Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Inflatable structures have very interesting properties such as low weight, compact transport volume and easy set up. Both manned and unmanned aircraft have been built using inflatable wings. However, a severe drawback of inflatable wings is the small load-bearing capacity of such structures which limits the aspect ratio of this wing type. Introducing the structural concept of Tensairity overcomes this deficiency. Tensairity combines an inflatable structure with struts and cables and thus increases the stiffness and maximal load of the inflatable structure tremendously. A further improvement of the stiffness and ultimate load of Tensairity can be achieved by introduction of fabric webs into the airbeam. In this work, the concept of web-Tensairity was further developed into curved girders to be able to build wings with dihedral, sweep and twist. A comparison between a curved and a straight web-Tensairity girder proved that their load deflection behaviour was very similar and superior to a curved and straight airbeam with the same dimensions and internal pressure. The stiffness of the web-Tensairity girder was estimated analytically. To demonstrate the concept of Tensairity wings, the goal was set to build a Tensairity kite which flies stable on a single tether. The latest kite prototype has a span of almost 8 m and a projected area of 11 m2. Results of structural and aerodynamic tests of this kite are presented.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The kites we use now are conventional surfkites because of their long design and exploitation record. However specially designed gliders [5], inflatable [4], twinskin [9] or lightweight [3] kites, parawings [57] and parachutes [12] can produce even better results. ...
... Roll φ, pitch θ and yaw ψ affect components of vector d (4) in Earth-fixed reference frame [11] and v l is a cable speed. The set of possible coordinates and velocities D dictates that all kites should be above the ground at all times and the set of possible controls U defines possible attitude angles with which kites can fly (from -π/2 to π/2). . ...
Article
Full-text available
Laddermill flight control problem with closed loop is considered in this paper. Laddermill is an alternative concept for energy production using high altitude kites. The kites have been simulated as rigid bodies and the cable as a thin elastic line. Euler angles and cable speed are controls. Flight control is written as a fusion of two approaches: design of experiments and stochastic optimization. Such combination ensures finding global optimum for any reasonable number of parameters and objectives in a reasonable time while also collecting some information about sensitivities – these two features are much harder to achieve by other means. Robustness has been formulated as an additional objective. We found the system very steady despite big variations of wind velocity. The resulting optimal trajectories can be also used as a first iteration for open loop control algorithms. The methods used can be also employed in wide range of wind energy applications.
... The kites we use now are conventional surfkites because of their long design and exploitation record. However specially designed gliders [5], inflatable [4], twinskin [9] or lightweight [3] kites, parawings [55] and parachutes [12] can produce even better results. Pumping Laddermill operates as follows. ...
Article
Full-text available
Closed loop Laddermill flight control problem is considered in this paper. Laddermill is a high altitude kites system for energy production. The kites have been simulated as rigid bodies and the cable as a thin elastic line. Euler angles and cable speed are controls. Flight control is written as a fusion of two approaches: design of experiments and stochastic optimization. Such combination ensures finding global optimum for any reasonable number of parameters and objectives in a reasonable time while also collecting some information about sensitivities – these two features are much harder to achieve by other means. Robustness has been formulated as an additional objective. We found the system very steady despite big variations of wind velocity. The resulting optimal trajectories can be also used as a first iteration for open loop control algorithms.
... 22.6.5, the outer diameter of the flying rotor can exceed the diameter of the ground rotor to some degree. It is not a problem in the case of the implementation of a rigid or semi-rigid [11] flying rotor. But in the case of the implementation of a flexible rotor, the diameter of the Parotor should not exceed the diameter of the ground rotor. ...
Chapter
Full-text available
The study proposes a new airborne wind energy system based on the carousel concept. It comprises a rotary ring kite and a ground-based rotating reel conversion system. The moment generated by the ring kite is transferred by several peripheral tethers that connect to winch modules that are mounted on the ground rotor. A generator is coupled to this rotor for direct electricity generation. Because the ring kite is inclined with respect to the ground-rotor the length of the peripheral tethers has to be adjusted continuously during operation. The proposed system is designed to minimize the used land and space. This first study describes the fundamental working principles, results of a small-scale experimental test, a kinematic analysis of steady-state operation of the system and a power transmission analysis. Design choices for the ring kite are discussed, a strategy for launching and landing and methods for passive and active control are described.
... The resulting structure is lighter than straight rigid wings and more aerodynamically efficient and durable than fabric kites. 7. Special design kites: Kiteplanes [22] and Tensairity Kites [23] are projects developed by TUDelft (The Netherlands) and EMPA (Research Center for Synergetic Structures, ETH Zurich), that aim at increasing the aerodynamic efficiency of arch kites without using rigid spars. ...
Article
Full-text available
Abstract Among novel technologies for producing electricity from renewable resources, a new class of wind energy converters has been conceived under the name of Airborne Wind Energy Systems (AWESs). This new generation of systems employs flying tethered wings or aircraft in order to reach winds blowing at atmosphere layers that are inaccessible by traditional wind turbines. Research on AWESs started in the mid seventies, with a rapid acceleration in the last decade. A number of systems based on radically different concepts have been analyzed and tested. Several prototypes have been developed all over the world and the results from early experiments are becoming available. This paper provides a review of the different technologies that have been conceived to harvest the energy of high-altitude winds, specifically including prototypes developed by universities and companies. A classification of such systems is proposed on the basis of their general layout and architecture. The focus is set on the hardware architecture of systems that have been demonstrated and tested in real scenarios. Promising solutions that are likely to be implemented in the close future are also considered.
... Other publications being more or less related to structural principles exploiting pure tensile stresses are the concepts of "tensegrity" by Snelson, e.g. [5], "tensairity" by Breuer [6] and the book "lightness" by Beukers [7]. In all cases, very high structural efficiency of the used materials is evident. ...
... Wever (Wever et al. 2010) further investigated the possibility of improving this design via introduction of internal fabric webs. Relying on this feature, Breuer and Luchsinger (2010) report the potential in utilizing the web-enhanced Tensairity structure as an inflatable wing element. The structural behavior of a symmetric spindle-shaped Tensairity girder, from a static point of view, has been investigated in recent work by Luchsinger and Galliot (2013), , and Teutsch (2009). ...
