2023 | Book

# Lighter Than Air Systems

## Proceedings of the International Conference on Design and Engineering of Lighter-Than-Air Systems 2022 (DELTAs-2022)

Editor: Dhwanil Shukla

Publisher: Springer Nature Singapore

Book Series : Lecture Notes in Mechanical Engineering

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This book presents select peer reviewed proceedings of the International Conference on Design and Engineering of Lighter-Than-Air Systems (DELTAs 2022) which was held at the Department of Aerospace Engineering, Indian Institute of Technology (IIT) Bombay. It highlights current research trends and advancements in the field of lighter-than-air (LTA) systems. The topics covered include design (conventional and unconventional), aerodynamics (CFD), structures, loads and materials, stability and control, operations and ground handling, multidisciplinary design optimization, and novel applications of LTA systems. The book will be a valuable reference for researchers and professionals interested in lighter-than-air systems and allied fields.

##### Effect of Geometrical Parameters of a Tethered Aerostat on Longitudinal Stability Boundaries
Abstract
Dynamic instabilities often impair the operations of a tethered aerostat (such as supporting antennas and/or aerial platform), especially during the strong wind conditions. Effect of various geometrical parameters on longitudinal stability boundaries of an aerostat tethered in a steady wind is presented in this paper. The mathematical modeling used for stability analysis of the tethered aerostat includes buoyancy forces, apparent mass terms and static forces resulting from the tether cable. The effect of systematic variation of geometrical parameters on longitudinal stability boundaries of the tethered aerostat has been presented graphically. The presented longitudinal stability analysis and a judicious/feasible choice of various geometrical parameters of the tethered aerostat can be utilized to design a new aerostat that can remain longitudinally stable for wide range of wind speeds.
Rakesh Kumar, A. K. Ghosh
##### CPACS LTA—Using Common Data Structures for Visualization and Optimization of Airship Designs
Abstract
Complex engineering projects require compartments from different engineering fields to work in close contact and exchange data from their workflows and specialized software tools regularly. Common data models are an immanent feature of systems engineering applications that can be used to reduce the number of interconnections between software modules. Using common open-source data structures in airship design helps engineers in evaluating and visualizing early designs using several methods. In the presented paper, we used the Extensible Markup Language (XML) data structure Common Parametric Aircraft Configuration Schema (CPACS) and associated high-level software libraries by German Aerospace Center (DLR) for a design optimization. The design optimization maximizes payload of a 15 t airship by its hull shape. Handbook methods for estimating weights and drag as well as a brute force algorithm are used in the design optimization. The result shows an explicit optimum of the design. With the experiences made, we developed an updated version of CPACS, allowing the definition of an additional vehicle category named ‘dirigible’.
Carl S. Eissing, Alexander Richter, David Schlipf
##### Airship Sling-Load Operations: A Model Flight-Test Approach
Abstract
The transportation of heavy loads is the ultimate yet to be achieved mission for airships. Several other cargo is being transported by airships successfully. Objective of this research is focused on how load exchange with near equilibrium airships can be performed. Proposed solutions aiming at similar targets have not demonstrated successfully yet or did not meet certification requirements. We introduce a viable approach and describe the procedure that resembles helicopter sling load operations, step-by-step. Demonstrating its viability is achieved by building a suitable airship model and performing model flight tests. The research identifies weaknesses and critical points in load exchange procedures. Setting up the flight test environment, controller and suitable airship configuration is the first step performed. Operational challenges during the flight missions result in learnings and observations of importance for performing such flight tests. Observations regarding maneuverability of the model help in improving the propulsion and controller configuration of heavy load airships.
Johannes Eissing, Carl S. Eissing, Erich Fink, Martin Zobel, Florian Antrack
##### Optimization of TPU/TiO2 Films Using UV Additives for Improved Weather Stability of LTA Hull Materials
Abstract
