Focusing on balloons

A project log for Low altitude flying electronics

Sending electronic devices in the air for cheap.

miawtthiasmiawtthias 04/21/2016 at 19:5010 Comments

It's been a long time since my last log. Thank you to all the people that liked and followed the project.

Kite design is way more complicated than what I anticipated. There's a lot of ressources on the web and a decent kite usually mean a bigger budget than what I had in mind when I started this project. So I think I'll focus on the balloons for now.

I already know that I'll need multiple balloons but I still haven't determined how I'm going to produce the hydrogen. The first option is to use electrolysis.

Pros : I've done it in the past and there's a lot of documentation on it.

Cons : It's a slow process. It needs a power source so it's not portable. It means that you'll have to produce it at home first, then take it with you and I don't really like the idea of moving around a big quantity of flammable gas. Finally it's kind of power hungry so not a very cheap solution.

Second option is to use a chemical reaction. For example : when iron reacts with hydrochloric acid, hydrogen gas is produced. It's quick if the contact area is big (you can use iron powder for example). It can be done anywhere if you bring the chemicals with you. The chemicals are quite cheap and easilly available. The only problem that I can think of is to find a way to stop the reaction once you've produced enough so that you don't waste chemicals and produce more hydrogen that could cause a fire hazard.

I've already got some ideas on how I'm going to solve this problem so I think I'll go whith the second option. If you can think of any other option please comment !


flashcactus wrote 04/22/2016 at 00:03 point

protip: trash bags are prime large-thinfilm-balloon material.

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miawtthias wrote 04/22/2016 at 08:22 point

I didn't think of trashbags, I'll definitely try this option. Thanks !

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flashcactus wrote 04/22/2016 at 00:02 point

In any case, have you considered using helium? It is not that expensive actually, a 10L bottle cost me less than an arduino, and it's enough to fill about 10 large balloons (or more, I haven't counted). And those are regular big balloons; if you use lighter ones, like meteorologicals or thin-film ones, the lift should be even better.

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miawtthias wrote 04/22/2016 at 08:22 point

I've considered using helium but I think it wouldn't be a fun challenge for me anymore. I really want this project to be easy to replicate even in countries where helium is not readilly available.

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flashcactus wrote 04/22/2016 at 08:38 point

from my experience, obtaining aggressive chemicals might be even harder than inert stuff like helium, with all kinds of strange regulations in the way. In any case, replacing the gas with helium would be trivial if you do the rest of the work. Good luck :)

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flashcactus wrote 04/21/2016 at 23:58 point

re: stopping the reaction. The classic way to do this is to use special glassware for the reaction. It basically consists of two vessels joined at the bottom. Vessel A has its top hermetically sealed, with the exception of a gas-output valve. In the lower 2/3rds of A is a net on which the metal lies. Vessel B has an open top. The system is about half-filled with acid. In gas production mode, the valve is open and the acid is in contact with the metal. When you want to stop, you close the valve. The excess pressure hydrogen forces the acid out of vessel A into vessel B until the acid is no longer in contact with the metal.

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miawtthias wrote 04/22/2016 at 08:21 point

I've never heard of this special glassware. Do you have a picture of it ? If it's as I think it might not be to difficult to replicate except maybe for the net.

Thanks a lot for your comments !

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flashcactus wrote 04/22/2016 at 08:34 point

The site won't let me paste anything :( But some clever googling gave me its name: It's called Kipp's Apparatus.

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miawtthias wrote 04/22/2016 at 09:06 point

Kipp's Apparatus is cool but it might be difficult to build a airtight container (at least with my skill level) in this configuration. I've came across a Döbereiner's lamp configuration that looks easier but won't work with iron powder. I think I need to try producing hydrogen with like iron bars or plates to see if it's good enough for the quantities that I need.

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flashcactus wrote 04/22/2016 at 09:09 point

The classic configuration is indeed quite unwieldy. But think two large plastic bottles with a rubber hose between them, the gas-output tube sticking through the lid of one of them, all sealed with hot glue. That should be doable. By the way,instead of the net/mesh you could have some kind of fabric bag hanging off of said lid, simplifying insertion/extraction.

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