The Force of Propulsion
By: Lesley Baker
Room 12
Due: Monday, February 1, 2010
                          
Table of Contents
1. Abstract………………………………. 3
2. Introduction Section ....................…..... 4
3. Research Summary (Fluid As A Fuel)...4
4. Experimental Section …………….,….. 5
4. Diagram of the Launch Pad ...................8
5. Results Section ………………………. 9
6. Discussion Section …………………... 13
7. Conclusion Section ………………..… 14
8. Bibliography ……………………..….. 15
9. Acknowledgments………………….....15
10. Rough Draft ………………………… 15
Abstract
Have you ever wondered what it was like to travel into space? Ontheotherhand, use a great force to propell into the air. Alternatively, how much force is need for a rocket to move through the air? I pondered about these questions when I was younger and thought about being an astronaut. In the 4^{th} grade, I witness for the first time the launching of the space shuttle in class. It was amazing. There was a lot of force used for the rocket to break free form the Earth’s gravitational pull.
This year’s science fair topic is on propulsion. Is it possible to launch a 2liter bottle a distance of 10 feet? The hypothesis to be tested is if I launch a 2liter bottle with a pressure of 30 pounds, then it will travel a distance of 10 feet because there will be enough propulsion to travel that distance. In order to test my hypothesis, I would use a launch pad powered by a bike pump and only air for the liquid fuel.
The independent variable that was tested is the amount of air pressured applied to the bottle rocket for a propellant. The observation showed that an increase in air pressure would increase the distance the bottle rocket will travel. On average, the rocket traveled a distance of 8.17 ft when 20 lbs of pressure. When using 30 lbs of pressure, the rocket traveled 12.26 ft. That is a difference of 4.09 ft. There was a difference in speed between the two pressures used. The rocket with 20 lbs of pressure traveled at a speed of 8.50 ft/s and the rocket with 30 lbs of pressure was log at 9.83 ft/s. That is a difference of 1.33 ft/s.
The observations and calculations disproved my hypotheses of if I launch a 2liter bottle with a pressure of 30 pounds, then it will travel a distance of 10 feet because there will be enough thrust to travel that distance to be invalid. The rocket traveled further by a distance of 2.26 feet. I was off by 34%.
Introduction
Have you ever wondered what it was like to travel into space? Ontheotherhand, use a great force to propel into the air. Alternatively, how much force is need for a rocket to move through the air? I pondered about these questions when I was younger and thought about being an astronaut. In the 4^{th} grade, I witness for the first time the launching of the space shuttle in class. It was amazing. There was a lot of force used for the rocket to break free form the Earth’s gravitational pull.
This year’s science fair topic is on propulsion. In other wards, how much force is need for a 2liter bottle to travel a distance of 10 feet? Is it possible to launch a 2liter bottle a distance of 10 feet? The hypothesis to be tested is if I launch a 2liter bottle with a pressure of 30 pounds, then it will travel a distance of 10 feet because there will be enough propulsion to travel that distance. In order to test my hypothesis, I would use a launch pad powered by a bike pump and only air for the liquid fuel.
Fluids as Fuel
Why is there a need to study space when there is so much here on Earth that we do not understand? Is it because of the yearning to understand where we, it all came from? In order to find that out, we need to look beyond our realm to outer space. Astronomy is the original science. Observing the stars began before technology, modern medicine, and formal language. Ancient cultures used the stars and planets to mark yearly cycles such as harvest and the best time to plant the crops. The information about the movement of the stars and planets were used to develop the first calendars. In order to find out more about the planets and stars by observing through a telescope such as Galileo and Edward Hubble or using nonoptical telescopes to detect electromagnetic radiation of distant object, we needed to breach our own atmosphere so we can have a better look. However, how do we do this?
Konstantin Tsiolkovsky, a Russian High School teacher, proposed that machines called rockets could take people to outer space, (Hemenway, Kay, and Meech, p. 137). Tsiolkovsky’s idea came from a novel by Jules Verne titled “From the Earth to the Moon”. The characters in this book reached the moon in a capsule shot from an enormous cannon, (Hemenway, Kay, and Meech, p. 134). How could this happen? So far is was a scientific theory that if enough force was generated from the rocket, the capsule could reach outer space. He even suggested the use of liquid rocket fuel just might do the trick. Tsiolkovsky’s inspirations lead him to being the father of rocket science even though he never built a rocket.
