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Vocabulary

Teacher Background

Materials
Unit Plan
Student Portfolio
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### Grade 6-8 | 8 (45 min) Classes

In this lesson, students will answer the question, “How does a parachute’s design affect the speed of descent of a model rocket?” The students will read a story about humans living on Mars in the year 2323. They must design a way to allow a rocket from Earth to land safely on their planet, Estesonia, as the rocket is carrying fragile, photovoltaic cells, their alternate energy source.

Students will hypothesize how the design of a parachute affects the speed of descent of a model rocket. After a review of different types of recovery systems, students will practice what they learned and build and test a parachute prototype. After analyzing the data, students will apply what they have learned to build the Green Eggs Rocket and plan the parachute for their flight. They will state a hypothesis and identify the independent and dependent variables.

After the flight, the students will combine their data into a class data chart to allow better analysis. They will compare the results and determine the answer to the essential question, “How does a parachute’s design affect the speed of descent of a model rocket?”.

The student’s final product will be to complete a Claims-Evidence-Reasoning writing piece supporting their final conclusions. A traditional multiple-choice quiz is included for use if desired.

## Next Generation Science Standards (NGSS)

### MS-PS2.1

Apply Newton’s Third Law to design a solution to a problem involving the motion of two colliding objects.

### MS-ETS 1-1

Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

### MS-ETS 1-2

Evaluate competing design solutions based on jointly developed and agreed-upon design criteria using a systematic process to determine how well they meet the criteria and constraints of the problem.

### MS-ETS 1-3

Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

### MS-ETS 1-4

Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.

## Vocabulary

### APOGEE

The peak altitude or highest point of a rocket’s flight.

### DRAG

The aerodynamic force that opposes an aircraft’s motion through the air.

### GRAVITY

Force that pulls everything down toward the center of the Earth.

### LIFT

The force that directly opposes the weight of an aircraft and holds an aircraft in the air.

### PARACHUTE

Drag-producing device, generally hemispherical (halfsphere) in shape. Parachutes used in model rockets are generally made from light plastic and are used to gently recover the payload package, rocket body, etc.

### RECOVERY SYSTEM

A device incorporated into a model rocket for the purpose of returning it to the ground in a safe manner. All model rockets must employ a recovery system (such as a parachute).

Flame resistant tissue packed between the streamer or parachute and model rocket engine protecting the recovery device from hot ejection gases.

### THRUST

The propulsive force that moves something forward.

### VELOCITY

The rate of motion or speed in a given direction. Measured in terms of distance moved per unit time, in a specific direction.

## Teacher Background

### For every action there is an equal and opposite reaction

With rockets, the action is the expelling of gas out of the engine. The reaction is the movement of the rocket in the opposite direction. The rocket is pushed by the escaping gases produced by the chemical reaction of fuel and oxidizer combining in the combustion chamber.

### Parts of a Model Rocket

The main parts of a model rocket are the body tube, engine holder assembly, fins, launch lug, nose cone, shock cord and recovery system. Model rockets are made of lightweight materials like paper, balsa wood, and plastic. The body tube is the main structure of the rocket. It determines the main shape of the rocket and is usually long and slender. All other parts are attached to the body tube. The engine mount holds the engine in place inside the rocket. Fins give directional stability and help the rocket fly straight. The launch lug is the hollow tube that slips over the launch rod. The nose cone is attached to the top of the rocket and is tapered to cut through the air more efficiently and reduce drag. The rubber shock cord, which attaches the nose cone to the body tube so the rocket is recovered in one piece. The recovery system returns the rocket to the ground safely.

### A Typical Model Rocket Flight

Thrust is the upward force that makes a rocket move off the launch pad. This is a demonstration of Newton’s Third Law of Motion: The action of the gas escaping through the engine nozzle leads to the reaction of the rocket moving in the opposite direction. The casing of a model rocket engine contains the propellant. At the base of the engine is the nozzle which is made of a heat-resistant, rigid material. The igniter in the rocket engine nozzle is heated by an electric current supplied by a battery-powered launch controller. The hot igniter ignites the solid rocket propellant inside the engine which produces gas while it is being consumed. This gas causes pressure inside the rocket engine, which must escape through the nozzle. The gas escapes at a high speed and produces thrust.

