Physics Model Rockets Project Name: ________________
Mr. Andrade Instructions and resources Class Period: _____
Introduction
Model rockets provide the physics student first an opportunity to apply the physics of rocket propulsion and projectile motion to develop a theoretical model that predicts the maximum
altitude of the model rocket, and second an opportunity to build and launch the rocket and obtain experimental results to compare with the predictions.
Your group will design, build and launch a model rocket. You will be provided with a model rocket kit. Each group will be provided with one A8‐3 model rocket engine. If time permits on launch day, we may launch them a second time.
Your group will be required to create a report that includes data from your rocket, the assigned research and a reflection on the effectiveness of your rocket. Make sure to include a works cited page for all research and graphics you use. You must research the following topics: Aerodynamics, Forces on a Model Rocket, Model Rocket Engines, Model Rocket Safety.
The flight of the rocket can be divided into three basic stages: the boost phase; the coast phase; and the return phase. The boost phase is the stage of flight that is powered by the rocket motor. The rocket undergoes approximately constant acceleration to attain its maximum velocity. Next is the coast phase. In this stage, the rocket undergoes negative acceleration due to gravity, coasting to its maximum altitude, also called the apogee. The final stage is the return phase, where the recovery system is deployed and the rocket falls back to the ground. By taking a close look at the forces involved in the boost and coast phases, it is possible to calculate the acceleration at each phase and then predict the maximum altitude of the rocket.
Great website (used during your webquest) for information: http://exploration.grc.nasa.gov/ education/rocket/
Other resource sites:
http://www.unclemikesrocketshack.com/Kids_Page/Estes_Manuals/Elem_Math.pdf
Supplies needed
Model rocket kit white glue Hobby knife Sandpaper Masking tape Rocket motor Wadding
String or thread
Weights (3) such as nuts, washers, or erasers
Name the three stages of the flight of a rocket.
What is the apogee?
In which phase does the rocket reach its apogee?
In which phase is the recovery system deployed?
In which phase is the rocket accelerating to maximum velocity?
Calculations
To calculate the maximum height the rocket should attain, these basic physics equations are used: F = ma, vf = at, and s = vit + ½ at2
In using these equations, certain assumptions are made. We assume that air friction is constant, that weight loss is negligible, and that engine thrust is constant.
At t = 0, the starting height and initial velocity (vi) = 0.
First we will need to know the mass of your rocket, the mass of a new motor, and the mass of a used motor. The mass of the rocket can be found on the package the kit came in. The mass of the motor and the propellant can be found on the Estes Engine Chart at http://www.v-serv.com/ usr/motors/estes/EstesEngineSpecs.pdf . Record them here. Make sure your readings are in kilograms.
m rocket = _____________kg
m new motor = _____________kg
m used motor = ______________kg
To fire the rocket, an igniter made up of a strip of resistance wire coated with pyrotechnic material is inserted into the motor so that the igniter is in contact with the propellant. The igniter works like a resistor in an electrical circuit, heating up until the pyrotechnic material ignites. This in turn ignites the propellant.
The burn rate of the propellant is proportional to the exposed surface area of the propellant. This surface area changes as the propellant burns producing a large initial thrust then settles into a fairly constant area or thrust.
The total impulse of a rocket motor is the average force produced times the length of time it is produced. It is measured in Newton-seconds.
The effective thrust of the motor, or net force, can be calculated by taking the thrust of the motor and subtracting the two opposing forces: air friction and gravity. We will use 0.7 N as the force of air friction.
The rocket motor has a three-part code on it, such as B6-4.
● The letter (sometimes preceded by a fraction) indicates the total impulse (I) of the motor. An “A” motor has a total impulse of 2.50 N-s. ½ A is half of 2.50 or 1.25 N-s. A “B” motor has a total impulse of 5.00 N-s, and a “C” motor has 10.00 N-s of total impulse. This figure will be used later to calculate the burn time.
● The second part of the code is a number, in this case 6. This number is the average thrust of the motor in Newtons. This is the number used in the equations for FT. ● The third part, 4 in our example, is a number that indicates the time delay in seconds
before the recover ejection. The rocket should reach its maximum altitude before the recovery ejection occurs.
A rocket motor is labeled A8-3.
What is the time delay of this motor?
What is the total impulse?
What is the average thrust?
The following graph is from the NASA website:
http://www.grc.nasa.gov/WWW/K-12/airplane/rktengperf.html
The mass of the rocket changes as the propellant burns. To compensate for this change in mass, the average mass of the rocket and motor will be used.
m ave = m rocket + (m new motor + m used motor)/2
F net = FT – m ave* g – Fair
Now calculate the average mass and effective thrust of your rocket.
m ave = ____________kg
By rearranging the equation F = ma, we can calculate the acceleration during the boost phase. a boost = F net / m ave
The burn time is calculated by dividing the total impulse by the average thrust of the motor. t burn = I / F T
The final velocity of the boost phase, which will be the initial velocity of the coast phase, is calculated using the acceleration and the time to burnout.
v f(boost) = a boost * t burn
Calculate the acceleration, burn time, and final velocity of the boost phase for your rocket.
a boost = ___________m/s2
t burn = ____________s
v f(boost) = _____________m/s
The altitude (s) the rocket will reach during the boost phase is calculated using the equation: s = vit burn + ½ a boostt burn2.
