Renaissance flying machines?

What about some sort of hand cranked propellor for dirigibles?

I'm surprised no one has referenced the White Dwarf human-powered airship yet! See also

White Dwarf
and Pedal–Powered
Flight
BRYAN L. ALLEN


Note that's a PDF. But it's by...well I'll let the intro blurb to this article do the talking...

Bryan L. Allen first learned to fly in 1974 In a foot–launched
hang glider. He was the pilot of the Gossamer Condor pedal–
powered airplane that won the £50,000 Kremer Prize in 1977.
The Condor is now on permanent display at the National Air
and Space Museum in Washington, DC. In 1979, he piloted the
Gossamer Albatross across the English Channel to win the
Kremer Cross–Channel Prize of œ100,000 for the group
headed by Dr. Paul MacCready. in 1984, ha set a speed record
at 23.5 mph when piloting the MacCready Bionic Bat, winning
the fourth installment of the Kremer World speed contest for
stored–energy human–powered aircraft. He still holds two
Federal Aeronautique international world records: distance
and duration for Class BA–1 through BA–l0 (nonrigid gas
airships). All told, he has piloted eight different human powered
aircraft. Bryan is employed full time by Telos Corporation, a
software services company, at the Jet Propulsion laboratory In
Pasadena, California. He possesses private pilot ratings for
airplane single–engine land and gliders and Is looking
forward to some day having an airship rating.

So it's hard to imagine who would be more qualified to participate in this discussion in general, for either HTA or LTA!

{edit}--of course the White Dwarf, and any sensible human-powered design, is not arm-cranked but leg-pedaled.{/edit}

Now some strong caveats--despite its steampunk look, White Dwarf is very much late 20th century technology. (Reed Gleason, who later acquired it, added a "weedwhacker" with a propeller on the tip to boost its propulsion, because human pedaling is both tiring and risky once one gets exhausted, so it didn't stay strictly human powered at that!) The "fabric" is a plastic sheeting material developed for utility tethered balloons, far advanced over anything possible in the 19th century. The gondola frame is made of modern metals, the prop and fin are styrofoam.

Trying to match the strength-weight ratios of these materials with what's available pre-1900 would be impossible. Maybe bamboo could get you a comparable gondola weight?

Note the speed ranges in Allen's article--a really hard pedaling effort can get it up to maybe 12 mph. (And the aerodynamic instability of the hull overcomes pendulum stability around 15 mph, something the designer did not worry about given the superhuman strength required to approach such an airspeed). Allen figures a sustainable "cruise" speed of about 7-8 mph.

The trouble with very slow airships is, one has to have enough speed to assert some navigational authority despite contrary winds. Airships capable of 40-50 knots often find themselves stuck; even the big Naval rigid airships Akron and Macon with their 70 knot airspeed capability found themselves trapped from time to time. At 7 knots, one has a moderately directable free balloon.

Can a pre-19th century gasbag, made of varnished silk most likely, or rubberized silk perhaps, come close to the lightness of the White Dwarf's skin? How about its gas-retaining properties? It sort of helps that helium would be unavailable, so perforce they'd use hydrogen. Or other mixes common in OTL early LTA experimentation, like "town gas" which is a mix of hydrogen and carbon monoxide :)eek:) generated by blasting carbon (ie coal) with live steam; the steam reformulates into hydrogen and CO. Monoxide is slightly lighter than air, so the mix has about half the lift of pure hydrogen--but it was readily available as this stuff was often used for gas lighting in the era. Half the lift, about the same fire hazard, and unlike hydrogen poisonous to boot--but available. Let's assume hydrogen since the lift is marginal enough even then!

Hydrogen is easier to retain than helium, but not by a whole lot--it's still a slippery, leaky gas.

I don't think anyone in a European setting paralleling our time line would divert themselves into trying for a human-powered dirigible; by the time they have the availability of hydrogen, suitable materials for the gas bag and frame, and some clue of aerodynamics for the design, they will have mechanical (including electrical--the more successful 19th century airships were often battery-powered) power plants that are ludicrously inadequate by the standards of the age of flight proper but still better than human power!

