This is my first post on LessWrong as well as my Substack. Been sitting on this post for a while but finally dug up the courage to publish it today. Any feedback would be greatly appreciated!

Nice work! I spent some time thinking about the Montgolfier brothers a while back for similar reasons, and it's interesting to see your analysis.

Sporatic attempts at parachuting had taken place for 1500 years prior to the Montgolfier brothers' hot air balloon. But both the Montgolfier brothers' first hot air balloon demonstration and the first recorded public parachute jump took place in 1783, over 300 years since the first known depiction of a parachute. It's interesting that the parachute seems to have reached maturity at the same time as the parachute, rather than earlier, given the much longer history of parachuting attempts. It seems like a reasonable working assumption that something fundamental was permitting both to occur in 1783 - maybe advancements in textiles, aeronautics, or something else.

The first recorded parachute jump was by Louis-Sebastien Lenormand. His previous attempt was with two umbrellas, and his subsequent parachute jump was witnessed by Joseph Montgolfier. Lenormand had studied physics, was involved in the intellectual scene, and was apparently inspired by a tightrope-walker's use of a parasol for balance. Unfortunately, information about Lenormand's life is sketchy.

Medieval Europians had toy parachutes. Lenormand was embroiled in the French intellectual scene. He was a physicist. His first attempt using parasols seems to have been no more methodical than the attempt of the polymath Abbas ibn Firnas to use a big cloak to break his fall from a tower in 852. It connects the insight of the feeling of drag, the resemblance to bird wings, and perhaps knowledge of toy parachutes, to the possibility that a bigger, convenient sort of device might break the fall of a person.

There was a lot of conversation and images produced of parachute designs in the hundreds of years before Lenormand, so we needn't posit that Lenormand reinvented the idea.

Where Lenormand went further than Abbas ibn Firnas was in improving the device after his first attempt - upgrading from two parasols to a full parachute. And his improvement over, say, Leonardo da Vinci was in publicly testing a real working parachute.

I find it likely that that the coincidence of the Montgolfier brothers' and Lenormands' demonstrations in France in 1873 was no accident. There was something about that place and that time that motivated them. If I had to guess, it was something cultural: the idea of testing things in the real world, familiarity with hundreds of years of parachute designs, a critical mass of competitive and supportive energy in the nascent aeronautics space, increasing cultural familiarity with connecting physical intuitions with practical engineering to design"magical" machines.

My default assumption is that it took humans that long to get a clue (or shift a paradigm). We are remarkably bad at creating new thinking patterns. In my area of interest, fundamental physics, there are similar patterns aplenty. It took several decades to get from the first black hole metric to understanding black hole horizons, even though no new math was required. Similarly, it took several decades from EPR to Bell, and the math there was... very elementary. The most glaring example is the Euclid's Fifth Postulate (about parallel lines): It took some 2000 years (!) for mathematicians to notice what was literally in front of their eyes and under their feet: that there are cases where the first 4 postulates hold, but the 5th does not!

Montgolfier's balloon was inefficient, cheap, slapped together in a matter of months

I agree the balloons were cheap in the sense that they were made by a couple hobbyists. It's not obvious to me how many people at the time had the resources to make one, though.

As for why nobody did it earlier, I suspect that textile prices were a big part of it. Without doing a very deep search, I did find a not-obviously-unreliable page with prices of things in Medieval Europe, and it looks like enough silk to make a balloon would have been very expensive. A sphere with a volume of 1060 m^3 the volume of their first manned flight) has a surface area of ~600 yard^2. That page says a yard of silk in the 15th century was 10-12 shillings, so 600 yards would be ~6000s or 300 pounds. That same site lists "Cost of feeding a knight's or merchants household per year" as "£30-£60,  up to £100", so the silk would cost as much as feeding a household for 3-10 years.

This is, of course, very quick-and-dirty and maybe the silk on that list is very different from the silk used to make balloons (e.g. because it's used for fancy clothes).  And that's just the price at one place and time. But given my loose understanding of the status of silk and the lengths people went to to produce and transport it, I would not find it surprising if a balloon's worth of silk was prohibitively expensive until not long before the Montgolfiers came along.

I also wonder if there's a scaling thing going on. The materials that make sense for smaller, proof-of-concept experiments is not the same as what makes sense for a balloon capable of lifting humans. So maybe people had been building smaller stuff with expensive/fragile things like silk and paper for a while, without realizing they could use heavier materials for a larger balloon.

That said, hot air balloons did have some practical applications:

• Military Ballooning—Hot air balloons can be used for reconnaissance
• Cartography—By providing an aerial view, balloons are useful for more accurate mapmaking
• Weather Observation—Balloons can be used to gain knowledge about parts of the atmosphere inaccessible from the ground

Tenses my rationalfic worldbuilder brain. Outputs: so I wonder if we'd have better international transparency cultures (faster surrenders/treaties, and fewer arms-races, and so a much greater chance of solving the alignment problem) as a result of the legacy of a long history of military ballooning for reconnaissance.

If a partially reusable and affordable rocket like the Falcon 9 was feasible in the 90s, then the answer is surely yes.

A similar rocket wouldn't have been feasible in the 90s as a rocket computer system of equivalent performance would have weighed too much to permit much, if any, cargo capacity.

