Airships, Blimps, anyone anyone

[dingpud]

Have any of the members out there done anything with airships or blimps? I am getting kind of interested in them and was planning on doing a DIY blimp or airship and wanted to know if anyone else has tinkered around with anything.

There are some small scale kits out there...
http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A44817
which are cool, but I'm looking for something that could maybe work outdoors and be a little more "rough and tough".

The mylar style balloons just don't seem like they could withstand...anything...

Weatherballoons are neat, but they only go one direction...well, two directions technically. Here's a really neat project a group did...
http://www.natrium42.com/halo/flight2/

So if anyone out there knows of blimp or airship manufacturers (other than ILC Dover and TCOM) let me know. Or if you've had success making your own airbags or envelopes, let me know.

Thanks

 

[KalamMekhar]

Beyond the hot air balloon type of home craft, I haven't ran across anything in my design books that helps with air ships. I will look around some more and see if I can find some stuff on DIY airships.

 

[dingpud]

Anything that you've got on airships...construction, projects, theory, etc. It's all good stuff to me...

 

[Lancelot59]

Looks like we have a common interest! I've been looking at trying to build one myself. From what I've researched so far the envelope is the trickiest part in a DIY situation. I had an idea for a rather cheap but what should be effective solution. Stuff a bag full of mylar balloons. The bag would just be a cover, and you just need to evenly pack all the balloons into the envelope.

The great thing is that you have a bunch of isolated cells, so even if some get punctured you don't lose all your lift.

I took a quick look around YouTube and found this: http://www.youtube.com/user/minizepp

These guys seem pretty good: http://www.minizepp.com/

 

[dingpud]

Yeah, I've thought about the isolated cells as well. Just think that an exoskeleton would then be required to keep it's shape. I've been doing some heat sealing of some mylar material to see how well it holds the helium...didn't realize how much money He was...

thanks for the link.

 

[Lancelot59]

How well has the mylar held up?

 

[dingpud]

As long as you get the stuff that you can actually heat seal...it seems to work well. Holds He decent...super fragile though. I am curious what the "big boys" are using in theirs. I am sure it's some sort of combination engineered material which us DIYers can't get a hold of cheap...

 

[Lancelot59]

As long as you get the stuff that you can actually heat seal...it seems to work well. Holds He decent...super fragile though. I am curious what the "big boys" are using in theirs. I am sure it's some sort of combination engineered material which us DIYers can't get a hold of cheap...

Possibly, or it could be something much simpler. Perhaps there is some compound available that we could just coat some fabric into create a gas tight cell. According to HowStuffWorks.com most full sized envelopes are made from "a durable, airtight, lightweight fabric (polyester composites) that is much like the fabric of a space suit." There has to be a cheaper way of getting it to work though.

 

[mugaliens]

The Hindenburg's gas bags were made of "goldbeater's skin," which is layered between gold before it was beaten into leaf as this as one micrometer.

Very expensive!

Aluminized mylar (boPET film) is cheaper, stronger, and more effective.

 

[Lancelot59]

The Hindenburg's gas bags were made of "goldbeater's skin," which is layered between gold before it was beaten into leaf as this as one micrometer.

Very expensive!

Aluminized mylar (boPET film) is cheaper, stronger, and more effective.

Yeah, I don't have the money to get that much gold. However mylar should be fairly cheap. The only problem I see is trying to seal the seams. But if we can find a solution to that, this should become fairly simple. A flat sheet of material could be cut into whatever shapes we need.

 

[mugaliens]

Yeah, I don't have the money to get that much gold. However mylar should be fairly cheap. The only problem I see is trying to seal the seams. But if we can find a solution to that, this should become fairly simple. A flat sheet of material could be cut into whatever shapes we need.

Actually, BoPET is so smooth that it will adhere strongly to itself if it weren't not treated to prevent this. For improved vapor barrier performance, it's aluminize and a layer of polyethylene is added, which improves its ability to be sealed as well as its puncture resistance.

I don't think sealability will be an issue. The question is, when you start using large, house-sized helium-filled bags, how does one anchor them in a way which contains them while evenly distributing the forces? BoPET's tensil strength is seriously strong (something like 4 GPa), but you don't want to make it thick enough to carry the lifting stresses itself. Just thick enough to maintain containment of the helium. I'm thinking balloon-shaped nets with an interlocking hexagonal weave made of kevlar, but that might be overkill. Nylon would be heavier, bit I think it would work just fine. Cheaper, too, and nylon also has excellent abrasion resistance.

Of course silk might work, but there are serious cost issues with using silk.

