Principles of Rocketry

Design and Drawing for Production Mr. Herrling

Outline:

• 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 reaction

What is the Action?

Solid Fuel Rockets • Fuel in solid form burns and is converted to hot gasses.

• 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 backwards

Gasses Action Rocket 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 fuel.

• 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 Engines • Solid Fuel Rocket Boosters

Propulsion

• 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 oxygen. • 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

Thrust

• 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

•

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

Drag

• 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.

Lift

• The

lift force

(the aerodynamic force perpendicular to the flight direction) is used to overcome the

weight

. • On a rocket,

thrust

to weight. is used in opposition • 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 behind.

•Heavy mass made of metal carriers the momentum.

•The End…