■ FIGURE 11. The red string on the right side of the
BalloonSat is the flight computer's commit pin. It permits
me to connect the battery to the flight computer ahead of
time, but won't let it begin recording data. That is, until I
pull out the pin.
■ FIGURE 13. The air temperature as a function of
altitude. The increasing temperature above 50,000 feet
indicates that this is the altitude where the stratosphere
■ FIGURE 14.You can see we passed through a cloud layer
at about 8,000 feet. The rest of the flight is very dry.
■ FIGURE 12. A side view of the BalloonSat airframe.
The hatch is on the left side. You can see there's a
small opening in the airframe for the commit pin
cable to hang out of.
The downward-looking camera only bolts to the
airframe at one point. This turned out to be a problem,
since I left clear space around the camera so it could
easily slide in and out of the lower bay. Without a tighter
fit, the camera is liable to twist against the airframe during
the chaotic descent and crack the foam airframe. Just in
case, I took up the slack and added gentle pressure to the
camera by sliding a sheet of thick foam latex to the top of
the bottom bay.
The next step was the construction of the BalloonSat
hatch. The hatch is a 10 millimeter thick sheet of Cellfoam
88 that sits on the surface of the opened airframe.
However, I wanted to keep the hatch from sliding around.
So, I cut rectangles out of five millimeter thick Cellfoam
88 that fit between the decks of the BalloonSat. These
were then strategically hot-glued to the inside of the hatch.
Now, the hatch snaps into place on the airframe, but the
rectangles keep it from twisting or sliding around. The
position of the video camera’s lens was measured and I
cut a hole in the hatch to match. Finally, the hatch was
given a coat of black tape.
I made one change to the airframe after its assembly. I
wanted a simple way to hold the hatch closed, so I cut a
channel in the back of the airframe and glued a square
tube into it. The tube was about seven inches long, so it
extends a 1/2 inch beyond both sides of the airframe. That
square tube stands out like a sore thumb in the back of
the airframe, therefore, I covered the construction site
over with a strip of black sealing tape. To lock the hatch, I