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Old 03-25-2020, 10:19 PM
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Why did it take us so long to invent flying in balloons?


I was reading a book on the history of technology and the author pointed out that a balloon is an incredibly simple invention. We had the basic technology that would have allowed us to make a balloon capable of carrying a person five thousand or more years ago.

It's not like it takes a major insight. People can see that smoke rises in the air. Why didn't anyone think of trying to contain some of that smoke in a cloth bag and seeing what happened?
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Old 03-25-2020, 11:10 PM
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Because 1) there was no perceived value to balloons, 2) why challenge any sky gods? and 3) this explanation:
Quote:
Hot air balloons that can carry people require very large amounts of fabric. They were first created a few decades after the "flying shuttle" made it possible for a single weaver to weave cloth wider than the weaver's arms -- and then made mechanized looms possible... The hugely increased availability of fabric has to be one reason the balloons were first made at that time.
Mesoamericans had inflated animal bladders. Chinese had "sky lanterns". The French had wide looms.
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Old 03-26-2020, 03:35 AM
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That explanation doesn't make any sense.

Ships with large sails have existed for thousands of years, and it was always possible to sew strips of fabric together. In fact, strips still had to be sewn together for a balloon, no matter how wide the loom.

The taffeta, linen, and silk used for early balloons was not significantly different from earlier hand-woven fabric, but may have been cheaper.
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Old 03-26-2020, 04:27 AM
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When I look at very old balloon pictures, the balloon looks very small. I think, among other things, they may have had trouble working out how large a balloon would be required. And the cost of cloth and paper. And -- it's clear that most people didn't understand the concept of 'hot air rises'. They didn't have a correct concept of air. The weren't able to differentiate between "flue gas" and "hot air", so they had no understanding that it was the 'hotness' or flue gas that created the wind, and mostly no clear idea of the difference between hot air/flue gass and fire draft.
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Old 03-26-2020, 04:31 AM
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Originally Posted by GreenWyvern View Post
The taffeta, linen, and silk used for early balloons was not significantly different from earlier hand-woven fabric, but may have been cheaper.
Cost may very well have entered into it. The first hot-air balloons, by the Montgolfier brothers was lined with paper. The brothers were, by the way, manufacturers of paper. Presumably they had a fair amount lying around, or could make it at wholesale prices.
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Old 03-26-2020, 06:17 AM
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I asked the very same question almost sixty years ago when chums and I played our own fantasy game set in medieval Europe. I announced that I was attacking their cities from hot-air balloons! They thought this was cheating.
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Old 03-26-2020, 07:37 AM
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It's not a balloon! Go outside and take a look!
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Old 03-26-2020, 08:00 AM
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What is required to make a hot air balloon that is flight worthy?

It appears that making the balloon material should be possible with sail making tech even if other fabric is used. And we had ropes by then and can make a basket, or a harness. But that's only part of it. We would need to be able to make a pretty substantial and controllable fire with a good updraft that wouldn't burn the craft supporting it. Perhaps not so easy as the fire would need to be hot enough, but the heat and sparks can't damage the balloon. Also a way to safely get back to the ground, some method to control the decent.

I suspect attempting to upscale it from fire lantern plus the landing requirement proved too difficult for materials available at the time.

Last edited by kanicbird; 03-26-2020 at 08:01 AM.
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Old 03-26-2020, 08:16 AM
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I'm a total stranger to the art of ballooning, but I'll hazard a few thoughts.

1. Method of heating the air. Sure, early second century BCE people may have noticed that hot air rises, but the heat sources at the time were pretty feeble and had a hefty weight-to-heat-output ratio. If you want a lot of heat from a coal or wood fire, you've got to lift a lot of coal or wood. Plus, you have to control and channel the heat effectively.

2. Perception of a technology as a "toy." I'm sure there are sociologists out there who have a technical term for this, but it's quite common for cultures to perceive a technology as a toy and not suitable for actual large-scale use. There are many stories about early aviation pioneers who studied fairly elaborate existing flying toys and decided to adapt their principles. As I understand it, wheeled toys may have existed among native American populations, but they rarely (if ever) used wheeled carts themselves. Laughing gas was a party novelty, as were early electrical batteries and Leyden jars. Someone has to say, "Hmmmm...look at that. You know...." This may take many years.

