Grade 6-8 | 8 (45 min) Classes
In this lesson, students will aim their rockets for the Moon! They will be challenged to launch a rocket that will reach an altitude of 800 feet- no more, no less. Students will take on the role of engineers for NASA who must choose the appropriate fuel supply for a rocket destined to the Moon.
Students will hypothesize how the thrust of the engine will affect the rocket’s apogee – highest altitude it reaches. After a review of the four forces of flight, students will practice using the Mini AltiTrak™, an altitude tracking device. After analyzing the data, students will apply those learnings to build an Estes Rocket and analyze its 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 for better analysis. They will compare the results and determine the answer to the essential question, How does the thrust of a model rocket engine affect the altitude of the rocket’s flight?
The student’s final product will be to complete a Choice Project. Details and a rubric are included. An optional Multiple-Choice Assessment is also provided.
Targeted Performance Expectation(s):
Next Generation Science Standards (NGSS)
Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.
Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.
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.
Common Core Standards - Math
Write and evaluate numerical expressions involving whole-number exponents.
Use variables to represent two quantities in a real-world problem that change in relationship to one another.
Giving quantitative measures of center (median and/or mean) and variability (interquartile range and/or mean absolute deviation), as well as describing any overall pattern and any striking deviations from the overall pattern with reference to the context in which the data were gathered.
Compute unit rates associated with ratios of fractions, including ratios of lengths, areas and other quantities measured in like or different units.
Recognize and represent proportional relationships between quantities.
Decide whether two quantities are in a proportional relationship.
Identify the constant of proportionality (unit rate) in tables, graphs, equations, diagrams, and verbal descriptions of proportional relationships.
Apply properties of operations as strategies to add, subtract, factor, and expand linear expressions with rational coefficients.
Understand that rewriting an expression in different forms in a problem context can shed light on the problem and how the quantities in it are related.
Solve multi-step real-life and mathematical problems posed with positive and negative rational numbers in any form (whole numbers, fractions, and decimals), using tools strategically.
Use functions to model relationships between quantities.
Describe qualitatively the functional relationship between two quantities by analyzing a graph.
Use trigonometric ratios and the Pythagorean Theorem to solve right triangles in applied problems.
The rate at which an object increases its speed.
The height or vertical distance of an object as measured from the ground.
ALTITUDE MEASURING DEVICE
An instrument used to measure the altitude or height of an object.
The angle between two objects as seen by an observer.
The peak altitude or highest point of a rocket’s flight.
The reduction in speed, to slow down (the opposite of acceleration).
The aerodynamic force that opposes an aircraft’s motion through the air.
A push or pull upon an object resulting from the object’s interaction with another object.
Force that pulls everything down toward the center of the Earth.
The force that directly opposes the weight of an aircraft and holds an aircraft in the air.
A gravity protractor used to determine the height of a rocket flight from the angle of the user’s body to the apogee of the rocket flight.
TANGEANT OF ANGLE
A trigonometric ratio in a right triangle calculated as the length of the opposite side of an angle divided by the length of the adjacent side of the same angle.
The propulsive force that moves something forward.
This is an altitude prediction, data collection and calculation activity. Students should be familiar with how a model rocket launches and all safety procedures that should be followed. The safety requirements can be found in the Model Rocket Safety Code of the National Association of Rocketry (NAR).
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: “For every action there is an equal and opposite reaction.” 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. The rocket can now be prepared for another launch.
To summarize, the steps of the Flight Sequence of a Model Rocket are
- Electrically ignited model rocket engines provide rocket liftoff.
- Model rocket accelerates and gains altitude.
- Engine burns out and the rocket continues to climb during the coast phase.
- Engine generates tracking smoke during the delay/coast phase.
- Rocket reaches peak altitude (apogee). Model rocket ejection charge activates the recovery system.
- Recovery systems are deployed. Parachutes and streamers are the most popular recovery systems used.
- Rocket returns to Earth.
- Rocket touchdown! Replace the engine, igniter, igniter plug and recovery wadding. Rocket is ready to launch again!
Sir Isaac Newton
What is known about rocketry today can be traced back to the time of Sir Isaac Newton (1642 – 1727). Newton described the motion of objects falling to the Earth in his book Philosophiae Naturalis Principia Mathematica where he outlined three laws of motion. Although Newton was merely describing principles of nature, Newton’s Laws apply to the physics of rocketry. His laws are simple statements regarding the physics governing motion and can be used to provide precise explanations of rocket flight.
Newton's First Law of Motion
Objects at rest will remain at rest and objects in motion will remain in motion in a straight line unless acted upon by an unbalanced force
During a model rocket flight, forces become balanced and unbalanced all the time. A rocket on the launch pad is in a state of rest. This is called inertia. A rocket is balanced all the time because the surface of the pad pushes the rocket up while the force of gravity tries to pull it down. An unbalanced force must be exerted for a rocket to lift-off from the launch pad. A rocket blasting off the launch pad changes from a state of rest to a state of motion. It will keep moving in a straight line at the same speed unless it is acted upon by an unbalanced force (gravity and drag).
There are four forces (drag, gravity, thrust, lift) that act on all objects that travel through the air. Drag and gravity are the two unbalanced forces that act on a model rocket. Drag is the resistance or frictional force between the surface of a moving object and air. Drag increases with speed. Gravity is the force pulling an object back to the surface of the Earth. The amount of this force is proportional to the mass of the object.
When the rocket lifts off the launch pad it is guided by the launch rod in a straight line upward. The unbalanced forces (drag and gravity) cause it to arch and fall to the ground.
Newton's Second Law of Motion
Force is equal to mass times acceleration. (F = ma)
The amount of thrust (force produced by a rocket engine) will be determined by the mass of gases created and how fast the gas escapes the rocket. The greater the rate at which the rocket fuel is burned and the faster the velocity of the escaping gas, the greater the thrust of the rocket engine.
Newton's Third Law of Motion
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.
Each Student Needs:
Student Design Portfolio
Tennis Ball (or other small ball)
Estes Rocket Kit
The Class Needs:
How Does a Model Rocket Fly? Slide Presentation
What Are Model Rocket Engines? Slide Presentation
How to use a Mini Altitrak
Blast Off Flight Pack
Opaque Box for Engines
Pocket Lab (optional)
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