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AUTHOR Vogt, Gregory L.; Rosenberg, Carla R., Ed.TITLE Rockets: Physical Science Teacher's Guide with

Activities.INSTITUTION National Science Foundation, Washington, DC.

Directorate for Education and Human Resources.REPORT NO EP-291PUB DATE Jul 93NOTE 50p.

PUB TYPE Guides Classroom Use Teaching Guides (ForTeacher) (052) Tests/Evaluation Instruments (160)

EDRS PRICE MF01/PCO2 Plus Postage.DESCRIPTORS Elementary Education; Elementary School Science;

Integrated Activities; Mathematics Education;*Physical Sciences; *Science Activities; ScienceEducation; Scientific Concepts; Teaching Guides;Technology Education

IDENTIFIERS Hands On Science; *Rockets

ABSTRACTRockets have evolved from simple tubes filled with

black powder into mighty vehicles capable of launching a spacecraftout into the galaxy. The guide begins with background informationsections on the history of rocketry, scientific principles, andpractical rocketry. The sections on scientific principles andpractical rocketry are based on Isaac Newton's Three Laws of Motion.These laws explain why rockets work and how to make them moreefficient. These sections are followed with a series of physicalscience activities that demonstrate the basic science of rocketry.Each activity is designed to be simple and take advantage ofinexpensive materials. Construction diagrams, material and toolslists, and instructions are included. A brief discussion elaborateson the concepts covered in the activities and is followed withteaching notes and discussion questions. Because many of theactivities and demonstrations apply to more than one subject area, amatrix chart has been included to assist in identifying opportunitiesfor extended learning experiences. The chart identifies these subjectareas (e.g., chemistry, history) by activity and demonstration title.Many of the student activities encourage student problem-solving andcooperative learning. The length of time involved for each activityand demonstration will vary according to its degree of difficulty andthe development level of the students. Generally, demonstrations willtake just a few minutes to complete and most activities can becompleted in less than an hour. The guide concludes with a glossaryof terms, suggested reading list, NASA educational resources, and anevaluation questionnaire. (ZWH)

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REST COPY ORME

ROCKETSPhysical Science Teacher's Guide

with Activities

National Aeronautics and Space Administration

Office of Human Resources and EducationEducation Division

This publication is in the Public Domain and is not protected by copyright.Permission is not required for duplication.

EP-291 July 1993

0cl

Acknowledgments This publication was developed for theNational Aeronautics and Space Administra-tion with the assistance of the many educa-

tors of the Aerospace Education ServicesProgram, Oklahoma State University.

Writer:

Gregory L. Vogt, Ed.D.Teaching From Space ProgramNASA Johnson Space CenterHouston, TX

Editor:

Carla R. RosenbergTeaching From Space ProgramNASA HeadquartersWashington, DC

/ 4

Table of Contents How To Use This Guide1

Activities and Demonstration Matrix 2

Brief History of Rockets 3

Rocket Principles 8

Practical Rocketry 12

Activities and Demonstrations 19

Glossary 40

NASA Educational MaterialsAnd Suggested Readings 41

NASA Educational Resources 42

Evaluation Card Insert

i i

5

How To Use This Guide R ockets are the oldest form of self-containedveNcles in existence. Early rockets were in use

more than two thousand years ago. Over a long and

exciting history, rockets have evolved from simpletubes filled with black powder into mighty vehiclescapable of launching a spacecraft out into the galaxy.Few experiences can compare with the excitement andthrill of watching a rocket-powered vehicle, such as theSpace Shuttle, thunder into space. Dreams of rocketflight to distant worlds fire the imagination of bothchildren and adults.

With some simple and inexpensive materials, youcan mount an exciting and productive physical science

unit about rockets for children, even if you don't knowmuch about rockets yourself. The unit also hasapplications for art, chemistry, history, mathematics,and technology education. The many activitiescontained in this teaching guide emphasize hands-oninvolvement. It contains background information aboutthe history of rockets and basic rocket science to makeyou an "expert."

The guide begins with background informationsections on the history of rocketry, scientific principles,and practical rocketry. The sections on scientificprinciples and practical rocketry are based on IsaacNewton's Three Laws of Motion. These laws explainwhy rockets work and how to make them more

efficient.The background sections are followed with a series

of physical science activities that demonstrate thebasic science of rocketry. Each activity is designed tobe simple and take advantage of inexpensivematerials. Construction diagrams, material and toolslists, and instructions are included. A brief discussionelaborates on the concepts covered in the activitiesand is followed with teaching notes and discussionquestions.

Because many of the activities anddemonstrations apply to more than one subjectarea, a matrix chart has been included on thispage to assist in identifying opportunities forextended learning experiences. The chartidentifies these subject areas by activity andaemonstration title. In addition, many of thestudent activities encourage student problem-solving and cooperative learning. For example,students can use problem-solving to come upwith ways to attach fins in the Bottle Rocketactivity. Cooperative learning is a necessity inthe Altitude Tracking and Balloon Stagingactivities.

1

The length of time involved for each activityand demonstration will vary according to its degreeof difficulty and the development level of thestudents. Generally, demonstrations will take justa few minutes to complete. With the exception ofthe Altitude Tracking activity, most activities can becompleted in less than an hour.

The guide concludes with a glossary of terms,suggested reading list, NASA educationalresources, and an evaluation questionnaire with amailer.

2

A Note on Measurement

In developing this guide, metric units ofmeasurement were employed. In a few exceptions,notably within the "materials needed" lists, Englishunits have been listed. In the United States, metric-sized parts such as screws and wood stock are notas accessible as their English equivalents.Therefore, English units have been used to facilitateobtaining required materials.

Activities and Demonstrationsby Subject Area and Relationship to

Newton's Laws of Motion

Hero Engines

Rocket Pinwheel

Rocket Car

Water Rocket

Bottle Rocket

Newton Car

Antacid Tablet Race

Paper Rockets

Pencil "Rocket"

Balloon Staging

Altitude Tracking

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36

Brief History ofRockets

TIoday's rockets are remarkable collections ofhuman ingenuity. NASA's Space Shuttle, for

example, is one of the most complex flyingmachines ever invented. It stands upright on alaunch pad, lifts off as a rocket, orbits Earth as aspacecraft, and returns to Earth as a glidingairplane. The Space Shuttle is a true spaceship. Ina few years it will be joined by other spaceships.The European Space Agency is building theHermes and Japan is building the HOPE. Still latermay come aerospace planes that will take off fromrunways as airplanes, fly into space, and return asairplanes.

The rockets and spaceships of today andthe spaceships of the future have their roots in thescience and technology of the past. They arenatural outgrowths of literally thousands of years ofexperimentation and research on rockets and rocketpropulsion.

One of the first devices to successfullyemploy the principles essential to rocket flight was

a wooden bird. In the writings of Aulus Gellius,0"" r) a Roman, there is a story of a Greek named

1(0 Archytas who lived in the city of Tarentum,t y now a part of southern Italy. Somewhere

around the year 400 B.C., Archytasmystified and amused the citizens of

Tarentum by flying a pigeon made of wood. Itor appears tha' the bird was suspended on wires

and propelled along by escaping steam. Thepigeon used the action-reaction principle that wasnot to be stated as a scientific law until the 17thcentury.

About three hundred years after the pigeon,another Greek, Hero of Alexandria, inventeda similar rocket-like device called anaeolipile. lt, too, used steam as a propulsivegas. Hero mounted a sphere on top of awater kettle. A fire below the kettle turned

the water into steam, and the gas traveledthrough pipes to the sphere. Two L-shaped tubeson opposite sides of the sphere allowed the gas toescape, and in doing so gave a thrust to the spherethat caused it to rotate.

Just when the first true rockets appeared isunclear. Stories of early rocket like devicesappear sporadically through the historical recordsof various cultures. Perhaps the first true rocketswere accidents. In the first century A.D., theChinese were reported to have had a simple

form of gunpowder made from saltpeter,sulfur, and charcoal dust. It was usedmostly for fireworks in religious and other

festive celebrations. Bamboo tubes were filled withHero Engine

3

the mixture and tossed into fires to createexplosions during religious festivals. It is entirelypossible that some of those tubes failed to explodeand instead skittered out of the fires, propelled bythe gases and sparks produced by the burninggunpowder.

It is certain that the Chinese began toexperiment with the gunpowder-filled tubes. Atsome point, bamboo tubes were attached to arrowsand launched with bows. Soon it was discoveredthat these gunpowder tubes could launchthemselves just by the power produced from the

NUM. )rr

Chinese Fire-Arrows

escaping gas. The true rocket was born.The first date we know true rockets were

used was the year 1232. At this time, the Chineseand the Mongols were at war with each other.During the battle of Kai-Keng, the Chinese repelledthe Mongol invaders by a barrage of "arrows offlying fire." These f;:e-arrows were a simple form ofa solid-propellant rocket. A tube, capped at oneend, was filled with gunpowder. The other end wasleft open and the tube was attached to a long stick.When the powder was ignited, the rapid burning ofthe powder produced fire, smoke, and gas thatescaped out the open end and produced a thrust.The stick acted as a simple guidance system thatkept the rocket headed in one general direction as itflew through the air. It is not clear how effectivethese arrows of flying fire were as weapons ofdestruction, but their psychological effects on theMongols must have been formidable.

Chinese soldier launches fire-arrow

4

Following the battle of Kai-Keng, theMongols produced rockets of their own and mayhave been responsible for the spread of rockets toEurope. All through the 13th to the 15th centuriesthere were reports of many rocket experiments. InEngland, a monk named Roger Bacon worked onimproved forms of gunpowder that greatly increasedthe range of rockets. In France, Jean Froissartfound that more accurate flights could be achievedby launching rockets through tubes. Froissart's ideawas the forerunner of the modern bazooka. Joanesde Fontana of Italy designed a surface-runningrocket-powered torpedo for setting enemy ships onfire.

By the 16th century rockets fell into a time of

Surface-Running Torpedo

disuse as weapons of war, though they were stillused for fireworks displays, and a German fireworksmaker, Johann Schmid lap, invented the "steprocket," a multi-staged vehicle for lifting fireworks tohigher altitudes. A large sky rocket (first stage)carried a smaller sky rocket (second stage). Whenthe large rocket burned out, the smaller onecontinued to a higher altitude before showering thesky with glowing cinders. Schmid lap's idea is basicto all rockets today that go into outer space.

Nearly all uses of rockets up to this timewere for warfare or fireworks, but there is aninteresting old Chinese legend that reported the useof rockets as a means of transportation. With thehelp of many assistants, a lesser-known Chineseofficial named Wan-Hu assembled a rocket-powered flying chair. Attached to the chair weretwo large kites, and fixed to the kites were forty-seven fire-arrow rockets.

On the day of the flight, Wan-Hu sat himselfon the chair and gave the command to light therockets. Forty-seven rocket assistants, each armedwith torches, rushed forward to light the fuses. In amoment, there was a tremendous roaraccompanied by billowing clouds of smoke. Whenthe smoke cleared, Wan-Hu and his flying chairwere gone. No one knows for sure what happenedto Wan-Hu, but it is probable that if the event reallydid take place, Wan-Hu and his chair were blown topieces. Fire-arrows were as apt to explode as to fly.

9

Legendary Chinese official Wan Hu braceshimself for "liftoff"

Rocketry Becomes a Science

During the latter part of the 17th century, thescientific foundations for modern rocketry were laid

by the great English scientist Sir Isaac Newton(1642-1727). Newton organized his understandingof physical motion into three scientific laws. Thelaws explain how rockets work and why they areable to work in the vacuum of outer space.(Newton's three laws of motion will be explained in

detail later.)Newton's laws soon began to have a

practical impact on the design of rockets. About1720, a Dutch professor, Willem Gravesande, builtmodel cars propelled by jets of steam. Rocketexperimenters in Germany and Russia beganworking with rockets with a mass of more than 45kilograms. Some of these rockets were so powerfulthat their escap;ng exnaust flames bored deepholes in the ground even before lift-off.

During the end of the 18th century and earlyinto the 19th, rockets experienced a brief revival asa weapon of war. The success of Indian rocketbarrages against the BritiGh in 1792 and again in1799 caught the interest of an artillery expert,Colonel William Congreve. Congreve set out todesign rockets for use by the British military.