3. Cost and technology. Theoretically, I guess, one could say, "Why did it take so long to develop battleships? After all, iron has been used for thousands of years. You just have to put the iron together to make a battleship. The principle is simple." Practical balloons required the ability to create and coat/seal large quantities of lightweight fabric, the technology to heat the air, the scientific understanding of how big the envelope/bag needed to be for a given weight, etc. And there had to be a source of money to pay for such an unusual effort.
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Old 03-26-2020, 08:26 AM
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Chimneys didn't first appear until 12th century, and they didn't become commonplace until the 16th and 17th centuries. So the concept of warm air buoyancy and draft has only been relatively widespread for a few centuries at this point. Even with small scale examples of putting something over a fire making it go up wouldn't necessarily lead to the conclusion of capturing that force in an enclosed bubble and trying to lift something as heavy as a person with it. There's a lot of knowledge leaps required there. All that on top of the already mentioned difficulty in constructing a balloon without any prior knowledge, figuring out how to inflate it without catching fire, then how to control it without killing yourself.
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Old 03-26-2020, 09:27 AM
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Chimneys didn't first appear until 12th century, and they didn't become commonplace until the 16th and 17th centuries.
Roman bakeries had chimneys, and Roman buildings heated by hypocausts had chimneys. Hypocausts rely on the fact that hot air rises.

The Chinese had a similar system with the Kang bed-stove, which had a flue, from at least the 1st century AD.
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Old 03-26-2020, 09:41 AM
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But did knowledge of any of the Roman heating systems persist through history? I think those were only rediscovered much more recently, like much of their technology that was forgotten after the civilization collapsed.
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Old 03-26-2020, 09:43 AM
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Maybe some of the more advanced cultures did have flying balloons but no record or artifacts survived to inform us so.

Civilizations come and go and there are plenty of artifacts that did survive which we have no idea what they were for.

Last edited by MDfive21; 03-26-2020 at 09:44 AM. Reason: grammar
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Old 03-26-2020, 10:00 AM
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Maybe some of the more advanced cultures did have flying balloons but no record or artifacts survived to inform us so.

Civilizations come and go and there are plenty of artifacts that did survive which we have no idea what they were for.
That would be strange. If a balloon was flown that carried a person aloft, there is a good chance it would have survived at least as a legend if not drawings.
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Old 03-26-2020, 10:27 AM
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Your major technological challenge to make a workable balloon that will carry humans isn't the balloon (technically called an "envelope") it's the burner. You need to be able to generate quite a lot of heat in a manner that is both controlled and doesn't weight so much the balloon won't go anywhere. Burners approximating what they use today weren't possible until surprisingly recently in human history, because we didn't have that kind of fuel - in fact, propane, which Hank Hill could tell you is now what balloons use, wasn't used as a fuel until the 20th century.
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Old 03-26-2020, 10:35 AM
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Yeah, "hot air balloons can fly and carry payloads" has been known since antiquity: That's what a sky lantern is, after all. But then, "things with wings can fly and carry payloads" has been known for even longer. The difficulty is in scaling it up to where the payload can be a human.

And yes, probably the part that was hardest to scale up was the burner.

Although... What if the burner wasn't carried on the balloon? Could you fill a balloon with hot air while it's tethered to a chimney on the ground, and then let it rise? It won't stay up for very long, because the air will cool down again. But you might still be able to get some use out of a balloon that goes up for a bit and then comes back down.
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Old 03-26-2020, 10:48 AM
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That explanation doesn't make any sense.

Ships with large sails have existed for thousands of years, and it was always possible to sew strips of fabric together. In fact, strips still had to be sewn together for a balloon, no matter how wide the loom.

The taffeta, linen, and silk used for early balloons was not significantly different from earlier hand-woven fabric, but may have been cheaper.
I would suspect that seams are quite heavy. You, at least, double the amount of material for a cm or so plus you have the added weight of the thread which will, generally, be heavier than the threads which make up the cloth.

If using only scraps under 6", I wouldn't be surprised if you had doubled the weight, compared to using a single piece of cloth of the full size. (No actual math included in that guess, just gut.)
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Old 03-26-2020, 10:50 AM
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The first manned balloon flights were in the late 1700s but there's not a whole lot of information out there about how they were heated. Most histories jump from those early flights to the modern era where propane is available, but what of the time in between when ballooning was all the rage? Did they have little potbelly coal stoves? According to this page https://balloonfiesta.com/Gas-Balloons-History prior to the availability of propane, most balloons used gas (hydrogen mainly?) rather than hot air, but that's not exclusive.
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Old 03-26-2020, 11:48 AM
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When I look at very old balloon pictures, the balloon looks very small. I think, among other things, they may have had trouble working out how large a balloon would be required. And the cost of cloth and paper. And -- it's clear that most people didn't understand the concept of 'hot air rises'. They didn't have a correct concept of air. The weren't able to differentiate between "flue gas" and "hot air", so they had no understanding that it was the 'hotness' or flue gas that created the wind, and mostly no clear idea of the difference between hot air/flue gass and fire draft.
That's why I mentioned smoke in the OP. I realize it's hot air and not smoke which is rising; the smoke is just particles that's being carried up by the hot air.

