Adventures in Aerospace: Lesson 2 Volunteer’s Guide

Key to Curriculum Formatting: ► Volunteer Directions ■ Volunteer Notes

♦ Volunteer-led Classroom Experiments

Lesson 2: YOU’RE PLANNING TO LAUNCH A ROCKET! ► Begin the presentation by telling the class that this is “Lesson 2: You’re Planning to Launch 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 Rocketdyne. I 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 • DVD/Presentation • Projector screen/TV

• Balloons

Page 1 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

• Matches/lighter • Small strip of paper • Rolling chair or something a student can easily sit on and be pushed • Candle • Plate or candle holder • Paper (or plastic) bag or paper cup • Handouts • Index cards ► See lesson to assess total equipment needs.

LESSON OUTLINE (NOTE: total time of video is about 1 minute) Introduction Lesson Concepts Vocabulary Balloon and Rocket Comparison Newton’s Laws of Motion • First Law • Second Law • Third Law Comparing and Contrasting Liquid and Solid Propellants Cooling What we use Rockets For Applying What We Have 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

Page 2 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

VOCABULARY Acceleration: Change in an object’s velocity 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

BALLOON AND ROCKET COMPARISON

► 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:

Page 3 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

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 OF MOTION

Sir Isaac Newton had three laws of motion that apply also to rocket flight. • Objects won’t move unless there is some kind of push or pull (force). • A push will make an object speed up until the push is no longer affecting it. • The push of an object will have an equal force against it.

First Law of Motion Objects won’t move unless there is some kind of push or pull (force). 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.)

Rocket Launch

Page 4 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

Like Newton’s first law of motion, a rocket must be pushed to have movement. To exit our atmosphere and the gravitational pull of the Earth, it must be moving at 7 miles per second (about 25,000 miles per hour). ► Show students the video which is a launch from the Apollo mission.

Second Law of Motion A push will make an object speed up until the push is no longer affecting it. 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

Page 5 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide the balloon in the opposite direction. Falling off a roller skate makes the skate go in one direction and the skater in another!)

♦ Newton’s Laws Experiment Experiment Concepts • Newton’s Laws of Motion Experiment Materials • A roller-skate, skate board or rolling chair Experiment Instructions 1. Introduce Isaac Newton's three laws of motion, developed more than 300 years ago (1687). Use the rolling item to illustrate. 2. 1st Law of Motion: Place the rolling item (skate board) in an open space and ask students if the item will move by itself. How about if we push it in a specific direction, what will happen? 3. 2nd Law of Motion: Put more mass on the rolling item. Ask the students to predict the difference in this situation from the one before (aiming for ‘it’s harder to push’). If using a rolling chair, ask a student volunteer to push the chair without the extra mass, then to push it again at the same speed with the extra mass. This shows that you need more force to move a larger mass at the same speed. This means that rockets (for heavy things like space shuttles) need A LOT of force. 4. 3rd Law of Motion: Have two volunteer students come up. One sits in a rolling chair (or something that can move a little when pushed). Ask students to predict the force needed to push a student a certain way while sitting on a chair. Have the student who is standing up push the other student in the indicated direction. Then have the student in the chair push themselves in the indicated direction using the other student, but the standing student isn’t’ allowed to push. Ask students to identify which way they had to push to accomplish this. This shows that forces acted on an object will create forces in the opposite direction. This was also shown with the balloon experiment. By pushing air downwards, the balloon was able to fly. ► Use the following information to explain to the students how Newton's laws relate to launching a rocket. Experiment Explanation 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) the massive rocket (m) off the launch pad. F=ma.

Page 6 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

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. 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.

BURNING BASICS

Page 7 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

Fuels are burned to consume or produce energy. The storage and burning of fuels adds complexity to powering rockets. It takes oxygen, fuel and ignition to start and maintain a fire. Just like the balloon rocket, rockets used for planes and space shuttles use some kind of fuel (or propellent) to provide the force to move. Unlike the balloon rocket, the ones used for planes and space shuttles burn up their fuels.

