Solar Sail Research Articles

Light-Propelled Super-Hydrophobic Sponge Motor and its Application in Oil-Water Separation.

Self-propelled separation materials, that is, motor, are one of the keys to realizing smart oil-water separation. Although three-dimensional sponges such as commercial melamine sponge (MS) exhibit excellent oil-water separation ability, they cannot move by themselves on water. Aiming at solving this problem, a polydimethylsiloxane (PDMS) and molybdenum disulfide (MoS2) modified MS motor (PDMS@MS/MoS2) with an asymmetric multilayer structure was prepared, in which the photothermal layer MoS2 provided the propelling force for the motor under infrared light irradiation, and the middle layer PDMS was used as the superhydrophobic modified agent and adhesive agent between commercial MS and MoS2 powder. PDMS coated MS (PDMS@MS) as the superhydrophobic layer showed good superhydrophobic ability (153.1°) and oil-water separation capacity (52.33 g/g to liquid paraffin). Furthermore, the introduction of MoS2 made the speed of the sponge motor reach 8.27 mm s-1 with a removal quantity of 12.20 g/g for cyclohexane. After recycling 8 times, the contact angle, cyclohexane capturing amount, and average velocity of the motor were 150.3°, 11.40 g/g, and 8.41 mm/s, respectively. Meanwhile, PDMS@MS/MoS2 kept a similar light-propelling velocity (∼8 mm) at different pH values and in simulated seawater, demonstrating that the light-propelling motor possessed a good cycle and practical performance, which provides a possibility for the directional light propulsion of a sponge motor in oil-water separation.

Solar Sail Transfer Trajectory Design for Comet 29P/Schwassmann–Wachmann 1 Rendezvous

The goal of this paper is to analyze the optimal transfer towards the periodic comet 29P/Schwassmann–Wachmann 1 of a solar sail-based spacecraft. This periodic and active comet is an interesting and still unexplored small body that has been regarded as an object of the Centaurs group. In this work, a classical (heliocentric) orbit-to-orbit transfer is studied from an optimal viewpoint, by finding the spacecraft trajectories that minimize the flight time for a given value of the solar sail characteristic acceleration, that is, the typical performance parameter of a photonic sail. In particular, the optimal Earth–comet transfer is studied both in a typical three-dimensional mission scenario and with a simplified two-dimensional approach, whose aim is to rapidly obtain an accurate estimation of the minimum flight time with a reduced computation cost. The numerical simulations illustrate the mission performance, in terms of the characteristics of the rapid transfer trajectory, as a function of the typical propulsive parameter and the solar sail thrust model.

Quantum Inspired Broadband Photonic Absorber: Potential Application as Solar Sail along with Mobility Analysis

Electromagnetic wideband absorption is still perceived as a critical and formidable challenge to address with an unambiguous photonic absorber. Subwavelength metamaterial (MM) unit cells with unique and controlled features have recently gained considerable interest. However, meta‐atoms, generated using a quantum‐inspired pattern distribution, are underwhelming in existing literature to design photonic absorbers and their potential application to manufacture solar sails is still quite uncommon. In this article, to create a flexible, polarization‐insensitive, ultrathin, and broadband MM absorber, quantum interference pattern‐inspired design is utilized. Herein, a novel approach to fabricating solar sails for the space exploration incorporates the proposed broadband photonic absorber rather than conventional reflectors. The quantum‐inspired meta‐absorber (QIMA) exhibits an absorption of over 91% for the visible domain, i.e., 380–800 nm under a conventional plane‐polarized source. It is shown in the study that broadband absorbers are almost equivalent to excellent reflectors to design the solar sails in terms of the time‐averaged force calculated by utilizing the Maxwell stress tensor method. Thus, the QIMA has the potential to be a viable alternative to reflectors in the design of futuristic solar sails for space exploration. The interference theory model is also utilized to assure the dependability of calculated data, and additionally, the standard AM1.5 solar spectrum is utilized to demonstrate the QIMA's solar‐harvesting potentiality.

