Building an LTA structure with controllable lift

[Turtle]

Flame retardants should help as this is a segmented design. Keeping one part from igniting another is the main concern and only has to last a few seconds to a minute before fuel from one segment is exhausted or dispersed.

 

That pesky lightning will be an issue, I know. Any ideas on mitigating this?

 

Static should not be to much of a problem so long as the hydrogen is contained in an inert gas envelope and no ground is available, but I had not considered the problem should I need to bring the structure to ground. Hmm

 

The core will be heated, but this will not be available to the exterior. I was hoping for a solution involving some magical water and ice shedding ultra light super strong material :hihi:

 

Total lift is approx 1 Kg per cubic meter of lift gas. I anticipate I will have 20% (minimum) excess lift on this structure.

 

OK So the idea is to let the balloon rise and its tether operates a shaft/gear mechanism which drives a generator which delivers electricity to make hydrogen to go in the balloon and or power 'stuff'. :hyper:

 

Your non-conducting material tether is your ground; if it gets wet, its a conductor. If it's dry, it's a capacitor. Either way, it's an invitation for sparks. :doh:

 

I think your vertical design balloon will fold up and/or otherwise deform and exhibit poor aeordynamic stability. Then there is the altitude. How high did you say you want to go? Let's take 2,000 feet for a start. When the balloon fails, where is that 2,ooo feet of line going to fall? Over power lines perhaps. :( Onto a freeway? :)

 

This project is so rife with problems that I may just have to build a scale model. :Alien: Carry on...........:ebomb:

[Kayra]

Without going into details, some of your concerns are valid and some are not, although there is no way for you to know that without having seen the designs.

 

Conductivity and lightning is an issue.

Static should not normally be an issue as there will not be a ground for it.

 

Deformation and instability have been accounted for and are actually not an issue. Some of the expected deformations are even quite helpful.

 

Lift and tension from drag are cumulative with the largest value (a considerable amount actually) near the ground. The design leverages this to prevent "folding" and "deforming" issues.

 

Lightning.. .Hmm..

[CraigD]

How much will 1,400 to 5,200 cubic meters of Hydrogen cost initially? Where will you get it?

It’s been a couple of decades, but when I was in school, my lab bought it’s gases in big tanks. There wasn’t much difference in cost between helium and hydrogen (as I recall in the 1980s, around $20/tank when exchanging for an empty), but this, it was explained to me, was because most of the cost was due to upkeep and delivery of the tank, which massed about 60 kg, while the hydrogen inside massed less than 1 kg. 1 kg of hydrogen at 1 atm pressure is about 11 m^3. I think if you bought hydrogen by the tanker load, the gas was nearly free – you were paying mostly for its transport, as the hydrogen was a refinery byproduct which would otherwise be wasted.

 

Helium, on the other hand, is actually a rare element on Earth. Web searches for its price come up with something like $1.50 m^3, not including containers and transportation. AFAIK, nearly all helium is distilled from natural gas, and is valuable enough not to be needlessly wasted. Not all natural gas fields are helium rich – if I recall my history, a few US fields are the most productive.

 

Helium price can be wildly manipulated, somewhat to which ends the US government created the National Helium Reserve in 1925. Intentional supply restriction and price manipulation was why the big German airships of the 1920s-40s had to use hydrogen.

 

What are the regulations for handling/having that volume of flammable gas? Is it legal to put that much H in a balloon even?

As I recall, in the US there are OSHA codes that apply to handling all compressed gases. There are some special regulations about gases used in healthcare – mainly oxygen – and those with illicit use potential – mainly [ce]N2O[/ce]. There are laws and regulations about not endangering the public or airpcraft, such as the FAA rules about balloons Turtle mentions. But, to the best of my knowledge, there’s no rule, against filling a balloon with hydrogen, or even something really dangerous, like straight natural gas or coal gas.

What happens when lightning strikes your balloon? What material is your tether?

I understand that getting a current from a balloon to the ground via a tether can be very bad news. How to keep a tether of any material from becoming conductive when covered in rainwater strikes me as challenging.