The Congrdve rockets were highlysuccessful in battle. Used by British ships to poundFort McHenry in the War of 1812, they inspiredFrancis Scott Key to write "the rockets' red glare,"words in his poem that later became The Star-Spangled Banner.

Even with Congreve's work, the accuracy ofrockets still had not improved much from the earlydays. The devastating nature of war rockets was

not their accuracy or power, but their numbers.During a typical siege, thousands of them might befired at the enemy. All over the world, rocketresearchers experimented with ways to improveaccuracy. An Englishman, William Hale, developed

a technique called spin stabilization. In this method,the escaping exhaust gases struck small vanes at

the bottom of the rocket, causing it to spin much as

a bullet does in flight. Variations of the principle arestill used today.

Rockets continued to be used with successin battles all over the European continent.However, in a war with Prussia, the Austrian rocketbrigades met their match against newly designedartillery pieces. Breech-loading cannon with rifledbarrels and exploding warheads were far moreeffective weapons of war than the best rockets.Once again, rockets were relegated to peacetime

uses.

Modern Rocketry Begins

In 1898, a Russian schoolteacher,Konstantin Tsiolkovsky (1'157-1935), proposed theidea of space exploration by rocket. In a report hepublished in 1903, Tsiolkovsky suggested the use of

liquid propellants for rockets in order to achievegreater range. Tsiolkovsky stated that the speedand range of a rocket were limited only by theexhaust velocity of escaping gases. For his ideas,

careful research, and great vision, Tsiolkovsky hasbeen called the father of modern astronautics.

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Tsiolkovsky Rocket Designs

5

Early in the 20th century, an American,Robert H. Goddard (1882-1945), conductedpractical experiments in rocketry. He had becomeinterested in a way of achieving higher altitudesthan were possible for lighter-than-air balloons, Hepublished a pamphlet in 1919 entitled A Method ofReaching Extreme Altitudes, It was a mathematicalanalysis of what is today called the meteorologicalsounding rocket.

In his pamphlet, Goddard reached severalconclusions important to rocketry. From his tests,he stated that a rocket operates with greaterefficiency in a vacuum than in air. At the time, mostpeople mistakenly believed that air was needed fora rocket to push against and a New York Timesnewspaper editorial of the day mocked Goddard'slack of the "basic physics ladled out daily in our highschools." Goddard also stated that multistage orstep rockets were the answer to achieving highaltitudes and that the velocity needed to escapeEarth's gravity could be achieved in this way.

Goddard's earliest experiments were withsolid-propellant rockets. In 1915, he began to tryvarious types of solid fuels and to measure theexhaust velocities of the burning gases.

ROCXET MOTOR

GASOLINE LINE

PRESSURERELIEF

VENT

LIQUIDOXYGEN

TANK

IGNITER

NEEDLEVALVES

LIQUIDOXYGEN LINE

HINGED ROD

EXHAUST SHIELD

GASOLINETANK

PULL CORD

DETACHABLESTARTING

HOSE

PIPE

ALCOHOLBURNER

Dr. Goddard's 1926 Rocket

6

OXYGEN

CYLINDER

While working on solid-propellant rockets,Goddard became convinced that a rocket could bepropelled better by liquid fuel. No one had ever builta successful liquid-propellant rocket before. It wasa much more difficult task than building solid-propellant rockets. Fuel and oxygen tanks,turbines, and combustion chambers would beneeded. In spite of the difficulties, Goddardachieved the first successful flight with a liquid-propellant rocket on March 16, 1926. Fueled byliquid oxygen and gasoline, the rocket flew for onlytwo and a half seconds, climbed 12.5 meters, andlanded 56 meters away in a cabbage patch. Bytoday's standards, the flight was unimpressive, butlike the first powered airplane flight by the Wrightbrothers in 1903, Goddard's gasolinejocket was theforerunner of a whole new era in rocket flight.

Goddard's experiments in liquid-propellantrockets continued for many years. His rocketsbecame bigger and flew higher. He developed agyroscope system for flight control and a payloadcompartment for scientific instruments. Parachuterecovery systems were employed to return rocketsand instruments safely. Goddard, for hisachievements, has been called the father of modernrocketry.

A third great space pioneer, HermannOberth (1894-1989) of Germany, published a bookin 1923 about rocket travel into outer space. Hiswritings were important. Because of them, manysmall rocket societies sprang up around the world.In Germany, the formation of one such society, theVerein fur Raumschiffahrt (Society for SpaceTravel), led to the development of the V-2 rocket,which was used against London during World WarII. In 1937, German engineers and scientists,including Oberth, assembled in Peenemunde on theshores of the Baltic Sea. There the most advancedrocket of its time would be built and flown under thedirectorship of Wernher von Braun.

The V-2 rocket (in Germany called the A-4)was small by comparison to today's rockets. Itachieved its great thrust by burning a mixture ofliquid oxygen and alcohol at a rate of about one tonevery seven seconds. Once launched, the V-2 wasa formidable weapon that could devastate wholecity blocks.

Fortunately for London and the Allied forces,the V-2 came too late in the war to change itsoutcome. Nevertheless, by war's end, Germanrocket scientists and engineers had already laidplans for advanced missiles capable of spanningthe Atlantic Ocean and landing in the United States.These missiles would have had winged upperstages but very small payload capacities.

1 1

With the fall of Germany, many unused V-2rockets and components were captured by theAllies. Many German rocket scientists came to theUnited States. Others went to the Soviet Union.The German scientists, including Wernher vonBraun, were amazed at the progress Goddard hadmade.

Both the United States and the Soviet Unionrealized the potential of rocketry as a militaryweapon and began a variety of experimentalprograms. At first, the United States began aprogram with high-altitude atmospheric soundingrockets, one of Goddard's early ideas. Later, avariety of medium- and long-range intercontinentalballistic missiles were developed. These becamethe starting point of the U.S. space program.Missiles such as the Redstone, Atlas, and Titanwould eventually launch astronauts into space.

On October 4, 1957, the world was stunnedby the news of an Earth-orbiting artificial satellitelaunched by the Soviet Union, Called Sputnik I, thesatellite was the first successful entry in a race forspace between the tw-, superpower nations. Lessthan a month later, the Soviets followed with thelaunch of a satellite carrying a dog named Laika onboard. Laika survived in space for seven daysbefore being put to sleep before the oxygen supplyran out.

A few months after the first Sputnik, theUnited States followed the Soviet Union with asatellite of its own. Explorer I was launched by theU.S. Army on January 31, 1958. In October of thatyear, the United States formally organized its spaceprogram by creating the National Aeronautics andSpace Administration (NASA). NASA became acivilian agency with the goal of peaceful explorationof space for the benefit of all humankind.

Soon, many people and machines werebeing launched into space. Astronauts orbitedEarth and landed on the Moon. Robot spacecrafttraveled to the planets. Spare was suddenlyopened up to exploration ar i commercialexploitation. Satellites enabled scientists toinvestigate our world, forecast the weather, and tocommunicate instantaneously around the globe. Asthe demand for more and larger payloads increased,a wide array of powerful and versatile rockets had tobe built.

Since the earliest days of discovery andexperimentation, rockets have evolved from simplegunpowder devices into giant vehicles capable oftraveling into outer space. Rockets have opened theuniverse to direct exploration by humankind.

Container forturbine propellant(hydrogen peroxide)

Warhead (Explosivecharge)

Automatic gyro control

Guidebeam and radiocommand receivers

Container foralcohol-water

mixture

Container forliquid oxygen

Propellant turbopump

Vaporizer for turbinepropel'ant (propellantturbopump drive)

Oxygen mainvalve

Rocket motor

12

Jet vane Air vane

German V-2 (A-4) Missile

Steamexhaust

from turbine

Alcohol mainvalve

7

Rocket Principles

8

Outside Air Pressure

Arocket in its simplest form is a chamber enclosinga gas under pressure. A small opening at one

end of the chamber allows the gas to escape, and indoing so provides a thrust that propels the rocket inthe opposite direction. A good example of this is aballoon. Air inside a balloon is compressed by theballoon's rubber walls. The air pushes back so thatthe inward and outward pressing forces are balanced.When the nozzle is released, air escapes through itand the balloon is propelled in the opposite direction.

When we think of rockets, we rarely think ofballoons. Instead, our attention is drawn to the giantvehicles that carry satellites into orbit and spacecraft tothe Moon and planets. Nevertheless, there is a strongsimilarity between the two. The only significantdifference is the way the pressurized gas is produced.

With space rockets, the gas is produced by burningpropellants that can be solid or liquid in form or

a combination of the two.One of the interesting facts about the

historical development of rockets is thatwhile rockets and rocket-powered

devices have been in use for morethan two thousand years, it has beenonly in the last three hundred yearsthat rocket experimenters have had ascientific basis for understanding howthey work.

The science of rocketry beganwith the publishing of a book in 1687by the great English scientist Sir IsaacNewton. His book, entitledPhilosophiae Nature ifs PrincipiaMathematica, described physicalprinciples in nature. Today, Newton's

work is usually just called the Principia.In the Principia, Newton stated three

important scientific principles that governthe motion of all objects, whether on Earth or

in space. Knowing these principles, now calledNewton's I aws of Motion, rocketeers have been ableto construct the modern giant rockets of the 20thcentury such as the Saturn V and the Space Shuttle.Here now, in simple form, are Newton's Laws ofMotion,

1. Objects at rest will stay at rest and objects inmotion will stay in motion in a straight line unlessacted upon by an unbalanced force.

2. Force is equal to mass times acceleration.

3. For every action there is always an opposite andequal reaction.

13

As will be explained shortly, all three laws are reallysimple statements of how things move. But with them,precise determinations of rocket performance can be

made.

Newton's First Law

This law of motion is just an obvious statement of fact,

but to know what it means, it is necessary tounderstand the terms rest, motion, and unbalanced

force.Rest and motion can be thought

of as being opposite to each other.Rest is the state of an object when it isnot changing position in relation to itssurroundings. If you are sitting still in achair, you can be said to be at rest. Thisterm, however, is relative. Your chair mayactually be one of many seats on aspeeding airplane. The important thing toremember here is that you are not moving in

relation to your immediate surroundings. If restwere defined as a total absence of motion, it wouldnot exist in nature. Even if you were sitting in yourchair at home, you would still be moving, because your

chair is actually sitting on the surface of a spinningplanet that is orbiting a star. The star is movingthrough a rotating galaxy that is, itself, moving throughthe universe. While sitting "still," you are, in fact,

traveling at a speed of hundreds of kilometers persecond.

Motion is also a relative term. All matter in the

universe is moving all the time, but in the first law,motion here means changing position in relation tosurroundings. A ball is at rest if it is sitting on theground. The ball is in motion if it is rolling. A rolling

ball changes its position in relation to its surroundings.When you are sitting on a chair in an airplane, you areat rest, but if you get up and walk down the aisle, you

are in motion. A rocket blasting off the launch padchanges from a state of rest to a state of motion.

The third term important to understanding thislaw is unbalanced force. If you hold a ball in yourhand and keep it still, the ball is at rest. All the timethe ball is held there though, it is being acted upon by

forces. The force of gravity is trying to pull the ball

downward, while at the same time your hand is

pushing against the ball to hold it up. The forcesacting on the ball are balanced. Let the ball go, ormove your hand upward, and the forces becomeunbalanced. The ball then changes from a state of

rest to a state of motion.In rocket flight, forces become balanced and

unbalanced all the time. A rocket on the launch pad is

balanced. The surface of the pad pushes the rocket

up while gravity tries to pull it down. As the engines

(/j

Balll at Rest

1 4

Lift

are ignited, the thrust from the rocket unbalances theforces, and the rocket travels upward. Later, when therocket runs out of fuel, it slows down, stops at thehighest point of its flight, then falls back to Earth.

Objects in space alsc react to forces. Aspacecraft moving through the solar system is inconstant motion. The spacecraft will travel in a

straight line if the forces on it are in balance. Thishappens only when the spacecraft is very far from anylarge gravity source such as Earth or the other planetsand their moons. If the spacecraft comes near a large

body in space, the gravity of that body will unbalancethe forces and curve the path of the spacecraft. Thishappens, in particular, when a satellite is sent by arocket on a path that is parallel to Earth's surface. If

9

the rocket shoots the spacecraft fast enough, thespacecraft will orbit Earth. As long as anotherunbalanced force, such as friction with gas moleculesin orbit or the firing of a rocket engine in the oppositedirection from its movement, does not slow thespacecraft, it will orbit Earth forever.