Titanium dioxide has sustained a vital role over the past few years as the most widely used material among various commercial inorganic UV absorbers due to its chemical stability, low cost, and good UV protection. TiO2 and numerous organic UV absorbers have been explored to be incorporated in Thermoplastic Polyurethane (TPU)-based films for coated and laminated textiles useful for aerostats and airships as Lighter than Air (LTA) hull material. TPU films based on TiO2 were prepared using commercially available UV additives (Hindered amine light stabilizer, benzotriazole-based UV absorber, and antioxidant) at various concentrations. Prepared films were optimized to achieve the best possible combination of all UV enhancing materials and assessed for artificial weathering tests. UV–VIS spectrum and infra-red spectrum were obtained. Characterization of material and another testing such as tensile testing, yellowness index, UPF, and gas barrier properties of prepared TPU/TiO2 films were determined after every 100 h. TPU/TiO2 films that incorporate UV absorbers and other additives accomplished the requirement for improved resistance against UV and photo-oxidation.
Bharti Rana, Neeraj Mandlekar, Shuchita Tomar, Mangala Joshi, S. Wazed Ali
##### Airship Turn Performance Estimated From Efficient Potential Flow Panel Method
Abstract
A first-order potential flow panel method is used in the present work to calculate aerodynamic yaw torques and other parameters involved in the turning performance of a stratospheric lighter-than-air airship. A specific mesh is generated to model the airship geometry in order to solve the Laplace potential flow equation by a sum of source and doubled distributions on the boundary, using a mix of Neumann and Dirichlet boundary conditions. As a result, it is possible to simulate the effect of the rudder and elevons within their angular range at different flight conditions. Air flow rotation is included in the boundary conditions to simulate airship yaw rate. Thus, the result of the model includes not only yaw momentum but also its derivative with respect to yaw rate and the lateral force. They are contrasted with a series of tests carried out in a wind tunnel for a stratospheric airship model and with the literature. Despite of the simplicity of the potential method (5 s execution for a 6000-cell mesh) compared to a more complex CFD simulations, the conclusions demonstrate that the correlation between numerical and experimental data is high enough to provide valuable performance insights during the design process, showing a considerable reduction of the necessary computational resources. A 30 m ECOSAT model with proper fins can turn with a steady radius of 50 to 60 m.
Jesús Gonzalo, Diego Domínguez, Deibi López, Carmen Salguero
##### Evaluation of High-Performance Fabric-Based Laminated Hull Material for High-Altitude Airship
Abstract
The aim of the present study was to develop a continuous laminated material system that could be very lightweight, having very high strength, extremely low helium permeability. In this paper, a multilayered laminated structure has been designed, prepared, characterized, and developed using high-performance fabric including para-aramid fabric as a strength layer due to high strength-to-weight ratio and excellent mechanical properties in order to achieve a lower aerial density material with the help of PU-based adhesive and different polymeric films including PVF film as a weather resistance layer and BOPET film as a gas barrier layer. The artificial weathering of all the prepared specimens was carried out in a machine from 100 to 400 h in order to decide the approximate durability of the laminated samples. The prepared unexposed and exposed laminates were subjected to various mechanical and physicochemical characterizations such as tensile testing, cut slit tearing testing, t-peel testing, helium gas permeability testing, and UV protection factor testing. It has been investigated that the helium gas permeability of based para-aramid laminate (K5 laminate) was 0.04 L/m2/day which is extremely low and there was no significant change in tensile properties from fabric to laminate, even after 400 h of UV exposure. The tearing strength of laminates was significantly enhanced than that of fabric due to the greater flexibility of PU adhesive. Therefore, using this type of multilayered laminated fabric would be the potential, effective and new alternative for the envelope of high-altitude airship applications.
Shikha Chouhan, Rishabh Tiwari, B. S. Butola, Mangala Joshi
##### Look Ahead Steering-Based Path Following Control for an Airship
Abstract
This paper describes design and development of an integrated guidance, navigation, and control (GNC) algorithm for smooth navigation of an airship following a series of planar waypoints for surveillance applications. The guidance algorithm employed in this study is a look ahead-based steering guidance law which provides the required guidance command to the controller for executing the target mission. The command signal generated by guidance law is based on the airship current location relative to the next target waypoint. Two different control architectures are used in the GNC algorithm in order to execute the guidance command and carry out the path following mission. A proportional–integral–derivative (PID) law-based outer loop kinematic controller is designed to control airship attitude/orientation, and a linear quadratic regulator (LQR)-based inner loop optimal controller is designed to control the airship’s speed and angular rates. Performance and robustness of developed GNC scheme are evaluated in MATLAB®-based simulation environment for two different flight scenarios. Results show that an optimal path following trajectory is obtained with minimum deviation from the given target waypoints.
