Modular Airships

[kirinyaga]

and don't forget the control fins and those openings that can be seen on the last image are the attachment/drop points for cables. They're needed there and not anywhere else during takeoff & landing. You need stairs to go there, and to the engines.

I'm pretty sure the balloons cost is much less than half a zeppelin cost. And add to this a system of small balloons will cost more than a single one : more fabric because of the surface-to-volume ratio, thus more stitching, and more volume for the same lift (thus more gas, more wind loading, bigger motors, etc...) because of the dead weight (inter-module attachments, all this fabric, ...). If you think about it, even doing them may not be that cheaper : I mean, do you really want to automate a balloon manufacturing ? Chances are you still want someone to do & check the stitching. And that's what takes time (i.e. money). For the fabric cost, only the number of balloons and not the way they are built will make a difference.

Until a technological discovery will allow a stitchless process, I cannot see how you could avoid to pay hours of a qualified stitcher work. If I'd buy a balloon for me to be lifted more than a few feet above the ground, I for sure will request a minimum of two eyes and two hands per stitch.

[Hektor Plasm]

On a related note, the Zeppelin-esque gas as fuel concept is revisited in this rather tongue-in-cheek article from The Register...

http://www.theregister.co.uk/2009/08/19/sanswire_sts_111_announcement/

(Note this may slightly offend those of a delicate nature, those who have not yet experienced sex-ed, or clones) 

There are links to the company who are producing this unusual craft.

HP

[19th Century Space Pilot]

We don't need stitching to make the modules. They're plastic, after all. Since when did you see a plastic bag or rubber dingy that was stitched, rather than glued? You could stitch them, I suppose, but clothes are stitched, and the manufactuing price isn't that high (most of the cost is just profit for the company). Why would the stitcher need to be highly qualified in stitching? I'm not asking them to do any fancy patterns...

This idea is not like taditional cluster ballooning. It is not like a rigid airship, either. The closest LTA machines in existence today to the idea are semi-rigid airships.

Each module would be a cylinder 4m long and 1m diameter, with a keel running underneath it. These keels would connect to each other to form the lifting component of the Airship. A gondola, containing the ballast, engines, and everything else needed, would be connected to the lifting part.

I do't know how much the fabric costs. If it costs £1/m^3, that's about £30 in fabric costs, but that number is ikely very wrong, since I just came up with it. The actual fabric cost might be closer to £0.10/m^3...

[Atterton]

The stitching on clothes doesn´t need to be airtight, which is one reason it doesn´t cost much. You would also have to deal with seepage through the fabric itself, helium atoms are small.
I think the keels you want for joining them together will add a whole lot of weight. I´d just put a net around the lot of them. However it also sounds like the whole arrangement will be very unaerodynamical.

[kirinyaga]

We don't need stitching to make the modules. They're plastic, after all. Since when did you see a plastic bag or rubber dingy that was stitched, rather than glued? You could stitch them, I suppose, but clothes are stitched, and the manufacturing price isn't that high (most of the cost is just profit for the company). Why would the stitcher need to be highly qualified in stitching? I'm not asking them to do any fancy patterns...

Your life is not suspended to your clothes stitches.
There is also a reason why the current airships are using stitched fabric and not glued/welded plastic. Stitched fabric is today the best cost/safety ratio (I'm not even sure if there is any advanced unwoven plastic that can be used).

In a general way you want a modular system to drive prices down. Where does the cost come from for an airship today ?

• The design. For an airship, what is expensive is the whole ship design. Modularity will just report this cost on the modules buyer. I guess modularity may drive it lower, but you have to admit it may also drive it higher.
• The materials. But a modular system will need more of them. And since the surface is divided by 4 when the volume is divided by 8, you'll need to build 8 "modules" TWICE the fabric you'll need to build one balloon with the same lift ... This is WITHOUT considering the weight of this additional fabric & the attachment system. So if you don't discover a cheaper material that can only be used for the modules and not for a standard airship, modularity will cost more.
• The building process. Modularity will help on this only if that process can be heavily automated. Again you will need a technology breakthrough. For example, to my knowledge at least, parachutes makers stitch them by hand, check then double-check and triple-check them, they don't use robots & welded plastic. And there are a lot of standardized parachutes built.