Robert Goddard, an American Physicist and inventor launch the first successful liquidfuel rocket in 1926, (Hemenway, Kay, and Meech, p. 134). The military became very interested in this invention as a weapon, so did other countries like Germany. In World War II Germany, Dr. Wernher von Braun and his research team surrender to the United States military after further advancement. The team developed a new weapon, the V2 rocket that can travel a distance of 350 km., (Hemenway, Kay, and Meech, p. 135). What a boost to the United States rocket science program. This then lead to the creation of NASA in 1958.
Gravity is a force that works against us when we jump or want to launch an object up into the sky. In order to work against gravity, think about Sir Isaac Newton’s 3^{rd} Law of Motion, which states that for every action, there is an equal, and opposite reaction. Rockets need fuel to propel itself in the opposite direction of gravity. Thrust; the force needed an object to accelerate a rocket. Konstantin Tsiolkovsky theorized about this and Robert Goddard put liquid fuel to use as thrust. However, can other fluids such as an air mixture be useful as a propellant?
Experimental Section
Problem Question
How much force is need for a 2liter bottle to travel a distance of 10 meters?
Hypothesis
If I launch a 2liter bottle with a pressure of 30 pounds, then it will travel a distance of 10 meters because there will be enough thrust to travel that distance.
Variables Chart
Independent Variable 
Dependent Variables 
Control Variables 
Amount of air pressure 
Distance traveled Speed Time in the air

Angle of the launch pad Direction of the launch pad Air temperature Wind Size of the plastic bottle 
Qualitative Observations
Independent Variable 
Dependent Variables 
Qualitative Observations 
Amount of air pressure 
Distance traveled Speed Time in the air

Direction the rocket travel Quality of travel, wobbles or flies straight 
Quantitative Observations
Independent Variable 
Dependent Variables 
Quantitative Observations 
Operational Definition 
Amount of air pressure 
Distance traveled Speed Time in the air

Distance traveled Time Speed 
Tape measure in meters Stopwatch in seconds Formula S=d/t 
Materials:
Bottle rocket launcher
2liter plastic bottles (2)
Plastic bottle rocket launcher
Launch pad
Bike tire pump with a gauge
Newspapers (2)
Vaseline jar
Tape measure
Stopwatch
Launching & Testing Procedures:
1. Locate an open area
2. Place the newspaper on the floor or ground to cover an area 1meter by 1 meter
3. Place the launch pad on top of the newspaper pointing the arrow towards your target
4. Stretch the measuring tape to a distance of 30 meters
5. Stretch out the clear rubber tubing
6. Open the lever on the tire pump; place the metal end of the tube in to the opening of the tire pump; close the lever on the pump
7. Pull the opposite end of the rubber tubing gently to give you some slack
8. Smear a thin layer of petroleum jelly on the rubber stopper
9. Insert the rubber stopper end of the tubing into the 2liter plastic bottle
10. Gently pull the rubber tubing away from the launch pad until the 2liter bottle rest onto 2 metal bars
11. Adjust the metal arms so that the notch fits snug on the rim of the 2liter bottle
12. Gently insert the u –shape ring into the 2 holes on the metal arms. Do not push it all the way through
13. Use the protractor to adjust the metal bar base to an angle of 55 degrees
14. Align the bottle to the measuring tape
15. Stretch out the string attached to the ushape metal ring
16. Use the tire pump to add 30 lbs of air into the 2liter bottle
17. Kneel to the left side of the launch pad where the string was placed, not behind the launch pad
18. Pull the string towards you at the same height that the ushape ring is inserted into, do not pull the string at an angle
19. Start the stopwatch at the launch and stop it when the rocket landed
20. Measure the distance from the rocket launcher until where the rocket touched the ground / floor the first time
21. Complete 12 launches to check the equipment
22. Record your observations on the data sheet
23. Repeat steps 621 nine times, exclude step 21 at the same pressure, then again for another 10 times at a different pressure
24. Repeat steps 621, exclude steps 21 using 20 lbs of pressure