Now that the three major terms of this first lawhave been explained, it is possible to restate this law.If an object, such as a rocket, is at rest, it takes anunbalanced force to make it move. If the object isalready moving, it takes an unbalanced force, to stopit, change its direction from a straight line path, or alterits speed.

Newton's Third Law

For the time being, we will skip the second law and godirectly to the third. This law states that every actionhas an equal and opposite reaction. If you have everstepped off a small boat that has not been properlytied to a pier, you will know exactly what this lawmeans.

A rocket can lift off from a launch pad onlywhen it expels gas out of its engine. The rocketpushes on the gas, and the gas in turn pushes on therocket. The whole process is very similar to riding askateboard. Imagine that a skateboard and rider arein a state of rest (not moving). The rider jumps off theskateboard. In the third law, the jumping is called anaction. The skateboard responds to that action bytraveling some distance in the opposite direction. Theskateboard's opposite motion is called a reaction.When the distance traveled by the rider and theskateboard are compared, it would appear that theskateboard has had a much greater reaction than theaction of the rider. This is not the case. The reasonthe skateboard has traveled farther is that it has lessmass than the rider. This concept will be betterexplained in a discussion of the second law.

With rockets, the action is the expelling of gasout of the engine. The reaction is the movement of therocket in the opposite dirc-,ct:on. To enable a rocket tolift off from the launch pad, the action, or thrust, fromthe engine must be greater than the mass of therocket. In space, however, even tiny thrusts will causethe rocket to change direction.

<Reaction

10

One of the most crrrimonly asked questionsabout rockets is how they can work in space wherethere is no air for them to push against. The answer tothis question comes from the third law. Imagine theskateboard again. On the ground, the only part airplays in the motions of the rider and the skateboard isto slow them down. Moving through the air causesfriction, or as scientists call it, drag. The surroundingair impedes the action-reaction.

As a result rockets actually work better inspace than they do in air. As the exhaust gas leavesthe rocket engine it must push away the surroundingair; this uses up some of the energy of the rocket. Inspace, the exhaust gases can escape freely.

Newton's Second Law

This law of motion is essentially a statement of amathematical equation. The three parts of theequation are mass (m), acceleration (a), and force (f).Using letters to symbolize each part, the equation canbe written as follows:

f = maBy using simple algebra, we can also write theequation two other ways:

Action

a =m

m =a

15

The first version of the equation is the one mostcommonly referred to when talking about Newton'ssecond law. It reads: force equals mass timesacceleration. To explain this law, we will use an oldstyle cannon as an example.

When the cannon is fired, an explosion propels acannon ball out the open end of the barrel. It flies akilometer or two to its target. At the same time thecannon itself is pushed backward a meter or two. Thisis action and reaction at work (third law). The forceacting on the cannon and the ball is the same. Whathappens to the cannon and the ball is determined bythe second law. Look at the two equations below.

f= rn (cannon)a

(cannon)

f = rn(ball)

a(ball)

The first equation refers to the cannon and the secondto the cannon ball. In the first equation, the mass isthe cannon itself and the acceleration is the movementof the cannon. In the second equation the mass is thecannon ball and the acceleration is its movement.

Because the force (exploding gun powder) is the samefor the two equations, the equations can be combinedand rewritten below.

m a rn a(cannon) (cannon) (ball) (ball)

In order to keep the two sides of the equations equal,the accelerations vary with mass. In other words, thecannon has a large mass and a small acceleration.The cannon ball has a small mass and a largeacceleration.

Let's apply this ?rinciple to a rocket. Replacethe mass of the cannon ball with the mass of thegases being ejected out of the rocket engine. Replacethe mass of the cannon with the mass of the rocketmoving in the other direction. Force is the pressurecreated by the controlled explosion taking place insidethe rocket's engines. That pressure accelerates thegas one way and the rocket the other.

Some interesting things happen with rocketsthat don't happen with the cannon and ball in thisexample. With the cannon and cannon ball, the thrustlasts for just a moment. The thrust for the rocketcontinues as long as its engines are firing.Furthermore, the mass of the rocket changes duringflight. Its mass is the sum of all its parts. Rocket partsincludes engines, propellant tanks, payload, controlsystem, and propellants. By far, the largest part of therocket's mass is its propellants. But that amountconstantly changes as the engines fire. That meansthat the rocket's mass gets smaller during flight. In

order for the left side of our equation to remain inbalance with the right side, acceleration of the rockethas to increase as its mass decreases. That is why arocket starts off moving slowly and goes faster andfaster as it climbs into space.

Newton's second law of motion is especiallyuseful when designing efficient rockets. To enable arocket to climb into low Earth orbit, it is necessary toachieve a speed, in excess of 28,000 km per hour. Aspeed of over 40,250 km per hour, called escapevelocity, enables a rocket to leave Earth and travel outinto deep space. Attaining space flight speedsrequires the rocket engine to achieve the greatestaction force possible in the shortest time. In otherwords, the engine must burn a large mass of fuel andpush the resulting gas out of the engine as rapidly aspossible. Ways of doing this will be described in thenext chapter.

Newton's second law of motion can berestated in the following way: the greater the mass ofrocket fuel burned, and the faster the gas producedcan escape the engine, the greater the thrust of therocket.

Putting Newton's Laws of MotionTogether

An unbalanced force must be exerted for a rocket to liftoff from a launch pad or for a craft in space to changespeed or direction (first law). The amount of thrust(force) produced by a rocket engine will be determinedby the mass of rocket fuel that is burned and how fastthe gas escapes the rocket (second law). Thereaction, or motion, of the rocket is equal to and in theopposite direction of the action, or thrust, from theengine (third law).

1 8 11

Practical Rocketry

12

The first rockets ever built, the fire-arrows of theChinese, were not very reliable. Many just

exploded on launching. Others flew on erratic coursesand landed in the wrong place. Being a rocketeer inthe days of the fire-arrows must have been an exciting,but also a highly dangerous activity.

Today, rockets are much more reliable. Theyfly on precise courses and are capable of going fastenough to escape the gravitational pull of Earth.Modern rockets are also more efficient today becausewe have an understanding of the scientific principlesbehind rocketry. Our understanding has led us todevelop a wide variety of advanced rocket hardwareand devise new propellants that can be used for longertrips and more powerful takeoffs.

Rocket Engines and Their Propellants

Most rockets today operate with either solid or liquidpropellants. The word propellant does not meansimply fuel, as you might think; it means both fuel andoxidizer. The fuel is the chemical rockets burn but, forburning to take place, an oxidizer (oxygen) must bepresent. Jet engines draw oxygen into their enginesfrom the surrounding air. Rockets do not have theluxury that jet planes have; they must carry oxygenwith them into space, where there is no air.

Solid rocket propellants, which are dry to thetouch, contain both the fuel and oxidizer combinedtogether in the chemical itself. Usually the fuel is amixture of hydrogen compounds and carbon and theoxidizer is made up of oxygen compounds. Liquidpropellants, which are often gases that have beenchilled until they turn into liquids, are kept in separatecontainers, one for the fuel and the other for theoxidizer. Then, when the engine fires, the fuel andoxidizer are mixed together in the engine.

A solid-propellant rocket has the simplest formof engine. It has a nozzle, a case, insulation,propellant. and an igniter. The case of the engine isusually a relatively thin metal that is lined withinsulation to keep the propellant from burning through.The propellant itself is packed inside the insulationlayer.

Many solid-propellant rocket engines feature ahollow core that runs through the propellant. Rocketsthat do not have the hollow core must be ignited at thelower end of the propellants and burning proceedsgradually from one end of the rocket to the other. In allcases, only the surface of the propellant burns.However, to get higher thrust, the hollow core is used.This increases the surface of the propellants availablefor burning. The propellants burn from the inside outat a much higher rate, and the gases produced escapethe engine at much higher speeds. This gives agreater thrust. Some propellant cores are star shapedto increase the burning surface even more.

17

To fire solid propellants, many kinds of

igniters can be used. Fire-arrows were ignited by

fuses, but sometimes these ignited too quickly andburned the rocketeer. A far safer and more reliable

form of ignition used today is one that employselectricity. An electric current, coming through wiresfrom some distance away, heats up a special wire

inside the rocket. The wire raises the temperature ofthe propellant it is in contact with to the combustion

point.Other igniters are more advanced than the

hot wire device. Some are encased in a chemical thatignites first, which then ignites the propellants. Stillother igniters, especially those for large rockets, are

rocket engines themselves. The small engine insidethe hollow core blasts a stream of flames and hot gasdown from the top of the core and ignites the entiresurface area of the propellants in a fraction of a

second.The nozzle in a solid-propellant engine is an

opening at the back of the rocket that permits the hot

expanding gases to escape. The narrow part of the

nozzle is the throat. Just beyond the throat is the exit

cone.The purpose of the nozzle is to increase the

acceleration of the gases as they leave the rocket and

thereby maximize the thrust. It does this by cuttingdown the opening through which the gases canescape. To see how this works, you can experimentwith a garden hose that has a spray nozzleattachment. This kind of nozzle does not have an exit

cone, but that does not matter in the experiment. Theimportant point about the nozzle is that the size of the

opening can be varied.Start with the opening at its widest point.

Watch how far the water squirts and feel the thrust

produced by the departing water. Now reduce thediameter of the opening, and again note the distancethe water squirts and feel the thrust. Rocket nozzles

work the same way.As with the inside of the rocket case,

insulation is needed to protect the nozzle from the hot

gases. The usual insulation is one that graduallyerodes as the gas passes through. Small pieces ofthe insulation get very hot and break away from the

nozzle. As they are blown away, heat is carried away

with them.The other main kind of rocket engine is one

that uses liquid propellants. This is a much morecomplicated engine, as is evidenced by the fact thatsolid rocket engines were used for at least sevenhundred years before the first successful liquid engine

was tested. Liquid propellants have separate storagetanksone for the fuel and one for the oxidizer. Theyalso have pumps, a combustion chamber, and a

nozzle.

TNozzle hroat

Payload

Igniter

Casing(body tube)

Core

Propellant(grain)

CombustionChamber

Fins

Solid Propellant Rocket

The fuel of a liquid-propellant rocket is usually

kerosene or liquid hydrogen; the oxidizer is usuallyliquid oxygen. They are combined inside a cavity

called the combustion chamber. Here the propellantsburn and build up high temperatures and pressures,and the expanding gas escapes through the nozzle atthe lower end. To get the most power from thepropellants, they must be mixed as completely aspossible. Small injectors (nozzles) on the roof of thechamber spray and mix the propellants at the sametime. Because the chamber operates under high

18 13

Liquid Propellant Rocket

Injectors

CombustionChamber

Fins

pressures, the propellants need to be forced inside.Powerful, lightweight turbine pumps between thepropellant tanks and combustion chambers take careof this job.

With any rocket, and especially with liquid-propellant rockets, weight is an important factor. Ingeneral, the heavier the rocket, the more the thrustneeded to get it off the ground. Because of the pumpsand fuel lines, liquid engines are much heavier thansolid engines.

14

One especially good method of reducing theweight of liquid engines is to make the exit cone of thenozzle out of very lightweight metals. However, theextremely hot, fast-moving gases that pass throughthe cone would quickly melt thin metal. Therefore, acooling system is needed. A highly effective thoughcomplex cooling system that is used with some liquidengines takes advantage of the low temperature ofliquid hydrogen. Hydrogen becomes a liquid when it ischilled to -253°C. Before injecting the hydrogen intothe combustion chamber, it is first circulated throughsmall tubes that lace the walls of the exit cone. In acutaway view, the exit cone wall looks like the edge ofcorrugated cardboard. The hydrogen in the tubesabsorbs the excess heat entering the cone walls andprevents it from melting the walls away. It also makesthe hydrogen more energetic because of the heat itpicks up. We call this kind of cooling systemregenerative cooling.

