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Let's say we have a society that for some reason (a MacGuffin, Unobtanium, Handwavium, whatever) have found a way to travel off the earth without having to fight gravity along the way. They can travel into orbit as easily as they can sail the seas or travel along a road.

What kind of technologies would they need in order to get into orbit and travel around the Earth from space? Space is still a cold, radioactive vacuum so there are still a bunch of hurdles of overcome.

But from what I know, the biggest hurdle has been (and still is) the prohibitive cost and difficulty of pushing something away from the Earth. So if we remove it...

  • Could we have medieval vessels in space? (I seriously doubt this)
  • Could (adapted) 19th century Ironclads make it?
  • Could a WWI era warship do it?
  • Or would we only shave a few years off the technology requirements?

What hurdles would still need to be overcome? When could it be done?

These vessels being able to reach any kind of stellar body isn't a requirement by the way. Chugging around in orbit is more than enough for what I had in mind.

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    $\begingroup$ You're looking for Cornelis Jacobszoon Drebbel, builder of the first submarine in 1620 $\endgroup$ – Separatrix Feb 18 '16 at 15:58
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    $\begingroup$ Check out "The Road Not Taken" by Harry Turtledove. The aliens manage interstellar conquest with otherwise Age of Sail equivalent technology. $\endgroup$ – Travis Christian Feb 18 '16 at 15:59
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    $\begingroup$ Mandatory XKCD. $\endgroup$ – Frostfyre Feb 18 '16 at 16:02
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    $\begingroup$ You can't be in orbit if you aren't relying on gravity. $\endgroup$ – a CVn Feb 19 '16 at 9:06
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    $\begingroup$ The question is a bit vague - can you define the exact requirements of the situation? Are we to assume that reentry, manoeuvring in space and orbital velocities are also not an issue for the same reason as getting to space in the first place? Is the question literally "If you remove the difficulties of getting to space and from space (and staying in space), what technological level could survive in space?" $\endgroup$ – Ieuan Stanley Feb 19 '16 at 9:26
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Assume that the ship is deposited in a stable Low Earth Orbit (LEO).

  • The vessel would have to be sealed against pressure. Considering that submarines became practical at the turn of the 20th century, spaceships should be workable for a time. Watch out for slow leaks, and the need to replace your atmosphere.
  • The vessel would have to cope with the temperature effects of vacuum. Contrary to myth, space isn't cold as ice, and there is no convection to cool the vessel. Overheating in the sun could be just as much as a problem as freezing in shadow, and the seals will suffer (see above). I guess that early 20th century technology could cope for a time. 19th century technology might have trouble.
  • Maintaining a breathable atmosphere will be similar to the challenges on early submarines. Again, turn of the 20th century technology, or perhaps a few decades earlier. Air circulation will be an unexpected problem, but after a few accidents people will learn the pitfalls.
  • A side effect is managing humidity. Expect molds in the corners.
  • This could be powered by batteries.

Summarized, a late ironclad or early sub should be able to cope for a couple of days.


Regarding Todd's question, it would be possible to mount an array of small solid fuel rockets, or perhaps cold gas thrusters. A liquid fuel rocket would be difficult. But the orbit should remain stable far longer than the environment.

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  • $\begingroup$ Since your ship is staying in LEO, could a snorkel be dropped down into the atmosphere to provide breathable air? $\endgroup$ – Henry Taylor Feb 18 '16 at 17:14
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    $\begingroup$ @HenryTaylor I like that thinking but A) the snorkel would have to be very long and able to withstand a lot of stress and heat build-up from friction of being dragged through thick enough atmosphere so fast, B) there's a maximum length for a usable snorkel and this would exceed it, and C) the resulting drag would degrade the orbit quickly enough to require a lot of fuel spent maintaining the orbit. $\endgroup$ – Todd Wilcox Feb 18 '16 at 17:37
  • $\begingroup$ What about thrust for orbital maintenance and manouvering? $\endgroup$ – Todd Wilcox Feb 18 '16 at 17:38
  • $\begingroup$ @ToddWilcox Actually, if you could solve A and B, C could solved by having the snorkel act like an Electrodynamic Tether and actually provide thrust to the ship. $\endgroup$ – AndyD273 Feb 18 '16 at 18:16
  • $\begingroup$ @AndyD273 This would make C even worse. Electrodynamic tethers work by converting kinetic energy to electricity. Losing kinetic energy is a fancy way of saying "drag", and you would need more fuel to recover the kinetic energy and stay in orbit. $\endgroup$ – Eldritch Cheese Feb 18 '16 at 20:45
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Submarines