But smoke is something that is visibly going up in the air. You don't have to develop a theory of air for it. You can see it happening. It's like building a raft; people figured out a way to use a moving current without understanding why it's moving. People could have taken the same approach to flying; just take advantage of something that's already going up.
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Old 03-26-2020, 11:50 AM
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Your major technological challenge to make a workable balloon that will carry humans isn't the balloon (technically called an "envelope") it's the burner. You need to be able to generate quite a lot of heat in a manner that is both controlled and doesn't weight so much the balloon won't go anywhere. Burners approximating what they use today weren't possible until surprisingly recently in human history, because we didn't have that kind of fuel - in fact, propane, which Hank Hill could tell you is now what balloons use, wasn't used as a fuel until the 20th century.
Yup. Same reason that despite the fact that it's been known for thousands of years that trapped hot steam can do a lot of work, steam engines (outside of novelties) did not become commonplace until the 1700s. Since metallurgy needed to advance to the point that practical pressure vessels could be made.


We often describe inventions and new technologies as being the result of dozens of inventions and innovations over time rather than one single breakthrough. That is accurate, however, there are often individual crucial technologies that make something practicable. Like burners for hot air balloons.
In our own time this fact is one of the reasons that nuclear proliferation has not been as widespread as it was once feared, by restricting access to a handful of key techniolgies.
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Old 03-26-2020, 12:24 PM
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Yeah, "hot air balloons can fly and carry payloads" has been known since antiquity. [...] The difficulty is in scaling it up to where the payload can be a human.

And yes, probably the part that was hardest to scale up was the burner.
That’s a good point, but scaling the envelope was also nontrivial. I’d argue that doing so was infeasible prior to the appearance of cheap, strong, consistent paper. I don’t think it’s a coincidence that practical human-scale balloon flight first appeared around the time of the industrial revolution.

Balloon flight at any scale requires materials with uncommonly good strength-to-weight ratios. Beyond silk, I can’t think of a natural material in the right ballpark. Even then, in a world without balloons, it’s not obvious that any silk bag full of air could ever lift itself (no matter how hot the contents).

Paper was the first practical material for balloon envelopes that I’m aware of. The Chinese, who had plenty of silk, made most of their balloons from paper (AFAIK). The Montgolfier brothers started out with taffeta, but moved to paper almost immediately—and didn’t look back.

I’d argue that the appearance of large-scale ballooning depended upon on paper manufacturing at an industrial scale. Without that, there was no known material strong enough—I mean consistently strong enough—to pull it off.

Prior to the invention of synthetic polymers, balloons were a lot more challenging from a materials science perspective than contemporary heavier-than-air machines. Aside from paper and silk, we had almost no thin, strong fibers or films until after WWII.

The Germans didn’t build the Hindenburg out of cow guts, hydrogen*, cellulose and thermite because they were quirky or unaware of how fire works. There were simply no other options.



* I know—the Germans used hydrogen because the Americans wouldn’t sell them helium. But helium is less buoyant than hydrogen and only exacerbates the strength-to-weight problem.
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Old 03-26-2020, 12:32 PM
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Perception of a technology as a "toy." I'm sure there are sociologists out there who have a technical term for this, but it's quite common for cultures to perceive a technology as a toy and not suitable for actual large-scale use. There are many stories about early aviation pioneers who studied fairly elaborate existing flying toys and decided to adapt their principles. As I understand it, wheeled toys may have existed among native American populations, but they rarely (if ever) used wheeled carts themselves. Laughing gas was a party novelty, as were early electrical batteries and Leyden jars. Someone has to say, "Hmmmm...look at that. You know...." This may take many years.
Years from now people will be asking why it took so long for robot servants to be put into everyone’s homes, when robot toys (programmable and/or voice command) were around for so long.
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Old 03-26-2020, 01:00 PM
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Remember 2 things - industrialization and technology. yes, the ancients had paper- but until it was being made by machines in industrial quantities, every square yard was made by hand. If the merchant was lucky, he had water power to help some of the heavy lifting. Ditto for cloth - look at a decent sized Mongolfier balloon, there's enough paper to keep a monastery going for a year, and enough cloth to cover a small village. Not to mention hundreds of feet of ropes... Also - all this stuff weighs something. Industrial machine works can consistently make reliable rope, or paper, or cloth, strong yet light enough in quantity. Burner? Need a lightweight metal bucket that can hold a fire - until modern metallurgy, producing things like sheet steel was very difficult and expensive.

