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Modelling of the Viscoelastic Relaxation of a Stowed Telescope StarshadeRaghu, Rahul 01 January 2024 (has links) (PDF)
The Habitable Worlds Telescope Starshade is an occulting disk that orbits in tandem with a telescope that occludes and diffuses the light from stars to observe the relatively dim exoplanets in orbit around them. It achieves this in part with tailored petals that diffuse light to soften the light from the star. Due to the relative sizes of the star and the planet, NASA considers the shape stability of the Starshade's petals to be a Key Technology Gap. The Starshade is developed to be a deployable composite structure that folds on itself to fit within modern rockets. Due to the nature of satellite launches, Starshade will sit in the stowed configuration for multiple years, during which the viscoelastic material properties of the materials that consist of the Starshade will deform in the structure and take an unknown time to recover fully. Thus, the need arises to understand Starshade's viscoelastic behavior through recovery after fully deploying. Starshade's Petals consists of a sandwich composite structure where multiple composite edges are joined together using a significantly less stiff adhesive that is comparably thicker than the individual Carbon Fiber Reinforced Plastic layers that consist of the composite edge. This could cause traditional modeling approaches to not fully capture the potential modes of relaxation in the structure, so a diagnostic model, referred to as the Phoenix Edge, is developed to compare different modeling techniques. After modeling techniques are validated against each other, they are applied to the NI2 Petal to predict the viscoelastic structural response through 6 months of recovery after three years of stowage in a furled configuration.
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Thin-Ply Laminate Viscoelasticity and Dimensional Stability in Deployable Space StructuresYapa Hamillage, Milinda Madhusanka Yapa 01 January 2023 (has links) (PDF)
Thin-ply composite materials display remarkable versatility and hold great promise for applications in the space industry. They are characterized by exceptional attributes such as a high strength-to-weight ratio, fatigue resistance, and the ability to conform to high curvatures without failure. This study investigates the behavior of thin-ply composite materials and structures, with a particular emphasis on their relevance to deployable space applications. Deployable structures such as solar sails, are large structures that are designed to be compactly folded into small volumes to fit inside the spacecraft for the purpose of carrying them to space. These structures utilize the strain energy during folding, to facilitate the deployment sequence and attain the intended original configuration of the structure. However, the viscoelastic nature of the composite material leads to a reduction of strain energy over the storage period, leading to shape inaccuracies after deployment. Our research includes an in-depth analysis of the viscoelastic properties of the composite material and the behavior of structures following folding and subsequent deployment. The viscoelastic mechanical properties of the materials were assessed through a numerical multi-scale homogenization approach. We examined thin-ply laminates with varying orientations and ply arrangements and conducted experimental studies to validate the numerical models. We subsequently incorporated the viscoelastic properties of the laminates into the simulation of deployable structures. The laminate properties were evaluated both at the ply level and at the laminate level. Numerical simulations were conducted to study the behavior of a composite boom during folding, stowage, deployment, and subsequent shape recovery. Our research extended to characterizing the composite material based on available test data, as well as examining the stowage and recovery behavior of a structure constructed from unidirectional composites.
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"Don't Leave the Pad Without It": Using Deployable Assets to Conduct Pre-Launch and On-Orbit TestingMorimoto, Todd, Sargent, Cliff 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / When hundreds of millions of dollars are invested in building, launching, and command/control of modern military space systems, the developers and operators need assurance that when their system achieves orbit, it will be able to "talk" with the ground network, exchanging commands, telemetry and ranging signals. Furthermore, prior to launch they need proof of compatibility with the ground data systems, showing that operational ground-based crypto keys, database parameters, and processing software are in-fact compatible with the spacecraft. This paper describes Air Force Materiel Command (AFMC), Space & Missile Center (SMC) Detachment 2's four classes of deployable test assets, emphasizing deployable's contribution to successful on-orbit performance. With not only the huge dollar investment, but even more important, the ability to execute a vital test or operational mission riding on compatibility, and launch vehicle and on-orbit test and evaluation operations the watchwords are "Don't leave the pad without it."
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Deployable Tensegrity Structures for Space ApplicationsTibert, Gunnar January 2002 (has links)
QC 20100901
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Ne Design Methods For Polyhedral LinkagesKiper, Gokhan 01 September 2006 (has links) (PDF)
This thesis analyses the existing types of polyhedral linkages and presents new linkage types for resizing polyhedral shapes. First, the transformation characteristics, most specifically, magnification performances of existing polyhedral linkages are given. Then, methods for synthesizing single degree-of-freedom planar polygonal linkages are described. The polygonal linkages synthesized are used as faces of polyhedral linkages. Next, the derivation of some of the existing linkages using the method given is presented. Finally, some designs of cover panels for the linkages are given. The Cardan Motion is the key point in both analyses of existing linkages and synthesis of new linkages.
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Compliant shell mechanismsSeereeram, Videsh Ramjas January 2012 (has links)
No description available.
