# How to quickly leave a planet for another planet en mass starting out from stone age tools?

An alien race decides to test the hability of humans to survive and engage into space travel, for whatever reason.

# The planets

The aliens prepares a pair of Earth-like planets revolving around a common center of mass around a Sun-like star. The planets are very similar to Earth in mass, size and composition, and revolves around their common center of mass in almost-circular orbits, with a diamater that is twice the distance between Earth and Moon. They are not tidally locked one to the other. Lets call those planets Old Paradise and New Paradise.

Both planets are similar, and features plentiful food sources and fresh water readily usable for humans. The air is fresh. They also features a lot of natural mineral resources. The planet is covered by seas, grasslands and forests. It has plenty and diverse fauna and flora. However, dangerous or toxic bacteria and virus are absent. There is also no poisonous plants or animals. No animal or microorganism is able to live as an human parasite. No animal is more dangerous than what a dog would be. Those planets are almost like a paradise.

There are some glaciers, volcanos, deserts and very high mountains also on the planets, but those are very far from the equatorial grasslands. The climate is milder and more reliable than what is found on Earth, but there is still some danger from heavy rains, floods, landslides, lightnings and mineral toxicity. Earthquakes, tsunamis, tornados and typhoons are rare, much rarer than what happens in Earth, but they are still present and might happen occasionally.

# The humans

The humans used in the experiment all speaks the same language. They are numbered in 100 millions. Those humans are men and women with Einstein-like intelligence, all very healthy, both physically and mentally, and aged in their mid-20s. They are also perfectly able to have children which would also be able to have children and so on.

Those people are scientists and engineers. They also feature genetic resistance against old-age illness, like pulmonary, brain or hearth diseases and cancers. Since there is no biologically pathogen available, this means that they would not naturally die before they lived beyond their 80s or 90s. However, even if nature is more forgiving than what happens in Earth, people still might die from falling off a cliff, drowning in the sea, being crushed in a cave or mine collapse, being poisoned by ingesting some dangerous mineral, being eletrocutted by incorrectly handling some machine and so on.

Many of those people have deep knowledge in physics, chemistry, math, biology, medicine, geology, engineering, economy, logistics, robotics, etc., each one to his/her own expertise. Those humans, collectivelly possesses the knowledge of everything relevant for them that humanity knows in 2015. I.E, there are a lot of people who know about how to create and study graphene and electronics, but they might not know or care about what would be the last musical hit here on Earth or what are the most recent memes being shared in facebook.

# The objective

Are you curious why the planets are names Old Paradise and New Paradise? Well, first because those planets are like paradises. Second, because the aliens warned them that in 60 years, a huge bollide will strike Old Paradise and kill whoever is left there, transforming it in an inhospitable wasteland with unbreatable air, lava lakes and boiling acidic seas. All the 100 millions humans are then settled in an area of Old Paradise called Eden (more on that below). Their only hope is to be able to evacuate everyone to New Paradise, which will be spared and sustain human life for some more millions or billions years.

Those people are very smart and they all know that they must work together the best to be able to leave Old Paradise ASAP. Also they all have a deep desire to survive and to be able to successfully evacuate this planet on time. This makes those people all very willing to cooperate and survive, and are very altruistic one to the other. They are also workaholic. This also means that they are really interested in not wasting time and energy with wars, crimes, greed, disputes over natural resources, endless debates about politics, making money only for the sake of making more money, dedicating their knowledge to frivolous and uneeded purposes or to anything that may distract or divert them from their evacuation objective. However they might still be interested in playing games, have parties and have fun in order to enjoy their lifes and not getting too tired or depressed. On the other hand, since they know that Old Paradise is going to be destroyed and should be evacuated ASAP, there is little to no need to concern about environment and natural resources preservation or about pollution.