Engine Thrust Control

Controlling the thrust of an engine is very important tolaunching payloads (cargoes) into orbit. Too muchthrust or thrust at the wrong time can cause a satelliteto be placed in the wrong orbit or set too far out intospace to be useful. Too little thrust can cause thesatellite to fall back to Earth.

Liquid-propellant engines control the thrust byvarying the amount of propellant that enters thecombustion chamber. A computer in the rocket'sguidance system determines the amount of thrust thatis needed and controls the propellant flow rate. Onmore complicated flights, such as going to the Moon,the engines must be started and stopped severaltimes. Liquid engines do this by simply starting orstopping the flow of propellants into the combustionchamber.

Solid-propellant rockets are not as easy tocontrol as liquid rockets. Once started, the propellantsburn until they are gone. They are very difficult to stopor slow down part way into the burn. Sometimes fireextinguishers are built into the engine to stop therocket in flight. But using them is a tricky procedureand doesn't always work. Some solid-fuel engineshave hatches on their sides that can be cut loose byremote control to release the chamber pressure andterminate thrust.

The burn rate of solid propellants is carefullyplanned in advance. The hollow core running thelength of the propellants can be made into a starshape. At first, there is a very large surface availablefor burning, but as the points of the star burn away, thesurface area is reduced. For a time, less of thepropellant burns, and this reduces thrust. The SpaceShuttle uses this technique to reduce vibrations earlyin its flight into orbit.

1 S

NOTE: Although most rockets used by governments

and research organizations are very reliable, there is

still great danger associated with the building and firing

of rocket engines. Individuals interested in rocketryshould never attempt to build their own engines. Eventhe simplest-looking rocket engines are very complex.

Case-wall bursting strength, propellant packing

density, nozzle design, and propellant chemistry are all

design problems beyond the scope of most amateurs.

Many home-built rocket engines have exploded in the

faces of their builders with tragic consequences.

Stability and Control Systems

Building an efficient rocket engine is only part

of the problem in producing a successful rocket. Therocket must also be stable in flight. A stable rocket is

one that flies in a smooth, uniform direction. Anunstable rocket flies along an erratic path, sometimes

tumbling or changing direction. Unstable rockets aredangerous because it is not possible to predict where

they will go. They may even turn upside down andsuddenly head back directly to the launch pad.

Making a rocket stable requires some form of

control system. Controls can be either active orpassive. The difference between these and how they

work will be explained later. It is first important tounderstand what makes a rocket stable or unstable.

All matter, regardless of size, mass, or shape,

has a point inside called the center of mass (CM). Thecenter of mass is the exact spot where all of the mass

of that object is perfectly balanced. You can easily

find the center of mass of an object such as a ruler by

balancing the object on your finger. If the material

used to make the ruler is of uniform thickness anddensity, the center of mass should be at the halfwaypoint between one end of the stick and the other. If

the iuler were made of wood, and a heavy nail were

driven into one of its ends, the center of mass would

no longer be in the middle. The balance point wouldthen be nearer the end with the nail.

The center of mass is important in rocket flight

because it is around this point that an unstable rocket

tumbles. As a matter of fact, any object in flight tendsto tumble. Throw a stick, and it tumbles end over end.

Throw a ball, and it spins in flight. The act of spinning

or tumbling is a way of becoming stabilized in flight. A

Frisbee will go where you want it to only if you throw it

with a deliberate spin. Try throwing a Frisbee without

spinning it. If you succeed, you will see that the

Frisbee flies in an erratic path and falls far short of its

mark.In flight, spinning or tumbling takes place

around one or more of three axes. They are called

roll, pitch, and yaw. The point where all three of these

axes intersect is the center of mass. For rocket flight,

the pitch and yaw axes are the most importantbecause any movement in either of these twodirections can cause the rocket to go off course. The

roll axis is the leastimportant becausemovement along this axiswill not affect the flightpath. In fact, a rollingmotion will help stabilizethe rocket in the sameway a properly passedfootball is stabilized byrolling (spiraling) it inflight. Although a poorly 11'

PITCHpassed football may stillfly to its mark even if ittumbles rather than rolls,a rocket will not. Theaction-reaction energy ofa football pass will becompletely expended bythe thrower the momentthe ball leaves the hand.With rockets, thrust fromthe engine is still being produced while the rocket is in

flight. Unstable motions about the pitch and yaw axes

will cause the rocket to leave the planned course. To

prevent this, a control system is needed to prevent or

at least minimize unstable motions.In addition to center of mass, there is another

important center inside the rocket that affects its flight.

This is the center of pressure (CP). The center of

pressure exists only when air is flowing past themoving rocket. This flowing air, rubbing and pushing

against the outer surface of the rocket, can cause it tobegin moving around one of its three axes. Think for a

moment of a weather vane. A weather vane ;s anarrow-like stick that is mounted on a rooftop and used

for telling wind direction. The arrow is attached to a

ROLL

YAW

Centerof

Pressure

Centerof

Mass

vertical rod that acts as a pivot point. The arrow is

balanced so that the center of mass is right at the pivot

point. When the wind blows, the arrow turns, and the

head of the arrow points into the on-coming wind. The

tail of the arrow points in the downwind direction.

2015

The reason that the weather vane arrow pointsinto the wind is that the tail of the arrow has a muchlarger surface area than the arrowhead. The flowingair imparts a greater force to the tail than the head,and therefore the tail is pushed away. There is a pointon the arrow where the surface area is the same onone side as the other. This spot is called the center ofpressure. The center of pressure is not in the sameplace as the center of mass. If it were, then neitherend of the arrow would be favored by the wind and thearrow would not point. The center of pressure isbetween the center of mass and the tail end of thearrow. This means that the tail end has more surfacearea than the head end.

It is extremely important that the center ofpressure in a rocket be located toward the tail and thecenter of mass be located toward the nose. If they arein the same place or very near each other, then therocket will be unstable in flight. The rocket will then tryto rotate about the center of mass in the pitch and yawaxes, producing a dangerous situation. With thecenter of pressure located in the right place, the rocketwill remain stable.

Control systems for rockets are intended tokeep a rocket stable in flight and to steer it. Smallrockets usually require only a stabilizing controlsystem. Large rockets, such as the ones that launchsatellites into orbit, require a system that not onlystabilizes the rocket, but also enable it to changecourse while in flight.

Controls on rockets can either be active orpassive. Passive controls are fixed devices that keeprockets stabilized by their very presence on therocket's exterior. Active controls can be moved whilethe rocket is in flight to stabilize and steer the craft.

The simplest of all passive t-ontrols is a stick.The Chinese fire-arrows were simple rockets mountedon the ends of sticks. The stick kept the center ofpressure behind the center of mass. In spite of this,fire-arrows were notoriously inaccurate. Before thecenter of pressure could take effect, air had to beflowing past the rocket. While still on the ground andimmobile, the arrow might lurch and fire the wrongway.

Years later, the accuracy of fire-arrows wasimproved considerably by mounting them in a troughaimed in the proper direction. The trough guided thearrow in the right direction until it was moving fastenough to be stable on its own.

As will be explained in the next section, theweight of the rocket is a critical factor in performanceand range. The fire-arrow stick added too much deadweight to the rocket, and therefore limited its rangeconsiderably.

An important improvement in rocketry camewith the replacement of sticks by clusters of lightweightfins mounted around the lower end near the nozzle.

16

Fins could be made out of lightweight materials and bestreamlined in shape. They gave rockets a dartlikeappearance. The large surface area of the fins easilykept the center of pressure behind the center of mass.Some experimenters even bent the lower tips of thefins in a pinwheel fashion to promote rapid spinning inflight. With these "spin fins," rockets become muchmore stable in flight. But this design also producesmore drag and limits the rocket's range.

Vi t the start of modern rocketry in the 20thcentury, new ways were sought to improve rocketstability and at the same time reduce overall rocketweight. The answer to this was the development ofactive controls. Active control systems includedvanes, movable fins, canards, gimbaled nozzles,vernier rockets, fuel injection, and attitude-controlrockets. Tilting fins and canards are quite similar toeach other in appearance. The only real differencebetween them is their location on the rockets.Canards are mounted on the front end of the rocketwhile the tilting fins are at the rear. In flight, the finsand canards tilt like rudders to deflect the air flow andcause the rocket to change course. Motion sensors on

MoveableFins

21

the rocket detect unplanned directional changes, andcorrections can be made by slight tilting of the fins andcanards. The advantage of these two devices is sizeand weight. They are smaller and lighter and produceless drag than the large fins.

Other active control systems can eliminate finsand canards altogether. By tilting the angle at whichthe exhaust gas leaves the rocket engine, coursechanges can be made in flight. Several techniquescan be used or changing exhaust direction.

Vanes are small finlike devices that are placedinside the exhaust of the rocket engine. Tilting thevanes deflects the exhaust, and by action-reaction therocket responds by pointing the opposite way.

Another method for changing the exhaustdirection is to gimbal the nozzle. A gimbaled nozzle isone that is able to sway while exhaust gases arepassing through it. By tilting the engine nozzle in theproper direction, the rocket responds by changingcourse.

GimbaledNozzle

22

Vernier rockets can also be used to changedirection. These are small rockets mounted on theoutside of the large engine. When needed they fire,producing the desired course change.

In space, only by spinning the rocket along theroll axis or by using active controls involving theengine exhaust can the rocket be stabilized or have itsdirection changed. Without air, fins and canards havenothing to work upon. (Science fiction movies showingrockets in space with wings and fins are long on fictionand short on science.) The most common kinds ofactive control used in space are attitude-controlrockets. Small clusters of engines are mounted allaround the vehicle. By firing the right combination ofthese small rockets, the vehicle can be turned in anydirection. As soon as they are aimed properly, themain engines fire, sending the rocket off in the newdirection.

Mass

There is another important factor affecting theperformance of a rocket. The mass of a rocket canmake the difference between a successful flight andjust wallowing around on the launch pad. As a basicprinciple of rocket flight, it can be said that for a rocketto leave the ground, the engine must produce a thrustthat is greater than the total mass of the vehicle. It isobvious that a rocket with a lot of unnecessary masswill not be as efficient as one that is trimmed to just thebare essentials.

For an ideal rocket, the total mass of thevehicle should be distributed following this generalformula:

Of the total mass, 91 percent should bepropellants; 3 percent should be tanks,engines, fins, etc.; and 6 percent can be thepayload.

Payloads may be satellites, astronauts, orspacecraft that will travel to other planets or moons.

In determining the effectiveness of a rocketc'Dsign, rocketeers speak in terms of mass fraction(MF). The mass of the propellants of the rocketdivided by the total mass of the rocket gives massfraction:

mass of propellantsMF = _ _ _

total mass

The mass fraction of the ideal rocket givenabove is 0.91. From the mass fraction formula onemight think that an MF of 1.0 is perfect, but then theentire rocket would be nothing more than a lump of

17

propellants that would simply ignite into a fireball. Thelarger the MF number, the less payload the rocket cancarry; the smaller the MF number, the less its rangebecomes. An MF number of 0.91 is a good balancebetween payload-carrying capability and range. TheSpace Shuttle has an MF of approximately 0.82. TheMF varies between the different orbiters in the SpaceShuttle fleet and with the different payload weights ofeach mission.

Large rockets, able to carry a spacecraft intospace, have serious weight problems. To reach spaceand proper orbital velocities, a great deal of propellantis needed; therefore, the tanks, engines, and associ-ated hardware become larger. Up to a point, biggerrockets fly farther than smaller rockets, but when theybecome too large their structures weigh them downtoo much, and the mass fraction is reduced to animpossible number.

A solution to the problem of giant rocketsweighing too much can be credited to the 16th-centuryfireworks maker Johann Schmid lap. Schmid lapattached small rockets to the top of big ones. Whenthe large rocket was exhausted, the rocket casing wasdropped behind and the remaining rocket fired. Muchhigher altitudes were achieved by this method. (TheSpace Shuttle follows the step rocket principle bydropping off its solid rocket boosters arid external tankwhen they are exhausted of propellants.)

18

The rockets used by Schmid lap were calledstep rockets. Today this technique of building a rocketis called staging. Thanks to staging, it has becomepossible not only to reach outer space but the Moonand other planets too.

