A hot air balloon is a flying vessel that is lighter than air, consisting of an upper part shaped like a large balloon and a basket suspended beneath it.
The balloon's interior is heated, making it less dense compared to the cooler external air, generating lift for movement. The basket carries passengers and a heat source, often an open flame. Modern hot air balloons are typically made of nylon fabric with fire-resistant material at the opening.
They find use in aeronautical sports, photography, tourism, and more. The first manned hot air balloon was created by the Montgolfier brothers. The first hot air balloon flight in America took place on January 9, 1793, launched from Philadelphia by French aeronaut Jean Pierre Blanchard. There are four main types: AA, AX, AM, and AS.
If you truly need to get somewhere specific, a hot air balloon wouldn't be the most practical means. In reality, you can't truly steer a hot air balloon as its speed is determined by the wind. However, if you merely want to experience flight, a hot air balloon offers a uniquely serene experience. Many consider riding in a hot air balloon as one of the most peaceful and delightful activities they've ever experienced.
Hot air balloons are also a creative application of basic scientific principles. Understanding why they ascend and how to designed to allow pilots to control altitude and vertical speed is fascinating. Witnessing these beautifully shaped, simple structured early aircraft can be quite astonishing!
At its core, a hot air balloon operates on a fundamental scientific principle: hot air rises above cold air. Essentially, hot air is lighter than cold air, as a given volume of hot air has less mass. One cubic meter of air weighs approximately 1 gram, and when heated to 37.8 degrees Celsius, the weight of the same volume of air decreases by about 0.25 grams.
Thus, for every cubic meter of air in a hot air balloon, it can lift about 0.25 grams. However, this is far from sufficient. That's why hot air balloons appear so enormous - to lift a 454-kilogram object, you'd need approximately 1,840 cubic meters of hot air!
To maintain the ascent, continuous heating of the air inside the balloon is necessary. Hot air balloons achieve this through a burner located beneath the opening of the envelope. When the air in the balloon cools, the pilot can reignite the burner to reheat the air.
A hot air balloon primarily consists of three parts: the passenger-carrying basket, the envelope for containing air, and the burner for heating the air.
Modern hot air balloons use propane for heating the air. Propane, a commonly used outdoor grilling fuel, is stored in lightweight cylinders within the balloon basket. An intake tube is connected to the bottom of the cylinder to draw out the liquid propane.
Propane is highly compressed in the cylinder, allowing it to flow rapidly through the intake tube to the heating coils. The heating coils, essentially a system of steel tubing coiled around the burner, facilitate this process. When the pilot ignites the burner, liquid propane flows out and ignites with a small, constant flame.
As the flame burns, the metal surrounding the coil heats up, warming the propane flowing through it, and causing the propane to transition from liquid to gas before ignition. Gaseous propane generates a stronger flame and allows for more efficient fuel combustion.
Most modern balloon envelopes are made of long strips of nylon fabric reinforced with stitching. Triangular fabric strips extending from the bottom to the top compose the majority of the envelope. Nylon is an ideal material for hot air balloons due to its lightweight, strength, and high melting point. The bottom of the envelope is coated with a special fire-resistant material to prevent ignition from the flame.
Even the most experienced pilots cannot entirely control the flight path of a hot air balloon. Typically, wind conditions allow for very limited choices for the pilot. Hence, it's challenging to navigate a hot air balloon along a precise route or return to the starting point. Unlike piloting an airplane, flying a hot air balloon heavily relies on improvisation, with conditions changing constantly.
Consequently, some members of the hot air balloon crew must remain on the ground, tracking the balloon by vehicle to predict where it will land. These crew members then proceed to the landing site to pick up passengers and equipment.
Hot air balloons can take us several hundred meters or even kilometers high, providing a three-dimensional view of the world. At that moment, when you're floating entirely in the air without controlling the burner, there's only tranquility around you. The speed of the wind becomes your pace, and its direction determines your path. There's a disconnected quietness, almost as if you've completely melded into the wind.
