Humanity could no longer access earth for some reason (it could be anything from alien invasion, third world war, ecological disaster, etc) starting at 2028, and they know about this as early as 2022. They gather resources and decided to flees up from earth. Some party looks to the moon, the other one looks for Mars, and the other one looks for Venus. In this case, I prefer Venus, on which is the most earthlike (50km above the surface) to colonize. But as we know transporting humans from earth to space is hard, let alone large amount of humans. To start a new viable colony, that would be required to restart human civilization outside earth, is considered (in story) to have lower limit of between 2000 persons, up to 10,000 persons.
As far as I know (as noted in comments and answers), I have this options:
- Considering other hindrances to build floating cities on venus, but hard to obtain minerals (albeit the fact that various volatiles could be extracted from atmosphere)
- Moon, though have long term health effect of low gravity, in danger of bone density loss, protection from radiation, but closer to earth (so it might be easier to transport there than anywhere else in the solar system)
- Mars which has higher gravity than moon, but still low enough to induce bone density loss, require protection from solar radiation, and long transport time.
- Asteroids could be use as rotating habitat and benefits from low Delta V required for resource transport between colonies, and sufficient artificial gravity to combat bone density loss, but also just as hard to transport to the belt as it is to Mars (I suppose?).
- Tech level is just slightly advanced than we are now (only known physics and near future technology, so there is no instant transportation, advanced nanotechnology, or massive cloning facility yet)
- Have to quickly build large ships to bring at minimum 20 persons, and have to send a lot of them, but construction could only start at least in 2024 (a year or two to research and planning?).
- Always assume that they have to be self sustaining afterwards, assume no further contact from earth after 2028.
- Earth surface and atmosphere could be assumed that it is no longer accessible. It is not destroyed, but could not be accessed (earth orbit and the moon are still accessible though).
- Assume that there is a willing megacorporation to help with finnancial backings, or even devoting its entire wealth for saving as many humans as possible (just assume that there is one, other than actual government of nations working to save humanity).
- What is the best bet for humanity to survive tha apocalypse? Should they concentrate on a single site (planet, moon, asteroids?) to expand (and which one?), or should they spread as wide as possible througout the preferred sites (venus, the moon, mars)?
- How much people could human send to space within just six years, assuming that tech would be advancing on each launch?
I have added details and narrowing down the questions, wish it enough to make it narrow enough and answerable. Please comment on what else could be improved in this question.
Old questions, that might be too broad, but is kept for background informations (and some of existing answers are actually trying to answer this questions, just to keep it on context). Future answer must not be based on this following questions, instead answer the new one.
- Is it possible for humans to do such that daunting tasks with our current technology? What would be major hindrances on doing that feat?
- If it is possible, how early could humans begin ship construction and how long does it take to produce one ship capable to carry at least 200 colonies plus supplies plus colonization tools)?
- If it is not possible, how much man could human send to space within just six years, assuming that tech would be advancing on each launch?