Adventures in Aerospace: Lesson 2 Volunteer’s Guide Key to Curriculum Formatting: ► Volunteer Directions ■ Volunteer Notes ♦ Volunteer-led Classroom Experiments Lesson 2: YOU’RE LAUNCHING A ROCKET! ► Begin the presentation by telling the class that this is “Lesson 2: You’re Launching a Rocket!” If this is your second visit, reintroduce yourself and the program. Briefly review key concepts from the first lesson, “You’re Piloting a Plane!” If this is your first visit, here is a suggested personal introduction: “Hello, my name is _____________, and I am a _________________ (position title) at Aerojet. I or another Aerojet volunteer will be visiting your class once over the next few months to speak to you about space exploration and space travel. We will learn about the basics of aerodynamics, rocket propulsion, and spaceflight to the space station, the moon, and future missions to Mars!” ► Answer any questions left over from the previous visit. MATERIALS NEEDED • AiA Multimedia Presentation (AMP) • DVD-ROM Page 1 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide • TV or projection screen • Handouts • Index cards ► See lesson to assess total equipment needs. LESSON OUTLINE Introduction Lesson Concepts Vocabulary Rockets vs. Airplanes Newton’s Laws • First Law • Second Law • Third Law What Type of Rocket Are You Launching? • Types of Engines Comparing and Contrasting Liquid Engines and Solid Motors Other Types of Rocket Engines Applying What We’ve Learned Experiment INTRODUCTION Rocket launches have mesmerized audiences, often entire nations, for centuries. What kind of power does it take to propel spacecraft out of the atmosphere and into the vacuum of space? This unit introduces you to rocket propulsion systems. Newton’s Laws will provide a basis for discussions of rocket engines, motors, propulsions, fuels, launch vehicles and future rocket engine concepts. LESSON CONCEPTS • Newton’s laws of motion • Rocket propulsions systems • Force and acceleration VOCABULARY Acceleration: Change in an object’s velocity Page 2 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide Air breathing engines: An engine that requires air for operation. Cryogenic fuels: Liquefied gas at very low temperature, such as liquid oxygen or hydrogen. Hypergolic liquids: Ignite and burn on contact. No ignition system required. Liquid rocket engines: An engine that utilizes liquid propellants. Solid rocket motors: Rocket motors that burn solid propellant. Monopropellant Liquid Rocket Engine: A rocket engine that utilizes a catalyst bed to “burn” the liquid fuel. Multi-stage rocket: A rocket consisting of two or more propulsion units (stages), stacked vertically to form the rocket structure, that fire in succession. Payload: All the cargo, including scientific equipment, carried into space by a rocket powered vehicle Oxidizer: A substance that provides the "air" to burn rocket fuel; can be a liquid or a solid material. Vector: A concept characterized by a magnitude and a direction. ROCKETS VS. AIRPLANES ► Tell the class that today's session deals with rocket propulsion. Tell them you've brought some very simple rockets with you. Take a couple of balloons out of your supply bag, blow them up, and release them into the crowd. Explain to the class that the balloon is technically a rocket because the balloon contains all of the propellant, in this case compressed air, needed to propel the balloon (rocket). Introduce the following key rocket propulsion concept: Rockets operate in the vacuum of space and must therefore carry not only the rocket engine fuel, but also the "air" (oxidizer) needed to burn the fuel in the rocket engine or motor. NEWTON'S LAWS Page 3 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide ♦ Newton’s Laws Experiment Experiment Concepts • Newton’s Laws of Motion Experiment Materials • 1 roller-skate Experiment Instructions 1. Introduce Isaac Newton's three laws of motion, developed more than 300 years ago (1687). Use a roller skate to illustrate. First Law of Motion An object at rest will stay at rest until an external force acts upon the object (a roller skate will remain motionless until an external force acts upon it) and a moving object will travel at a constant speed in a straight line until acted upon by an external force. (A moving roller skate will stop when it runs into the wall or when the friction of floor and air cause it to slow down and stop.) Page 4 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide Second Law of Motion Application of a force to a mass will cause it to accelerate. As long as a force is being applied, the mass will continue to accelerate. The defining mathematical expression is F=ma where F is the force applied, m is the mass of the object, and a is the object’s acceleration. F and a are vector