By Jonny Lupsha, Wondrium Staff Writer
A hydrogen balloon trapped a man for two days after its ropes untied. The unwitting passenger had been picking pine nuts when the balloon became untethered. Balloons were the first flying vehicles.
A man in China became an unhappy hot air balloon pilot when a journey picking pine nuts from a pine tree went awry. His balloon somehow became untethered from the ground and carried him into the air, drifting 200 miles over the course of two days, before finally returning to Earth. Officials say the man was eventually able to call emergency services from his cell phone, sometime after the runaway balloon took off. Rescuers gave hime instructions for how to safely deflate the balloon so he could land.
Buoyancy is the key to balloon flight, which was first attempted in 1783. In his video series The Science of Flight, Dr. James W. Gregory, Professor of Mechanical and Aerospace Engineering at The Ohio State University, clarifies the science of ballooning.
Full of Hot Air
“[Buoyancy] is the fundamental physical principle behind balloon flight,” Dr. Gregory said. “Whether flight is in a hot air balloon, or a helium balloon, or a hydrogen-filled zeppelin, the fundamental principle is the same: The lifting force action on the balloon is produced by buoyancy. This is the same buoyancy that we experience when we float in a pool, and it’s the same buoyancy force that makes all ships float on water.”
Finding buoyancy force dates back to Archimedes’ find of displacement in a bathtub. According to Dr. Gregory, to find buoyancy force, one could fill the bathtub to the brim, gently ease into it, and collect all the water that spills out. The amount of displaced water is equal to the buoyancy force. The same principle applies to gases, since both gases and liquids are fluids.
“For a balloon, the force of buoyancy pushing up on the balloon is equal to the weight of the air displaced by the balloon,” he said. “Now, the actual net lift that pushes the balloon upward will be the difference between the buoyancy force and the weight of the balloon itself. Of course, the full weight of the balloon would include the payload, the material of the balloon envelope, and the weight of the gas inside the balloon.”
Errors in Flight
Long before the Disney/Pixar release of the film Up, humanity wondered if regular balloons, when tied to an object like a chair with a single occupant, could lift the passenger into flight. How many balloons would it take? Could they safely return? In 1982, a Californian named Larry Walters, whose poor vision kept him from his lifelong dream of becoming a pilot, put the theory to the test.
“He tied 45, eight-foot weather balloons to his lawn chair [and] sat down with only a parachute, a pellet gun to burst individual balloons as needed, and a CB radio,” Dr. Gregory said. “After cutting a tether, he quickly rose to an altitude of over 15,000 feet. He ended up drifting into the hectic Los Angeles airspace, causing substantial disruption to air traffic in the area.”
After 45 minutes in the air, Walters shot several balloons to drift back down to Earth. The remaining balloons became entangled in power lines, causing a blackout and forcing him to climb down. He was arrested for flying into controlled airspace without being in two-way communication with air traffic control.
Hydrogen, twice as light as helium, may seem like an intriguing substitute for balloon flight. However, it was the choice of hydrogen gas that contributed to the Hindenburg crash. Helium would have been able to carry an empty Hindenburg, but hydrogen lifted a crew of 40 and a passenger manifest of 50 across the Atlantic Ocean at over 75 miles an hour. In 1937, tragedy struck.
“As the vehicle was positioning to land at Naval Air Station in Lakehurst, New Jersey, something caused the giant airship to ignite,” Dr. Gregory said. “Fire quickly spread throughout the Hindenburg’s hull, fed by the highly flammable nature of hydrogen gas. Although hydrogen in smaller commercial airships had flown without incident, commercial use of hydrogen for buoyancy faded away within a few years.”
The Science of Flight is now available to stream on Wondrium.