We're getting into our old argument Hab vs. Dirt again, Des. It might be a good idea to relocate it so this thread can return to its original intent. It's my fault for starting the derailment.
That would depend where you get it. If you have to go all the way to the asteroid belt or the Moon for the dirt, those propellant costs will start to add up. On Mars all I have to do is walk outside with a shovel and a bag.
So propellant costs are important, but labor costs aren't? The thing with propellant is that it is irrelevant. You can use just about anything for it, including otherwise worthless shit. Not all mass is created equal, and certainly not all is in the same demand. Once you have it, you can use any amount of gravity and sunlight needed to reduce the amount of labor required, ending up with a net win.
It could be either "I" or "My faithful robot". And in space habitat construction you'd have propellant costs plus zero-gravity-labor costs, which are always higher.
Moreover, if you are willing to go to where the dirt is for planets (the Martian surface), why not go to where it is in the asteroid belt? Orbital habitats can be built anywhere. It could be Earth orbit or it could be next to that big rock in the belt.
The problem with building your habs in the belt is that you've always claimed that your goal is a solar powered habitat. The available solar power at the belt is even lower than in Mars orbit. You'd either have to move the material to a lower orbit first, which means bringing along waste material at least part of the way, risking a collision with something you care about, or build your hab (or parts of it) in outer orbit, powering all your construction equipment with more solar panels or an alternative power source, and then move it into its permanent orbit.
On a planet, all your mining, construction, and operational facilities are in one general location.
It depends on if you want to burn propellant getting people to Mars, or burn propellant getting rocks to Earth.
quite right. The good thing about people is they are self-replicating, rocks aren't.
Brick Houses are a lot easier to build than steel habitats after all.
That would be great if planetary habitats were actually brick houses. You could ignore the huge cost and up-front wait time of terraforming, but if you are doing that, it is perfectly fair to ignore the much smaller cost and much smaller wait time of building the habitat.
Well, they can
be brick houses.
Unless you change the planet's rotation. Not as impossible as would be thought.
Even more work... surely better to just pick the lucky planet (tiny little Mars) and the lucky people who can handle the differences. Hugely limiting, but avoids doing whatever you do to rotate the planet. (Burn through propellant?)
In the case of Venus (the only planet in dire need of some speed-up), you can use the ample atmosphere as your propellant and just blast it off into a solar orbit. Or you could use NTR engines to ignite it and get even more bang for your buck.
It is difficult, but not impossible, and there are payoffs to be had. Is there even enough material in the asteroid belts to build an Earth-sized habitat?
Though, you don't need to ignore the planets. You could always mine them and put their mass to good use in space.
And the people are going to commute every day from their orbital habitat? SOME people are going to have to live on Mars, and if they're going to live there, they may as well make the most use of it.
Off the planet? Absolutely. On the planet? maybe not.
You'll notice a pattern there: here on Earth, we have cracked long distance travel, but every method we use requires up front work and active maintenance to keep the environment how we want it - uniform, efficient - just like space is for free.
Of course in almost all space scenarios, you not only have to use energy to speed up, you also have to use it to slow down. Not all friction is a mortal sin.
Of course, the best part is space doesn't even need as long travel distances as Earth, since it is so much more efficient in its use of volume. It gets the inside environment it wants anywhere it wants, no need to beg the planet to play along. It uses all three dimensions as living space. All in all, it would be much more densely populated, without ever feeling like it.
Of course the moment you start spinning it you lose that advantage, at least inside the centrifuge. And maybe I don’t want to live so close to my neighbor? Some people appreciate open space, and real estate law is a lot easier in two dimensional space than three, especially a three-dimensional space that is constantly revolving about the Sun.
You have night, where the sun isn't available to you, and the atmosphere chews up even more of it. Solar power isn't cost effective on the surface of planets (not Earth, and most certainly not Mars, considering it is further out). It is in orbit. The sun provides all your energy needs.
I’ve never liked Solar power anywhere, orbit included. Give me a nice nuclear reactor any day of the week. A pound of uranium gives you the same power at 15 AU as it does at 1 AU. And with Fusion it’s even better since a lot of fusion fuels don’t decay over time, but that’s another argument we always seem to be having: Solar Power vs. Local Power.
Solar is a stepping stone to power, but it’ll never allow for sustainable expansion outside the 1AU boundary.
And the bigger problem on Mars isn’t its distance, that would be manageable, it’s the damn dust, unless you like going out every morning and cleaning off your panels.
Who says we won't learn how to control the weather by the time we terraform Mars?
