Fluid mechanics

How high do hot air balloons go?

How high do hot air balloons go?

A typical commercial hot air balloon ride usually flies at a height of between 150 and 800 meters above the surface, but a hot air balloon can reach up to 10,000 feet in altitude.

As we go up, in addition to finding less pressure, the temperatures drop. This drop is on the order of about 2 degrees Celsius for every 1,000 feet (about 300 meters). The proportion of oxygen in the air also decreases.

The limit for a balloon to rise is set by physics and the humans who crew it.

 From 4,500 or 5,000 meters it would be convenient for the crew members to carry an additional supply of oxygen. The burner flames would also go out due to a lack of oxygen. That is, they would also require an extra supply of O2. You would also need an ignition system for the pilot lights that would go out for the same reason. The crew members would also need special suits to withstand the low temperatures that at 11 or 12,000 meters would be around 50 or 60ºC below zero. From a certain height, a pressurized capsule or a space suit would also be necessary.

The maximum height was achieved by French pilot Rémi Ouvrard who reached a height of 4,016 m (13,175 ft) in a hot air balloon flight. It was the highest altitude reached standing on top of balloon. This record was set in Châtellerault, Vienne, France, on 10 November 2021.

What is a hot air balloon?

A hot air balloon is an aircraft that floats in the air without the aid of any mechanic engine because it is lighter than air. Balloons rise because warmer air rises in cooler air sinks.

Hot air balloons are means of air transport that are sustained in the air thanks to the difference in density between the air outside and inside the balloon. Balloons are a clear example of fluid mechanics since air is fluid, and Archimedes' law applies to them.

This method of flying is normally used to transport passengers on recreational trips or for advertising campaigns.

The composition of this aircraft consists of a large spherical envelope that holds the air, burners, and a wicker basket. On the bottom of the envelope, there is an opening called the mouth that is the entrance of air.  Beneath the envelope, there is the wicker basket with the burners, where the passengers and the pilot are located.

How does a hot air balloon work?

A hot air balloon stays in the air due to the difference in density between the air inside and the cold air outside. 

For a hot air balloon to fly, it is necessary to heat the air inside. To do this, modern hot air balloons use propane burners located inside the basket next to the pilot. When the pilot wants to gain altitude, he fires the burner to increase the air temperature, and the hot air balloon rises.

As the temperature of the interior increases, the air inside the balloon expands so that its density decreases. According to Archimedes' law, having a lower density than the outside air, cold outside air exerts an upward force that makes it rise.

The balloon has a parachute vent on the crown - the top of the envelope - collecting most of the heat from a more resistant material. The pilot can open the parachute vent by pulling down a cord out of a hole via pulleys. When the crown is open, the hot air escapes through the parachute vent making the balloon descend.

On the other hand, the balloon moves horizontally according to the air direction in which the wind blows. Therefore, to travel in a balloon, the pilot must find a current of air going in the desired direction by raising or lowering the balloon. Since the balloon is totally enveloped by the air, it travels at wind speed.

How many people can fly in a hot air balloon?

The number of people a hot air balloon can lift depends on the size and weight of the balloon. The largest balloons can carry more than 20 people, while the smallest balloons can only carry one or two people.

Drawings of hot air balloons

Below we show a selection of photos and drawings of balloons.

How high do hot air balloons go?How high do hot air balloons go?How high do hot air balloons go?How high do hot air balloons go?

Publication Date: November 16, 2022
Last Revision: February 14, 2023