Current Settings

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).

The Questions

  1. 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)?
  2. How much people could human send to space within just six years, assuming that tech would be advancing on each launch?

Edit Notes

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.

  1. Is it possible for humans to do such that daunting tasks with our current technology? What would be major hindrances on doing that feat?
  2. 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)?
  3. 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?
  • $\begingroup$ Why the goddess of love?(cause she's hot) Do you know jealousy caused the most death ever since somebody left the Pandora box open, I know it is ironic but you should look to the god of war for blessing and perhaps prosperity at least NASA seems to agree with me! $\endgroup$
    – user6760
    Commented Mar 5, 2016 at 13:14
  • $\begingroup$ Getting them there is only like 1% of the problem. Keeping them alive on the surface Venus so that a viable colony can be established is the other 99%. $\endgroup$
    – DMfiend
    Commented Mar 5, 2016 at 13:44
  • 2
    $\begingroup$ I like your question but I think you ought to split it across three separate entries. $\endgroup$
    – Jim2B
    Commented Mar 5, 2016 at 18:06
  • 1
    $\begingroup$ Just one thing to note. Bunkers are the real solution to w/e problems you have to make the Earth no longer livable. To make Earth as unlivable as moon/mars/venus, you'd have to fuck it up to an unimaginable degree and there is no reason to think that any of those bodies would come out more favorable in the aftermath. Earth would still be more favorable for life even if an asteroid the size of a continent hit it, rendering most of the surface molten. $\endgroup$ Commented Feb 26, 2018 at 18:54
  • 1
    $\begingroup$ The cheapest way to send 2,000 humans to Venus would be to execute 2,000 humans, cremate them so that only a few pounds of ashes are left of each, and then send them in a small capsule atop a giant multi stage booster rocket to eventually be scattered in the atmosphere of Venus. That should only cost a billion dollars or so. Why anyone would want to do is is unknown. $\endgroup$ Commented Apr 1, 2018 at 16:43

5 Answers 5


Given your lift requirements there's only one possible approach: Orion. You don't care about Earth, the fallout generated is of no concern.

I think it's doomed to failure, though, because of the Venus end of things. You have a very short time to develop your floating cities, at best you get one revision after trying one and seeing what happens. You are betting your colony on the that second version working very well indeed.

Mars is your only reasonable target.


If this was a crash project with no expenses spared, it is possible in theory.

SpaceX currently is the only rocket company building boosters on an assembly line, so their hardware can be pressed into service. Three Falcon 9 boosters strapped together make a Falcon9 Heavy, which can launch heavy payloads into orbit, including ones with powerful trans stages to get into interplanetary orbits.

Dragon capsules can hold up to seven astronauts apiece, although for trips like this, you probably want to only hold 4, both to minimize launch weight and make the on board supplies stretch out. Each Dragon will be mated in orbit with a Bigelow inflatable hab module, which provides space for the astronauts and supplies in flight. With some clever handwaving, it may be possible to gently aerobrake the Bigelow modules and have them eventually come to a stop floating in the Venesian atmosphere like giant balloons.

The problem is "now what?"

Unlike the colonists who escaped to the Moon, Mars or the asteroid belt, the colonists on Venus are trapped. Any resources they need will have to be "mined" from the atmosphere, which is Carbon Dioxide with a smattering of water vapour and sulphuric acid. Mineral resources are hidden miles below under a hellish 90 atmospheres of pressure, temperatures similar to the interior of a self cleaning oven and under the gravity field of a planet similar in size to Earth.

In contrast, the other colonists have access to a wide range of resources, including water, and are on bodies which only require a small amount of energy to enter orbit and escape to interplanetary space. Venesians will be like people trapped aboard a balloon; they can actually see the ground below and all the resources, but have no means of getting there to replenish the piknick baskets they brought with them (and current technology will not allow them to bring anything to Venus that they can use or adapt for surface mining, much less boosting it back into orbit).

