I am currently working on a character backstory for somebody whose fictional character gets sent back in time an era before his species existed (essentially to bronze-age times or even earlier, it's not specified) and sets himself the task of building a spaceship by the time his original self is born again.

The character has been augmented in every way possible - strength, agility, intelligence - and has also been mentally force-fed every piece of knowledge known to his species. Essentially he's a true polymath by the time he has this spaceship-building task to do. He's also completely alone with no technology, not even wreckage.

I strongly suspect it's ludicrous to expect a lone character in the wilderness to build a spaceship, however much he might try to do so from the ground up, but I don't know exactly how it's ludicrous. I've tried pointing this out to my client but am having difficulty convincing him as he believes that his character could do it because he's just that much of a genius. Please can somebody help me out with specific snag points that this character would have?

Just to add to the fun, this character is also mindful that he mustn't do anything that influences the timeline.

I have tried reading up about this but haven't found any sources that give enough information about how a spaceship, or its supporting infrastructure, is made.

Any ideas/thoughts?

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    $\begingroup$ "building a spaceship by the time his original self is born again" set a time line. If the super mega enchanced hero is born, for example 2050, then the hero don't need to do anything. Spaceships 30 years before his birth are so "common" you have private companies launching trips to Mars. $\endgroup$ – SZCZERZO KŁY Apr 7 at 15:18
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    $\begingroup$ If you want a serious answer, you will have to define "spaceship" reasonably closely. It would be extraordinarily difficult for one person to build a Saturn V and its launching equipment, but the simple antigravity system in James Blish's YA novel Welcome to Mars would be far easier. $\endgroup$ – John Dallman Apr 7 at 15:21
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    $\begingroup$ A: is he immortal? B: What time travel paradigm are you using? If he has to try not change the timeline then he’s predestined to either fail or disguise himself as someone that built and launched a spaceship, given that there’s no historical record of any industry that would support space travel until post WW2. If the timeline is mutable then who’s to say he’ll even be born? $\endgroup$ – Joe Bloggs Apr 7 at 15:44
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    $\begingroup$ Thanks for accepting my answer, but it is customary to wait a bit longer and then accept the best answer. So you should take that back for now; I'll be happy if you accept again one or two days from now. $\endgroup$ – o.m. Apr 7 at 15:59
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    $\begingroup$ Here's a related question about why it would take even a group of polymaths most of a century, if not more, to go from nothing to modern technology: worldbuilding.stackexchange.com/questions/6747/…. Your lone individual will likely require millennia to produce the technology needed to go to space. $\endgroup$ – Nuclear Wang Apr 7 at 16:10

11 Answers 11


The obvious problem is building the tools to build the tools to build the tools. Say your character needs high-end alloys, ceramics, and plastics.

  • He needs various ores, starting with iron and titanium but also others to alloy them -- nickel, manganese, molybdenum, and many more. That will require mines in many different parts of the world. But before that, prospecting.
  • Those ores must then be refined and processed. That requires a high-end smelter. Charcoal probably isn't enough. Coal mining and coke produktion.
  • For ceramics, yet more materials are required.
  • The plastics might involve drilling for oil. That requires drill rigs, first.

... and I haven't started with the tools themselves, yet.

  • Does the spacecraft involve any microprocessors? Those cannot be assembled by hand, they are etched on a silicon wafer by photo-chemical processes. This requires clean-room technology. He can't simply build the factory, mothball it, and go to the next project. The seals would degrade.
  • How are the various factories powered, and how are materials moved between them? Gasoline has a very limited shelf life, he can't simply make a big tank of it early in the project and draw on that.

So even if the character is qualified to do any one step in the chain, he probably won't have the time to do all steps unless he is for all practical purposes immortal, and even then the synchonization is all but impossible.

Science fiction sometimes talks about von Neumann machines, factories which can replicate themselves. We are not nearly there yet, and doing it without a machine will be even harder.

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  • $\begingroup$ This... is exactly the kind of answer I was looking for! Thank you - I'm sure there are more examples of how this would be logistically impossible but your comments about synchronisation and about the sheer quantity of materials that must be displaced and moved without changing history show that this is an impossible task. Oh, and yes - he's immortal. Thank you! $\endgroup$ – TCC Apr 7 at 15:59
  • $\begingroup$ Prospecting seems unnecessary -- "all the knowledge" surely includes exactly where to find the ores he'll need with minimum effort and cost... $\endgroup$ – Zeiss Ikon Apr 7 at 16:01
  • $\begingroup$ @ZeissIkon, good point, but that might also depend on timeframes and continental drift. The good stuff today could be quite deep back then. $\endgroup$ – o.m. Apr 7 at 16:21
  • $\begingroup$ Nobody mentioned geologic time. Given enough time, such a one ought to be able to build anything... $\endgroup$ – Zeiss Ikon Apr 7 at 16:39
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    $\begingroup$ @ZeissIkon: Not necessarily. If components degrade (which we know they do) then there’s every chance you won’t be able to make parts fast enough to offset the losses. You need a massively parallel toolchain, but that just kicks the can down the road to ‘how can I maintain my toolchain without help’ which is just as big a problem $\endgroup$ – Joe Bloggs Apr 7 at 18:54

Math will get you a long way into calculating stuff. But you can't calculate steel and electronics into existence. You need to turn the raw material into stuff.

