6 th Grade Model Rocket Program
The 6 th Grade Rocket Program • Day 1 – Investigate how and why a rocket works – Determine what we will measure with our rocket • Day 2 – Predict how high the rocket will fly and what our instruments will measure – Launch the rocket! • Day 3 – Compare our predictions to what we measured with the instruments on the model rocket 2
Today, we will… • Identify the parts of a model rocket • Describe the motion of a model rocket • Calculate the altitude of a model rocket Then, we will answer three questions • What can we measure with a rocket? • What will the measurements look like? • How will we make these measurements? 3
Parts of a rocket 4
Picture of model rocket flight
Model rocket engine Coast Phase Ejection charge to deploy the recovery system Thrust Phase Non-thrust delay and smoke tracking charge High thrust charge for lift-off and acceleration 6
How do you describe the motion of a rocket? • What is the rocket’s position ? – Altitude – 332 meters high • How fast is the rocket changing its position ? – Velocity – 75 meters/second • How fast is the rocket’s velocity changing ? – Acceleration – 98 meters/second/second 98 meters/second 2 7
Velocity • Measures the distance moved per unit of time • Unit of measure • Meters per second, kilometers per hour, miles/hour • Examples – Walking quickly = 10 km/hour = 2.8 m/sec – Car on freeway = 100 km/hour = 28 m/sec – Jet in flight = 1,000 km/hour = 280 m/sec – Space shuttle = 27,000 km/hour = 7,500 m/sec • Experiments – How fast am I moving? – How far did I travel? 8
Acceleration • Measures the change in velocity per unit of time • Units of measure • Meters per second per second • Kilometers/hour 2 • Examples – Acceleration of gravity = 1 g or 9.8 meters/second 2 – Shuttle Thrust Phase produces 3 g – Blackout occurs at 4 – 6 g’s without special “anti-g suit” – Jet fighter acceleration = 9 g’s 9
How can we predict the motion of a rocket? Observations for rockets • How far will I travel in t seconds? If v 1 = 0, then d = ½ a • t 2 • – d = v 1 • t + ½ • a • t 2 [1] • If a = 0, then d = v • t • How far will I travel at velocity v? 2 – v 1 2 ) / (2 • a) [2] – d = (v 2 If v 1 = 0, then d = v 2 /(2 • a) • • How fast will I go in t seconds? – v 2 = v 1 + a • t [3] • If v 1 = 0, then v = a • t • Definitions – d = distance traveled – v 1 = velocity at start of time period – v 2 = velocity at end of time period – a = acceleration 10
How do we use these concepts? • A skydiver jumps out of an airplane 1,000 meters above the ground – Initial velocity = 0 meters/second – Acceleration = 9.8 meters/second/second • The acceleration of gravity on Earth • How fast am I going after 1 second? 10 seconds? • How far have I traveled after 1 second? After 10 seconds? 11
Skydiver summary 0 seconds 1 second 10 seconds 9.8 m/sec 2 9.8 m/sec 2 9.8 m/sec 2 acceleration 98 m/sec velocity 0 m/sec 9.8 m/sec 490 m distance 0 m 4.9 m • After 10 seconds, the skydiver is going 3.5 times faster than a car on the freeway! • After 10 seconds, the skydiver is almost ½ way to the ground! 12
What determines the motion of a rocket? Newton’s 3 Laws of Motion 1. A body remains at rest, or in motion with a constant velocity, unless acted upon by an unbalanced force. 2. Acceleration = Force / mass 3. For every action (force) there is an equal and opposite re-action. Sir Isaac Newton 1686 13
3 Forces determine a rocket’s flight Drag • Thrust – Determined by the rocket engine • Gravity – Acceleration of gravity (g) = 9.8 meters/second/second Thrust • Drag or air resistance – Caused by the rocket moving through the air – Determined by the diameter of the rocket, Gravity shape of the rocket, and other factors • Force Total = F Thrust – (F Drag + F Gravity ) – Measured in Newtons 14
How high will a rocket go? Thrust Phase Coast Phase • Thrust pushes the rocket • Engine burnout, so the upward thrust is zero • Gravity pulls the rocket • Gravity pulls the rocket down down • Drag slows the rocket • Drag slows the rocket • F Total = F Thrust – (F Drag + • When the rocket reaches F Gravity ) apogee – Velocity = 0 – Acceleration = 0 • F Total = F Drag + F Gravity Altitude Total = Altitude Thrust phase + Altitude Coast phase 15
How high will a rocket go (ignoring drag)? Altitude Total = Altitude Thrust phase + Altitude Coast phase Thrust Thrust Phase F Total = F Thrust – F Gravity A upward = A rocket – A gravity A upward = (Engine thrust/Rocket mass) – g Altitude Thrust Phase = ½ A upward • t 2 Gravity Coast Phase F Total = F Gravity V burnout = A upward • t thrust duration Gravity Altitude Coast Phase = V 2 burnout / (2 • g) 16
Example Calculation • A small model rocket – the micro V2 – 17.8 cm long – 1.89 cm diameter – Rocket • Mass = 0.028 kg • Weight = 0.27 Newtons – Engine • Thrust = 10.7 Newtons • Thrust duration = 0.5 seconds • How high will this rocket fly? 17
Small model rocket example Thrust Phase Coast Phase A upward = 372.3 m/sec 2 V burnout = 186.2 m/sec = 38 g’s Altitude = 1,768.4 meters Altitude = 46.5 meters Altitude Total = 1,814.9 meters Observations – During Thrust Phase - rockets gain a small amount of altitude and a large velocity – During Coast Phase - rockets gain most of their altitude 18
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Observations • Drag has a large impact on the altitude of the rocket at apogee – Calculating drag is complicated (trust me!) • Rockets gain a small amount of altitude and a large velocity during the Thrust Phase • Rockets gain most of their altitude during the Coast Phase • Model rockets go really fast and very high! 21
Group Activity • What can we measure during the flight of a model rocket? 22
What do the measurements look like? 23
How are the measurements made? Rocket Data Acquisition System (R-DAS) The CPU, or brain to do all the work Memory The program, or to record all the data instructions, to tell the CPU what to do. 1. Wait for lift-off 2. After lift-off, take measurements The sensors that measure the data 200 times/sec 24
6 th Grade Model Rocket Program Day 2
Today, we will… • Calculate the altitude for our rocket launch – We will ignore drag in the calculations – Extra credit – predict the altitude at apogee with drag • Predict the change in temperature for our flight • Discuss safety on the rocket range • Launch the rocket!! • Record the data (if we have time) 26
Group activity • Break into shipwreck groups • Complete the altitude calculation worksheet • Predict how the temperature will change during the flight – Draw a graph and show how the temperature will change with altitude • Y-axis = temperature temperature • X-axis = altitude altitude 27
Rocket Worksheet • Equations of motion – a upward = a rocket engine – a gravity – a upward = (engine thrust / total mass of the rocket) – g – altitude burnout = ½ • a upward • t 2 where t = thrust duration – v burnout = a upward • t where t = thrust duration 2 / (2 • g) where g = 9.8 m/sec/sec – altitude Coast phase = v burnout – altitude total = altitude burnout + altitude Coast phase Quantity Value Units ������������������� ������������������� a upward = ������������������� ������������������� altitude burnout = ������������������� ������������������ v burnout = �������������������� ������������������� altitude Coast phase = �������������������� �������������������� altitude total = 28
Temperature vs. Altitude Temperature Slope ~ 0.02 ° C/m Altitude 29
Launch site safety rules • Everyone stand behind the launch table at all times • Do not run up to the rocket when it lands. You can trip and fall on the rocket and break it! – Yes, it happened to me! • Only teachers are allowed to install the engine and ignite it. 30
6 th Grade Model Rocket Program Day 3 31
Today, we will… • Compare the data collected yesterday with your predictions – Each group will present their predictions, observations, and conclusions to the class • Where can you learn more about rockets? • Discussion on the 6 th Grade Model Rocket Program 32
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Other model rocketry resources • Handbook of Model Rocketry by G. Harry Stine – The best book on all aspects of model rocketry • www.nar.org – The National Association of Rocketry • www.estes.com – Manufactures model rocket kits and engines • www.nasa.gov – Search for “model rocket” – lots of information! • Local hobby stores and rocketry clubs 35
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