Principles of Rocketry

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					Principles of Rocketry

• Newton’s Third Law
• Solid Fuel Rockets
• Liquid Fuel Rockets
• Water bottle Rockets
• Forces on Rockets
• Rocket Stability
Isaac Newton’s 3rd law of Motion

 • For every action
   there is an equal
   and opposite
What is the Action?

Solid Fuel Rockets
• Fuel in solid form burns and is converted to hot
• Hot gasses expand and create high pressure.
• Pressure escapes out nozzle, pushing against
  air and rocket body equally.

   – Reaction: Rocket moves forward, as gasses move
Gasses   Rocket
Action   Reaction
More on Solid Fuel Rockets

• Solid-fueled rockets use
  a fuel and oxidizer in
  solid form. The fuel and
  oxidizer are in a powdery
  or rubbery mixture known
  as the grain or charge.
  Once a solid-fueled
  rocket is ignited, it burns
  completely. There is no
  way to stop the
  combustion or to change
  the amount of thrust.
Liquid Fuel Rockets

• Work on same basic principles as solid
• Carry liquid fuel and oxygen.
• Unlike solid fuel, liquid fuel can be
  regulated to control thrust.
… Liquid Fuel

• Used for launches and interplanetary travel,
  liquid fuel rockets are more versatile than
  solid rockets because the amount of thrust
  can be controlled, but they are less reliable
  than solid rocket engines.
Space Shuttle:

• Liquid Fuel and
  Oxygen tank feeding

• Solid Fuel Rocket

• All spacecraft need to reach about 17,500 miles
  per hour to get into orbit.
• Thrust is used to push the spacecraft this fast.
• Thrust is produced by burning a rocket fuel with
• If there is not enough thrust the spacecraft will
  fall back to earth due to gravity.
 Our Water Rockets

• Instead of hot gasses creating pressure, we
  use a bike pump and store pressure.
• Action: Expelling water from engine bottle
  (water is forced down)
• Reaction: Water resisting against rocket body
  (Rocket is forced up)
Water Rockets Work Like Real Rockets

• Forward motion or thrust
  can best be described by
  observing a balloon filled
  with air. When air is
  released from the
  balloon, forces inside the
  balloon cause it to move
  to the left.

• Weight is the force generated by the
  gravitational attraction on the rocket.
• We are more familiar with weight than with the
  other forces acting on a rocket, because each
  of us have our own weight which we can
  measure every morning on the bathroom scale.
• We know when one thing is heavy and when
  another thing is light

• We can think of drag as aerodynamic friction,
  and one of the sources of drag is the skin
  friction between the molecules of the air and
  the solid surface of the moving rocket.
• Because the skin friction is an interaction
  between a solid and a gas, the magnitude of
  the skin friction depends on properties of both
  solid and gas.

• The lift force (the aerodynamic force
  perpendicular to the flight direction) is
  used to overcome the weight.
• On a rocket, thrust is used in opposition
  to weight.
• On many rockets, lift is used to stabilize
  and control the direction of flight.
Stability During Flight

• The purpose of putting fins on a rocket is to
  provide stability during flight, that is, to allow the
  rocket to maintain its orientation and intended
  flight path.
• If a typical amateur rocket was launched
  without fins, it would soon begin to tumble after
  leaving the launcher, due to the way that
  aerodynamic and other forces (such as wind)
  act upon the rocket, in relation to the forces that
  are exerted upon the rocket by the motor and
  by gravity.
Stability During Flight…

• Think about a dart…
                        •Fins or feathers in the rear
                        act like wind veins and trail

                        •Heavy mass made of metal
                        carriers the momentum.
•The End…

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