Article
The dynamic analysis of a pneumatic beam structure, termed the Tensairity girder, is experimentally, numerically, and analytically studied. The structural concept of Tensairity relies on the combination of an airbeam with conventional struts, which leads in a light-weight structure of significant load-bearing capacity. By focusing on the analysis of the dynamic response of this structure, the objective of this work is to determine the pressure-dependent modal characteristics of the pneumatic beam and to couple these with the associated material properties. Based on the results of a modal identification procedure, relying on hammer and white noise excitation tests, a finite-element (FE) model is updated to reflect the actual system response. This procedure reveals the membrane’s shear modulus as the material property that more heavily relies upon the pressure level of the Tensairity girder. The experimental and numerical investigations indicate that the dynamic behavior of the beam can be expressed as a superposition of pressure dependent and pressure independent modes. The obtained insight allows for a better exploitation of the Tensairity in a new range of applications involving dynamic loading.
... Wever (Wever et al. 2010) further investigated the possibility of improving this design via introduction of internal fabric webs. Relying on this feature, Breuer and Luchsinger (2010) report the potential in utilizing the web-enhanced Tensairity structure as an inflatable wing element. The structural behavior of a symmetric spindle-shaped Tensairity girder, from a static point of view, has been investigated in recent work by Luchsinger and Galliot (2013), , and Teutsch (2009). ...
... Initial work was focused on increasing the stiffness of tube kites [4]. Detailed simulations with our tool KiteSim 2.0 revealed that precise pitch control is instrumental to fly efficient pumping cycles [12]. ...
Chapter
Full-text available
Pumping cycle kite power has attracted considerable interest over the last years with several start-ups and research teams investigating the technology. While all these groups produce electrical power with a ground-based generator in a cyclic process, there is no consent about the shape, structure and control of the flying object. In particular the launching and landing strategy has not been settled yet. TwingTec has followed a pragmatic approach focusing on the flying part of the system. The spin-off from Empa and FHNW has developed over the last years in close collaboration with leading research institutes from Switzerland the twing, an acronym for tethered wing. The guiding principle behind the design of the twing was to combine the light weight property of a kite with the aerodynamic properties of a glider plane. Launching and landing was solved by integrating rotors into the structure allowing the twing to hover. Launching, transition into crosswind, autonomous power production, transition into hover and landing has been demonstrated with the current small-scale test system.
... Plagianakos [13] and Wever [14] studied the static performance of spindle shaped Tensairity structures under axial compressive loads, revealing their potential as columns. Breuer and Luchsinger [15] applied the Tensairity concept to inflatable wings, overcoming the small load-bearing capacity of such structures. Recently, Tensairity arches were developed and investigated, showing that the Tensairity concept could bring many solutions for inflatable arch structures [16]. ...
Article
Tensairity dome is a lightweight spatial structure composed of struts stabilized by cables and airbags inflated by low pressurized air. Two forms of Tensairity domes with annular airbags, stiffened with central cables or webs placed between the upper and lower chords, were proposed based on the Tensairity concept. The zero-stress state, the initial state and the loaded state were successively simulated to investigate the static behavior of the structures, respectively. The results indicate that both two forms of structure have good static performance and the internal pressure in the airbag at about 1000–4000 Pa can ensure the stabilizing role of the inflated airbag. The investigation reveals the subtle interplay between the internal pressure and external loads in the load state, and the tremendous effect of temperature change on overall structure is predicted. The comparisons also show the benefits of webs in the structure for all load cases. Finally, the results show the attractive advantages of Tensairity dome in comparison with conventional structures in terms of structure weight and overall stiffness.
... 22.6.5, the outer diameter of the flying rotor can exceed the diameter of the ground rotor to some degree. It is not a problem in the case of the implementation of a rigid or semi-rigid [11] flying rotor. But in the case of the implementation of a flexible rotor, the diameter of the Parotor should not exceed the diameter of the ground rotor. ...
Data
"Airborne Wind Energy Conversion Using a Rotating Reel System" is the title of the chapter 22, authors Pierre Benhaïem and Dr. Roland Schmehl, of the second AWE book (Airborne Wind Energy Advances in Technology Development and Research), editor Dr. Roland Schmehl. This chapter is also, among other things, a part of my searches about this conversion system, within my Airborne Wind Energy Systems project investigating several sorts of AWES.
... The idea only began to be exploited more widely after 2000. Early work in the area was carried out by Diehl (2001); Houska and Diehl (2006), Ockels (2001), Lansdorp and Ockels (2005), Canale et al. (2007); Fagiano (2009) and Breuer and Luchsinger (2010). More recently many other researchers and start-up companies started contributing to the field. ...
Article
Full-text available
Large-scale kites, flying high-force crosswind trajectories, have been proposed for wind power generation. A two phase operational cycle generates net positive power using a ground-based motor/generator. In the traction phase the kite flies a high-force trajectory while reeling out the generator-connected tethers. A low-force retraction phase reels in the tethers and returns the kite to the start of the cycle. Highly variable conditions and significant uncertainty in the dynamics pose challenges to autonomous, well-controlled flight. The control task is divided into trajectory generation and tracking components and the most uncertain parameters in the model are identified online. The control structure uses these parameters in a robust framework resulting in an experimentally verified adaptive control scheme.
... The kites we use now are conventional surfkites because of their long design and exploitation record. However specially designed gliders [3], inflatable [2], twinskin [6] or lightweight [1] kites, parawings [34] and parachutes [8] can produce even better results. Pumping laddermill operates as follows. ...
Article
Full-text available
A new innovative approach to sailing has been proposed by TU Delft. It allows sailing in any desired direction, including straight into the wind. The concept consists of generating energy with a sky sail and then using it in an electric motor of the ship. The paper describes a mathematical model of laddermill sail.
... The low specific mass and transportation volume of tethered flying systems makes them generally an interesting option for wind energy harvesting on other planets with an atmosphere. Especially inflatable wings with rigid reinforcements can be scaled up efficiently to compensate for the substantially lower atmospheric density on Mars (Breuer & Luchsinger, 2010). An example for the effect of the lower atmospheric density and gravity on Mars is the aerodynamic design of NASA's Ingenuity drone (NASA, 2020;Chi, 2020). ...
