Heyo! This was an old obsession of mine! Here goes...
So, radiation: Yes, and no.
Some shielding would be required, but not a whole lot. Using lead is a bad idea; it's a lot of dead weight you'd need to haul from Earth or mine on Mars. But first, the trip there. As mfb pointed out, this really isn't that bad.
I think smoking is actually much more dangerous than a trip to Mars and back, in terms of increasing your chances of cancer.
mfb said:
Those [radiation exposure] limits are always arbitrary, they vary with country and occupation and can be changed.
There are inhabited places on Earth with radiation doses of about 100mSv/year. A trip to Mars without excessive shielding would exceed that, but just for 2-3 years, for a total dose of something like 1 Sv (number from
space.com). That would increase the risk to get cancer, but so does smoking. The other risks of such a trip are probably much more dangerous.
If you want to stay there for a lifetime, you certainly want some shielding.
[...]
One idea I like for radiation shielding once you're there, may be to simply pack dirt up against the side of your habitats. Martian dirt is free, and all you need to move it around is a shovel. That way you can still have windows, and the shielding is more than sufficient if you do it right.
http://www.examiner.com/images/blog/EXID21670/images/776px-Concept_Mars_colony.jpg
You'll notice that most artist depictions' and NASA renditions of Mars colonies don't have any shielding, though. Truth be told, you'd need to stay on Mars for 3 years to reach NASA's career radiation dose limits. So for something like a research base where the crew changes out every launch window or two, no radiation shielding would be necessary at all, apart from the structure's walls, and perhaps a special "storm shelter" for Solar Proton Events.
*For conjunction-class missions, surface stay duration is around a year, give or take. The entire trip would be in the ballpark of 2 years, with about 6-8 months each way.
**I'm pulling that bit about radiation from
here, and decided to do some digging and wound up http://www.nasa.gov/centers/johnson/slsd/about/divisions/hacd/hrp/space-radiation-pubs2.html then
here. How do I actually get to the paper itself?
As for temperature; you feel cold when its cold outside because the ground and air conduct heat from your body. The air is extremely thin on Mars; for our purposes here, virtually non-existent. So in terms of air temperature, taking a walk on Mars would be more or less identical to a spacewalk (aka, an Extra-Vehicular Activity, or EVA) in Low Earth Orbit (LEO) (except the sun won't be as intense, so it'd actually be a bit easier. EVA suits for LEO have to work day and night, in and out of the sun. For Mars, the range of temperatures would be less extreme since it wouldn't get as hot).
As for the ground... Yes, that will be cold. But not
too cold. The temperatures there are very easily handlable with some good insulative materials, which you need a lot of in aerospace, anyways. It's really not that big of a problem; it's something engineers face with every spacecraft they build and launch; and often a few inches of very lightweight insulation would be far more than enough.
*Controlling the temperature of something in a vacuum is a surprisingly precise balancing act. You must insulate it so its heat doesn't all leak out by thermal radiation (the warmth you feel radiating from a hot stove, for example, is thermal radiation), and control how much you radiate out so too much heat doesn't build up
in your insulation from things that produce waste heat like human beings, computers, engines, life support devices, etc. Spacecraft generally have specialized heat radiators for this purpose, that can radiate a variable amount of heat to keep the craft at the right temperature.
In fact, the Space Shuttle's cargo bay doors are lined with heat radiators - that's what the reflective material is - aluminum with tubes running through it of coolant, wrapped in mylar. They're essentially air conditioners, but instead of using fans like air conditioners for your house would, they use thermal radiation (I think they even use Freon, iirc!). If the cargo bay doors were to jam, the shuttle would have to have pulled an emergency abort back to Earth.
Other things that were brought up:
Water:
http://phoenix.lpl.arizona.edu/edu_water_ice_dirty_ice_snowcones.php
Water + RTG, fission or Solar power = Oxygen.
Soil is also rich with peroxides and nitrogen.
