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?
Because 1) there was no perceived value to balloons, 2) why challenge any sky gods? and 3) this explanation:
Mesoamericans had inflated animal bladders. Chinese had “sky lanterns”. The French had wide looms.
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.
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.
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.
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.
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.
I’m a total stranger to the art of ballooning, but I’ll hazard a few thoughts.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.)
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 Gas Balloons History prior to the availability of propane, most balloons used gas (hydrogen mainly?) rather than hot air, but that’s not exclusive.
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.
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.