Powering a clock(punk) airship

one enemy either betrays his faction and helps out your guys with the ships or he helps them out to get on their good side but is still working on the bad guys side.

Sorry I can't be of more help. I don't know much about mechanics.

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Unfortunately that wouldn't work. The enemy's method of flight just isn't available to non-magical humans - even with help.

Well, given your description of where they are with steam, I wouldn't consider that avenue for power. You could store a lot of mechanical energy with banks of wound springs but it would be awkward and heavy. Perhaps consider using the potential energy of weights to drive a mechanism, similar to grandfather clocks. Especially since the airship will be flying at altitude when it needs propeller power, you could have the weights on long ropes that are basically dropped overboard and periodically hauled up and "reset" by hand; this would actually have quite limited mechanical power but, depending on how much you want to handwave the physics... :)

Also keep in mind that an elongated envelope won't work efficiently with a hot air balloon. They are generally vertically-oriented because that keeps most of the air column above the heater. With a long envelope, the ends will get cool and lose lift. (Forced circulation? Multiple heaters?)

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You can sort of steer a hot air balloon if you're skilled enough. You change direction by going up, or down, until you hit a different air current. At different heights, air currents will be blowing in different directions. By rising or dropping into the right currents, you can steer your balloon horizontally. Generally, winds tend to veer to the right as you gain altitude. Usually you can change direction by ninety degrees or more in the first couple of thousand feet.

But I can see why you might want something more precise than relying on air currents, and which you don't need half a lifetime's experience to use properly.

If your working at high speeds you could use a rudder. It would have to be quite large, but it could be made from fabric, so it would be a bit like the sails they used for steering on ships. This would only work in high winds or at high speeds though.

It's a pity they haven't figured out steam properly yet, you could make a really nice simple system with just a circle of pipes and a reservoir of water above the flame for heating the air. I think it would possibly be simple enough for your world to have plausibly come up with on their own.

It would basically consist of a closed system of pipes, with a larger "box" for the reservoir of water. This would be positioned above the flame. The water would boil and build up pressure. When the propeller was needed, a catch could be released so that the pipe going straight up from the top of the reservoir would be opened. The smaller this pipe,the higher the pressure so the better the system. The high pressure steam would rise quickly, and so turn a small fan which would be simply attached to a propeller - so that turning the fan would spin the propeller. The hot steam would then condense and run back through the rest of the circuit of pipes back into the reservoir and hey presto! It would all happen again.

I don't know whether that's clear or not, it would be easier to explain with a diagram.

I appreciate it may be a bit sophisticated for your civilisation - but it builds on technology the Romans used for central heating, it's just got a fan and a propeller stuffed on.

I also have no idea whether it would actually work, but I had a lot of fun thinking it up :-D

Hmm, thing is I want to avoid handwaving the physics except where magic is involved and as I've said they can't use magic for this.

As to the elongated envelope I was just going on information on how airships were developed in the first place and the fact I got the impression that the envelope shape was as important as engines for control of an airship. I wonder how modern thermal airships (or indeed hotdog themed hotair balloons) resolve the issue - though two burners seems feasible. And of course it's entirely possible they know about lighter than air gas though finding a safe one would be difficult.

I guess they need their version of Leonardo Da Vinci, Hero of Alexandria or Archimedes working on the problem and soup up their steam power and then explain why they don't have the train yet.

All this is, of course, assuming that my instinct that a controllable wind powered airship like the one in that image is impossible. Even though mine would have a smaller balloon due to heating issues I'm sure you couldn't get large or sophisticated enough sails to allow tacking on an airship so you'd be back to drifting. Tell me if I'm wrong because if possible it'd solve the issue.

Becky

Beeblebum,

That system for spreading the heat is brilliant and much more elegant than two burners. And yes I think they'd work that out since they do have hypocaust systems for heating. I also think they might work out a better steam engine soon. They've got from a steam-powered organ (1120 according to Wikipedia) to a Newcombe type engine in about 300 years (as opposed to 600) and it took less than 60 years to get from Newcombe's engine to Watt's and a further 30 until Trevithick developed the first high pressure steam engine.

Becky

The easy answer for why they don't have trains yet... They need the airships more.

They need airships to defend against their enemies, so ground transport would be second priority.