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Saturn V rocket being transported to the launch pad

23

Activities andDemonstrations

Hero Engines 21

Rocket Pinwheel 23

Rocket Car 24

Water Rocket 25

Bottle Rocket 27

Newton Car 29

Antacid Tablet Race 31

Paper Rockets 32

Pencil "Rocket" 33

Balloon Staging 35

Altitude Tracking 36

2419

Hero EnginesObjective: To demonstrate Newton's Third Law of Motion using the actionforce of expanding steam or falling water,Description: This activity provides plans for constructing and using twoversions (teacher demonstration model and student model) of a working Heroengine.

Procedure: Making a Steam-PoweredHero Engine (Teacher Model)

1. File the middle of the brass tube until a notch isproduced. Do not file the tube in half.

2. Using the ice pick or drill, bore two small holes onopposite sides of the float at its middle. The holesshould be just large enough to pass the tubestraight through the float.

3. With the tube positioned so that equal lengthsprotrude through the float, heat the contact points ofthe float and tube with the propane torch. Touchthe end of the solder to the heated area so that itmelts and seals both joints.

4. Drill a water access hole through the threadedconnector at the top of the float.

5. Using the torch again, heat the protruding tubesabout one inch from each end.With pliers, carefully bendthe tube tips in oppositedirections. Bend thetubes slowly so they donot crimp.

6. Drill a small hole throughthe flat part of the thumbscrew for attaching thefish line and swivel. Twistthe thumb screw into the threaded connector of thefloat in step 4 and attach the line and swivel.

File notch in middleof tube. Step 1.

Procedure: Using the Steam-PoweredHero Engine

1 Place a small amount of water (about 10 to 20 ml)into the float. The precise amount is not important.The float can be filled through the top if you drilledan access hole or through the tubes by partiallyimmersing the engine in a bowl of water vsith onetube submerged and the other out of the water.

25

2. Suspend the engine and heat its bottom with thetorch. In a minute or two, the engine should beginspinning. Be careful not to operate the engine toolong because it probably will not be exactlybalanced and may wobble violently. If it begins towobble, remove the heat.

Materials and Tools: (Teacher Model)Copper toilet tank float (available from full-line

hardware stores)Thumb screw, 1/4 inchBrass tube, 3/16 I.D., 12 in. (from hobby shops)SolderFishing lineIce pick or drillMetal filePropane torch

21

Caution: The steam-powered Hero engineshould be operated by adults only. Wear eyeprotection. Be sure to confirm that the tubesare not obstructed in any way before heating.Test the by blowing through one like astraw. If air flows oi the other tube, theengine is safe to use.

Procedure: Making and Using the SodaPop Can Hero Engine(Student Model)

1. Lay the can on its side and using the nail or ice pickcarefully punch four equally spaced, small holesjust above and around the bottom rim. Then,before removing the punching tool from each hole,push the tool to the right (parallel to the rim) so thatthe holes all slant in the same direction.

2. Bend the can's opener lever straight up and tie ashort length of fishing line to it.

3. Immerse the can in water until it is filled. Pull thecan out by the fishing line. As water streams out,the can will start spinning.

Discussion:

The Hero engine was invented by Hero ofAlexandria in the first century B.C. Refer to thehistorical text at the beginning of this guide forinformation about the engine and other early rocket-powered devices.

The principle behind the Hero engine issimple. Steam from the boiling water inside the floatpressurizes the metal sphere (float). T he steamrapidly escapes through the L-shaped tubes producingan action-reaction force that causes the sphere to spinin the opposite direction. The action-reaction principleof the Hero engine is the same that is used to propelairplanes and rockets.

Teaching Notes and Questions:

Because of the steam produced with the first Heroengine. Only the teacher should operate it. Thesecond engine design is safe for all students to use.Is there any difference in the efticiency (rate ofrotation) of the soda pop engines and the numberand diameter of the holes? If there are differences,how can they be explained using Newton's SecondLaw of Motion?What happens if the holes slant in differentdirections?

22

What happens when the holes are spaced unevenlyor at different heights?Be sure to recycle the soda pop cans at the end ofthe activity.

Materials and Tools: (Student Model)Empty soda pop can with the opener lever stillattachedNail or ice pickFishing lineBucket or tub of water

26

Rocket PinwheelObjective: To demonstrate Newton's Third Law of Motion using air escaping

from a balloon as the action force.Description: In this activity, students construct a balloon-powered pinwheel

that spins from the force of air escaping through a plastic straw.

Method:1. Inflate the balloon to stretch it out.2. Slip the nozzle end of the balloon over the end of

the straw farthest away from the flexible bend. Usea short piece of plastic tape to seal the balloon tothe straw. The balloon should inflate when you

blow through the straw.3. Bc. d the opposite end of the straw at a right angle.

4. Lay the straw and balloon on an outstretched fingerto find the balance point. Push the pin through the

straw at the balance point, into the pencil eraser,

and into the wood itself.5. Spin the straw a few times to loosen up the hole the

pin made.6. Inflate the balloon and let go of the straw.

Discussion:The balloon-powered pinwheel spins because of theaction-reaction principle described in Newton's Third

Law of Motion. The air, traveling around the bend inthe straw, imparts a reaction force at a right angle tothe straw. The result is that the balloon and straw spin

around the pin in the opposite direction.

Teaching Notes and Questions:This activity can be done by every student; however,

younger students may need assistance in insertingthe pin into the wood of the pencil.Some toy and variety stores sell an inexpensiveballoon powered helicopter. The device has three

small plastic wings through which air passes and is

released in a right angle direction at each blade tip.

Try to obtain one or more of these toys forcomparison with the balloon pinwheel. The toy is

marketed under the name of Whistle BalloonHelicopter. One of these helicopters was used by

astronauts on the STS-54 Space Shuttle missionduring the Physics of Toys live lesson. Refer to the

reference list at the end of this guide for information

on obtaining a videotape that demonstrates this toy's

performance in microgravity.

27

Materials:Wooden pencil with an eraser on one endStraight pinRound party balloonFlexible soda strawPlastic tape

Rocket CarObjective: Newton's Third Law of Motion is demonstrated with escaping airas the action force.Description: In this activity, students construct a balloon-powered rocket carthat rolls across the floor because air is forced to escape through a plasticstraw.

Procedure:1. Using the ruler, marker, and drawing compass, draw

a rectangle about 7.5 cm by 18 cm and four circles7.5 cm in diameter on the flat surface of the meattray. Cut out each piece.

2. Inflate the balloon a few times to stretch it. Slip thenozzle over the end of the flexi-straw nearest thebend. Secure the nozzle to the straw with tape andseal it tight so that the balloon can be inflated byblowing through the straw.

3. Tape the straw to the car as shown in the picture.4. Push one pin into the center of each circle and then

into the edge of the rectangle as shown in thepicture. The pins become axles for the wheels. Donot push the pins in snugly because the wheelshave to rotate freely. It is okay if the wheelswobble.

5. Inflate the balloon and pinch the straw to hold in theair. Set the car on a smooth surface and releasethe straw.

Discussion:The rocket car is propelled along the floor according tothe principle stated in Isaac Newton's Third Law ofMotion. The escaping air is the action and themovement of the car in the opposite direction is thereaction. The car's wheels reduce friction and providesome stability to the car's motion. A well-designedand constructed car will travel several meters in astraight line across a smooth floor.

Teaching Notes and Questions:Encourage students to design their own cars. Carscan be made long or short, wide or narrow, or eventrapezoidal. Wheels can be large or small. Ifstyrofoam coffee cups are available (retrieved fromthe waste basket and washed is preferable), thebottoms can be cut off and used as wheels.Hold car distance trials on the floor. Have studentsmeasure and chart the distance each car travels.

24

Average multiple runs for individual cars to identifythe best cars. What makes one car design performbetter than another? Are large wheels better thansmall wheels?

Materials and Tools:4 pinsStyrofoam meat trayCellophane tapeFlexi-strawScissorsDrawing compassMarker penSmall party balloonRuler

28

Water RocketObjective: To demonstrate how rocket performance is improved throughapplication of Newton's Second Law of MotionDescription: In this activity, students test fire a commercial water rocketusing varying amounts of air pressure and water to learn how optimumperformance can be achieved.

Procedure:1. Take the water rockets, water supply, measuring

tape, and markers to an outside location such as aclear, grassy playing field.

2. Attach both rockets to their pumps according to themanufacturer's instructions. Pump one rocket 10times. Pump the second rocket 20 times. Havetwo students point the rockets across the field in adirection in which no one is standing. The rocketsshould be held next to each other at exactly thesame height above the ground and aimed upwardat about a 45 degree angle. Count backwards from3 and have the students release the rockets. Markthe distance each rocket flew.

3. Pour water into one rocket so that it fills up to therecommended level in the instructions. Do not pourwater into the other rocket. Attach both rockets totheir pumps. Pump both rockets 20 times. Againaim the rockets across the field as before andrelease them simultaneously. Mark the distanceeach rocket flew. Caution: The rocket with thewater will expel the water from its chamber andmay spray the students. If the students standto the side for the release, the water sprayshould miss them.

4. Try other combinations for simultaneous firings ofthe rockets, such as a small amount of water in oneand a larger amount of water in the other, or equalamounts of water but one pumped a differentnumber of times. Be sure to change only onevariable at a time (i.e., vary only the water or onlythe pumping).

Discussion:Water rockets can demonstrate Newton's Second Lawof Motion where one varies the pressure inside therocket and the amount of water present. In the firsttest, neither rocket went very far because the air insidedid not have much mass. The rocket that was pumpedmore did travel farther because the air in that rocketwas under greater pressure and it escaped the rocket

29

Materials and Tools:2 Water rockets and pumps (available for a few

dollars each from toy stores)WaterSmall wooden stakes, small flags, or other

materials to serve as markersTape measure

25

at a higher speed (acceleration). When water wasadded to one of the rockets, the effect of mass wasdemonstrated. Before the air could leave the waterrocket, the water had to be expelled first. Water has amuch greater mass than air and it contributed to amuch greater thrust. The rocket with water flew muchfarther than the rocket filled only with air. By varyingthe amount of water and air in the rocket andmeasuring how far the rocket? 'ref, students can seethat the thrust of the rocket is dependent on the massbeing expelled and the speed of expulsion. Thrust isgreatest when mass and acceleration are greatest.

Teaching Notes and Questions:Several different versions of water rockets areavailable. If you can obtain a couple of differentmodels, run comparison flights. Do they performequally? If not, why? (Be sure to check the entirerocket to answer this question. Some models comewith bigger nozzles than others.)Measure and graph the distance each rocket flew.Be sure to indicate the number of pumps and thequantity of water used.Why does the water rocket have bent fin tips?Will the rocket go farther if more water is added thanrecommended by the manufacturer ? Why or whynot?

26 30

Bottle RocketObjective: Rocket performance is improved through application of Newton's

Second Law of Motion.Description: In this activity, students construct a high-performance bottle

rocket from a plastic soft drink bottle and a hand or foot operated air pump to

test the effect of varying air pressure.

Procedure: (steps 1-5 should be done by the

teacher)1. Using a small knife blade or a

valve stem tool, remove theneedle valve from within the tirevalve. To do so, place the bladepoint inside the valve (cap end)and gently turn the valve. Theneedle valve will begin tounscrew. Remove it and discard.

2. Enlarge the hole inside the tire valve with the drill5/32" bit. Hold the valve with a vise whiledrilling. Press the drill gently to avoid jamming

the bit.3. Using the 9/16 bit, drill a hole through the center

of the plastic cap of the soft drink bottle.Carefully clean off any plastic burrs with the

knife.4. Press the tire valve from the inside through the

hole in the plastic cap until it locks into place.

5. Screw the plastic cap on the soft drink bottle.

The bottle is ready for launch.6. Attach the pump valve to the rocket. Push the

lever to lock the valve on the rocket. Whilewearing safety goggles, pump the rocket to apressure of 30 pounds. Hold the rocket upward bythe pump hose and valve. Aim the rocket in a cleardirection and quickly open the lever on the pumpvalve. The rocket will take off. Pump the rocket up

again but this time to a pressure of 60 pounds.

Caution: For a safety margin, pump the rocketno higher than 90 pounds. This isapproximately 50% of the industryspecifications for this kind of container.

