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Hot Air Balloon
Hot air balloons were the primary mode of transport that allowed people to travel by air; it was designed and developed in Paris in 1783. With a fabric ‘envelope’ to hold the hot air with an exhaust at the top and a carrier underneath the passengers, their design has never changed in centuries.
The floating hot air balloon is due to the air that heats inside the envelope, which has a lower density than the colder air outside. It’s precisely the same way as a boat supported by water on the ocean; the cold air supports a hot air balloon.
It requires specialised knowledge and expertise to operate a hot air balloon. Good familiarity with wind directions at different altitudes is a major requirement to operate a hot air balloon since it is the only technique to control the balloon. A pilot can change the vertical direction by regulating the amount of hot air within the balloon.
- Physics behind Floating of Hot Air Balloon
- Hot Air Balloon Operation
- Application of Buoyancy, Air Pressure and Gravity in Hot Air Balloon
- Frequently Asked Questions – FAQs
Physics behind Floating of Hot Air Balloon
The fundamental physics behind a hot air balloon is buoyancy, which generates lift. A hot air balloon consists of a large envelope bag with a basket suspended below. The basket holds a flame used to heat the air inside the balloon through an opening. Therefore, a lift is generated by the heat produced.
This phenomenon of lifting the balloon from the ground is due to the buoyant force created by the surrounding air since the density of hot air inside the balloon is less than the surrounding air.
It is Archimedes’ principle that works behind the lift of the hot air balloon, that is, an upward or buoyant force is acted upon a body upwards when it is wholly or partially submerged in a fluid at rest, and that the magnitude of this force is equivalent to the weight of the fluid displaced by the body. The hot air balloon works using the same principle: the air is a high-pressure fluid.
Therefore, this buoyant force must surpass the weight of the heated air, counting the weight of the balloon, passengers, and the on-board equipment for a lift to be generated,
Hot Air Balloon Operation
As revealed in the figure below, the weight of the hot air balloon is more focused near the bottom of the balloon, so the centre of mass G of the hot air balloon is always underneath the centre of buoyancy C. This means that the balloon is always steady during flight.
If the balloon machinist wishes to lower the balloon, he can either halt firing the burner, which cools down the envelope or open a small vent at the top of the balloon. This will decrease the buoyant force by releasing some of the hot air, which will eventually cause the balloon to go downhill.
Since keeping a strictly constant altitude by maintaining a net-zero buoyant force is practically impossible, the operator fires and turns off the burner irregularly until he reaches the desired height. This is the only way he can uphold an approximately constant altitude.
The operator must be familiar with the wind directions, which differs with altitude, to move the balloon sideways. So, he advances or drops the hot air balloon to the altitude matching the wind direction, and hence he can move the balloon in the direction he wants.
Watch the video and learn about the concept of Archimedes Principle
Application of Buoyancy, Air Pressure and Gravity in Hot Air Balloon
The downward force of Gravity draws all air particles into the atmosphere. But an upward force working opposite to Gravity is created by the pressure in the air.
This pressure level is maximum at the Earth’s surface; more weight above means a greater gravitational force downwards. As you move up through stages of the atmosphere, the air has a lesser amount of air mass above it, and so the balancing pressure declines. This is why pressure drops as you rise in altitude.
This pressure difference causes an upward buoyant force in the air. But this buoyant force is weak, and hence, for buoyancy to push something up in the air, the thing has to be lighter than an equal volume of the air around it.
So, if we change the air conditions inside the balloon, we can decrease density while keeping air pressure the same.
Hence, the overall pressure can be increased in two ways:
- Growth in the number of air particles so that there is a superior number of particle impressions over a given surface area.
- Increase the speed of the particles so that each particle strikes with greater force and the particles hit an area more often.
So, for this, you simply need to increase the speed of the air particles, and this can be done by heating the air. The air particles will become more excited by absorbing the heat energy. This, in turn, will make them move faster, which means they will collide with a surface with a greater force more often.
That is why a hot air balloon rises because it is filled with hot, less dense air and is encircled by colder, more dense air.
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$130,000 could buy you a Michelin-star meal with a view of the stars
Zephalto hopes to offer passengers panoramic views of Earth, a fancy dinner. and psychological counseling.
By Andrew Paul | Published May 12, 2023 4:00 PM EDT
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This year marks the 250th anniversary of the first human hopping aboard a hot air balloon. But Jean-Francois Pilatre de Rozier only hovered about 85 feet above the ground, so it’s safe to say he would be stunned at what his country’s modern denizens are planning. As CNN reported on Thursday, a French company called Zephalto aims to begin “edge of space” hot air balloon tourist sojourns as early as next year—for $130,000 a seat.
After ponying up the hefty price tag, passengers will board Zephalto’s pressurized capsule, Celeste, which is attached to a massive, helium-filled stratospheric balloon. Over the course of roughly ninety minutes, the balloon will ascend at 4 meters per second to an altitude of 25 kilometers (about 15.5 miles). Once at the edge of space, tourists will enjoy a fancy meal during their three-hour hover time in front of 7-square-meter window views of the Earth’s curvature before descending back down to terra firma.
Other high-profile space tourism ventures such as Blue Origin and Virgin Galactic travel much higher than the capabilities of even a high-end hot air balloon such as Zephalto’s. In July 2021, Virgin Galactic’s founder, Richard Branson, soared 86 km above Earth. Just one week later, Blue Origin took its co-founder and Amazon CEO Jeff Bezos above the Karman Line, the internationally recognized (if somewhat disputed) boundary for outer space.
Unlike those high-profile space tourism ventures, however, Zephalto bills itself as being a much more eco-friendly alternative. According to its official description page, only 26.6 kg of CO2 are purportedly needed for a single journey—the lowest amount required for a space flight, says the company, or akin to “as little as the production of a pair of denim trousers.” By comparison, a single suborbital rocket launch can put out as much as 300 tons of CO2 into the upper atmosphere during its journey.
As reservations quickly fill for the trips—Zephalto told CNN it’s already booked out until mid-2025. The company’s founder recently explained they were working closely with France’s space agency, CNES, alongside partners at Airbus to ensure all safety and logistical regulations are met. Once in full swing, Zephalto aims to launch as many as 60 flights per year, each with six passengers alongside two pilots.
And if the six-hour-total journey and fancy meal aren’t enough to sell you on a $130,000 ticket, Zephalto says it’s throwing in complementary psychological counseling ahead of the outing to help deal with what’s known as the “overview effect,” the existential weight that reportedly comes from viewing the entirety of Earth from high above its surface.
Andrew Paul is Popular Science’s staff writer covering tech news. Previously, he was a regular contributor to The A.V. Club and Input, and has had recent work also featured by Rolling Stone, Fangoria, GQ, Slate, NBC, as well as McSweeney’s Internet Tendency. He lives outside Indianapolis.