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Thin-walled composite deployable booms with tape-spring hingesMallikarachchi, H. M. Yasitha Chinthaka January 2011 (has links)
Deployable structures made from ultra-thin composite materials can be folded elastically and are able to self-deploy by releasing the stored strain energy. Their lightness, low cost due to smaller number of components, and friction insensitive behaviour are key attractions for space applications. This dissertation presents a design methodology for lightweight composite booms with multiple tape-spring hinges. The whole process of folding and deployment of the tape-spring hinges under both quasi-static and dynamic loading has been captured in detail through finite element simulations, starting from a micro-mechanical model of the laminate based on the measured geometry and elastic properties of the woven tows. A stress-resultant based six-dimensional failure criterion has been developed for checking if the structure would be damaged. A detailed study of the quasi-static folding and deployment of a tape-spring hinge made from a two-ply plain-weave laminate of carbon-fibre reinforced plastic has been carried out. A particular version of this hinge was constructed and its moment-rotation profile during quasi-static deployment was measured. Folding and deployment simulations of the tape-spring hinge were carried out with the commercial finite element package Abaqus/Explicit, starting from the as-built, unstrained structure. The folding simulation includes the effects of pinching the hinge in the middle to reduce the peak moment required to fold it. The deployment simulation fully captures both the steady-state moment part of the deployment and the final snap back to the deployed configuration. An alternative simulation without pinching the hinge provides an estimate of the maximum moment that could be carried by the hinge during operation. This moment is about double the snap-back moment for the particular hinge design that was considered. The dynamic deployment of a tape-spring hinge boom has been studied both experimentally and by means of detailed finite-element simulations. It has been shown that the deployment of the boom can be divided into three phases: deployment; latching, which may involve buckling of the tape springs and large rotations of the boom; and vibration of the boom in the latched configuration. The second phase is the most critical as the boom can fold backwards and hence interfere with other spacecraft components. A geometric optimisation study was carried out by parameterising the slot geometry in terms of slot length, width and end circle diameter. The stress-resultant based failure criterion was then used to analyse the safety of the structure. The optimisation study was focused on finding a hinge design that can be folded 180 degrees with the shortest possible slot length. Simulations have shown that the strains can be significantly reduced by allowing the end cross-sections to deform freely. Based on the simulations a failure-critical design and a failure-safe design were selected and experimentally verified. The failure-safe optimised design is six times stiffer in torsion, twice stiffer axially and stores two and a half times more strain energy than the previously considered design. Finally, an example of designing a 1 m long self-deployable boom that could be folded around a spacecraft has been presented. The safety of this two-hinge boom has been evaluated during both stowage and dynamic deployment. A safe design that latches without any overshoot was selected and validated by a dynamic deployment experiment.
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Etude de structures légères déployables pour applications spatiales / Study of deployable lightweight structures for space applicationsMorterolle, Sébastien 18 October 2011 (has links)
Les besoins croissants en moyens de télécommunication nécessitent le développement de grands réflecteurs spatiaux paraboliques. Un nouveau concept d'architecture d'antenne déployable est ainsi proposé en partenariat avec le CNES. La conception de son ossature repose sur une revue de solutions pour faire appel à des mécanismes de ciseau associés à des articulations flexibles. Des modélisations numériques par éléments finis sont d'abord développées pour simuler le déploiement par restitution de l'énergie emmagasinée dans ces articulations lors du pliage. Un démonstrateur expérimental avec un système de compensation gravitaire est ensuite réalisé. Des essais et mesures sont effectués pour caractériser son comportement en statique et dynamique puis sont comparés avec les résultats issus des simulations. La mise en forme de la surface réflectrice par un réseau de câbles est étudiée par la suite. Une méthode innovante de recherche de forme permettant d'obtenir un réseau parabolique en tension uniforme est alors proposée. Elle est appliquée à différentes typologies de réseaux et l'erreur de surface résultant de sa facettisation est évaluée. Le procédé d'accrochage de ce réseau sur l'ossature de l'antenne est également traité. / The growing needs in telecommunications require the development of large parabolic reflectors. A new conceptual design for the architecture of a deployable antenna is therefore proposed in partnership with the CNES. The design of its framework is based on a review of solutions which leads to scissor mechanisms associated with flexible joints. Numerical modelings with finite elements are first developed to simulate the deployment by the release of the energy stored in the joints after the folding. An experimental prototype with a gravity compensation device is then realized. Tests and measurements are performed to characterize the static and dynamic behavior and compared with the results of simulations. Shaping of the reflective surface by a net of cables is then studied. A new form-finding method for obtaining a net with a uniform tension is then proposed. It is applied to different parabolic typologies of nets and the error due to surface faceting is evaluated. The process of net attachment on the antenna rim structure is also treated.
