Four Forces of Flight. Rocket Project Day 1. Aerodynamic Forces. Act on a rocket as it flies through the air Lift & Drag Lift Force – Acts perpendicular to the direction of motion Drag Force – Opposes the direction of motion
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Four Forces of Flight Rocket Project Day 1
Aerodynamic Forces • Act on a rocket as it flies through the air • Lift & Drag • Lift Force – Acts perpendicular to the direction of motion • Drag Force – Opposes the direction of motion • Generated by the interaction and contact of a solid body with a fluid, a liquid or gas
Lift • In a rocket, lift is used to stabilize and control the direction of flight • In a plane, lift is used to overcome the force of weight; in a rocket, thrust is used to overcome weight • In a rocket, lift is generated by the nose cone, the rocket body and the fins
Drag • Think of drag as aerodynamic FRICTION • Sources of Drag • Skin Friction – Friction between air and the solid surface of the rocket • Form Drag – Depends on the shape of the rocket, a resistance to upward motion
Weight • The force generated by the gravitational attraction of one object on another object • This force is always directed towards the center of the Earth • The magnitude of this force depends on the mass of all of the parts of the rocket itself, plus the amount of fuel, plus any payload on board • The weight is distributed throughout the rocket, but we can often think of it as collected and acting through a single point called the CENTER OF GRAVITY
Center of Gravity • Average location of the weight of an object • Mass and weight are distributed throughout an object • How can we find the center of Gravity? • For simple geometries we just balance the component or the entire rocket using a string or an edge. The point at which the component or rocket is balanced is the center of gravity. This is just like balancing a pencil on your finger! Obviously, we could not use this procedure for a large rocket like the Space Shuttle, but it works quite well for a model.
Weight Formula • Weight = mass x gravitational acceleration • On Earth • W = m x 9.8 m/s2
Rocket Thrust • The force which moves the rocket through the air, and through space. • Thrust is generated by the propulsion system of the rocket through the application of Newton's third law of motion • The direction of the thrust is normally along the longitudinal axis of the rocket through the rocket center of gravity
Bottle Rocket Thrust • All rocket engines produce thrust by accelerating a working fluid • A bottle rocket uses water as the working fluid and pressurized air to accelerate the working fluid
Thrust (Continued) • In rockets, the hot gases in the combustion chamber press against all sides equally. Water bottle rockets work the same way. The water bottle acts as the combustion chamber of the rocket. • When the bottle is opened, the pressure on the opposite side of the combustion chamber is now unbalanced and pushes the rocket.