This research goes throughout the general design steps for an airship starting by skeleton, outer surface and balloons that give the airship the necessary buoyant force to fly by filling these balloons with a lifting gas that is less dense than the surrounding air. Controlling the airships altitude, it could be achieved by changing the overall density of airship. The Drag coefficient is calculated using ANSYS, therefore the thrust power required for airship to move is calculated.
Different energy alternatives used to drive the airship was comprehensively studied for economic operation. These alternatives vary between renewable (Solar energy and fuel cell) and traditional (diesel) energies. A Comparison between these alternatives is presented. It was found that solar energy with fuel cell is the most effective system for long duration flights (greater than 14 days). Although traditional energy (diesel) seems most economical in short duration flights (less than 14 days), the renewable energies are environmental friendly where there is no harmful exhaust as well as minimum fire and explosion risk.
Rigid airship is a mean of transportation that can be used to flourish economy. Airships can be used in different applications such as Freight and passengers' transportation, communications, weather forecasting, agriculture, observing environment, conditions monitoring for farmlands, tourism, as a crane and in research.
Abstract
Rigid airship is a mean of transportation that can be used in Egypt to flourish economy. Airship can be used in different applications such as Freight and passengers' transportation, communications, weather forecasting, agriculture, observing environment, conditions monitoring for farmlands, tourism, as a crane and in research.
This research goes throughout the general design steps for an airship starting by skeleton, outer surface and balloons that give airship the necessary buoyant force to fly by filling these balloons with a lifting gas that is less dense than the surrounding air. Controlling the airship altitude, it could be achieved by changing overall density of airship.
Drag coefficient is calculated using ANSYS, therefore, thrust power required for airship to move is calculated.
Different energy alternatives used to drive airship was comprehensively studied for economic operation. These alternatives vary between renewable (Solar energy and fuel cell) and traditional (diesel) energies. Comparison between these alternatives was presented.
It was found that solar energy with fuel cell is the most effective system for long duration flights (greater than 14 days).
Although traditional energy (diesel) is seemed most economical in short duration flights (less than 14 days), the renewable energies are environmental friendly where there is no harmful exhaust as well as minimum fire and explosion risk.
Index Terms
Airship, solar airship, airship design, propulsion, Drag coefficient, Ansys, energy alternatives, Ragone chart, fuel cells.
1. Introduction
Airship is lighter than air Aircraft. It moves horizontally in the air depending on its power and flies vertically using buoyant force gained from balloons that are filled with gases. These gases are lighter than surrounding air called lifting gases as example helium, hydrogen and even hot air can be used. In early airships, the lifting gas used was hydrogen, due to its high lifting capacity and ready availability. Helium gas has almost the same lifting capacity and is nonflammable, unlike hydrogen. The outer envelope of the airship may be formed from its single gas bag, or may be a separate supported skin. Besides the main envelope, the airship has engines, crew and/or payload accommodation. Airships obviously have a great advantage over traditional planes which is airships do not consume a power to maintain flying as airships have static lift ,not dynamic lift as planes. This reduces the energy and fuel consumption and that lead to operating costs reduction. Airships are faster than ground and sea vehicles (1).
A. Airships versus planes
- Airship is not risky as planes.
- Airship can carry heavy loads without need of such huge amount of fuel that is lost in dynamic lift in planes because it depends on static lift.
- Airship does not need to airport, it can land in place with little infrastructure or without any infrastructure at all. It can even unload while flying.
B. Airship types
The airships have main three types which are nonrigid, semirigid, and rigid (2).
- Nonrigid airships, these airships gain its shape from internal pressure, also called blimps, aerostats.
- Semirigid airships are much like nonrigid airships maintain the envelope shape by internal pressure, but have a part of supporting structure, like fixed keel. This allows for the airship to be longer and carries a heavier weight than non-rigid airship.
Rigid airships have an outer structure giving it a fixed shape and gains lift from internal balloons that contain lifting gases. The affecting loads are distributed on the outer structure.
