# Bottle rocket project

Define the problem: To make a working rocket out of a 2 liter bottlel

Brainstorming:

Research and generating ideas:

The rocket has to have a good combination of Drag, Lift, Thrust, and weight for the rocket to have good stability and to go high.

You have to have a good shape do the top of your rocket so it will not have drag.

You have to know what your rocket can handle in a weather system so it dose not come crashing down and break.

Thrust acts the rocket through the center of gravity.

Drag acts through the center of pressure.

Lift also acts through the center of pressure.

Weight also acts through the center of gravity.

Gravity is strongest on the surface of earth and the further it goes up the gravities pull decreases.

Density will change with altitude.

The air density for your bottle rocket is constant at 1.2 kg/m3.

Drag increases with the square of velocity

Velocity is not directly controlled by you. However, changing your frontal area and drag coefficient will help change your maximum velocity.

The frontal area is the area of the geometry you would see if the rocket were coming right at you

The way to change your frontal area is to use a different size bottle

The coefficient of drag is a pretty complicated variable involving the shape of the rocket moving through the air.

You can control the coefficient of drag by adjusting the shape of the transition cone. The term streamlining is used to describe adjusting the shape of an object, for example your transition cone, to reduce pressure and friction caused by air flow.

Stability

It is important for a rocket to have and maintain stable flight. In order to maintain stable flight, rotation around all three axes - especially yaw and pitch - must be prevented. The reason controlling rotation is more important around the yaw and pitch axes is because instabiliy about these axes would change the intended flight path. If the rocket was to rotate around the roll axis the flight path would not necessarily change. In order to understand rocket stability you must first learn about two very important points on the rocket. These two points are the center of gravity (CG) and center of pressure (CP).

The center of gravity is the "balance point" of the rocket. If you were to balance a pencil on your finger, the point on the pencil directly above your finger would be the center of gravity. The pencil is in balance because there is an equal amount of mass on the left and right of your finger. This is the same with a rocket. The center of gravity is at the point were the mass on the nose end is equal to the mass on the tail end of the rocket.

The center of pressure is the point through which the drag force acts and any wind forces

A recovery system is part of the rocket that allows the rocket to safely return to earth after launch. There are many different types of recovery systems, but we will focus on the types available in the Rockets 2.0 application: Standard or "Lawndart", tumble, backslider, and a parachute. The parachute is an active recovery system, and the others are all considered passive recovery systems.

Passive recovery system

The standard (lawndart), tumble, and backslider recovery systems are considered passive designs because the rocket's return to earth is largely based on the same principles of stability that took the rocket upwards. In other words, there is no system that "kicks in" at the right time to safely bring the rocket back to earth. So to understand how these passive recovery systems work, we need to consider each in the context of stability - specifically the static margin.

Active recovery systems tend to be better for heavier rockets, and provide a safer recovery. However, active recovery systems are often more complex, have a higher chance of failure, and add weight to the rocket

Action Items

You should design your recovery system to minimize the falling velocity of the rocket. Since drag depends on velocity, drag increases until the drag force is equal to weight. When the drag force and weight are equal the rocket has reached "terminal velocity". Use the following animation to see how weight and parachute size - the two independent variables that you can control - will affect terminal velocity.

Citations/ references: Whiteboxlearning.com

Identifying and specifying constraints:

Exploring possibilities:

I would need to have a bottle and put fins on it. I would need to make sure it is light as it can be. I have to have as much stability as possible. I need the rocket to go as high as possible and to be very stable as it is reaching greater heights. Once the rocket reaches its greatest height I need for the parachute to come out so it will come down softly.

Developing a design proposal :

Testing and evaluating the design using specifications:

We only tested once. My parachute was to to big but if i could have wrapped my parachute a little tighter i think it would have deployed. It went up pretty high and I felt pretty good about my rocket.

Refining the design:

If I could do it over I would make it to were my nose cone was a little bigger in width so that my parachute could have had room to deploy and the rocket would have most likely came down safely. I Would have also made my fins a little more sturdy.

Creating it or making it:

I would make it to where it would not break as easy so that you would make sure it would work still after one run. I would also make it to where the parachute would be almost guaranteed to deploy. I would make it to where all the fins and everything would be even to each other.