Although zero-emission air travel may sound like a thing of the future, gliders have a long history, which can be traced back to the birth of aeronautics. Before the Wright brothers famously outfitted their Flyer design with an engine-powered propeller, most early-flight concepts could be defined as gliders. Early gliders were often launched from hilltops or towed behind a motor vehicle to achieve liftoff. Once airborne, it was the pilot's job to find pockets of rising air known as "thermals" to stay in flight longer (more on that later). That basic principle still applies today, but as modern technology has brought stronger and lighter materials to market at lower costs, modern gliders and sailplanes can travel greater distances.

Modern methods of liftoff include being pulled along a runway by a heavy-duty motorized winch, or an aerotow that requires a traditional airplane to get the glider off the ground. Once in the air, it's just like the good ol' days. A trained pilot skillfully locates rising air, which is usually powerful enough to lift the glider to higher altitude, extending the distance of the flight. Of course, even technology can play a part in old school thermal locating methods.

In the past few years, pilots have gone social and put thermal maps on the web. Now it's easy for a pilot to pick a common thermal zone and fly to it. Even the in flight instruments that pilots can use have gained some technology in hopes of grabbing a "free" ride.

The free ride, so to speak, comes from naturally occurring columns of rising air. They are created from uneven heating of the Earth by the sun. Such uneven heating can be caused by cloud cover, terrain changes, and even shade from tall buildings and trees. As the ground heats, the air around it starts to get hot and thus less dense. It begins to rise until the temperature is at equilibrium with the rest of the air around it. (That can depend on how much the air was heated.)

As that air begins to rise, skilled glider pilots can locate the air and ride it upward. After climbing levels off--usually after circling in the thermals for a few minutes--common gliders can travel at a 45:1 glide ratio. This means for every foot lost vertically, the glider can travel 45 feet horizontally (1 mile of vertical height = 45 miles horizontal travel).

In our episode, we showed the glider being lifted via aerotow, but there are concepts in the works that will render the motorized plane unnecessary and therefore reducing any emissions for flight. By capturing solar energy on the plane's large wings, future gliders will be able to power a small propeller to get up into the air. From there, it will be business as usual. Imagine the ability to fly somewhere quickly without using a drop of gasoline. Or, bypassing LA traffic to get from the city to the beach in no time at all.

That may sound like a stretch, but remember, people weren't exactly optimistic about the Wright brothers' plane, and we know how that went. The rest is history.

Click the image below to watch TRANSLOGIC 73: Thermal Soaring:

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