Modularity will drive costs down only if applied to a technological advance.

[edit:]
The hindenburg had 16 cells of 12 500 m³ in average. Your module is about 3.1 m³. To replicate one of the hindenburg cell you'll need 4000 modules and thus SIXTEEN times more fabric. That's about ten tons (200g/m² for helium airships seems about right) for your system versus 700kg for the hindenburg. Now, you don't need the same tensile strength for small modules, but you still need the fabric to be as leak proof as you can (unlike those helium balloons rolling on the floor the day after you bought them at the fair), plus the attachment system and one valve + one tube per module to empty/refill it, so I don't think you can save a lot on the weight.
And remember while the hindenburg cell lifts 12.5 tons, the 4000 modules will lift only 2.4 tons because of all that fabric. So you really need 20.000 of them. That's 80 times more fabric to buy and sew and five times more helium to buy and refill. And let's forget about the additional engines and fuel you'll need to move that increased volume against the wind.

Of course, I guess you don't want to build the Hindenburg. But it gives you an idea of the modularity limits.

[19th Century Space Pilot]

I only want to build a small Airship from them!

The original idea I hadwas based on a twin envelope airship, much like a Catmaran, where the envelopes were reconfigurable into the lifting structure of, for example, a flying base.

Surely seepage is less of a problem if your lifting gas doesn't cost as much? Modern airships can't vent because they use Helium, and it would be effectively releasing sevel 500 dollar bills to the wind every time you vent. If you can use Hydrogen...

Your module is about 3.1 m3

Eh? I was proposing them being 4m long and 1m diameter - 12.5m^3, actually. That's about 3x the lift.

[19th Century Space Pilot]

Hmmm... if I double the proportions, to 8m long and 4m diameter, and budget 200g/m^2, it increases the avialable lift (assuming Hydrogen) to a tad over 67kg. Put two of these together, and you have something that can serve as the lift for a personal flying machine. On it's own, it could serve as the lifting component of a small Airship, if the pilot is light. Put four of these together, and you easily have the mass budget for a two person craft.

Seepage is a problem, but have you noticed how metallic Mylar balloons retain their Helium for far longer than ordinary Latex ones? It's because of the metallized layer, preventing the Helium from escaping.

[19th Century Space Pilot]

Oops, made another mistake. Actual lift would be 91kg, even better. That's 1 module for a personal Airship, and two for a two seater. So four modules if you want to take the family...

[akumabito]

..assuming hydrogen, which could very well blow up if there's any oxygen in the balloon.
..or could get you arrested as using hydrogen as a lifting gas is illegal for manned air travel in most places.

Just saying

Sure, helium is much more expensive and you can not produce it yourself, but it also eliminates many problems, mostly regarding safety and legality of the aircraft.

[greensteam]

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.

I believe the inimitable guys on Myth Busters did this. You would find it on Youtube

Also for an interim "airship" fix for the desperate junky, Revell do a minikit of the Hindenburg which is dirt cheap: http://www.revell.de/en/products/model_kits/easykit/mini_kits/index.html?id=241&KOKANR=01&KOSCHL=09&KGSCHL=&L=1&page=1&sort=0&nc=&searchactive=&q=&SWO=&ARMAS4=&PHPSESSID=4131d84a785416d9c00cc88c028d4d7b&KZSLPG=&offset=1&cmd=show&ARARTN=06700&sp=1

I have made one into a sort of medal that I wear to steampunk events

[kirinyaga]

Hmmm... if I double the proportions, to 8m long and 4m diameter, and budget 200g/m^2, it increases the available lift (assuming Hydrogen) to a tad over 67kg. Put two of these together, and you have something that can serve as the lift for a personal flying machine. On it's own, it could serve as the lifting component of a small Airship, if the pilot is light. Put four of these together, and you easily have the mass budget for a two person craft.

Seepage is a problem, but have you noticed how metallic Mylar balloons retain their Helium for far longer than ordinary Latex ones? It's because of the metalized layer, preventing the Helium from escaping.

