Balloons
Have you ever wondered what keeps a hot air balloon
flying? The same principle that keeps food frozen in
the open chest freezers at the grocery store allows
hot air balloons to fly. It’s a very basic principle: Hot air
rises and cold air falls. So while the super-cooled air
in the grocery store freezer settles down around the
food, the hot air in a hot air balloon pushes up, keeping the balloon floating above the ground. In order to
understand more about how this principle works in
hot air balloons, it helps to know more about hot air
balloons themselves.
A hot air balloon has three major parts: the basket, the
burner, and the envelope. The basket is where passengers ride. The basket is usually made of wicker. This
ensures that it will be comfortable and add little extra
weight. The burner is positioned above the passenger’s heads and produces a huge flame to heat the air
inside the envelope. The envelope is the colorful fabric
balloon that holds the hot air. When the air inside the
envelope is heated, the balloon rises.
The pilot can control the up-and-down movements of
the hot air balloon by regulating the heat in the envelope. To ascend, the pilot heats the air in the envelope.
When the pilot is ready to land, the air in the balloon is
allowed to cool and the balloon becomes heavier than
air. This makes the balloon descend.
Before the balloon is launched, the pilot knows which
way the wind is blowing. This means that she has a
general idea........................... which way the balloon will
go. But, sometimes the pilot can actually control the
direction that the balloon flies while.......................................... flight.
This is because the air above the ground is sectioned .........................................layers in which the direction of the wind
may be different. So even though the pilot can’t steer
the balloon, she can fly or higher or lower into a different layer ......................................air. Some days the difference
between the direction of the wind between layers is
negligible. But other days the difference is so strong
that it can actually push the balloon in a completely
different direction!