# The Eden

The people are initially distributed in an area called Eden in Old Paradise, which features some grasslands, meadows, rivers, beaches, small mountains and small forests within a radius of something like 1500 km. This way, those people would be able to eventually contact everyone quickly enough while also being able to take food and water from the nature.

Initially, the aliens left everyone in the planet completely naked, barefoot and barehand, and there isn't anything artificial human-made or alien-made provided for them. All of what they can start to work out are plants, animals, stones, water, soil and rocks.

Also, in order to properly answer this question, you might also add watever animal, vegetal or mineral resources are present in Old Paradise, especially in the Eden area, as long as you don't add something that is not likely to be a creation of nature.

# The question

Now the question: Is it possible that they might succeed to evacuate Old Paradise and sucessfully settle New Paradise with a minimal human life loss?

The humans have full knowledge of our current digital-age technology but are left only with stone age technology available. Are they able to bring everyone to New Paradise via space travel in 60 years, or they are all doomed to die when Old Paradise becomes a hell overnight?

Further, how would their technology evolve in the mean time from being naked with barehands and barefoot to achieving hability to perform mass-scale space travel?

If in the given scenario, they are simply unlikely to be able to reach their objectives in time, what are the minimal set of changes needed that would make at least something plausible that they would be able to leave Old Paradise en masse?

• How long do we have to pre-plan before we are dropped? The timescale is absurdly small, so we are going to have to rely on everyone doing exactly the right thing, every time, for their entire life, without making a single mistake from the global sense, without lightspeed communication until we invent electricity again. Also, do we get to know a priori the exact ideal way to maximize productivity of the land? Learning to farm a new planet would take perhaps 600 years. – Cort Ammon Sep 11 '15 at 1:12
• @CortAmmon Assume that they know just what is in the question when they awaken on this planet. I.E. This would include the time to contact nearby people and to figure out a plan to get out the planet as soon as possible. – Victor Stafusa Sep 11 '15 at 1:58
• Can we change the demographics to include useful non-STEM talents? Obviously farmers and survival experts would be very useful – Cort Ammon Sep 11 '15 at 5:23
• @CortAmmon Put whatever talents you need to in the planet. – Victor Stafusa Sep 11 '15 at 6:23
• I highly doubt that our current, modern-day civilization would be capable of getting 100 million humans into space in sixty years- the energy of the fuel required alone gets is spoken of in terms of multiples of current global energy usage. what-if.xkcd.com/7 discusses some relevant calculations (albeit for ~7 billion passengers.) – Maxander Nov 19 '15 at 19:35

It's not likely that they'll survive.

Think of it like baseball. I could do all the math, all the physics, all of the calculations needed to know exactly where, when, and how hard to swing the bat in order to hit a home run. But that doesn't mean I can actually hit a 100MPH fastball.

Similarly, having the requisite knowledge to build rockets capable of escaping the planet doesn't mean that they will be able to.

The key here is that they're starting from literally nothing - no clothes, no tools, no infrastructure. Let's just run through what they need and we'll see why they're so screwed.

Metal: They need to get a mining operation set up in order to get the metal they need to build the rockets. This will mean finding, extracting, and processing ore before smelting it into something actually usable (more on that in a bit). They need to do this without having factories, mines, even a simple pickax or shovel. They'd essentially have to get ore by bashing rocks together until they get enough ore for pickaxes, which they could then use until they got enough ore for a half-decent drill. Even still, they'd have to get a group of blacksmiths (Note: using "blacksmiths" as a generic term for "people who make stuff out of metal", because it's easier than going into great gory detail about every type of metal that would be involved) going at it because of the lack of industry, so it'd be incredibly slow work.

Infrastructure: Let's suppose they get lucky and find massive deposits of ore that are easily accessible so that they can get a mining operation going quickly. Great! Now how do they quickly get it from the mine to the blacksmiths? Or the finished product from the blacksmiths to the rocket assembly facility (more on that later)? Where are they getting their food? Moving rockets long distance is not feasible without tech (the crawler that NASA uses to get rockets from the Vehicle Assembly Building to the launch pad moves at a pace of 1 MPH). In order for this to work, at the very least they would need a road system in place - whoops, that's more work they're gonna have to do.

