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Author Topic: Modular Airships  (Read 6904 times)
19th Century Space Pilot
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« on: August 17, 2009, 01:35:27 pm »

I posted about constructing my own Personal LTA Flying Machine a while back, and someone mentioned cluster ballooning as being a lot cheaper. That has got me thinking: why not combine the two, making lift modules which can be joined together to produce the lifting envelope? So your Airship would be sort of like a cluster balloon, except cheaper and steerable. Such common modules could also be configured for lifting a small house, for example. Basically, it's OTRAG for Airships. If one module pops, you'll descend to the gound slowly, instead of crashing.

If the modules are cylinders 4m long and 1m diameter, and filled with Hydrogen, they should have a lift (accounting for the weight of the material) of 12.5kg each, if the material weighs 100g/m^3 (achievable with plastics).

Thoughts? If they can be mass produced, Airships for everyone.

Now, I'll go post this on Halfbakery as well Smiley
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19th Century Space Pilot
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« Reply #1 on: August 17, 2009, 05:49:59 pm »

I made a mistake working out the surface area of such a cylinder. The actual lift, if filled with Hydrogen and with a material weight of 100g/m^3, would be around 11kg. Still, 10 of thyese would equal 110kg, sufficient for a manned craft.
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Noctum Solaris
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« Reply #2 on: August 17, 2009, 06:10:22 pm »

I was under the impression that it was illegal to use hydrogen for such applications, is that not correct?

By the way, I'd like to learn how to do these kinds of calculations, if anyone could point me in the right direction.  Although, with helium.
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akumabito
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« Reply #3 on: August 17, 2009, 06:43:50 pm »

I do believe hydrogen is a no-no.. using helium, I believe there is a 12% reduction in lift capacity.. helium is also a fair bit more expensive than hydrogen, unfortunately..
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Atterton
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« Reply #4 on: August 17, 2009, 06:45:54 pm »

I think airships have generally always used smaller balloons within the envelope, for safety reasons.
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« Reply #5 on: August 17, 2009, 07:39:46 pm »

I think airships have generally always used smaller balloons within the envelope, for safety reasons.

Indeed so, however they were not clusters of much smaller balloons but rather large hydrogen or helium filled cells of hundreds of cubic metres of gas.  The exception to this however is the blimp, in which the envelope is the outer cover.       
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19th Century Space Pilot
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« Reply #6 on: August 17, 2009, 07:56:59 pm »

I believe you are refering to Zeppellins, which can be described rather accurately as 'extreme cluster balloning with a rigid framework and outer skin to give it shape and maneuverability'. In the case of the airship I mentioned, it would be a semi-rigid, which is basically a blimp with a keel running underneath it to improve maneuverability and shape. So it would be sort of a cross between a semi-rigid and a cluster balloon, with the formers advantages in maneuverability.

Hydrogen isn't illegal, as far as I can tell. A good thing too, given it's advantages over Helium.

Quote
By the way, I'd like to learn how to do these kinds of calculations, if anyone could point me in the right direction.  Although, with helium.
The lifting capability per a given unit of volume is the density of air minus the density of the lifting gas, multiplied by the volume. For example, air has a volume of 1.25kg/m^3, whereas Hydrogen has only 0.09kg/c^m, so the lifting capability per cubic meter is (1.25-0.09)=1.16kg/m^3 lift capability. Helium is two times as heavy as Hydrogen, so it's density is 0.18kg/m^3. Then multiply the lift capability of your chosen gas by the volume of your airships envelope, and you have the maximum weight of your airship.
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Atterton
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« Reply #7 on: August 17, 2009, 08:03:38 pm »

Zeppelin is just a brand name. What exactly is it you feel would give your design an advantage over the normal airship design?
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19th Century Space Pilot
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« Reply #8 on: August 17, 2009, 11:20:15 pm »

The modules can be mass produced, allowing anyone to make their own flying machine from them in whatever combination they like. Like I said, OTRAG style. It allows airships to be reconfigured for whatever purpose you like.

By Zeppelin I was refering to Dirigibles, BTW.
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Atterton
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« Reply #9 on: August 17, 2009, 11:26:56 pm »

Fair enough, I still can´t pronounce dirigible.
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VRAndy
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« Reply #10 on: August 18, 2009, 12:17:19 am »

I'm trying to imagine the best way to connect the balloons so that they lift the lawn chair gondola, but at the same time don't just crowd each other out like a normal cluster balloon.

Perhaps you could have a rigid "frame" consisting of a single aluminum shaft down the center?  (You could even have secondary, but slack, cables so that if the shaft collapses it goes back into "cluster" formation)

I'm sure that would do nasty things to your weight allocation, of course, but you can always just add more balloons.

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19th Century Space Pilot
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« Reply #11 on: August 18, 2009, 01:26:38 pm »

I was actually envisioning ach module being almost a semi-rigid on it's own, with a keel running along the bottom, which connect together to connect the modules. So if you connected them all in a line and put your gondala underneath, you'd have a very long and skinny semi-rigid. However, that's not the best configuration, since you'd be able to connect four in a parallellogram instead, using a special endcap.
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Noctum Solaris
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« Reply #12 on: August 18, 2009, 04:49:48 pm »

Thanks for the calculation info.

