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Airship Design

Greatest volume to surface area ratio to minimize airship skin weight. 

Best aerodynamics performance, highest lift and lowest drag possible by CFD analysis. 

Design environment by estimating mass breakdown, volume and lift of hybrid airship design. 

Fabrication of airship as a test bed for attitude and altitude control system. 

Design and Analysis

A few design iterations have been made to achieve the required lift of the hybrid airship, while optimizing its weight, performance and lift. The design is required to have high volume to surface area ratio, great aerodynamic performance which implies highest lift and lowest drag possible.

 

For the design, the airship skin is designed with CAD in CATIA, providing the exact geometry of every skin section. The design also includes the inner structure of the triangular airship. The structure consists of 5 short ribs which are connected with 8 longerons. 

The shape design for hybrid airship is decided by the results of CFD analysis of a few design iterations. For the project, CFD analysis was carried out using Ansys-Fluent to study its aerodynamics characteristics when cruising. The analysis takes into consideration a reasonable airship cruise velocity. The thrust required for cruise is also determined from the drag force exerted on the airship in this simulation. 

Prototyping and Fabrication

The airship's gas bags are fabricated and tested on PS-01. The gas bags are first prototyped with easily available PVC and sealed using the hot iron sealing method. The leakage of the gas bags are checked by visual inspection. 

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Different types of seaming method are tested. 

  • L shape seam is torn apart easily with a slightly higher internal pressure in the gas bag. 

  • The overlap seam is strong enough butmore difficult to be fabricated with limited machining resources. 

  • Spiral seam is both strong enough and can be easily fabricated with hot iron sealing method. 

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Due to the lack of machining resources, PS-01 is improvised by outsourcing the fabrication of PS-02 airship skin to other companies. 

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Different materials have been considered for building the airship structure. The materials are chosen based on its properties, costs and availability. 

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The structure of airship is built using the carbon fiber rod. The hollow carbon rod is used due to its elastic property compared to the non-hollow carbon rod. For every section of airship, the thickness depends on how much it bends on the section.

 

Aluminium rods are used to build the front part of airship structure. This is because the front part of the structure is the most critical part with extreme bending. The carbon fibre rod is replaced with aluminium rod which is capable of retaining its shape and has high flexibility for conforming into the desired shape. The main problem with aluminium rods is its malleability which changes shape easily upon large force exerted on it.  

A non-rigid airship prototype of PS-02 is developed. The airship is adopted with a quadcopter rotor configuration for its control system.

 

Propeller mechanisms are designed to rotate for tilt rotor control and for producing reverse thrust for altitude hold.  

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