Food requirements: Feeding a hundred million people takes a lot of calories, especially when they're doing manual labor like mining, smithing, building roads, building rockets, etc. Implausible as it may be, we'll suppose that large herds of animals (deer, bison, etc) haven't learned to leave Eden alone and they're easy pickings for anyone with a decently thrown rock. The rock throwers will be the main source of food until they can get enough hide (leather) to use for slings, or until they can craft bows and arrows. But a hundred million is still an awful lot of people to sustain from hunting and gathering. It would take some very clever math to figure out how much you can hunt without destroying the herds entirely (because we'd like to still be eating come year 50).

What do we do?: They have the knowledge of what is needed. That doesn't mean they have blueprints, CAD designs, etc. They'd need to plan out how the rockets will actually work, and they'll have to have a design chosen by the time the mines get operational so that the blacksmiths know what to actually make. And they'll have to be made very well, because we're dealing with space. Challenger exploded because it was too cold for one of the parts. When Hubble was first launched, the picture quality was awful because the mirrors were out of focus by a few microns. Precision is very important with space, and they won't have many chances to get it right.

Rocket assembly: Okay, let's get into the actual rocketry bit. Currently the only rocket that has taken humans to another planetary body is the Saturn V, so I'll use that for estimates. They'd have to be able to get massive hunks of metal firmly in place 300 feet in the air. This will either require a crane system (which will need to be metal and strong enough to lift rocket stages - the stage at the top which held the astronauts was about 23,000 pounds, and they got heavier as they get closer to the ground.

"How do I fly this thing?": Again, it's one thing to know how to do something, and it's another thing to actually do it. There's a reason that astronauts train on simulators for as long as they do - if they mess up even a little bit and can't fix it, they're dead. And these things would pretty much be under manual control, unless they were able to program the computer to- oh, wait, stone age, they'd have to develop computers in order to do that.

Population: I'm bringing this up now because it'll tie into the next part. How many people are going up? Based on the OP, the people are in their mid-20s and will live until their mid-80s for the most part. Unfortunately, that's exactly when the asteroid is hitting the planet. So while we COULD launch people on their deathbeds to another planet, it probably wouldn't be smart. We'd want them to have had children to make it easier to establish life on New Paradise. Besides, using a ballpark of menopause at 40, they'd need enough women under 40 to be able to sustain the population But that increases the number of people we're trying to send. Let's say that people pair off and have one child per pair around year 10 (they're in their mid-30s), giving a grand total of 150 million people, then 175 million when that generation turns 20 in year 30 (as the original generation is now above 40), and then about 200 million in year 50. That generation would turn 20 after reaching New Paradise. The actual number would be a bit higher, but for hand-waving purposes we'll say not everyone gets pregnant or some people died.

How many rockets?!?!: Saturn V carried three people. We have 200 million. Now, we can probably cram a bit more, since it's a life or death situation, and we can remake some of the hardware (like we don't need a lander that can also leave the surface again) to fit more people. Let's say we can cram ten people into a rocket (for reference, the International Space Station usually has six people on it). That still means we need to make 20 million rockets to get everyone off the planet. Which is a hell of a lot of metal, but that's not even the biggest problem.....

FUEL: Ah, energy requirements, the bane of all things fun. Saturn V used about six million pounds of fuel (5.6 million in the launch stages, and I can't find numbers for how much the lander used, so I'll cheat a bit). We have 20 million rockets. That's 120 trillion pounds of fuel. Good luck with that.

Consensus: Not Feasible

There are just too many issues to overcome with getting from the Stone Age to the Space Age for it to happen in sixty years, even with the knowledge already there. Honestly, their best bet would probably be to have a group of them working on the laws of physics to try and find a way to rig up a teleportation device to get them from one planet to the other. And when developing teleportation is your best bet, something is wrong.