Located above the propellant is the smoke-tracking and delay element. Once the propellant is used up, the engine’s time delay is activated. The engine’s time delay produces a visible smoke trail used in tracking, but no thrust. The fast moving rocket now begins to decelerate (slow down) as it coasts upward toward peak altitude (apogee).The rocket slows down due to the pull of gravity and the friction created as it moves through the atmosphere. The effect of this atmospheric friction is called drag. When the rocket has slowed enough, it will stop going up and begin to arc over and head downward. This high point or peak altitude is the apogee.

At this point the engine’s time delay is used up and the ejection charge is activated. The ejection charge is above the delay element. It produces hot gases that expand and blow away the cap at the top of the engine. The ejection charge generates a large volume of gas that expands forward and pushes the recovery system (parachute, streamer, helicopter blades) out of the top of the rocket. The recovery system is activated and provides a slow, gentle and soft landing.

To summarize, the steps of the Flight Sequence of a Model Rocket are:

1. Electrically ignited model rocket engines provide rocket liftoff.
2. Model rocket accelerates and gains altitude.
3. Engine burns out and the rocket continues to climb during the coast phase.
4. Engine generates tracking smoke during the delay/coast phase.
5. Rocket reaches peak altitude (apogee). Model rocket ejection charge activates the recovery system.
6. Recovery systems are deployed. Parachutes and streamers are the most popular recovery systems used.
7. Rocket returns to Earth.
8. Rocket touchdown! Replace the engine, igniter, igniter plug and recovery wadding. Rocket is ready to launch again!

### Recovery Systems

Various recovery systems are used depending on rocket size and weight. While this lesson focuses on the streamer as a recovery system, the systems used in Estes model rockets include:

• Break-Apart – Recovery is accomplished by the rocket separating in the middle and free falling back to the ground.
• Featherweight – Used strictly for light rockets. When the ejection charge activates, the engine is ejected, and the rocket falls lightly to the ground.
• Glide – The engine’s ejection charge converts the rocket into a glider by separating the glider from the booster rocket. The glider’s wings then generate lift, allowing it to settle slowly to the ground.
• Helicopter – Vanes on the rocket are activated when the ejection charge fires. Lift is created when the vanes rotate and the rocket settles slowly to the ground.
• Tumble – The center of gravity is shifted behind the center of pressure. (The center of gravity is the point where the rocket balances evenly. The center of pressure is the point where the aerodynamic forces are evenly distributed.) Tumble can be accomplished by allowing the ejection charge to push the engine casing backwards, but not out of the rocket. The rocket is unstable and tumbles end over end producing high drag which slows the rocket as it falls. This method is often used for recovering lower stages of multi-stage rockets.
• Parachute – The parachute is the most common form of recovery. Drag is produced by the parachute to slow the rocket. The parachute is attached to both the nose cone and the body tube. Flame-resistant recovery wadding must be placed between the engine and the parachute. If wadding is not placed in the rocket, the engine could melt or burn holes into the parachute.
• Streamer – A streamer is attached to the rocket and ejected by the ejection charge. It whips through the air causing drag to slow the rocket. The larger the streamer, the slower the rocket descends.

## Materials

### Each Student Needs:

Student Design Portfolio

Safety Goggles

Tape

Scissors

Plastic Grocery Bag

Ruler

String/ Dental Floss (about 4 feet)

Toothpick

Market/Highlighter or Small Toy

### The Class Needs:

Rocket Recovery Slide Presentation
Stopwatch
Meter Sticks
Green Eggs Bulk Pack
C11-3 Engines
Pocket Lab
Glue
Hobby Knife
Camera (optional)