Preprint
Full-text available
Generating renewable energy on Mars is technologically challenging. Firstly, because compared to Earth, key energy resources such as solar and wind are weak as a result of very low atmospheric pressure and low solar irradiation. Secondly, because of the harsh environmental conditions, the required high degree of automation and the exceptional effort and costs to transport material to the planet. Like on Earth, it is crucial to combine complementary resources for an effective renewable energy solution. In this work, we present the result of a design synthesis exercise, a 10 kW microgrid solution, based on a pumping kite power system and photovoltaic solar modules to power the construction as well as the subsequent use of a Mars habitat. To buffer unavoidable energy fluctuations and balance seasonal and diurnal resource variations, the two energy systems are combined with a compressed gas storage system and lithium-sulfur batteries. The airborne wind energy solution was selected because of its low weight-to-wing-surface-area ratio, compact packing volume and high capacity factor which enables it to endure strong dust storms in an airborne parking mode. The surface area of the membrane wing is 50 m2 and the mass of the entire system, including the kite control unit and ground station, is 290 kg. The performance of the microgrid is assessed by computational simulation using available resource data for a chosen deployment location on Mars. The projected costs of the system are 8.95 million Euro, excluding transportation to Mars.
... The low specific mass and transportation volume of tethered flying systems make them a generally interesting option for wind energy harvesting on other planets with an atmosphere. In particular, inflatable wings with rigid reinforcements can be scaled up efficiently to compensate for the substantially lower atmospheric density on Mars (Breuer & Luchsinger, 2010). An example for the effect of the lower atmospheric density and gravity on Mars is the aerodynamic design of NASA's Ingenuity drone (NASA, 2020;Chi, 2020). ...
Article
Full-text available
Generating renewable energy on Mars is technologically challenging. Firstly, because, compared to Earth, key energy resources such as solar and wind are weak as a result of very low atmospheric pressure and low solar irradiation. Secondly, because of the harsh environmental conditions, the required high degree of automation, and the exceptional effort and cost involved in transporting material to the planet. Like on Earth, it is crucial to combine complementary resources for an effective renewable energy solution. In this work, we present the results of a design synthesis exercise, a 10 kW microgrid solution, based on a pumping kite power system and photovoltaic solar modules to power the construction and subsequent use of a Mars habitat. To buffer unavoidable energy fluctuations and balance seasonal and diurnal resource variations, the two energy systems are combined with a compressed gas storage system and lithium-sulphur batteries. The airborne wind energy solution was selected because of its low weight-towing surface area ratio, compact packing volume, and high capacity factor which enables it to endure strong dust storms in an airborne parking mode. The surface area of the membrane wing is 50 m 2 and the mass of the entire system, including the kite control unit and ground station, is 290 kg. The performance of the microgrid was assessed by computational simulation using available resource data for a chosen deployment location on Mars. The projected costs of the system are €8.95 million, excluding transportation to Mars.
... Inflated wing HALE aircraft research was also conducted at the Defense Advanced Research Projects Agency (DARPA) for intelligence, surveillance, reconnaissance (ISR), and communications missions [9]. More recent designs include the development of inflated wing kites using the principle of tensairity, wherein the inflated wing is designed with struts and cables to improve its structural stiffness [19]. ...
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-0903.vid To assist in the design process of Toyota’s futuristic, high-altitude aerial platform concept, called ‘Mothership’, an experimental investigation of a swept, tethered, inflated wing was conducted in the Virginia Tech Stability Wind Tunnel. The test article is a 30⁰ swept back inflated wing of 1.06 m reference span, 0.31 m reference chord, and thickness to chord ratio of 0.20, mounted in a 30⁰ swept back 0.29 m reference span and 0.63 m reference chord aluminum mount. The experiment was conducted in the modular wall configuration of the anechoic test section at speeds ranging from15−32.5 m/s for three different tether attachment configurations. Along with static aeroelastic deformation data using a 3D photogrammetry system, aerodynamic measurements were taken in the form of Pitot and static pressure measurements in the wake of the wing, force and moment measurements at the base of the mount, and tension measurements at the tether attachment locations. Numerical 3D steady RANS CFD computations of the rigid 3D scanned inflated wing geometry were conducted in the wind tunnel environment. A detailed grid refinement study was conducted to guide grid sizing requirements for accurate numerical computations of such wings. Static aeroelastic deformation data from the 3D photogrammetry system, at a speed of 27.5 m/s, were used to deform the 3D scanned inflatable wing geometry, and 3D steady RANS CFD computations of this deformed inflated wing were conducted at a tunnel speed of 27.5 m/s, using both the k-ω SST and Spalart-Allmaras turbulence models. Good agreement is found with experimental data for the forces and moments as well as wake Pitot pressure coefficient contours. Comparisons are also made with the rigid wing CFD computations at the same tunnel speed of 27.5 m/s to illustrate the effect of static aeroelastic deformations on the aerodynamic performance, wake Pitot pressure coefficient contours and wing-tip vortex structures, of flexible inflated wings. These results show that RANS CFD computations can accurately model the effects of substantial static aeroelastic deformations on the aerodynamic performance of an inflated wing.
... Nous trouvons là un schéma déjà utilisé par Wielgosz [WIE03] pour la modélisation de tubes gonflables (voir également [DAV08] [BRE10]). Cela nous renvoie également à l'analogie qui est souvent faite entre les systèmes de tenségrité et un ballon gonflable, dans lequel les câbles tendus représentent l'enveloppe et l'air comprimé les barres. ...
Article
Ce mémoire présente mes activités en tant qu'enseignant-chercheur au sein du Laboratoire de Mécanique et Génie Civil (LMGC) de l'Université Montpellier 2, en vue de l'obtention de l'Habilitation à Diriger des Recherches. Les travaux de recherche exposés sont liés aux principales thématiques que j'ai pu développer dans l'équipe " Conception en Structures " du LMGC, essentiellement de 2004 à 2013.
Article
Tensegrity rings, sometimes also called hollow ropes, tubes or sleeve modules, are systems based on straight prism geometry and composed of one or more bar circuits and cables. Recently, we developed a general study for these structures, including their ability of folding. We designed and built a human-size prototype of a pentagonal tensegrity ring with 30 cables and 15 bars, connected to 15 nodes symmetrically spread on three layers. This prototype has been tested under compression loading in several experiments. Finite element (FE) simulations are consistent with the experimental observations. In this paper, we present an analytical model of the axial behaviour of such a ring. We show the influence of each element on the mechanical behaviour of the structure, and our study can be seen as a first step in adapting the response of the system to a static or dynamic behaviour. We also provide a rheological model for its axial behaviour under compression. Our model is reduced to four springs and gives an axial mechanical behaviour identical to that obtained by FE simulations. Thus, a macro-element tensegrity ring is presented which connects the axial symmetrical load to four nodal displacements.