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Vibration Modal Analysis of a Deployable Boom Integrated to a CubeSat / Modalanalys av en utfällbar bom på en kubisk satellitShepenkov, Valeriy January 2013 (has links)
CubeSat or Cubic Satellite is an effective method to study the space aroundthe Earth thanks to its low cost, easy maintenance and short lead time. However, a great challenge of small satellites lies in achieving technicaland scientific requirements during the design stage. In the present workprimary focus is given to dynamic characterization of the deployable tapespringboom in order to verify and study the boom deployment dynamiceffects on the satellite. The deployed boom dynamic characteristics werestudied through simulations and experimental testing. The gravity offloadingsystem was used to simulate weightlessness environment in theexperimental testing and simulations showed that the deployment of thesystem influence the results in a different way depending on the vibrationmode shape. / En CubeSat eller kubisk satellit är effektivt för att studera rymden runtjorden på grund av dess låga kostnad, enkla underhåll och korta ledtid. Enstor utmaningen i utformningen av små satelliter är att uppnå de tekniskaoch vetenskapliga kraven. Detta arbete har analyserat de dynamiska egenskapernahos en utfällbar band-fjäder bom i syfte att verifera och för attstudera bommens utfällningsdynamiska effekter på satellitens bana och attityd.Den utfällda bommens dynamiska egenskaper har studerats genomsimuleringar och experimentella tester. Ett tyngdkraftskompenserande systemhar använts för att simulera tyngdlöshet i de experimentella testernaoch simuleringar visar att utformningen av detta system påverkar resultatenolika beroende på svängingsmodens form.
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[pt] COMPORTAMENTO NÃO LINEAR E INSTABILIDADE DE ARCOS AJUSTÁVEIS / [en] NONLINEAR BEHAVIOR AND INSTABILITY OF DEPLOYABLE ARCHESANA BEATRIZ GIMENES BARCELLOS 23 March 2021 (has links)
[pt] As estruturas ajustáveis ou dobráveis (deployable structures) consistem em um grupo de estruturas capazes de modificar sua forma e volume para atender a uma variedade de aplicações. Geralmente, são estruturas pré-fabricadas compostas por barras retas ou curvas unidas por meio de articulações que permitem que se movimentem para formar um arranjo compacto e se desdobrem em formas estruturais de grande porte. Essas estruturas atuam como mecanismos durante sua implantação e se tornam estruturas capazes de suportar cargas externas durante a fase de serviço. Além disso, elas devem ser leves e compactas a fim de serem facilmente transportadas e simples e rápidas de montar. Todas essas restrições
dificultam a escolha dos melhores parâmetros que levem ao menor peso, maior rigidez e que permitam à estrutura desempenhar suas duas funcionalidades e garantir sua reutilização. Entre os tipos de estruturas dobráveis, os elementos pantográficos (tesouras) têm despertado grande interesse de engenheiros e
arquitetos nos últimos anos. Este estudo avalia o comportamento não linear geométrico de arcos planos constituídos por dois tipos clássicos de elementos pantográficos: polar e translacional. Para isso, uma análise geométrica não linear detalhada é conduzida por meio de software de elemento finito elaborado com formulação corrotacional, a fim de avaliar a influência dos parâmetros geométricos da estrutura, como o tipo de elemento patográfico, o tipo de apoio e número de elementos no comportamento não linear e na estabilidade da estrutura. Os resultados obtidos por nossas análises revelam, na maioria dos casos, um
comportamento eminentemente não linear característico de arcos esbeltos, com o caminho de equilíbrio exibindo vários pontos limites de carga e deslocamento, onde podem ocorrer saltos para configurações remotas e indesejáveis. Com base nestes resultadods, a influência dos parâmetros do sistema na capacidade de carga do arco é quantificada. / [en] Deployable structures consist of a group of structures capable of modifying their shape and volume in order to meet a range of conditions and needs. They are usually prefabricated structures consisting of straight or curved bars linked together in a compact bundle, which can then be unfolded into large-span, load bearing
structural shapes. These structures have dual functionality since they act as mechanisms during its deployment and become immovable structures capable of supporting external loads during the service phase. In addition, they should be lightweight and compact to be easily transported and simple and quick to deploy. All these restrictions make it difficult to choose the best parameters regarding the shape and material of the structure, since many analyzes must be performed in order to find parameters that give lowest weight, highest stiffness, and that allow the structure to perform its two functions and ensure its reuse. Among the types of folding structure, those made of pantographic elements (scissors) have attracted great interest from engineers and architects in recent years. This study evaluates the
geometric nonlinear behavior of plane arches constituted by two classic type of pantographic element, namely: polar and translational. For this, a detailed nonlinear geometrical analysis is conducted through tailored corotational finite element software in order to evaluate the influence of the structure s geometrical
parameters, type of scissor units and supports on the nonlinear behavior and stability of the structure. The results obtained by our analyzes reveal, in most cases, a characteristic non-linear behavior of these structures with the nonlinear equilibrium path exhibiting several load and displacement limit points where jumps to remote and undesirable configurations may occur. Based on them, the influence of system parameters on the load carrying capacity of the arch is quantified.
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