Remember to calculate volume you need to take the radius, not the diameter, that's why your 4x1 module is only 3.1 m³
With a 8x4, you'll have 100 m³ and 125 m², or 100kg of lift and 25kg of fabric for 75kg net lift. That's the size of a small hot air balloon tho, so at this point you can just make one. Or two for aesthetics if you prefer. But there is no cost gain over a traditionnal design. The base is using too small of a cell will give you too small of a lift and lead to additional costs.

Believe me, mylar is not a good idea. That thing has nothing of the solidity of a good ripstop fabric. Hot air balloon fabric is a bit lighter because you can do with the sippage, however the lift is less. I think someone tried to put mylar on ripstop fabric to decrease heat losses in a hot air balloon. The benefit was not obvious.

And hydrogen is just illegal to use in a balloon in a lot of countries. Baron zeppelin himself first planned to have 16 inner cells of hydrogen inside the 16 bigger ones of helium, to prevent them to be in contact with air oxygen. When it was obvious he wouldn't be able to get enough helium, he went for an all hydrogen fill-up but kept his original design so he could switch back to the safer setup.

If I remember well, the guys from MythBuster used a lot of very long and very thin modules of PE plastic, put horizontally. They tried to build a working "helium raft" for a onetime use : it was a poor design from the very beginning since they only wanted to show what large of a very light raft was needed to lift a single man. They failed due to their poor attachment system (sticky tape ). Note also they spent a huge amount of time to fill all these modules with helium.

If you do the stitching yourself, building a hot air balloon is not that expensive, only time consuming.

[19th Century Space Pilot]

No, the volume of a 4m long and 2m diameter cylinder is 12.5, since the radius is 1m, and the volum is 4 x radius x pi.

My point with the Mylar is that metallizing the skin of whatever fabric you use reduces the loss of your lifting gas, if it's something like Hydrogen or Helium.

You say that using Hydrogen is illegal, but have you any links to prove it?

[popuptoaster]

I dunno if using hydrogen as a lifting gas is legal or not, but storing and transporting it is tightly regulated in the UK, even buying the tanks to store it is difficult, i have to rent the bottles for my oxy torch or no one will fill them.

[kirinyaga]

Oh, you made a typo, then :

...
If the modules are cylinders 4m long and 1m diameter
...

(emphasis added by myself)

For hydrogen, I can't give you an extensive list of regulations in europe or a link in english, but I can tell you in France it is prohibited for both sportive and commercial flights. Well, I guess if a company conducts an extensive protocol of tests and studies to prove a particular design is safe, they may accept it, but an amateur built hydrogen balloon will be rejected.

[19th Century Space Pilot]

Oh, I made a typo somewhere, which I corrected in my later posts. I meant 2m diameter.

It may be illegal in France, the EU even, but I don't think the UK (where I live) has made it illegal (I'll have to look into it). The UK is... different, in that they take a while to implement EU legislation that the continent has already passed. Hwever, it appears that storing it is highly regulated

[greensteam]

Oh, I made a typo somewhere, which I corrected in my later posts. I meant 2m diameter.

It may be illegal in France, the EU even, but I don't think the UK (where I live) has made it illegal (I'll have to look into it). The UK is... different, in that they take a while to implement EU legislation that the continent has already passed. Hwever, it appears that storing it is highly regulated

In UK perhaps not so much specifically illegal as you would never get an airworthiness certificate?

[maltedfalcon]

Firstly Hydrogen as a lifting gas is legal everywhere.
any old style gas ballon, the kind that has a vent on the top and vents gas to descend uses hydrogen.
Helium would be too expensive.

you just have to enforce the no smoking/open flame regulations.

secondly a modular design would have decidedly less lift than non-modular.
as each module would need to be selfcontained it would be definition include identical hardware. - since there is not telling how many modules would be used, hardware on each end would be redundant and dead weight. -dead weight is the enemy of airship designers...