A Station-Keeping Control Strategy for a Symmetrical Spacecraft Utilizing Hybrid Low-Thrust Propulsion in the Heliocentric Displaced Orbit

The solar sail spacecraft utilizing a hybrid approach of solar sail and solar electric propulsion in the heliocentric displaced orbit is affected by external disturbances, internal unmodeled dynamics, initial injection errors, and input saturation. To solve the station-keeping control problem under such complex conditions, an adaptive control strategy is proposed. First, the dynamical equations of the spacecraft utilizing hybrid low-thrust propulsion in the cylindrical coordinate system are derived. Second, the combined disturbance acceleration introduced by external disturbances and internal unmodeled dynamics is constructed, and a radial basis function neural network estimator is designed to estimate it online in real time. Third, an adaptive high-performance station-keeping controller based on an improved integral sliding surface and multivariate super-twisting sliding mode approaching law is designed. Then, stability analysis is conducted using Lyapunov theory, adaptive laws are designed, and the introduced virtual control accelerations are converted into actual control variables. Finally, simulations are conducted under different simulation conditions based on the disturbance sources. The results show that although the use of hybrid low-thrust propulsion breaks the symmetry of the solar sail in configuration, the proposed control strategy can effectively achieve the station-keeping and disturbance estimation of the spacecraft with only a small amount of propellant consumed and position tracking errors up to decimeters.

Electric Sail Mission Expeditor, ESME: Software Architecture and Initial ESTCube Lunar Cubesat E-Sail Experiment Design

The electric solar wind sail, or E-sail, is a novel deep space propulsion concept which has not been demonstrated in space yet. While the solar wind is the authentic operational environment of the electric sail, its fundamentals can be demonstrated in the ionosphere where the E-sail can be used as a plasma brake for deorbiting. Two missions to be launched in 2023, Foresail-1p and ESTCube-2, will attempt to demonstrate Coulomb drag propulsion (an umbrella term for the E-sail and plasma brake) in low Earth orbit. This paper presents the next step of bringing the E-sail to deep space—we provide the initial modelling and trajectory analysis of demonstrating the E-sail in solar wind. The preliminary analysis assumes a six-unit cubesat being inserted in the lunar orbit where it deploys several hundred meters of the E-sail tether and charges the tether at 10–20 kV. The spacecraft will experience acceleration due to the solar wind particles being deflected by the electrostatic sheath around the charged tether. The paper includes two new concepts: the software architecture of a new mission design tool, the Electric Sail Mission Expeditor (ESME), and the initial E-sail experiment design for the lunar orbit. Our solar-wind simulation places the Electric Sail Test Cube (ESTCube) lunar cubesat with the E-sail tether in average solar wind conditions and we estimate a force of 1.51×10−4 N produced by the Coulomb drag on a 2 km tether charged to 20 kV. Our trajectory analysis takes the 15 kg cubesat from the lunar back to the Earth orbit in under three years assuming a 2 km long tether and 20 kV. The results of this paper are used to set scientific requirements for the conceptional ESTCube lunar nanospacecraft mission design to be published subsequently in the Special Issue “Advances in CubeSat Sails and Tethers”.

Improving Solar Observing Capabilities with Diffractive Solar Sailing

Improving Solar Observing Capabilities with Diffractive Solar Sailing

Advancements in Large Solar Sail Technology for Heliophysics Missions Requiring High Efficiency Propulsion and High Inclination Solar Orbits

Advancements in Large Solar Sail Technology for Heliophysics Missions Requiring High Efficiency Propulsion and High Inclination Solar Orbits

Solar Sail Missions for Sub-L1 Sampling of the Interplanetary Magnetic Field and Plasma on the Sun-Earth Line

Solar Sail Missions for Sub-L1 Sampling of the Interplanetary Magnetic Field and Plasma on the Sun-Earth Line

Effect of Dust and Hot Spots on the Thermal Stability of Laser Sails.

Laser sails propelled by gigawatt-scale ground-based laser arrays have the potential to reach relativistic speeds, traversing the solar system in hours and reaching nearby stars in years. Here, we describe the danger interplanetary dust poses to the survival of a laser sail during its acceleration phase. We show through multiphysics simulations how localized heating from a single optically absorbing dust particle on the sail can initiate a thermal runaway process that rapidly spreads and destroys the entire sail. We explore potential mitigation strategies, including increasing the in-plane thermal conductivity of the sail to reduce the peak temperature at hot spots and isolating the absorptive regions of the sail that can burn away individually.

Chasing nomadic worlds: A new class of deep space missions

Nomadic worlds, i.e., objects not gravitationally bound to any star(s), are of great interest to planetary science and astrobiology. They have garnered attention recently due to constraints derived from microlensing surveys and the recent discovery of interstellar planetesimals. In this paper, we roughly estimate the prevalence of nomadic worlds with radii of 100km≲R≲104km. The cumulative number density n>>R appears to follow a heuristic power law given by n>∝R−3. Therefore, smaller objects are probably much more numerous than larger rocky nomadic planets, and statistically more likely to have members relatively close to the inner Solar system. Our results suggest that tens to hundreds of planet-sized nomadic worlds might populate the spherical volume centered on Earth and circumscribed by Proxima Centauri, and may thus comprise closer interstellar targets than any planets bound to stars. For the first time, we systematically analyze the feasibility of exploring these unbounded objects via deep space missions. We investigate what near-future propulsion systems could allow us to reach nomadic worlds of radius >R in a 50-year flight timescale. Objects with R∼100 km are within the purview of multiple propulsion methods such as electric sails, laser electric propulsion, and solar sails. In contrast, nomadic worlds with R≳1000 km are accessible by laser sails (and perhaps nuclear fusion), thereby underscoring their vast potential for deep space exploration.

