Deformation Of Sail Research Articles

Study Membrane Solarelasticity Using a Wave Model and a Corpuscular Model of Light

The difference between solarelastic interaction and aeroelastic interaction is illustrated from the perspective of external forces. Membrane solarelastic responses of the solar cell and solar sail are studied through a wave model and a corpuscular model of light, respectively, where the light intensity and phase are considered in the wave model to calculate the solar radiation pressure but the phase of light is neglected in the corpuscular model. The effects of the membrane optical properties, the thickness, and the size on the solarelastic flutter instability are investigated. The solar radiation pressure is divided into a part depending on the sail deformation and a part independent of sail deformation to investigate their respective influences. The results show that the former terms result in membrane flutter and the latter term results in membrane static deflection. A comparison is conducted between the wave model and the corpuscular model on the flutter boundaries and membrane responses. The membrane reflectivity is coupled with membrane stiffness by the membrane thickness in the wave model, but it is uncoupled in the corpuscular model. Therefore, the wave model has an advantage over the corpuscular model when evaluating the thickness effect of membrane reflectivity.

Analysis of the solar sail deformation based on the point cloud method

The deformation of the solar-sail membrane is an important factor for causing inaccuracies in the solar-sail missions. This paper describes the solar sail under deformation by using a new modelling technique based on point cloud and triangular mesh generation. Two types of deformation, stemming from wrinkling and billowing, are modelled. The changes in the solar radiation pressure force and the moment caused by deformation are calculated and compared to the ideal non-deformed case. The heliocentric spiral trajectory and the orbital angular momentum reversal trajectory are taken as examples to quantify the influence of the deformation from an orbit point of view. Additionally, point cloud simplification, based on the normal vector and bounding box, is utilized to simplify the original deformed-sail model. It involves a reasonable reduction and renewal of the points in the model considering the variation of surface curvature. The simplification and its modelling accuracy are numerically investigated as well as computational efficiency.

Attitude Control of a Flexible Solar Sail in Low Earth Orbit

Launching solar sails to low Earth orbit can provide cheap and frequent opportunities for test missions, orbit raising from low Earth orbit, or deorbiting space debris. This Paper considers the problem of attitude dynamics and control of a flexible solar sail under solar radiation pressure, aerodynamic forces, and gravity gradient torque. A geometrically nonlinear finite element method was used to study the effects of solar radiation pressure and aerodynamic forces on a flexible membrane, including the deformation-induced disturbance torque and changes of center of pressure. Then, an analytical method was applied to estimate the deformation of the membrane, and consequently the generated disturbance torque. The results showed that the analytical method could estimate the sail deformation very accurately. The problem of controllability of a sliding mass control mechanism in low Earth orbit was studied, and the controllable attitude regions were defined according to the mass of the sliding masses. A robust servomechanism linear quadratic regulator optimal control approach was applied to control the attitude of a flexible sail in low Earth orbit under the disturbance torques. The simulation results showed the efficacy and robustness of the controller in dealing with deformation-induced torques during orbit raising and deorbiting.

Thermal-structural analysis of a square solar sail

The aim of this work is to improve an efficient methodology, recently developed to study the structural response of a classical square solar sails in free flight, under the action of the solar radiation pressure. The new approach models the effect of thermal loads acting on the sail's reflective surface. In particular, a square solar sail with a side length of 20m at 1au distance from the Sun is analyzed for different values of incidence and clock angles. The thermal-structural analyses are carried out under the assumption that the stress-displacement solution depends on the temperature field, but there is no inverse dependency. The thermal loads, for some attitude conditions, are shown to have remarkable effects on the sail deformation.

Correction and adjusting for the deformation on solar sail

A research on structural deformation of solar sail was presented. Nonlinear deformation of the sail was discussed, which will cause an additional devastating torque because of the shifting of the center of mass (CM). Finite-element analysis (FEA) method was carried out. In the computation, a correction was brought in, and a gradually increasing load method was presented. A more accurate membrane deformation result was obtained, and the photons pressure on the membrane was corrected. In purpose to guarantee the control ability in the long mission, a lifting mechanism is developed to adjust the large deformation. The lifting motion and result are verified by Abaqus. The research can be used in the solar sail controlling, where a large deformation may occur and an additional torque will disturb the controlling.

