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Old 11-16-2018, 07:35 AM   #31
David Johansen
 
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Originally Posted by Phil Masters View Post
The problem with trial and error in early aircraft development is dead test pilots. Who are, at low TLs, frequently the people whose bright idea this was.

It was bad enough at TL6. At TL4? Lots of dead monks and mandarins. Not many aircraft.
Which is why we used trained monkeys. Well that was the theory anyhow. Does anyone have ideas how to deal with monkeys with jet packs flying around the city stealing things?
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Old 11-16-2018, 07:46 AM   #32
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Default Re: Are TL4 'Rocket-Pack's Possible?

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The Aborignal Boomerang is an airfoil that was developed at TL 0, and Fantasy-Tech 1 has real world development beginning at TL 3
As Dan says, the boomerang is one of those outlier technologies. Like the development of stone tools, there's a large large swath of time for humans to tinker with it - TL 0 is an immense slice of human history, and the Aborigines have been in Australia for 40 thousand years. The boomerang is also one of those tools that benefits visibly from small improvements, without the problem of killing the tool-maker.

Boomerangs include things more properly called wooden war picks with no special flight characteristics, things that are basically big heavy throwing clubs that are well balanced and crudely aerodynamic, small throwing clubs that do have airfoils, and the returning boomerang, which is used to circle around behind prey and flush it towards the hunter (which has really good airfoils). Basically, a series of snapshots in the development of the seriously-impressive returning boomerang, frozen in time because each stage was a perfectly good tool in its niche. But the periods of time are much much longer than a human lifetime.
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Old 11-16-2018, 08:02 AM   #33
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Coming up with an aerofoil via trial and errors is not actually impossible, evolution managed it a few times, but the amount required is very large (even if you start at TL 4, it probably won't still be TL 4 when you finish).
Lets not go too overboard here. Kites and sails are after all both stick and fabric airfoils developed before TL4, and even a badly designed "glider" with enough fabric might be a functional parachute.

Certainly developing one without aerodynamics is a risk I wouldn't volunteer for, but it's probably not impossible for even a first attempt at a hang glider to work well enough to be survivable.
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Old 11-16-2018, 08:02 AM   #34
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Personally I figure that someone with access to bamboo and a lot of silk might be able to make a working glider, those materials are noticeably lighter the wood and cloth that they would normally have been made out of.
Someone with silk and bamboo did; kites that lift humans are described in China some centuries back. The landings were a killer though, to the point where the described use is as a means of execution.
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Old 11-16-2018, 08:14 AM   #35
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Default Re: Are TL4 'Rocket-Pack's Possible?

Every time I've ever flown a kite, it finishes its run by nosediving into the earth. One way trip to broken-neck town, I would imagine.
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Old 11-16-2018, 08:37 AM   #36
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Certainly developing one without aerodynamics is a risk I wouldn't volunteer for, but it's probably not impossible for even a first attempt at a hang glider to work well enough to be survivable.
I caught a TV documentary about an attempt to test whether Leonardo’s glider design could have worked. The team of modern aeronautical engineers came up with something that didn’t look much like Leonardo’s sketch but looked a lot like a modern hang glider, but made of TL4 materials. They gave it to a competitive champion hang glider pilot, and she took it up and flew for a short distance with a couple of guys holding ropes attached to the wings to keep it stable.

The team decided to declare success at that point, and stop. Frankly, it all looked pretty hairy. The vehicle in Steampunk Conveyances was inspired by that, but kind of optimistically. I think a bunch of Renaissance tinkerers would actually just have killed a couple of people and then gone back to composing poetry.
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Old 11-16-2018, 08:42 AM   #37
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Which is why we used trained monkeys. Well that was the theory anyhow. Does anyone have ideas how to deal with monkeys with jet packs flying around the city stealing things?
I am reminded of the story of the American space engineers who put a live bear in a test capsule flight — after which, the bear refused very assertively ever to go anywhere near anything that looked like the capsule, ever again.

One of the engineers observed that they had just proved that that bear was smarter than any of their test pilots.
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Old 11-16-2018, 08:44 AM   #38
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Default Re: Are TL4 'Rocket-Pack's Possible?

What's the gravity like on your home-moon?

Perhaps you could insert some naturally occuring rocket-friendly fuels to help the tech get started, or some conveniently flight-capable fauna to mimic.

Another possibility- the 3 moons share similar ecosystems, and there's a migratory space-bird that moves between them with the seasons. Studying how they do so gives an impetus to the TL4 spaceflight tech.
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Old 11-16-2018, 09:35 AM   #39
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Anyhow, I think you'd have a gunpowder reservoir with a valve resembling a baker's sifter. The rate at which the sifter is cranked would increase or reduce the volume of powder dropping into the firing chamber. As one would expect there would be a chamber between the fuel and firing chamber that can be sealed from both ends to prevent back blasts. You'd get a stuttering and jerky ride of course.
Things much like that have actually been tried, and they have an unmitigated record of failure. Explosive failure. Eventually, a spark gets back into the powder tank, and boom. It's much harder to get valves to seal well with solids than with liquids or gases.

That being said, that's an awful lot like how a pulse jet works. If you want potentially low-tech powered flight, a valveless pulse jet is about as simple as they come. And you can run one on almost any combustible fluid (with varying efficiencies, of course). One is forced to wonder how well various alcohols would work? I know that a lot of hobby designs run on diesel, so I wonder if vegetable oil would work? (Given the well-known trivia that the first diesel engines ran on peanut oil.)

Anyway, there are all sorts of YouTube videos about them.

One problem- they do need something like a spark plug.

Another problem- how exactly would a TL4 designer have thought to make the damned thing?

Last edited by acrosome; 11-16-2018 at 09:57 AM.
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Old 11-16-2018, 10:53 AM   #40
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Default Re: Are TL4 'Rocket-Pack's Possible?

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Esoteric Chinese know-wotz would also work
For example, this.
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