Ramesh P. Hun, Nandan K. Sinha
Abstract
Shuchita Tomar, Neeraj Mandlekar, Bharti Rana, Mangala Joshi, B. S. Butola
##### Degradation Study of Aromatic and Aliphatic TPU Films in Accelerated Weathering: Impact on the Gas Barrier and Mechanical Properties
Abstract
This study investigates the influence of the artificially accelerated weathering test on the degradation behaviour of thermoplastic polyurethane (TPU) films. Accelerated artificial weathering test parameters were specially designed to simulate outdoor natural exposure parameters with higher UV radiation exposure. Artificial weathering tests were carried out in a laboratory weatherometer and changes in mechanical properties, chemical structure and morphology were studied. In this study, two types of polyether-based aromatic and aliphatic TPU films were exposed for 500 h. The result shows that exposure to UV radiation affects the key properties like breaking strength, helium gas barrier and surface properties of TPU films. The mechanical strength reduces as the irradiance time is increased. The SEM and AFM analysis reveal that the film surface that was exposed to irradiance become rough, and cracks on the surface were observed. The FTIR analyses of the exposed film prove that chemical structure changes due to the formation of the polyurea group. It was found that aromatic TPU gets crosslinked after 300 h exposure; however, in aliphatic TPU, long molecular chains break into shorter chains, and the number of chain scission increases with increasing exposure time.
Neeraj Mandlekar, Rishabh Tiwari, Sampath Parasuram, Mangala Joshi
##### A Multidisciplinary Design Optimisation (MDO) Algorithm for the Automatic Sizing of an Unmanned Lighter-Than-Air Platform
Abstract
This study aims to present a multidisciplinary design optimisation (MDO) algorithm for the automatic sizing and design of an unmanned lighter-than-air (LTA) platform, given its mission requirements. The mission in question consists of territorial mapping, made possible through the implementation of several remote sensing on-board systems. Once assigned the parameters of the mission as inputs, the algorithm, through a process of iterations, returns the optimal sizing of the airship, shows the distribution of all the systems’ masses, and chooses the preferable energy system between the two considered (fuel cells or batteries). Moreover, a sensitivity analysis on the main variables allows to examine how the variation of each of the parameters of the mission affects the distribution of the masses in the airship, and therefore, how the optimal design and sizing change. Finally, further studies on the energy systems are presented, to verify the convenience of one option above the other one as a function of the distance from the mission location and the survey area.
Piero Gili, Ludovica Castronovo, Marco Civera, Rinto Roy, Cecilia Surace
##### The Concepts of Telescopic and Self-Deployable Tensegrity-Based Helium-Filled Aerostats
Abstract
In this contribution, we propose two novel concepts of an adaptive ultra-light high-altitude aerostats. Both proposed concepts enable changes of aerostat volume and shape during the flight, which results in the possibility of vertical motion control. The first proposed construction is telescopic aerostat with multi-segmented construction and controllable segments’ couplings. In turn, the second construction is based on a self-deployable tensegrity structure equipped with pre-stressed and tensioned elements of controllable lengths. Basic advantages and features of the proposed design are shown using dedicated numerical examples.
Lech Knap, Andrzej Świercz, Cezary Graczykowski, Jan Holnicki-Szulc
##### Numerical Investigation of Laminar to Turbulent Boundary Layer Transition Over Airship Envelopes
Abstract
The shape of a conventional airship’s envelope is usually an axisymmetric body of revolution. Previous numerical and experimental studies have indicated that at zero angle of attack, the flow over such shapes is either fully turbulent or transits from laminar to turbulent at nearly half of the envelope’s length. In most numerical investigations of such bodies, k-ɛ or k-ω-SST turbulence models are used. In recent studies, a four-equation k-ω SST-LM transition turbulence model has been proposed and shown to predict transition on a flat plate quite well. In this study, the transition of the laminar boundary layer to the turbulent boundary layer over the bodies of revolution of airship envelopes is investigated using the k-ω SST–LM transition turbulence model. The results obtained in numerical analysis are validated with the data available in the literature. It is seen that the two-equation k-ω SST turbulence model is not able to capture the laminar to turbulent transition, whereas the four-equation k-ω SST-LM transition turbulence model can capture it quite well.
Ashish Magar, Shantanu S. Gulawani, K. M. Kiran Babu, Rajkumar S. Pant