As for structure, ideally speaking, how about carbon fibre?  It could be used to create a modular frame supporting the balloons and creating shape.  Skin optional, perhaps.
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Atterton
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« Reply #13 on: August 18, 2009, 06:20:45 pm »

How about a net?
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19th Century Space Pilot
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« Reply #14 on: August 18, 2009, 10:13:01 pm »

To contain the modules in a classic Dirigible architecture? Nah, I want something that is a simple clip-together system, to make it easy to assemble a craft (at least the lifting part). If you mean attached to the keel, however, to spread the load across the entire module - sure, why not?
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Atterton
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« Reply #15 on: August 18, 2009, 10:39:25 pm »

You would still want your pieces to be aerodynamic after assembly. Perhaps the best way would be to imagine the typical airship shape, kind of cigar like. Cut off either end, to be used as end points. Then the main body cut into several thick cylinders. You could then place as many of those cylinders together as you wanted, and add the pointy end parts afterwards. Rather like a train with a locomotive at either end. Of course the engines and habitation part would probably then need to be placed outside the envelope, which might be bad for aerodynamics.
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19th Century Space Pilot
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« Reply #16 on: August 18, 2009, 11:53:37 pm »

Only if you want a classical Airship shape, if you want to configure it into an Airship at all. Besides, it doesn't have to be a long thin cigar shape. It could be two, with the gondola attached at the middle, like most twin ballooned Airships.

One idea I have in mind is a configuration that has two modules connected in a line, connected in parallell to another two modules in a line, so that one module is beneath another, then use two of these in a typical twin balloon system.
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Dr. makebot
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« Reply #17 on: August 19, 2009, 01:26:32 pm »

what about putting the two next to each other and having a gondiler under each.
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akumabito
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« Reply #18 on: August 19, 2009, 01:49:52 pm »

Not modular at all, but very much on the topic of alternative hull shapes for airships... I once made a quick sketch of an airship 'racer', the design of which was roughly based on a Zodiac inflatable boat. Imagine such a boat, if you will, with the air chambers filled with helium or hydrogen. the normal seating arrangement would remain the same.. this should be fairly aerodynamic as well as stable. It would also provide a rather large interior space, although for a similar size, lift capacity isn't as great as a conventional shape..

Spoiler (click to show/hide)

It's a little hard to see, but there is another gas bag running the length of the ship, right down the middle, which has the same diameter as the outer gas bags. I once ran the numbers for a configuration like this, and the max payload would be about 500kgs, which really isn't a whole lot.. but then, this was designed to be a racer, blockade runner, or similar craftm where speed and maneuvrebility are more importan than carrying loads of stuff..
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Atterton
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« Reply #19 on: August 19, 2009, 06:28:26 pm »

The reason why classical airship shape would be a good idea, is because it is very aerodynamic.
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popuptoaster
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« Reply #20 on: August 19, 2009, 10:38:29 pm »

Surely all your doing though is adding expense, weight and failiure points with all these joints for no real advantage? Whos going to want to adjust the size of their airship once they own it? and if your an airship manufacturer i would assume your gas cells are already pretty standardised and you just line up as many as you need to fill the airframe length the customer has specified.

Dont forget you need places to mount engines, conections for controls and fuel, and the fuel tanks have to be in a position to keep the carft stable as do the ballast tanks so its not as simple as just adding modules unless each module has everything built in and that would make them very expensive.
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19th Century Space Pilot
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« Reply #21 on: August 19, 2009, 11:50:51 pm »

I can't afford to get an Airship custom built for me. I could, however, afford to buy several modules and attach them together.

Quote
Dont forget you need places to mount engines, conections for controls and fuel, and the fuel tanks have to be in a position to keep the carft stable as do the ballast tanks so its not as simple as just adding modules unless each module has everything built in and that would make them very expensive.
The Zeppellins never had all that stuff mounted to each individual gas bag... you build that into the gondola. The gas bags are merely there to provide lift. The aim is to keep each module very simple, i.e. a gas cell and a keel. Everything is mounted on the gondala, including the modules.
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popuptoaster
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« Reply #22 on: August 20, 2009, 12:29:28 am »

I can't afford to get an Airship custom built for me. I could, however, afford to buy several modules and attach them together.

Quote
Dont forget you need places to mount engines, conections for controls and fuel, and the fuel tanks have to be in a position to keep the carft stable as do the ballast tanks so its not as simple as just adding modules unless each module has everything built in and that would make them very expensive.

The Zeppellins never had all that stuff mounted to each individual gas bag... you build that into the gondola. The gas bags are merely there to provide lift. The aim is to keep each module very simple, i.e. a gas cell and a keel. Everything is mounted on the gondala, including the modules.


not true, fuel, ballast and engines are mounted on or in the frame of the airship.



besides if you need to lift a gondola, you need a certain amount of lift to carry it and its payload so you'd have a minimum amount of modules needed, and then why would you want to add more lift modules to it afterwards?

The joints between modules are going to have to be pretty substantial to transfer the lift from the end ones to the centre where the weight is being carried or the thing will just bend up at the ends like a banana, it just sounds like its way more complex than you'd ever need
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19th Century Space Pilot
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« Reply #23 on: August 20, 2009, 02:09:13 pm »

You can enlarge your airships as you go on.

Just because the fuel, ballast, and engines are mounted on the frame of a rigid, doesn't mean they have to be. Where do they mount them on a semi-rigid or Blimp?
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Noctum Solaris
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« Reply #24 on: August 20, 2009, 02:12:09 pm »

So what this leaves me imagining is a (very light) keel, with seats/whatever + engines attached beneath and to the sides respectively.  Balloons cluster-tethered atop it.

Maybe.
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