratch, it looks like you would need about 6 MJ of energy to make 1 kg of methane. Lets round up, somewhat arbitrarily, to 10 MJ in actual practice. So, if you had a 4 GWatt powerplant dedicated solely to making Methane, it could theoretically make 400 kg a second. Over a day, that would be 35,000 tonnes a day at full output. Now, the next question would be, how much production do you need? Resourcing on Mars is an interesting thing, the north and southern ice caps have quite large deposits of CO2 so carbon is that would be an ideal, H2 as well is readily available as both poles have large amounts of water ice. So production sites would be in or at the least near these locations, this has the added bonus of cooling the reactors with just atmospheric ambient temperatures. As a tactical note, locating production sites at these extreme latitudes would help fortify them as orbits would have to be very specific to hit these areas. On the note of pure Methane, Mars Express detected trace amounts of Methane in the atmosphere, which is strange as UV radiation would destroy Methane as in around 300 odd years, but the average seems to be 0.6-4 years for the life of a single Methane molecule. So clearly something is destroying or dissipating the Methane very quickly, on the plus side this means that something is creating Methane at a good rate which implies underground deposits or generation of some sort,
|
|
|
Post by cuddlefish on Oct 26, 2016 17:12:20 GMT
Well, the PTFE is on the materials list for a reason. Funny, I thought it was so I could barbecue spherical beef on my radiators without using excessive amounts of oil. The best tools are multi-purpose.
|
|
|
Post by apophys on Oct 31, 2016 19:19:02 GMT
Another option would be to grow algae or other plants on Mars (probably under some domes), using the plentiful CO2 from the ice caps to make complex molecules via photosynthesis, then running the biomass through an anaerobic digester for methane. As a plus, such infrastructure would be excellent support for colonization, and probably cheaper for electricity than massing solar panels over the surface (nuclear reactors are great, but sourcing fuel for long-term installations may be troublesome; not sure about the geology of Mars or the viability of importing fuel).
Trace methane in the atmosphere makes me think of biological activity. It's possible that there are bacteria living deep underground on Mars feeding on something (and another bacterium is turning their dead remains into methane). If this is the case, we might actually discover some methane deposits under the surface with exploratory drilling.
|
|