##### Designing Helium-Filled Aerostats Applying Scaling Procedure, Mini-Models CANDY and Fly-Tests on SKYLAB
Abstract
Helium-filled aerostats can be lifted by the traditional hot-air balloon (SKYLAB), in the compact form, and then, after reaching some starting level $${H}_{1}$$, helium can be pumped into the aerostat (using storage tank with a compressed gas), starting its autonomous mission. Optimal design process of aerostats dedicated to perform determined mission (between the altitudes $${H}_{1}$$ and $${H}_{2}$$) will be discussed with preliminary experimental verification process, based on scaling procedure of aerostat mini-model, so-called CANDY, and fly-tests on SKYLAB will be proposed.
Jan Holnicki-Szulc, Lech Knap, Andrzej Świercz, Grzegorz Mikułowski, Cezary Graczykowski
##### Effect of Reynolds Number on the Aerodynamic Characteristics of Leading-Edge Protuberanced Airship Fin
Abstract
In this paper, we present the computational investigation on the aerodynamic characteristics of the leading-edge protuberanced (LEP) fins subjected to Reynolds number in the range of 102 to 106 for wide range of angles of attack between 0o and 45°. The aerodynamic force coefficients like coefficient of lift (CL), coefficient of drag (CD) and surface pressure distribution with respect to chordwise position (x/C) for the modified leading-edge protuberanced models at different Re are analysed in detail. Assessment of aerodynamic characteristics of modified leading-edge protuberanced fins under different Reynolds number is one of the immediate issues which needs to be addressed to bring such novel design in to airships and different kinds of LTA platform.
S. Arunvinthan, C. Hari Babu, V. Manoj, S. Nadaraja Pillai
##### Autonomous Tilt Rotor Stabilized Plimp Hybrid Airship Unmanned Aerial Vehicle
Abstract
Stabilizing the remotely operated hybrid VTOL tilt rotor unmanned aerial vehicle that has an envelope of gas particularly installed to provide hydrostatic buoyancy force to generate lift, with a payload bay equipped with sensors and electronic components attached to the envelope and having a pair of wings extended on both the sides of the bay to generate lift through motion as well act as a stabilizing surface, and the thrusters pivoted at wing tip would be tilted with powerful servo motors to provide vertical takeoff and landing capabilities. This manuscript deals with stabilizing the undamped forces and moments using automatic control system. Mathematical modeling of equations would be framed based on the obtained kinematics of flight that would be converted to autopilot codes in MATLAB. The MATLAB results further determine the stability of the designed tilt rotor Plimp unmanned aerial vehicle.
N. C. Ajay Vishwath, Saras Takearya, Tanishka Mourya, Ashish Prajapati
##### Numerical Approach to Maneuver Design and Feasibility Evaluation for the Autonomy of Airship
Abstract
Maneuver design is a vital prerequisite for autonomy in aerospace guidance and control. It ensures system safety by analyzing the feasibility of the proposed maneuvers. This paper demonstrates a holistic approach to maneuver design by emphasizing its feasibility with consideration on the complete dynamics of the system and its constraints. Computational bifurcation analysis is employed to generate a sequence of trim solutions based on specified state and control constraints that define a stipulated maneuver. Implementing this approach on a stratospheric airship model helps attempt a few of its challenging and interesting facets like autonomous hovering, ascending, and descending by gauging its performance and formulating realistic maneuvers pertaining to the imposed limitations on the lateral excursion, control, and state constraints. The effectiveness of the proposed maneuvers is then evaluated using numerical simulations with computed control schedules in an open-loop.
Duraisamy Gobiha, Nandan K. Sinha
##### Estimation of Stability Derivatives Due to Translational Motion of Various LTA Vehicles Using CFD
Abstract
In this paper, the aerodynamic model parameters (stability derivatives) of the aerostat are investigated based on a CFD-based approach. The stability derivatives due to the translational motion of the aerostat are considered for the analysis in this paper. The extraction of the stability derivatives involves the simulation of the oscillations of the aerostat along the vertical direction (heave motion) and axial direction (surge motion). A forced sinusoidal oscillation is used for the simulation of the aerostat, and one stable period of oscillation is taken for the derivatives extraction. Four different aerostats are considered for the current study with four different angles of attack. Zhiyuan aerostat, HAA aerostat, NPL aerostat and GNVR aerostat are the aerostats considered for this study. The stability derivative results obtained for the four aerostats are analysed and compared with respect to their geometrical features. The dynamic stability derivatives of the Zhiyuan aerostat suggest its superiority among the four aerostats considered.
Anoop Sasidharan, Ratna Kishore Velamati, Sheeja Janardhanan, Venkata Ramana Murthy Oruganti, Akram Mohammad
Title
Lighter Than Air Systems
Editor
Dhwanil Shukla