Lecture on Water Rocket

7/29/2019 Lecture on Water Rocket

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Waterrocketuseswaterasapropellant.


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Itisbasedonthe

NEWTONS THIRD LAW OF MOTION.

For a simple model, water rocket

consists

of

a

bottle

having

water

above

which there is pressurized air. On

launching, air pushes the water outside

providing the rocket an upward thrust.

PRINCIPLE


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Awaterrockethastwomainparts.


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BODY

1.Bodyofawaterrocket canbeassimpleas

asingle2lsoftdrinkbottleandalsoascomplex

asabodyofamultistagerocket.

2.Toachievegreatervolumeandaerodynamic

stability,twoormorebottlescanbe

splicedi.e.joinedtogetherasshowninthe

figurebelow.


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FINSWhydorocketshavefins?

1.Thepurposeofputtingfinsonarocketisto

providestability

during

flight,

that

is,

to

allow

therockettomaintainitsorientationand

intendedflightpath.

2.Finsaresymmetricallyplacedaroundthe

body(threeorfour),withenoughareaso

thatwhentherockettipsoffofitspatha

littlebit,thefinsprovideaerodynamicforce

toputitstraightagain.

3. Morethanfourfinsadddragandweight.


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Drag

> >

NOSE CONE1.Theconeisshapedtooffer

minimumaerodynamicresistance.

2.Itconsists

of

simply

top

portion

ofacolddrinkbottle.


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NOZZLE1. Nozzleservesthepurposeof

controllingthethrustprovidedbywater.

2.Smallerdiameternozzlescanbeusedtoprolongthetime

offlightbyreducedexhaust

rate.3.Inourcase,wewillhavea

fixedsize.Themouthofthebottlewillactasanozzle.


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LAUNCHERItactsasameanstopressurizetherocketwithair

andas

abase

to

provide

support

to

the

rocket

before

launch.


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MAKING OF A LAUNCHER


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CABLE TIES1. Theyhelptoholddownthe

rocketwhilefillingtheair.

2. Thecollarisapipethatcanslide

overtheinnerpipe.Whenpushed

up,itwillclosethecableties.(They

arein

open

position

in

the

above

pic).Whenclosed,theywillhold

thebottleandwillnotallowitto

movewhile

pressurizing.

The

collar

ispulleddowntoreleasethebottle

whendesiredpressureisreached.


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RELEASE MECHANISM


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PARACHUTETherocketusesaparachutetoincreasedragtoslowits

descent.

Ithelpsinthesmoothlandingoftherocketafterthefuelis

over.

Theparachuteisgenerallykeptinsidethenoseconebefore

launch.

Afterattaining

the

apogee

the

nose

cone

separates

from

the

rocketreleasingtheparachute.


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WORKING

Awater

rocket

works

using

the

sameprinciplesasotherrockets.

Therearethreemainforcesin

action:thrust(Fapp),drag(Ffr)and

weight(w=mg).

The

water,

which

is

forcedoutbythedifference

betweeninternalandatmospheric

pressure,is

areaction

mass

that

providesthethrust.


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Whenawaterrocketislaunched,the

differencebetweeninternaland

atmosphericpressures

forces

the

rocketoffthepressureseal,followed

bytheexpulsionofwaterandairout

ofthe

nozzle

until

the

internal

and

atmosphericpressuresareequalized.

Thisactioncreatesadownward

force,by

applying

Newtons

Third

LawofMotion.


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Pumpingair

into

the

bottleincreasesitspressure

Eventuallythe

nozzle

is

pushedoutallowingthewatertoescape

Theair

pushes

the

water

downwhichmeansthe

waterpushesitback.Thisforceisthentransferredtotherocket.


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Arocket'sstabilityiscriticalfor

achievinghigh

altitude

flights

an

unstablerocketwillgoupabout50

feet(max.)andthenflutterback

downtotheground.

STABILITY

Theruleisknownasthe

alphabeticalstabilityruleand

statesthat

G

comes

before

P(in

thealphabet).Fromthetopofthe

rocket,theCGcomesbeforethe

CP.


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Wecall

the

average

location

of

the

pressurevariationthecenterofpressureinthesamewaythatwe

callthe

average

location

of

theweightofanobjectthecenter

ofgravity.Theaerodynamicforces

liftanddrag actthroughthe

centerof

pressure

in

flight.

CentreOfPressure


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Thisis

because

the

aerodynamic

forcescenteredatthecenterofpressureareinthe

directionoftherelativewind(theoppositedirection

oftherocket).Iftherocketismovingup,the

aerodynamicforces

are

pushing

down

onit.Ifthecenterofpressureislocatedaftofthe

centerofgravity,theaerodynamicforceswillworkto

pull

the

bottom

of

the

rocket

backinlinewiththerelativewind,pointingtherocket

backinthedirectionoftherelativewind.Thismakesa

stablerocket.Ifthecenterofpressurewereforward

ofthe

center

of

gravity,

the

opposite

would

happen.

Theaerodynamicforceswouldpullthenoseinthe

oppositedirectionthatitshouldmove,causingthe

rockettospinoutofcontrolanunstablerocket.


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FLYING HIGHER

Usehigherpressuresbutinsafelimits(100psi)Keepweighttoaminimum.Increaserocketvolume.Streamlinethebodyoftherockettoreducedrag.Usetherightamountofwater(30to40%)Streamlinetheleadingandtrailingedgesofyourfins.


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WATER ROCKET WITH

BOOSTERS1.Oneofthepossiblemodificationsinthesimplewaterrocketis

makingwater

rocket

with

boosters.

2.Inourcase,inadditiontomainstage,wehavethree

dropawayboostersattachedwithittoincreasethe

launchvelocity

in

order

to

achieve

agreater

altitude.

3.Whenthewaterintheboostersrunsout,they

automaticallygetdetachedfromthemainbody,allowing

ittogomuchhighereasily.

4.We

are

going

to

attach

the

boosters

at

an

angle

of

120

degreestooneanothertomaketherocketstableduring

theflight.


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The 2004 w or ld record a l t i t ude for a w a te r bot t le rock e t

i s more than 300 met e rs .

The max imum a i r speed fo r a w a te r rocke t has been

c loc ked a t up t o 200 km /h

SOME PICS OF OUR BOOSTER WATER


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Pictureodf

main

stage

SOME PICS OF OUR BOOSTER WATER

ROCKET


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Photoof

components


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Contacts:-

Jeetesh Agrawal : 9795669413

Kratika Agrawal : 9616354932

Tushar Sikroria : 9450683065

http://students.iitk.ac.in/aeromodelling


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Lecture on Water Rocket

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