Just think of Virgin, Space-X, NASA or ESA. Those companies/agencies have international supply chains. Each supply chain has factories and many offices for logistics.

Even if your protagonist knows how to build a spaceship, he doesn't have the manpower nor the infrastructure to do so. He would spend many human lifetimes to produce even the smallest components, and by the time he finishes a part another might have been lost to time.

If this still isn't enough - do an iterative process. You can do it backwards. Before building a vehicle that can achieve orbital flight, the protagonist should be able to build a modern supersonic aircraft. And before that, a regular jet plane. Before that, a plane. Before that, a car. Before that, an engine.

You may handwave a genius person building an engine, maybe even a car with access to modern tools and a mechanic shop. But building a jet engine in the woods? This is unusual even in the DC comics/Marvel kind of literature.

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Maybe but probably not.

This gives a timeline of 5 billion hours to do the Apollo Program. It's probably gonna take longer if you're starting at nothing.

A million years is about 8 billion hours. So, if he was dropped a million years in the past, technically he'd have the time, but a million years is a long time. Steel would rust, plastic would break down, and accidents would happen.

There might be a way to do it. If they're a sci fi super genius they may be able to invent cold fusion, ala Tony Stark building iron man armor in a cave with a box of scraps. If they can work out how to build a small nuclear reactor, they could make a very crude spaceship.

That said, this or any jury rigged plan carries an extremely high risk.

3.2% of astronauts died, and he has to build it over a much longer time frame with more chance for random wear and tear to make components fail. If a test fails, then it's gonna change the timeline massively when a possibly nuclear space ship explodes in the sky and massively mutates the populace.

If he does have sci fi genius creation skills and can create small portable cold fusion devices like arc reactors, then it's doable. You just need some fuel source to accelerate, gears and mechanical systems to handle the ship, a shell, and he can slowly fly up and down. Nuclear power makes space travel a lot easier, if risky.

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  • $\begingroup$ I can't imagine attempting to build a nuclear reactor from first principles.. it's about the most dangerous project I can think of. $\endgroup$ – Ruadhan Apr 8 at 11:43
  • $\begingroup$ Nuclear reactors aren't the most complex thing. boredpanda.com/story-radioactive-boy-scout-david-hahn/… Reportedly, a kid built one in his back yard. Plus I imagine the superhuman is pretty radiation resistant. Not that it's a good idea, but it vastly reduces the size of the necessary project. $\endgroup$ – Nepene Nep Apr 9 at 17:21

first off welcome to worldbuilding SE. Building a spaceship isn't very easy, look at a picture of the saturn V saturn v that's very big uses alot of fuel and none of the technology is available. ok lets say there's a different currently nonexistent rocket that ill call the X rocket. the X rocket is a very simple rocket that has 3 tanks a shell, batteries and the engines. lets also say you can make this with blacksmithing. you would STILL have the problem of getting the supplies to make a X rocket. then finally you have everything by some stroke of luck. Nope you still cant get any fuel.

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  • $\begingroup$ Well yes. I want to emphasise again that understand that the question is ludicrous. I just want further information on exactly how it's ludicrous. I suspect tha blacksmithing wouldn't cut it since you need a perfectly smooth shell to avoid burning up in space. So surely the question would be, how to create the technology required to create those. In theory if I work back far enough then this character could make the technology, but he's still working alone so I wonder whether that would lead him to an impossible task somewhere along the line. $\endgroup$ – TCC Apr 7 at 15:46
  • $\begingroup$ well this X rocket wouldnt even work you would still need a het sheild, unless hes sent back to like 1950 he has no chance $\endgroup$ – Topcode Apr 7 at 15:50
  • $\begingroup$ Mm, but my question is exactly why is making a heat shield impossible? This client is pretty certain that his genius character could do it, has absolutely no idea how but that's not deterring him from writing this, and I'm looking for either wiggle room through for this character to be able to do it, or cast-iron proof that it would be genuinely impossible. $\endgroup$ – TCC Apr 7 at 15:53
  • $\begingroup$ that heat sheild will make it much harder and one mistake on it and... you die $\endgroup$ – Topcode Apr 7 at 16:01
  • $\begingroup$ Yes, but how, and why is it so hard to make a perfect one? $\endgroup$ – TCC Apr 7 at 16:03

Character gets sent back in time a couple million years or so --- that would be "before his species came into existence"...