 

[Lancelot59]

Actually, BoPET is so smooth that it will adhere strongly to itself if it weren't not treated to prevent this. For improved vapor barrier performance, it's aluminize and a layer of polyethylene is added, which improves its ability to be sealed as well as its puncture resistance.

I don't think sealability will be an issue. The question is, when you start using large, house-sized helium-filled bags, how does one anchor them in a way which contains them while evenly distributing the forces? BoPET's tensil strength is seriously strong (something like 4 GPa), but you don't want to make it thick enough to carry the lifting stresses itself. Just thick enough to maintain containment of the helium. I'm thinking balloon-shaped nets with an interlocking hexagonal weave made of kevlar, but that might be overkill. Nylon would be heavier, bit I think it would work just fine. Cheaper, too, and nylon also has excellent abrasion resistance.

Of course silk might work, but there are serious cost issues with using silk.

The strength of that adhesion might not hold the gas in once you get higher up and the gas starts to expand. It would have to be sealed with something. The mythbusters used tape to decent effect when they made the balloon out of lead foil. Some higher quality stuff should do the job well.

Balloon shaped nets seems like a good idea, if the material really lacks that tensile strength. You might even be able to get away using cables. The way I best imagine this working is having two rings on the top and bottom that the ends of the cables attach to, and then just have some thin wire wrap around each of the cables in several places along the height of the cell to keep the cables aligned.

 

[mugaliens]

The strength of that adhesion might not hold the gas in once you get higher up and the gas starts to expand.

The mylar bags would never be pressurized, but would simply be designed to expand. Besides, we're not talking 35,000 ft operations, here, as the carriage wouldn't be pressurized, so only about 20% volume differential between sea level and max operating altitude.

It would have to be sealed with something.

Self-sealed without the additives. Heat-sealed during the epitaxial alignment. One of about a thousand adhesives on the book, half of which would do admirably?

It's not an issue.

The mythbusters used...

With all due respect to their experience, it's a TV show.

 

[Lancelot59]

The mylar bags would never be pressurized, but would simply be designed to expand. Besides, we're not talking 35,000 ft operations, here, as the carriage wouldn't be pressurized, so only about 20% volume differential between sea level and max operating altitude.

Makes sense. I wouldn't want to take this higher one or two thousand feet.

Self-sealed without the additives. Heat-sealed during the epitaxial alignment. One of about a thousand adhesives on the book, half of which would do admirably?

My knowledge of BoPET is pretty limited, so I'll defer to your assessment. I'll do a little more research.

With all due respect to their experience, it's a TV show.

I mentioned it because it's a solution that worked fairly well.

 

[mugaliens]

I mentioned it because it's a solution that worked fairly well.

Ok. I'll run with it - Although gold is 70% more dense than lead, it's both far more maleable, and vapor deposition products do not corrode (oxidize). It might very well be a better solution than aluminized mylar, provided it provided better overal characteristics.

We might find beryllium to be the optimum choice, but since we know the characteristics of them all, let's specify the design requirements, first, then select for the best, perahps most effective life-cycle cost combination of materials within those design specs.

 

[Lancelot59]

Ok. I'll run with it - Although gold is 70% more dense than lead, it's both far more maleable, and vapor deposition products do not corrode (oxidize). It might very well be a better solution than aluminized mylar, provided it provided better overal characteristics.

We might find beryllium to be the optimum choice, but since we know the characteristics of them all, let's specify the design requirements, first, then select for the best, perahps most effective life-cycle cost combination of materials within those design specs.

Just to clarify, I was talking about the tape as the solution, and not the lead foil.

Given the scale we're working with, tall cylindrical cells don't have the volume we need. It depends on how the cells are going to be laid out. I'm thinking a cylinder laid out along the longitudinal axis. Big radius, and short. It would make the most effective use of the space available inside the ship. Each cell fits in between two frames, and should follow the curve of the skin fairly well.

I wonder if there's a specific shape that could be used on the actual dirigible that would offer more stability. A sideways oval I guess? Might as well start simple with a circular frame.

 

[mugaliens]

Just to clarify, I was talking about the tape as the solution, and not the lead foil.

Given the scale we're working with, tall cylindrical cells don't have the volume we need. It depends on how the cells are going to be laid out. I'm thinking a cylinder laid out along the longitudinal axis. Big radius, and short. It would make the most effective use of the space available inside the ship. Each cell fits in between two frames, and should follow the curve of the skin fairly well.

I wonder if there's a specific shape that could be used on the actual dirigible that would offer more stability. A sideways oval I guess? Might as well start simple with a circular frame.

http://www.nlhs.com/construc.htm" of one of the Hindenburg's gas cells, along with some other pics of its interior construction.

The gas cells cannot be full sized at sea level due to expansion at altitude. You can see this in the picture and accompanying text in the link.

As for shape, a hocky puck turned on edge might be appropriate, although the lower portion would be somewhat flattened to allow for expansion. Line 'em up along their mutual axis and you whind up with the aerodynamically streamlined form of a dirigible.

Alternatively, instead of a single hocky puck per cell, you can use two balloon-shaped nets containing a mylar bag. :)

Another advantage of mylar is the fact that it can be made both electrically conductive by means of the aluminized coating, while electrically grounded by the same means. Static can be reduced by means of this and other coatings, though I'm unsure of the static effects of enclosing mylar bags in nylon or kevlar mesh nets.

 

[Lancelot59]

http://www.nlhs.com/construc.htm" of one of the Hindenburg's gas cells, along with some other pics of its interior construction.

The gas cells cannot be full sized at sea level due to expansion at altitude. You can see this in the picture and accompanying text in the link.

As for shape, a hocky puck turned on edge might be appropriate, although the lower portion would be somewhat flattened to allow for expansion. Line 'em up along their mutual axis and you whind up with the aerodynamically streamlined form of a dirigible.

Seems like a decent shape...although that's the exact shape I suggested.

Alternatively, instead of a single hocky puck per cell, you can use two balloon-shaped nets containing a mylar bag. :)

I'm unsure what you mean here.

Another advantage of mylar is the fact that it can be made both electrically conductive by means of the aluminized coating, while electrically grounded by the same means. Static can be reduced by means of this and other coatings, though I'm unsure of the static effects of enclosing mylar bags in nylon or kevlar mesh nets.

Things might get sparky.

 

[mugaliens]

Things might get sparky.

Not a problem if you're using helium. If you're using hydrogen, we're fairly adept about eliminating sparking, these days, by means of various semi-conducting coatings.

 

[Lancelot59]

Not a problem if you're using helium. If you're using hydrogen, we're fairly adept about eliminating sparking, these days, by means of various semi-conducting coatings.

Okay, so how about propulsion? Electric motors seem like the simplest solution. If there's enough lifting capacity solar panels could even be mounted on the ship.

 

[mugaliens]

Okay, so how about propulsion? Electric motors seem like the simplest solution. If there's enough lifting capacity solar panels could even be mounted on the ship.

Fine! Make it a flattened spheroid and add the solar panels - what do you come up with?

 

[Lancelot59]

A boxy looking spheroid?

 

[mugaliens]

A boxy looking spheroid?

I was thinking more along the lines of the flattened and elongated saucer shapes I've seen on the pages of Popular Science over the years. Whether the solar area would provide enough energy to overcome winds or not is subject for discussion.

So, let's do it: When looking at it head-on, it would be an ellipsoid who's semimajor axis is twice that of its semiminor axis. From the top, it would be the same. It would have enough fin area to stabilize it longitudinally. It's helium, and like all blimps, relies on overpressure to keep it's shape, moderated with ballonets. Let's figure enough volume, less basic blimpage, to lift 5 tons.

I'm figuring that if operated between 9am and 3pm sideral, only half its upper surface area would be available to receive solar at any given time. Question: On a bright, sunlit day, would this even be enough to buck a 30-kt wind?

 

[Lancelot59]

I was thinking more along the lines of the flattened and elongated saucer shapes I've seen on the pages of Popular Science over the years. Whether the solar area would provide enough energy to overcome winds or not is subject for discussion.

Could you please link me to those articles?

So, let's do it: When looking at it head-on, it would be an ellipsoid who's semimajor axis is twice that of its semiminor axis. From the top, it would be the same. It would have enough fin area to stabilize it longitudinally. It's helium, and like all blimps, relies on overpressure to keep it's shape, moderated with ballonets.

I thought we were going to have gas cells, with the outer skin just being a cover over a rigid frame. I think that would support the weight of the solar cells better too. That and anything else that might need to be attached.

Let's figure enough volume, less basic blimpage, to lift 5 tons.

MADNESS! That's a lot of weight to carry around. I thought this was going to be a RC airship. Not a full sized ship meant to carry people...although that would be pretty fun.

I'm figuring that if operated between 9am and 3pm sideral, only half its upper surface area would be available to receive solar at any given time. Question: On a bright, sunlit day, would this even be enough to buck a 30-kt wind?