Before abandoning the line of thought completely though, one might reflect on what might happen if we scale the ship up from a one-person to a multi-person capability. If we were to double the linear dimensions, we'd get eight times the lift volume, whereas the drag area would only be multiplied by four, meaning if all eight people were to pedal together, we'd have twice the power per drag area available. This only works out something like a 20-25 percent speed increase, allowing cruise at perhaps 10 mph if everyone stays pedaling, alternatively the crew can alternate, with half of them pedaling and half resting, so the effort can be sustained perhaps indefinitely--assuming our lift budget includes a fair amount of food and water!

Even bigger scaling slowly increases the speed margin. Meanwhile, scaling up an airship at a given state of the art tends to involve heavier structures; the drag area proportion goes down (so less "engine" or in this case our pathetic human "engine" is more effective), the structural strength against aerodynamic bending requirement scales in proportion to volume and hence mass--but the structural aspect of achieving suspension of the weight of the craft rises. Also, as we achieve higher speeds, the bending stress on the hull increases as the square of the speed, leading either to risk of failure or increased hull weight. And there is the aforementioned dynamic instability at higher speeds, which was not a problem at 10 mph but would be at 15.

The idea of an air galley, propelled by hundreds of pedallers, seems quite romantic--I was thinking air Vikings. But even a ship that could lift half a thousand of them couldn't go much more than 20 knots, leaving them too much at the mercy of winds. And where, before 19th century type tech is available, is anyone going to get hydrogen? (With inferior lift gases, like say steam, or town gas, or methane, or ammonia, the performance is more marginal still, and there are risks and dangers that even hydrogen doesn't pose).

Hydrogen by the way, assuming someone figures out how to make it in quantity, is less risky for a human powered vehicle than for one powered by an engine that burns fuel, or by electric motors whose power lines might produce sparks. Until, that is, the humans driving it get hungry and want cooked food!:p

Perhaps horses can be harnessed somehow to drive a big bio-powered airship--I'm not sure hayburners are really much more efficient than human muscle, pound per pound. Actually DValdron in the Thule thread came up with some interesting figures that suggest that horses aren't such great draft animals, pound per pound, compared to dogs! But I don't see how one harnesses a lot of dogs to be propulsion units, and their food stock of meat would tend to spoil a lot faster than hay.

Meanwhile even if the horses or dogs actually propelling the ship don't need cooked food, the humans aboard would still want it. And there's the kaboom!
 
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You could store up horse energy on clockworks.

"Clockworks" resolves into two things--1) lots of fussy, delicate gears that may serve many useful purposes but in power terms are so much dead weight to be avoided and 2) springs.

Springs of course have sort of been addressed under the rubber band airplane category of dialogue.

If springs can be made light enough and capable of storing suitable amounts of power, well and good, but I don't see how they can. If they could, it doesn't matter what sort of power you use to wind them---horses, man power, water mills, windmills, it's all the same. But I don't think it's possible.

I have yet to find the energy/weight ratio of a bluesteel spring to be expressed, but the Clockwork Power page at the Museum of Retro Technology casts considerable doubt on the principle by pointing out a number of applications where compressed air was found to be a superior method of power storage, despite the fact that compressed air loses much of the energy pumped into it when it cools from its compressive high temperatures.

Well, maybe a spring-driven propeller (and, yes, it would be "clockwork" in that some sort of escapement regulator has to be applied to keep the torque steady) could serve as well or better than rockets. Unlike a rocket, which is pretty compact and quite light when burned out (and a solid fuel rocket that is spent is just a casing that would surely be simply discarded), we have the dead weight of the mechanism and the drag of the propeller to consider when the spring winds down and the plane goes into its gliding phase. So, aside from doubts I have about any sort of spring available to pre-1900 metallurgy being light enough to compete with even batteries or steam engines, these are extra problems I doubt could be easily solved.

Perhaps compressed air can be a superior answer here too as with torpedoes and trams? Making a good tank that can hold high pressure air while being reasonably light is a challenge. If it drives a propellor we still have the problem of what to do about the prop when the air pressure falls to zero. Perhaps some sort of ingenious Venturi principle thrust augmentor can use high pressure air to impel freestream air to higher speeds thus achieving thrust, and when the pressurized air is gone, easily faired off to minimize drag?

The prospects for that look dim, but we have historical evidence that those of a clockwork drive would be even dimmer.
The Museum of Retro Technology has pages on pneumatic powered planes, steam powered planes, and many other interesting and relevant things.

