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October 24, 2011

Center of Mass and Center of Pressure: Engineering a Stable Rocket

Presented by: Rachel Power

NASA Explorer Schools PresentsNASA Explorer Schools PresentsNASA Explorer Schools PresentsNASA Explorer Schools Presents

Outline for Web SeminarOutline for Web SeminarOutline for Web SeminarOutline for Web Seminar

Navigating the GuideNavigating the Guide Navigating the ActivityNavigating the Activity Building a LauncherBuilding a Launcher Building a RocketBuilding a Rocket STEM ConceptsSTEM Concepts Additional ResourcesAdditional Resources

explorerschools.nasa.gov

explorerschools.nasa.gov

explorerschools.nasa.gov

Table of ContentsTable of ContentsTable of ContentsTable of Contents A Pictorial History of RocketsA Pictorial History of Rockets pg 1pg 1 How Rockets WorkHow Rockets Work pg 19pg 19 Applying Newton’s LawsApplying Newton’s Laws pg 24pg 24 National Standards MatrixNational Standards Matrix pg 31pg 31 Suggested Grade LevelsSuggested Grade Levels pg 33pg 33 Additional Explorations Additional Explorations pg 140pg 140

Which civilization is credited Which civilization is credited with the first recorded use of with the first recorded use of

rocket propulsion?rocket propulsion?

Which civilization is credited Which civilization is credited with the first recorded use of with the first recorded use of

rocket propulsion?rocket propulsion?

A. Chinese

B. Russian

C. Greek

D. German

A Picto

rial H

istory

A Picto

rial H

istory

A Picto

rial H

istory

A Picto

rial H

istory

How

Rocke

ts Work

How

Rocke

ts Work

Ap

ply

ing

New

ton

’s Law

sA

pply

ing

New

ton

’s Law

s

Natio

nal S

tandard

s Matrix

Natio

nal S

tandard

s Matrix

Su

gg

este

d G

rade Le

vels

Su

gg

este

d G

rade Le

vels

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questions in the chat!questions in the chat!

Teach

er Pa

ges

Teach

er Pa

ges

Teach

er P

ag

es

Teach

er P

ag

es

Teach

er P

ag

es

Teach

er P

ag

es

Teach

er P

ag

es

Teach

er P

ag

es

Stu

den

t Pag

es

Stu

den

t Pag

es

Calcu

latin

g A

rea

Calcu

latin

g A

rea

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questions in the chat!questions in the chat!

Hig

h-Po

wer La

un

cher

Hig

h-Po

wer La

un

cher

Low costLow cost Parts in plumbing or Parts in plumbing or

hardware storeshardware stores Easy to assemble and useEasy to assemble and use Bicycle pump or air Bicycle pump or air

compressocompressorr

Shoppin

g a

nd A

ssem

bly

Shoppin

g a

nd A

ssem

bly

Pop

! Rocke

t Lau

nch

er

Pop

! Rocke

t Lau

nch

er

Minimal costMinimal cost Even easier to assemble Even easier to assemble

and useand use Parts at plumbing or Parts at plumbing or

hardware storeshardware stores

Shoppin

g a

nd A

ssem

bly

Shoppin

g a

nd A

ssem

bly

Which type of launcher do Which type of launcher do you plan to use?you plan to use?

Which type of launcher do Which type of launcher do you plan to use?you plan to use?

A. High-power launcher

B. Pop! rocket launcher

C. Undecided

Safe

ty P

lan a

nd Tip

sSafe

ty P

lan a

nd Tip

s

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questions in the chat!questions in the chat!

Making B

asic

High-

Making B

asic

High-

Power P

aper

Power P

aper

Rocke

ts

Rocke

ts

EngineeringEngineeringDesignDesignProcessProcess

Mate

rials

Mate

rials

Asse

mb

lyA

ssem

bly

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questions in the chat!questions in the chat!

Sounding Sounding RocketsRockets

Force

s on

a R

ocke

tFo

rces o

n a

Rocke

t

weightweight

thrusthrustt

dragdrag

liftlift

Rocke

t Sta

bility

Rocke

t Sta

bility

center of pressure

center of gravity

x

For simple shapes:For simple shapes: Balance rocket using a Balance rocket using a

string or an edge such as string or an edge such as your finger or meter stickyour finger or meter stick

For simple shapes:For simple shapes: Balance rocket using a Balance rocket using a

string or an edge such as string or an edge such as your finger or meter stickyour finger or meter stick

Finding Center of GravityFinding Center of Gravity

For more complex shapes: Hang the rocket from some point Drop weighted string from point Draw line on rocket along string Repeat from another point Find the point of intersection

For more complex shapes: Hang the rocket from some point Drop weighted string from point Draw line on rocket along string Repeat from another point Find the point of intersection

x

Finding Center of GravityFinding Center of Gravity

x

Trace the shape of rocket on cardboard

Cut out the shape Determine the balance point

Trace the shape of rocket on cardboard

Cut out the shape Determine the balance point

Finding Center of PressureFinding Center of Pressure

ccggW = wW = wnnddnn + w + wbbddbb + w + wffddff

W = wW = wnn + w + wbb + w + wff

ccggW = wW = wnnddnn + w + wbbddbb + w + wffddff

W = wW = wnn + w + wbb + w + wff

Mathematical ApproximationMathematical ApproximationCenter of GravityCenter of Gravity

ccgg = w = wnnddnn + w + wbbddbb + w + wffddff

WW

ccgg = w = wnnddnn + w + wbbddbb + w + wffddff

WW

Mathematical ApproximationMathematical ApproximationCenter of GravityCenter of Gravity

Mathematical ApproximationMathematical ApproximationCenter of PressureCenter of Pressure

ccppA = aA = annddnn + a + abbddbb + a + affddff

A = aA = ann + a + abb + a + aff

ccppA = aA = annddnn + a + abbddbb + a + affddff

A = aA = ann + a + abb + a + aff

ccpp = a = annddnn + a + abbddbb + a + affddff

AA

ccpp = a = annddnn + a + abbddbb + a + affddff

AA

Mathematical ApproximationMathematical ApproximationCenter of PressureCenter of Pressure

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Rocke

t Win

d Tu

nn

el

Rocke

t Win

d Tu

nn

el

Launch

Altitu

de Tra

cker

Launch

Altitu

de Tra

cker

Ad

ditio

nal E

xp

lora

tion

sA

dd

ition

al E

xp

lora

tion

sCalculating AltitudeCalculating Altitude

Advance

d H

igh-Po

wer

Advance

d H

igh-Po

wer

Paper R

ocke

tsPa

per R

ocke

ts

Colla

bora

tion

Colla

bora

tion

Feed

back

Feed

back

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questions in the chat!questions in the chat!

http://explorerschools.nasa.gov

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Zipporah Miller, Associate Executive Director Conferences and Programs

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