Bottle Rockets. The bottle rocket, like the squid, uses water as the driving agent and compressed air instead of heat to provide the energy.

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1 Bottle Rockets Problem/Purpose: To create a bottle rocket that will fly straight and will stay in the air for as long as possible. Background Information: A squid propels itself by filling its body with water and ejecting it backwards in order to move forwards. This is the principle used by rocket engineers. Space rockets use fuels that are burned in a chamber shaped rather like a bottle, with the neck pointing backwards. The burning fuel produces a large quantity of gas that is further expanded by the heat generated and this is ejected through the neck (or nozzle) of the bottle (normally called the combustion chamber) at a very high velocity, propelling the rocket in the opposite direction (one of Newton s laws). The bottle rocket, like the squid, uses water as the driving agent and compressed air instead of heat to provide the energy. For the technically minded, if the pressure in the bottle at launch is about 18 x 104 N/m2 (or about 25 psi). The water is forced through a nozzle with a cross sectional area of about 1cm2 and this produces a theoretical thrust of about 18 Newtons (about 3.9lbs) at launch. As the water is ejected the bottle rocket gets lighter resulting in an increased acceleration or g force. This increasing g force is one of the more unpleasant aspects of space flight that astronauts have to endure; a rocket leaving the earth s atmosphere would have to keep up this increasing acceleration for some time. The bottle rocket expels its charge of water in about 1 second so DON T WORRY, IT S NOT LIKELY TO GO INTO ORBIT! State Newton s three laws of motion (3 points) State Pascal s Principle (1 point) 1. Materials: Two empty 2-liter bottles Manila folders or cardboard or old cds or card stock Duct tape Clay or weight String Garbage bag for Parachute (large or tall kitchen trashcan bag) Optional Rules: Each group will use two standard 2-liter soda bottles to build their rocket. No commercially finished or model products may be used. One of the 2-liter bottles must be used as the pressurized body. There may not be any cuts or holes in the 2-liter bottle. The mass of the empty rocket should not exceed 300 grams. All energy put into the rocket must originate from the water/air pressure combination. All rockets will be launched at a pressure not to exceed 80 pounds per square inch. Once the rocket is pressurized, no student can touch or approach the rocket!!! All students will be required to wear safety goggles at all times!!! Prior to launch, each rocket must pass a safety inspection. Though various rocket components may separate during the flight, all must remain linked together with a maximum distance not to exceed three (3) meters. If a nose cone is used, it can separate. Students are not allowed to use hot glue or super glue in constructing their rockets. Cold glue is acceptable. The use of duct tape is required

2 Part I: Constructing Your Bottle Rocket Below is a diagram of how your bottle rocket should be put together: Stability weight goes here as well.. A) Sleeve a. A slit will be made in the two liter bottle for the sleeve. b. Using the slit, cut the top off of this bottle. Do not cut both bottles! c. You may also leave the bottom on the sleeve, if you want, to keep the rounded end as your nose. d. Attach the sleeve to the uncut bottle using duct tape. B) Stability a. Ideally you want your rocket to fly straight or it will reduce the rocket s performance. Your rocket s center of gravity is near the top middle of your rocket and we want to move it more toward the top without adding too much weight. b. Tape small objects to the bottom of your intact bottle, or place a chunk of mud or clay to the bottom. C) Nose Cone a. To construct the nose cone for you rocket use a piece of card stock. b. Draw a circle with a radius of 6 inches, and cut it out. c. Cut one slit from the outer edge of the circle to the center. d. Fold the poster board until it creates a cone that fits on top of you rocket. e. You can make a different shaped nose if you would like: such as a curved nose, a pointed nose, or an elongated nose. f. Attach the nose cone to the sleeve, use duct tape. D) Fins a. Create 3, 4, 5 or 6 fins to put on the pressurized bottle. b. Fins can be created from old cds, plastic bottle pieces, poster board, manila folders, card stock, or cardboard. c. Fins need to be strong, and not flexible. d. Fasten the fins to your rocket using tape. The fins need to be spaced equally apart. E) Parachute (not necessary, but you can try one if you want) a. Take a large garbage bag and lay it out flat. b. Cut a large circle out of the bag. c. Put 16 pieces of masking tape around the edges of the bag, evenly spaced. d. Punch one hole through each piece of tape. Use a reinforcement tab around each hole. e. Attach sixteen 32-inch long strings to the bag, evenly spaced. i. Put 4 strings on your parachute. Tie these four strings together at the base of the strings. ii. Repeat 3 more times. (You should have 4 groups of 4 strings) iii. Use duct tape to tape the ends of the strings to your pressurized bottle. f. Fold the parachute and strings so that it makes a z shape.