Safety Procedures:
1. Do not stand behind or in front of the 2liter bottle when the tire pump has added air pressure to the bottle
2. If there is a misfire, gentle pull on the rubber hose or release the lever on the tire pump so pressure is release safely
3. Before pulling the string to release the rocket into the air, make sure the landing zone is clear of objects and people
4. Say a count down before pulling the string
5. Do not pull the string at an angle; you may have a misfire
Diagram of the Launch SetUp:
Results
Rocket Launched with 20 lbs of Pressure
Trial 
Time in seconds 
Distance in meters 
Speed in m/s 
Other observations 
1 
0.95 
8.2 
8.63 
To the right, wobble 
2 
0.96 
8.1 
8.43 
To the right, wobble 
3 
0.98 
8.4 
8.57 
Straight, skipped a lot 
4 
0.95 
8.3 
8.74 
To the right, skipped some 
5 
0.94 
8.0 
8.51 
To the left, skipped 
6 
0.96 
8.2 
8.54 
To the right, wobbled 
7 
0.99 
8.1 
8.18 
To the left, skipped 
8 
0.98 
7.9 
8.06 
To the left, skipped sideways 
9 
0.95 
8.3 
8.74 
Straight, skipped 
10 
0.96 
8.2 
8.54 
Straight, wobbled 
Mean 
0.962 
8.17 
8.495 

Rocket Launched with 30 lbs of Pressure
Trial 
Time in seconds 
Distance in meters 
Speed in m/s 
Other observations 
1 
1.23 
12.5 
10.16 
Straight, skipped 
2 
1.33 
12.2 
9.17 
Straight, skipped to the wall 
3 
1.28 
11.9 
9.29 
To the right, skipped 
4 
1.20 
12.3 
10.25 
Wobbled, to the right, skipped 
5 
1.28 
12.2 
9.53 
To the left, skipped 
6 
1.21 
12.2 
10.08 
To the right, skipped 
7 
1.23 
12.4 
10.8 
To the right, wobble 
8 
1.22 
12.3 
10.8 
To the left, skipped 
9 
1.22 
12.1 
9.92 
Straight, skipped 
10 
1.28 
12.5 
9.77 
Straight, skipped to the door 
Mean 
1.248 
12.26 
9.83 
Straight, skipped alot 
Speed Calculations Examples:
Average speed for 20 lbs of pressure
Speed = distance / time
Speed= 8.17 m / 0.96 sec = 8.495 m/s
Average speed for 30 lbs of pressure
Speed = distance / time
Speed = 12.26 m / 1.28 sec = 9.83 m /s
Analysis of Data
Categories 
20 lbs of Pressure 
30 lbs of Pressure 

Mean 
Distance 8.17 m 
Speed 8.495 m/s 
Distance 12.26 m 
Speed 12.26 m/s 
Median 
8.2 m 
8.54 m/s 
12.3 m 
9.92 m/s 
Mode 
8.1 m, 8.2 m, 8.3 m 
No Mode 
12.2 m, 12.3 m, 12.5 m 
10.8 m/s 
Range 
0.06 m 
0.68 m/s 
0.6 m 
1.03 m/s 
Differences Between 20 lbs vs. 30 lbs
Categories 
20 lbs 
30 lbs 
Difference 
Percent difference 
Distance average 
8.17 m 
12.26 m 
4.09 m 
33% 
Speed average 
8.495 m / s 
9.83 m / s 
1.335 m/s 
15.4% 
Graphs:
Graph: Trials of Launches Measured in Meters
Graph: Mean Distance of 20 lbs vs. 30 lbs
Graph: Speed Rocket Traveled in m/s
Graph Mean Speed of 20 lbs vs. 30 lbs
Discussion
The distance the bottle rocket travel depended on a few factors. These events were observed when checking the launch pad equipment. One of the factors is the angle of the legs on launch pad. The angle can change from one launch to another due to the force released by the rocket when it is launch. It all comes down to Newton’s 3^{rd} Law of Motion for this event. The angle was checked after each launch or the rocket will be angled at a higher angle changing the control variable to an independent variable. This event could increase or decrease the distance the rocket travels depending on how much the angle increased toward 180 degrees to the left. Another factor is the direction the rocket will travel. Since the experiments were held inside, the walls of the hallway were a factor. Before each launch, I needed to align the bottle to the measuring tape to be sure the rocket will travel in a straight line. If the rocket was not lineup with the tape, it will increase the risk of hitting the walls and having a miss fire. There was a need to add petroleum jelly to the rubber stopper in order to decrease the amount of friction between the inside of the neck of the bottle and the rubber stopper. The increase in friction also can change the direction the rocket will travel. The increases in friction cause the rocket not to be launch from the launch pad, but to be stuck to the rubber stopper. Once the arms fell off the lip of the bottle, the bottle was hanging onto the rubber stopper. Now, the tip of the bottle is pointing down or at a 180degree angle, changing the distance the rocket will travel.
