Combining both methods of a ship and a hot air balloon, we investigate how an airship flies.
Airships use a combination of different gases in order to get off the ground, fly and descend. Today mostly helium gas is used to fly the lighter-than-air (LTA) craft, which although more expensive than hydrogen, was adopted as the non-flammable alternative after the infamous Hindenburg accident.
The helium-filled ship holds several “tanks’ of air known as ballonets. Because air is heavier than helium, all the pilot needs to do is open the air valves to release it and create positive buoyancy so the airship elevates. Once in the open skies the pilot controls the airship in flight much like a submarine under water, using a rudder to steer, adjusting the elevators to ascend and descend and throttling the engine (which provides forward and reverse thrust) to angle it into the wind.
At higher altitudes the air pressure outside the LTA decreases and so the helium in the envelope expands, to maintain pressure the pilot pumps air into the ballonets. This technique is also employed to descend, as filling the ship with more ‘heavy’ air makes it negatively buoyant and therefore sinks lower in the sky, or bring it in to land.
While the first hot air balloon was invented in 1783 by two French brothers – Jacques-Etienne and Joseph-Michel Montgolfier-the first powered airship was not constructed until many decades later in 1852. Henri Giffard built the first, which consisted of a 143-foot cigar-shaped gas bag with a propeller. It was powered by a three-horsepower steam engine. Just under half a century later in 1900 Count Ferdinand von Zeppelin of Germany invented the first rigid airship and therefore his name and work lives on.
Airships can stay elevated from a matter of hours to a stretch of several days, making them ideal for research or for watching sports events and so on. In recent times scientists have been adopting the method of transport to study whales, thanks to their less disturbing nature than helicopters, boats and planes.
The German Hindenburg airship took off from Frankfurt in May 1937, taking just two and half days to reach New Jersey. The ship measured over 800 feet in length and weighed 242 tons. Accommodating a rigid design, it was filled with hydrogen – a much cheaper gas than the helium used today. On arrival it hovered tentatively over its landing area as 200 ground crew attempted to retrieve it with its landing lines. A small burst of flames was spotted on the upper fin and in just 34 seconds – reacting with the highly combustible gas – the ship was transformed into a huge fire ball. Some of the people on board jumped to safety and landed on the sand below, but 13 passengers, 22 crew and one ground man were killed in the accident.