Sails are a bad counterexample - they had to be heavy to stand up to squalls and gusts without tearing. A balloon probably uses the thinner, much lighter fabric - the sort that was at a premium for women's fancy dresses. (i.e. expensive)

The issue is we tend to forget the cascade effect of the growing industrial revolution in Europe. When everything had to be made and moved by hand or beast of burden, items were relatively expensive. To make iron, once you've denuded the countryside, requires coal. Unless you and the coal mine are on a fortuitous waterway, the best that can be done is to cut coal by hand, haul out of the mine by pulley, haul it by cartload and hope the oxen can get the loaded cart through the mud ruts if it recently rained... ditto for the iron ore. The bellows were operated by hand, and the hammers for beating the iron... etc. In middle ages and earlier, metal was precious - all those Greek ruins have pits in the pillars where locals dug out the lead anchors that held the drums together, once adult supervision disappeared during times of strife... heck, people still steal any copper not nailed down, and much that was.

the other problem alluded to - when everything was done by hand, slaves were the "hands". Thus any physical practical work was looked down on as menial and beneath a thinking intellectual. So a Brainiac of the Roman empire would probably ask his slaves to make something like that, and odds are the slaves would not grasp the nuances of making a practical device. (Or didn't care, or were happy to build something badly that might kill the master.) To top that off, practicality reigns. What good is a hot air balloon? The Mongolfiers were just having fun. If the balloon carried you twenty miles away, someone had to follow in a cart (or several) to collect the balloon and haul it back - it didn't automatically return. A tethered balloon has to lift a spool of rope that lets it float above arrow range, if you're going to use it as a shooting platform (and enough ammunition to make a difference, and hope the base doesn't get overrun while you're up there...)

Similarly iron boats - what good are they until you have to defend against canon? And canon in the first few years were liable to blow up until the metallurgy caught up with the need. Again, making enough iron to build a decent sized ship requires industrial technology. And rivet or welding technology. Similarly for steam engines. The early days of steam are full of stories of badly made boilers and bursting vessels or pipes. Before giant foundries and mass production, consistent quality metal was always an issue - and it was too expensive to fiddle with for fun. The evolution of mechanization follows a predictable path of response to real need resulting in refined or new devices. Necessity, not tinkering, is the mother of invention.

(I had a discussion with a history prof who offered a "History an technology" course years ago. Romans didn't put big catapults on warships because the recoil would twist the spine of the ship, loosen the planking so it leaks, etc. It just didn't work. Firing down the length of the ship interfered with the rigging that held up the mast, and severely limited your aim, especially if you were trying to aim into the wind. Plus, you had to carry a lot of big rocks, which slowed you down for maneuvering.)
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Old 03-26-2020, 01:27 PM
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Helium is less buoyant than hydrogen, but not by very much. The important point is that either one is a small percentage of the density of air. On the other hand, hydrogen isn't actually all that dangerous as a lifting gas, and it's a fair bit cheaper than helium.
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Old 03-26-2020, 01:33 PM
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Years from now people will be asking why it took so long for robot servants to be put into everyone’s homes, when robot toys (programmable and/or voice command) were around for so long.
I don't see this as a valid analogy. Robots (as far as we know) are a complicated technology. Balloons are not. You can explain how a balloon works to a preschooler.
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Old 03-26-2020, 01:41 PM
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2. Perception of a technology as a "toy." I'm sure there are sociologists out there who have a technical term for this, but it's quite common for cultures to perceive a technology as a toy and not suitable for actual large-scale use.
I think you might be on to something, but I’d speculate that this isn’t a characteristic of particular cultures, but usually a manifestation of individual insecurity.

Nearly every time I hear something dismissed as a “toy,” the speaker is a blustery man who’s out of his technical depth.

I design scientific instruments for work; I’m also an amateur photographer. Some inexpensive lenses happen to have extraordinary optical quality, and I routinely hear amateur men (almost never women or working professionals of any stripe) dismiss those lenses as “just toys.”