On the subject of rocket planes, aside from old-fashioned gunpowder rockets which have the quality control issues pointed out above by Detlef, we might consider the possibility of various liquid-fueled rockets being developed before 1900, and the possibility of enhancing their thrust by some sort of turbine or Venturi-principle thrust augmentor. Liquid oxygen based rocket engines are probably ASB pre-1900, so we'd be talking about other reactant combinations, so-called "storable propellants" that are liquid at room temperatures. These tend to be very toxic and caustic. Many combinations are hypergolic, meaning they react with each other on contact, which poses obvious hazards but also comes in handy in engine design--no need for ignition, just bring the components together! The sorts of rocket engines used during WWII--mainly by the Germans, but also by the Soviets in some experimental designs--for rocket airplanes used these sorts of fuels. (Von Braun and company at Peenemuende used LOX and alcohol for their V-2 engine).

Modern hypergolic engines, like those used in the Apollo Service Module main engine or the Titan II missile also used to launch the Gemini spacecraft, get ISPs over 300, meaning their exhaust is going at something like 3 km a second and they can hover 300 kg in Earth's field for every kg of propellent they can expel per second. (Or accelerate 30 kg at 10 g's). To get that, one needs a reaction chamber that can stand the heats and pressures involved, as well as carefully designing it for optimum capture of the potential thrust involved. It may be way beyond 19th century metallurgy to take those stresses without such a massive chamber the benefit is completely lost. But a low-speed airplane that is basically a light glider will not need a whole lot of thrust, so an engine much heavier than we'd expect of the modern state of the art might do the job at an acceptable weight, and low thrust means lower consumption of propellant so we might get thrust endurances that are reasonable, measured in tens of minutes instead of just minutes. If we can enhance thrust by using the high-speed exhaust to entrain and accelerate larger masses of air, we might improve on it a lot. Also they can be made throttleable and restartable.

Such an engine before 1800 would be completely ridiculous of course, indeed I'd guess the 1850s would be the earliest conceivable time. Also they'd have very poor notions of high-temperature high speed fluid dynamics, so the engine design would hit on reasonable efficiency only by accident or painstaking trial and error.
 

Dirk_Pitt

Banned
I think it's much more likely to see early exploration of hot air balloons, and maybe even some kind of airship sooner (yes, yes, I know airships are an AH cliche -- but theoretically you could power one with a steam engine in an alternate 1700s). Actual airplanes? Pretty much impossible without some kind of more modern power source, like a diesel engine...

I also agree that any sort of development along these lines is going to be done by individual artisans and in a sort of haphazard way.

Oh! Remember that medieval Chinese guy who tried to build a rocket flying machine? Maybe you could do something with that! A very primitive, one-use flying machine, but maybe you could combine it with renaissance parachutes to get clockpunk paratroopers.

Why do I have the image of Wilely Coyote on a rocket?
 
What about a dirigible with sails? Obviously not on the same general design as an ocean-going ship, as this would make it fairly top heavy, and liable to capsize, but with sails extending outwards, horizontally, in place of wings. I'm sure that some smaller manoeuvring sails could be attached vertically, so that it could land (or dock with docking towers), and take off like a normal (OTL) airship, and this could lead to airships as a widespread method of transport by the early 1800s, as, though limited by the winds in the same way that seaships were, they would be able to ascend and descend to find favourable winds, and would be able to travel much shorter distances, particularly on Europe to India or China runs, or trans-American routes.
 
What about a dirigible with sails? Obviously not on the same general design as an ocean-going ship, as this would make it fairly top heavy, and liable to capsize, but with sails extending outwards, horizontally, in place of wings. I'm sure that some smaller manoeuvring sails could be attached vertically, so that it could land (or dock with docking towers), and take off like a normal (OTL) airship, and this could lead to airships as a widespread method of transport by the early 1800s, as, though limited by the winds in the same way that seaships were, they would be able to ascend and descend to find favourable winds, and would be able to travel much shorter distances, particularly on Europe to India or China runs, or trans-American routes.

An unpowered airship would already be carried along at the same speed as the air moves, so there is no relative wind to act on any sails. They would just be dead weight.
 