Tubeless TireValve

Discussion:Like a balloon full of air, the bottle rocket is

pressurized. When the pump valve is opened, air

escapes the bottle, providing an action force that isaccompanied by an equal and opposite reaction force

(Newton's Third Law of Motion). Increasing the

pressure inside the bottle rocket produces greater

31

Materials and Tools:Plastic soft drink bottle with plastic cap (large or

small)Tubeless tire valve - 1 1/4" long, TR No. 413

(available from auto supply stores)DrillDrill bits - 5/32", and 9/16" (or spade bit)

Small viseAir pump, foot or hand style (not bicycle frame

pump) with pressure gauge and lever-typevalve attachment

Small knife blade or valve stem toolSafety goggles

27

thrust. This is because a greater mass of air inside thebottle escapes with a higher acceleration (Newton'sSecond Law of Motion). Try adding a small amount ofwater to the bottle. The escaping mass increases, andthereby increases the action force produced.

Teaching Notes and Questions:Have each student bring plastic soft drink bottles toschool to decorate and fly. The tire valve/cap can beshared among the different bottles. Is there anydifference between the flight of large and smallbottles? Is there any difference in the amount ofeffort required to raise bottles of different size toequal pressures? Compare the volume of the bottleswith the number of pump strokes required.Because the bottle rocket does not have any passiveor active stability controls, the bottle tumbles throughthe air. Experiment with attaching fins to the bottlerocket to stabilize its flight.Will the addition of a small amount of water to thebottle rocket improve its performance? (See WaterRocket activity.) What will happen to the rocket'sperformance if more water is added? Is there a limitto how much water should be added?A launch pad can be constructed from boards, dowel

rods, and string. The launch pad shown here usesdowel rods to hold the rocket upright for launch. Thepump valve is opened and the rocket released bypulling on the string.If your community has a plastic recycling program, besure to recycle damaged bottle rockets and plasticscraps.Look up the following references for plans forconstructing a different kind of bottle rocket launcherand for additional teaching strategies:

Hawthorne, M. & Saunders, G. (1993), "ItsLaunchtimel," Science and Children, v30n5,p17-19, 39.

Rogis, J. (1991), "Soaring with Aviation Activities,"Science Scope, v15n2, pp14-17.

Winemiller, J., Pedersen, J., & Bonnstetter, R.(1991), "The Rocket Project," Science Scope,v15n2, pp18-22.

28

3 2

Newton CarObjective: To demonstrate Newton's Second Law of Motion by showing the

reaction of a rolling car by increasing its mass and acceleration.

Description: In this activity, students test a slingshot-like device that throws

a wooden block that causes the car to move in the opposite direction.

Procedure:1. Screw the three screws in the large

wood block as shown in the diagram.2. Hold the short piece of wood with a vice

and drill two holes large enough to droptwo sinkers in each.

3. Tie the string into several small loops ofthe same size.

4. Place one string loop over a rubberband and then place the ends of therubber band over the two screws onone end of the large wood block. Pullthe rubber band back like a slingshotand slip the string over the third screwto hold the rubber band stretched.

5. On a level table top arrange the pencilsor dowel rods in a row like railroad ties.Be sure to mark the position of eachdowel rod to make the experimentexactly the same way each time it istried. Place the large block on one end of the rowso that the tips of each single screw points towardthe other dowel rods. Slip the small block (withoutsinkers) into the rubber bands.

6. Light a match and ignite the ends of the stringhanging down from the loop. When the string burnsthrough, the rubber band will throw the block off thecar and the car will roll in the other direction.Measure how far the car travels along the table top.

7. Reset the equipment and add a second rubberband. Again, light the string, then measure andrecord how far the car travels.

8. Reset the equipment and try again with .3 rubberbands. Then try again with one rubber band andtwo sinkers, 4 sinkers, etc.

9. Plot the data from each of the experiments on agraph similar to the sample on the next page.

Sinkers fit here

33

Materials and Tools:1 Wooden block about 10x20x2.5 cm1 Wooden block about 7.5x5x2.5 cm3 3-inch No. 10 wood screws (round head)12 Round pencils or short lengths of similar

dowel rods3 Rubber bandsCotton stringMatches6 Lead fishing sinkers (about 1/2 ounce each)Drill and bit (bit size determined by the diameter

of the fishing sinkers)ViceScrewdriverMeter stick

29

Discussion:The Newton car provides an excellent demonstrationof Isaac Newton's Second Law of Motion. By re-peated trials of the experiment, it will become clearthat the distance the car travels depends on thenumber of rubber bands used and the mass of theblock being expelled. By adding sinkers to the block,the mass of the block is increased. By adding rubberbands, the acceleration of the block increases. (Referto the chapter on rocket principles for a more detailedexplanation of this law. The cannon and cannon ballexample in the chapter is very similar to the NewtonCar.)

Teaching Notes and Questions:This activity offers a number of opportunities tocombine science and mathematics. Mathematicskills that can be employed include measurement,recording data, plotting data on a graph, and inter-preting graphical data.

30

Because this activity involves the use of matches, besure to exercise proper safety procedures. Caution:Provide adequate ventilation and a place todispose of used matches. Scissors can be substi-tuted for the matches. Using scissors requires somepractice because the scissors must be quicklywithdrawn after cutting the string so as to not inter-fere with the reaction motion of the car.Permit students to test this principle for themselvesby first stepping and then jumping off a stationaryskateboard. Observe how far the skateboard travels.Caution: Be sure to have a student spotternearby so the student will not get hurt jumpingfrom the skateboard,.Compare this activity with the water rocket activity.

Newton Car Trials

6 60 60 (§ & (;,;co <Go scoc c * \t-- ,i----)rt, tb- Qr .<- .c. t-- .\ .'0 NO NO c,' co

co co cok c \ \ \Z e tZ

PsC) .§)s() \PNC)k k k `6s' 6°' 6c-)00 'CP. (§s' (2)-C\k '.0 'o0 'c c ec & c,),60 e sose) so sQ, solZ

(Sample graph. Actual student graphs will vary with skill andcare in experiment setup and measurement.)

34

Procedure:1. Fill both beakers about half full

with water of the sametemperature.

2. Wrap paper around one antacid tablet.Place the packet on a hard surface andcrush the tablet by pressing on it with thewood block.

3. Open the paper packet with the crushedtablet and hold it over one of the beakers.Pour the power in the water and time howlong it takes for the powder to dissolve.

4. Pick up a whole tablet and drop it into thesecond beaker of water. Time how long ittakes to dissolve completely.

Antacid Tablet RaceObjective: To demonstrate how increasing the surface area of a chemical

increases its reaction rate.Description: A whole antacid tablet and a crushed tablet are added toseparate beakers of water so that their relative reaction rates can becompared.

Discussion:This activity demonstrates how increasing thesurface area of an antacid tablet by crushing itinto a powder increases the rate in which it dissolvesin water. This is a similar situation to the way thethrust of a rocket is increased by increasing theburning surface of its propellants. Increasing theburning surface increases its burning rate. In solidrockets, a hollow core extending the length of thepropellant will permit more propellant to burn at a time.This increases the acceleration of the gases producedas they leave the rocket engine. Liquid propellants aresprayed into the combustion chamber of a liquidpropellant rocket to increase their surface area.Smaller droplets react more quickly than do largeones, increasing the acceleration of the escapinggases.

Teaching Notes and Questions:This activity is an ideal way for safely showing howthe burning rate of rocket propellants is increasedwithout having the students use fire.A similar activity can be tried with small pieces ofhard candy. Take two pieces of candy and crush

35

one. Then, give the whole candy piece to onestudent and the crushed candy to another student todissolve in their mouths. Which candy will dissolvefirst?Demonstrate the same effect by trying to ignite athick piece of wood with a match. Next, cut the woodwith a sharp knife to make shavings. Then, try toignite the shavings. Caution: Be sure to exerciseproper safety precautions with fire.

Materials:Antacid tablets (two per test)Two beakers (or glass or plastic jars)Tweezers or forcepsScrap paperWatch or clock with second handSmall block of wood

31

Paper RocketsObjective: To demonstrate the importance of using control systems, such asfins, to stabilize rockets in flight.Description: In this activity, students construct small flying rockets out ofpaper and propel them by blowing air through a straw.

Procedure:1. Cut a narrow rectangular strip of paper

about 13 cm long and roll it tightly aroundthe fat pencil. Tape the cylinder andremove it from the pencil.

2. Cut points into one end of the cylinder tomake a cone and slip it back onto thepencil.

3. Slide the cone end onto the pencil tip. Squeeze andtape it together to seal the end and form a nosecone (the pencil point provides support for taping).An alternative is just to fold over one end of thetube and seal it with tape.

4. Remove the cylinder from the pencil and gently blowinto the open end to check for leaks. If air easilyescapes, use more tape to seal the leaks.

5. Cut out two sets of fins using the pattern on thispage and fold according to instructions. Tape thefins near the open end of the cylinder. The tabsmake taping easy.

Flying the Paper Rocket:Slip the straw into the rocket's opening. Point therocket in a safe direction and blow sharply through thestraw. The rocket will shoot away. Caution: Becareful not to aim the rocket toward anyonebecause the rocket could poke an eye.

Discussion:The paper rocket activity demonstrates how rockets flythrough the atmosphere. A rocket with no fins is muchmore difficult to control than a rocket with fins. Theplacement and size of the fins is critical to achieveadequate stability while not adding too much weight.

Teaching Notes and Questions:Try flying a paper rocket with the fins placed on thefront end of the cylinder. Also try attaching delta-shaped wings to achieve a gliding flight.How small can the fins be made and still stabilize therocket? How many fins are requir ..3d?

32

Tape

Fold Down.

Fold Up. Fold Up.

What will happen to the rocket if the lower tips of thefins are bent pinwheel fashion?Test fly different paper rockets to see which will travelhigher or farther. Investigate the designs of therockets that travel the farthest and shortestdistances. What makes one rocket perform betterthan another? (Do not forget to examine the weightof each rocket. Rockets made with extra tape andlarger fins weigh more.)Are rocket fins necessary in outer space?

Materials:Scrap bond paperCellophane tapeScissorsSharpened fat pencilMilkshake straw (slightly linner than pencil)

Jo

Pencil "Rocket"Objective: To demonstrate the effect fins have on rocket flight through

the atmosphere.Description: In this activity, students fly pencil "rockets" using a rubber

band powered launch gantry.

Procedure: Launch Platform1. Join the two pieces of wood as shown in the

diagram to form the launch platform. Use metalangle irons on each side to strengthen thestructure.

2. Screw the cup hooks and screw eye into the woodas indicated in Figure 1.

3. Disassemble the clothespin, and file the "jaw" ofone wood piece square as shown in Figure 2.Drill a hole in this piece and two holes in theother piece as shown in the figure.

4. Drill a hole through the upright piece of thelaunch platform as shown in Figuru 1, andscrew the clothespin to the upright piece sothat the lower holes in the clothespin line upwith the hole in the upright board.Reassemble the clothespin.

5. Tie a big knot in one end of the string andfeed it through the clothespin as shown inthe magnification of Figure 1, through theupright piece of the platform, and then through thescrew eye. When the free end of the string ispulled, the string will not slip out of the hole, andthe clothespin will open. The clothespin hasbecome a rocket hold-down and release device.

6. Loop four rubber bands together and loop theirends on the cup hooks. The launch platform isnow complete.

Figure 1

Procedure: Rocket1. Take a short piece of baling wire and wrap it around

the eraser end of the pencil about 2.5 cm from theend. Use pliers to twist the wire tightly so that it"bites" into the wood a bit. Next, bend the twistedends into a hook as shown in Figure 3.

2. Take a sharp knife and cut a notch in the other endof the pencil as shown in Figure 3.

37

Materials and Tools:2 Pieces of wood about 1 meter by 7.5 centimeters

(thickness can vary)2 Cup hooks1 Wooden spring clothespin1 Small wood screw1 Screw eye4 Metal angle irons and screws4 Feet of heavy stringIron baling wireSeveral rubber bandsSeveral unsharpened wooden pencilsSeveral pencil cap erasersCellophane or masking tapeHeavy paperSawWood fileDrill about 3/16 inch in diameterPliers

33

3. Cut out small paper rocket fins and tape them to thepencil just above the notch.

4. Place an eraser cap over the upper end of therocket. This blunts the nose to make the rocketsafer if it hits something. The rocket is nowcomplete.

