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Old August 14 2013, 11:20 PM   #18
Location: Kentucky
Re: Self-sustaining Mars colony?

For available resources, energy especially, Mercury would be easier to colonize than Mars, but the delta-V is much larger. One the plus side it has a launch window every couple of months, so the two-year resupply issues go away.

Near Mercury's poles are huge ice-filled craters (its axial tilt is only about 2 degrees), and nearby, above the rims, undiminished by any atmosphere, is about 18 times more solar energy density than Mars gets. That energy flux would be there, undiminished, and available 24 hours a day by very slowly rotating the vertical-hanging collector on a tower, if you pick a spot with the right elevation. You can't do that on Mars, where the axial tilt is 25 degrees and you'd have long arctic nights to accompany a long arctic summer.

At Mars, assuming you had solar cells producing at 42% efficiency (about the maximum achieved so far), 200 square meters of solar cells would give you about 50 kilowatts and about 550 kWh/day (24 hr day). On Mercury the same installation would give you about 870 kW and 21,000 kWh/day, which is more than Mars by a factor of about 36.

This is critical because to become energy self-sufficient, and growing, the colony has to start making its own solar cells so they can expand material and crop production. So whatever PV production a Mars colony would require to support a hundred new arrivals, the Mercury colony would only have to make about 3% as many new solar cells to support the same number of immigrants. If you sent identical production facilities to each colony, and growth was purely a function of the growth in available energy, the polar Mercury colony could grow 36 times faster than the Mars colony. So if energy and food production are the limitations, the Mercury colony beats the Mars colony hands down.

And as an aside, when it comes to vehicles for transport or mining, 15 square meters (16 feet by 10 feet) of 42% efficient on-board solar cells on Mars gets you 4 to 5.5 horsepower, which is about like using a chainsaw engine to move you around, but on Mercury it would give you 50 to 110 horsepower, which is more than a Prius, Nissan Leaf, or Honda Insight. On Mercury, solar powered cars could actually travel faster than our current highway speeds.

But Mercury is going to look much like the moon instead of Arizona, so nobody seems to want to go there.
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