When I was checking the equipment of the launch pad, I did not realize what other factors where involved needed to be controlled, such as the amount of friction generated between the rubber stopper and the inside of the neck of the bottle. In this instance, petroleum jelly was smeared in a thin layer to prevent friction from occurring so the rocket will not misfire. The angle of the launch could change from launch to launch due to the amount of force the air pressure released from the bottle upon the launch. The angle had to be check with a protractor to maintain accuracy.
In the qualitative observations, the rocket at times traveled to the right or to the left. This was due to an increase in friction between the inside of the neck of the bottle and the rubber stopper. This could also be the reason why the rocket wobbled while traveling through the air. It could also be due to pulling too hard on the trigger, which pulled the launch pad to the left. If the bottle was not aligning properly to the measuring tape, the bottle could travel more to the left or to the right.
The factor that was tested is the amount of air pressured applied to the bottle rocket for a propellant. The observation showed that an increase in air pressure would increase the distance the bottle rocket will travel. On average, the rocket traveled a distance of 8.17 m when 20 lbs of pressure. When using 30 lbs of pressure, the rocket traveled 12.26 m. That is a difference of 4.09 m. There was a difference in speed between the two pressures used. The rocket with 20 lbs of pressure traveled at a speed of 8.50 m/s and the rocket with 30 lbs of pressure was log at 9.83 m/s. That is a difference of 1.33 m/s.
These observations and calculations disproved my hypotheses of if I launch a 2liter bottle with a pressure of 30 pounds, then it will travel a distance of 10 m because there will be enough thrust to travel that distance to be invalid. The rocket traveled further by a distance of 2.26 m. I was off by 34%. The other factors which could effect the data is not pressing the stop watch accurately enough or having not another person to help observe an accurate distance is possible since the bottle skips once it hit the floor even thought I was measuring from where the bottle hit the ground first could have effect my results. Ontheotherhand, if the observations were collect with more accuracy, with every 10lbs of pressure added to the bottle rocket, it could increase a distance travel by 35% each time.
Conclusion
The hypothesis that was tested, if I launch a 2liter bottle with a pressure of 30 pounds, then it will travel a distance of 10m because there will be enough thrust to travel that distance, was proven invalid. The rocket traveled further by a distance of 2.26m, which is a 35% more than I predicted. The air pressure that is applied provided more thrust than previously believed. If more air pressure was added in increments of 10lbs, there is a possibility the rocket will travel by an increase in distance of 35%. Next time, I will test to verify if an increase of 35% in distance would occur when 10 lbs of pressure is true or a fluke.
Bibliography
1. Giancoli, Douglas C. Physics, Principals with Applications. Englewood Cliffs, NJ: Prentice Hall, 1991.
2. Hemenway Ph.D., Mary Kay, and Meech Ph. D, Karen, Astronomy Holt Science & Technology. New York: Holt, Rhinehart & Winston, 2005.
3. www.nasa.gov
5. http://wwwistp.gsfc.nasa.gov/stargaze/Srocket.htm
6. http://waterocket.explorer.free.fr/workshop.htm
7. http://www.lnhs.org/hayhurst/rockets
8. http://exploration.grc.nasa.gov/education/rocket/bgmr.html
9. Goddard, Robert H. Rockets. New York: Dover Publications, Inc., 2002.
Acknowledgements
If you have read this report, congratulations. Here is how you can earn some extra credit. You need to examine the bibliographies above. Then observe what is missing in the bibliography format. On a sheet of looseleaf paper, write your answers or email your answers to me.
After the bibliography is the appendix. Any loose leaf papers or worksheets that you did not add to the composition notebook is then added here.
GOOD LUCK!!