 

However, a spark in a bag of fairly pure hydrogen isn’t dangerous, because without oxygen, hydrogen gas can’t burn. So, as long as you can keep its hydrogen from getting too contaminated, or having a major leak, a hydrogen balloon’s pretty safe. A major puncture and a spark, though, and you’ve got a potential repeat of the Hindenburg disaster. It’s worth noting, though, that there’s a lot less heat in a burning hydrogen balloon than in a fire in a typical structure of the same size, because there’s so little mass in a volume of near-atmosphere-pressure hydrogen (about [math]0.09 \,\mbox{kg/m}^3[/math]). So a 5000 m^3 hydrogen balloon has only about 500 kg of hydrogen in it, equivalent in energy content to about 40 gallons of gasoline (source: wikipedia table “Energy density in energy storage and in fuel”).

 

Despite the popular misconception of it as an unsurvivable explosion, recall that only 35 of the Hindenburg’s 97 passengers and crew, and one of the ground crew, were killed, and most of them from falling, not burning. Hydrogen’s reputation as a dangerous gas is somewhat unjustified.

[Turtle]

Without going into details, some of your concerns are valid and some are not, although there is no way for you to know that without having seen the designs.

 

I can't evaluate the plans for you if'n ya don't show 'em.

 

Conductivity and lightning is an issue.

Static should not normally be an issue as there will not be a ground for it.

Static is an issue because if there is no ground it will continue to build up until it finds a discharge route. If there is a ground, then you might have a steady discharge; something else to add to your electric generation. ;)

 

Deformation and instability have been accounted for and are actually not an issue. Some of the expected deformations are even quite helpful.

Can you share those details?

 

Lift and tension from drag are cumulative with the largest value (a considerable amount actually) near the ground. The design leverages this to prevent "folding" and "deforming" issues.

It is not going to be steady, i.e. it's going to jerk around, go slack, dance, etcetera. Does your generator design account for this?

 

Lightning.. .Hmm..

:hihi: No! :naughty: Not reliable/regular enough of an occurance and you would need an enormous capacitor to capture it. We have some threads here somewhere discussing this. :naughty:

 

There are laws and regulations about not endangering the public or airpcraft, such as the FAA rules about balloons Turtle mentions. But, to the best of my knowledge, there’s no rule, against filling a balloon with hydrogen, or even something really dangerous, like straight natural gas or coal gas.

I think a check with the fire departments and their codes might be in order as well as or instead of the FAA. If y'all think it's OK, then how about sending up a Hydrogen balloon and igniting it on purpose for special effects/entertainment purpose?

What happens when lightning strikes your balloon? What material is your tether?

 

I understand that getting a current from a balloon to the ground via a tether can be very bad news. How to keep a tether of any material from becoming conductive when covered in rainwater strikes me as challenging.

 

The only regular tethtered balloons coming to mind are the barage balloons* of WWII; maybe there is some info out there on how they operated and dealt with the electricity/lightning issue. In spite of the jolly homespun colloquaial story of ol' Ben & his kite, messing with a wet kite or ballooon line is asking to get fried and or fry other people or their property.

 

*

...Disadvantages

Balloons were sometimes more trouble than they were worth. In 1942 Canadian and American forces began joint operations to protect the sensitive locks and shipping channel at Sault Ste. Marie along their common border among the Great Lakes against possible air attack.[3] During severe storms in August and October of 1942 some barrage balloons broke loose, and the trailing cables short-circuited power lines, ...

 

However, a spark in a bag of fairly pure hydrogen isn’t dangerous, because without oxygen, hydrogen gas can’t burn. So, as long as you can keep its hydrogen from getting too contaminated, or having a major leak, a hydrogen balloon’s pretty safe. A major puncture and a spark, though, and you’ve got a potential repeat of the Hindenburg disaster. It’s worth noting, though, that there’s a lot less heat in a burning hydrogen balloon than in a fire in a typical structure of the same size, because there’s so little mass in a volume of near-atmosphere-pressure hydrogen (about ). So a 5000 m^3 hydrogen balloon has only about 500 kg of hydrogen in it, equivalent in energy content to about 40 gallons of gasoline.