Calculate the altitude your rocket will reach during the boost phase. (Remember the initial velocity is 0).
s boost = _____________m
During the coast phase of the rocket flight, the mass is simply the mass of the rocket and the mass of the used motor. The force during this phase is simply gravity and air friction both in a negative direction.
m coast = m rocket + m used motor
F coast = – m coast* g – Fair
Calculate the mass and force during the coast phase of your rocket.
m coast = ___________kg
F coast = ___________N
The acceleration and time of the coast phase are calculated using the equations:
a coast = F coast /m coast
tcoast = v f(boost) / a coast
Calculate the acceleration and time of the coast phase of your rocket.
a coast = _____________ m/s2
t coast = _____________s
s coast = v f(boost) * t coast + ½ a coast * t coast 2
The maximum altitude the rocket will reach is the sum of the boost phase and coast phase.
Calculate the additional altitude of your rocket during the coast phase and the maximum altitude your rocket will reach on its flight.
s coast = _____________m
s total = _____________m
If the baseline is 50m and the measured angle is 135°, what is the maximum altitude of the rocket?
Calculate the maximum altitude for each of your flights using the equation: Altitude = baseline / tan (angle)
Record the maximum altitudes in the table.
Flight 1
Flight 2
Flight 3 Spotter 1
Spotter 2 Spotter 3 Average Length of
Baseline Maximum
Altitude
How does the measured maximum altitude compare with the predicted maximum altitude?
Using the predicted value as a base, calculate the percent difference from the base for each of the flights. ((Predicted value – measured value)/ Predicted value) * 100
Flight 1 _____________
What are some things that might account for these differences?
(optional if we have time:)
NASA has a rocket flight simulator called the RocketModeler on its website:
http://www.grc.nasa.gov/WWW/K-12/airplane/rktsim.html
Use the RocketModeler with the dimensions of your rocket. What does the RocketModeler predict as the maximum altitude?
How does this figure compare with your prediction and results?
To give you a better understanding of the velocity of a model rocket, let’s look at the maximum velocity of a model rocket and compare that with the velocity of other familiar objects. In this section, the more familiar English units will be used.
A small, lightweight rocket with a powerful motor reaches a maximum velocity of 670 feet per second. How fast is that in miles per hour?
A much heavier rocket with a smaller motor reaches a maximum velocity of 84 feet per second. How fast is that in miles per hour?
A Boeing 747 has a cruising speed of 570 miles per hour. How fast is that in feet per second?
A man walking at a steady pace averages about 3 miles per hour. How many meters per second is that?
Project Report
Write a lab report of building and launching your model rocket. You may work with your team to write the report, but each person must turn in their own report.
(For most labs use Title given on lab instructions.)
II. PURPOSE (2pts) (A simple statement of the purpose of the lab or the problem being solved. This may be written as a question or as a statement.)
III. INTRODUCTION (preliminary observations, known facts, (5pts)Dependent/Independent Variables (5pts), “If …then” hypothesis.(5pts) Sources.) This should be a minimum of 3 paragraphs. (Informative) Include: Newton’s three laws and the basic concept of how a model rock works.
● 1st Paragraph: How a Model Rocket shows Newton’s First Law
● 2nd Paragraph: How a Model Rocket shows Newton’s 2nd Law and include your hypothesis on how
high you think your rock will go and what will determine that.
● 3rd Paragraph: How a model Rocket shows Newton’s 3rd Law.
Google Search:
● How model rockets work.
● How model rocket engines work.
● Newton’s Laws and Model Rockets
● The physics behind Model Rockets
IV. MATERIALS (5pts)(This must be a list)
V. METHODS (Both summary (5pts)and Numbered steps, reproducible, diagrams (5pts) (10pts total for Methods)
Narrative Essay (3 paragraphs-Building, Launch and Recovery) ● 1st Paragraph: Narrative of how your build your rocket.
● 2nd Paragraph: Narrative of how your prepared your rocket for launch and launching.
● 3rd Paragraph: Narrative of how your rocket was recovered. (From the point it quit increasing in altitude (going up) to the point when it was back in your hand. Include a description of the condition of your recovered rocket.
-Summarize in 5 complete sentences how you built and launched. (Add after you launch your rocket.) -List the steps of building the rocket and launching the rocket.
-Include diagrams, etc.
VI. DATA / RESULTS
-After launch: Approximate altitude. -Observation of Launch and Recovery -Observation of how high your rocket went.
VII. ANALYSIS (10pts)
-Write a 3 paragraph informative essay on the entire Rocket building and launching experience, likes, dislikes, comments, data, etc.
Include all of your data and calculations from this packet also.
VIII. CONCLUSION
IX. Literature Cited (6pts)
It is up to you to select the most useful references. All references cited in your report must appear in the literature cited section. 3 references minimum with 3 sources listed separately below reference summaries.