It was all those years ago on the 21st of November in the year 1783 in Paris, that the first hot air balloon, that was untethered and manned hit our skies. This historical flight was made by Jean-François Pilâtre de Rozier and François Laurent d’Arlandes. The balloon was actually created on December 14 1782 by by the Montgolfier brothers.
A model of the Montgolfier brothers’ balloon at the London Science Museum
image via Wikipedia (Click for larger view)
The heated air inside the envelope (the balloon) makes it buoyant since it has a lower density than the relatively cold air outside the envelope. Unlike gas balloons, the envelope does not have to be sealed at the bottom since the air near the bottom of the envelope is at the same pressure as the surrounding air.
In today’s sport balloons the envelope is generally made from nylon fabric and the mouth of the balloon (closest to the burner flame) is made from fire resistant material such as Nomex. Beginning in the mid-1970s, balloon envelopes have been made in all kinds of shapes, such as hot dogs, rocket ships, and the shapes of commercial products, though the traditional shape remains popular.
References :- Wikipedia