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Yeah, they'll probably develop a steam based tank as well... *shudders* I bet that would be horrible to work in.

oooh, there was something I forgot to say - the propeller would be outside the basket so if the whole system was on a pivot, the propeller that was attached to the fan would allow steering in any direction.

You know, I thought of it only as a steering mechanism, but you're right it could also be used to spread the heat.

Oh, and one other thing, instead of having it permanently rugby ball shaped, how about you have it shaped pretty much like a conventional one, only with wires (strings if you don't have wires) attached to the outer fabric at certain intervals. That way mid-journey you could change the tension on the different wires and pull the balloon shape into a more aerodynamic shape for whatever direction you want to go in. It would speed up direction changes a lot, I think.

Is it very geeky how interested I've got in this? lol

You know for some reason I didn't register the propeller because I fixated on the heat spreading possibilities. But the fact it's simple, well within their comprehension and could solve three problems with one blow makes it a very elegant solution.

And nah not very geeky.

Very geeky is spending your whole bank holiday weekend world-building.

Becky

Haha but world building is Fun! Surely fun things can't be geeky.... Can they??

I have no idea whether it would actually work in practice, but still I'm a bit proud of the idea lol. Although if you forgot to let out the pressure every now and then it could explode... which probably wouldn't be good lol

Any society advanced enough to develop the hot air balloon is also far enough along to produce hydrogen, which was once known as "inflammable air." Coal heated in an enclosed vessel will give off this gas in abundance. In fact, it was only months after the the invention of the first hot air balloon that someone realized hydrogen made a far better lifting medium than does air.

Early hot air balloons heated the air before launch, by burning straw under the envelop. No fire was carried with the balloon, since heating the air requires a huge amount of fuel. No balloon could lift enough straw, wood, or coal to manage the job. As a result, the air inside the envelope quickly cooled, giving the balloon only limited distance and altitude.

After only a couple of flights in the highly-inefficient hot air balloons, aviators quickly turned to hydrogen, which provides by far the greatest lifting power of any gas. No one flew hot air ships again until recent years, when the propane burner was adapted for heating the envelop.

Powering an airship is another matter. Steam was actually used on one early airship, with some success--although the boiler, compact as it was, was too heavy to provide much power. And, of course, using any flame source around hydrogen is dangerous. (However, countless thousands of air miles have been flown in hydrogen airships using internal combustion engines.) A more successful apparatus employed batteries and an electric motor, although this, too, was limited.

In any event, you may not need football-shaped airships. Balloons are "steerable," after a fashion. Direction is controlled by ascending and descending to find favorable air currents. As the creator of your world, you can have a situation where the characters realize that air currents can be relied on to move in certain directions at certain altitudes.

One thing to remember: Military necessity brings rapid development. In World War I, airplanes went from being nothing more than kites with motors to serious weapons in just a matter of a couple years. Airships, barely invented by the turn of the century, were flying bombing missions of hundreds of miles by 1915.

Hmmm they certainly have access to both coal and wood syngases, but both are a mix of gases including a great deal of hydrogen rather than pure hydrogen. They could probably work out how to seperate the gases out however.

On the plus side their current tactic in the few skirmishes they've been in (it's clear the enemy is feeling them out for a major attack) is the launch of a fleet of tethered balloons above any city attacked to shoot at the enemy forces and Hydrogen balloons would be kept inflated and therefore be quicker to launch in an emergency. They are a bit dangerous however. Fire-based weapons might make them go *fwoosh*.

On the other hand they know how to make wood gas and they're aware of the fire piston (lovely the things you realise when you develop the whole supercontinent rather than just the bit where your people live - some of the races along their world's equivalent of the silk road use the fire piston as a firestarting method) so now I'm wondering if they might not jump straight over the more advanced steam engines to some sort of gas (gas as in gas not petrol) run internal combustion engine in the next few years. (And why am I talking about them like they really exist?). There's no reason the order of invention has to happen in the order we did is there?

As to steerability they need something a bit more immediate and controllable than adjusting height to find the right wind direction. *Muses on a possible wood gas run airship*

Becky

There is an order, or a general sequence, to the development of inventions, but as you just said, parts can be skipped over. It would be hard for the automobile to be invented without most of its components having been developed first. Just because Earth inventors moved in our linear direction doesn't mean that another world couldn't branch out and go another way. For instance, if General Motors and the oil and gas companies hadn't conspired to buy up the streetcar lines and convert to gasoline-powered buses, the United States might never have developed the Interstate Highway System, but could have high-speed bullet trains going everywhere.

