Need a material that can hold Helium....

[Pat Trainor]

Experts,

I'm in need of a balloon to hold an RF antenna aloft, and that can have a light (LED) in it. For cost & safety, it appears Helium is the choice. But everything I'm reading says that He atoms are so tiny they pass (eventually) through traditional balloon materials quickly. There is a cheap mylar-metal (aluminum?) material used in cheap party balloons, but I need something a bit more rugged.

Without consideration for the weight of the enclosing material, I'll be using a balloon at about 3' to 5' diameter, but the interior really needs to be lit. So the need is materials that are transparent/translucent and yet able to contain He for a relatively long period. I'm talking 72 hours or so with really little loss-much better than your party balloons do...

Hoping that this is a good generic forum to ask, are there materials I can make a spherical balloon from as-is, or perhaps some combination, or layers?

Thanks!

 

[anorlunda]

Google "helium permeability"

Also
http://geojournalism.org/2013/08/balloon-mapping-how-to-make-your-own-low-flying-satellite/
and
http://www.dtic.mil/dtic/tr/fulltext/u2/621959.pdf

Depending on where you live, and how high the balloon will be, you may need permits from the city and the FAA.

If just 72 hours, then it might be easier to just oversize the balloon and not worry about leakage.

 

[berkeman]

But everything I'm reading says that He atoms are so tiny they pass (eventually) through traditional balloon materials quickly.

Maybe one possibility would be to attach a small He canister to the balloon assembly, and have a simple electromechanical circuit that can maintain the He volume over the duration of the flight. You'd need to calculate the additional size of the balloon needed to support the extra weight, and see if it was worth it to have the on-board replenishment process to extend the flight time. A canister about this size...

https://www.luftballons.biz/en/balloons-helium-kits/metallic-balloons-helium-small-bottles-disposable-mini-helium/balloons-mixed-metallic-colors-disposable-mini-helium-cylinder

https://www.luftballons.biz/media/images/org/mini-ballons-helium-sets-metallic-bunt.jpg

 

[anorlunda]

Conventional weather balloons are translucent, and inexpensive. One more thing, check about FCC licenses for the transmitter. Also, if the LED light is to warn off airplanes, the FAA has minimum brightness requirements and color requirements, I think red and 2 mile visibility is the minimum. That might be easier to achieve with a light that is outside the balloon, and also it makes your transparent/transluscent requirement go away.

 

[berkeman]

Conventional weather balloons

What are they using to inflate the balloon in that picture? Looks like a leaf blower, but that can't be right. Is it some He canister attachment?

 

[anorlunda]

What are they using to inflate the balloon in that picture? Looks like a leaf blower, but that can't be right. Is it some He canister attachment?

I have no idea. I just searched for a photo of a translucent weather balloon. Maybe someone staged that photo for demo purposes.

 

[rbelli1]

Looks like a leaf blower, but that can't be right. Is it some He canister attachment?

If that balloon was filled with helium it would not be nearly spherical. The buoyancy would cause an upside down teardrop shape.

BoB