![]() ![]() No need for runways – Infrastructure independenceĪnother advantage of aerostatic flight is that it eliminates the need for runways in order to land. Because of the speed’s effect on drag, an airship travelling at half the velocity can go approximately twice as far on the same amount of fuel.Ĭonsequence 1.2. Being able to fly relatively slowly also gives an airship range flexibility. Being able to land at their leisure also means that airship can wait out the fog or other bad weather, and stand in a queue before landing at a busy station. Engines are required only for maneuvering or forward motion.īeing able to hover opens up unique applications from tourism to operating like cranes to acting as flying warehouses. Airships can turn off the engines and hover indefinitely. A helicopter can hover in one place but it has to burn a lot of fuel to do it. Essentially, the propellers are rotating wings. Helicopters fly by passing air over their propellers to create a pressure differential equal to their weight. Airplanes cannot stop, and if they slow down below some minimum velocity, they start to descend. Over half the fuel consumed by airplanes and helicopters is used just to remain airborne.Īirplanes need to have air moving over their wings to remain aloft. They require no expenditure of energy or effort, in contrast with the aerodynamic flight of airplanes and helicopters. The ability of airships to float in the air is called aerostatic flight. Aerostatic flight – Lower energy consumption In fact, the largest Zeppelins were about 250 meters long and 38 meters in diameter.Ĭonsequence 1.1. So, in the case of the giant Zeppelins that had a gross lift of 150 tons, their size would be about the same as 150,000 kitchen stoves stacked together. This much gas provides one kilogram of lift. As an easy way to envision this relationship, an electric stove occupies about one cubic meter of space. The lift of an airship is directly proportional to the weight of the air that is replaced by helium or hydrogen. If enough water is replaced by air, the submarine gradually floats to the surface because its overall density is less than the water around it. Compressed air is stored onboard the submarine, which can be released to push water out of the ballast tanks. Since the density of water is about 1,000 times more than air, for every cubic meter of water a submarine expels from its ballast tanks, the vessel becomes one ton (1000 kilograms) lighter. ![]() The buoyancy principle for a gas-filled airship is similar to the operations of a submarine, which controls buoyancy by substituting water for air (to go down) or vice versa (to go up) in its ballast tanks. As a rule, for each cubic meter of air replaced the container generates about one kilogram of lift. By replacing the air in a container with these lighter gases, the container becomes lighter. A quick peek at the periodic table of the elements reveals that two gases in particular, hydrogen and helium, are made up of molecules much smaller than nitrogen and oxygen, so these gases are lighter than air. As per Avogadro’s Law, its weight is proportional to the molecules that comprise air that is 78% nitrogen, and most of the rest oxygen. It may come as a surprise, but a cubic meter of air weighs more than a kilogram. ![]() Like fish in water, we rarely consider the weight of the air around us. In this example, the oxygen balloon is eight times heavier than the helium balloon. The weight of the gas in these balloons is (roughly) proportional to the size of the gas molecules. As illustrated below, balloons of the same size, temperature and pressure that contain different gases, do not weigh the same. Avogadro’s Law, Gas Buoyancy, and Aerostatic FlightĪirship technology begins with Avogadro’s Law. Economic analysis of the giant airships begins with a clarification of their potential capabilities based technological principles.This post and the following three introduce the technological principles of airships. ![]() Understanding how helium or hydrogen gas allow an airship to float, and other principles of how airships work, enables us to appreciate what giant airships could do, if they were built using modern technology. The optimism of airship advocates is based on scientific principles of which most people are only mildly aware. ![]()
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