3 Parachute strings F) Water a. Look at the graph that has calculated the optimum amount of water for different size bottles. Remember how big your pressure bottle is, and look to see how many ml of water is suggested for your size bottle. b. Or you can just put in however much water you want. However, too much water will make it too heavy, too little and it will not launch as high. c. Cap your bottle to keep the water in, until launch. Pre-Design: How long do you want your rocket to be? How many fins? What shape will your fins be?_(draw it) How long will your nose cone be? What shape? Draw it) How will you make sure your rocket is balanced? What forces are acting on your rocket? Draw what you think your rocket will look like. Use Color. DATA: Mass of Rocket (g) no water Mass of Rocket Convert g to kg Amount of water for 1 st launch (ml) Amount of water for 2 nd launch (ml) # of fins and shape of fins (draw it) Weight in nose cone (state yes & object or no) Anything special you did for your rocket:

4 Draw and color your actual rocket: Measure your rocket and label measurements. Class Data Launch 1: Team Members Names Launch 1 Partner 1 Total Time (s) Launch 1 Partner 2 Total Time (s) Launch Information for & Average -Find the average of the ALL the Launch Times for your rocket: Time to Peak-(Divide the average time by 2)

5 List at least 1 thing you will do to modify your rocket to stay in the air longer: Make the modification on your rocket. Why did you choose to make this modification? Class Data Launch 2: Team Members Names Launch 1 Partner 1 Total Time (s) Launch 1 Partner 2 Total Time (s) Launch Information for & Average -Find the average of the ALL the Launch Times: Time to Peak-(Divide the average time by 2)

6 Launch # Pressure in PSI Pressure in Pascals (Multiple PSI : 1 pound per square inch= 6,895 Pa) 1 2 Average Calculations: Complete the following calculations. Be sure to show all of your work, use the correct units and significant digits. 1) Distance using time: How far the bottle rocket traveled (from the launch pad to its maximum height.) S= ½ a x t 2 For time to peak take total time and divide by 2. Distance = ½ 9.81 m/s 2 (total time time to peak) 2 d = 2) Average velocity Formula: v = distance time to peak v = 3) Momentum Formula: M = mass of rocket(kg) x velocity M = 4) Thrust Formula: Thrust = (π/2) = (Pressure in Pascals) x (nozzle diameter) 2 Thrust = (1.57) x (pa) x (0.022m) 2 Thrust = Analysis Questions: 1) Why didn t you fill the pressurized body all the way up with H 2 O? Explain using Newton s 1 st Law of motion. 2) Did the rocket and the water move in the same direction? Explain what happened using Newton s 3 rd Law of Motion. (What was the action and reaction?) Draw a picture. 3) How does the momentum of the rocket change as it lifts off? How does it change as it falls back to the ground? 4) What forces act against the rocket s momentum? 5) What causes the rocket to fly skyward? 6) Would a rocket launched in the mountains have a greater momentum or a rocket launched at sea level? Why? 7) How does the difference in external pressure (outside about 15 psi) to internal pressure (80 psi) of the rocket affect its distance? 8) How does Pascal s Principle apply to your rocket? 9) Where should the center of gravity be on your rocket in relation to the center of pressure? 10) What factors help make your rocket stable?