Launching Pencil Rockets1. Choose a wide-open area to launch the rockets.2. Spread open the jaw of the clothespin and place the

notched end of the rocket in the jaws. Close thejaws and gently pull the pencil upward to insure therocket is secure. If the rocket does not fit, changethe shape of the notch slightly.

3. Pull the rubber bands down and loop them over thewire hook. Caution: Be sure not to look downover the rocket as you do this, in case therocket is prematurely released.

4. Stand at the other end of the launcher and step onthe wood to provide additional support.

5. Make sure no one except yourself is standing nextto the launch pad. Count down from 10 and pull thestring. Step out of the way from the rocket as it fliesabout 20 meters up in the air, gracefully turnsupside down, and returns to Earth.

6. The rocket's terminal altitude can be adjusted byincreasing or decreasing the tension on the rubberbands.

DiscussionLike Robert Goddard's first liquid-fuel rocket in 1926,the pencil rocket gets its upward thrust from the nosearea rather than the tail. Regardless, the rocket's finsstill provide stability, guiding the rocket upward for asmooth flight. If a steady wind is blowing during flight,the fins will steer the rocket toward the wind in aprocess called "weather cocking." Active controlssteer NASA rockets during flight to prevent weathercocking and to aim them on the right trajectory. Activecontrols include tilting nozzles and various forms offins and vanes.

Teaching Notes and Questions:Permit each student to make his or her own pencilrocket. If the children are too young to safely maketheir own notches, have an adult or older studentnotch enough pencils and clothespins for the entireclass.What would happen if the rocket had only one fin?Two? What would happen if the fins are placed inthe middle of the pencil rocket? At the upper end?Is the pencil rocket a genuine rocket? Why?

34

File notch.

Drill holes.

Figure 2

38

Balloon StagingObjective: To demonstrate the principle of rocket staging.Description: In this activity, students simulate a multistage rock launchusing two inflated balloons that slide along a fishing line by the thrust produced

from escaping air.

Procedure:1. Thread the fishing line through the two straws.

Stretch the fishing line snugly across a room andsecure its ends. Make sure the line is just highenough for people to pass safely underneath.

2. Cut the coffee cup in halfso that the lip of the cupforms a continuous ring.

3. Loosen the balloons bypre-inflating them. Inflatethe first balloon aboutthree-fourths full of air andsqueeze its nozzle tight.Pull the nozzle through the ring. While someoneassists you, inflate the second balloon. The frontend of the second balloon should extend throughthe ring a short distance. As the second ballooninflates, it will press against the nozzle of the firstballoon and take over the job of holding it shut. It

may take a bit of practice to achieve this.4. Take the balloons to one end of the fishing line

and tape each balloon to a straw. The balloonsshould be pointed along the length of the fishingline.

5. If you wish, do a rocket countdown and releasethe second balloon you inflated. The escapinggas will propel both balloons along the fishingline. When the first balloon released runs out ofair, it will release the other balloon to continue thetrip.

other. The lowest stage is the largest and heaviest. Inthe Space Shuttle, the stages are attached side byside. The solid rocket boosters are attached to theside of the external tank. Also attached to the external

Discussion:Traveling into outer space takes enormous amountsof energy. This activity is a simple demonstration ofrocket staging that was first proposed by JohannSchmid lap in the 16th century. When a lower stagehas exhausted its load of propellants, the entirestage is dropped, making the upper stages moreefficient in reaching higher altitudes. In the typicalrocket, the stages are mounted one on top of the

tank is the Shuttle orbiter. When exhausted the solidrocket boosters are dropped. Later, the external tankis dropped as well.

Teaching Notes and Questions:Several launchings may be necessary to get thesecond "upper stage" balloon to travel completelyacross the classroom.Encourage the students to try other launcharrangements such as side-by-side balloons andthree stages.Can a two stage balloon be flown without the fishingline as a guide? How might the balloons be modifiedto make this possible?

Materials and Tools:2 Long party balloons ("airship")Nylon monofilament fishing line (any weight)2 Plastic straws (milkshake size)Styrofoam coffee cupMasking tapeScissors

35

Altitude TrackingObjective: To use geometry to estimate the altitude a water or bottle rocketachieves during flight.Description: In this activity, students construct simple altitude trackingdevices that are used to measure the angle a rocket reaches above ground, asseen from a remote tracking site. The angle is drawn on a graph and the altitudeis read from a scale.

Procedure: Constructing the AltitudeTracker1. Copy the Altitude Tracker pattern on white or

colored paper. Cut out the outline and glue thepattern to a piece of scrap file folder or posterboard. Do not glue the hatched area to the folder orposterboard.

2. Cut off the excess file folder or posterboard.3. Roll the hatched area at the top of the pattern into a

tube and tape the upper edge along the dashed lineat the lower edge. Shape the paper into a sightingtube.

4. Punch a tiny hole in the apex of the protrartorquadrant.

5. Cut out the Altitude Calculator and punch a hole atthe apex of its protractor quadrant. Glue theAltitude Calculator to the back of the tracker so thatthe two holes line up.

6. Slip a thread or lightweight string through the holes.Knot the thread or string on the calculator side.

5. Hang a small washer from the other end of thethread as shown in the diagram of the completedtracker.

Procedure: Using the Altitude Tracker1. Select a clear spot for launching water or bottle

rockets.2. Measure a tracking station location exactly 30

meters away from the launch site.3. As a rocket is launched, the person doing the

tracking will follow the flight with the sighting tubeon the tracker. The tracker should be held like apistol. Continue to aim the tracker at the highestpoint the rocket reached in the sky. Have a secondstudent read the angle the thread or string makeswith the quadrant protractor.

Procedure: Determining the Altitude1. Use the Altitude Calculator to determine the height

the rocket reached. To do so, pull the thread orstring through the hole in the tracker to the Altitude

36

30 meters

9

Materials and Tools:

Altitude Tracker patternsThread or lightweight stringScrap file folders or posterboardGlueCellophane tapeSmall washerScissors

Meter stick or steel tape measure (metric)

40

Calculator side until the washer stops it. Lay thestring across the protractor quadrant and stretch itso that it crosses the vertical scale. (See samplecalculation.)

2. Read the altitude of the rocket. The altitude is theintersection point of the string and the vertical scaleto that number. Add the height of the personholding the tracker to determine the altitude therocket reached.

Discussion:This activity makes use of simple trigonometry todetermine the altitude a rocket reaches in flight. Thebasic assumption of the activity is that the rockettravels straight up from the launch site. If the rocketflies away at an angle other than 90 degrees, theaccuracy of the procedure is diminished. For example,if the rocket flies toward a tracking station as it climbsupward, the altitude calculation will yield an answerhigher than the actual altitude reached. On the otherhand, if the rocket flies away from the station, thealtitude measurement will be lower than the actualvalue. Tracking accuracy can be increased, however,by using more than one tracking station to measurethe rocket's altitude. Position a second or third stationin different directions from the first station. Averagethe altitude measurements.

Teaching Notes and Questions:This activity is simple enough so each student canconstruct his or her own Altitude Tracker. Permiteach student to try taking measurements while otherstudents launch the rockets. To assure accuracy intaking measurements, practice measuring the heightof known objects such as a building or a flagpole. It

may also be necessary for a few practice launchesto familiarize each student with using the tracker inactual flight conditions.

Why should the height of the person holding thetracker be added to the measurement of the rocket'saltitude?

Curriculum guides for model rocketry (available frommodel rocket supply companies) provide instructionsfor more sophisticated rocket tracking measure-ments. These activities involve two station trackingwith altitude and compass direction measurementand trigonometric functions.

41

Altitude Calculator

Sample Calculationi

Altitude = 30 meters

90 80

Angle = 45 degrees

Tracking Station

\..

50

30

20

10

0 0

Launch Site

37

3 8

Roll this section over and tape the upperedge to the dashed line. Shape thesection into a sighting tube.

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10

This Altitude Tracker belongs to

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0

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0

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*

Additional Activities

Construct models of historical rockets.Refer to the reference list for picture bookson rockets to use as information on theappearance of various rockets. Use scrapmaterials for the models such as:

Mailing tubesTubes from paper rollsSpoolsCoffee creamer pac

plastic containerrocket engine n

CardboardEgg-shaped hosi

nose cones)Styrofoam con

cylindersGlueTap

Use roperspechoosing uneye view for pi

hy so manyn used for space

aceships.with

43

ac guided launch of commercial

cket kits and enginesfrom craft and hobby

ly from the manufacturer.Obtain addition information about modelrocketry by cont cting the NationalAssociation of Ri ketry, P.O. Box 177,Altoona, WI 5472Contact NASA S acelink for informationabout the history if rockets and NASA'sfamily of rockets nder the heading, "SpaceExploration Befo the Space Shuttle." Seethe resource secti n at the end of this guidefor details.

39

Glossary

Action A force (push or pull) acting on anobject. See Reaction.

Active Controls Devices on a rocket that moveto control the rocket's direction in flight.

Attitude Control Rockets Small rockets thatare used as active controls to change theattitude (direction) a rocket or spacecraft isfacing in outer space.

Canards - Small movable fins located towardsthe nose cone of a rocket.

Case The body of a solid propellant rocket thatholds the propellant.

Center of Mass (CM) The point in an objectabout which the object's mass is centered.

Center of Pressure (CP) The point in an objectabout which the object's surface area iscentered.

Chamber A cavity inside a rocket where propel-lants burn.

Combustion Chamber See Chamber.Drag Friction forces in the atmosphere that

"drag" on a rocket to slow its flight.Escape Velocity The velocity an object must

reach to escape the pull of Earth's gravity.Fins Arrow-like wings at the lower end of a

rocket that are used to stabilize the rocketin flight.

Fuel The chemical that combines with anoxidizer to burn and produce thrust.

Gimbaled Nozzles Tiltable rocket nozzles usedfor active controls.

Igniter A device that ignites a rocket'sengine(s).

Injectors - Showerhead-like devices that sprayfuel and oxidizer into the combustionchamber of a liquid propellant rocket.

Insulation A coating that protects the case andnozzle of a rocket from intense heat.

Liquid Propellant - Rocket propellants in liquidform.

Mass - The amount of matter contained within anobject.

Mass Fraction (MF) - The mass of propellants ina rocket divided by the rocket's total mass.

Motion Movement of an object in relation to itssurroundings.

40

Movable Fins - Rocket fins that can move tostabilize a rocket's flight.

Nose Cone - The cone-shaped front end of arocket.

Nozzle A bell-shaped opening at the lowerend of a rocket through which a streamof hot gases is directed.

Oxidizer - A chemical containing oxygencompounds that permits rocket fuel toburn both in the atmosphere and in thevacuum of space.

Passive Controls - Stationary devices, suchas fixed rocket fins, that stabilize arocket in flight.

Payload The cargo (scientific instruments,satellites, spacecraft, etc.) carried by arocket.

Propellant A mixture of fuel and oxidizer thatburns to produce rocket thrust.

Pumps Machinery that moves liquid fuel andoxidizer to the combustion chamber ofa rocket.

Reaction A movement in the oppositedirection from the imposition of anaction. See Action.

Rest The absence of movement of an objectin relation to its surroundings.

Regenerative Cooling Using the low tem-perature of a liquid fuel to cool a rocketnozzle.

Solid Propellant Rocket fuel and oxidizer insolid form.

Stages Two or more rockets stacked on topof each other in order to reach higheraltitudes or have a greater payloadcapacity.

Throat The narrow opening of a rocketnozzle.

Unbalanced Force A force that is not coun-tered by another force in the oppositedirection.

Vernier Rockets Small rockets that use theirthrust to help direct a larger rocket inflight.

4 4

NASA Educational Materials

NASA publishes a variety of educational resourcessuitable for classroom use. The following resources,specifically relating to the topic of rocketry, areavailable from the NASA Teacher Resource CenterNetwork. Refer to the next pages for details on how toobtain these materials.

