Saturday, January 14, 2012

GAGA-2: Mounting the flight computer

On GAGA-1 the flight computer was screwed in place using nylon bolts that went through the polystyrene walls of the capsule. GAGA-2 is using cable ties.

One concern with cable ties is their performance at low temperature. The CUSF guys had warned me never to use cable ties for load bearing joints. But since we are holding in place a few grams of flight computer the only remaining concern was whether the cable ties would still be locked at low temperature.

So, I locked together a pair of ties and left them in the freezer at -18C overnight.

The next morning they showed no signs of slippage and I was unable to pull them apart. But for double safety I've also superglued the locking part of the cable ties shut in place.

Here's the flight computer inside the capsule:

There are a pair of cable ties around the two board of the flight computer (the Arduino and the custom shield on top containing the radio transmitter and the GPS). Those help keep them together.

Then there are a pair of cable ties that pass through the wall of the inner capsule. Those cable ties are hot glued in place so there are no holes and so they don't move.

Finally the two sets of cable ties are interleaved so that the board is held in place. Once everything is tightened I dropped superglue in all the locking parts. The computer is positioned so that there's no stress on the rather short cable to the GPS antenna.

It doesn't move and I'm pretty happy that it'll stay in place during the flight. The next thing that needs mounting securely is the battery. On GAGA-1 the batteries popped out on landing; I'm not letting that happen this time.

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