## Designing the Parachute

### What material should you use?

Doesn’t really matter — but make sure it’s durable. I had some packing bubble wrap stuff from sharper image so I cut the bubble into a flat piece. From there I pinned it onto a sewing cutting board (made of cardboard), and stuck a pin in where I thought a good middle of my circle would be. Next, I cut a piece of string that was the length of my intended radius (4 inches) and attached the string to the center pin. Next, I attached a permanent marker to the string, and drew a perfect circle just by dragging the pen along the material and keeping the string taunt. Alas, voila, we have our circle that will soon become our parachute.

### Now what?

The parachute has to be connected to something — I wasn’t really sure what type of cord I should use, so I just picked some kite string. If I were you I would NOT use kite string — I will address this later. So I poked several holes into parachute and tied the string into each one. From there I tied all the strings together, then finally made a string to connect all the strings to the elastic band that connected the rocket to the nose cone. I thought I was done, but little did I know…

### The Failure

The dumb parachute wouldn’t fit into the tube! The chute itself would fit in, but because I used thick kite string, it just jammed up in the tube (which was only 18mm in diameter). The moral of the story? A) Make sure you’re conscious of the size of your parachute — a big parachute isn’t going to fit into a small container and B) use THIN cord! The kite rope easily took up twice the volume of my chute, so I just got mad.

### The Solution

Scrap it! Since the string was hogging all my room, I decided to go with a square chute instead because it would use less cord. After redoing my calculations, using a drag coefficient of .75 (square/rectangular chute) I solved for area this time (since diameter is only for a circle) and my new area was .06426 m^2

.

I had absolutely no basis for the ratio of length to width, so I just picked one of my pictures that I drew of a parachute and went with 1:2.2. Using that, I solved for x in the equation

.06426 = x(2.2x)
x = .1709m (6.73in)
2.2x = .376m (14.8in)

I cut out a new pattern (it was much easier to cut out since it was just a rectangle) and evenly spaced out three holes on each shorter side. Instead of using kite string I used some very thick sewing string and tied it all together in a similar fashion to what I did previously.

Next: Problems