Article
The load bearing behavior of an asymmetric spindle shaped Tensairity girder is studied experimentally and compared to finite element analyses. The influence of the air pressure on the stiffness of the structure is investigated for homogeneous distributed load, asymmetric distributed load and a local load at the center of the structure. An overall good correlation between experiments and finite element predictions was found. An analytical model based on two coupled ordinary differential equations is presented and solved for the homogeneous distributed load case. The role of the form of the Tensairity girder on the stiffness is investigated by comparing the load-deflection behavior of the asymmetric spindle shaped girder with a cylindrical shaped girder.
Article
Two new designs for spindle-shaped Tensairity girders with a reinforced coupling between the chords are proposed. The first one uses a continuous coated-fabric web and the second one a discrete reinforcement composed of 23 steel wire ropes to facilitate the load transfer between the chords. Both girders are studied experimentally and numerically and compared to the original design. A simple analytical model is proposed for the homogeneous load case. Results show that the behavior of the Tensairity girders is significantly improved by the integration of a reinforcement for all tested load configurations. Under homogeneous distributed load at 25 kPa the coupling increases the stiffness and the ultimate load by about a factor 3 and 2, respectively, while the weight of the girder increases due to the fabric web or the cables by only 12% and 29%, respectively. At 50 kPa a live load to dead load ratio of 95 has been achieved, which is twice as much as for the original design.
Article
The load-bearing behavior of a symmetric spindle-shaped Tensairity girder with 5-m span and thin chords is studied experimentally, numerically, and analytically. The influence of the air pressure on the load-deflection behavior is investigated for homogeneous distributed load, asymmetric distributed load, and central local load. An m-shaped deflection with two maxima at about one- and three-quarter of the span was obtained for homogeneous distributed loads whose distribution is not linearly dependent on the applied load. The slope of the load-deflection curve as well as the maximal load increases with increasing air pressure, demonstrating the stabilizing role of the inflated hull. An analytical model based on two beams coupled by an elastic foundation with air pressure-dependent properties is presented for the homogeneous distributed load case, and simple predictions for the average displacement and the maximal load are given. The model reveals the subtle interplay between the chords and the inflated hull leading to the peculiar displacement distribution of the system. Finite-element analysis shows the limiting influence of the low fabric shear modulus on the stiffness and load-bearing capacity of the Tensairity girder for local and asymmetric distributed load. The investigated spindle-shaped Tensairity girder is optimal for homogeneous distributed loads, where a live load to dead load ratio of more than 50 has been achieved.
Conference Paper
Full-text available
In the last decade, several research groups and companies around the world have been developing a new class of wind generators, aimed at harnessing the energy of winds blowing at high elevation above the ground. This kind of technology is usually referred to as Airborne Wind Energy (AWE) or High-Altitude Wind Energy. All of the proposed solutions exploit the high-speed flight of tethered wings, or aircrafts, and their operation heavily relies on automatic control. This paper provides a tutorial on the fundamental concepts of AWE and on the different technologies that are being investigated, with particular emphasis on control-related aspects, highlighting the accomplished results and the issues that still need to be solved.
Conference Paper
In the last years, a renewed interest in airships has led to an extensive research to study possible new applications. Such renewed interest is due to the main benefits inherent to airships, primarily its low energy consumption and hovering capabilities. In this line, the MAAT project aims to design a novel green air transport system. MAAT is conceived as a system of two type of airships, the so-called Cruiser, which stays at a constant 16 km altitude and displaces horizontally; and the so-called Feeders, which perform linking operations between ground and the Cruiser. Due to its mission requirements and the objective to generate the totality of energy by solar panels, the Cruiser conceptual design results in a large non-conventional airship. In this paper, the structural feasibility of a non-rigid large non-conventional airship is researched. Finite Element Analyses combined with a literature study have been conducted, aiming to elucidate the effects of size and non-conventional geometry on the envelope stresses. Such analysis reveal the challenges on finding weight-efficient solutions to control the envelope shape, as well as a linear stress increase with the size of the envelope as a consequence of the internal overpressure. Considering the findings, a new solution is proposed: the application of Tensairity beams as structural elements of the airship keel. Tensairity is a new lightweight structure based on the Tensegrity concept: it is based on the functional division of the existing elements, aiming to maximize its efficiency. A Tensairity beam is made of tension and compression elements connected by an air beam that stabilizes the system. In this paper, a large Tensairity torus withstanding air drag force has been numerically studied, aiming to deduce if the Tensairity concept can be applied in these new conditions. The main effects of larger dimensions and a torus-shaped structure have been characterized in order to design a preliminary Tensairity structure. The Tensairity structure has been compared to a HEA profile beam, concluding that the Tensairity principle is reproducible in the studied conditions. Moreover, an analysis of the influence of the air beam radius shows a significant decrease of the struts stress and of the beam deflection as the radius beam is increased. These results validate the possibility of applying Tensairity as an alternative solution for airships structure, although more research and optimization is needed to validate such hypothesis. © 2014 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Article
Based on the advantages of tension-string structures and inflatable membrane structures, this paper proposes a Tensairity arch and designs and builds a model for the structure. The mechanical response of the structure under a concentrated load is studied by carrying out static tests. From three aspects of the midspan deflection deformation, the strain of upper chord member and the tension of steel cable, this paper studies the influence of the internal inflation pressure, the tension of the lower chord steel cable, and the combinations of the steel cable on the bearing capacity of the structure. The results show that increasing the inflated air pressure to a certain extent can significantly improve structural stiffness, but compared with traditional spindle-shaped Tensairity, the prestress applied during the inflation process is not conducive to enhancing the structural load-bearing capacity. Changing the stress distribution of the upper chord member by tensioning the lower chord cable is beneficial to achieve a better material performance and weaken the adverse effects caused by the inflation of the airbag. The supplementary tension of the horizontal steel cable can improve the ultimate bearing capacity of the structure, thus contributing to the safety of the structure.
Article
A framework for simulating tethered wings for kite power is presented. The simulation tool contains a detailed aerodynamic model and a realistic tether model. With the aerodynamic tool, two different wings are analyzed regarding their efficiency. The aerodynamic efficiency of kites is determined with a parameter study showing the trends of the most important geometrical parameters. Those wings are manually flown in the simulator and the flight behavior is discussed. Finally, power cycles of a pumping system are simulated and controlled automatically and results are compared.
