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Rocket Launching

Guiding Question

How fast did my rocket fly?

Objectives

Development of fine motor skills
Develop students' ability to read, comprehend and follow instructions
Introduction to Rocketry
Introduction to Rocket Science

Concepts

Newton's laws of motion control the motion of a spacecraft.
Rocketry
Trigonometry

Principles

Rocket. A transportation device containing at least a rocket engine, fuel, and a payload.
Rocket Engine. A propulsion motor to drive a rocket.
Fuel. Liquid or solid propellant used in an internal reaction to provide thrust for a space rocket.
Combustion Gravity. The force of attraction between two bodies such as the earth and you.
Thrust. The propulsion force generated by a rocket during firing. A rocket's thrust is used to escape the force of gravity.
Drag. The resistance of air in the upper atmosphere to the motion of a satellite or other airborne vessels.
Speed. The rate at which an object travels over time, i.e. ft/sec, miles per hour.
Velocity. The direction and rate of displacement over time, i.e. 12 ft/sec north, 60 mph forward.
Acceleration. The rate at which the velocity of an object increases, ft/sec*sec.
Deceleration. The rate at which the velocity of an object decreases.
First Law of Newtonian Motion. Unless acted upon by an outside force, an object at rest or in motion will remain at rest or in motion with the same speed and direction.
Second Law of Newtonian Motion. The change in motion of an object acted upon by an outside force is directly proportional to the force and inversely proportional to the object's mass.
Third Law of Newtonian Motion. Every action force has a reaction force equal in magnitude and opposite in direction. Usually stated as, to every action there is an equal and opposite reaction. Atmosphere Flight
Trajectory Escape Velocity. The speed required for a rocket to leave a planet or celestial body without falling into orbit around it.
Orbit. The closed elliptical path travelled through space by an object around another object, following Newton's laws of gravitation and motion.
Microgravity. The space science term for the nearly-zero gravity of Earth orbit.

Materials

Estey's Alpha Rocket Kit
Super-glue
Glue Resolvent/Remover
Metric Ruler
Scissors
Exact Knives
Table Protection
Pencils
Calculators
Table of tangent angle values
Students' copy of Rocket Launching Lesson
Room Preparation

Protect desktops from glue spills and knife cuts by covering desks with newspapers and providing your students with cardboard on which to construct their rockets.

Explain lesson and handout lesson pages to students.

Safety

It is recommended that children below the fifth grade DO NOT handle Exacto or artist's knives for this project. Only the instructors should use the hobby knives when necessary.

Procedures and Activities

History of Rockets

Modern Rockets first were developed in World War II when Germany designed the V2 missile. Since that time, rockets have evolved into a means of transporting things such as satellites and people out into space. A vehicle as complex as the Space Shuttle (shown to the right) has many different types of rockets, such as Liquid fuel booster rockets, Solid Fuel booster rockets, and orbital maneuvering rockets. Rockets run by mixing a fuel and something called an oxidizer (taken from the word oxygen). When the fuel and the oxidizer are mixed, and heated to a high enough temperature, they ignite, and burn. When the fuel and the oxidizer burn, they release energy. This energy is used to propel the rocket into the air. This is similar to the engines on the big passenger airlines you see at the airports. However, rocket engines are different than jet engines in that rocket engines carry both the fuel and oxidizer with them, while jet engines bring only the fuel, and take the oxygen from the air around the jet. This is why you will find on the Space Shuttle both Liquid Hydrogen (the fuel) and Liquid Oxygen (the oxidizer) tanks on board. This is also the reason that rocket engines instead of jet engines are required if you want to get something out into space. Why, you might ask? Is there any oxygen out in space for a jet engine to use? There is no atmosphere out in space, thus, there is no oxygen, and therefore, a jet engine would not work out in space.

The Rocket Lesson

Today you are going to build your own rocket, and later on in the lesson, you will actually launch the rocket, take some data, and figure out some things about the rocket. But first, we must go over some terms so that you can understand some things about rockets.