Now, what could we do to improve their chances? Obviously starting them with good tools would be good. I'd also say give them an established infrastructure system (ie roads and bridges) that they don't have to worry about building and maintaining so that they can actually get started on mining and processing ore as quickly as possible. Unfortunately there's just no real way to get around the lack of industry. Assuming a 365-day year like on Earth, they have 21,900 days to build 20 million rockets. That's just over 913 rockets per day. Give them pre-existing factories, even if they're just skeletons of buildings that aren't currently doing anything, and maybe they'll have a chance. But at that point they aren't exactly in the Stone Age.

• Welcome to the site, John. You have a good answer here, but I felt the text was a little dense. I've made a few minor edits. If you disagree with them, feel free to roll them back. – Frostfyre Sep 11 '15 at 0:11
• If we would just change the initial population, their initial distribution on Old Paradise and/or the time until the impact, what would be their chances? – Victor Stafusa Sep 11 '15 at 2:00
• @VictorStafusa A smaller population would help immensely. Say a hundred thousand. Way fewer rockets needed, as well as food etc. That would also make the distribution better, though still not great. Need those massive herds until you can get agriculture. Time is the key though. There is a LOT of stuff that has to be in place for space flight to work. If it was the sole focus, so industry and infrastructure were designed to optimize space flight prep.... Maybe five hundred years? The biggest help would be starting in a time period with better developed industry. – John Robinson Sep 11 '15 at 2:38
• While I agree they are doomed you're thinking way too small on your rockets. Old Paradise is going to be destroyed anyway, it doesn't matter what happens as they leave. Thus they're going to take to the skies on Orion boosters, not chemical rockets. I rather suspect the landing will be in Orion into shallow seas, also. – Loren Pechtel Sep 11 '15 at 4:11
• I think time is the real factor, not numbers. The smaller populations end up putting more load on the community for space rockets. Space is not cheap. At our current rates, with several decades of infrastructure in place, it costs \$25M/seat to put someone in space (Soyuz). A minimum breeding population is 5000, which calls for the average production of \$20,833 /capita /year devoted just to spaceflight for all 100k individuals using current technologies. They wont have current technologies, and they will not be producing \\$21k surpluses in the first years. – Cort Ammon Sep 11 '15 at 5:21

I'm sorry, but your human population is doomed. Regardless of their intelligence, knowledge, dedication and fear of dying, they're trying to bootstrap an entire civilisation from the stone age to high-occupancy short-range spaceflight in practically no time at all.

In fact, if all 100,000,000 of them are deposited in the same area of Old Paradise, there would be mass starvation as they stripped the landscape for everything edible, and then found that the appetite of such a huge number of people is such that they could literally not run fast enough away from Eden in order to gather enough food before everyone starved to death.

Then, when a few thousand survivors managed to escape into the wilderness and relearn the skills of being hunter-gatherers, their high-tech skills and knowledge would be worthless in the face of the daily grind to merely survive, and it is likely that with knowledge of the impending disaster, depression would set in in many, leading to a further wave of deaths from suicide.

So, far from proving that humans are resourceful survivalists, the alien scientists would be embarrassed that they have engineered a situation impossible for humans to survive.

In order for this scenario to be survivable for the human population, we are going to need two or three alterations - a much lower initial population that includes those with knowledge of agriculture and wilderness survival and a more distant deadline, on the order of 400 to 500 years. A higher initial technological level would allow a significant reduction in time.