To filter Co2,
NASA has developed fully-reusable systems that do this. There's probably more options for systems to pick from, and better ones, but the RCRS is one that I know about, at least.
Growing food ain't no thang:
aeroponics. It's like hydroponics, but better. No soil is needed, higher yield per volume and time with less labor, and far less water consumption.
3d printer technologies are looking more and more promising if you need to make replacement parts in-situ. ISRU means you can even use that local water (which you're already getting hydrogen and oxygen from for your life support) plus some martian atmospheric Co2 to make methane+LOX fuel/oxidizer.
Better yet, you can even do this:
2H2O -> 2O2 + H2
Put that O2 somewhere else, we just need that H2, and grab some atmospheric CO2.
2H+CO2 -> C+O+H2O
in a pressurized reactor to get yourself carbon, which is oh so nice for so many things.
Ryan_m_b said:
It's worth bearing in mind that even if a method was developed to break down waste molecules for reuse those methods themselves could generate waste. Albeit less (otherwise it's a useless technology) but a 100% closed system is quite unlikely for the foreseeable future.
True, and I thought I remembered someone mentioning the failed Biosphere experiments, but I couldn't find that post when I looked again. But fortunately, we don't need a 100% closed system for the reasons I listed. We only need it to be very efficient, and although I can't quote for sure, I think the level of efficiency present on the ISS is actually about enough. Although, of course, I guess that depends on how quickly you can extract resources from the Martian environment.
Mars is about as lush for us, with our current technology, as the colonial Americas were for the early colonists' technology. More so, I'd say, actually, since we wouldn't have to worry about disease and the cold of winter in the ways that they had to. Or hostile natives, heh. The big difference in-between us and them is that they had a real strong incentive to go and colonize the Americas. Natural resources/colonialism, and religious freedom, as I understand it. Interesting to me it is, that it wasn't until hundreds of years after the first explorers sailed there that colonies - or even the motivations for those colonists to go - appeared.
Our technological nearness to being able to settle there (I'd say we're much, much closer to that, than we were to landing on the moon in 1959!) and lack of colony might be somewhat analogous to that span of time in-between the first explorers finding America and the colonies appearing there, if not only very roughly so - I'm really no historian at all.
Thing is, I'm very hopeful about Mars colonization. As Robert Zubrin put it, in the ancient days before the world was explored, it was common to draw fearsome dragons on maps in unknown lands, and put "there be dragons," and other fears of the unknown, fears of doing what hasn't been done before.
Radiation, temperature, low gravity... All of these things are managable, but a lot of people go on as if they're show-stoppers. "There be dragons." In truth, we could have built a Mars colony in the 80's with "Mars Direct." The only reason we didn't was a lack of political drive or unity in NASA.
I'm very hopeful SpaceX will live up to its ambition to have one there by 2035. They've been doing an awful lot of "impossible things" in the aerospace industry already, like lowering the price of spaceflight to where some companies think it'll be profitable to mine asteroids. I think they'll pull through. I'm not so sure about the 2035 deadline, but I'm certain by 2050 there'll be people on Mars.
EDIT: I suppose ultimately, though, we can only conjecture about how easy/close we are, but I don't think anyone can really say for certain until some group, perhaps SpaceX, actually develops the In-Situ Resource Utilization (ISRU) technologies and proves they can work at a rate to make up for inefficiencies in recycling in test facilities here on Earth (Something I should note that Robert Zubrin and a few colleagues - not a single of whom were chemists or chemical engineers, but aerospace engineers - did to prove that CH4/LOX could be produced from Martian resources at an acceptable rate. iirc, they did it fairly quickly and without too much effort).
But my educated guess is; it's going to be easier than a lot of people make it out to be. Not
easy by any means, but not harder than the really amazing stuff SpaceX has done already, and certainly, by a far cry, not nearly as hard as landing on the Moon was in 1959.