You can make a heck of a scientific instrument out of a sewing needle and a buzzer from a broken smoke detector: an atomic force microscope, which is a really useful addition to any home nanotech research lab.

Technically competent people value result/data quality above almost all else. When the results are solid, dismissing the instruments as “toys” isn’t a great look. It implies that the speaker doesn’t understand what he’s looking at.

Sure, each society has cultural biases that can play a big role in which technologies it adopts. And while this can create dangerous blind spots, they tend not to last long.

There’s a long tradition of seeking out and exploiting technological blind spots. The Greeks fooled the famously martial Trojans by exploiting their preconceptions about what’s a threat and what isn’t.

Hint: not all weapons are sculptures, and not all sculptures are weapons. But some sculptures are definitely weapons. Especially the big, horsey kind.
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Old 03-26-2020, 01:42 PM
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Great post, md2000!

A few notes:

Sails - the point was that the width of a loom of was not a factor.

Quote:
To make iron, once you've denuded the countryside, requires coal.
Coppicing was a sustainable method of harvesting wood indefinitely without denuding the countryside, widely used for many centuries.

Wood could be used to make charcoal. Charcoal burners still worked in parts of England well into the 20th century, making charcoal in small-scale operations in the traditional way. The charcoal was used in smelting furnaces, by blacksmiths, etc.

Quote:
Romans didn't put big catapults on warships
That depends what you mean by catapults. They didn't use trebuchet-type stone throwers or onagers on ships, but they did use large bolt-firing catapults (ballistae). These could also be used to fire small stones with great force and accuracy.
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Old 03-26-2020, 01:42 PM
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Yup. Same reason that despite the fact that it's been known for thousands of years that trapped hot steam can do a lot of work, steam engines (outside of novelties) did not become commonplace until the 1700s. Since metallurgy needed to advance to the point that practical pressure vessels could be made.
But you don't need metallurgy to make a balloon. You can make a balloon out of silk. And silk production is a technology so old it predates writing.
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Old 03-26-2020, 01:48 PM
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Remember 2 things - industrialization and technology. yes, the ancients had paper- but until it was being made by machines in industrial quantities, every square yard was made by hand. If the merchant was lucky, he had water power to help some of the heavy lifting. Ditto for cloth - look at a decent sized Mongolfier balloon, there's enough paper to keep a monastery going for a year, and enough cloth to cover a small village. Not to mention hundreds of feet of ropes... Also - all this stuff weighs something. Industrial machine works can consistently make reliable rope, or paper, or cloth, strong yet light enough in quantity. Burner? Need a lightweight metal bucket that can hold a fire - until modern metallurgy, producing things like sheet steel was very difficult and expensive.
This. Even if conceived of in prior times the cost would have been too high. There must have been numerous times people somehow got a small bag of cloth or paper into the air over an existing fire, and even conceived of the bag large enough to carry a person and a flame aloft, but it required wealth and technical prowess to carry that concept through experimentation and into reality, and the Montgolfiers were blessed with both.
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Old 03-26-2020, 02:02 PM
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Chimneys didn't first appear until 12th century, and they didn't become commonplace until the 16th and 17th centuries. So the concept of warm air buoyancy and draft has only been relatively widespread for a few centuries at this point.
Smoke holes were used before chimneys, and also require the (fairly obvious) concept that smoke rises.

To what extent this leads to the conclusion that warm air rises whether or not smoke is involved may be uncertain*; but I doubt the difference has much to do with chimneys in particular. Anybody who's ever looked at a fire knows that smoke rises.
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Old 03-26-2020, 02:13 PM
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I don't see this as a valid analogy. Robots (as far as we know) are a complicated technology. Balloons are not. You can explain how a balloon works to a preschooler.
Balloons are only simple when it comes to basic lift. When it comes to manufacturing in the pre-industrial era, nothing was simple. The principles of the steam engine are very simple as well, and we had demonstrated steam's ability to do work when the aeolipile was developed in Egypt in the first century. But it took a thousand years for the first steam-powered device, which was an organ. Many inventors including Leonardo Da Vinci talked about steam turbines, steam cannons and all sorts of steam devices, but it wasn't until 1698 that the first practical steam engine was developed.