quantities, which have both magnitude and direction. Third Law of Motion Every action produces an equal and opposite reaction. (The air escaping from the balloon pushes the balloon in the opposite direction. Falling off a roller skate makes the skate go in one direction and the skater in another!) Experiment Explanation What do these laws have to do with rockets? ► Use the following information to explain to your students how Newton's laws relate to launching a rocket. First Law of Motion A rocket on a launch pad is an object at rest. The rocket engine thrust is the force that will accelerate it into the atmosphere and on into space. Second Law of Motion The thrust of the rocket engine(s) and or motors provides the force (F) needed to accelerate (a) Page 5 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide the massive rocket (m) off the launch pad. F=ma. Note: The thrust of the rocket engines must exceed the weight of the rocket or the rocket will not lift off the launch pad! Third Law of Motion When the rocket propellant ignites, gases are formed that rush out of the nozzles at the back of the rocket. The gases go in one direction and the rocket goes in the opposite direction (away from the earth.) In summary, an unbalanced force must be exerted for a rocket to lift off from a launch pad or for a craft in space to change speed or direction (first law). The amount of thrust (force) produced by a rocket engine will be determined by the mass of rocket fuel that is burned and how fast the gas escapes the rocket (second law). The reaction, or motion, of the rocket is equal to and in the opposite direction of the action, or thrust, from the engine (third law). ► Perform the following experiment to illustrate Newton's 3rd law. ♦ Newton’s Third Law Experiment Experiment Concepts • Propellants • Newton’s third law of motion Experiment Materials • 1 large, empty plastic bottle • 1 cork (must fit snugly into the bottle opening) • Vinegar • Water • Baking Soda • 2X2 inch square of thin cloth or paper towel Experiment Instructions 1. Wrap baking soda in a napkin. Page 6 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide 2. Insert the napkin in a bottle. 3. Add vinegar. 4. Cork loosely and shake mixture. 5. Lay bottle quickly on its side on several round pencils or wooden dowels. 6. Observe the reaction as the cork is popped out. WHAT TYPE OF ROCKET ARE YOU LAUNCHING? Types of Engines The most common type of rocket propulsion systems are liquid or solid fueled. The following presentation video will help students see the difference between different types of rockets. ► Show the presentation video and the images of various solid and liquid rockets. Tell the students that we'll talk later about the advantages of each different kind of propellants. 1. Solid This rocket propulsion system uses a mixture of solid oxidizer and solid fuel. The fuel and oxidizer of the solid rocket motor feels like a hard rubber eraser and is usually dark in color. This mixture of fuel and oxidizer is called the solid propellant. There can be several other materials in the solid propellant besides the fuel and oxidizer (for example - binder, the material that holds the fuel and oxidizer together.) A high temperature flame is needed to Page 7 of 11 Adventures in Aerospace: Lesson 2 Volunteer’s Guide start the solid propellant burning. It continues to burn until all the solid propellant is consumed — you can't easily turn off a solid rocket motor once it starts! ► Show the class the sample of inert solid propellant (dog bone). Explain that these samples are used to test certain physical properties such as tensile strength. The fuel and the oxidizer have been left out of this sample so it will not ignite. The solid propellant is often poured into a case as thick liquid which then hardens. The shape of this solid propellant (a grain) determines how the trust will change while the propellant burns. ► Show pictures of solid rocket motor grains and discuss how they produce varying thrust levels. 2. Liquid The most common types of liquid propellants we use in liquid rocket engines are called 1. Hypergolic This is a word of Greek origin. It means two materials that ignite on contact without any external aid (like a spark). For the space shuttle, Aerojet produces two kinds of engines that use hypergolic fuels. The Orbital Maneuvering Subsystem (OMS) engines help propel the shuttle into orbit, adjust the orbit as required, and slow the shuttle to allow for reentry and landing. The shuttle reaction control system engines are used for on orbit attitude control. 2. Cryogenic This is a word of Greek origin (kryos) meaning "cold." The three main engines of the space shuttle use liquid hydrogen (fuel) and liquid oxygen (oxidizer), both kept very cold so they will remain liquid.