Flight
Objective: Conduct tests of a model parachute design, and identify design
changes to improve the effectiveness of the design.
A parachute works to slow down someone, or something, from falling by creating
“drag.” Drag is the push on something from air or water. Because air is much thinner than
water, air doesn’t have as much drag as water. The bigger something is (that is, the larger its
surface area), the more drag it creates. That’s why a parachute works so well – it is very light
and it has a very big surface area. It catches lots of air, creating lots of drag, which slows it
down as it falls. The first real parachute was invented in the 1780’s. Parachutes have been used
to slow down the descent of people and things ever since. Huge parachutes are used to slow
down the fall of rockets and space shuttles when the re-enter Earth’s atmosphere.
Objective: Describe the design of a hot-air balloon and the principles by which
its rising and falling are controlled.
Hot air balloons are based on very a basic scientific principle: warmer air rises in cool air.
A hot-air balloon rises because it is filled with hot, less dense air and is surrounded by colder,
denser air. To make a hot air balloon rise and to keep it rising, the air inside of it must be
constantly heated. This is done with a burner positioned under an open balloon “envelope.” As
the air in the balloon in the balloon cools, the pilot can reheat it by firing the burner. A hot-air
balloon has three essential parts: the burner, which heats the air; the balloon envelope, which
holds the air; and the basket, which carries the passengers. The burners in modern hot-air
balloons heat the air by burning propane, which is stored in compressed liquid form in
lightweight cylinders positioned in the balloon basket.
To lift the balloon, the pilot moves a control that opens up the propane valve. As it
turns, the flow of gas increases and the flame grows in size. The pilot can increase speed by
blasting a larger flame to heat the air more rapidly. Hot-air balloons also have a flap at the top
of the envelope to let air out, controlled by a cord in the basket. This causes the balloon to
descend. If the pilot keeps the flap open long enough, the balloon will sink. Pilots can only move
hot-air balloons up and down. To move in a particular direction, a pilot ascends or descends to
the appropriate level and rides with the wind. Since wind speed generally increases as you go
higher in the atmosphere, pilots can control speed by changing altitude.
Objective: Conduct tests of glider designs; and modify a design so that a glider
will go farther, stay up longer, or fly in desired way; eg. fly in a loop, turn to the
right.
Objective: Recognize the importance of stability and control to aircraft flight;
and design, construct, and test control surfaces.
Objectives: Apply appropriate vocabulary in referring to control surfaces and
major components of an aircraft. This vocabulary should include: wing, fuselage,
vertical and horizontal stabilizers, elevators, ailerons, and rudder.
The pilot of an airplane needs to be able to control its flight. The plane needs to be able
to go up and down, and turn to the right and to the left. A pilot also needs to be able to achieve
enough thrust on the plane because the air flow over the wings must create enough lift to
overcome the force of gravity.
In order for a plane to lift off, the four forces of flight must be balanced. If lift is greater
than weight, the plane goes up. If lift and weight are equal, the aircraft continues level flight. If
weight is greater than lift, the plane goes down. The pilot must use the engines to move
forward to provide thrust. Once there is enough thrust the speed requirement will be met for
lift. The force acting opposite to thrust is drag, the resistance of air on the plane’s wings and
body. If thrust is greater than drag, the plane moves forward. If drag is greater than thrust, the
plane slows down.
The aircraft is made up of several different parts that enable a pilot to have a successful
flight. The main body of the plane is called the fuselage. Flaps are part of the airplane that can
be adjusted to increase the curvature of the wings to create more lift. Hinged flaps in the
trailing edge of an aircraft’s main wing are called ailerons. These are used to make the airplane
bank left or right, which is called “roll.” Ailerons control roll. If the left aileron is raised and the
right one is lowered, the air moving over the upper surface of the wing is slowed, thereby
increasing the air pressure. As a result, the plane banks to the left.
Two smaller flaps on the plane’s tail can be moved up or down. They are called
elevators. They are attached to the horizontal stabilizers. Elevators are used to control pitch.
Pitch is the upward or downward movement of the plane. With the elevators down, lift on the
tail is increased and the nose drops. With the elevators up, lift on the nose is increased; the tail
goes down and the nose rises. The flap attached to the tail of the wing on the vertical stabilizer
is called the rudder. The rudder allows the pilot to change direction from left to right. This is
called “yaw.” If the rudder is turned to the left, the nose of the plane turns left. If the rudder is
turned to the right, the nose of the plane turns right. Pilots use both the ailerons and the
rudder to turn the plane.
Objective: Construct and test propellers and other devices for propelling model
aircraft.
One of the problems with most aircraft is that they are quite large and cannot hover in
one place. They must be moving forward all the time in order to achieve lift. This is not the case
for helicopters. Helicopters are designed with a giant horizontal propeller, known as a rotor,
which spins around very quickly. Each of the long thin blades of the rotor is the shape of an
airfoil. These blades cut through the air at high speeds and provide the helicopter with lift. Lift
can be generated while the helicopter is going straight up, hovering, flying forward, or flying
backward. To move in these different directions, all the pilot has to do is tilt the rotor slightly in
the direction he or she wants to go. The four forces of flight still apply to the movement of a
helicopter.
Objective: Describe the differences in design between aircraft and spacecraft,
and identify reasons for the design differences.
Since there is no air in space, aircraft and spacecraft have many design differences. The
first difference is how they achieve lift. An aircraft achieves lift by first generating thrust, which
creates enough speed to achieve lift. Spacecraft generate thrust to lift-off through two large
rocket boosters and three main engines. The engines burn liquid oxygen and hydrogen. The fuel
for the engines is stored in a large tank attached to the shuttle. After lift-off, the fuel tank is
detached from the shuttle. With the help of a large parachute, it lands safely in the ocean
where it is picked up. Shuttles are designed to meet the environmental needs of the astronauts
on board. Astronauts need air to breathe, food to eat, water to drink, and a warm temperature.
When the shuttle is ready to come back to Earth, it must come through Earth’s atmosphere.
When the shuttle does this, it is moving so fast that large amounts of heat are generated from
the friction of air molecules. Spacecraft are designed to be protected from the intensity of the
heat. They have reinforced carbon on the wing surfaces and underside, high-temperature black
surface insulation tiles on the upper forward fuselage and around the windows, and lowtemperature white surface tiles on the remaining areas. These materials are designed to
protect the shuttle from the intensity of the heat during re-entry. When re-entry to the Earth’s
atmosphere is complete, the shuttle is able to fly like an airplane. Spacecraft are designed with
wings that can generate lift when needed.