Mission SammyOne

Helium and Filling Mechanism

2010

 
 

The principle of the balloon filled with Helium is this:


  1. Fill the balloon with Helium until it has a recommended free lift

  2. Launch the balloon

  3. As the air gets thinner, the balloon expands

  4. The balloon gets bigger and bigger until it bursts

  5. The balloon returns to Terra Firma


The manufacturer of the balloon recommends a 5 m/s ascent rate for the balloon. For that it needs to have a free lift of 1190 grams. If you put too much Helium in the balloon, it will go up much faster but will burst much sooner, not getting to altitude. If you put not enough Helium into the balloon, it will not go up at all or go up just fine but will keep on floating for hours as it takes a lot longer to get to bursting altitude.


I made a spreadsheet to calculate the amount of helium I would need, given the weight of the balloon, the payload and the lift the balloon would need to achieve an ascent rate of 5 meter per second. I found out that 1 liter of Helium would lift about 1 gram. This meant that I needed more than 3500 liters of Helium!


Helium is very expensive and I searched the web for days to find the best Helium deal. I bought two cylinders of 5000 liters each. One for the main balloon, the other for the reserve balloon (hopefully not needed). This should be enough to fill the balloons and do some funny voice experiments.


The cylinders did not come with any pressure valve or fill mechanism. This is where my growing DIY skills came into place, again. I used 30mm PVC plumbing pipe, an air hose, some glue, silicone and tape to create a 90 degrees, 30mm filling mechanism. A Perfect airtight fit for the balloon!


The pressure valves were way too expensive for one time use, so I skipped that and decided to "fiddle around" with the open/close valve. This meant that I had to be very, very careful as the full pressure from the Helium would shear the balloon into pieces.


It also meant that I could not measure the amount of Helium that goes into the balloon. But no problem, I just filled a bucket with stones until it weighed the same as the payload and the free lift necessary to achieve 5m/s ascent rate. When the balloon is just able to lift that bucket it would be good to fly the capsule at a 5m/s ascent rate!


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Helium and Filling Mechanism

Jurgen, Jan and myself in action, closing the balloon. See the self-made “high tech” filling mechanism in action! The string underneath the filler is connected to the bucket with stones. Being able to lift the the bucket would mean 5m/s ascent rate.