Article
Simple analytical models for a pumping cycle kite power system are presented. The theory of crosswind kite power is extended to include both the traction and retraction phase of a pumping cycle kite power system. Dimensionless force factors for the reel out and reel in phase are introduced which describe the efficiency of the system. The optimal reel out and reel in speed of the winch is derived where the cycle power becomes maximal. These optimal speeds are solely determined by the ratio of the force factors. Scenarios for wind speeds higher than the nominal wind speed are considered and power curves for the pumping cycle kite power system derived. The average annual power for a given wind distribution function allows to estimate the annual energy production of the pumping cycle kite power system. The role of the elevation angle of the tether is highlighted and a simple model to demonstrate the influence of the kite mass on the power output is discussed.
Article
Based on the mechanical behavior of the Tensairity, a spindle Tensairity structure model of 2.5 m span was designed and manufactured. Under two concentrated forces loading on the mid-span of the model, the deflection and the laws of internal force distribution of the model were investigated, and the influence of the internal air pressure on the static performance of the structure was studied. Through the analysis of the limit states for the structure, the fracture morphology and the failure mechanism were studied. Second, the refined spindle Tensairity finite element model was established by ANSYS. From initial state to inflated state and loaded state of the structure, the whole course numerical simulation was carried out, and the responses of the structure were compared with the results of the experiment. The results show that the results from numerical simulation and the experiment agree well. The displacements and the internal forces obtained from the two methods coincide basically. The test model reaches the limit state at the time of the concentrated force is added to 1.98 kN, and the corresponding failure mode is the local buckling damage of the upper chord member and the folding of the membrane at the end of the airbag.
Article
Designing robots for applications in space flight requires a different prioritization of design criteria than for systems operating on Earth. In this article, we argue that the field of soft robotics offers novel approaches meeting the specific requirements of space flight. We present one especially promising construction principle, so called Tensairity, in some detail. Tensairity, as the name suggests, takes ideas from Tensegrity, but uses inflatable structures instead of cables and struts. Soft robots pose substantial challenges with respect to control. One way to meet these challenges is given by the concept of morphological computation and control. Morphological computation can be loosely defined as the exploitation of the shape, material properties, and dynamics of a physical system to improve the efficiency of computation and to deal with systems for which it is difficult to construct a virtual representation using a kinematic model. We discuss fundamental aspects of morphological control and their relevance for space flight. Besides low weight, small consumption of space in the inactive state and advantageous properties with respect to intrinsic safety and energy consumption, we discuss how the blurring of the discrimination of hard- and software leads to control strategies that require only very little and very simple electronic circuitry (which is beneficial in an environment with high irradiation). Finally, we present a research strategy that bundles activities in space flight with research and development in medicine, especially for support systems for an aging population, that are faced with similar morphological computing challenges to astronauts. Such a combination meets the demands for research that is not only effective, but also efficient with respect to economic resources.
Conference Paper
View Video Presentation: https://doi.org/10.2514/6.2022-1514.vid A high altitude aerial platform called a "Mothership" is a large-scale tethered wing, designed to fly at 10 kilometers above the ground (AGL) or higher. Strong jet streams found at these operating altitudes present unique yet challenging opportunities to harvest wind energy. Additionally, a long endurance stationary vehicle could serve communications, provide atmospheric data, and provide payload transportation needs for commercial and disaster relief purposes. An inflatable baffled wing was conceived of as potentially viable for such an unconventional high altitude vehicle, providing sufficient performance attributes, with minimized weight. Inflatables are also compact and easy to transport, a positive feature. However, there are many technical challenges associated with fabricating such a textiles-based inflatable wing, including dynamics, controls, and structural and performance characteristics. A small scale wing prototype was developed and fabricated, and used for flight testing, and also to provide model input data for FEA analysis. This paper describes the design requirements, evaluation and selection of material and fabrication methods, and the performance and analysis of the authors’ prototype inflatable kite.
Article
Airships have the intrinsic advantages of Lighter-Than-Air (LTA) vehicles: minimal energy consumption and Vertical Take-Off and Landing (VTOL) characteristics. Due to these advantages, significant efforts are being taken in order to investigate new applications and technical improvements. More specifically, there is a renewed interest in large airships for heavy payload transportation and for stratospheric airships. The design of large airships is a big challenge, especially when considering the structural point of view, since big volumes imply high loads, and since light weight is a major requirement for this type of vehicles. In this context, a light-weight structure is proposed by applying the structural Tensairity concept. A Tensairity beam consists of a rigid air beam designed on the basis of complete functional separation of the different structural elements, allowing for a maximum optimization. In this paper, the justification of the feasibility of applying Tensairity components in airships is discussed based on two criteria. The first criterion is the justification of the need of a lightweight structure by a state of the art analysis and a study of the principal characteristics of the existing types of LTA vehicles structures. The second criterion is a preliminary technical analysis, which aims to clarify if the load bearing behavior of airships is suited for the application of the Tensairity concept. Moreover, the bases for the development of the concept for the LTA vehicles structures are established. The advantages and drawbacks of the traditional rigid airships structure in comparison with a non-rigid structure has been analyzed, which conclusion is that the use of a rigid structure is convenient for large airships, since it reduces significantly the stresses of the envelope, but at the same time decreases the payload efficiency due to the addition of the structure's weight. Moreover, the analysis of the load bearing behavior suggests the technical feasibility of applying Tensairity components, since airships have to withstand high bending moments and Tensairity structures are appropriate for withstanding such loads. Finally, the principal guidelines for defining the various load cases and for modeling Tensairity beams have been defined. In order to confirm the hypothesis of the suitability of Tensairity structures on airships, extensive research on design, analysis and optimization of Tensairity beam grids in typical airship loading conditions is needed.
Thesis
Full-text available
Dunnage bags are an inflatable dunnage variant, positioned and inflated between goods in multi-modal containers to restrain and protect the goods while in transit. This project endeavours to develop a simple method of generating new numerical prototypes for dunnage bags suitable for simulating operational loading of the bags. Previous research has produced a model that simulates the inflation of a paper dunnage bag using a simple pressure load. A dunnage bag reinforced with plain-woven polypropylene was chosen as the test case. Woven polypropylene is a highly non-linear, non-continuous, non-homogeneous material that requires specialised material models to simulate. A key aspect of this project was to develop a simple method for characterising woven-polypropylene and replicating it's response with material models native to LS-DYNA. The mechanical response of the plain-woven polypropylene was tested using a bi-axial tensile test device. The material response from physical testing was then mapped to two material models using the numerical optimiser LS-OPT. The response of the calibrated material models was found to correlate well with the measured response of the woven material. Dunnage bags are subjected to cyclic loading in operation. In order to capture the effects of compressing the contained gas, a gas inflation model was added to the model that calculates the pressure in the bag based on the Ideal Gas Law. A full bag model making use of the calibrated material models and the inflation model was subjected to a cycled boundary condition simulating loading and unloading of an inflated dunnage bag. The two prototype models captured the pressure drop in the bag due to material plastic deformation and the restraining force produced by the bag to within 10 %. The prototype models were also found suitable for predicting burst pressure in voids of arbitrary size and shape.
