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
Ballooning at the 1900 Summer Olympics Hot air balloons for manned flight were invented in 1783, but requiring fuel, they proved less practical than the hydrogen balloons that followed almost immediately. Hot air ballooning soon died out, and gas balloons dominated ballooning for nearly 200 years. Gas balloons used hydrogen or coal gas until switching to helium well into the 20th century. The height or altitude of a gas balloon is controlled with ballast weights that can be dropped if the balloon gets too low. In order to land some lifting gas must be vented through a valve. Gas balloons have greater lift for a given