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Teacher Background

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Grade 7-10 | 9 (45 min) Classes

In this lesson, students will answer the question, How does the relationship between the center of pressure and the center of gravity affect the stability of a rocket? Working in teams of three, students will be challenged to design and market a rocket prototype to NASA for its Artemis Program that will be stable enough to carry commercial passengers to the Moon.

 

Students will be working for R2 Manufacturing, a company revolutionizing spaceflight and rocket technologies. Their new propulsion technology has been a breakthrough, but development on the airframe has been challenging. Their first attempt veered wildly from the flight path, slammed into the ground and was destroyed. Stability has been a huge concern, and they worry that their latest design will suffer the same fate. Students will be placed into 3 different roles – Head Engineer, Head of Manufacturing, and Program Manager – to provide an independent review, measure and verify the stability of the rocket. They will then provide recommendations for the next design iteration.

 

Through this lesson, students will learn about the center of gravity and center of pressure to hypothesize the best way to have a stable rocket flight. They will then build their first rocket prototype to determine the center of gravity and the center of pressure for their rocket design. They will analyze their own results and the results of their classmates. Following stability tests, they will plan and build a second rocket prototype with a different configuration and identify the center of gravity and the center of pressure of this rocket. Students will make a scientific drawing of a stable rocket, identifying the location of the center of gravity and the center of pressure.

Standards

Targeted Performance Expectation(s):

Next Generation Science Standards (NGSS)

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.

Common Core Standards - English

CCSS.ELA-LITERACY.WHST.6-8.2

Write informative/explanatory texts, including the narration of historical events, scientific procedures/ experiments, or technical processes.

CCSS.ELA-LITERACY.WHST.6-8.2.D

Use precise language and domain-specific vocabulary to inform about or explain the topic.

CCSS.ELA-LITERACY.WHST.6-8.4

Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience.

CCSS.ELA-LITERACY.WHST.6-8.6

Use technology, including the Internet, to produce and publish writing and present the relationships between information and ideas clearly and efficiently.

CCSS.ELA-LITERACY.SL.6.1, SL.7.1, SL.8.1

Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade level topics, texts, and issues, building on others’ ideas and expressing their own clearly.

CCSS.ELA-LITERACY.SL.6.4, SL.7.4, SL.8.4

Present claims and findings, sequencing ideas logically and using pertinent descriptions, facts, and details to accentuate main ideas or themes; use appropriate eye contact, adequate volume, and clear pronunciation.

CCSS.ELA-LITERACY.SL.6.5, SL.7.5, SL.8.5

Include multimedia components (e.g., graphics, images, music, sound) and visual displays in presentations to clarify information.

CCSS.ELA-LITERACY.SL.6.6, SL.7.6, SL.8.6

Adapt speech to a variety of contexts and tasks, demonstrating command of formal English when indicated or appropriate

Vocabulary

CENTER OF GRAVITY

The point in a rocket around which its weight is evenly balanced; the point at which a model rocket will balance on a knife edge.

CENTER OF PRESSURE

The point where the total sum of air pressure forces act on a body.

DRAG

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

FIN

The stabilizing and guiding unit of a model rocket (which should be in a symmetrical form of three, four, or possibly more and made of reinforced paper, balsa, or plastic); an aerodynamic surface projecting from the rocket body for the purpose of giving the rocket directional stability.

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.

MASS

The amount of matter in an object

NOSE CONE

The foremost surface of a model rocket, generally tapered in shape to allow for streamlining, usually made of balsa or plastic.

STABILITY

A stable and safe rocket where the nose of the rocket travels forward and moves in a predictable flight path. For a stable model rocket, the center of pressure should be located below the center of gravity.

THRUST

The propulsive force that moves something forward.

Teacher Background

Forces of Flight

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.

Center of Gravity / Center of Pressure

The basic principle of rocket stability is the center of gravity must be ahead of the center of pressure for the rocket to be stable. The center of gravity (CG) is the point at which the mass of the rocket is balanced because the weight forward from this point is equal to the weight to the rear of this point. (Think of this as balancing a pencil on your finger. The pencil will balance when there is an equal amount of mass on both sides of your finger.) The center of pressure (CP) is the point on the rocket at which half of the aerodynamic surface area is located forward and half to the rear.

 

Fins make the rocket fly straight. A rocket without fins will tumble around its CG (also called the balance point) when flying through the air like a balloon that is inflated and then let go. The balloon will fly erratically because it is uncontrolled. With fins, a rocket has more surface area behind the CG than in front. When the rocket is flying through the air, the air has more surface area to push against behind the balance point than in front because of the greater surface area provided by the fins. Therefore, the rocket tends to stabilize itself. The rocket will rotate until the nose is pointing forward in the air and the fins are pointing backward.

 

If you point a rocket straight up, the CP should be below the CG. This will allow the rocket to have a stable flight. You can accomplish this by adding fins (as noted above) or by adding mass to the front of the rocket meaning if the rocket is pointed upward, the CP should be below the CG. Neutral stability is when the CG and CP are at the same point and the rocket’s flight will be random. If the CP is in front of the CG (in other words, the surface area is greater towards the front or top of the rocket), then the flight will be unstable.

Materials

Each Student Needs:

Student Design Portfolio

Rocket Stability Kit

Glue

Hobby Knife

Safety Goggles

Pencil

Ruler

Cardstock

String (60 cm)

Permanent Marker

Small ball of clay

Colored Pencils, Markers, or Paint

Computer (optional)

The Class Needs:

Unit Plan

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Student Portfolio

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Resources

PowerPoint Presentations

Videos

NASA Artemis Overview – The NASA program that students are designing towards

 

Launch 1

Launch 2

Launch 3

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