Coated and Laminated Textiles for Aerostats and Airships

Material Challenges and Technology

Mangala Joshi

• Publisher: CRC Press
• Year: 2022
• Print ISBN: 9781138360693
• eBook ISBN: 9780429780653
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

This book covers material challenges and technology innovation in coated and laminated textiles for aerostats and airships. Aerostats/airships are lighter-than-air (LTA) aircraft which are generally used in defence applications and face many harsh environmental conditions. For sustaining such conditions, there are special requirements for the material to be used in aerostats/airships which generally include a multi-layered coated/laminated textile using a textile fabric in base layer and different polymers for coating/lamination. Therefore, this book covers typical materials developed by different countries, challenges for developing material for aerostat/airship envelope and the future scope.

Features:

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• Exclusive title on materials used for LTA envelopes.

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• Discusses material challenges such as selection of suitable fibre, polymer, additive, coating/lamination techniques, joint type and sealing techniques.

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• Includes typical materials developed by different companies and researchers worldwide.

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• Clearly explains technical concepts using figures, schemes and tabulated data.

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• Includes case studies on material developed for aerostats/airships by different countries including NASA, Lockheed Martin, JAXA, ADRDE and DRDO.

This book is aimed at graduate students, researchers and professionals in textiles engineering and aerospace engineering.

1 Introduction to LTA Systems: Aerostats and Airships

Mangala Joshi

Indian Institute of Technology, New Delhi, India

Bapan Adak

Kusumgar Corporates Pvt Ltd, Gujarat, India

DOI: 10.1201/9780429432996-1

Contents

1. 1.1 Introduction
2. 1.2 Different Types of LTA Systems
3. 1.3 Applications of Aerial Platforms
   • 1.3.1 Atmospheric Estimations/Studies
   • 1.3.2 Surveillance/Reconnaissance
     • 1.3.2.1 To Overcome Military Surveillance Challenges
     • 1.3.2.2 Towards Non-Military Applications
     • 1.3.2.3 Stratobus as the Sentinel of the Stratosphere
     • 1.3.2.4 CNIM Air Space
     • 1.3.2.5 SkyStar 180
   • 1.3.3 Telecommunications
     • 1.3.3.1 Loon LLC
     • 1.3.3.2 Aerostat for Wireless Communication in Remote Areas
     • 1.3.3.3 Aerostats in Australia
   • 1.3.4 Scientific Research
     • 1.3.4.1 Ultra-Thin Balloons for High-Altitude Research
     • 1.3.4.2 Development of Ultra-Thin Balloon Film
     • 1.3.4.3 The First Trial on Ultra-Thin Balloon Film Extrusion
     • 1.3.4.4 Trial Balloon Fabrication Using 3.8 μm Film
     • 1.3.4.5 Trial Balloon Fabrication Using 3.4 μm Film
     • 1.3.4.6 Energy Harvesting and Power Generation
4. 1.4 Functioning of LTA Systems
5. 1.5 Working Atmosphere of LTA Systems
6. 1.6 Material Requirements for the LTA Systems
   • 1.6.1 Material Requirements for the Hull
     • 1.6.1.1 Strength Layer
     • 1.6.1.2 Weather Resistance or Protective Layer
     • 1.6.1.3 Gas Barrier Layer
     • 1.6.1.4 Sealing Layer
     • 1.6.1.5 Adhesive Layer
   • 1.6.2 Requirements for Ballonet Materials
7. 1.7 Challenges in Material Development for LTA Systems and Future Scopes
8. 1.8 Brief History of Development of LTA Systems
9. 1.9 Conclusion
10. References

1.1 Introduction

Lighter-than-air (LTA) aircrafts such as balloons, aerostat, blimps, airship and dirigibles are designed for various applications. Aerostat and airship are basically used in defence fields such as military surveillance, detection of aerial threats, etc., and also may be used for many other purposes such as network monitoring, weather forecasting, broadcasting, etc. [1, 2].

The LTA systems are filled with LTA gases such as hydrogen or helium, and they are continuously exposed under UV radiation coming from sunlight. Additionally, airships are also exposed under intense ozone as they work at much higher altitude compared to aerostat [3]. Moreover, the effects of temperature variation, pressure variation, rain and humidity also cause deterioration of envelope materials of LTA systems. Therefore, material development of LTA systems faces significant challenges, especially with regard to stratospheric airships, which require fulfilment of necessary criteria such as high strength, light weight, flexibility at low-temperature and capability of containing helium or non-flammable hydrogen gas for a long time. More importantly, it has to be weather resistant, which means it has to sustain under the exposure of harmful radiations such as UV and ozone, for providing a long service life. Here, multi-layered coated and laminated fabrics are used to fulfil all the requirements for this particular application, where a specific layer is used for a specific function [1, 4–6].

This chapter is all about the different types of LTA systems, the basic structure of the multi-layered envelope for an airship or aerostat, the requirements for each layer and different potential materials (polymers, fibres and fabrics) for different layers and challenges.

1.2 Different Types of LTA Systems

LTA systems can be classified in different ways. On the basis of working altitude, it may be two types – low-altitude aerostat and high-altitude airship (HAA). An aerostat is a tethered system; its working altitude generally varies between 2 and 5 km, and it operates from a fixed location by a mooring system. It is lifted solely by hydrogen or helium gas filled inside the envelope. No power is required to drive tethered LTA systems for station keeping or for controlling altitude, and it can be recovered easily for payload maintenance [1]. On the contrary, ‘Airship’ or HAA, is an untethered system and works at a higher altitude (about 17–55 km) from sea level. Airships are power driven and free-flight aircraft systems where lift is provided by a combined effect of lifting gas (such as hydrogen or helium) and aerodynamics. Recently, HAA systems operated above an altitude of 20 km from the earth surface are receiving more attention for multiple purposes. The working altitude of an LTA system is chosen based on many factors, such as severe weather conditions, jet stream or wind speed, and the presence of the “Federal Aviation Administration” (FAA) air-traffic layer [1, 7].

