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