■ FIGURE 8. The airframe has been wrapped in black tape.
The holes in the tape are cut with an Exacto knife.
However, I find that a hot soldering iron or hot Styrofoam
knife is better for melting clean, small holes in the tape.
The sensor array is hot-glued to the top of the airframe.
thick foam. The battery box was placed far enough from
the front that it wouldn’t interfere with attaching the video
As you might begin to see, in this BalloonSat design I
will connect the flight computer to the nine volt battery
and then turn on the digital camera. Afterwards, I can start
up the camcorder and close the hatch.
Now, it was time to attach the top deck. The weather
sensors would be placed on the top, where their
orientation (with respect to the sun) doesn’t change
significantly. If they are attached to the side of the
airframe, the balloon’s rotation would carry them in and
out of the sun — perhaps affect their readings. The sensors
I selected were an LM335 temperature sensor and a
Honeywell HIH-4000 relative humidity sensor. Since both
react to sunlight shining on them, I placed a white plastic
lid over the sensors. The lid’s rim was drilled with a series
of holes that are designed to let the air flow in. However,
the holes are small enough that no significant amount of
sunlight can shine on the sensors inside. After gluing the
top to the airframe, I marked the location of the plastic lid
and cut a slot to allow the sensor’s cable to pass into the
The results of a near space experiment that I
performed years ago led me to believe that the interior of
a BalloonSat airframe remains warmer if its exterior is
colored black. Since the airframe material is Styrofoam, I
use colored packing tape to add color to the BalloonSat.
This tape is popular for covering Styrofoam gliders (in
place of painting them). The tape is also used to seal and
■ FIGURE 6. The battery box. By sliding the battery into
this opened box, it's kept from bouncing
all around inside the airframe.
label packages in preparation for mailing. You can find it
at Uline ( www.uline.com) as item S-700. Another benefit
of using the tape is that by wrapping it around the outside
of the airframe, it creates compression that helps hold
■ FIGURE 9. Everything but the hatch is ready. The cameras
are bolted into the airframe as is the white plastic lid on top.
July 2012 71