On the basis of the hull configuration or rigidity of the structure, an LTA system can be classified as: (i) rigid, (ii) semi-rigid and (iii) flexible. Non-rigid airship systems are also called blimps. Figure 1.1 shows different types of airships and their different components.

Figure 1.1 Different types of airships and their components. Source: Taken from https://ruor.uottawa.ca/handle/10393/36594 [8].

Conventional airships can be further classified on the basis of (i) payload capacity (heavy-lift and medium-lift) and (ii) the way of producing vertical force (heavier-than-air, lighter-than-air, and hybrid). Because of their light weight, low cost, simple structure, easy fabrication and less maintenance requirement, non-rigid, flexible-type LTA systems are preferred over others [9–11].

1.3 Applications of Aerial Platforms

Recent advancements in aerostat technology have achieved great success by making the application versatile. With the flexibility in volume, size and shape, the advanced aerostats have attracted tremendous applications in different domains. These structures are economical, handy and stable and can fly steadily over land as well as over sea in almost all weather conditions. These characteristics of aerostats brought profoundness in real-life solutions. The application domains have been broadly classifieds into five categories [1, 4, 10, 12, 13] and are discussed in their respective sections.

1. Atmospheric estimations/studies
2. Surveillance/reconnaissance
3. Telecommunications
4. Scientific research
5. Energy harvesting and power generation

1.3.1 Atmospheric Estimations/Studies

The weather/sounding-balloon is a high-altitude balloon that carries instruments aloft to transfer significant information on atmospheric conditions. In 1896, these balloons were employed by Léon Teisserenc de Bort, the French meteorologist, who launched hundreds of them from his observatory in Trappes. These experiments led to his discovery of the tropopause and stratosphere [14]. Military and civilian government meteorological agencies share all the data produced through these balloons, internationally. The balloons are usually made of highly flexible latex material such as Chloroprene and are usually filled with helium or hydrogen gas. The control over the gas pressure facilitates the change in altitude as per requirements. These balloons have a variety of applications; some of them are as follows:

1. These balloons are launched around the world to diagnose climatic conditions, viz. atmospheric pressure, temperature, humidity and wind speed, through a measuring device called a radiosonde using RADAR/navigation systems. The data are eventually processed by human forecasters and computer models for weather forecasting. About 800 locations around the globe do routine releases, usually at 0000 UTC and 1200 UTC.
2. There also exist specialized applications for aviation interests, pollution monitoring, photography/videography and research.
3. Moreover, field research programs often use mobile launchers from land vehicles as well as ships and aircraft. In recent years, they have also been used for scattering human ashes at high altitude as well as to create the fictional entity “Rover” in the TV series The Prisoner, filmed in Portmeirion [15].
4. Transosonde balloons (that stay at a constant altitude for a long period) helped in diagnosing radioactive debris from atomic fallout through experimentation in 1958.

Further, extending the potential of ballooning over the atmosphere of Venus, the VEGA balloon mission was launched by the Soviet Union in 1985. The hostile atmosphere on Venus had challenged the aerostat technology in creating exploration opportunities differently. In the mission, two aerostats were successfully deployed on Venus with 3.5 m super-pressure balloons at an altitude of about 55 km with the total payload being 6.9 kg; each was tracked from Earth for about two earth days.

In this period there were also several US and European proposals to fly such missions with technological advancements for meticulous explorations. Such missions had a further objective in developing an aerostat with larger payload capability than VEGA. The Jet Propulsion Laboratory (JPL) has been developing super-pressure balloons tolerant of both the sulfuric acid environment on Venus and capable of accommodating the diurnal stresses induced on the balloon. A 5.5 m balloon with a payload capability of 45 kg is at TRL 5, whereas a 7.0 m balloon with a payload of 110 kg is now under development [16]. In the past, several proposals have been made to apply this technology to the VALOR (Venus Aerostatic-Lift Observatories for in-situ Research) [17] and the European Venus Explorer (EVE).

Other, more ambitious concepts involved the deployment of sondes from the aerostat such that the aerostat could serve as both a platform for...

Table of contents

• Cover Page
• Half Title Page
• Title Page
• Copyright Page
• Contents
• Editor
• Contributors
• 1 Introduction to LTA Systems Aerostats and Airships
• 2 Modern Technologies for Manufacturing Aerostats and Airships
• 3 Fibres and Fabrics for Aerostats and Airships
• 4 Coated Textiles for the Envelope of Lighter-than-Air (LTA) Systems
• 5 Laminated Textiles for the Envelope of LTA Vehicles
• 6 Polyurethane Nanocomposite-Based Advanced Materials for Aerostat/Airship Envelopes
• 7 Weathering and Degradation Behaviour of Materials Used in Envelopes of LTA Systems
• 8 Developments in Weather-Resistant Polyurethane Coatings for Inflatables
• 9 Testing and Evaluation of LTA Systems
• 10 Modelling for Performance Analysis of Aerostats/Airships
• 11 Future Trends in the Area of Material Developments for Aerostats/Airships Future Trends in Material Developments
• Index