To get there we needed advances in metallurgy, thermodynamic science, understanding of pressure and work, pistons, vacuum, yada yada. But we also needed precision machining and repeatable processes, which are fairly recent innovations.
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Old 03-26-2020, 02:20 PM
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Helium is less buoyant than hydrogen, but not by very much. The important point is that either one is a small percentage of the density of air. On the other hand, hydrogen isn't actually all that dangerous as a lifting gas, and it's a fair bit cheaper than helium.
Oh, absolutely. We fully agree about all of this. I mentioned it partly to illustrate extreme and less-than obvious requirements demanded of balloon envelope materials.

That said, hydrogen offers about 8% more lifting capacity than helium. You can fly an airship filled with either, of course; the technology was sufficiently advanced by the time dirigibles showed up. 8% more lifting power is a lot like having 8% less weight to lift, and that would be a huge deal even now. The margins have always been tiny.

I mention the difference only because I think it helps illustrate my answer to the original question. Nonexistent or tiny material margins are part of the reason we didn’t see human-lifting balloons earlier than we did.
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Old 03-26-2020, 02:29 PM
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But you don't need metallurgy to make a balloon. You can make a balloon out of silk. And silk production is a technology so old it predates writing.
Silk has great material properties, but translating those numbers into a practical gas bag is harder than you might appreciate.

As I said earlier, the Chinese had access to both and overwhelmingly used paper for their balloons. Silk isn’t the slam-dunk you seem to think it is.
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Old 03-26-2020, 03:03 PM
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I don't see this as a valid analogy. Robots (as far as we know) are a complicated technology. Balloons are not. You can explain how a balloon works to a preschooler.
I doubt very much that you can explain how to construct a proper burner used in a balloon vehicle. It’s not a camp fire in a basket.

Even the concept of heat making things rise is not something intuitive to people, let alone children. You could demonstrate it, but there’s a difference between showing that something works and explaining how it works.

My point wasn’t that balloons are robots. My point is that people estimate how difficult it is to scale up from a toy. An example made in this thread is a wheeled toy used by cultures that don’t use carts. A cart needs to be made of materials sturdy enough to bear weight but light enough to push with minimal effort. You need a flat, level surface (roads) to move it any appreciable distance. How do you keep it from falling apart when it jounces around with a lot of weight in it? These are things that people needed to figure out in order to implement something we might take for granted as simple.
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Old 03-26-2020, 03:10 PM
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Nazca Lines & the World’s First Hot Air Balloon: A Theory of Ancient Flight in Peru & Nazca Desert Mystery

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Woodman theorized that the magnificent geoglyphs would not have been made if the Nazca people themselves could not have appreciated the results of their labors... Woodman became convinced that the Nazca people had taken flight....

While not as outlandish as Erich von Däniken’s extraterrestrial orientated Nazca theories, Woodman’s hot air balloon concept is largely discredited...

Referring to the successful flight, Julian Nott himself stated: “while I do not see any evidence that the Nazca civilization did fly, it is beyond any doubt that they could have. And so could the ancient Egyptians, the Romans, the Vikings, any civilization”.
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Old 03-26-2020, 05:15 PM
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You don't need to fly to see the Nazca lines. Up on the nearby mountainside will serve just fine.

And "not as outlandish as von Däniken" isn't saying much.
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Old 03-26-2020, 06:29 PM
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When I look at very old balloon pictures, the balloon looks very small. I think, among other things, they may have had trouble working out how large a balloon would be required. And the cost of cloth and paper. And -- it's clear that most people didn't understand the concept of 'hot air rises'. They didn't have a correct concept of air. The weren't able to differentiate between "flue gas" and "hot air", so they had no understanding that it was the 'hotness' or flue gas that created the wind, and mostly no clear idea of the difference between hot air/flue gass and fire draft.
Indeed, the Montgolfier brothers, the ones who were to ballooning what the Wright brothers were to airplanes, initially thought it was SMOKE that caused the balloons to rise.

It takes an enormous amount of hot air to get even one person off the ground and prior attempts just didn't use a big enough balloon. Much like early attempts at fixed-wing flight typically just didn't have enough wing area to generate the lift needed to glide, much less actually fly.
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Old 03-26-2020, 06:41 PM
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Balloons are only simple when it comes to basic lift. When it comes to manufacturing in the pre-industrial era, nothing was simple. The principles of the steam engine are very simple as well, and we had demonstrated steam's ability to do work when the aeolipile was developed in Egypt in the first century. But it took a thousand years for the first steam-powered device, which was an organ. Many inventors including Leonardo Da Vinci talked about steam turbines, steam cannons and all sorts of steam devices, but it wasn't until 1698 that the first practical steam engine was developed.

