Airships

Things that fly
Post Reply
User avatar
Miles   100 GW

100 GW
Posts: 11020
Joined: Mar 16 2007 4:15pm
Location: London UK

Airships

Post by Miles » Jun 20 2010 6:17am


User avatar
j3tch1u   10 kW

10 kW
Posts: 686
Joined: Dec 26 2008 2:09pm
Location: Taipei, Taiwan

Re: Electric airship - conceptual designs

Post by j3tch1u » Jun 20 2010 6:36am

that is a very interesting article! hope we see those efforts come to fruition in our lifetime.

User avatar
Miles   100 GW

100 GW
Posts: 11020
Joined: Mar 16 2007 4:15pm
Location: London UK

Re: Electric airship - conceptual designs

Post by Miles » Jun 20 2010 6:52am

It's my dream to develop a one or two person pedal/electric airship :D

User avatar
etard   1 MW

1 MW
Posts: 1935
Joined: Aug 03 2008 3:28pm
Location: Redlands, CA

Re: Electric airship - conceptual designs

Post by etard » Jun 21 2010 12:04pm

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. :D
Four wheels moves the body, Two wheels moves the soul
Thanks to Justin @ http://www.ebike.ca He brings the soul to ES

mf70   1 µW

1 µW
Posts: 4
Joined: Jul 10 2007 3:22pm
Location: Takoma Park, MD

Re: Electric airship - conceptual designs

Post by mf70 » Jun 21 2010 3:07pm

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.ph ... ssing-flop

... but you can see how thin the power/speed/lift/payload margins are.

mark

User avatar
Miles   100 GW

100 GW
Posts: 11020
Joined: Mar 16 2007 4:15pm
Location: London UK

Re: Electric airship - conceptual designs

Post by Miles » Jun 21 2010 3:34pm

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-gene ... ed-airship

And this is interesting:
http://www.dendronautics.com/USERIMAGES ... ration.pdf

User avatar
Malcolm   10 kW

10 kW
Posts: 755
Joined: Jan 26 2007 9:35am
Location: Newcastle upon Tyne, UK

Re: Electric airship - conceptual designs

Post by Malcolm » Jun 21 2010 3:47pm

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.

User avatar
Miles   100 GW

100 GW
Posts: 11020
Joined: Mar 16 2007 4:15pm
Location: London UK

Re: Electric airship - conceptual designs

Post by Miles » Jun 21 2010 4:05pm


User avatar
PedalingBiped   100 W

100 W
Posts: 145
Joined: Mar 23 2008 11:42pm
Location: Renton, WA

Re: Airships

Post by PedalingBiped » Jun 30 2010 1:56am

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.
Mongoose MTB, full suspension WE BD 36 at 48V, 7 SLA
Carpe Diem

User avatar
Miles   100 GW

100 GW
Posts: 11020
Joined: Mar 16 2007 4:15pm
Location: London UK

Re: Airships

Post by Miles » Jun 30 2010 2:11am

PedalingBiped wrote: Which means if you have an airship that will lift 1000 lbs then to lift 2000 lbs you need 4 times the volume.
Hi PB,

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) :)

User avatar
Tiberius   10 kW

10 kW
Posts: 871
Joined: Jan 14 2008 7:52am
Location: Rural England

Re: Airships

Post by Tiberius » Jun 30 2010 4:52am

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

User avatar
AussieJester   100 GW

100 GW
Posts: 8736
Joined: Mar 11 2008 3:33am
Location: Perth Western Australia

Re: Electric airship - conceptual designs

Post by AussieJester » Jun 30 2010 5:30am

Miles wrote:It's my dream to develop a one or two person pedal/electric airship :D
Did you see James May in the caravan blimp Miles? :lol:

KiM

User avatar
Miles   100 GW

100 GW
Posts: 11020
Joined: Mar 16 2007 4:15pm
Location: London UK

Re: Electric airship - conceptual designs

Post by Miles » Jun 30 2010 6:21am

AussieJester wrote: Did you see James May in the caravan blimp Miles? :lol:
I have now.... :)

User avatar
PedalingBiped   100 W

100 W
Posts: 145
Joined: Mar 23 2008 11:42pm
Location: Renton, WA

Re: Airships

Post by PedalingBiped » Jul 01 2010 3:07am

OK, I was wrong, I had it backwards!!!! :mrgreen:

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.
Mongoose MTB, full suspension WE BD 36 at 48V, 7 SLA
Carpe Diem

Post Reply