Sorry, it seems more like a suicide unit.
We´re talking about the Renaissance here, right?
If you want a rocket that is reasonably reliable and flying (reasonably) straight you need two things:
- a propellant (gunpowder in this case) that´s reasonably consistent and evenly mixed
- an exhaust nozzle that´s reasonably "even" (circular or whatever)

If the exhaust nozzle is even a bit uneven, the rocket won´t fly straight. That´s still good enough if you want to hit an area. But it´s a real problem with one or several of them propelling a rocket glider.
And it´s the same with gunpowder. If the gunpowder isn´t evenly mixed then some parts (volume) of it will burn faster than others. Meaning the rocket won´t fly exactly straight. Still good enough to hit a general area.

Now imagine the size of the gun-powder rockets (plural!) needed to transport a fully armed soldier. And both of the problems I mentioned above just became larger with bigger rockets needed.
(In a sense that´s the difference between rockets certified to carry a satellite and rockets certified for manned space flight today.)
A few will just "fizzle", a few will explode on the ground. The majority might have "ignition and lift-off". :D

But then - because of poor gun-powder quality and exhausts - the rockets will start to pull in slightly different directions. Which means that most of the Renaissance rocket gliders (made out of wood) will simply self-destruct once in the air. Once the rocket(s) left on the glider decide to go in a slightly different direction than the rocket(s) right on the glider wing. :)
You´d be lucky if even 10% of the rocket gliders reach your target.
(I´m not even mentioning that rockets would expose Renaissance soldiers to accelerations - g-forces - unknown to them.)

It might provide entertainment for the besieged town or fortress though. :D
Some spectacular fireworks in the enemy camp. Some simply exploding, others not getting airborne but plowing through the enemy camp? Lots of enemy soldiers falling from the sky once their glider disintegrate. Maybe even some early aerobatics? Loopings or such? :D

I´m afraid the mercenary soldiers used in a lot of Renaissance wars might not volunteer for the job? They weren´t afraid of dying in a battle. But they might object to an 80-90% casualty rate just trying to use rocket gliders?

Rocket powered paratroops, not gliders.

And if even that doesn't work we can always think about Renaissance rocket artillery...:D
 
An unpowered airship would already be carried along at the same speed as the air moves, so there is no relative wind to act on any sails. They would just be dead weight.

Yes, and without the water a ship has to interact with, pretty much unsteerable too.
 
The idea of medieval balloon born parachute glider troops piqued my imagination. At first I saw a dozen gliders going over a castle wall, the invading warriors rushing to the gate from the inside to overwhelm the surprised defenders. Then I asked how could you even get that many in the air from a balloon? I’ve always liked airship carriers but I find an aerostat that large staggering. I don’t think you could make a balloon big enough to launch that many simultaneously using hot air. I suppose you could have multiple balloons with a few gliders each but costs are going to get prohibitive. What if the glider jumpers shimmied up the tether to the balloon and then glided over? Sounds great till they land and get slaughtered one at a time. What if the glider jumpers went in at night? I can’t imagine someone being able to put up a balloon without the watchmen noticing and someone getting alarmed. Even if you did I still imagine people crashing into stuff and not accomplishing anything worth the effort.
 
Interesting on the sense that crazy and retarded ufology is interesting? I just want to point that in alternate history, you have the word "history", and no place for aliens outside ASB.

Besides, these supposed Colombian ancient stone carvings have been proven to be hoaxes at least two decades ago. Hell, IIRC, even stubborn old Däniken admitted that they are not authentic out-of-place artefacts. So that's that.



I could see balloons and hang gliders appear a few centuries sooner, but that would be a best case scenario and would be stretching it. The gliders would need some knowledge of aerodynamics to back them up - they were attempted numerous times before the late 19th century, but no one ever got them right because they lacked the knowledge on how wings should be profiled to provide better lift. Hint: Having wings as flat as a board and with no other aerofoils (tailplanes, a rudder, etc.) is not how you achieve enough lift. Take a look at the more succesful gliders from the late 19th century - the ones used by Lilienthal, Pilcher, Chanute and others. Those are what you'd need, as well as what you could actually build with early modern European technology. Despite these being simple gliders, their inventors were capable of soaring in them above ground for many minutes, not unlike any of their more modern successors (the only difference being the construction material and the lack of adequate safety measures in the old ones). Fun fact : If it wasn't for Chanute, the Wright brothers might have never taken off.

Also, human-powered manned ornithopter gliders are physically impossible. Manned ornithopters prior to the current experimental ones are actually possible, but incredibly hard to pull off without an adequate motor/engine - which the Renaissance scholars won't have, since no such devices have been invented yet anywhere in the world.
 
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