• The Eden area is something of a radius os 1500 km (which implies a diameter of 3000 km). Why is this not big enough? Looking for something like China, even in ancient times or middle ages, this seems to be plausible for me. Further, how their technology would evolve in the mean time even if they all decided to try their best until the last minute without anyone prefering to just commit suicide instead? – Victor Stafusa Sep 11 '15 at 2:06
• Do you have any idea how hard it is to survive in the wilderness - especially if you aren't trained for it? There won't be any pre-established agriculture there, just 100M people, most of whom are not survival trained, and they'll strip the place bare of immediately available food - you're talking about 14+ people per square kilometre, and this is unsustainable for a hunter gatherer society. A sustainable population for stone age man is 1 per square mile. – Monty Wild Sep 11 '15 at 4:03

This answer is a bit of a stretch, and isn't technically the answer asked for by the OP...

Instead of trying to build sufficient lifting capacity to move an entire population - or at least part of one - to a 'moon', on being told that there was a bolide set on a collision course with Old Paradise, and that they had 60 years before impact, I can imagine that these rocket scientists would be engaging in lateral thinking.

I'm also pretty sure that at least one of these scientists would come up with a solution that these aliens may not have anticipated - save both planets.

How do we do that?

Step 1: Feed the starving masses. It may take a year or two, but we have to get plenty of separation between our settlements so that the land won't be overtaxed. This could be quite difficult, but we have motivated people...

Step 2. Go for high-tech manufacturing capability. This is the tough bit, but for the purposes of this answer, you don't need a whole lot of it. This may take forty to fifty years.

Step 3. Build telescopes and plot the local asteroids and the like. Anything big enough to do a number on Old paradise has to be big enough to spot a fair way out. It may take thirty years to get a decent telescope or three, but that should be soon enough. This can take place concurrently with step 2.

Step 4. Use the high-tech manufacturing capability to build the biggest Ravening-Beam-Of-Death style FEL x-ray laser they can and place it on the highest point of the highest mountain. It would be better launched into space, but the mountaintop location may be the best that there is time for.

Step 5. When the bolide comes into sight, focus the x-ray laser on it - specifically one side of it - flip the switch, and keep blasting until the ejecta plume of vaporised rock/iron/whatever from the point of impact forms an impromptu rocket engine that pushes the bolide sufficiently off-course that no impact will occur. The longer the time before impact, the easier this will be. Catch the bolide a year short of impact, and you could generate a miss easily. A month? No problem. A week or less might be cutting things a bit too close.

So, this doesn't involve transporting the population to the other planet ahead of the impact, but it does allow them to get there in a far more leisurely manner, having averted the impact altogether. If the aliens wanted to make sure everyone tried to get off the planet on schedule, they shouldn't have been so specific as to what the disaster was going to be.

This has the advantage that a relatively small manufacturing base is needed, as opposed to that required to build sufficient lifting capacity to extract the entire population - or enough of it to form a self-sustaining colony - to New Paradise.

• :) - I was silently expecting that someone would suggest something to deviate the bollide. However I was thinking about going there and nuke it with enough atomic bombs to either destroy it (too energy expensive, and the self-gravity could make it reassemble) or enough to take it off the course (way simpler). But this might very well also work and is yet simpler. However, if you can, I would like to see some deeper calculations about the energy cost vs bollide size and mass. – Victor Stafusa Sep 14 '15 at 0:51
• Sorry, I'm not quite that much of a mathematician/physicist to pull this off the top of my head, nor do I have the time to work it out from scratch. Might I suggest that if you're really interested in this, make another question based on this, and I'm sure that one of the mathematicians or physicists that lurk hereabouts could answer it. – Monty Wild Sep 14 '15 at 1:14

This is one hell of an emergency flight. Let's see if they can make it.

For problems as these, it is best to use a reverse approach. Here's how it's done. We are not going to begin with metallurgy, but rather with spaceships and go back to prerequisites for every step and see if we can make it within 60 years!

1- Building A Spaceship

3 years I say. AT LEAST. Since all the population is working coherently 24/7, they can build a large enough spaceship within 3 years. Notice that the parts would have to be built on separate places, you don't have to pull all the population on one point for that.

We have 57 years left to reach spaceship building technology.

