Show that foil balloons can float at altitude. Previous pico flights have shown that you can carry out low altitude flights with foil balloons however each time one balloon has burst resulting in descent. The current thinking is that the reason we havent' previously achieved float is that the balloons have had too much lift, they reach burst altitude before float altitude. For this flight the aim is to carefully get a slow ascent rate of approximately 0.5m/s.

• Arduino168
• Ublox5 GPS with patch antenna
• Radiometrix NTX2 434.075Mhz
• 2xAA
• Built on stripboard

Total mass = 87g (inc antenna + insulation)

• Filling was undertaken in a closed barn, to reduce any wind.
• As we were going to add ballast to get the target ascent rate we filled one balloon first, made sure it could lift 25g (1/4 of payload mass + a little bit more), we over filled slightly.
• We measured the total lift of the first balloon and then aimed to get each balloon to lift that much. It was easy to add He but we didn't attempt to empty out He as we feared it might push out the internal seal.
• Once we had all the balloons filled we then measured the ascent rate and added further mass until we had roughly 0.5m/s.
• Bluetack is a good material to add and subtract mass. We found that it needed a further 44g of ballast and so added a small bottle and some water which had a total mass of 44g.
• Once everything was filled we just waited for the rain to stop - being in the barn meant that the balloons were safe.
• For launch we just too everything outside and released it.

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