Ed Yost own interests turned toward reviving the lost practice of manned hot-air ballooning. This technology had first been invented in France by in the late 18th century by pioneers led by the Montgolfier brothers, but under the Montgolfier system, the balloon's air was heated by a ground fire prior to the balloon being released. The inherent danger of this type of balloon flight led to the system being abandoned when hydrogen and later helium became available. One of Yost's key engineering insights was that a hot-air balloon could be made to carry its own fuel. The invention of relatively light burners
Hot air balloon indicators would be useless) and direction. The combined mass of an average system can be calculated as follows: using a density of 0.9486 kg/m³ for dry air heated to 210 °F (99 °C). Increasing the air temperature inside the envelope makes it less dense than the surrounding (ambient) air. The balloon floats because of the buoyant force exerted on it. This force is the same force that acts on objects when they are in water and is described by Archimedes' principle. The amount of lift (or buoyancy) provided by a hot air balloon depends primarily upon the difference between the