Airships
- Thread starter Miles
- Start date
j3tch1u
10 kW
that is a very interesting article! hope we see those efforts come to fruition in our lifetime.
etard
100 kW
A noble dream indeed Miles! So which design looks to be most realistic to you guys? I like the Aeolus Airship, it seems most aerodynamic, but might have trouble with crosswinds. And of course the High Altitude Airship will probably become a reality because of it's military applications. Thanks Miles. 
mf70
1 µW
While materials science has progressed greatly since the Hindenburg disaster, the basic physics of lighter-than-air flight remain. For a volume of structure, you don't get very much lift. The biggest lift margins are near the ground.
This means that structure tend to be large and flown low, down among the bad weather. That's a recipe for mid-air breakups and very limited payloads.
When reality testing a proposal, look at
* how many self-supporting structures would be needed (thin projections, flat sides)
* How much non-lifting hardware is listed (solar cells, fans, glass-frigging-windows)
* Where the aircraft will travel (margins are far tighter at 30,000 feet than 3,000)
Pretty pictures are easy. Getting a vehicle to fly is hard. (That said, there are man-powered airships
http://www.thetechherald.com/article.php/200840/2156/Pedal-powered-airship-is-a-Channel-crossing-flop
... but you can see how thin the power/speed/lift/payload margins are.
mark
This means that structure tend to be large and flown low, down among the bad weather. That's a recipe for mid-air breakups and very limited payloads.
When reality testing a proposal, look at
* how many self-supporting structures would be needed (thin projections, flat sides)
* How much non-lifting hardware is listed (solar cells, fans, glass-frigging-windows)
* Where the aircraft will travel (margins are far tighter at 30,000 feet than 3,000)
Pretty pictures are easy. Getting a vehicle to fly is hard. (That said, there are man-powered airships
http://www.thetechherald.com/article.php/200840/2156/Pedal-powered-airship-is-a-Channel-crossing-flop
... but you can see how thin the power/speed/lift/payload margins are.
mark
Hi Mark,
Also:
http://home.teleport.com/~reedg/whitedwarf.html
Southampton University UK made one in the '80s.
Nottingham University UK:
http://ibikeride.com/mountain-bike-general-posts/latest-news/giant-pedal-powered-airship
And this is interesting:
http://www.dendronautics.com/USERIMAGES/d4-operation.pdf
Also:
http://home.teleport.com/~reedg/whitedwarf.html
Southampton University UK made one in the '80s.
Nottingham University UK:
http://ibikeride.com/mountain-bike-general-posts/latest-news/giant-pedal-powered-airship
And this is interesting:
http://www.dendronautics.com/USERIMAGES/d4-operation.pdf
Malcolm
10 kW
Are there any hybrid designs – an airship that's slightly heavier than air, with lifting surfaces? I used to do some windsurfing and a lot of the faster boards would sink without power.
PedalingBiped
100 W
I was interested in this subject back in the 80's. Did all my calculations with a 4 function calculator.
The payload is a function of the volume which has pi times radius square in the formula.
Which means if you have an airship that will lift 1000 lbs then to lift 2000 lbs you need 4 times the volume.
To lift a lot of weight then you need a massive airship.
A blimp is just a gas bag with no internal structure. I believe they can only fly around 20 - 30 mph
A dirigible has an internal structure or framework. I believe they can go up to 100 mph with enough power.
The Germans made truss rings made of an aluminum alloy. They then stretched the flammable skin over the trusses. Then they hung bags filled with gas inside
Hydrogen has more lift then Helium but with the Hindenburg in our collective memory, it is just about impossible to use.
The Hindenburg actually burned up because it's skin was extremely flammable.
As for negative buoyancy I would think you would need to increase the size of the envelope to make up for the weight of the wing. Or on second thought, add the wing to a neutral buoyant envelope then the wing would have to provide lift for itself.
Thanks to all of you that have posted links. I haven't thought about this subject in a long time.
It seems I will have google this subject in more depth.
The payload is a function of the volume which has pi times radius square in the formula.
Which means if you have an airship that will lift 1000 lbs then to lift 2000 lbs you need 4 times the volume.