 

Wow! That would be one kewl fireball on or off the ground! Let's do it! :ebomb: :doh:

 

Anyway, this all seems to have it's most practical use in producing fun. :hihi:

[Turtle]

:hihi: Can't get this pressure outa my mind! :naughty: :naughty:

 

What we need here is a hybrid balloon and kite, and as luck has it there is a name for that. Well, a commercial product name anyway. >> Birdscaring devices, Aerostats, barrage ballons, bird control equipment, sky-hooks, tethered VAV's for science

 

Wiki article on helikites: >> Helikite - Wikipedia, the free encyclopedia

 

Wiki article on moored balloons: >> Moored balloon - Wikipedia, the free encyclopedia

 

So we combine your balloon idea for power with LauriG's and my ideas for kite power, by using a helikite to make power. Rather than those helikite designs from the above link, I suggest a delta wing shape with aileron/elevator flaps to control descent and ascent. Basically you put the thing into a dive in a wind which then pushes it down.

 

One other thing is that one way or the other, there is a need of a power reel/winch to recover the line while the aerostat is descending. To the bat cave! :ebomb:

[Kayra]

LOL, Thanks Turtle, always entertaining :naughty: I had no designs on harnessing lightning, just trying to bring the conversation and thoughts back around to the problem.

 

No I can not give more details yet, and I was originally asking about the viability of the lift control system, not the concepts in general :naughty:

 

Static dissipates and is not a concern in this design.

 

The actual tether is never exposed, but the container for it IS :hihi: and will provide just as handy a path for the lightning when wet

 

The Kite idea is interesting (I remember the thread) but not compatible with what I have in mind. It would only add needless complexity.

 

The design deals with gusts likely up to 10 seconds in duration and will smooth out longer ones.

 

CraigD, I was hoping the outer envelope would provide exactly the protection against sparks you mentioned. This is not one giant balloon but a segmented construct, so not all the gas would be at risk at once.

 

 

At this point can I confirm that nobody responding has seen any major flaws with the lift control system?

[Turtle]

LOL, Thanks Turtle, always entertaining I had no designs on harnessing lightning, just trying to bring the conversation and thoughts back around to the problem.

 

:hihi: What? Me go off on a tangent? :hihi: You are too kind. :ebomb:

 

At this point can I confirm that nobody responding has seen any major flaws with the lift control system?

Other than fire :naughty:, no major flaws in theory no. The Devil is in the details now. In general, I think the whole business is going to weigh too much by the time it's rugged enough, to get any appreciable work done. When's the first test flight anyway? :naughty:

[Kayra]

Weight is a surprisingly smaller issue then I had first imagined it would be, as to ruggedness, that remains to be seen :0

 

Way to soon to even decide if it will fly at all. I am still building prototypes of some of the more stressed parts and breaking them (what fun). Assuming this goes well, I should have a prototype up in 6 weeks after the IPO is filed.

 

Due to the cost, I am not willing to file an IPO until I confirm to my own satisfaction the concept will.. ah.. fly :phones:

[Kayra]

This lightning issue is really bothering me. I would hate to have to use the lift control system every time a puffy cloud appears on the horizon :phones:

 

Do you guys think a highly water repellant coating would help break up the water enough to ensure there was no contiguous conductive coating? Would that even help?

 

Is it possible to run a wire along the entire length, sense impending possible strikes, and create a strong enough static field to discourage the lightning leader (not the bolt itself) from using the structure as a path to ground?

 

Any other suggestions out there?

[Turtle]

This lightning issue is really bothering me. I would hate to have to use the lift control system every time a puffy cloud appears on the horizon :phones:

 

Do you guys think a highly water repellant coating would help break up the water enough to ensure there was no contiguous conductive coating? Would that even help?

 

Is it possible to run a wire along the entire length, sense impending possible strikes, and create a strong enough static field to discourage the lightning leader (not the bolt itself) from using the structure as a path to ground?

 

Any other suggestions out there?

 

I see no way around it, and lack of clouds is no guarantee of no lightning. Ground your equipment, use a lightning arrestor* and arrange for whatever remote control is necessary to keep you out of direct conduct with said equipment.