Research
Full-text available
Die Entwicklung und Bedeutung vollflexibler, seilgebundener Tragflächen ist seit der Jahrtausendwende stark vorangeschritten. Grund hierfür ist zum einen die quantitative Zunahme an weltweiten Institutionen, welche sich mit der Höhenwindenergienutzung (AWE) beschäftigen, und zum anderen die steigende Popularität des Kitesurfsports. Mit den bisherigen Entwicklungsmethoden konnte bereits ein hoher Reifegrad auf Produktebene erreicht werden, jedoch wurde dieser vorwiegend durch die empirische Variation der Schirmparameter realisiert. Messungen mit reproduzierbaren Steuereingaben unter gleichbleibenden Bedingungen konnten bisher nicht durchgeführt werden. Zunächst werden die zu messenden statischen und dynamischen Eigenschaften aufgestellt. Im Rahmen dieser Arbeit werden Eigenschaften als dynamisch bezeichnet, welche gegenüber variablen Steuereingaben oder Schirmpositionen ermittelt werden. Anhand dieser Eigenschaften erfolgt die methodische Prüfstandsentwicklung. Hierbei liegen die Schwerpunkte auf der konstanten Strömungserzeugung am Schirm, der Vermessung des gesamten Kitesystems zur realitätsnahen Messdatengenerierung sowie der Möglichkeit, wiederholbare, automatisierte Manöver einzuleiten. Durch diese Arbeit wird die objektive Messung ausgewählter Schirmeigenschaften hochflexibler seilgebundener Tragflächen ermöglicht. Die Messergebnisse können einerseits zur Weiterentwicklung und Charakterisierung dieser Tragflächen genutzt werden und andererseits können anhand der Ergebnisse Simulationsmodelle validiert und verbessert werden. Die ausgewählten dynamischen Eigenschaften können erfolgreich mit Hilfe des Manövers „lineares Powern“ bestimmt werden. Hierbei wird das Längenverhältnis zwischen Frontleinen und Steuerleinen automatisiert über einen definierten Weg abgefahren. Der Pilot kann Steuereingaben tätigen, um den Schirm in seiner Position zu halten. Dieses Manöver ermöglicht somit die Vermessung der Schirmeigenschaften gegenüber dem Längenverhältnis zwischen Front- und Steuerleinen. Weiter kann gezeigt werden, dass die entwickelte Messmethode dazu geeignet ist, grundlegende Schirmdesignkonzepte aufgrund ihrer gemessenen Eigenschaften, miteinander zu vergleichen. Auch subjektive Bewertungskriterien zur Charakterisierung von Kitesurfschirmen können objektiv bestätigt werden. Die vorliegende Arbeit kann somit einen entscheidenden Beitrag zur Evaluierung von Folgekonstruktionen und Simulationsmodellen vollflexibler, seilgebundener Tragflächen leisten. Since the turn of the millennium, the design and significance of highly flexible tethered airfoils has increased considerably. In particular, this has been attributed to the quantitative growth of global institutions involved in airborne wind energy (AWE) as well as the rising popularity of kitesurfing. While, existing design methods have proven useful in achieving a high degree of maturity on product level, this has primarily been accomplished by the empirical variation of wing parameters. Measurements, which include reproducible steering inputs, within the same conditions have not been carried out yet. In a first step, the static and dynamic properties that need to be measured are specified. In the scope of this thesis, airfoil properties are defined as dynamic, which are determined against variable control inputs or kite positions. Based on these properties, the methodical test bench design is carried out. In this context, the focus is on the constant airflow generation at the kite, the measurement of the entire kite system under realistic conditions, and the possibility to initiate repeatable, automated maneuvers. With the findings described in this thesis, an objective measurement of specific dynamic wing properties of highly flexible tethered airfoils will be facilitated. The measuring results are essential for the development and characterization of these airfoils as well as for the validation and improvement of simulation models. The selected dynamic properties are successfully determined by using the “Linear Power” maneuver. Hereby, the ratio between front lines and control lines is varied fully automated within a predefined length. At the same time, the pilot steering the kite can still perform control inputs to keep the kite in positon. This maneuver allows the measuring of the kite property depending on the length ratio between front and control lines. Furthermore, it was demonstrated that the method is suitable for comparing basic airfoil design concepts, based on the in-depth measurements of the kite properties. In addition, subjective evaluation criteria used for the characterization of surf kites were objectively confirmed. The thesis makes a decisive contribution to the evaluation of follow-up designs and simulation models of highly flexible tethered airfoils.
Article
Tethered wings that fly fast in a crosswind direction have the ability to highly concentrate the abundant wind power resource in medium and high altitudes, and promise to make this resource available to human needs with low material investment. This chapter introduces the main ideas behind airborne wind energy, attempts a classification of the basic concepts that are currently pursued, and discusses its physical foundations and fundamental limitations.
Article
Full-text available
Because o f its li ght wei ght, simple construction, and good aerodynamic performance, the Princeton sailwing may be a competitive alternative to con-ventional wings for many low-speed applications such as ultralight sailplanes, man-powered aircraft and high-performance hang gliders. The operational characteristics of the sailwing are discussed with some emphasis placed on the importance of the trailing-edge cable tension as it controls several aero-dynamic properties. The three-dimensional aerodynamic characteristics of eight different sailwing profile sections have been obtained from wind tunnel tests and the results compared to determine the magnitude of the aerodynamic penalties paid for various structural simplifications . For the sectional thickness ratios considered in this research, it is concluded that, while the basic double-membraned sailwing has exceptional aerodynamic performance, even superior for some applications to the conventional hardwing, any notable deviation from this configuration results in an unacceptably large performance penalty.
