Long permanence high altitude airships: the opportunity of hydrogen

Abstract

MAAT cruiser/feeder airship system is a transport system financed by European 7th Framework programme 2011. The project aims to realize a cruiser/feeder airship system, which can connect major populated centres worldwide. The MAAT cruiser feeder system is based on two different airships, the cruiser, which remains airborne for long times, and the feeder, which connects the cruiser with the ground and vice versa. This paper traces a detailed bibliography about MAAT project showing the actual state of the art of the project. This bibliographic review allows understanding the level of innovation related to this project. Starting from the results of the preceding literature, the authors present a model of the cruiser, in terms of both mass and energy. According to the preceding studies, they have assumed the following minimal set of hypothesis: the buoyant gas is hydrogen; the shape of the cruiser is a discoid; operative altitude is in the range 15-17 km. It is well known that the major showstopper to actual diffusion of airships is related to the initial costs related to the use of Helium. The problem is more accentuated in Europe than in USA and Russia, because of higher unitary prices. An economic comparison with the possibility of using Hydrogen has produced. A further comparison has performed in terms of operations, focusing on the necessity of replacing the gas, which disperses in the external atmosphere because of the porosity of the tissues of the balloon system. The on board generation of hydrogen as an energy system is very convenient on long permanence airships because the replacement buoyant gas can be produced on board. It has been also traced a complete energy balance of the cruiser airship assuming it as discoid. On one side it has been evaluated the hydrolysis process against batteries showing that an hydrolyser/fuell cell cycle has a lower efficiency in comparison of batteries but it looks less expensive and presents a lower weight than any battery type. This paper has clearly demonstrated that the use of hydrogen is much more convenient than the uoiuse of Helium, even if it require an accurate design to minimize the risks related to hydrogen potential flammability. It demonstrates the necessity of using hydrogen as buoyant gas in long endurance airships because of the easiness of replacement. An estimation of the necessary energy requirements for a discoid airship has produced demonstrating clearly that a discoid shaped airship is energetically inefficient. These results force to consider a different and more efficient cruiser system. In conclusion this paper demonstrates clearly the necessity of using hydrogen to allow possible future airship renaissance, which could be a fundamental option for the future because of airships are the most energetically efficient aerial vehicles. This research activity has also clearly demonstrated that the initial discoid shaped cruiser hypothesis is not feasible on energetic point of view.