Near Space
ments for new ones. These experiments are what excite
me the most about the amateur near space program.
Airframes
Components of the near spacecraft.
around during a mission, just like foam rubber does. When
possible, use a standardized airframe design and avionics
pallet. This way, you can have several airframes and avionics pallets that can be mixed and matched as needed.
Experiments are the element that changes the most.
Typically, each new mission switches out the old experi-
The fastest way to get an airframe is to purchase an
insulated and reusable lunch bag. In this style of airframe,
the avionics are either mounted to a sheet of correplast (a
pallet) with zip ties or fitted into a block of foam rubber
that has been cut to fit the interior space of the lunch bag.
Never rely on the rubber ducky antenna that comes with
most handheld radios, as they tend to have poor gain.
Instead, use a flexible J-Pole or dipole antenna connected
to the handheld radio's antenna jack. The rest of the antenna is left dangling outside of the closed bag. Parachute
shroud lines are attached securely to the hand strap. Never
use a snap swivel to attach the parachute to the airframe,
as it can pop open. A popped snap swivel terminates a
near space mission much sooner than planned. A reusable
lunch bag and simple tracker, as described below, make an
ideal first near spacecraft or backup tracker for a more
advanced near spacecraft design.
More elaborate airframes are constructed from a 3/4"
thick Styrofoam sheet. The best source of this material is
the blue or pink Styrofoam sheeting used to insulate
homes. This material is very popular and can be found at
virtually every home improvement store. Styrofoam is the
ideal material because it is strong, warm, lightweight, and
inexpensive. Styrofoam is also very easy to machine; you
only need a sharp Xacto knife and metal straight edge to
cut the foam. A good adhesive to glue the sides of your cut
Styrofoam panels together is hot glue. As it sets very
quickly, hot glue is as easy to work with as Styrofoam. Just
be sure to keep the glue below its maximum temperature,
because it can begin to melt the Styrofoam.
After constructing your airframe,
you may wish to add more insulation
to its exterior. To keep spacecraft
warm, aerospace companies wrap
their spacecraft in multilayer insulation (MLI). Their MLI is constructed
from alternating layers of space-rated
aluminized Mylar or Kapton and a
scrim (plastic mesh) inner layer. A
homemade version of MLI is made
from space blanket and wedding veil
material. At this time, however, I'm
not certain the vacuum of near space
is "hard" enough to make the MLI
effective.
During its mission, the interior of
your near spacecraft module will chill
in the freezing air. The cold of near
space is severe to some items, like
batteries. From personal experience,
I can tell you that cold batteries can
make for a bad day. In some cases
the batteries get so cold that they fail
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Circle #110 on the Reader Service Card.