♦ Burning Basics Experiment Experiment Concepts • Propellants • Newton’s third law of motion Experiment Materials • Small strip of paper • Matches/lighter Experiment Instructions Burn a small strip of paper and ask the students what you need to have fire happen. The students will get the fuel (the paper), oxygen (or air) and they might get that you need a spark or certain amount of energy to start. The rocket carries fuel with it but how will the rocket have oxygen when in space? Students will get that they have to carry oxygen with it.

COMPARING LIQUID AND SOLID PROPELLANTS 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.

Page 8 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

► Show the images of the solid and liquid rockets and discuss advantages and disadvantages of each. 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 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! 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 thrust will change while the propellant burns. 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 Rocketdyne produced 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. They are both "cryogenic" propellants. 3. Monopropellant. A monopropellant contains both fuel and oxidizer within the same molecule. When the

Page 9 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

monopropellant flows over certain materials called catalysts, it decomposes. When it decomposes, hot gas is produced which flows out the rocket engine nozzle producing thrust. One of the biggest problems with liquid rockets is keeping them cool. For example, the Space Shuttle Main Engine (called SSME) burns liquid oxygen and liquid hydrogen. The temperature in the combustion chamber is about 6,000°F which is higher than the melting point of steel. The SSME contains a significant amount of steel. Why doesn't it melt when exposed to temperatures of 6000 degrees Fahrenheit? Let's do an experiment to show how many rocket engines are cooled so they don't melt.

Now that we know something about liquid rocket engines and solid rocket motors, how do they compare? ► Talk with the students about the following properties of liquid rocket engines and solid rocket motors. Liquid propellant rocket engine facts: • Liquid engines are more complicated than solid rocket motors. They contain many more parts. • They contain many moving parts in their turbo pumps, valves, and gearboxes. • They can start and stop multiple times during one flight. • They have a higher specific impulse than solid propellant. This means that the propellant has a better “gas mileage” rating. • Liquid engines can be throttled to increase or decrease thrust as required. Solid propellant rocket motor facts: • Solid propellant rocket motors typically ignite once and burn until solid propellant is consumed in the reaction. • Solid propellant rocket motors are simpler and cheaper to produce. No moving parts. • Thrust profile can be tailored to meet mission requirements by varying grain cross section design.

COOLING

Page 10 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

When burning these fuels, solid or liquid, the tempurature gets really high. It gets so hot that the rocket shell (usually made of some type of steel) can start to melt. ► Talk briefly about the extreme temperatures present in a rocket engine and how we keep the rocket from melting. Then perform the following experiment. ♦ Regenerative Cooling Demonstration Experiment Concepts • Rocket propulsion systems Experiment Materials • Candle • Matches • Plate or candle holder • Paper (or plastic) bag or paper cup Experiment Instructions 1. Light the candle. 2. Put 1.5 inches of water into the bottom of a bag or cup. 3. Put the bag or cup directly over the lit candle. 4. Watch what doesn’t happen! Experiment Explanation This experiment illustrates (in principle) how many liquid rocket engines are kept from melting, as the temperatures inside many liquid rocket engines during combustion are much higher than the melting temperatures of many of the materials used to make the engine. One or both of the rocket engine propellants (fuel or oxidizer) flows through passages in the hottest parts of the rocket engine. The propellant absorbs the heat, keeping the rocket engine itself cool. The propellant is then burned in the combustion chamber. Because the propellant is hot from the regenerative (regen) cooling, it reacts more readily in the combustion chamber.

Page 11 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

ROCKET POWER USES

LET’S REVIEW

QUIZ THE TEACHER (Q & A) ► Hand out index cards to the class and ask them to write down one or two questions for you. Ask for a volunteer to collect the cards. Read some the questions aloud and answer them for the entire class. ► If you and your teacher have set a meeting for the next presentation, let students know what they will be exploring next session:

Page 12 of 13 Adventures in Aerospace: Lesson 2 Volunteer’s Guide

“In the next session, ‘You’re Going to the Moon!,’ your class will learn about past, current and future moon missions, as well as what life would be like on the moon.” ► Thank class.

Page 13 of 13