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.
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.
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?
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.
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.
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…”
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.
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.
Right. And myself and others have explained why that is harder than it seems. But you’re not persuaded.
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.
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.
So, if none of this reasoning persuades you, and you think it would be so easy, … do it. Build a hot-air balloon using only the technology of pre-1783: no rubberized fabric, no nylon ropes, no propane fuel, no machined metal burner, etc.
We don’t even insist on an actual demonstration flight. Just an accurate construction plan, with specific measurements & amounts of materials involved. If you can come up with one that the people here can’t refute, you will have persuaded them.
Again, not a convincing argument. An aeronautical balloon has around 1500 to 2000 square meters of material. High quality silk costs around eighty dollars a yard. So let’s say a silk balloon would cost around $150,000.
That’s more than I would spend on this project. But that’s not a sum beyond the reach of mortal man.
It is, however, a sum beyond what almost any rational man would invest in a theoretical idea of flight that looks conspicuously hazardous and by no means guaranteed to succeed.
The ludicrous part is the attempt to estimate pre-industrial costs by using modern prices, which are a very recent miracle of computer-optimized supply-chain management.* And that’s not to mention the actual supply-chain challenges the estimate would pose in pre-industrial society.
And this is after post #47, in which MD2000 prophylactically addressed the entire reason why that’s invalid. (I’ve gotta say: the scope of that post was sweeping, but it was so succinct. That was outstanding!)
There’s an entire engineering discipline devoted to it: operations research. Despite the name, it’s not a business-school thing. It’s among the mathiest of the applied maths.
And all of this is after I pointed out that the Chinese, who 2000 years ago had both silk and paper in spades, made their balloons out of paper. Even if that were a coincidence at first, they’d have switched to silk if it were a better material—the benefits would have been obvious for certain applications.
) 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.