ThePrinciple of Balloon Flight

 

     Hot air rises . The envelope ( the multicolored 
compartment) traps a largebubble of hot air. If the air in the envelope is allowed to cool or ifthe hot air is "vented"(allowed to escape ) from the top or side of theenvelope  (allowed to escape ) from the top or side of the envelopethe the balloon will descend. An altimeter ( to measure altitude), a rateof climb meter , and an envelope temperature gauge are the only instrumentsused in the balloon . Amazingly, the pilot can control the altitude ofthe balloon within a matter of inches.
 
Balloons can go as fast as the wind blows . But if the wind is over 8 miles per hour at groundlevel ,balloons are normally not inflated because of the increased possibilityof burning the fabric and because the landing would be rough and requirea large field.