The method of generating steam to turn a small propeller sounds pretty good to a non-engineering person with only high school physics taken 40 years ago. It wouldn't weigh much and would be fairly easy to develop and build. As I understand it, steam engines are extremely heavy, which would handicap even a hydrogen balloon.

I have ridden in hot air balloons. Most flights occur in the early morning hours, often launching just after sunrise, because the air is most still then. They are not as easy to steer as was suggested, and believe me, air currents rarely take you the way you want to go.

The sausage, or dirigible shape is most effective if the balloon is filled with hydrogen, which has the best lifting power but is flammable, or helium, which had 1/4th the lifting power but does not burn. The Zeppelins and later the Goodyear blimps are amazing flying machines. The Zeppelins used hydrogen, could carry heavy loads, but ended up being replaced with helium because of several (not only the Hindenburg) being destroyed by fires. The Goodyear blimps are helium.. They have never been developed for commercial purposes except for advertising. But they are excellent for air photography of activities like football games. They would be excellent for air surveillance of an enemy's ground troop movements. They could fly too high for them to be a target, considering the weapon technology of your world . They could be used to effectively drop bombs.

Your biggest problem now is how to obtain the helium. Germany used hydrogen because they did not have a source for helium. The United States had all the helium reserves.. The last Zeppelin ever built by Germany was constructed for the Untied States to use helium. (It was named the Los Angeles, was the first of many, and outlived all the other U. S. Airships, becoming the only one ever to be decommissioned and dismantled.)

So, you need to find out where helium is found, how it is recovered, processed , transported, and stored on Earth, and then adapt it all to your world. Maybe you'll get some helpers here on NaNoWriMo.

Good luck and happy writing!

Well people had already come up with the rough idea for an internal combustion engine by the 17th Century in our world. In fact Da Vinci described a compressionless internal combustion engine in 1506, he also described a steam engine but that's Da Vinci so I'm not shocked. Still the fact people were working on Internal Combustion Engines simultaneously means that it would just have taken one lucky break for it to work out different.

Infact according to this page Robert Street made a working compressionless engine in 1794 and Watt's steam engine was 1769 according to Wikipedia so they're pretty close together.

Helium tends to found in natural gas fields and I think the low-temperature gas liquefaction needed to extract it might be a bit beyond them at the moment. If they're going to use a lighter than air gas it'll probably have to be hydrogen. Then again - the Hindenburg not withstanding - it's probably not really all that much more dangerous than using Helium with proper precuations (like not flying in thunderstorms). The Akron and the Shenandoah were both Helium filled and the R101 would not have been saved from crashing by being filled with Helium though it would not have caught fire on impact if it had been.

Becky

Helium is extremely difficult to extract while hydrogen is very easy to obtain. Germany's hydrogen-filled zeppelins made pretty wicked weapons in World War I. The allies quickly found out that it took more than a few bullet holes to bring one down. They could stay aloft even when filled with bullet holes. The things had to be hit with incendiary bullets.

Just a side note: the last zeps built by Germany were the Hindenburg and the identical ship Graf Zeppelin II (which only underwent test flights).

Helium is naturally extractible from ground sources. While in the real world, helium was not identified and isolated escaping fron the ground until the early twentieth century, there's no reason in your story that the Human nation did not discover a natural source of hgelium and were able to identify the properties of this gas and capture it. Though you might want to call it something other than "Helium," though, just for versimilitude's sake.

Propelling the airship forward will be difficult, however, without gasoline-powered engines. Steam power, even with the improvements you describe, doesn't have the power-per-weight ratio of internal-combustion. However, there are examples of steam-powered cars, like the Stanley Steamer, so I suppose a steam-driven turboprop engine is not too much of a stretch. However, even the Stanley Steamer was poweredv by kerosene, so perhaps some form of combustible fuel other than wood or chunks of coal cound be used.

Here's an idea: If you're going with the Archimedes idea, why not use the Archimedian Heat Ray? Supposedly Archimedes invented a series of parabolic mirrors that could set a ship on fire at range, and used them to defend Syracuse from a Roman invasion. You could have such an apparatus on the airship, which could do two things: under normal conditions, it would help heat the water in the boilers to create steam for propulsion, and also it could be used to help defend the airship against airborne attackers.