 

*

Lightning arresters, also called surge protectors, are devices that are connected between each electrical conductor in a power and communications systems and the Earth. These provide a short circuit to the ground that is interrupted by a non-conductor, over which lightning jumps. Its purpose is to limit the rise in voltage when a communications or power line is struck by lightning. ...

Lightning rod - Wikipedia, the free encyclopedia

[Kayra]

A series of inexpensive disposable kites and a conductive monomer perhaps?

 

Hmm...

I might just have to resurrect your kite idea after all and pull a Ben Franklin.

 

I do not need to make the lightning stay away from the generator, I need to encourage it to go elsewhere.

 

A series of inexpensive disposable kites and a conductive monomer perhaps?

 

Placed strategically around the area and triggered to auto launch after one goes down might do the trick.

 

I will have to think on this. Thanks Turtle.

[Turtle]

A series of inexpensive disposable kites and a conductive monomer perhaps?

 

Hmm...

I might just have to resurrect your kite idea after all and pull a Ben Franklin.

 

I do not need to make the lightning stay away from the generator, I need to encourage it to go elsewhere.

 

A series of inexpensive disposable kites and a conductive monomer perhaps?

 

Placed strategically around the area and triggered to auto launch after one goes down might do the trick.

 

I will have to think on this. Thanks Turtle.

 

There is a guy named Art Bell down in Nevada that is a radio ham and he put up one of the largest amateur radio antennas anyone has. It's 100 feet up on towers and at least 1,000 feet long. (Will look for a link...) Anyway, he was reporting that he had a current coming off it & was having to take measures to isolate his radios from it. He also mentioned he was going to look into making some use of the current , but I have not heard anything further on it in quite a while.

 

Still not knowing your exact secret plans, I think a hybrid kite/balloon would be way cool and practical too. Deploying more than one gets problematic, as the higher you go, the wider spaced you need the anchor points to minimize/prevent tangling. One of my favorite movie scenes ever is when what's his name launches that pop-out kite from a canon on his ship in Waterworld. Too kewl!!!:doh:

 

A commercial lightning arrestor attached to the line should work. >> Delta Lightning Arrestors Home Page

 

If'n you do want a conductive line, then by all means go with thin steel cable. I don't know how conductive Kevlar is wet or dry, but a lot of the stunt-kiters fly with it.

 

That's all from the turtle's shell for now. ;)

[Turtle]

There is a guy named Art Bell down in Nevada that is a radio ham and he put up one of the largest amateur radio antennas anyone has. It's 100 feet up on towers and at least 1,000 feet long. (Will look for a link...) :doh:

 

Here we go thens: >> Art Bell's antenna - Google Search

 

The Art Bell W6OBB Loop Antenna Slideshow 2005

 

So using hybrid kite-balloons, you tether them with a wire inside a vinyl tube sheath. You collect your juice from the wire, and pump your Nitrogen through the tube to vary the altitude. (You could rig the kite to change angle of attack when the inner bag deflates; kill two birds with one stone, to quote a phrase. )

 

Speaking of which, if I saw this thing flying nearby, I very well might try to shoot it down. ;)

Something to keep in mind out there, as I rather imagine I'm not unique in that regard. :D:doh: :hihi:

[Kayra]

Thanks for the Info Turtle. Quite interesting considering my background. We (the Canadian military) had an antenna farm in Germany in the ULF range and it was also picking up a constant current. Pretty cool when your radio waves hug the earth and cross the Atlantic though. Not a hell of a lot of bandwidth down there unfortunately. (Morse code anyone?)

 

To be clear, I did not want the lightning anywhere near the LTA system. I was of a mind to deploy inexpensive disposable kites around the perimeter of the wind farm and fly them higher then anything else around.

 

As for pumping the Nitrogen, as it is slightly lower density then air it is naturally buoyant, saving a considerable amount of pumping energy.

[Turtle]

Thanks for the Info Turtle. Quite interesting considering my background. We (the Canadian military) had an antenna farm in Germany in the ULF range and it was also picking up a constant current. Pretty cool when your radio waves hug the earth and cross the Atlantic though. Not a hell of a lot of bandwidth down there unfortunately. (Morse code anyone?)

