Robert

Hi All,

I'm in the process of launching a balloon into the stratosphere (CAA approval is in place) to initially take pictures of the UK. However due to wind there is a good chance that my camera may head towards the sea. This is bad news for the camera and my project. What I would like to be able to do is cut down the payload from the balloon using a pyrotechnic device and this is where you all come in.

The balloon is connected to the payload (box) by one piece of kite string about 2 meters above the flight box. I would like to burn though this string using a pyrotechnic ignited by a processor controlled switch. The problems are:

1) There is very low oxygen content at ~35000m
2) I have very limited power to supply to the ignition system 4xAAA or the
equivalent in weight perhaps a lipo from the local model shop
3) The external temperature is ~ -60 deg C (The payload box internal temp is ~0 deg C)
4) The burning has to be contained so as to not affect the parachute


My initial idea is a cardboard tube with a string running through the middle of it. Using a davysfire (electric match) to ignite some slow burning fuse wrapped around the string in the middle. I'm assuming that a davysfire (if that's what they're called) can be ignited with such low power supply and that it will be enough to ignite the fuse at such low temperatures and oxygen content.

Does any one out there have any useful suggestions or comments.


Many thanks

Robert