So Venus may be a target for exploitation in the centuries to come (skimming the atmosphere will provide lots of CO2 to use as feedstock for making artificial diamonds and grapheme for industry), but this will require a mature infrastructure to be developed in space, and plenty of R&D as well.

Head to Mars, young man.

  • $\begingroup$ The original idea is that they know other factions also settle on Mars and moon. Given that the first colonists bring a lot of inflatable pods, and put their main ship in orbit while reaching the inflatable habitat on the clouds using their shuttles. So supplies could be send to the orbit from other places in solar system. Isn't that provide enough motive to colonizing Venus? The gravity would be so similar to earth that further generation of humans wouldn't have weakened bones due to low gravity, and I think it would provide enough motivation for other colonies to keep sending them supplies. $\endgroup$ Commented Mar 5, 2016 at 16:04
  • $\begingroup$ @HendrikLie, I don't think it makes sense in your timeframe. The launch capacity from Earth won't even remotely fill the available space on Mars or Luna. Perhaps Venus habitats are in the plans, one or two generations later, but for the beginning it is just too hostile, even compared to places like Mars or Luna. $\endgroup$
    – o.m.
    Commented Mar 5, 2016 at 20:22
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    $\begingroup$ Since getting too and from Venus will be about as energetically difficult as getting to and from Earth, this will be quite expensive. For colonists in the Asteroids, they can create rotating habs which can simulate Earth gravity, and still gain the economic benefits of cheap access to resources and low deltaV cost to move material and people around the solar system. $\endgroup$
    – Thucydides
    Commented Mar 6, 2016 at 2:47
  • $\begingroup$ @Hendrik Lie, I've seen you reference "weakened bones", but that's only in the context of earth gravity. In a lighter gravity situation, would they really be considered "weak" for that environment? $\endgroup$
    – Marky
    Commented Mar 7, 2016 at 18:50
  • $\begingroup$ Well, yes, I just realized it. Venus high gravity makes it as hard to escape from it as it is from earth to space. I think asteroid is the viable option as of now, as it is on moon. $\endgroup$ Commented Mar 8, 2016 at 1:05

Yes, but ...

I have faith that mankind could pull it off, if it becomes a top priority effort and if society doesn't unravel before the mission can launch.

  • What percentage of global GDP goes into the preparations?
  • What is an acceptable casualty rate en route, provided enough colonists arrive at the destination?

In the scenario you posed, both answers might be "a lot." We should be able to put a Soyuz-style capsule on various 20th-century-style rockets. SpaceX still has problems with the landing, but in your scenario most passengers and cargo go up, not down. Both should be able to greatly increase the production rate if quality control takes second place to speed.

While the surface-to-orbit infrastructure is expanded somebody comes up with a quick and dirty design for an one-way spacecraft. Perhaps something like the ISS, except for an engine and fuel tanks at one end and docks for landers at the other end. Either a conventional chemical rocket or a crude nuclear rocket. Start designing both, as an insurance policy that one of the craft proves impractical.

Don't build one ship for 200 people, build 20 ships for 20 people each and hope that at least half will arive. Those who die on ships with non-redundant life support and untested designs would have died on Earth, too. What do they have to loose?

The main technical problem I see are the lander and the Venus habitats. For that reason, I believe that Mars is a much better option for your timeframe.

An even bigger problem is how you keep society from crumbling while the disaster comes nearer. How do you convince somebody to fuel the last ship out if they have no ticket?