 

To be clear, I did not want the lightning anywhere near the LTA system. I was of a mind to deploy inexpensive disposable kites around the perimeter of the wind farm and fly them higher then anything else around.

 

As for pumping the Nitrogen, as it is slightly lower density then air it is naturally buoyant, saving a considerable amount of pumping energy.

 

Oooooo....boots from the ground; my favorite resource. What was the voltage/current off that antenna? Did you have to get rid of it somehow? How long was the antenna, and do you think length is important to having that voltage develop at all? Was it AC or DC current?

 

Supposing we want to fly a 1,000 foot antenna, could we fold it 4 times and fly at 250 feet and get the same effect do you think?

 

Roger on the decoy kites; very clever. Not sure it would work as lightning has a mind of its own, but very clever all the same.

 

You never responded to my suggestion to just pump the Hydrogen in and out of the balloon to vary height, and forget the Nitrogen double-bag arrangement. If you're not worried about fire, and you already plan to run a tube up (or as) the tether, it strikes me as much simpler and lighter.

 

Must break for coffee. :naughty:

[Kayra]

No details on the antenna. I was drinking buddies with the techs. I myself was more the fire control/IFF/ECM guy on the aircraft. They did have some interesting stories to tell come Friday evening though :naughty:

 

I thought I had responded to your suggestion, sorry.

Fire suppression is an important aspect of this system, hence the inert gas and fire retardant envelope surrounding the bladder. I needed a multi-layered material anyway. inside laminate had to stop the gas (much as it could) and the outside had to be tough and UV impervious. The inside bladder is quite light.

 

By separating those 2 layers and adding another gas impervious coating to the inside of the external envelope the weight impact is almost negligible compared to the rest of the structure. The other advantage (I hope) is that with external pressure, the very thin gas bladder will not be stressed by internal pressure and therefore last longer.

[Turtle]

No details on the antenna. I was drinking buddies with the techs. I myself was more the fire control/IFF/ECM guy on the aircraft. They did have some interesting stories to tell come Friday evening though :lol:

 

I thought I had responded to your suggestion, sorry.

Fire suppression is an important aspect of this system, hence the inert gas and fire retardant envelope surrounding the bladder. I needed a multi-layered material anyway. inside laminate had to stop the gas (much as it could) and the outside had to be tough and UV impervious. The inside bladder is quite light.

 

By separating those 2 layers and adding another gas impervious coating to the inside of the external envelope the weight impact is almost negligible compared to the rest of the structure. The other advantage (I hope) is that with external pressure, the very thin gas bladder will not be stressed by internal pressure and therefore last longer.

 

First, roger secret info. :( Now....

 

Dude!!! (and other Dudes & Dudettes! :confused: :naughty:)

 

I just found the most amazing balloon resource!!! Looky here! Looky here! :eek2:

 

Lift of Hydrogen Balloons

 

Dia. Ft. Vol. l Lift gr. Lift Lbs.

 

1 14.83 16.5 0.04

2 118.62 132.3 0.29

3 400.34 446.4 0.98

4 948.96 1058.1 2.33

5 1853.45 2066.6 4.56

6 3202.76 3571.1 7.87

7 5085.86 5670.8 12.50

8 7591.72 8464.8 18.66

9 10809.30 12052.5 26.57

10 14827.58 16532.9 36.45

11 19735.50 22005.3 48.51

12 25622.05 28568.8 62.98

13 32576.18 36322.7 80.08

14 40686.87 45366.2 100.02

15 50043.07 55798.5 123.02

16 60733.75 67718.7 149.29

17 72847.88 81226.0 179.07

18 86474.42 96419.8 212.57

19 101702.3 113399.0 250.00

20 118620.6 132263.0 291.59

21 137318.2 153111.0 337.55

22 157884.0 176042.1 388.11

23 180407.1 201155.5 443.47

24 204976.4 228550.5 503.87

 

>> Balloon Lift

 

That's just for starters. Everything you want to know about materials, design, other gases, etcetera. Spectacular!! A party for your brain. There is even a section on the weight of different types of wire for lofting antennas!! Almost more than an ol' turtle can stand. :hyper: Enjoy! :hyper: