Rocketry Unit

1
Rocketry Unit

• Physics
• McFall
• 7th Period

2
Newton's First Law

• Objects at rest will stay at rest, and objects in
  motion will stay in motion in a straight line
  unless acted upon by an unbalanced force.
• 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 are ignited, the thrust from
  the rocket unbalances the forces, and the rocket
  travels upward. Later, when the rocket runs out
  of fuel, it slows down, stops at the highest
  point of flight, then falls back to the Earth.

3
Newton's Second Law

• F ma - Force is equal to mass times
  acceleration.
• Force in the equation can be thought of as the
  thrust of the rocket engine. Mass in the equation
  is the amount of rocket fuel being burned and
  converted into gas that expands and then escapes
  from the rocket. Acceleration is the rate at
  which the gas escapes. Inside the rocket, the gas
  does not really move, but as it leaves the engine
  it picks up speed.
• Newton's second law of motion can be restated in
  the following way the greater the mass of rocket
  fuel burned and the faster the gas produced can
  escape the engine, the greater the thrust of the
  engine.

4
Newton's Third Law

• For every action there is always an opposite and
  equal reaction.
• With rockets, the action is the expelling of gas
  out of the engine. The reaction is the movement
  of the rocket in the opposite direction. To
  enable a rocket to lift off from the launch pad,
  the action, or thrust, from the engine must be
  greater than the weight of the rocket.

5
Putting Newton's Laws of Motion Together

• An unbalanced force must be exerted for a rocket
  to lift off from the launch pad (first law). The
  amount of thrust (force) produced by a rocket
  engine will be determined by the mass of the
  rocket fuel that is burned and how fast the gas
  escapes the rocket (second law). The reaction, or
  motion, of the rocket is equal to and in an
  opposite direction from the action, or thrust,
  from the engine (third law).

6

• Parts of a Model Rocket

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Nose Cone

• The foremost surface of a model rocket, generally
  tapered in shape, usually made of balsa or
  plastic. It reduces drag by directing airflow
  smoothly around rocket.

8
Body

• A specially wound and treated cardboard or
  plastic cylinder used to make the fuselage or
  airframe of a model rocket to which all other
  parts are attached.

9
Recovery System

• The device in a model rocket whose purpose is to
  return the rocket to the ground safely by
  creating excess drag or by creating lift. All
  model rockets must employ a recovery system, such
  as a parachute.

10
Launch Lug

• Round, hollow tube (attached to the model rocket)
  which slips over the launch rod to guide the
  model during the first few feet of flight until
  sufficient airspeed is reached allowing the fins
  to operate.

11
Recovery Wadding

• Flame resistant tissues that are packed between
  the model rocket engine and the streamer or
  parachute to protect the recovery device from the
  hot gases of the ejection charge.

12
Fins

• The stabilizing and guiding unit of a model
  rocket. The aerodynamic surfaces projecting from
  the rocket body for the purpose of giving the
  rocket directional stability. Usually made of
  balsa wood or plastic, and located at the rear of
  the rocket.

13
Engine Mount

• Safely secures the engine in a model rocket.
  Sometimes includes an engine hook.

14
Total Impulse

• Total impulse is a measure of the overall total
  energy contained in a motor, and is measured in
  Newton-seconds. The letter "C" in our example
  engine above tells us that there is anywhere from
  5.01 to 10.0 N-sec of total impulse available in
  this engine.
• Since each letter represents twice the power
  range of the previous letter, total available
  power increases rapidly the further you progress
  through the alphabet.

15
Average Thrust

• Average thrust is a measure of how slowly or
  quickly the motor delivers its total energy, and
  is measured in Newtons. The "6" in our example
  motor tells us that the energy is delivered at a
  moderate rate (over about 1.7 seconds). A C4
  would deliver weaker thrust over a longer time
  (about 2.5 seconds), while a C10 would deliver a
  strong thrust for a shorter time (about a
  second).
• As a rule of thumb, the thrust duration of a
  motor can be approximated by dividing its total
  impulse by its average thrust.
• Keep in mind that you cannot assume that the
  actual total impulse of a motor lies at the top
  end of its letter's power range - an engine
  marked "C" might be engineered to deliver only
  5.5 Newton-seconds, not 10.

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Motor Parts
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• Paper Casing
• A paper cover that protects the charges of a
  model rocket engine and confines the internal
  pressure during combustion allowing the exhaust
  gas to escape through the nozzle.
•  
• Clay Nozzle
• A device on the bottom end of an engine that
  channels the exhaust gas through the nozzle
  throat to greatly increase the exhaust gas speed
  which in turn develops thrust.
•   Propellant
• A chemical paste of a combustible nature, that
  has been commercially developed and loaded in the
  casing of a model rocket engine that when ignited
  will provide the thrust necessary to launch a
  model rocket.

18

• Coast or Delay Phase
• A no thrust, slow burning charge that emits smoke
  to aid in tracking and allows the rocket to coast
  to a higher altitude before activation of the
  ejection charge for recovery system deployment.
•  
• Ejection Charge
• Ignited by the delay element and produces
  expanding gases which activate or eject a
  recovery device.
•   Clay Retaining Cap
• A clay cap that prevents the combustion gasses
  from escaping. It is destroyed by the ejection
  charge. It is located opposite the nozzle.