Fluid-structure interaction analysis of deformation of sail of 30-foot yacht

Most yacht sails are made of thin fabric, and they have a cambered shape to generate lift force; however, their shape can be easily deformed by wind pressure. Deformation of the sail shape changes the flow characteristics over the sail, which in turn further deforms the sail shape. Therefore, fluid-structure interaction (FSI) analysis is applied for the precise evaluation or optimization of the sail design. In this study, fluid flow analyses are performed for the main sail of a 30-foot yacht, and the results are applied to loading conditions for structural analyses. By applying the supporting forces from the rig, such as the mast and boom-end outhaul, as boundary conditions for structural analysis, the deformed sail shape is identified. Both the flow analyses and the structural analyses are iteratively carried out for the deformed sail shape. A comparison of the flow characteristics and surface pressures over the deformed sail shape with those over the initial shape shows that a considerable difference exists between the two and that FSI analysis is suitable for application to sail design.

Fluid-structure interaction analysis of deformation of sail of 30-foot yacht

Most yacht sails are made of thin fabric, and they have a cambered shape to generate lift force; however, their shape can be easily deformed by wind pressure. Deformation of the sail shape changes the flow characteristics over the sail, which in turn further deforms the sail shape. Therefore, fluid-structure interaction (FSI) analysis is applied for the precise evaluation or optimization of the sail design. In this study, fluid flow analyses are performed for the main sail of a 30-foot yacht, and the results are applied to loading conditions for structural analyses. By applying the supporting forces from the rig, such as the mast and boom-end outhaul, as boundary conditions for structural analysis, the deformed sail shape is identified. Both the flow analyses and the structural analyses are iteratively carried out for the deformed sail shape. A comparison of the flow characteristics and surface pressures over the deformed sail shape with those over the initial shape shows that a considerable difference exists between the two and that FSI analysis is suitable for application to sail design.

단순형태 세일의 변형에 대한 유체-구조 연성 해석

Since most of yacht sails are made of thin fabric, they form cambered sail shape that can efficiently generate lift power by aerodynamic interaction and by external force delivered from supporting structures such as mast and boom. When the incident flow and external force alter in terms of volume or condition, the shape of sail also change. This deformation in shape has impact on the peripheral flow and aerodynamic interaction of the sail, and thus it is related to the deformation of the sail in shape again. Therefore, the precise optimization of aerodynamic performance of sail requires fluid-structure interaction (FSI) analysis. In this study, the simplified sail without camber was under experiment for one-way FSI that uses the result of flow analysis to the structural analysis as load condition in an attempt to fluid-structure interaction phenomenon. To confirm the validity of the analytical methods and the reliability of numerical computation, the difference in deformation by the number of finite element was compared. This study reproduced the boundary conditions that sail could have by rigs such as mast and boom and looked into the deformation of sail. Sail has non-linear deformation such as wrinkles because it is made of a thin fabric material. Thus non-linear structural analysis was conducted and the results were compared with those of analysis on elastic material.

Solar sail elastic displacement effects on interplanetary trajectories

Space agencies are paying greater attention to solar sail technologies and missions. Actually, one of the most demanding issues when considering solar sailing is to assess the sail deformation as well as the following trajectory modifications. The main purpose of this paper is to show the order of accuracy that can be reached when coupling structural and dynamical behavior of a solar sail. Based on the application of the Finite Element Method, the deformations affecting the large structure of the sail, up to the second order of accuracy, are estimated, together with the real-time updated thrust vector according to such deformations. The new thrust vector, evaluated for an Earth–Venus mission, allows one to find a more realistic sailcraft trajectory. The results obtained show a change in the thrust's magnitude with a not negligible variation of the sailcraft trajectory with respect to the undeformed case. Another issue deserving particular attention concerns solar sail deployment. Both structural and dynamical behavior affecting a solar sail's performance will be analyzed even in the event of partial deployment. The results obtained show the importance of the right sizing of the attitude control, which may not be able to compensate such a failure and what strategies could be used to save the mission including the need for a new mission analysis.