Self contained airtight vessels for the carrying of human occupants

While Aristotle said Alexander the Great used a diving bell in the 4th century BCE, the first self contained submarine was built by Cornelis Jacobszoon Drebbel in 1620 based on a William Bourne design from 1578. This submarine was only able (in possibly exaggerated tales) to submerse to around 4-5m, meaning in wasn't able to withstand the minimum of 1atm of pressure difference to survive orbit (1atm at around 10m depth). It was also designed to keep water out rather than air in. There was a combat suitable Russian design in 1720 that could be the first we'd recognise today as a proper submarine, but again the navy didn't take it on.

This gives us a time period for the earliest reasonable airtight vessel 1620-1720

Movement in space

Riding the firework

Fireworks have been around since the 7th Century. All you have to do is turn them round, stick them to the outside and fire off small numbers to allow maneuvering. Leaving off the bit at the end that makes them go bang, which could be uncomfortable. They'll probably try this at least once, it doesn't work of course, it needs air.

Compressed air

You'll need to develop some sort of reaction drive system. Since compressed air systems have also been around since the 18th century, possibly much earlier, a gas powered system is not impossible. However the drive system is probably the hardest bit for us to consider at that time period as there are no suitable transferable technologiescitation needed.

Orbital mechanics and re-entry

Applied handwavium!

The unobtainium that got us up here is keeping us up here and it's going to get us back down again as well. Since it handwaved all the way up, there's no reason to hit orbital speeds to stay up, this means that re-entry speeds aren't a problem since we never hit those speeds anyway.

In conclusion

Early 1700s, but they'd need to invent maneuvering thrusters.

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The first manned spacecraft that humans launched was Vostok 1 in 1961, which orbited the earth for 108 minutes (roughly two hours). Using this as the baseline of a 'spaceship', a human could likely have survived in space as early as the 4th century BC.

Air

A person inhales and exhales roughly 15 cubic feet of air per hour. To survive two hours, a person would need 30 cubic feet of air. With a typical adult male human body occupying a volume of ~3 cubic feet, a sphere of four foot diameter would easily hold a person and enough air to survive two hours in space.

Diving bells were used as early as the 4th century BC, which means that technology of the time could produce a shell that was air tight.

Since the spacecraft wouldn't need to resist the water pressure a diving bell would need to resist, it's possible that some type of airtight(ish) bladder / balloon could be large enough to hold both a person and two hours of air at a much earlier time.

Even if the bell / bladder wasn't completely airtight, coating the bell / bladder with pitch would have provided enough of a seal to prevent too much air loss.

After two hours CO2 buildup in a craft of this volume would start to pose a danger, but the occupant could certainly survive such a flight. An arbitrarily larger bell / bladder could extend the time of this flight almost indefinitely.

Heat

Since vacuum is an excellent insulator, an additional heat source wouldn't be necessary. Furs or other heavy clothing would be sufficient to keep the occupant of the craft warm.

As the craft becomes larger and the outside surface area increases, the body heat of the occupant could not extend the flight indefinitely. Without an additional heat source, the body heat of the occupant could not extend the flight indefinitely.

Still, with careful heat management, good insulation, and perhaps preheated objects to supplement the occupant's body heat, the occupant could perhaps survive a full day before the craft radiated too much heat and the occupant froze to death.

Radiation

Who cares? Worrying about an increased risk of cancer in old age is a thoroughly modern concept.

Reentry

This is a tough one with traditional power sources, but we don't have the same limitation here. A limitless power source would allow the craft to re-enter the atmosphere at an arbitrary speed, so re-entry heating issues don't need to be considered.

