Figure 7. Notice the black colored cube cooled faster than the silver one.
Next, I loaded two BalloonSats
inside my Thermal Test Chamber
(TTC) for testing. The first test
compared the internal temperature
differences between a BalloonSat
wrapped in aluminum tape (the
traditional material) and one
wrapped in a thin black plastic
packaging tape (the kind of tape
used to wrap Styrofoam gliders).
The second thermal test compared
the internal temperatures between
BalloonSats wrapped in a traditional
aluminum tape and one wrapped in
aluminized space blanket.
Initially, I was a bit surprised by
the chart in Figure 7 until I recalled
something my father had told me.
A material painted black absorbs
radiation well and reflects very little
of it. However, if a black colored
body can absorb radiation well, it
can also emit it well. I was told this is
why the radar antennas on aircraft
carriers are painted black and not in
white or silver.
Have you wondered why potatoes are wrapped in aluminum foil
before being baked in the oven?
While the aluminum foil reflects a lot
Figure 8. Chart comparing the old design to the new design.
NUTS & VOLTS
of the infrared radiation emitted
by the oven’s heating coils, what
radiation does get in, stays in, and
can’t get out. The potato cooks
faster as a result.
In the second test, I hoped to see
that reducing the amount of metal
on the outside of the BalloonSat
would reduce the rate at which it
cooled. In the chart in Figure 8 you
can see that the results are pretty
much a wash. There’s no significant
difference in the rate at which the
two cubes cooled.
However, the BalloonSat wrapped
in space blanket is lighter in weight
than the traditional BalloonSat
wrapped in aluminum tape. Anything
that reduces the weight of the
airframe helps meet the weight
criteria and permits an increase in
Here’s my conclusion on
airframe materials and insulation.
The five inch cubic foamcore
BalloonSat weighs 58 grams initially
and 82 grams once it’s wrapped in a
single layer of aluminum tape. The
same size Styrofoam BalloonSat
only weighs a total of 58 grams with
a space blanket exterior and stays
just as warm.
Now if your BalloonSat is not
using space blanket, then I recommend using Styrofoam tape in place
of the aluminum tape. I’m referring
to the tape hobbyists use to wrap the
surfaces of their Styrofoam gliders.
It comes in multiple colors and is
Use a dark colored tape because
my past near space experiments
have demonstrated that dark colors
on the exterior of a near spacecraft
keep it warmer. See my article,
Keeping Near Spacecraft Warm, in
the Fall 2004 issue of Amateur
Television Quarterly. (Contact the
editor, Gene Harlan, at ATVQ@www.
hampubs.com to get a copy.)
The closure on most BalloonSats
is either tape or Velcro. My suggestion is to change to rubber bands.