Saturday, November 27, 2010

GAGA-1: Capsule insulation and antenna mounting

A bit of physical stuff on GAGA-1 this weekend after the Recovery Computer software last time. I'd previously painted the capsule for high visibility, but hadn't started cutting it or sticking on parts. After the successful test of the Recovery Computer it's time to put some bits on the box!

The three antennae visible on the box (as with the other components) are hot glued in place. I pierced holes in the box using a long metal skewer and a chop stick.

Here's a close up of the top of the capsule.

The top two antennae are for the two GPS modules (one in the Flight Computer and the other in the Recovery Computer). The long thin antenna is for the GSM connection that's part of the Recovery Computer.

The other two parts are a small red straw and a large black straw. The small red straw is simply there to allow the pressure to equalize between the inside and the outside of the capsule. Since the pressure is very low in the stratosphere it would be dangerous to send the box up completely sealed.

The black straw is sealed at the end with hot glue and will be where the external temperature sensor is placed.

I've further insulated the box by lining the interior with sheets of space blanket. This reflects almost all the heat generated inside the box (by the electronics) and should help keep things warm.

This was very fiddly to do as the space blanket material is very thin. I cut sheets out using a stencil and glued them in place. Placing my hand in the box I can feel warmth: the reflected warmth of my own hand.

Finally, here's an interior shot of the lid of the capsule showing where the cables for the antennae and straws poke through.


Ed said...

Greetings John.

Although the insulation on the inner surface of the lid will help this somewhat anyway, you may improve the GPS signal to noise ratio reaching the antennas by placing a strip of foil directly underneath them to act as a ground plane. It is especially helpful to have them shielded from the relatively high strength EMI sources inside the box, like the telit module.

Whilst the antennas can see plenty of sky, the GPS engine's state estimators tend to have a strong prior on you being at ground level, so you really do need a good SNR to give more confidence to the observation.

All looking good!


Ed said...
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