Article
Full-text available
In recent years the Departments of Defense has had a desire to tightly pack small Unmanned Aerial Vehicles (UAVs) in order to allow them to be launched via gun, by hand, or air dropped for reconnaissance or munitions delivery. Inflatable components enable compact packaging and rapid deployment on the ground or in flight, while minimizing system mass and complexity. Inflatable structures also provide UAVs with a significant amount of robustness as they can sustain hard landings without damage due to their inherent inflatable nature, in essence functioning as airbags. The combination of these two factors, compact packaging and damage tolerance, can be combined to provide UAVs that are easily transportable and cost effective. Numerous laboratory and flight tests have been performed to demonstrate the damage tolerance of inflatable wings. The survivability rate has remained at 100% beyond one hundred flight test impacts, and has been verified by similar laboratory testing. The resilience of the inflatable components manufactured from engineered materials is outstanding and tracks well with related inflatable structures such as the Pathfinder and MER airbags, which landed on the rocky surface of Mars. Inflatable wings have also demonstrated two aspects of morphing for UAVs or other flight platforms (such as airships). These are high aspect ratio changes via the deployment of inflatable tip extensions, and camber morphing for aerodynamic control. Inflatable wings with embedded actuation systems have been developed that are deployable and can easily be shape morphed to provide the required aerodynamic control for small UAVs. The flexible composite materials used in inflatable wings also allow for the inclusion of multi-functional elements to augment performance. Multi-functional elements for deployable wings include those that perform structural or aerodynamic functions, but are also used for functions such as aerodynamic control, power generation, power storage, and communication. Key tests conducted during this research and discussed herein include: rapid simultaneous wing deployment, gust and impact loading survivability tests, and wing shape vs. inflation pressure as characterized through wind tunnel testing. This paper discusses the various morphing concepts in detail and the subsequent development and testing of various components for UAVs. The design and fabrication of a small UAV with embedded actuation technology on the inflatable components is also detailed along with flight-test data.
Conference Paper
Full-text available
In this paper we present a challenging application of periodic optimal control. A kite that is towing a ship into a given target direction should fly optimal loops. We show how to find the maximum average tractive force by controlling the roll angle of the towing kite taking into account that the wind is increasing with the altitude over the sea. The optimal control problem for this highly nonlinear and unstable system has periodicity constraints, free initial values, and a free cycle duration. For its solution, we use MUSCOD-II, an optimal control package based on the direct multiple shooting method. Finally, we discuss the influence of an important design parameter, the effective glide ratio of the kite
Conference Paper
Full-text available
The paper describes the new concept Tensairity which can be used to significantly improve the load bearing capacity of inflatable wings. The basic principle of Tensairity is to use an inflatable structure to stabilize conventional compression and tension elements. So far, Tensairity has been mainly used in civil engineering application like roof structures and bridges. In this work, considerations to apply Tensairity to wing structures are given and the construction of two wing-like Tensairity kite prototypes is described. Test results on the Tensairity structure used in these kites are presented and compared to purely air inflated structures. Finally, the advantages of Tensairity wings are discussed and some application areas of these wings are suggested.
Article
Structural stabilization by a pressurized fluid is very common in nature, however hardly found in technology. Car tires, hot air balloons, airships and airhouses are among the few technical exceptions, which are stabilized by a compressed medium, typically air. Restricted by simple geometries and a very limited load bearing capacity these pneumatic structures could succeed only in very specialized applications. Nevertheless, prospective concepts ag has systematically investigated pneumatic structures during the last few years. As a major result, it was demonstrated that almost any shape can be made with pneumatic structures and that astonishing structures such as the pneumatic airplane Stingray can be realized even with low air pressure. On top of that, Airlight Ltd. in close collaboration with prospective concepts ag has recently developed the fundamental new structural concept Tensairity. The synergetic combination of an inflated structure with conventional structural elements such as cables and struts yields pneumatic light-weight structures with the load bearing capacity of steel girders. Thus, complex forms and high strength open up many new opportunities for pressure induced stability in technology. An overview of these recent developments is presented and the close relationship of pneumatic structures with biology is outlined.
Conference Paper
Deployable wing technology can offer many benefits to specific UAV missions, most importantly low-volume storage of the wings when the vehicle is not in-flight. Deployable wing designs enable aircraft to be more effective by providing larger numbers in volume restricted applications, such as air, submarine, or hand launches. As platforms become smaller, new avenues for deployable wings arise. This paper discusses issues related to deployable wing technology for small UAVs and some of the limitations for certain designs. In particular, the differences between rigid and inflatable solutions are discussed and example applications are presented. Like morphing aircraft technology, there is not a single solution for aircraft requiring deployable wings. The suitability of low-volume storage on an aircraft will be dependent on weight, span, storage requirements, and the flight envelope.
Article
Deployable wings are needed for a variety of applications such as extended range cargo delivery, lightweight portable aircraft and gun-launched vehicles. Inflatable structures provide a non-mechanical means for compact stowage and reliable deployment. This paper provides historical background on early examples of inflatable wings, including several early patents and the Goodyear Inflatoplane. A new approach to inflatable structures utilizes tubular spars manufactured by braiding high tenacity fibers over a thin gas barrier. Such structures can withstand high inflation pressures, which is the key to high strength before wrinkle onset. Reinforcement with high modulus fibers in the axial direction allows stiffness tailoring. The strength and stiffness equations for pressurized reinforced braided tubes are presented and discussed. These are considerably different than those found in the literature for woven fabric pressurized tubes. Examples are given of wing structures, wing deployment and actual flying configurations.
Article
This paper describes a concept for large-scale wind power production by means of aerodynamically efficient kites. Based on aircraft construction, these kites fly transverse to the wind at high speed. The lift produced at this speed is sufficient to both support the kite and generate power. The equations of motion are developed, and examples are presented. One version, based on the C-5A aircraft, results in 6.7 MW produced by a 10-m/s wind. Extrapolation to newer technology, which is more comparable to modern wind turbines, indicates the production of 45 MW from a single machine. The detailed calculations are validated by comparison of their results with simple analytical models. The methodology used here lays the foundation for the systematic study of power-producing kites.
Article
The new structural concept Tensairity® is a synergetic combination of cables, struts, membranes and low pressure compressed air, The role of the air and membrane is to pretension the cables and to stabilize the compression element against buckling. The new light weight structure has a variety of applications ranging from wide span roof structures to temporary bridges. Recent realizations of Tensairity as the roof of the parking garage in Montreux Switzerland rely on the spindle shape of the girders. First experimental investigations of a spindle shaped Tensairity girder under bending load are presented and compared to numerical results and some analytical results. Geometrical properties and simple approximation formulas for the surface area, the volume and the stresses in an inflated spindle are given.