Nor have I seen any industry experts claim such a thing would have been possible in the 90s.

When writing about this, I think it would make sense to suggest what you consider the pieces that are necessary for hot air balloons. That would make it much easier to clearly agree and disagree.

One question that occurs to me is what the... engine, I guess... looked like.

Like, I'm imagining that the engine and passengers are in a wicker basket. You probably don't want to just light a fire in the middle of one of those. In a modern balloon I'd probably expect a gas burner, but if you don't have one of those?

I wonder if you have something like a cast-iron stove, possibly with bricks to insulate the bottom of it and stop the basket from burning. That sounds pretty heavy. Maybe there was a limiting factor here?

Wikipedia doesn't say what the original used, but two other things caught my eye. In the section above, premodern and unmanned balloons:

The notable balloonist Julian Nott, in the 1970s; hypothesized that two millennia ago, the Nazca Lines geoglyphs' creation could have been guided by Nazca leaders in a balloon, possibly the earliest hot air balloon flights in human history.[7] In 1975 to support this theory, he designed and piloted the Nazca Prehistoric Balloon, claiming to have used only methods and materials available to the Pre-Inca Peruvians 1,000 years ago.[8][9]

I'm skeptical on general principles here, but there could be something interesting to learn. And in the section below, modern balloons:

Modern hot air balloons, with an onboard heat source, were developed by Ed Yost, beginning during the 1950s

Where did early balloons have their heat source, if not onboard? Unless that word means something different than "the fuel and the thing burning the fuel both being carried in the basket"? My guess would be there was a transition at this point that had something to do with the heat source, but was not what I would describe as "not-onboard to onboard".

I enjoyed this investigation a lot; it's fascinating to think of the uses to which this could have been put.

You may be interested in a related (ongoing) project I've been working on, to survey ‘paths untaken’--cases of historical technological delay, restraint, or post-development abandonment, and to try and assess their rationales or contributing factors. So far, it includes about 160 candidate cases. Many of these need much further analysis and investigation, but you can find the preliminary longlist of cases at https://airtable.com/shrVHVYqGnmAyEGsz/tbl7LczhShIesRi0j  , and an initial writeup and pitch of the project at: https://forum.effectivealtruism.org/posts/pJuS5iGbazDDzXwJN/the-history-epistemology-and-strategy-of-technological [EA · GW]   -- I'd be interested to hear any thoughts or comments.

Military Ballooning—Hot air balloons can be used for reconnaissance

Military use them the most obvious. 

Cartography—By providing an aerial view, balloons are useful for more accurate mapmaking

Maps are valuable but the amount of capital invested in map-making was relatively small. The people making the maps likely didn't have the capital to try to build hot air balloons. 

Weather Observation—Balloons can be used to gain knowledge about parts of the atmosphere inaccessible from the ground

I think there's a good chance that people didn't know that there was any worthwhile weather observation to be done by gaining knowledge about the upper parts of the atmosphere.

Prestige—The invention of the hot air balloon had tremendous psychological repercussions across the world. In an earlier time with slower technological diffusion, the first state to develop the hot air balloon could use it to boost prestige for decades or longer.

This is essentially what the Montgolfiers targeted. They pitched their prototype to the king instead of just building the ballon in their hometown where their paper mills are located. Out of that, they got a noble title for their father. 

I think it's very counter-intuitive that you can actually steer a hot air balloon well because the wind direction is different at different heights. You need that steering ability for military applications. 

The sky lantern was invented by the Chinese by at least the 3^rd century AD. Constructed from paper and a small fuel source, sky lanterns operated using the same principles as manned hot air balloons, well over a thousand years prior to the invention of the latter.

A sky lantern can get away with a lot more errors. If it breaks that's okay. When a hot air balloon breaks someone dies.

I sometimes wonder if asking why should something have been invented earlier is not also an important question to ask in these types of inquiries.

Arguably the hot air balloon perhaps should have been invented shortly after Archimedes' "Eureka" moment. But why would such an application of the principle of buoyancy have been applied to floating in the air at that time? One idea might be that it should have been invented then IF the idea that air (gases) were basically just like water (fluids). But there would also have to be some expected net gain from the effort to make doing the work worthwhile. Is there any reason to think the expect value gained from the invention and availability of the balloon was seen as anything more than a trivial novelty or toy (such as the Chinese seemed to think)?

After all, a balloon is not much like a ship which can be steered and the value of higher ground limited to just how far one can see clearly, and with sufficient detail.

The Archimedes example might be an easy case, but I'm wondering if there are not things to look into regarding the motivations for the work on an invention at the time that offer some type of change in the "environment" (social or intellectual/level of knowledge) that point to why no one did something we now think of as obvious.

For all things invention, intellectual property rights are an important thing to take into consideration. The fact you could create things and patent then and then profit, meant that many people started to be creative. And I guess it can be argued that it impacted the Zeitgeist so much that even in a neighbor state that was still facing an absolutist regime, the impact was felt, even with less property rights.

I don't think you could invent the air balloon, enter the Senate and wait for a patent nor any kind of glory. If my peers are joining the Roman Army, I'd rather joining too than pursuing a career in engineering.