Newton's Law, Force & Acceleration

A long time ago, there was a scientist called Isaac Newton. Being a very observant person, he noticed that when an object is moved from one place to another, there is a relationship between force, mass and acceleration. His formula is shown below:

F = m x a

Where F is the force, m is the mass of the object being moved, and a is the acceleration of the object. But what is the difference between force and acceleration? Consider the following example.

Imagine you're in a sports car stopped at a traffic light. When the light turns green, the driver slams on the gas. After squealing the tires, the car zooms up to 55 mph. What do you feel? First of all, you are pushed back into your seat, then as you get up to 55 mph, you feel normal again.

Now imagine you are at the same traffic light, but this time sitting in a small subcompact car. When the light turns green, the driver slams on the gas. Because this is a small car has a very weak engine, and the car slowly goes faster and faster until it gets up to 55 mph. What do you feel? Not a whole lot.

What is the difference between these two cars? They both started from a stop. They both end at 55 mph. The difference is that one reached 55 mph much faster than the other. Or, in other words, the sports car accelerated much faster than the sub-compact car. Since you're sitting in the car, you accelerated as fast as the car did. This acceleration created a force on you--one that pushed you back in your seat. Therefore, acceleration is how quickly you get something moving, while a force is a push you can feel.

Returning to Newton, he realized that there was a relationship between acceleration and force, and also the mass of something. This can be seen by another example. Imagine you drop a ping-pong ball on your foot. No big deal. Now imagine dropping a bowling ball on your foot. Ouch! What is the difference? In this example, you have an acceleration: Gravity. Yes, Gravity is a form of acceleration. You have the same acceleration for both the ping-pong ball, and the bowling ball, but you have different masses. Obviously, the bowling ball weighs more than the ping-pong ball. Which one is going to hurt more (create the most force on your foot)? The bowling ball!. So indeed, the mass of the object being accelerated changes the force involved.

With these examples in mind, Newton's Law makes a lot of sense. But how does it apply to rockets?

The rocket has a certain amount of mass, and gravity is an acceleration downwards. Therefore, with the rocket sitting on the ground, it will cause a certain amount of force pushing against the earth. This force is the rockets' weight. To get the rocket to launch into the air, there must be a greater force pushing the rocket upwards than there is pushing the rocket downwards. This force pushing it upwards is called the thrust.. Thrust is generated when the rocket engine burns the fuel and oxidizer, and shoots it out the bottom at very fast speeds.

With this you know enough to start building your own rocket, and understand some of the things happening to your rocket as it goes up in the air when you launch it, later on in the lesson.

The directions for building your rocket are included in the rocket kit. Follow them carefully to build your own rocket!

Rocket Pre-Launch Preparation

Parachute preparation

Crumple up (loosely) three sheets of recovery wadding
Fold parachute in half four times, so that all the parachute lines wind up together.
Loosely wrap the lines around the chute and place the parachute in the rocket body.
Put the shock cord on top of the parachute and cap the rocket with the nose cone.

Engine Preparation

Slide the engine into the rocket body and make sure the engine hook latches the engine into place.
Insert black end of the ignitor into the engine and use either the yellow plug or a piece of masking tape to hold the ignitor in the engine.

Launch Safety

There are a few rules that everyone MUST follow.

The only time you should approach the launch pad is if you have the safety key in your hand. The rocket cannot launch with out the safety key being in the ignition controller. This way, there is no risk of the rocket accidentally being launched with you standing right next to it.
Before you launch the rocket, count down from 5. This way, everyone is alerted to the fact that a rocket is about to be launched, and nobody will get hurt by walking up to the rocket.

Model Rocket Data Worksheet

Record the performance data for your rocket.

time to parachute opening = (seconds)
time from parachute opening to rocket hitting ground = (seconds)
angle (°) =
distance to telemetry station = (feet)
Convert the distance to meters by multiplying the number of feet by 0.3048: distance = ______________________ _(meters) …

Find out how high your rocket traveled.