The present study was executed with the main objectives summarized as follows:
1- To develop model for airship.
2- To investigate airship systems.
3- To calculate power consumption for the selected airship model.
4- To compare between different alternatives supplying airship with power.
In view of these goals, an extensive review of the literature on rigid and non-rigid airships as well as the different energy alternatives and airships design parameters was done.
2. Airship Systems Design
In this section, the necessary systems design of airship is covered. The aim is to describe these systems and approximately calculate the weight and power consumed, if there is any, for each system. Figure 1 illustrates dimensions for airship and location sketch for some parts in airship such propellers, helium ballons, control cabinet and area specified for cargo.
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Figure 1 location sketch showing dimensions and some parts in the airship
2.1 Airship Body
The airship body consists of aluminum frame structure surrounded by outer envelope consists of three layers made of different materials. The airship body shape is Tri-axial ellipsoid with distinct semi-axis lengths where c>b>a as illustrated in Figure 2. In this case, a=20 m, b=30 m, c=50 m. So for the airship, H=2a, W=2b, L=2c.
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Figure 2 Tri-axial ellipsoid with distinct semi-axis lengths where c>b>a
Taking into consideration these dimensions, then using Ellipsoid equations to calculate volume and surface area of airship yields:
Airship volume is
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The Surface Area of the airship is calculated by the following approximate formula
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Where p ≈ 1.6075 for spherical ellipsoids. (Knud Thomsen's formula) (3) .
Aluminum Frame structure
It is very important to have a very light structure for the airship, but it has to be powerful enough to afford its weight and for this reason is one of the best choices (aluminum density = 2700 kg/m3). Structure consists of transverse frames welded with longitudinal frames.
To estimate the structure weight, a curved tri truss is used as shown in Figure 3; truss consists of three aluminum pipes with following specifications:
- Each pipe outer diameter of 4 cm.
- Thickness of pipe 0.5mm.
- Pipes welded together with three links, each link length L= 8 cm.
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Figure 3 Aluminum curved tri truss
Structure consists of transverse frames welded with longitudinal frames.
- There are 6 transverse frames distributed along the airship body (weight of transverse frames = 836 Kg).
- There are 15 symmetrical longitudinal frames installed from front to rear of the airship (weight of transverse frames = 4979 Kg).
- Total weight of aluminum frame structure = 5815 Kg.
Outer Envelope
The external hull skin of the airship have the following characteristics (4):
- High strength.
- UV (Ultra Violet) and ozone resistance.
- Weatherproof outer layer to protect the system from environmental degradation.
- Lower gas permeability to minimize gas losses.
- Flexibility at wide range of temperature.
- Longer Durability and life time.
Outer airship envelope material is better to be multi-layered flexible laminate because a single layer will not be able to achieve all the needed characteristics. This multiple layered material is consisted of three important layers which are:
- Strength Layer.
- Adhesive Layer.
- Protective layer.
Table 1 illustrates Material Selection for hull skin, taking into consideration material density and thickness, and then the weight can be calculated for each layer.
Table 1 Material Selection for hull skin , (4)
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After calculations, Total weight for outer envelope = 15738 Kg.
2.2 Helium Balloons
The airship gains its lift from the helium balloons that are enclosed inside its body. Three balloons are allocated inside airship. They are keeping the airship floating horizontally due to symmetrical distribution as shown in Figure 4. Balloons dimensions are 12 m radius for smallest while largest is 15 m radius.
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Figure 4 3D drawing shows Helium balloons configuration inside airship
Max enclosed volume that can contain helium
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Total surface area for the balloons
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The helium balloon of the airship have the following characteristics:
- Low temperature flexibility
- Light weight
- Low gas permeability
- Ozone resistant
- Abrasion resistance
- Long service time
[...]
- Arbeit zitieren
- Mahmoud Hebeshy (Autor:in), 2018, Rigid Airship Energy Systems. Renewable versus traditional energy, München, GRIN Verlag, https://www.grin.com/document/465515
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