Liftoff to Learning Educational Video Series

Space BasicsLength: 20:55Recommended Level: Middle SchoolApplication: History, Physical ScienceSpace Basics explains space flight concepts such ashow we get into orbit and why we float when orbitingEarth. Includes a video resource guide.

Newton in SpaceLength: 12:37Recommended Level: Middle SchoolApplication: Physical ScienceNewton in Space demonstrates the difference betweenweight and mass and illustrates Isaac Newton's threelaws of motion in the microgravity environment ofEarth Orbit. Includes a video resource guide.

Other Videos

Videotapes are available about Mercury, Gemini,Apollo, and Space Shuttle projects and missions.Contact the Teacher Resource Center that serves yourregion for a list of available titles.

Publications

McAleer, N. (1988), Space Shuttle The RenewedPromise, National Aeronautics and SpaceAdministration, PAM-521, Washington, DC.

NASA (1991), Countdown! NASA Launch Vehiclesand Facilities, information Summaries, NationalAeronautics and Space Administration, PMS-018-B,Kennedy Space Center, FL.

NASA (1991), A Decade On Board America's SpaceShuttle, National Aeronautics and SpaceAdministration, NP-150, Washington, DC.

NASA (1987), The Early Years: Mercury to Apollo-Soyuz, Information Summaries, NationalAeronautics and Space Administration, PMS-001-A,Kennedy Space Center, FL.

NASA (1991), Space Flight, The First 30 Years,National Aeronautics and Space Administration,NP-142, Washington, DC.

NASA (1992), Space Shuttle Mission Summary, TheFirst Decade: 1981-1990, Information Summaries,National Aeronautics and Space Administration,PMS-038, Kennedy Space Center, FL.

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Roland, A. (1985), A Spacefaring People:Perspectives on Early Spaceflight, NASA Scientificand Technical Information Branch, NASA SP-4405,Washington, DC.

Lithographs

HqL-311 Black Brant XII Sounding Rocket (colorlithograph with text)

HqL-367 Space Shuttle Columbia Returns fromSpace (color lithograph with text)

HqL-368 Space Shuttle Columbia Lifts Off Into Space(color lithograph with text)

Suggested Reading

These books can be used by children to learn moreabout rockets. Older books on the list providevaluable historical information rockets and informationabout rockets in science fiction. Newer books provideup-to-date information about rockets currently in useor being planned.

Asimov, I. (1988), Rockets, Probes, and Satellites,Gareth Stevens, Milwaukee.

Barrett, N. (1990), The Picture World of Rockets andSatellites, Franklin Watts Inc., New York.

Bran ley, F. (1987), Rockets and Satellites, Thomas Y.Crowell, New York.

Bolognese, D. (1982), Drawing Spaceships and OtherSpacecraft, Franklin Watts, Inc., New York.

Furniss, T. (1988), Space Rocket, Gloucester,New York.

Gat land, K. (1976), Rockets and Space Travel, SilverBurdett, Morristown, New Jersey.

Gat land, K. & Jeffris, D. (1977), Star Travel: Transportand Technoloily Into The 21st Century, UsbornPublishers, London.

Gurney, G. & Gurney, C. (1975), The Launch ofsputnik. October 4, 1957: The Space Age Begins,Franklin Watts, Inc., New York.

Malone, R. (1977), Rocketship: An Incredible VoyageThrough Science Fiction and Science Fact, Harper& Row, New York.

Quackenbush, R. (1978), The Boy Who Dreamed ofRockets: How Robert Goddard Became The Fatherof the Space Age, Parents Magazine Press,New York.

Vogt, G. (1987), An Album of Modern Spaceships,Franklin Watts, Inc., New York.

Vogt, G. (1989), Space Ships, Franklin Watts, Inc.,New York.

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NASA Educational Resources

NASA Space link: An Electronic Information System

NASA Space link is a computer information service that individuals may access to receive newsabout current NASA programs, activities, and other space-related information; historical data,current news, lesson plans, classroom activities, and even entire publications. Although it isprimarily intended as a resource for teachers, anyone with a personal computer and a modemcan access the network.

Users need a computer, modem, communications software, and a long-distance telephone line toaccess Space link. The Space link computer access number is (205) 895-0028. The data wordformat is 8 bits, no parity, and 1 stop bit. For more information contact:

Space link AdministratorMail Code CA21NASA Marshall Space Flight CenterMarshall Space Flight Center, AL 35812Phone: (205) 544-0038

NASA Space link is also available through the Internet, a worldwide computer network connectinga large number of educational institutions and research facilities. Callers with Internet accessmay reach NASA Space link at any of the following addresses:

spacelink.msfc.nasa.govxsl.msfc.nasa.gov192.149.89.61

NASA Educational Satellite Videoconferences

During the school year, NASA delivers a series of educational programs by satellite to teachersacross the country. The content of each videoconference varies, but all cover aeronautics orspace science topics of interest to the educational community. The broadcasts are interactive; anumber is flashed across the bottom of the screen, and viewers may call collect to ask questionsor to take part in the discussion. For further information contact:

Videoconference CoordinatorNASA Aerospace Education Services Program300 North CordellOklahoma State UniversityStillwater, OK 74078-0422Phone: (405) 744-7015

Technology and Evaluation BranchEducation DivisionCode FETNASA HeadquartersWashington, DC 20546

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NASA Select Television

NASA Select Television is the Agency's distribution system for live and taped educational programs. Theeducational and historical programming is aimed at inspiring students to achieve, especially in math-

ematics, science, and technology.

if your school's cable television system carries NASA Select, or if your school has access to a satelliteantenna, the programs may be downlinked and videotaped. NASA Select is transmitted on Sat Com

F2R, transponder 13, C-band, 72 degrees west longitude, frequency 3954.5 MHz, vertical polarization,audio on 6.8 MHz. A schedule for NASA Select is published daily on NASA Space link. For more

information contact:

NASA Selectdo Associate Administrator for Public AffairsNASA Headquarters, Code PWashington, DC 20546Teacher Resource Center Network

To make additional information available to the education community, the NASA Education Division hascreated the NASA Teacher Resource Center (TRC) network. TRCs contain a wealth of information foreducators: publications, reference books, slides, audio cassettes, videocassettes, telelecture programs,computer programs, lesson plans and activities, and lists of publications available from government andnongovernment sources. Because each NASA field center has its own areas of expertise, no two TRCsare exactly alike. Phone calls are welcome if you are unable to visit the TRC that serves your geographicarea. A list of the centers and the geographic regions they serve starts at the bottom of this page.

NASA's Central Operation of Resources for Educators (CORE) was established to facilitate thenational and international distribution of NASA-produced educational materials in audiovisual format.Orders are processed for a small fee that includes the cost of the media. Send a written request on yourschool letterhead for a catalogue and order forms. For more information contact:

NASA CORELorain County Joint Vocational School15181 Route 58 SouthOberlin, OH 44074Phone: (216) 774-1051, Ext. 293 or 294

OOOOO OOOOO

National Aeronautics and Space AdministrationInformation for Teachers and Students

IF YOU LIVE IN:AlaskaArizonaCaliforniaHawaiiIdahoMontana

ConnecticutDelawareDistrict of ColumbiaMaineMaryiandMassachusetts

NevadaOregonUtahWashingtonWyoming

New HampshireNew JerseyNew YorkPennsylvaniaRhode IslandVermont

Center Education Program OfficerChief, Educational Programs BranchMail Stop TO-25NASA Ames Research CenterMoffett Field, CA 94035PHONE: (415) 604-5543

Chief, Educational ProgramsPublic Affairs Office (130)NASA Goddard Space Flight CenterGreenbelt, MD 20771PHONE: (301) 286-7207

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Teacher Resource CenterNASA Teacher Resource CenterMail Stop TO-25NASA Ames Research CenterMoffett Field, CA 94035PHONE: (415) 604-3574

NASA Teacher Resource LaboratoryMail Code 130.3NASA Goddard Space Flight CenterGreenbelt, MD 20771PHONE: (301) 286-8570

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IF YOU LIVE IN: Center Education Program Officer

ColoradoKansasNebraskaNew Mexico

FloridaGeorgiaPuerto RicoVirgin Islands

KentuckyNorth CarolinaSouth CarolinaVirginiaWest Virginia

IllinoisIndianaMichigan

AlabamaArkansasIowa

Mississippi

North DakotaOklahomaSouth DakotaTexas

MinnesotaOhioWisconsin

LouisianaMissouriTennessee

The Jet Propulsion Laboratory (JPL)serves inquiries related to spaceand planetary exploration and otherJPL activities.

California (mainly cities nearDryden Flight Research Facility)

Virginia and Maryland'sEastern Shores

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Center Education Program OfficerPublic Affairs Office (AP-4)NASA Johnson Space CenterHouston, TX 77058PHONE: (713) 483-1257

Chief, Education and Awareness BranchMail Code PA-EABNASA Kennedy Space CenterKennedy Space Center, FL 32899PHONE: (407) 867-4444

Office of Education ProgramsMail Stop 400NASA Langley Research CenterHampton, VA 23681-0001PHONE: (804) 864-3307

Chief, Office of Educational ProgramsMail Stop 7-4NASA Lewis Research Center21000 Brookpark RoadCleveland, OH 44135PHONE: (216) 433-5583

Chief, Education Services BranchPublic Affairs Office (CA 21)NASA Marshall Space Flight CenterMarshall Space Flight Center, AL 35812PHONE: (205) 544-7391

Center Education Program OfficerMail Stop AA00NASA John C. Stennis Space CenterStennis Space Center, MS 39529PHONE: (601) 688-2739

Manager, Public Education OfficeMail Cooe 180-205Jet Propulsion Laboratory4800 Oak Grove DrivePasadena, CA 91109PHONE: (818) 354-8592

Teacher Resource Center

NASA Teacher Resource RoomMail Code AP-4NASA ,Johnson Space CenterHouston, TX 77058PHONE: (713) 483-8696

NASA Educators Resource LaboratoryMail Code ERLNASA Kennedy Space CenterKennedy Space Center, FL 32899PHONE: (407) 867-4090

NASA Teacher Resource CenterMail Stop 146NASA Langley Research CenterHampton, VA 23681-0001PHONE: (804) 864-3293

NASA Teacher Resource CenterMail Stop 8-1NASA Lewis Research Center21000 Brookpark RoadCleveland, OH 44135PHONE: (216) 433-2017

NASA Teacher Resource CenterAlabama Space and Rocket CenterHuntsville, AL 35807PHONE: (205) 544-5812

NASA Teacher Resource CenterBuilding 1200NASA John C. Stennis Space CenterStennis Space Center, MS 39529PHONE: (601) 688-3338

NASA Teacher Resource CenterJPL Educational OutreachMail Stop CS-530Jet Propulsion Laboratory4800 Oak Grove DrivePasadena, CA 91109PHONE: (818) 354-6916

NASA Dryden Flight Research FacilityPublic Affairs Office (Tri. 42)NASA Teacher Resource CenterEdwards, CA 93523PHONE: (805) 258-3456

Wallops Flight FacilityEducation Complex - Visitor CenterBuilding J-17Wallops Island, VA 23337PHONE: (804) 824-1176

II S. GOVERNMENT PRINTING OEFICE 1993- 356.114

Educators and scientists at the National Aeronautics and Space Administration wouldappreciate your taking a few minutes to respond to the statements and questions below.Please return by mail.

Rockets - Physical Science Teacher's Guide With Activities

1. The teaching guide is easily integrated into the curriculum.

:2. The procedures for the activities have sufficient information and are easily understood.

3. The illustrations are adequate to explain the procedures and concepts.

, 4. Activities effectively demonstrate concepts and are appropriate for the grade level I teach.

, 5. a. What features of the guide are particularly helpful in your teaching?

SA Strongly AgreeA - AgreeD - Disagree

SD - Strongly Disagree

SA A D SD

SA A D SD

SA A D SD

SA A D SD

b. What changes would make the guide more effective for you?

6. I teach grade. Subjects

7. I used the guide with (number of) students.

Additional comments:

EP-291

National Aeronautics and Space Administration

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONEDUCATION DIVISIONMAIL CODE FETWASHINGTON, DC 20546-0001

RACE STAMPHERE

POST OFFICEWILL NOTDELIVER

WITHOUT PROPERPOSTAGE

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