To lift a lot of weight then you need a massive airship.
A blimp is just a gas bag with no internal structure. I believe they can only fly around 20 - 30 mph
A dirigible has an internal structure or framework. I believe they can go up to 100 mph with enough power.
The Germans made truss rings made of an aluminum alloy. They then stretched the flammable skin over the trusses. Then they hung bags filled with gas inside
Hydrogen has more lift then Helium but with the Hindenburg in our collective memory, it is just about impossible to use.
The Hindenburg actually burned up because it's skin was extremely flammable.
As for negative buoyancy I would think you would need to increase the size of the envelope to make up for the weight of the wing. Or on second thought, add the wing to a neutral buoyant envelope then the wing would have to provide lift for itself.
Thanks to all of you that have posted links. I haven't thought about this subject in a long time.
It seems I will have google this subject in more depth.
Hi PB,PedalingBiped said:
Maybe you meant something other than what you actually wrote? :wink: Lift is directly proportional to the volume of air displaced.
I can remember, when I was young, being fascinated by the possibility of making a vacuum balloon (as proposed by Francesco de Lana in 1670)
Tiberius
10 kW
Regarding vacuum / hydrogen / helium...
The lift comes from the difference in density between the gas used and normal air, and that simply depends on the molecular weight.
A vacuum is zero, Hydrogen 2 and Helium 4. But air is about 28, so the difference in buoyancy between using hydrogen and helium isn't that much, 26 versus 24.
The other way is to use hot air. The density of a gas at the same pressure is inversely proportional to the absolute temperature. So if you can heat the air in the envelope by 50 C that will have an equivalent density of 28 * (290)/(290+50) = about 24.
You can immediately see why hot air balloons have to be many times the size of gas balloons.
Nick
The lift comes from the difference in density between the gas used and normal air, and that simply depends on the molecular weight.
A vacuum is zero, Hydrogen 2 and Helium 4. But air is about 28, so the difference in buoyancy between using hydrogen and helium isn't that much, 26 versus 24.
The other way is to use hot air. The density of a gas at the same pressure is inversely proportional to the absolute temperature. So if you can heat the air in the envelope by 50 C that will have an equivalent density of 28 * (290)/(290+50) = about 24.
You can immediately see why hot air balloons have to be many times the size of gas balloons.
Nick
AussieJester
1 TW
Miles said:It's my dream to develop a one or two person pedal/electric airship
Did you see James May in the caravan blimp Miles? :lol:
KiM
PedalingBiped
100 W
OK, I was wrong, I had it backwards!!!! 
double the diameter and you get 4 times the lift.
cylinder 10ft by 100 ft has 2,500 cubic ft.
20ft by 100 ft has 10,000 cubic ft.
Hydrogen has a lift 1.202 gram/liter
Helium 1.113 gram/liter
An 8% difference
(Helium isn't 100 % because it is mined and has impurities, so the difference is slightly higher)
So for the above cylinders
10ft Helium 173 lb/lift
10ft Hydrogen 187 lb/lift
20ft Helium 697 lb/lift
20ft Hydrogen 750 lb/lift
When you get to the 200 ft diameter range, a small increase will get you a large lift increase. You have to decide when to stop increasing and just build.
There also seems to be a preferred ratio of 3:1 example 30ft diameter 100 ft length: 50ft diameter and 150 ft length.
double the diameter and you get 4 times the lift.
cylinder 10ft by 100 ft has 2,500 cubic ft.
20ft by 100 ft has 10,000 cubic ft.
Hydrogen has a lift 1.202 gram/liter
Helium 1.113 gram/liter
An 8% difference
(Helium isn't 100 % because it is mined and has impurities, so the difference is slightly higher)
So for the above cylinders
10ft Helium 173 lb/lift
10ft Hydrogen 187 lb/lift
20ft Helium 697 lb/lift
20ft Hydrogen 750 lb/lift
When you get to the 200 ft diameter range, a small increase will get you a large lift increase. You have to decide when to stop increasing and just build.
There also seems to be a preferred ratio of 3:1 example 30ft diameter 100 ft length: 50ft diameter and 150 ft length.
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