Article
Tensairity is a lightweight structural concept comprising struts and cables stabilized by a textile membrane which is inflated by low pressurized air. This paper addresses the effect of fabric webs inside the membrane hull on the static response of spindle-shaped Tensairity columns to axial compression. Two full-scale spindle-shaped columns, one without and one with webs, were fabricated and tested. The columns were subjected to axial compressive loading for various levels of internal air pressure to quantify its effect on the global structural response. It was found that the stiffness and the load bearing capacity for both columns increased with increasing air pressure. The experimental results also revealed the benefits of including fabric webs in the spindle configuration in terms of axial stiffness and buckling load. Comparisons with an analytical solution and finite-element predictions showed good correlation for the axial stiffness in the case without webs. For the case with web deviations between predicted and experimental results indicated that structural detailing and imperfections in the manufacturing process strongly influence the performance of Tensairity columns with internal webs.
Article
Die Parkhauserweiterung für eine zentral gelegene Park-and-Rail-Station in Montreux, Schweiz, durch Luscher Architectes aus Lausanne und mit dem Ingenieurunternehmen Airlight aus Biasca, Schweiz, stellt die erste wichtige architektonische Anwendung des “Tensairity”-Patents dar. Dabei handelt es sich um eine synergetische Kombination aus Stahlelementen und einem pneumatischen Glasfasergewebe-Träger, die die Realisierung von neuen, innovativen, sehr leichten und trotzdem sehr widerstandsfähigen konstruktiven Formen ermöglicht. Tensairity Patent – A pneumatic tensile roof. A membrane roof covering a central railway station parking area in Montreux, Switzerland, by Luscher Architectes of Lausanne with engineering by Airlight of Biasca, Switzerland, involved the first significant architectural application of the “Tensairity” patent. The static combination of steel and pressurized fabric beams has brought about an effectively innovative structural form in terms of lightness and load resistance. The pneumatic beams filled with compressed air and the covering membrane are stabilize the steel structure with half the weight of a conventional roof.
Article
Recent shifts in tactical defense operations have led to a need for improved capabilities in Unmanned Aerial Vehicles (UAVs). Several vehicle types such as the Predator are currently operational, and numerous smaller specialized vehicles are under development. Many of the vehicles under development require the ability to stow their wings and control surfaces into very small volumes to permit gun launch or packaging into aircraft mounted aerial drop assemblies. One technology that has shown promise in achieving this goal is the inflatable wing. Inflatable wings have been demonstrated in many applications over the past five decades, including aircraft, UAVs, airships, and missile stabilization surfaces. Recent advancements in high strength fibers and rigidizable materials have enabled higher performance designs for modern application. The inclusion of "smart materials" has provided the opportunity to impart a multi-functional capability to inflatable wings. Such materials include electronic- textiles, which provide the potential for the integration of numerous functions directly into the structure of the wing such as shape modification for control and morphing, power generation and storage, antennas, and sensing.
Article
A study was conducted to develop a nonlinear feedback controller that stabilized the kite motion using a set of noisy measurements of the system. The study used numerical simulations to demonstrate the effectiveness of the controller for tracking power-generation trajectories. The study found that the loop was closed with the kite using feedback and nonlinear optimal control with a tether dynamic model. The study showed that the controller, combines a nonlinear outer loop, was followed by the system in response to changes in wind speed and direction. The updated reference trajectories were tracked using an inner-loop controller based on the time-varying linearized dynamics. The study found that the control of the kite was achieved under changing wind conditions using filtered measurements in the feedback loop.
Article
A very significant amount of wind energy is contained in the movements of air at high altitudes. A particular invention (Laddermill Patent Ned. 1004508. Nov. 1996 applications Europe and USA), named “laddermill”, is described that allows exploiting this energy using the winds up to possibly the tropopause. A “laddermill” is a self-supporting system that consists of an endless cable connected to a series of high-lifting wings or kites moving up in a linear fashion, combined with a series of low-lifting wings or kites going down. The cable drives an energy generator placed on the ground. Dutch measured wind statistics are presented that show the immense power source at high altitudes. Some general physical considerations are given for the laddermill. Three simulation programmes were developed independently by different institutions. The results give a good consistency of the laddermill shape and power production. Design solutions are indicated for the wing attitude control and stability and a concept for the ground station is presented providing wing and cable handling. Adaptation to weather is given by flexible retrieval and deployment capability. Comparisons are shown with existing wind turbines. An operational model and related cost model have been made that include an operation strategy that optimises the economical effectiveness of the wings, cable and ground station. This operational model has been applied to the actual wind measurements over a period of 10 years. The results show, in comparison to the existing horizontal axes wind turbines, (i) a potential for significantly larger amount of wind energy production and (ii) an indication that this can be done at significantly lower cost. The public acceptance has been assessed, resulting in a positive perception of elegance of the low speed and silent movements combined with the excitement from reaching impressive altitudes. Safety and potential aviation interference are also addressed.
Article
Tensairity is a new lightweight structural concept consisting of struts and cables stabilized by a textile membrane, which is inflated by low pressurized air. In order to estimate the potential of Tensairity beams towards applications including axial compressive loads, full-scale compression experiments were conducted on a simply-supported spindle shaped Tensairity column. The column was subjected to axial compressive loading for various levels of internal air-pressure in order to quantify its effect on local and global response, and it was found that the axial stiffness of the column increases with air-pressure and eventually reaches a plateau. Displacements were measured in several positions along the span, whereas axial forces were experimentally determined by strain gauges measurements. The experimental results were compared to finite element and analytical predictions, yielding good correlation for low air-pressure levels, whereas for higher ones, local imperfections led to significant deviations. Comparisons of the Tensairity column to similar truss-type structures with comparable stiffness revealed the superiority of the concept in terms of transportation volume and in-situ deployment.
The new structural concept Tensairity: Basic principles
  • R H Luchsinger
  • A Pedretti
  • P Steingruber
  • M Pedretti
R.H. Luchsinger, A. Pedretti, P. Steingruber, M. Pedretti, The new structural concept Tensairity: Basic principles, in: Progress in Structural Engineering, Me-chanics and Computations, A.A. Balkema Publishers, London, 2004.
Design limitations of deployable wings for small low altitude UAVs, in: 47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition
  • J D Jacob
  • S W Smith
J.D. Jacob, S.W. Smith, Design limitations of deployable wings for small low altitude UAVs, in: 47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition, Orlando, Florida, AIAA 2009-1291, 2009.
Utility Mk1 demonstrated, Flight Magazine
  • M L Airoplane
Airoplane, the Inflatable-wing M.L. Utility Mk1 demonstrated, Flight Magazine (1957) 751–752.
Power kites for wind energy production
  • Canale
The new structural concept Tensairity: Basic principles
  • Luchsinger