To get there we needed advances in metallurgy, thermodynamic science, understanding of pressure and work, pistons, vacuum, yada yada. But we also needed precision machining and repeatable processes, which are fairly recent innovations.
I agree this is true for a steam engine or a robot. But a balloon is not a steam engine or a robot. In terms of complexity, a balloon is comparable to a ladder or a chair. It doesn't have any moving parts and if you get it only ninety percent right, it'll still do the job.
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Old 03-26-2020, 06:44 PM
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I mention the difference only because I think it helps illustrate my answer to the original question. Nonexistent or tiny material margins are part of the reason we didn’t see human-lifting balloons earlier than we did.
I understand why we didn't have hydrogen or helium balloon earlier than we did. But I was asking about hot air balloons.
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Old 03-26-2020, 07:28 PM
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You don't need to fly to see the Nazca lines. Up on the nearby mountainside will serve just fine.

And "not as outlandish as von Däniken" isn't saying much.
Clearly the ancient astronauts were landing their spacecraft on the nearby mountainside. Thank you for that clarification Chronos.
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Old 03-26-2020, 09:54 PM
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Which came first, hot-air balloons or balloons carried aloft by helium/hydrogen?

On a related note, I suggest that people interested in early ballooning check out The Aeronauts on Amazon Prime. The two main characters are carried aloft in a hydrogen balloon. Their mission was to study the weather at altitude and use that information to make predicting the weather on the ground more accurate.

One hypothesis I found interesting was that the two people in the balloon were unprepared for the extreme cold found at high altitudes. They knew that it gets cooler as one rises, but the hypothesis was that that would change and eventually temperatures would get very warm. They based this on the fact that they were closer to the sun. Of course, while that was true, they had no idea that they were closer by a trivial amount. The sun is much farther away than they imagined.

Still a good movie.
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Old 03-26-2020, 11:12 PM
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Wikipedia says that the Montgolfier's first human-carrying balloon was 790m^3 which I calculate to be about 5.5m radius or about 35 feet in diameter. That's huge by the standards of the day, consuming a vast amount of paper and fabric. (I leave it to the reader to find the surface area of said sphere... ) While silk would be airy light it would probably cost a king's ransom. Plus, such fabrics likely need the paper lining to make the fabric sufficiently airtight.

It seems their early experiments got off the ground by using a fire on the ground until the balloon was fully charged. They later added a burner in the basket, only to have the first flight cut short because they then had to extinguish the fire and keep sponging the bottom of the balloon to avoid sparks setting it ablaze.

Remember when considering metallurgical and machining mass production that it was only around 1800 that Eli Whitney, after drinking some cotton gin no doubt, managed to demonstrated interchangeable parts - multiple parts made to the same spec so they could be switched from one gun to another. (Recent analysis shows he actually cheated). things we take for granted are not so trivial.

The point was that catapults have a recoil - the bigger the pult, the bigger the jolt. Those of us used to metal or fibreglass one-piece boat hulls don't appreciate what a work of art a wood boat made of multiple planks and beams would be. Such a construction, unless excessively over-engineered, is susceptible to damage ranging from loss of watertightness to unplanned disassembly if subject to pulses of lateral torque. This limited the size of the catapult and the ammo. Cross-bow type assemblies have less of this complication.
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Old 03-27-2020, 12:11 AM
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I understand why we didn't have hydrogen or helium balloon earlier than we did. But I was asking about hot air balloons.
Ah! Now I see the source of the confusion!

The things I’ve said about the structural demands of balloon envelopes apply equally whether the lifting medium is hot air or light gas. The stresses on the envelope are independent of what’s used to fill it. Is that clearer?
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Old 03-27-2020, 02:00 AM
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The point was that catapults have a recoil - the bigger the pult, the bigger the jolt. Those of us used to metal or fibreglass one-piece boat hulls don't appreciate what a work of art a wood boat made of multiple planks and beams would be. Such a construction, unless excessively over-engineered, is susceptible to damage ranging from loss of watertightness to unplanned disassembly if subject to pulses of lateral torque. This limited the size of the catapult and the ammo. Cross-bow type assemblies have less of this complication.
Um... we are talking about large crossbow-type catapults - ballistae - as I stated clearly, contrasting them with other types. Like crossbows, these have almost no recoil.

Roman ships were constructed using the mortise-and-tenon method, with an inner supportive framework, so the hulls were strong and durable, and not at all fragile - especially warships, which had to be able to withstand the shock of ramming. Large merchant ships could carry hundreds of tons of cargo.

