Balloon Recovery System
- ~$8/yd, from Lens Mill
What Other People Done
Most near-space launches I've found used commercially available parachutes. Those who built their own chutes haven't provided detailed information regarding how they designed or constructed the chutes. We may have to look further a-field.
BYU-Idaho used a home-made chute for their first launch, without success: "...the parachute did not deploy very well. In fact, during a pre-flight test on launch day, the parachute was seen to deploy, then collapse. It is suspected that somehow, the parachute may have deployed partially, or not at all."
They also say the parachute was "[n]ot built according to any real standards, the parachute was our best attempt, and very little analysis and testing were put into its design"
1337arts used a plastic parachute which they all ready had on hand for their first launch, and a trash bag for a second launch.
These are 48" hemispherical balloons made of ripstop nylon. Detailed information about the balloon construction: http://www.fruitychutes.com/how_to_make_a_parachute.htm
A program called RockSim "can predict descent speed for a given weight and size chute within about 5% by setting the parachute Cd to 1.5. This value has been proven accurate over the course of many flights under various conditions."