2- High End Technology Labs And Production Units

We have all the required material here (metal, plastics, fibers etc) and we want to build hightech production units for constructing a giant spaceship. Since they have all the knowledge and guidelines, the only headache is practical, not theoretical. There is no issue of "how to do that?" The only issue is "lets do it buddy, and do it real fast!" 7 years I say, no less.

We are left with 50 years to reach this stage where we are capable of building spaceship production units.

3- The Industrial And Technological Revolution

We have refined metal and plastics here and we want to make the industrial revolution happen. That is, we want large scale electricity production, we need to invent the integrated circuit, the internal combustion engine, build very large production units and start carrying out complex calculations on some really fast computers.

How much time for all this? 25 years I say. First 10 for building the electrical framework that is a prerequisite and the next 15 for building and improving the integrated circuit technology. This is the time interval required while we know WHAT exactly we want and HOW to do it.

We have 30 years left for reaching this stage where we have large metal refining and abundant plastics production units.

4- Metallurgy

This is not as easy you think it is! Metallurgy involves digging up a metal ore, having huge structures to roast, smelt and filter it and add additives to it for tensile strength (i.e. converting iron into steel).

10 years here. We won't be producing enough steel and aluminum to develop skyscrappers with our small metal refinement units, but we will have enough metal for building a large spaceship, nevertheless.

Once we get to refine our first 1000 tons of metal, we can develop steam engines, which will revolutionize our progress speed.

We have 20 years left to reach metallurgy stage now.

5- Mapping The Planet

We are a group of people limited to one region of the planet, and we need to map all the regions of this planet and it's resources. Fast, fast, FAST!

Send in parties to all directions for a distance of 2000 km from our starting point. We won't have more time than that. Yes, more than half of the planet will be left from exploration, but we can't waste more time on exploring the planet!

Since there are no dangerous animals, insects etc, our parties make their round trips within 6 months (on foot of course). This means they will have to walk 22 km per day. Not too much to ask for, if you ask me.

Now we have a limited map of our planet, marking the surface resources in our vicinity.

1 year would be required for mapping 2000 km radius circle AND recording the findings on leather parchments, wooden sheets etc.

19 years left to reach this stage where we are ready to begin metallurgy ventures.

6- Basic Tools Production

We need a lot of basic, prerequisite tools before we can think of the next stage. Shovels, crowbars, lots and lots of paper (leather and wooden sheets would serve for it) and things like these. These are going to be required in large amounts!

Try different wood types. Find the suitable ones. Make stone tools for woodworking. Start a large scale production of these primary tools. 3 years for this stage.

16 years left till we are able to take this first step!

5- Develop A Colony And Establish A Social Structure

We are a band of unruly people. But we do have a know-how of advanced social structures. Since there are no disputes between us and there are no "politicians" among us, we can successfully design a social system quickly. Since we know what we want to do, let us organize our population in categories of engineers, surveyors, builders etc.

2 years to design a social structure for our population and listing down the expertise of every individual.

14 years left from the start now.

6- Where The Heck Are We And ... What Is This Place???

We are freshly transported on this planet and we want to know what it is and what dangers we might face. It's everybody to himself at this stage. There are expected to be feuds, murders, anger, depression, rapes, deceit and whatnot at this stage. Once we get to understand that this planet is only our temporary abode and we must act together, crimes will stop and people will come closer (socially). A social structure can now be built.

I think 7 years will be passed in these "dark ages" era of this planet's human history.

After all the math, we are left with 7 surplus years on our table. This means that even if one stage in our evolution requires a couple more years than we anticipated, we will not hit the extinction deadline with that.

We should be able to make a last minute flight out of this planet.

