Aaron's Bottle Rocket
Step 1 Defining a problem
We need to be able to build a rocket that will function properly and our goal is to make it stay in the air the longest.
Step 2 Brainstorming
Step 3. Researching and Generating Ideas
Notes: People have been interested in the topic of flying now for a long time. The first type of rocket was made in Greece and it was propelled by steam. Over time other cultures have integrated their ideas into the designs of the rocket. The Chinese transferred from a steam powered rocket to a gunpowder rocket. This was the transition to a solid fuel rocket. The solid fuel rocket was used all the way up to even the Revolutionary War. At this time they had decided to make a rocket without the stick at the bottom. By the end of the 19th century space travel was in people’s minds. During World War I many scientists began to stop studying rockets and began to make other things such as plans. They also made other machines for the war that was going on. Robert H. Goddard continued to focus on rockets. He made the first rocket that was to be powered by a liquid fuel source. After World War II American scientists went to Europe trying to help come up with designs of rockets. Rockets were used to power planes. The space race began to be the first to put a rocket into space and also to have the first person on the moon. Rockets continue to be developed and made better.
Layers of atmosphere-1) troposphere- sea level to 11 miles 2)stratosphere- 11 to 31 miles ozone layer 3)mesosphere- 31 to 50 miles 4) ionosphere- 50- 400 miles 5) 400-800 miles
Drag is created by air resistance. Imagine running down a track with a small parachute attached to your back. You would notice that it is more difficult to run with the parachute pulling you back versus running with no parachute. The parachute, in this example, causes considerable drag. When a rocket flies through the air, drag pushes back - or resists the rocket's forward motion. A rocket's drag is affected by shape, texture, velocity, as well as other factors.
Lift - On a rocket, Lift is a side force used to stabilize and control the direction of flight. This is quite different from the concept of lift as it relates to an airplane. On an airplane, lift is a force that overcomes weight to enable flight. In the Rockets 2.0 application, we will simply discuss the concept of stability to avoid confusion.
Thrust - This is the force that produces lift-off, or upward movement of a rocket. Thrust is produced by engines or some other form of propulsion system. For lift-off to be achieved, thrust must exceed weight.
Weight - A combination of factors affect the weight of a rocket and can include cargo, passengers, fuel, parts of the rocket, materials, and other items. Weight is related to mass, but also includes the gravitational pull of the Earth.
- Roll is a twisting motion about the roll (longitudinal) axis. Roll movement is not really a problem on a water rocket since it does not tend to alter the rocket's flight path.
- Pitch refers to an up and down movement of the rocket's nose. This movement can take the rocket off of its intended flight path and could result from a gust of wind. Careful attention to the location of the center of gravity and center of pressure will ensure pitch stability.
- Yaw refers to the side to side movement of the rocket's nose. This movement can take the rocket off of its intended flight path and could result from a gust of wind (very similar to pitch). Careful attention to the location of the center of gravity and center of pressure will ensure yaw stability.
- Thrust is what gives the rocket the upward movement
- Newton’s third law of motion states= for every action, there is an equal and opposite reaction
- As you increase the velocity and decrease the amount of weight you use the rocket should go higher and descend faster.
- Drag = .5 * air density * velocity squared * frontal area * coefficient of drag
- Air density for your bottle rocket is 1.2 kg/meters cubed
- Increasing frontal area will result in higher drag, so maximizing frontal area is a good way to minimize drag.
- Frontal area= pi times radius squared
In order for rocket to have and maintain stable flight all three axes must be prevented
Center of gravity and center of pressure
- Center of gravity is “balance point”
- Mass=density x volume
- Distance between center of gravity and center of pressure Is known as the static margin.
- Rule of thumb- static margin should be greater than or equal to the bottle diameter/ center of gravity should be closer to the nose of the rocket than the center of the rocket.
- Changing the static margin changes the stability of the rocket
- If you want to shift center of gravity to the front or the back add weight in the direction you want it to be Recovery-
- recovery system is the part of the rocket that allows it to return safely to the ground
- Passive recovery systems are standard, recovery, and backsliding/ there is nothing that kicks in it is the principle of stability that returns it to the ground.
- The first is a lawndart. The rocket reaches its maximum altitude, then rotates and falls nose first back to earth. The lawndart works due to high positive static margin, meaning that the center of gravity is closer to the nose than the center of pressure. The center of gravity always falls first, thus the nose will impact the ground first with a lawndart recovery system. Due to the rocket having relatively low drag, the rocket falls quickly and the nose takes a relatively high impact onto the ground.
- The second passive recovery is tumbling. The rocket reaches a maximum altitude, then proceeds to tumble, spinning and rotating back to earth. Tumbling works due to a small positive or negative static margin. The rocket's drag is increased due to the way it is falling, slowing the decent. However, any part of the rocket may impact the earth.
- The third is backsliding. The rocket reaches maximum altitude, then falls tail, rear, or nozzle end first back to the earth. The backslider works due to a high negative static margin, meaning that the center of pressure is closer to the nose than the center of gravity. Again, the center of gravity falls first and since the center of gravity is closer to the tail, the tail impacts the ground first. The rocket falls relatively quickly and the tail takes a high impact into the earth.
- In general passive recovery systems are simple, lightweight, inexpensive, and reliable.
- Active recovery systems are better for heavier rockets/ they are more expensive and have a higher chance of failure and add weight to the rocket.
- Parachute is an active recovery system
- When the decent of the rocket begins it pulls the ball being it descends slower than the rocket it opens the parachute.
- The parachute increases total flight time
Step 4. Identifying Criteria and Specifying Constraints
Step 5. Exploring Possibilities
- The main concept of my design was to make my rocket have the lowest mass as possible but also go as high as possible and have the slowest decent.
- The rocket also needed to have a static margin that was equal to or greater than the diameter of the 2 liter bottle I was using/ my static was exceptionally larger than my diameter.
- I also needed to be able to get the stability equal to 1 or have it over one. Stability is what helps it go down to the ground as slow as possible and it has a smooth decent.
- The parachute was regulated at 279.40 so I went ahead and maxed that out as high as I could
- For my cone transition length and cone tube length, the cone transition needed to be small and the cone tube needed to be bigger. I needed to increase my static margin but not try to increase the mass at the same time.
- For my Nose I used a 38mm ball and I used the least amount of clay as I possibly could so that it would not affect my mass too much.
- My fins are made out of the lightest possible material. I could not let my fins add so much weight that it would affect the decent of the rocket but I also needed fins that would increase the static margin of my rocket. My fins don’t way much at all and they are as close as possible to the base so they increase the static margin.
Step 6. Selecting An Approach
Step 7. Developing a design proposal
Step 8. Making a model or prototype
Step 9. Testing and evaluating the design
Step 10. Refining the Design
- Use less spray paint so that it would weigh less
- Use less clay on the ping pong ball so it would weigh less
- Use a better material for the parachute
- Actually get the parachute to deploy
- Maybe use a better material for my fins
Step 11. Creating or making it
- Better Materials
- Make it more kid friendly
Step 12. Communicating processes and results