hot air balloon above Luxor city
hot air balloon Everyone gets busy unpacking the large gasoline-powered fan, lifting the wicker basket from the pickup bed, and unrolling the hundreds of meters of nylon.
The pilot releases a small helium balloon and studies the air currents that whisk it away. With a noisy growl, the fan starts up.
The yellow and blue panels
lift off the ground and undulate. In the predawn light, the inflating balloon looks like some weirdly colored monster slowly rising out of the earth. Into a sky streaked with red and orange, the sun bursts over the distant mountains.
The propane burner blasts its noise and heat into the morning.
As the air inside the balloon warms, the balloon expands, and the nylon envelope is pulled from the ground.
The wicker creaks as we climb into the basket.
Within minutes, the balloon towers over us, tugging at the ropes that fetter it to the earth.
At the pilot’s signal, the ground crew loosens the ropes and the balloon pops into the air.
We wave to the crew, already occupied with packing up gear and loading it into the vehicles that will follow us.
Up and away As air inside the balloon heats up, the molecules move faster and faster.
If the balloon were sealed,
pressure would soon build to the bursting point.
But molecules are free to escape.
Before long, the hot air inside the balloon is less dense than the cool air that surrounds it.
Just as an object less dense than water rises to the surface, our balloon filled with hot air rises through the surrounding air.
And we are off! Gaston, our pilot, checks two gauges—the variometer measures the balloon’s rate of ascent or descent.
We’ve been climbing steadily for the past five minutes.
The altimeter indicates our distance from the ground.
We’re 350 meters above the ground—a nice cruising height—so Gas-ton shuts off the propane burner. It is amazingly quiet up here! Montgolfier (the French term for hot air balloons) are propelled by the wind.
But we are only aware of floating. In a balloon you neither feel nor hear the wind, since you are traveling with it.
That is why a ground crew is essential. You never quite know where you’re going to end up because the wind, not the pilot, determines the flight path
discover the gas laws Many of our gas laws were discovered by balloonists. The Montgolfier brothers came up with the idea of launching and testing hot air balloons after observing that smoke never flowed down a chimney.
Jacques Charles, a French physicist, knew that the newly identified hydrogen gas would lift balloons far better than hot air.
His first experiment, launched from Paris, was supremely successful! The unmanned balloon shot a mile into the sky and eventually landed 25 km away, terrifying the peasants, who hacked at the flying “monster” with pitchforks until it no longer “breathed”.
Charles’ law—the volume of a gas will increase as its temperature increases, when kept at a constant pressure—is named after its discoverer.
Professor Charles applied his discovery to making improvements to the airships. Early flights were brief because the balloons quickly deflated.
The buoyant gases escaped through the silk fabric’s weave.
Charles coated the silk with rubber dissolved in turpentine, sustaining flights by slowing the diffusion of hydrogen or hot air from the balloon. He suggested adding a vent to the top of the balloon.
The vent allows pilots to release gas from the apex, thus giving them control over the descent. Early balloons had an alarming tendency to explode.
Pilots, hoping to set new altitude records, heated the flammable hydrogen to decrease its density.
Not surprisingly, some met their deaths in spectacular, fiery crashes.
Sometimes the inexperienced balloonist failed to balance the amount of air inside the envelope with the rate at which it was heated.
The rapid ascent to high altitudes strained the silk beyond the tolerance limit.
The balloon burst, plunging the occupants to their untimely deaths.
Gas-ton fires the burner again, reheating the air to regain our lost altitude. It’s good to know that skirts of contemporary balloons are treated with a flame retardant.
The average sporting balloon stands about seven stories tall and, depending on its design, is made from about 1000 square .