This is set on a fictional alien world with medieval people. However, this world has alien livestock that are capable of flying into outer space and traveling to other worlds. These medieval-age people figured out how to use the animals to tow their ships from planet to planet, all with no technology. Would they be able to create a ship or ark that can withstand the elements of outer space using common materials? They would have protection against radiation and have their own source of water and heat and air and water using fictional means. However they would need to build their ships using common resources such as oil, tar, wood, etc. Is it possible to build a ship or ark out of wood and other common materials that won't implode in space? They would also have their own type of epoxy sealant that will make their ships absolutely airtight, which would also protect them and their ships from radiation, etc.

  • $\begingroup$ Short answer: No / Slightly more nuanced answer: Given a short enough travel time between planets they could perhaps do an adequate job to hold in sufficient atmosphere for long enough for them to travel from planet A to planet B, the radiation isn't a problem they'll even be aware of so they won't do anything about it though (assuming these flying beasts have adequate lifting & propulsive power) it would be easy for even their tech to solve as all it needs is adequate shielding so it's just an issue of mass & weight. $\endgroup$
    – Pelinore
    Sep 17, 2021 at 17:29
  • $\begingroup$ If the question assumes an endless ability to generate energy and matter out of nothing (food, water, air, heat) anything is possible. This does, however, badly violate physics and causality. Build a bubble out of your perfect epoxy and skip the hull entirely. Your issue would be the gasses exploding, not imploding. How long are the voyages the ships need to make? What sort of sheer and G-forces do they need to endure? $\endgroup$
    – DWKraus
    Sep 17, 2021 at 17:30
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    $\begingroup$ Turtledove has a story (The Road Less Traveled) where most civilizations quickly discover the principles of anti-gravity and achieve spaceflight at a very low level of technology. The only other requisite seems to be building airtight metal modules. One civilization hadn't even entered the iron age, they built theirs from bronze. The tradeoff is that once you discover this, the scientific principle seems like bullshit, and so you stagnate and never develop anything else. Earth is invaded by an army of aliens wielding flintlock rifles, much to their sorrow. $\endgroup$
    – John O
    Sep 17, 2021 at 18:15
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    $\begingroup$ What about using the hides of the beasts that migrate? $\endgroup$
    – Allan
    Sep 17, 2021 at 21:23
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    $\begingroup$ worth noting a pressurized ship will not implode, it will explode in a vacuum. Also what you you mean by having a source of air, does it maintain normal pressure, does it remove Co2 and add oxygen, if you can magically make air fast it does not need ot be airtight. $\endgroup$
    – John
    Sep 18, 2021 at 12:44

2 Answers 2


If airtightness is the only requirement, then yes, medieval people could create such vessels

By middle ages, creating watertight ship hulls was a very common task. Yes, ships leaked, but that could be successfully mitigated.

Also, diving bells were known since antiquity, and fully isolated "dry" bell is not very different from a spaceship. 1 atm pressure difference could be easily handled by wood and metal construction.

Dealing with the coldness of space is more tricky, because iron will become brittle, and any wet insulation will become dry, but if medieval NASA can get enough tries, they can find out what works and what not.

Radiation hazard can be mitigated by building thicker hulls. This is something that the builders absolutely can do, but they must know it from somewhere, or learn the hard way.

Excessive G forces, atmospheric shocks, high temperatures and life support would probably be too much to handle for medieval technology, but that seems to be outside of scope of this question.

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    $\begingroup$ Vacuum is not cold. On the contrary, vacuum is an excellent thermal insulator. I would be very much more afraid of being cooked in a medieval spacecraft than of being frozen. (And in real history, Otto von Guericke's famous "Magdeburg hemispheres" experiment demonstratring atmospheric pressure happened in 1657. Yes, it's 200 years after the end of the Middle Ages but it is still proof that airtight vessels able to withstand 1 atmosphere of pressure could be made by Renaissance-level technology.) $\endgroup$
    – AlexP
    Sep 17, 2021 at 19:06
  • $\begingroup$ @AlexP vacuum is not cold, so as it not an insulator - the sun is the proof. It looks like insulator because at low temperatures black body radiation flow isn't that high. If I remember rigth it about 450W/m2 for 300K. And sure with star next to them cooking may be a real problem. $\endgroup$
    – MolbOrg
    Sep 17, 2021 at 19:51
  • $\begingroup$ @MolbOrg: An excellent thermal insulator is not a perfect thermal insulator; and of course we are speaking about temperatures where humans don't get vaporized. (On the other hand, solar irradiance around Earth is about 1360 W/m², but of course those are cross-sectional square meters.) $\endgroup$
    – AlexP
    Sep 17, 2021 at 20:12
  • $\begingroup$ @AlexP good point about the thermal balance, although for the internal comfort I assumed this is an out of scope problem. For the conditions on the outer surface of the spaceship (which should be in scope) the heat on the sunny side should not be as bad as to cause any issues to wood or metal, however, the cold in the shade can be an issue. $\endgroup$
    – Alexander
    Sep 17, 2021 at 20:45
  • $\begingroup$ Ships are not very water tight, and wood will get much less watertight when subjected to vacuum. more importantly to survive weeks or months you need a gigantic ship to have enough air. a person needs a bout a shipping crate of air for each day. $\endgroup$
    – John
    Sep 17, 2021 at 20:55


