Connecting bearing swivels is
fast and easy with split rings
The parachute apex with its bearing swivel.
ing the balloon or you’ll get a very
fast descent after the balloon bursts.
Now let’s look at an electronic
device that you might add to your
parachute as an aid to recovery.
Normally, a burst balloon remains
attached to the apex of the
parachute during the descent to the
ground. This doesn’t harm the
descent, but does make it more
chaotic due in part to the weight and
drag of the burst balloon trailing
behind the parachute at the end of
a 20 foot load line. As the burst
balloon swings around, it tugs on the
parachute causing it to swing and tip.
If we cut away the balloon, there’ll be
no off-balanced forces pulling on the
parachute and the descent is more
like an elevator ride.
Many near spacecraft carry an
audio beacon to help locate it when
it lands in tall grass or a corn field.
The downside of the audio beacon is
that it starts wailing away while
you’re launching the near spacecraft.
It’s not pleasant to be the
one nearest the audio
beacon during a near
spacecraft launch. (Man,
it sure would be nice if
the audio beacon would
only start up on descent
radio signal (or lack thereof) from the
near spacecraft. This device cuts
away the balloon by melting the load
line running through its nichrome
coil. An I/O pin of the PICAXE
operates the coil by controlling a
simple SPST reed relay. The coil only
needs to get hot for a few seconds to
melt the load line. After melting, the
balloon is free to continue ascending
if it hasn’t burst yet. This gives the
Smart Cutdown the ability to
terminate the ascent of a near space
mission at any point. If the balloon
has already burst, then the balloon
and load line drop away from the
parachute, making the descent easier
on the near spacecraft.
To enable the nichrome coil to
melt the load line in just a few
seconds, the coil needs insulation
from the cold near space air. Not
The recovery aid I
designed to counter the
two problems mentioned
above is the Smart
Cutdown. It’s PICAXE
controlled and can cut
away the balloon and
start the audio beacon
based on either mission
elapsed time (MET) or a
Each hole is centered vertically in the hoop’s
side and 90 degrees apart. Don’t sweat it if
your holes are mildly misaligned.
The outer hoop’s clamp was removed and the gap
was filled with a block of basswood. The letter
visible on the hoop’s side was part of a test. I was
experiencing too many knots in the shroud line
and thought labeling every connection would help
reduce their numbers.
Two bearing swivels attached to the cross stitch loop.
I don’t feel the heat shrink next to the bearing swivel knots
is necessary anymore.
To make the interior knot larger and more resistant
to coming unknotted, there’s a sleeve of heat
shrink over it.