Additionally, if care were used the heat problem above could be mitigated (using atmospheric friction to warm the craft) making the volume of the craft (and air contained within) the primary limiting factor of flight time.

Other needs

For a two hour round trip, a person would be able to survive with nothing more than air and warmth. Additional comforts like light, food / water, or hygiene would be secondary and could be addressed in one way or another. The occupant wouldn't have to be happy or comfortable, but people can survive a significant amount of discomfort.

Other thoughts

This certainly wouldn't be the safest or most comfortable way to travel into space, but historically the value of life hasn't been particularly high. An ancient general / civilization would probably think little of sending dozens or hundreds of men to their deaths in a such a manner, and in all likelihood many would survive their trips into space.

Time to and from orbit might be a concern as well, as such craft wouldn't be able to travel at high rates of speed in the lower atmosphere, but it probably wouldn't change this considerably.

The actual mechanics of this craft would, of course, be dictated by the nature of the magical propulsion system.

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Space isn't exactly cold. It isn't hot either, because a vacuum can't be either.
Heat regulation is actually a big problem because of that vacuum, since heat can't be radiated off into the air. It would be like putting something into a vacuum thermos bottle. The heat on the inside stays on the inside except for a bit that radiates off as IR.

Being air tight is of course important, along with a way to filter out carbon dioxide.

I read somewhere that the theory of why air was important was around in the middle ages, though what made air good or bad was still a mystery. With antigravity allowing for flight early on, they probably would have figured it out sooner since hypoxia from traveling to high to quickly would have surfaced really early.

Radioactivity could be dealt with by sheathing the ship with lead, since weight isn't an issue. This of course mean's that they have to have a theory of radioactivity, which was discovered by Marie Curie in our timeline. Before that people would have gotten sick, and not had a clue why. This may have been harder to discover than the theory of gasses.

However, as long as they stay in low earth orbit, inside of the Van Allen Belt (1000 km), radiation will be less of an issue.

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I'd say Industrial Revolution for the first short experimental runs 1950s for long stays, and some time after that long stays that don't kill people, that's assuming there's no difference in technological advancement caused by exploring space. If you assume that once people start exploring space they'll push along the technologies they need to keep going (which it probably would) then by the mid twentieth century, 1940s say, you should have a fully fledged space program, one far more extensive that we have now.

The real issue is keeping the atmosphere in for that you need good gas seals that don't rely on volatile compounds that will boil off in a vacuum, that's very early 1950's technology in our world (first patents for dry-gas seals are from 1951). The rest of the technology in terms of keeping up air quality, flexible pressure hull alloys, long life powercells, etc... is submarine gear so possibly WWI, definitely by the end of WWII. As I said early industrial revolution precision rubber seals will hold for a while before the vacuum degrades them too badly which will let you get a start in the 1890s for o-rings, earlier for permanent seals, but you need dry-gas seals, a good pressure hull, etc... before long stays become possible.

Radiation shielding is a thing that they'll learn about the hard way just like we did in the 1940s and 50s with atomic power and it's easy enough to deal with, especially if you don't have to haul the weight of that shielding out of the gravity well.

Motors etc... are a separate issue since you don't actually need them. If you want them you need either self-oxidizing fuel or compressed gas, compressed gas you're talking the 1490s and Leonardo de Vinci. Self-oxidizing fuels are a slightly more modern invention say the 1810s for peroxide based liquid fuels. If you're okay with solid fuel motors that you use once and then dump you can go with nitrated black powder, or nitro-cellulose (gun cotton) for a more reliable burn rate, and they need to be really really well sealed against vacuum if you want them to be reliably there when you need them.

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A lot of answers have suggested looking to submarines for inspiration, but I would suggest instead that you look to steam. Boulton & Watts, circa 1800, had already mastered all the technology required to produce the physical vessel to go into space. Their pressure vessels, seals, energy management (heating and cooling) and extreme pressure variation handling would be sufficient to produce a vehicle that could survive in space if it could be raised with handwaveium and lowered on a tether. Adequate rocket propulsion for even basic control in space really didn't happen until the 1950's so there would be no significant time saving there, and without it, untethered space flight would be (and still is) impossible.

