A tribute to the Montgolfier Brothers and the dream of flight
Hot air is less dense than cool air. A cubic meter of air at 100°C (212°F) weighs about 250 grams less than a cubic meter at 20°C (68°F). Fill an envelope with enough hot air, and the difference in weight exceeds the weight of the balloon itself. You rise. It's that simple. And that miraculous.
A modern hot air balloon has three main components: the envelope (the colorful fabric bag, typically nylon), the basket (traditionally wicker - strong, light, flexible), and the burner (propane-fired, producing a flame of up to 3.5 million BTU). The envelope has panels called gores, with an opening at the top called the parachute vent for controlled descent. Some have turning vents for rotation. The whole assembly can weigh 250 pounds empty and carry 1,000 pounds of passengers and fuel.
Typical envelope volume: 77,000 cubic feet (2,180 m³)
Envelope temperature: 200-250°F (93-121°C)
Lift capacity: ~20 grams per cubic foot of difference
Typical flight altitude: 500-2,000 feet AGL
Maximum altitude (record): 69,850 feet (Vijaypat Singhania, 2005)
Flight duration: 1-2 hours typical
Landing speed: 0-10 mph
Best flying time: Early morning or late evening (stable air)
Hot air: Easy to produce, safe, low lift. Must keep heating.
Hydrogen (Hâ‚‚): Greatest lift, but highly flammable. Used for early gas balloons.
Helium (He): Good lift, non-flammable, but expensive. Used in modern blimps.
The Montgolfiers used hot air. Jacques Charles pioneered hydrogen. Modern sport ballooning returns to the brothers' method—propane burners heat air safely and controllably.
A balloon pilot cannot steer horizontally—only up and down. Navigation depends on finding winds blowing in the desired direction at different altitudes. Ascend to catch one current, descend to catch another. It's a three-dimensional chess game with the atmosphere.
Landing requires reading the terrain, gauging the wind, and timing the descent. A skilled pilot can set down gently in a chosen field. Others may drag across the landscape in an "adventurous" landing. Either way, it's traditional to toast with champagne afterward.