Abstract
Abstract The design and development of Stratospheric Airships for High-Altitude Long-Endurance missions (HALESAs) has generated interest worldwide. Conventional airships usually have a single-lobed axisymmetrical envelope shape. In contrast, several non-axisymmetric envelope configurations have been proposed for the HALESAs, such as flattened single lobed and multi lobed. This paper describes a methodology for carrying out a comparative analysis of a conventional HALESA and the multi-lobed HALESA designed for the same design mission. A sizing methodology which enables the estimation of its design parameters to meet some user-specified requirements has been developed for airships with envelopes of both these shapes. A Multidisciplinary Design Optimisation (MDO) approach has been followed in this methodology, which includes considerations from the disciplines of aerodynamics, energy, environment and structures. The study indicates that the envelope volume, solar array area and total mass of the single-lobed conventional airship are better than those of the tri-lobed HALESA. While the multi-lobed HALESA has the advantage of a flatter upper surface resulting in higher efficiency of the solar panels, the conventional airship has lower drag, which results in superior mission performance.
Highlights
Depletion of fossil fuels and environmental concerns such as noise, pollution and global warming have supported the resurgence of airship technology as an efficient aerial platform for a wide range of applications and operations in the civil and defence sectors
The lift and drag of an airship are determined by the volume of the envelope, and the volume of an airship needs to be fixed in the primary design phase itself
A Computational Fluid Dynamics (CFD) study on the complete configuration of a hybrid air vehicle with a shape similar to the Airlander 50 airship of hybrid air vehicles reported by Carrión[43] shows that the volumetric drag coefficient of the bare hull obtained from the CFD is 1.44 times the value calculated using Hoerner’s equation by assuming the multi-lobed body equivalent to an ellipsoid
Summary
Depletion of fossil fuels and environmental concerns such as noise, pollution and global warming have supported the resurgence of airship technology as an efficient aerial platform for a wide range of applications and operations in the civil and defence sectors. For highaltitude long endurance missions, a special category of stratospheric airships has emerged (HALESAs). These systems are to be deployed for months at a stretch at altitudes ranging from 15 to 20km above the Earth’s surface, where the temperature is approximately constant, wind intensity is quite low and stable[1,2,3,4] and the wind moves horizontally at this band of altitudes[5]. To achieve long endurance flight at a high altitude, these systems generally use solar energy to meet their own propulsive power requirements, as well as the power needs of the onboard mounted payloads.
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