they can't make a airtight container big enough for weeks of travel, especially not one that can withstand vacuum. Even a day of travel is probably impossible. You need a shipping container worth of air per person per day. Since it needs to have doors it gets even less likely they can make it airtight.

The only technology they had for making airtight containers either relied on glass, or barrels, which have a scaling limit. if the travel times was an hour or few they could maybe manage with large single use barrels, assuming they someone at the other end to let them out. But even then it is iffy, wooden barrels can't withstand much internal pressure. Even the materials themselves have problems. Wood, tar, pitch, glue, all these materials outgas in a vacuum, meaning they won't work for a seal in vacuum, natural material don't make great vacuum seals. if this is actually space, then uneven heating by the sun will cause even more deformation which is destructive ot seals.

Material problems

large barrels and ships are made in very similar ways at least in terms of making them watertight, tight fitting planks with either with nothing (rare) or a caulking (common) sealing joints. Usually cordage soaked in pitch or tar. All of which seriously outgas under vacuum, so they will break down or fail almost instantly when subjected to vacuum. Sealing things against vacuum is hard without modern materials because all traditional glues and sealers contain volatiles the boil off at vacuum pressures which destroys the material. If you want to get an idea of what happens put a marshmallow in a microwave. Even the water in the wood will boil off deteriorating any seals in contact with it and can even damage the wood itself.

Mechanical problems

Barrels work much better for our purposes because they are reinforced on the outside relying on compression to seal them so they can withstand some pressurization, but they still suffer the outgassing problem and the internal pressure they can withstand is still low, the end caps can't be braced like the sides so this is where leaks tend to start. Ships are pegged/bolted into place so will be far weaker to internal pressure, which makes sense they are designed to withstand great external pressure.

  • $\begingroup$ I made a comment under Alexander's answer, and in some sense it applies to this answer as well. Atm there is yes and no answer but both have no numbers, just some statements and yeah some ideas reasoning but there is no information which uses science to show or support any of those statemens. This time, I wanna be a baby girl(google traffic user) traveling in a train and looking in the windows to see the world, keeping calculator in its scabbard. $\endgroup$
    – MolbOrg
    Sep 17, 2021 at 21:37
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    $\begingroup$ @MolbOrg there are no numbers to apply, this is about construction methods not tolerances. medieval societies only had a few ways to make airtight containers, only one of the scales and it can't hold much pressure. volume and Co2 concentration which would be the limiting factor with a large airtight container does not even get a chance to come into play, $\endgroup$
    – John
    Sep 17, 2021 at 22:11
  • $\begingroup$ Do you know how hulls of wooden ships were made? Meaning technology? It almost composite technology. Not sure since when, but was watching repair of 100 something year old yacht. So as old ships 200+ had suprisingly nice displacement. Barrels are not the only technology which was available to solve the problem. But sure it up to you will you investigate or improve the q. Quality of both answers atm is not very high, and that with relatively simple OP's q which is tangible engeneering and history. Is wb become way too relaxed on grazing those magic q's to the point not being able to walk? $\endgroup$
    – MolbOrg
    Sep 17, 2021 at 23:16
  • $\begingroup$ @MolbOrg large barrels and ships are made in very similar ways at least in terms of making them watertight, tight fitting planks either with nothing (rare) or a caulking (common) usually cordage soaked in pitch or tar. all of which seriously outgas under vacuum. barrels work much better for our purposes because they are reinforced on the outside relying on compression to seal them. they can withstand some internal pressure, ships are pegged/bolted into place so will be even weaker to internal pressure. $\endgroup$
    – John
    Sep 17, 2021 at 23:37
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    $\begingroup$ @MolbOrg: The hull of a ship is stressed in compression. Water wants to come in under some pressure, you want to stop it. It is not hard to make a strong vessel able to resist outside pressure. Making a vessel able to conain inside pressure is a very different problem; atmospheric pressure is 1 kg / square centimeter, meaning 10 tons per square meter. That's an awful lot of force for a pre-modern container. (For example, the wind chests of a pipe organ held compressed air at about 0.007 atmospheres; yes, 7 millibars.) $\endgroup$
    – AlexP
    Sep 18, 2021 at 0:12

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