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Expert: Mars Astronauts Would Lose Teeth
Ant wrote to us with a story on Discovery about the long term consequences of manned and "womanned" missions to Mars - lots of research about bone-weakening effects of zero G environments, with tooth loss high on the list.
What if they just created artificial gravity via centripetal force by simply rotating the craft about its axis on the way to Mars? I don't know the physics involved here, maybe it's just not possible to create enough gravity that way unless you have a spacecraft with a really big radius, such as the space station in 2001.
I'm sure that more-informed minds then mine have already considered this simple idea, I'm just wondering why it's not feasible.
If the manned Mars spacecraft wasn't big enough to create sufficient gravity that way, maybe they could just hire really fat astronauts, in order to make the most of the limited gravity. just kidding...
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Because the Moon, in some ways, is actually not closer to us at all, and there are a lot more things worth having on Mars when we get there.
Firstly, Mars has a day almost identical in length to Earth's. Why is this so important? Because it means you might be able to grow plants there by the natural light. Growing plants under artificial light is very inefficient - the only ones that we can afford to do so for are kind of illegal in many places :) You can't grow plants by natural light on the moon because the two-week night would kill most plants (let alone the problems of your greenhouse heating up to boiling point during the two-week day).
Secondly, Mars has almost certainly got a lot more water available than the Moon does. The moon has virtually no water available. You can't have a colony without a water supply :)
Thirdly, just because Mars is further away doesn't mean it's more difficult to get stuff to and from it. The travel time is an important issue for humans, but for cargo it often doesn't matter, and for cargo it takes *less* fuel to land stuff on Mars because you can use the Martian atmosphere to slow down when you get there, unlike the moon where you have to use more fuel slowing down. Going the other way, it's easier to get stuff off the Moon than Mars (because the moon has less gravity), but you can make rocket fuel for your rocket a lot more easily on Mars than you can on the Moon (because if you have water, you can use electrolysis to get hydrogen and oxygen - instant rocket fuel).
Finally, if you're going to run a self-sustaining colony which pays its own way, to pay for imports from Earth you need something you can export back. From what we know about the composition of the moon, we're fairly sure that there's not much there of value (except for Helium-3, which is a fuel that might be used in fusion power plants in the future but is very difficult to extract), but on Mars there's a distinct possibility of finding high-grade deposits of gold, platinum, and other commercially valuable metals. In addition, if we ever mine the asteroids (many of which are virtually pure precious metal and are thus incredibly valuable), it's much easier to supply the miners with food and supplies from Mars than from the Earth or Moon.
In any case, we're not really trying to colonize either yet. As to the interest in exploring Mars, we've been to the Moon and have a fairly good idea of what it's like. Mars is the next step along the line.
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This is the major hazard of space colonization. You have to get money from it, if you want to pay it with corporate money. And you suggest raw materials!!! I firmly believe transport costs of pure platinum from Mars would be high enough to make extraction from sea water look dirt cheap. Recycling is another thing that will not let the prices go that high. Extraction of gold from used electronics will be cheaper than importing the stuff from Mars.
Information would be cheap to transport, so prodicung it on other planets would be better. For geological/planetological research, every planet will have it's own colony, if robots are not considered better.
However, I think Moon would be the prime place for some sciences: Astronomers would love the continuous two-week data set. Radio interference from Earth would be no problem on the backside of Moon. No atmosphere means all wavelengths (IR to gamma-rays) can be studied from the Moon. Lower gravity means that the telescopes can be made larger. Some deep craters near the Lunar poles are in permanent shadow, so they would be excellent places for far infrared astronomy, where detectors must be at milliKelvin temperatures. To have a 10-K heat sink nearby will make things very easy.
Hazardous biotech research could also be done and safely tested on the Moon. It would be much harder to kill billions of people by stupid accidents.
Another possibility of the Moon is to use coilgun-like launchers that would use solar power to accelerate the cargo. This would eliminate the need for chemical propellant and rockets. Estimated launch price: less than one dollar per kilogram! As launching from Earth will never be able to compete with this, manufacturing satellites etc. could be an interesting option.
True, if you're thinking of making a great big can. That would be massive, heavy, expensive, etc. But you could just make a ship consisting of two modules - one habitation and one service, say - and tether them opposite each other to a common hub which would also contain the engines. That way you could spin them fast without having to build a great big can. Basically the ship would look like a bean can with two tetherballs attached to opposite sides.
Oh, just one more thing... in fact, you'd have to make two pairs of modules and spin them in opposite directions. Otherwise you get precession, which makes steering a bit tricky. When you arrive in Mars orbit, stop the spin, winch in the tethers, and send down the landers.
Important: make sure the tether doesn't break. Otherwise your precious astronauts go whizzing off on an eccentric orbit somewhere between Earth and Mars, out of the ecliptic plane (probably) and die. But building a 2km tether to support a 20-tonne module shouldn't be impossible. Anyone?
Also, make sure the two sides don't get out of balance. Ballast weights that can be winched up and down the tether - or just winching in or out a bit to balance the angular momenta - are best for this.