Near Space
Figure 2. I spent two hours hiking up this snowy
mountain to get the mission back. In places, the
snow was five feet deep.
time learning how to launch (
program) and readout data from the
Hobo. The Hobos used in a
BalloonSat have an internal temperature sensor, so to measure the
external temperature, students use
either a temperature sensor from
OnSet or make their own (see my
column in the August 2004 issue of
Nuts & Volts, page 84).
A popular device carried
onboard the BalloonSat is the Canon
Elph APS Camera. The Elph camera
is reasonably inexpensive and easily
modified for use with an
automatic timer (
consisting of a simple 555 timer
circuit and transistor
switch). The camera may
have already been modified when students get it,
but that still leaves construction and adjustment
of the camera’s 555 timer
circuit for them to do. My
November 2004 (page 94)
and March 2005 (page 80)
columns have information
on modifying cameras for
near space use.
After constructing
their BalloonSat, the team
must evaluate the performance of
their BalloonSat with a series of four
tests. First is the weight test. Each
fully loaded BalloonSat (this
includes film and batteries) is
weighed. The Colorado Space Grant
BalloonSats can weigh no more
than 500 grams and Idaho high
school students are limited to
400 grams.
The functional test is next.
Each BalloonSat must remain
attached to the flight string (and not
cut it) without suffering damage
under normal flight conditions.
Each BalloonSat must also show
that it will collect data for the
expected flight time.
The third test is my favorite.
The BalloonSat must function
under the cold conditions expected
during the flight. Each BalloonSat is
placed inside a thermal chamber
loaded with dry ice where it must
record data for 20 minutes. The
final test is the drop test. Here, each
BalloonSat must survive a ground
impact at speeds expected during
recovery. The BalloonSat is
dropped from a specified height
and must remain in one piece and
continue functioning.
If the BalloonSat passes these
tests, the team calls it a day and gets
some sleep. In the morning, the
BalloonSat team meets at the
launch site where an amateur near
space group has agreed to carry
their BalloonSat into near space.
Remember, the BalloonSat doesn’t
carry tracking equipment, so the
BalloonSat must piggyback with a
near spacecraft.
Some of My
BalloonSat Flights
Figure 3. BalloonSats.
Figure 4. I’m the one in the front left,
hauling like crazy to catch my near
spacecraft before it lands.
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Often, the BalloonSat team
accompanies the near space crew
on the chase and recovery.
However, they may not be prepared for the task of actually
hiking out to get their stuff back!
On my last BalloonSat mission, I helped Idaho State
University launch four BalloonSats.
We ran into a slight problem on this
flight. We sent four BalloonSats up
but only one came back. The
metal tube in the top BalloonSat
abraded the flight line that carried
all of the BalloonSats. Eventually,
the metal tube cut the flight line
and three BalloonSats below
dropped off. Fortunately, a farmer
found the three in his field and
sent them back. On a positive
note, I got my closest to catching
a descending near spacecraft on
this flight. I missed grabbing my
JULY 2005
