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Swift
2006-Nov-03, 02:39 PM
I came across this journal article in one of my chemistry journals and I thought people here might be interested. I can't link to the whole article (you have to pay for that), but the title and abstract are below, with a link.

Microreactor development for Martian in situ propellant production
Catalysis Today
Volume 120, Issue 1 , 30 January 2007, Pages 35-44
J.D. Holladaya, K.P. Brooksa, R. Wegenga, J. Hua, J. Sandersb and S. Bairdb
Pacific Northwest National Laboratories, P.O. Box 999, Richland, WA 99354, USA
NASA Johnson Space Center Houston, TX, USA

Abstract
A process is presented for in situ resource utilization of indigenous resources on Mars to produce hydrocarbon propellants using microchannel reactors. The proposed system utilizes CO2 from the atmosphere on Mars and hydrogen brought from Earth. The CO2 is reacted in a Sabatier reactor (SR) to produce methane (propellant) and water. The water generated is electrolyzed to produce oxygen (oxidant). The hydrogen is recycled. The microchannel SR used in this study consisted of integrated cooling and reaction channels, was <100 cm3 in volume and 175 g in mass, and used a proprietary catalyst. When operated at 400 C, 7080% CO2 conversion was achieved, which enabled 0.0125 kg CH4/h production or one-eighth the target mission-required throughput. The modular design of microchannel reactors would enable simple scale-up to full-scale production for the proposed mission. To produce the desired oxygen-to-methane ratio (3.8 by mass), a reverse water-gas-shift reactor (RWGS) converts CO2 and hydrogen to water and CO. Again, the water is electrolyzed and the hydrogen recycled; the CO is discarded. The RWGS system contained 30 microchannels in a four-reactor monolith (70 cm3). When operated at 700 C and at a contact time of 36 ms, 0.09 kg/h O2 generation (half-scale production for a sample Direct Robotic Earth Return Mission) was achieved, and 0.18 kg/h (full-scale production) was accomplished when operated at 18 ms.

LINK (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFG-4KNMB4N-4&_coverDate=01%2F30%2F2007&_alid=480578891&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5226&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=981ce861cd0fe11f2de5d6f024f37a8f)

Instead of bringing hydrogen from Earth, as stated in the abstract, I wonder if you could take water (from the ice caps, for example) and split it to hydrogen and oxygen, either thermally (nuclear reactor) or photoelectrochemically?

selden
2006-Nov-03, 05:11 PM
Note that it says that the hydrogen is recycled. I suspect the mass of the hydrogen and its tanks that would be needed to be carried to Mars would be less than the mass of the equipment that would be needed to extract it from local resources.

Laguna
2006-Nov-03, 07:06 PM
Note that it says that the hydrogen is recycled. I suspect the mass of the hydrogen and its tanks that would be needed to be carried to Mars would be less than the mass of the equipment that would be needed to extract it from local resources.
Only the hydrogen of the produced water is recycled. The hydogen used to produce methane is not.

Edit: I see, the methane is used resulting in CO2 and Water, where the hydrogen is again recycled.
So, forget this post.

galacsi
2006-Nov-03, 09:03 PM
Only the hydrogen of the produced water is recycled. The hydogen used to produce methane is not.

Edit: I see, the methane is used resulting in CO2 and Water, where the hydrogen is again recycled.
So, forget this post.

No you were right ! Water is electrolysed giving oxygen to be liquefied and stored and hydrogen to start the cycle again . IN each cycle half hydrogen is combined to carbon to give methane and half is recycled in the form of water.

JustAFriend
2006-Nov-05, 08:44 PM
It might be more economically viable to find a cometary or asteroidal or Saturn source of hydrogen and oxygen, then tug it into Martian orbit and crack it there....

Ronald Brak
2006-Nov-05, 09:13 PM
Hmmm, here's an idea. drop a lander on top of Olympus Mons that gather's samples. The orbiter goes into a highly eliptical orbit that dips into the tenuous upper atmosphere at the peak of Olympus Mons and catches the samples with hook and takes it to earth. (I realize this is not exactly easy or practical.)