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Rockets

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by

Tamara Rajecki

on 9 May 2016

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Transcript of Rockets

ROCKETS
A vehicle, typically cylindrical, containing
liquid or solid propellants
which produce hot gases or ions that are ejected rearward through a
nozzle
. This creates an
action force
accompanied by an
opposite and equal reaction
force, driving the vehicle forward. Rockets are
self-contained
, because they are able to operate in outer space.
Newtons' 3 Laws of Motion
1. Objects at rest will
remain at rest
and objects in motion will
remain in motion
in a straight line unless acted upon by an
unbalanced force
.
2. Force equals
mass times acceleration.
3. Every action has an
equal and opposite reaction.

1. Objects at Rest or in Motion
At Rest
: forces are balanced. The force of
gravity
on the rocket balances with that of the
launch pad
holding it up.

In Motion
:
Thrust
from the rocket unbalances the forces. As a result, the rocket travels
upward
(until it runs out of fuel).
2. F=mA
The pressure created inside the rocket produces force (thrust). Mass represents the
total mass
of the rocket, including its
fuel.

The mass of the rocket
changes
during flight. As fuel is rapidly
used and expelled
, the rocket weighs
less and accelerates.

Thrust continues
until
the engine stops firing.

3. Action and Reaction
A rocket
takes off only
when it expels gas.
Action
: the rocket pushes the gas out of the engine.
Reaction
: the gas pushes up on the rocket.

The Action (Thrust) has to be
greater than
the weight of the rocket for the Reaction (liftoff) to happen.
Inertia
Inertia is the resistance of an object to change its motion. It is associated with the mass of the object.
More
mass
= more
inertia
Center of Mass
Center of mass is the
exact point
, which all of the mass of an object is perfectly
balanced.
Center of Pressure
Center of pressure is the
location
where the '
pressure forces
' acting on a rocket are
balanced
.
The CP exists only when
air is flowing past
the moving rocket.
DRAG
DRAG =
Air resistance
Air resistance causes
friction
which
slows

down
the rocket.
Friction always works in the
opposite direction
of the rocket's motion.
Even when a rocket is
descending drag counteracts
the rocket's motion.
Reducing Drag
AERODYNAMICS
Pointed Nose Cone - causes the air to part







Thinner, streamlined fins moved toward the tail end of the rocket.
Stability
How can you increase rocket stability?
1.
Lengthen
the rocket
2. Add
mass
to the nose cone. This is called
ballast
.
3.
Extend the fins
toward the end of the rocket.
4.
Heavier
rockets have more
inertia
and therefore are more
stable
. (Don't add too much mass!)
BALLAST
Ballast is any mass added to a vehicle to improve stability and increase inertia.
Stability - ballast towards the nose cone will shift the center of mass forward.
Inertia - more ballast increases inertia and will prevent the rocket's path of motion from being prematurely overcome by drag.
Rocket Fin Shapes
Square/Trapezoidal = more stability and more drag
Triangular = less stability and less drag
TRAJECTORY
Trajectory is the
curved path
of an object traveling through space.
(Any object thrown or launched has trajectory.)
Boost Phase
inital period of thrust; ends when the fuel runs out.
Coast Phase
the period of flight when the rocket is not being actively powered; end of boost to ground impact
Apogee
highest point of trajectory
Multi-Stage Rockets
a rocket that uses
two or more
stages, each of which contains its own
engine or propellant
.
Advantages
By
dropping
each stage as it exhausts its fuel, it
lightens the rocket
. The
remaining
stages are able to provide
more acceleration
than the stage before.
Each stage can be built
specific
to the
conditions
of where the rocket is flying during that stage. (The
lower
stage can be built to withstand the
atmospheric pressure
.
Upper
stage can withstand the
vacuum
of space.)
Disadvantages
Makes the rocket
heavier
and more
difficult
to build.
There is the potential for
separation or ignition
failure, or stage
collision
.
Costly
to build.
First Stage (Stage 0) is associated with liftoff. 2nd and upper stages burn and fall off in order (called staging).
Full transcript