Look up the tangent for your angle in the Table of Tangents.
tangent(angle) = actual height = (distance to telemetry station) X (tangent) actual height = (feet)
Convert the height to meters (Multiplying the number of feet by 0.3048): height = (meters)

Find out the mass of your rocket.

Mass = (grams)
Convert both of these to kilograms, by dividing the grams by 1000: Mass = (kg)

Find out the weight of the rocket.

Weight = (Mass in kg) x (9.8 meters/sec²) weight = (Newtons)

Find the overall average acceleration of the rocket as it goes up.

Use the height in meters!
Overall acceleration of rocket (including effect of gravity) = (m/s²)
Get the average acceleration because of the rocket engine.
Acceleration due to engine = (Average acceleration) + (9.8 m/sec²)
This is what the overall acceleration of the rocket would be if there was no gravity.
Acceleration due to rocket engine = (m/s²)

Calculate the average thrust of the rocket engine.

Thrust = (Initial mass) x (acceleration because of rocket engine)
average thrust of engine = (Newtons)
Convert this to pounds by dividing by 4.45
average thrust of engine = (pounds)

Calculate the acceleration of the rocket while it parachutes to the ground.

acceleration down = (m/s²)
Find the drag of the parachute.
Drag = (mass ) x (9.8 - acceleration down)
Drag of parachute = (Newtons)

Calculate the thrust-to-weight ratio of your rocket.

Thrust-to-Weight Ratio = (T / W)
Compare your thrust results to the numbers for the Space Shuttle: For the Space Shuttle at liftoff, Thrust (at liftoff) = 28,650,000 Newtons, or 6,400,000 pounds. Initial Weight = 20,000,000 Newtons, or 4,500,000 pounds.
Calculate the thrust-to-weight ratio of the shuttle at liftoff:
T/W = ___________

Questions

Is your T/W less than, the same, or higher than that for the Shuttle?
Why? (What would happen if T/W for the Shuttle was the same as the T/W you calculated for your rocket?)
What would happen if T/W was less than one at liftoff?
Why do the Shuttle and your rocket have such different thrusts?
How does your computed drag compare to your computed thrust? Why?
What are the units of thrust-to weight ratio? How do these units make the thrust-to-weight ratio useful?

Table of Tangents

Angle	Tangent(angle)	Angle	Tangent(angle)	Angle	Tangent(angle)
0	0.0000	30	0.5773	60	1.7317
1	0.0175	31	0.6008	61	1.8037
2	0.0349	32	0.6248	62	1.8804
3	0.0524	33	0.6493	63	1.9622
4	0.0699	34	0.6744	64	2.0499
5	0.0875	35	0.7001	65	2.1440
6	0.1051	36	0.7265	66	2.2455
7	0.1228	37	0.7535	67	2.3553
8	0.1405	38	0.7812	68	2.4745
9	0.1584	39	0.8097	69	2.6044
10	0.1763	40	0.8390	70	2.7467
11	0.1944	41	0.8692	71	2.9033
12	0.2125	42	0.9003	72	3.0767
13	0.2309	43	0.9324	73	3.2698
14	0.2493	44	0.9656	74	3.4862
15	0.2679	45	0.9999	75	3.7306
16	0.2867	46	1.0354	76	4.0091
17	0.3057	47	1.0722	77	4.3295
18	0.3249	48	1.1105	78	4.7023
19	0.3443	49	1.1502	79	5.1418
20	0.3639	50	1.1916	80	5.6679
21	0.3838	51	1.2347	81	6.3095
22	0.4040	52	1.2798	82	7.1099
23	0.4244	53	1.3269	83	8.1372
24	0.4452	54	1.3762	84	9.5045
25	0.4663	55	1.4279	85	11.4157
26	0.4877	57	1.5396	87	19.0404
28	0.5317	56	1.4823	86	14.2780
27	0.5095	57	1.5396	87	19.0404
28	0.5317	58	1.6001	88	28.5437
29	0.5543	59	1.6640	89	56.9168