I can't comment much on this because I haven't seen the shape. But I think that most of the time in that interval it would get sun...unless you live in a part of the world where there isn't much daylight. I live in west Canada, and 9 to 3 most of the time would easily light up a flat surface. It wouldn't get all of it, but most.

Don't forget to we can take advantage of light that gets reflected from the ground off of windows, water, etc.

 

[mugaliens]

Could you please link me to those articles?

No. They were from the 80s. I did a couple of online searches before I posted my last, to no avail. If you've ever consistantly read PS, you will recall them as being proposed for duty in the foresting industy, with other potential heavy-lifiting duties. One version included four Sikorsky S-64 Skycranes, but http://www.youtube.com/watch?v=_7jENWKgMPY" built with four Sikorsky H-34J helos didn't fare so well during testing. Fortunately, only one pilot died. This design, however, involved a traditional cigar-shaped blimp, rather than a flattened one.

I thought we were going to have gas cells, with the outer skin just being a cover over a rigid frame. I think that would support the weight of the solar cells better too. That and anything else that might need to be attached.

Fine with me. It's just that a dirigible needs to be much larger, and probably using hydrogen, in order to support the weight of the structure.

MADNESS! That's a lot of weight to carry around. I thought this was going to be a RC airship. Not a full sized ship meant to carry people...although that would be pretty fun.

A friend of mine had an RC blimp. Fun! We used to pilot it around the Rector Field House at my alma mater.

I can't comment much on this because I haven't seen the shape. But I think that most of the time in that interval it would get sun...unless you live in a part of the world where there isn't much daylight. I live in west Canada, and 9 to 3 most of the time would easily light up a flat surface. It wouldn't get all of it, but most.

If the upper surface could be made clear, perhaps the solar cells could lie flat in a plane inside the blimp?

Don't forget to we can take advantage of light that gets reflected from the ground off of windows, water, etc.

I'm not sure that little reflection (less than 15%) would be worth the weight penalty.

 

[Lancelot59]

No. They were from the 80s. I did a couple of online searches before I posted my last, to no avail. If you've ever consistantly read PS, you will recall them as being proposed for duty in the foresting industy, with other potential heavy-lifiting duties. One version included four Sikorsky S-64 Skycranes, but http://www.youtube.com/watch?v=_7jENWKgMPY" built with four Sikorsky H-34J helos didn't fare so well during testing. Fortunately, only one pilot died. This design, however, involved a traditional cigar-shaped blimp, rather than a flattened one.

Well if they were printed in the 80's I wasn't even alive back then.

Fine with me. It's just that a dirigible needs to be much larger, and probably using hydrogen, in order to support the weight of the structure.

That it would, but it would make mounting equipment on it much easier. Things such as the solar cells. Helium would work...or perhaps a combination of hydrogen and helium? I can see mixing the two making a less volatile mix if things do go south. Also, a rigid frame is going to be needed for what I have in mind for a future design...think lots of powerful engines.

A friend of mine had an RC blimp. Fun! We used to pilot it around the Rector Field House at my alma mater.

I bet. I'd prefer to start with a small project for proof of concepts and a simple test rig.

If the upper surface could be made clear, perhaps the solar cells could lie flat in a plane inside the blimp?

That doesn't really take the most advantage of the surface area we have. I think it would be better to have cells around the outside of the ship mounted on the frame. Having them inside I see being needed if the cells would rotate to capture the most sunlight. That complicates the design a bit. Also, where would they go? Most of the space is going to be taken up by the cells. Unless you have a strip down the middle, but that limits the cells you can have. Putting the cells outside seems to be the best solution.

I'm not sure that little reflection (less than 15%) would be worth the weight penalty.

I guess not. Not unless you were operating over water or snow all the time. Snow can reflect enough light to blind people, I think that has potential as a specific application (operating over snow, not blinding people).

 

[mugaliens]

Helium would work...or perhaps a combination of hydrogen and helium? I can see mixing the two making a less volatile mix if things do go south.

That sounds good as an initial thought, but studies have shown that anything greater than 4% hydrogen becomes flammable.

Also, a rigid frame is going to be needed for what I have in mind for a future design...think lots of powerful engines.

Dirigibles aren't effective for use with helium. Just not enough lifting power.

That doesn't really take the most advantage of the surface area we have. I think it would be better to have cells around the outside of the ship mounted on the frame. Having them inside I see being needed if the cells would rotate to capture the most sunlight. That complicates the design a bit. Also, where would they go? Most of the space is going to be taken up by the cells. Unless you have a strip down the middle, but that limits the cells you can have. Putting the cells outside seems to be the best solution.