Another example of the travel thing: use high technology to get what space gives you for free. Perhaps solvable, but one more disadvantage.
The fact of the matter is Mars probably offers more land area than you’ll ever be able to build out of the Main Belt. That’s more land for crops and people. To start with of course this land will be no more useful than hab land, except that on Mars you can use the partial atmosphere to reduce your building costs, and that the atmosphere and soil provide free plant food that needn’t be flown in. Once Mars is terraformed, the ability to do away with greenhouse would give groundside agriculture a big advantage. Yes, everything in a hab-farm is controllable, but that also means everything MUST be controlled.
Kay. I don't need to take my whole planet to the Stars. That's like driving my whole house down to the grocery store.
People, however, do need to move to where the market is. Look at ghost towns on Earth. People lived there, but then the economic condition dried up (sometimes blamed on random planetary weather!), and they had to move.
On Earth, that means leaving your beautiful city behind as you chase opportunities. In space, it doesn't have to.
Best off, it doesn't always require work. Consider the case of the habitat on an orbit half way between Earth and the Moon. One week it is near Earth. Next week, it is near the moon. You can alternate your visits, for free. Try that on a planet.
A fine scenario where habitats make sense, but not every operation requires such itinerant living. Again, even if you disassembled every asteroid and used every kg of material to build habitats (which is impossible since some of that material would be useless for hab building, or more valuable for other uses) you’d never equal the available space granted by Mars.
Even with the advantages of constant solar power, if you don’t have the space, you don’t have the space.
To any society of the maturity required for either extensive space habitats or planetary colonization no multi-kilometer ball of dirt will pose a threat to either. They'd see it as free resource delivery.
The big thing here is just one more option. Both could redirect or capture the asteroid. Only one has the option of moving out of the way.
Moving out of the way is only needed if you are surprised by the impactor. That would only happen as the result of a malicious action or total ignorance of orbital movements. Even with our primitive space tracking we are pretty well apprised of the movements of asteroids dangerous to the Earth.
Also, once human civilization has established another self-sustaining habitat (whether that is an orbital or groundside habitat), the threat of annihilation by asteroid is halved, and with each additional habitat that danger falls even more. Even if a whole hemisphere on Mars or an entire Island-habitat were wiped out (and that is VERY unlikely with any space faring civilization, if it were impossible to move the asteroid or the habitat in time, there would likely be enough time to evacuate the area) it wouldn’t pose that big a threat to humanity as a whole.
But with substantially reduced maintenance costs
A habitat's maintenance cost is negligible, there's really not much to it. Far more will be spent on internal affairs like road maintenance... which is a much higher cost on planets, due to the distances involved.
On a planet like Mars the road costs will actually be greatly reduced since everything will weigh 2/3rds less there, so you could either build a road to the same standard as an Earth road and it will last longer, or build it 2/3rds cheaper and it should last as long as a typical Earth road.
And in the early days the damage done by erosion will be even less since there will be no running water and the air pressure would be lower. In addition your trains will be able to go faster in the thinner air and lower gravity, giving additional benefits. Not to mention the fact that airships will probably see a lot of use on Mars, since in the CO2 dominated atmosphere there are many more useful gases beside hydrogen and helium to use as a lifting gas, including methane and oxygen.
You can’t assume that all the problems of living on Earth will follow the Martian colonists. Some old problems will follow, some new ones will arise, and some old ones will be left behind.
A minor nuisance to any space-based civilization.
Mars doesn't have to worry about it as much, but earthquakes aren't magically harmless just because you can go into space. Habitats don't have quakes at all[/quote]
I can count on one hand the number of colonizable bodies that are dangerously geological active, and at least one of those (Venus) would be more likely to see floating cities in the early stages of colonization, completely removing it from any geologic consequences.
Habitats also have to deal with challenges atmospheric bodies don’t. Again, there are pros and cons to both, and both should be explored. We can run all the models we want, but the fact of the matter is we are unlikely to know how either is run until we actually build one. And I imagine that orbital habitats and groundside habitats are likely to exist in a codependent state for some time. In order to economically mine materials for orbital habitat construction you’ll need groundside bases (asteroids or the Moon perhaps, maybe Mars for certain materials), and in order to ease transit times and provide way stations and facilitate zero-gravity manufacturing that will allow the expansion of groundside civilization the orbital habitats will come into play.
I’m not willing to dismiss either as useful. Will there be ghost towns? Certainly, but the ghost towns once served a purpose, and for them to live beyond their usefulness, they must have once had a purpose. Saying we ought not to build something because it’ll be made obsolete in 50-100 years’ time if we do is pure folly.