...then he got eaten by a realitycheckasaurus!

Sorry! Tell your friend that even geniuses get eaten by monsters.

Reality Check:
This scenario will certainly fail because the character has no tools, no tech of any kind with him, no companions, no help, and will literally be spending his every waking moment just trying to stay alive.

He's going to need to find a good source of water, some kind of shelter, some kind of weapons for hunting and defense against creatures that want to eat him and have no fear whatsoever of his species. He's going to have to clothe himself for the environment and he's going to have to worry over everything he eats, everything he drinks and every little cut and abrasion he gets.

Let's just face it: if he survives the first day, he's unlikely to survive many more. His best plan might be to spend his days carving some Nazca Lines into the earth in hopes that someone up in low planetary orbit will see them and come down to rescue him.

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  • $\begingroup$ I think you're overestimating "survival in the wilderness" difficulty. The MC is described as a polymath superperson who has all knowledge and strength. Roughing it wouldn't be too hard. Today, if a human prepared, they would be able to survive indefinitely in most places on Earth (baring oceans and deserts). The biggest problem would be lack of other people, and they would go insane as humans are a social animal. $\endgroup$ – Dragongeek Apr 8 at 13:57
  • $\begingroup$ As for free time, most experts today think that individuals in primitive hunter-gatherer societies had more free time than a modern office worker does. $\endgroup$ – Dragongeek Apr 8 at 13:57

I think the answer should be a simple "no way".

But then again, this is worldbuilding SE.

Let's see what we can come up with to make it possible.

Others have pointed out the extreme complexity of the task, and of all the tasks that must be completed before. The whole bunch is a showstopper. So let's find a ways to eliminate the showstopper.

Your caracter - after establishing himself in the wild, which includes living long enough, should have knowledge of how to build a nanoassembler, i.e. a machine that builds complex things from simple ingredients.
The general idea is that instead of building the tools for building the tools, you use additive manufacturing to cut most of those routes short.

This nanoassembler, or at least the first in a chain of such machines, should be specifically designed to be built from scratch. You will need quite some handwaving heere, but let's say that with the right combination of not-too-complex chemistry and some magnetism you could create the first simple nano machines that in turn can break up earth, wood and stones for their component molecules, and with those create the next, bigger, faster assembler.

Obviously you need a power source for the assemblers (and for surviving), so you should also have a reasonably simple way of creating either solar cells or a solar oven.

But, if you can think up the existence of nano assemblers, you might also think up a small, portable survival tool style nano assembler, together with it's own solar power bank, which your character happened to bring along, just like many people today carry smartphones and powerbanks wherever they go. That might help with credibility.

Of course, once the first nano assembler is set up, all you need is time. Especially since your character has no shortage of knowledge. From there on, i think one might actually end up with a spacecraft.

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Start in Australia

Two main aspects of this problem are you're going to need other people to help and you can't alter history. You're also going to need a lot of space to build factories, mines, etc., and you can't let any of that be seen. My suggestion is -- conduct this work in some place like Australia that was only recently (geologically speaking) inhabited.

If you get there early enough, you can build your entire technology and supply chain, launch your spaceship, and then destroy all the evidence, before the first humans (that we know about) arrive around 65,000 BC.

If you can't take anyone back in time with you, I suggest rescuing people from shipwrecks who would have otherwise been lost to history. So you'd spend your first couple of millennia alone, developing basic technology, observing primitive people, building a submarine, and waiting patiently for an opportunity to rescue/capture/recruit your first few workers. Once you've got a growing population, teach them agriculture, mining, and manufacturing, and inculcate them with your mission.

From that point on, it will probably take less than a millennium to launch the first ship. You can't stop there, though. Unless you're a moral monster, you'll have to move your entire population off-planet, or into the future (and remember the population is growing all the time you're working on this). So, figure another ten thousand years to develop a time machine or a self-sustaining colony on the dark side of Pluto and move all your people there. Then it's simply a matter of destroying all your mines, factories, launch pads, apartment complexes, universities, etc., without creating such a dust cloud that it'll alter the climate enough to change history.

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Realistically speaking? no, the idea is bullshit and sounds like someone just got too attached to their favourite genius character and doesn't want to admit that they aren't perfect either.

As for making it seem believable, I'd say fusion reactors and nanobots. Both are technologies that people accept as possible but not yet doable, and one can be used to explain the energy consumption and the other the production of advanced devices.