I was thinking of saving weight. Using a clear envelope and a central axial truss with tiltable panels would require minimal solar panel area for maximum solar influx. The downside is allowing sunlight into the interior results in some serious heating/ballast issues, and going through any type of material will result in some transmission loss. If you are going to put them outside, it would be best to flatten the blimp/dirigible into an elongated saucer shape.

 

[Lancelot59]

That sounds good as an initial thought, but studies have shown that anything greater than 4% hydrogen becomes flammable.

So we be verrry careful with it. Make sure there's no static discharge, and plenty of ventilation to prevent heat building up. Isolate the electronics and give them good external heat sinks. The big plus is that hydrogen is much easier to get than helium. We literally could just put the electrolysis system together ourselves and run it off of a solar panel. I didn't make it myself, but I did a project on fuel cells in high school using a kit.

Dirigibles aren't effective for use with helium. Just not enough lifting power.

So I guess that it'll need to be fairly large then. Starting out with a blimp would be easier.

I was thinking of saving weight. Using a clear envelope and a central axial truss with tiltable panels would require minimal solar panel area for maximum solar influx. The downside is allowing sunlight into the interior results in some serious heating/ballast issues, and going through any type of material will result in some transmission loss. If you are going to put them outside, it would be best to flatten the blimp/dirigible into an elongated saucer shape.

That shape sounds similar to what I was thinking, but a picture would be required for certainty...I'll try drawing one on paper and posting it.

 

[Lancelot59]

That sounds good as an initial thought, but studies have shown that anything greater than 4% hydrogen becomes flammable.

So we be verrry careful with it. Make sure there's no static discharge, and plenty of ventilation to prevent heat building up. Isolate the electronics and give them good external heat sinks. The big plus is that hydrogen is much easier to get than helium. We literally could just put the electrolysis system together ourselves and run it off of a solar panel. I didn't make it myself, but I did a project on fuel cells in high school using a kit. I don't see any danger in using hydrogen as long as we're careful with it. Perhaps only fill some of the cells with it when we get to that stage? Then the hydrogen cells could be spaced out, insulated, and in the event of a leak or fire you could simply vent the cells.

Dirigibles aren't effective for use with helium. Just not enough lifting power.

So I guess that it'll need to be fairly large then. Starting out with a blimp would be easier just to get the construction techniques down and test flight systems.

I was thinking of saving weight. Using a clear envelope and a central axial truss with tiltable panels would require minimal solar panel area for maximum solar influx. The downside is allowing sunlight into the interior results in some serious heating/ballast issues, and going through any type of material will result in some transmission loss. If you are going to put them outside, it would be best to flatten the blimp/dirigible into an elongated saucer shape.

That shape sounds similar to what I was thinking, but a picture would be required for certainty...I'll try drawing one on paper and posting it. But a I said some sort of frame would be needed to carry the load up there. Maybe a semi-dirigible? It only has frames where the panels are?

 

[mugaliens]

Tell you what - let's prototype it after the GZ-20, the current model of Goodyear Blimps. It had a 45 ft diameter cylinder, with a length of 192 feet. It has two Continental IO-360 engines rated at 210 hp each, which give it a max velocity of 50 mph. That's a total of 314 kW, which gives us something to shoot for, solar panel-wise.

Let's de-rate it at bit, to just 300 kW, and a max velocity of 40 mph

Even if we were to cover the entire top half with solar cells, the effective area would only be approximately 2,700 square feet (rough estimate, only). Is that enough to generate 300 kW using modern solar cells?

 

[Lancelot59]

Tell you what - let's prototype it after the GZ-20, the current model of Goodyear Blimps. It had a 45 ft diameter cylinder, with a length of 192 feet. It has two Continental IO-360 engines rated at 210 hp each, which give it a max velocity of 50 mph. That's a total of 314 kW, which gives us something to shoot for, solar panel-wise.

Let's de-rate it at bit, to just 300 kW, and a max velocity of 40 mph

Even if we were to cover the entire top half with solar cells, the effective area would only be approximately 2,700 square feet (rough estimate, only). Is that enough to generate 300 kW using modern solar cells?

Uh...what happened to working with a small prototype? I don't have the resources to build a full sized aircraft.

 

[mugaliens]

Uh...what happened to working with a small prototype? I don't have the resources to build a full sized aircraft.

On paper! Just the calcs...

 

[Lancelot59]

On paper! Just the calcs...

You had me worried there for a sec.