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In order to achieve space travel you need:

1. To be able to break free from the gravity well.

That was completely unachievable before the 50's - 60's. Just flying does not mean that one can leave the atmosphere.

We had balloons ever since the 1800's, and biplanes were around fora good 50 years before we had rockets capable of breaking orbit.

2. We need to survive space

So you've been shot out into space. Congrats! Enjoy the next 2 seconds of life, which is all you have left before dying an agonizing death.

In space you have incredibly cold temperatures, a notable absence of breathable atmosphere, and hard radiation that's capable of cooking you alive.

Some scientists today shake their heads at the very little protection the original astronauts had against space radiation. We definitely think it would be a big, big issue if we were to try to send people to Mars, for example. And that's with the technological advancements we've developed since the 50's.

How would people back then stay alive in space? Short answer? They wouldn't.

3. Communications

Let's assume that you were shot out of an enormous cannon into orbit, and that your 1800's diving suit is somehow keeping you alive for the time being.

How do you communicate with the Earth's surface. Rudimentary radio equipment - which was not around in the 1800's, by the way - will not suffice.

4. Getting back down

Once you've reentered the atmosphere you can simply deploy a parachute and float back down to the ground. However that first step is the dangerous one. Remember the Columbia? Yea.

Reentering the atmosphere requires a knowledge of advanced material science, and good navigation to boot. You need to be able to calculate the forces that your craft can handle very accurately.

Conclusion

The absolute prerequisite to handling space is the material science capable of producing the very high quality ceramics, polymers, and alloys which which will withstand being heated up to very high degrees, then cooled to arctic temperatures in mere minutes. Repeatedly.

Recycling your air supply, protecting against radiation, and all the rest won't even be issues if you can't solve that.

And that sort of material science involves very advanced knowledge of chemistry, and fine tuned industrial manufacturing processes.

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    $\begingroup$ the gravity well issue is explicitly solved by an unobtanium-handwavium alloy. $\endgroup$ – Serban Tanasa Feb 18 '16 at 16:10
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    $\begingroup$ Also, I believe that radiation is less of an issue below the the Van Allen belt, which starts around 1000 km up, and is higher than LEO at 160 km. While communication would be nice, anyone in the time of sailing ships would be used to not communicating... you could maybe do heliograph though... $\endgroup$ – AndyD273 Feb 18 '16 at 16:26
  • $\begingroup$ In LEO, heat is more of a problem than cold. Yes, you'll cool down when you're in the Earth's shadow, but your body heat can compensate for some of that. Heating up when you're in direct sunlight is rather more of an issue. $\endgroup$ – Mark Feb 18 '16 at 20:47
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The Vacuum is a Harsh Mistress

It is really hard to make something leak-proof and yet openable.

Space is big

Really big. Really Really Big. You'd need computers to navigate successfully even between planets in the same system. Moreover, you'd need engines, and control systems for engines...

You need metallurgy with micron precision and plastics for rubberized seal technology

My guess would be industrial-age technology, circa late 1800s or so. However, if gravity is not an issue, all sorts of 1km-high floating cities become possible. Why go all the way to space?

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  • $\begingroup$ Travelling to other planetary bodies was explicitly not required. $\endgroup$ – Erik Feb 18 '16 at 16:02
  • $\begingroup$ If you are manipulating gravity already, then there should be no need for any additional engine technology for a spacecraft. $\endgroup$ – a CVn Feb 19 '16 at 9:11
  • $\begingroup$ Rubber seals don't work in a vacuum, the VOCs boil off and the material disintegrates. I do agree that if the technique can be used for gravity defying architecture space isn't really worth the hassle. $\endgroup$ – Ash Aug 1 '17 at 13:40
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Presuming humanity wore nanocellular suits, which were at least restrictive in movement and able to clean their bodies, while maintaining a suitable environment for them locally (i.e. heat and pressure) any construct imaginable should suffice to be in space providing the vacuum/temperature would not damage the material as may be the case with cement/mortar structures.

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  • $\begingroup$ If you're waiting to get to nano-tech engineering levels you've already failed the the OP. $\endgroup$ – Ash Aug 1 '17 at 13:42

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