Hot air balloon sea level, and humidity of the air surrounding. On a warm day, a balloon cannot lift as much as on a cool day, because the temperature required for launch will exceed the maximum sustainable for nylon envelope fabric. Also, in the lower atmosphere, the lift provided by a hot air balloon decreases about 3% for each 1,000 meters (1% per 1,000 ft) of altitude gained. Standard hot air balloons are known as Montgolfier balloons and rely solely on the buoyancy of hot air provided by the burner and contained by the envelope. This style of balloon was developed by the
Balloon of motion, the balloon is propelled forward. This is the same way that a rocket works. Balloons filled with hot air or a buoyant gas have been used as flying machines since the 18th century. The earliest flights were made with hot air balloons using air heated with a flame, or hydrogen as the lifting gas. Later, coal gas and later still helium were used. An unpowered balloon travels with the wind. A balloon which has an engine to propel it is called a dirigible balloon or airship. Angioplasty is a surgical procedure in which very small balloons are inserted