THE MAIN PROBLEM

The pioneers of this planet are all adults within reproducing age-range. They also have full technological know-how of modern day science. Problem is that with time, people age. Of course babies will be born who will replenish the lost population count, but babies aren't born with all tech-know-how. Babies have to be taught these things. Here on this planet, there are no books. There are no science labs or libraries or schools. And even if they learn some basic things with apprenticeship, these 2nd generation people will not be as much focussed on the mission of escaping the impending doom as the first generation. These, seeing there is no immediate threat to their survival and that the environment is teeming with lush green pastures, plenty of game and food sources, are very very likely to deviate from their purpose and consider their elders as fools.

And ... by 30 (maximum 40) years, most of the 1st generation people would be dead and the project would be left for completion with the 2nd generation. These will be quarrelsome, egotistic teenagers who would want to just sneak into the lush forests with their bf/gf and do their thing, instead of focussing on the goal of their elders.

So yes, the humans on this planet are doomed. But not because they don't have enough time, but because of death and age, the task would be left with 2nd generation who don't have technical knowledge, nor are interested in designing of the spaceship.

More like people of Noah's time if you ask me. "Come on old man! Don't jinx us. A shooting star is going to fall on planet and destroy it after 30 years? Oh boy, you're getting senile, I can tell! Emily, look what Mr. Naddley is on about!"

• Some parts of what you say here can be done in parallel, which might shorten the needed time. Also, even if some of the younger boys rebels out, there would still be a large part of youngsters that who would not and surely there would be many people with more than enough desire to teach the 2nd and 3rd generation the best of what they can. Further, they don't need to build only one big spaceship, but if they do, how large would be that spaceship? – Victor Stafusa Sep 11 '15 at 6:30
• The size of spaceship depends on several factors. -a- The size of the colony that is to be transported -b- The production resources they muster -c- The engineers available for working on this project (notice that all people on the planet aren't space engineers) -d- The available fuel -e- The distance between the planets (the shorter the distance, the bigger spaceship you can afford as it will need lesser fuel). Also, while I think that in case the pioneers don't age, they can finish the project in 60 years, I really don't think the 2nd generation can (or will) do it. – Youstay Igo Sep 11 '15 at 6:45
• Well, I defined the distance of the planets as twice the distance between Earth and Moon. And I defined the initial size of the colony as 100 millions people, although Monty Wild and John Robinson stated in their answers that this is probably too many people. – Victor Stafusa Sep 11 '15 at 7:36
• Too many people = both good and bad. You get more hands on the job which means a very fast progress. Even with 1 million, you are in for a world of speedy evolution. With 100 million you can practically get to spaceship building era within 40 years which is really fast (less than an eye blink). A larger initial population would also mean that the 2nd generation deviance from purpose will be much lesser than I expected. Still they would be lacking in too many critical aspects of information to be handy in spaceship building process. – Youstay Igo Sep 11 '15 at 8:02

You are very optimistic about our ability to survey and discover minerals, dig mines for raw minerals, develop industries to turn minerals into raw stock, find reserves of petroleum for energy, develop precision machine tools and heavy equipment, etc. It took 4 years to build the Golden Gate bridge. It took 6 years to build the First Transcontinental Railroad. It took over 20 years for Boston to complete "The Big Dig". It tooks 35 years to construct the US Interstate Highway System. These were all built with existing technology, tools, equipment, material supply chains, trained work-force, the best established industrial support infrastructure on the planet, by the richest nation on the planet.

I have a theory that the time it takes for us to develop and deploy technology is about equal to our ability to invent it. So starting from illiterate stone age people it takes about 8000 years to get two people to the moon. Starting from a planet full of highly trained engineers also wielding only stones, it would take them about 8000 years to get two people to the moon. Maybe a little bit less if nobody went on vacation and there were committees to decide who gets to get to dig the mines to extract the natural resources necessary... and there were no disagreements about work assignments.

This may sound like a stupid theory, and it's impossible to test, but I think it's a better starting point. You should start from the worst case scenario and then work toward optimizing your goal. Start with a presumption that it would take cavemen 8000 years.