### What is my rocket’s mass?

Usually the manufacturer of your rocket will have that type of information on their website or through a catalogue. If you’re making your own rocket, you might try asking a high school science teacher if you can use a scale. According to the Estes Catalogue, my rocket itself weighed in at **12 grams**. However, you also have to take into account the weight of your engine. I assumed I’d use the biggest engine possible, which was a C engine that weighed **26.9 grams** and had **12.48 grams** of propellant. So how do you find the final weight that you’ll use for calculations? Take the rocket weight + engine weight – propellant weight. For me, this was **12 + 26.9 – 12.48 = 26.42 grams**. For the sake of it, I rounded up to 27 grams, or **.027 kilograms**.

I used the equation on the math and theory page, and using a velocity of **3 m/s**, a mass of **.027 kilograms**, and a drag coefficient of **1.5**, I determined that a chute of **.202 meters** was needed, or 7.95 inches. Again, just for the sake of being safe I rounded up to an **eight inch diameter chute**.

In order for air to escape it is necessary to have a hole in the top of the parachute — I’ve heard about 10% of your surface area, but for my chute that seemed like too much. Here’s how to figure out how much you should cut out..

- Find surface area (pi * radius
^{2}) [pi * 4.5^{2}= 63.6 in^{2}] - Take 10% of that [6.36 in
^{2}] - Find radius of that [6.36 = pi * r
^{2}— solve for r -> 1.42] - Double radius to get diameter [2.84]

A 2.84 diameter hole just seemed like too much for me, and since this was just a fun project I went with a **1 inch diameter hole**. Now that we have everything planned out, it’s time to move onto the design phase.

Next: Designing the Parachute