Thirdly, the joins between each module would either need to be very strong( and heavy) or each module would shimmy and flex at the joins, making steering /maintaining a heading difficult.


on other points, - the goodyear blimp as well as ZepplinNT are not sewn, they are glued together.

the lift equations Ive seen in this thread are a bit optimistic, as they do not include weight of the envelope and are also based on gas measured at basically room temperature.
unfortunately in the morning gas is colder and much denser making it heavier and able to lift much less.
in the heat of the day it is much expanded giving it greater lift, but also larger volume,  making flying a game of pop goes the airship unless you vent excess gas over the side which means as it cools, in the evening you drop like a rock. uness you plan strictly on flying your airship indoors you need to add at least 30% to your volumes.

The larger airships overcame this by having condensers which allowed them to use water as a ballast, dump the water instead of gas and replacing it as the day went on... all of which adds weight to your airship

Also your lift figures tend to not include engines and fuel,  with which you run into one of the small ship paradoxes, To gain enough lift to carry an  engine (and fuel)  big enough to control your envelope  you need a bigger envelope. Bigger envelopes are at the mercy of the winds and require larger engines and control surfaces, which means you need a bigger envelope, which is then effected more by the winds, which.... you get it...

The smallest (human powered) airship was the white dwarf figure your modules would each need to be about this size...

WHITE DWARF SPECS
Year built:  1985
Designed and built by:  Bill Watson
Built for:  Gallagher, the comedian
Dimensions

        Envelope length:  48'
        Maximum diameter:  17'
        Volume:  6200 cubic feet
        Overall height:  27"

Weights
        Empty:  140 lbs.
        Pilot weight range:  90-250 lbs.
        Maximum take-off weight:  390 lbs.

Performance
       Maximum level speed:  12 mph
       Average cruising speed:  6-7 mph

Construction
        Envelope:  Helium filled, non-rigid polyurethane coated nylon.
        Helium maintained at average slight pressure of 0.02  lbs/sq. in.  No ballonets.
       Fuselage:  Open framework structure of 2024 T3 and 7075 T6 aluminum, stressed to 4+ Gs, attached to the envelope by  24 Dacron sheathed Kevlar lines.
       Ballasting: two water ballast tanks with pilot-controlled drains and up to 60 lbs. of lead ballast control buoyancy.
       Venting:  A three-inch diameter plug alongside the seat can be lifted by the pilot to vent helium.  It opens automatically at a pressure of 4 inches of water.
       Aerodynamic controls:  Large Mylar covered styrofoam and spruce rudder.
       Passengers:  pilot only
       Power system:  Pedal power, producing approx. 10 lbs. of  cruise thrust via 4:1 gearing and plastic chain drive to a two-blade pusher propeller made of spruce and Styrofoam.
       Propeller can be vectored up and down for vertical control.

Misc.
        Cost to fill:  approx. $1000.00
        FAI World for Duration, Class B Airships, BA-1 through BA-10, achieved by pilot Bryan Allen in 1985.

More
  

[kirinyaga]

That's a nice little airship 
It needs very good weather conditions to take off, however, 20km/h wind and it can't avoid moving.

If you're sure zepplinNT is glued and not sewn, do you know what fabric/glue they're using and if the process still require human supervision ? Maybe this could be automated.

PS: both initial poster and me did include fabric weight in our calculations.

[19th Century Space Pilot]

It only cost $1000 to fill? That's suprisingly cheap, especially for a Helium filled airship...

Enlarging the module to 8m long and 4m dimater would give a single one sufficient lift to lift 90kg, if filled with Hydrogen and with a fabric weight of 200g, if I remember correctly. If the person weighs 70kg, that gives 20kg for them to attach a chair/gondola, and somekind of propulsion, to their craft. It also makes ataching them together to form a bigger Airship easier, because you don't need to attach them lengthways (two side by side, with the gondala in between, would make a nice two seater, and you can put another two under those modules to form a four seater).

[kirinyaga]

it was probably 1000$ in 85, not now. It is also very small : only 175m³.

[akumabito]

*RESURRECTS THREAD FROM PAGE 5*

I just came across this link: http://www.voliris.com/v900.htm
Now that's a sexy little airship right there! Thee's some definite SP potential with a proper gondola swung underneath..