Big Ships, Boarding, and Catapults by William M. Murray (Oxford Scholarship Online):

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Traditionally, the use of catapults (both bolt and stone projectors) and boarding tactics were thought to account for the production of larger and larger warships during the Hellenistic period. While larger warships allowed for an increase in carrying capacity for both catapults and deck troops, no ancient evidence supports the modern claim that catapults negated the role of ramming warfare and thus led to boarding tactics. Naval artillery weapons were generally limited to small calibers (especially stone projectors) and, to judge from Philo, were used primarily to target deck fighters and siege machinery, not oarcrews.
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Old 03-27-2020, 04:50 AM
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Originally Posted by EdelweissPirate View Post
Ah! Now I see the source of the confusion!

The things I’ve said about the structural demands of balloon envelopes apply equally whether the lifting medium is hot air or light gas. The stresses on the envelope are independent of what’s used to fill it. Is that clearer?
It's clearer but I'm not finding it persuasive. As we've noted, it's possible to make a balloon out of silk and silk has been available for millennia.

So any argument based on the idea that people didn't build balloons because they lacked the resources seems untenable to me.
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Old 03-27-2020, 07:56 AM
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It's clearer but I'm not finding it persuasive. As we've noted, it's possible to make a balloon out of silk and silk has been available for millennia.

So any argument based on the idea that people didn't build balloons because they lacked the resources seems untenable to me.
The resource in that case is MONEY. Silk was and still is incredibly expensive. Why hasn't anyone invented carbon fiber road paving yet? Titanium bridges? Those are known materials, but such uses would be so monumentally expensive that nobody's even looking at them as a possibility. Same with those in historical times not considering building a balloon out of a royal family's wardrobe's worth of valuable silk.
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Old 03-27-2020, 09:43 AM
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It's clearer but I'm not finding it persuasive. As we've noted, it's possible to make a balloon out of silk and silk has been available for millennia.

So any argument based on the idea that people didn't build balloons because they lacked the resources seems untenable to me.
Silk breathes, That's not good for a balloon. What it does have is better tensile strength than paper, less likely to tear. hence, fabric balloons lined with paper for air-tightness. But for proper anchoring, this is contained in a net of rope, since even silk has limited tear resistance and holding a few hundred pounds of basket, passengers, and fuel is not something to be trusted to a sheet of silk.

But then - 35-foot diameter balloon needs about 380 square meters of cloth and fabric. Before automation that was a king's ransom - especially when you look at how silk is made. Even today that would be several thousand dollars. Hand-made paper would probably be expensive too.

Before the industrial revolution and the agricultural revolution, just getting enough food was often a struggle. Surpluses were more often spent on permanent things like statues of the leader or city walls, not on something that might catch fire and destroy the equivalent of a life's earnings.

who knows how many people thought about it, and even tried scaled down versions. AFAIK Leonardo drew some very nice ideas for tanks, helicopters, and birdman outfits, etc. but never actually tested them or built even scale models - he just doodled while musing "this should work, you would think..."
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Old 03-27-2020, 10:46 AM
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Which came first, hot-air balloons or balloons carried aloft by helium/hydrogen?
Hot air. When the Montgolfiers sent up their first big balloons, hydrogen could not be produced in such quantity (heck, it had only just recently been NAMED "Hydrogen") and helium was a century from being discovered.
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Old 03-27-2020, 07:40 PM
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It's clearer but I'm not finding it persuasive.
That’s disappointing. I have a passing familiarity with structures and materials, and I’m not exactly afraid to go into detail on this stuff. But you’re not persuaded. Ok.

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As we've noted, it's possible to make a balloon out of silk and silk has been available for millennia.
Right. And myself and others have explained why that is harder than it seems. But you’re not persuaded.

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So any argument based on the idea that people didn't build balloons because they lacked the resources seems untenable to me.
I’m not even sure what that means in this context. Is it possible that you’re not persuaded because you’ve decided not to be?

To be clear, I’m happy to engage with any earnest questions or objections you might have.
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Old 03-27-2020, 07:54 PM
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Hot air. When the Montgolfiers sent up their first big balloons, hydrogen could not be produced in such quantity (heck, it had only just recently been NAMED "Hydrogen") and helium was a century from being discovered.
According to Wikipedia professor Jacques Charles and the Robert brothers launched a manned hydrogen balloon on December 1, 1783. Only a couple months after the Montgolfiers.
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