Saturday Morning Physics

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Higher, Faster, Longer The Physics and
Engineering of Model Rockets, Model Airplanes and
Flying Toys
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Overview

• Early examples of flying models in the
  development of aviation and space flight
• Exploring the physics that makes flying models so
  interesting and so much fun
• Examples and demonstrations from rocketry and
  model aviation
• Flying models as tools for exploring and teaching
  physics
• The application of model engineering techniques
  and materials to the development of undergraduate
  laboratory experiments

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1796 Cayley Helicopter Model

• "...it may be an amusement to some of your
  readers to see a machine rise in the air by
  mechanical means and which anyone can construct
  at the expense on 10 minutes labour. There are
  two corks, into each of which are inserted four
  wing feathers, from any bird, so as to be
  slightly inclined like the sails of a windmill,
  but in opposite directions in each set.  A round
  shaft, which ends in a sharp point, is fixed in
  the top cork. At the upper part of the bottom
  cork is fixed a whalebone bow, having a small
  pivot hole in its centre, to receive the point of
  the shaft. The bow is then to be strung equally
  on each side to the upper portion of the shaft,
  and the little machine is completed. Wind up the
  string by turning.

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Cayleys 1804 Glider
A modern glider, with a forward wing, a rear
stabilizer and fin 99 years before the Wright
brothers! It was very pretty to see it sail down
a steep hill, and it gave the idea that a larger
instrument would be a better and a safer
conveyance down the Alps than even the surefooted
mule
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Alphonse Pénauds 1871 Planiphore
Planiphore designed by Alphonse Pénaud in 1871.
It is extraordinary that such a seemingly modern
design existed and was demonstrated publicly over
thirty years prior to the first successful
flights by the Wright brothers. Of particular
note is its use of twisted rubber strands to
store the energy necessary for propulsion, a
major technical innovation.
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Alphonse Pénauds 1872 HelicopterA Flying Toy
That Changed History
In 1874 Bishop Milton Wright brought a
Pénaud-type helicopter model home to his boys
Orville and Wilbur.
I often wonder what the first Wright flyer would
have looked like if Bishop Wright had brought his
boys a Pénaud Planiphore instead
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Pénauds Ornithopter
It is a testament to Pénauds brilliance that he
also perfected a flying model ornithopter. Long
before 1900 he had invented all the forms of
aircraft models flown today. We can only
speculate what the world lost with his suicide in
1880.
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Rocket Science Newtons Second Law
A Force Acting on an Object Causes its Momentum
to Change With Time
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Rocket Science Thrust
y
Demo Water Rocket
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Early Reaction Propulsion for Models Jetex
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Early Reaction Propulsion for Models Jetex
Display Jetex Model, Engine and Fuel
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Early Reaction Propulsion for Models Jetex
Jetex engines were the first reloadable engine
system. They were inexpensive and safe. Their
specific impulse (total impulse/weight) was so
low that free vertical ballistic flight was not
possible. Also they suffered from very poor
reliability. Something better was needed
Demo CO2 Rocket
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The Early Space Age

• During the 1950s the quest for rocket
  propulsion and space flight had captured the
  popular imagination in the same way that early
  aviation had captivated previous generations.
  With this came a gruesome unforeseen consequence
  young people were being maimed and killed as
  they sought to experiment with rocket propulsion.
  A shoe salesman from Iowa was moved to solve the
  problem

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Orville Carlisles 1954 Rock-a-Chute
Orville Carlisle wasnt just a shoe salesman-he
was a master pyrotechnician (his hobby). He knew
only too well how dangerous it was to handle
potentially explosive rocket propellants without
proper training and equipment. Using his
extensive knowledge of pyrotechnics, he developed
a model rocket engine that would be safe for
young people to use for legitimate experiments in
rocket propulsion. In collaboration with his
brother (a model airplane hobbyist) he developed
a lightweight wood and paper rocket to launch
with his new engine and Model Rocketry was born.
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Orville Carlisles 1954 Rock-a-Chute
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Model Rocket Flight A Safe Way to Experiment
with Reaction Propulsion
Carlisles design was innovative in a number of
ways. Safety was assured by means of remote
electrical ignition at a safe distance and
lightweight model construction. The paper
casings used for the engines would simply rupture
if the engine malfunctioned, posing no hazard to
people or property.
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Model Rocket Flight A Wide Arrayof Possible
Flight Profiles
The most important innovation of Carlisles
design was his inclusion of an ejection charge
as the final function of the engine. This
seemingly simple feature opened up countless
possibilities for recovery options, because it
permitted the configuration of the vehicle to be
changed in flight, transforming the model from a
ballistic projectile into a high-performance
duration machine.
Display Models and Recovery Systems
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Estes Industries Making Safe Reaction
Propulsion Available to All
Orville Carlisle and G. Harry Stine founded Model
Missiles Incorporated (MMI) in 1957, but their
venture failed commercially. Vernon Estes
succeeded in building Mabel the first
successful (albeit temperamental) automated
engine manufacturing machine. Estes industries
became the first firm to market model rocket
products on a large scale.
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Rocket Science Engine Construction
Paper Casing
Clay Nozzle
Ejection Charge
Propellant Grain
Delay Grain
Model Rockets are safe because the hobbyist
purchases the pyrotechnics pre-loaded by
professionals. To date tens of millions of model
rockets have flown safely.
Display Rocket Engines
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Rocket Science The Engine Code
Example C6-3
3 Second Delay
5.0 N-SltTotal Impulselt10 N-S
Average Thrust 6 N
Burn Time Total Impulse/Average Thrust
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Rocket Science Impulse and Momentum
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Rocket Science Impulse and Momentum
Impulse is the area under the thrust versus time
curve
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Rocket Science Impulse and Momentum
Force (N)
Area Under Curve Impulse In Newton-Seconds
(N-s)
Time (s)
Demo Static Test Stand
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Rocket Science B.O.E. Altitude Prediction
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Rocket Science The AerodynamicDrag Force
Dimensionless Coefficient of Drag
Air Density
Speed
Cross-Section Area of Vehicle
Kinetic Energy/Volume
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Rocket Science Stability
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Rocket Science Stability
Simple empirical techniques could be employed to
determine the center of gravity and center
of pressure without computation
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Rocket Science Stability
In the mid 1960s Jim Barrowman published his
landmark treatise detailing the calculation of
the center of pressure by the superposition of
individual CP calculations for the component
vehicle shapes. Today these equations are still
used to calculate the CP for numerical
simulations. The analysis is performed in
software and used as input to the numerical
routines.
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Rocket Science Numerical Simulations
2002 WSMC Model Test Flight With Streamer
Payload
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Rocket Science Numerical Simulations
Max. Acceleration 18.6 g Max. Speed 210
mi/hr Altitude 997 ft Total Impulse 5 N-s
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Rocket Science Numerical Simulations
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End of Part I