  • $\begingroup$ Basically that means rather than sending large monolithic ship, send as many small ships as possible? I have to agree with problems involved in deploying floating platform for them to live in. At maximum a floating platform would not be able to hold hundreds of people. $\endgroup$ Commented Mar 5, 2016 at 14:50
  • $\begingroup$ Too many separate ships become inefficient and unable to survive. Each ship needs an engineer, a surgeon, etc. But the colonists definitely don't want to put all of their eggs into one basket, either. And the chance for survival will be greatly enhanced if the first colonists arrive before the last colonists (and the last supplies) depart. Such a hurried plan would be bound for forget something. Think of the first wave as the lab rats. $\endgroup$
    – o.m.
    Commented Mar 5, 2016 at 15:00
  • $\begingroup$ I was considering the fact that we could reach Venus faster than travel to Mars. But, oh well, haven't considered floating infrastructure required to hold 2k individuals. $\endgroup$ Commented Mar 5, 2016 at 15:01
  • $\begingroup$ I think I would consider them. First colonist are important to deploy infrastructures required for further colonists. I think the first colonists would bring with them a lot of deployable floating platforms. I think that they are not descending their ships directly, instead they'd use their ship as orbital platforms and deploy smaller inflatable pods to the atmosphere, then reach it using shuttles. That way they could manufacture more pods using resources send on Venus orbit from elsewhere in solar system, instead of manufacturing them on the floating platform. $\endgroup$ Commented Mar 5, 2016 at 15:14

It depends what you mean by 2000+ people

If you want to save humanity (but not many humans) the easier is to sent a ship with a few women and 2000+ frozen embryo. You just need to send enough people to maintain the base.
One key reason is that you will be travelling quite close from the sun. To make a lead protection for a small fridge is no big deal. Most passengers may die of cancer a few year after arrival but they will breed sound children before that (hence the point of sending only women).
Note this paradox: The first colonist will have no descendants. Unless some of the embryo are theirs.

The way you describe the situation: send as much resources as you can on the moon, then take needed time to send to Venus.
The plan I describe probably allow to send a first ship before the 6 year deadline, but as o.m. suggest, send several ship is safer

By the way, a big problem in the Venus plan is: if links with earth are severed, where can you mine material to expand/maintain your floating colony?
There is no way a few people entrapped in some balloon with few tools and no material could build shuttle and miner robot.
If you still can access the Moon, then OK. If not, Mars is a better plan. But if the Moon is accessible, there is no real emergency to reach for Venus.

  • $\begingroup$ Well, I think it's just earthen civilizations is split at the time, with various factors being considered, and some parties are convinced to invest on Venus colonization, while others convinced to moon and Mars. $\endgroup$ Commented Mar 5, 2016 at 14:53
  • $\begingroup$ Also, I like your idea of using women and frozen embryos. But still they have to have maintainers of colony, therefore a handful of crew are required to operate the colony I think? $\endgroup$ Commented Mar 5, 2016 at 14:55
  • $\begingroup$ True. You need to send enough to maintain a base. If you had more time, you could make a "perfect" base with robotic maintenance. Embryo mean you don't have to be scared of consanguinity. And you can "pay" millions of worker by sending their children $\endgroup$
    – Madlozoz
    Commented Mar 5, 2016 at 16:15
  • $\begingroup$ So send all the women to Venus. Does that mean you send the men to Mars? $\endgroup$ Commented Mar 8, 2016 at 2:45
  • $\begingroup$ Sorry guys: you are just not needed. Depending on the situation and requirement, I'll sent women and/or mining robot only on $\endgroup$
    – Madlozoz
    Commented Mar 8, 2016 at 13:46

I think long term survival is a near zero probability. No system is lossless. What you have is a society that most likely cannot replenish in the quantity necessary, the essentials for life. In addition to having to build a large number of small ships or small numbers of large ships, they have to build floating cities capable of reliably withstanding the conditions of a Venusian atmosphere. One little potato famine and everyone dies. Venus doesn't have an appreciable magnetic field so there would be no protection from charged particles. Something has to be developed to extract water from the atmosphere. The people need a constant supply of breathable air which also must be scrubbed, plus all of the things others have mentioned. But most importantly this all has to be designed, built and deployed in just 12 years.

I don't want to rain on your parade, but if it's not important to the plot, I would gloss over HOW they did it. If you want to explain it or add realistic details I think it would be important to add some kind of pressure relief here, like more time, a secret project that had actually been working on it for decades, some source for external supplies, a shorter life expectancy, something that would help make this more plausible.

I hope this helps.

  • $\begingroup$ This, somehow, helps me in some considerations. So upvoted $\endgroup$ Commented Jun 14, 2016 at 3:32

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