So the question would be: how does your character get there? Assuming he has knowledge of physics beyond our current understanding all in his head, accessible at any time (which, in itself is somewhat beyond the realms of suspension of disbelief for me), he might somehow be able to pull it off without it seeming completely unrealistic.

I believe an essential point would be the development of computers. A basic computer can be built with surprisingly simple components, but to get to the processing power one would need, you really do need high-tech production facilities; but maybe one could handwave that away since there needs to be no mass-production, so a small facility with a few robot arms could be used in a cycle of better hardware creating even better hardware, until the point where some sci-fi tech can take over and it becomes easier to accept that the tech-magic just works a certain way. From that point on, a spaceship isn't all that unrealistic.

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Yes, I think it could be realistic that this "peak person" could build a "spaceship" without any starting resources, but it would only be a "spaceship" by definition.

For something to be a "spaceship" it needs to:

  • Keep occupants alive
  • Be able to move/achieve delta-v in a microgravity environment

This means that your hero needs to build something that:

  • Is airtight and can withstand at least 0.3 standard atmospheres of internal pressure
  • Has enough breathable air for a single occupant not to suffer from carbon dioxide poisoning immediately
  • Can somehow thermally regulate itself
  • Can somehow propel itself in a direction.

All of these, while difficult, are achievable with primitive construction materials like wood, natural fiber, and tiny amounts of metal provided the spacecraft and occupant are simply "teleported" into empty space and don't need to survive a launch.

To construct this primitive spacecraft, the hero should build an extremely large barrel. Making airtight and pressure tight containers is an old technology, and building a barrel big enough for a person is within the technological capability of a lone survivor. Furthermore, if they make this barrel big enough, they would be able to last quite a while before carbon dioxide buildup kills them and they could start a fire inside the barrel to provide warmth if they get to cold (this would rapidly decrease available air though).

For propulsion, they could poke a hole in one side of the barrel or unplug a cork and use the escaping air to provide a tiny bit of delta-v

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** He Can't Do It Alone, But Maybe He Doesn't Have To**

As others have discussed, even on geological timescales, creating advanced technology from nothing but knowledge and wilderness is staggeringly implausible.

Good news! Your enhanced man has all of his race's knowledge packed inside his head. This ahould include the locations of many ancient tribes and savage settlements. It's a risk, but if any group appears to have gone extinct in isolation, he can show up beforehand, pass himself off as a god, build a cult, fake their extinction, and then he has a group of workers at his command. Generation upon generation of workers.

Manpower problem solved. The story he tells them may be something like how the future will need a special, select people (and the artifices they create), but they must be unknown until the chosen day, blah, blah, blah...

The trick is maintaining control, and getting the required materials and the work done while not leaving a footprint for explorers or archaeologists to find. But the manpower issue is solvable.

Bonus: When the time comes, you'll have a crew for your ship.

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I think it's an interesting and cool idea!

There is a video game called Factorio where your objective is exactly this (check it out if you haven't already). In the game you start with a simple tool for harvesting stone, ore and wood and have to eventually launch a spaceship (for the purposes of this comparison ignore the critters against which you must defend yourself).

Automation is key, essentially you don't build the spaceship, you:

  1. Build tools to harvest resources
  2. Use resources to build robots to harvest more resources automatically
  3. Use the extra resources (and robots) to build factories that build more robots and factories automatically
  4. Iterate until you have a factory run by robots that builds spaceships

Look into how primitive technologies worked, like a primitive kiln to make ceramics. Then you can make a smelter to get metals, starting with lead and tin, then working your way up to copper, bronze and eventually iron and steel.

All you really need is wood, stone and clay to get started.

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    $\begingroup$ Keep in mind that in factorio you evidently have some fancy super-science technology for constructing autonomous hardware with just raw materials and no infrastructure. in reality the first drill you make is already a hundred steps ahead of the previous technology of clay furnaces. Not exactly working from first principles $\endgroup$ – Ruadhan Apr 8 at 11:28
  • $\begingroup$ Robots? You need an electronics industry first. $\endgroup$ – Spencer Apr 8 at 13:18
  • $\begingroup$ @Ruadhan you are correct. I referenced Factorio here more for comparing objectives with the OP question rather than circumstances. Though they are similar there is a much bigger jump. Keep in mind though that the OP stated that this character has the entire knowledge base of their society (who can time travel!) so I am assuming they already know exactly how to do everything that they need to do to get to the end game. $\endgroup$ – Rorxor Apr 14 at 1:43
  • $\begingroup$ @Spencer robots don't have to be electronic.. any machine that can execute a task automatically like a primitive Monjolo or even a windmill is a robot if it can just keep doing it's thing without intervention $\endgroup$ – Rorxor Apr 14 at 1:45

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