A curved surface solar radiation pressure force model for solar sail deformation

A precise force model is of vital importance for dynamics and control of solar sails. Among various factors, deviations from the ideal flat sails, elastic deformations of the sails, are really important as most solar sails are large flexible membranes. In this study, the deformed sails are modeled as smooth curved surfaces and a general total force model (GTFM) for the deformed sails is proposed. Various simplified versions of this GTFM are also derived for the symmetric deformation cases. Furthermore, differences between the ideal force models and our precise GTFM are investigated. The numerical results demonstrate that both the previous ideal reflected model and flat optical model are not as satisfactory as claimed before, by contrast with the actual dynamics from the GTFM. Thus this work paves the way for sail craft’s precise navigation where exact forces are needed.

변형을 고려한 요트 세일의 2차원 단면 해석

Although a yacht sails operate with large displacement due to very thin thickness, many studies for flow around yacht sails have not considered the sail deformation. The sail deformation not only caused a change in the center of effect(CE) on the sail but also a change in the thrust of the sail. The change of the CE and thrust affects the center of lateral resistance(CLR) and side forces of the hull, and the balance of the yacht. These changes affect the motion of the yacht which changes the velocity of the yacht. Thus, when analyzing the flow around yacht sails, the sail deformation should be considered. In the present study, fluid-structure-interaction(FSI) analysis of a two dimensional section of yacht sails was performed to consider the effects of sail deformation on the lift and drag performance. FSI and moving mesh methods were studied. Computational methods were verified using benchmark test cases such as the flow around horizontal and vertical cantilever beams. Shape deformation, pressure distribution, lift forces and separation flow were compared for both rigid and deformable sail.

Can Solar Sails Flutter?

I N A widely cited report, MacNeal [1] has pointed out the advantages of a heliogyro, a solar sail that rotates and responds in ways similar to a helicopter blade, with the driving force being the solar pressure, as distinct from the aerodynamic pressure of more conventional rotorcraft. In this brief Note we consider the possible interaction between the deformation of the solar sail and the solar pressure. The solar pressure acts normal to the surface of the sail; thus, as the sail deforms, the direction of the solar pressure changes. This provides an opportunity for feedback between the loading of the solar pressure and the deformation of the sail. Indeed, as is shown implicitly by MacNeal [1] andmore explicitly here, for small elastic deformations of the sail, the solar-pressure-loading/solar-deformation relationship has essentially the same mathematical form as the aerodynamic-loading/ elastic-structural-deflection relationship for (two-dimensional, static Ackeret) supersonic flow aerodynamic theory. This suggests that many of the known methods and, to some extent, the known results from aeroelasticitymay be immediately adapted to the analysis of the solar sail. In particular, solar sails have the potential to undergo flutter.

Finite Element Modeling of Sail Deformation Under Solar Radiation Pressure

Anumerical structural model of a thin-film sail that simulates the deformation caused by solar-radiation pressure is developed, using a geometrically nonlinear finite element method (FEM). By using the finite element presented in this study, the force and moment exerted on an arbitrarily shaped solar sail subjected to solar pressure can be calculated accurately. In addition, it is shown that the sail deformation due to a solar-pressure load can be approximated by the deformation caused by the corresponding uniform gas-pressure load. This finding will significantly simplify analyses to improve attitude controller design as well as structural design of sailcraft, because commercially available FEM software can be used for the analyses.

Application of a non-convex model of fabric deformations to sail cut analysis

Abstract In this paper, we present a computer model based on an elastic string network representation for sail deformation. The equilibrium equation for this model is written in the form of a minimization problem. The latter is non-convex because of the unilateral-stress behaviour of strings. The method of deconvexification has to be used in order to obtain an equivalent problem which is easier to solve. The resulting model is applied to sail cut design problems: bi- and tri-radial cut plans are compared, as well as variations of the elasticity modulus in warp and weft directions. The results are found to be very similar to what is usually observed on actual sail boats.