Dynamic modeling and control of a solar sail considering large-amplitude nonlinear vibration

The solar sail spacecraft utilizes Solar Radiation Pressure (SRP) to achieve propulsion, which can realize long-term acceleration without fuel consumption, making it an appealing option for deep space exploration and polar-sitter observation. However, because of the large-scale and high-flexibility of the membrane structure, the solar sail poses challenging dynamic and control issues. Precise dynamic modeling and effective control design can provide theoretical guidance for the efficient functioning of solar sail, which are of great significance and urgently need to be studied. In this paper, a dynamic model that can describe the large-amplitude vibrations of the solar sail is established. Additionally, an attitude tracking controller and a cable-based nonlinear vibration controller are designed to control the attitude motion and flexible vibration of the solar sail. The results show that the established nonlinear rigid-flexible coupling dynamic model is more accurate compared to the linear dynamic model. The polynomial fitting method can characterize the nonlinear dynamics of the solar sail extremely effectively while cutting the program runtime to 5% of the original. Two controllers designed in this paper can make the solar sail maneuver follow the desired trajectory accurately while reducing the sail surface vibration by more than 40%. The research outcomes of this paper can provide references for the dynamic study and active control of large-scale membrane spacecraft.

Attitude control for a full-scale flexible electric solar wind sail spacecraft on heliocentric and displaced non-Keplerian orbits

The electric solar wind sail (E-sail) spacecraft is a fuel-free propulsion system with promising potential in deep space explorations and solar activity monitoring missions. It is challenging to conduct attitude control for a full-scale flexible E-sail spacecraft due to its complex dynamical characteristics, including the spatial multi-scale, high-speed spinning, and large deformations. In this work, a double-loop attitude control strategy for the flexible E-sail spacecraft with high accuracy and efficiency is proposed. The E-sail spacecraft is firstly modeled by the referenced nodal coordinate formulation, where the rotations are described by the Lie group approach. A state-feedback controller developed from the Lyapunov stability theory is prescribed as the inner loop. The gain is obtained by solving a semidefinite programming problem with linear matrix inequality constraints, which is globally optimal and numerically reliable. A multi-variable proportional-integral-derivative controller is then introduced as the outer loop for flexibly enhancing the control performance. Several missions of the E-sail spacecraft, including attitude maneuvers on heliocentric and displaced non-Keplerian orbits, are studied to show that the desired attitude adjustments are accurately and efficiently achieved without exciting high-frequency oscillations. The double-loop control strategy has great prospects in designing and implementing orbital transformation and long-term stable Sun-orbiting missions.

Attitude Tracking Adaptive Control of a Geocentric Polar Displaced Solar Sail

To deal with the attitude tracking control problem of a struck or pierced geocentric polar displaced solar sail (GPDSS), an attitude adaptive control strategy is proposed in this paper under the complex conditions of unknown inertial parameters, external disturbance and input saturation. First, on the basis of a flexible solar sail spacecraft attitude dynamics model with damping terms and vibration initial values, an integrated disturbance term, including inertial parameter uncertainties and external disturbance, is constructed. Second, a radial basis function neural network is applied to design a disturbance estimator with an adaptive law to estimate the integrated disturbance in real time. Then, a sliding-mode controller with fixed-time convergence in the reach phase and finite-time stability in the sliding phase is designed, and stability analysis is conducted by using the Lyapunov theory. Finally, comparative simulations with a linear sliding-mode controller and numerical simulations under various workings are performed. The results show that the designed adaptive control strategy can effectively achieve the attitude tracking control of the GPDSS.

Space weather investigation Frontier (SWIFT)

The Space Weather Investigation Frontier (SWIFT) mission will aim at making major discoveries on the three-dimensional structure and dynamics of heliospheric structures that drive space weather. The focus will be on Interplanetary Coronal Mass Ejections (ICMEs) that originate from massive expulsions of plasma and magnetic flux from the solar corona. They cause the largest geomagnetic storms and solar energetic particle events, threatening to endanger life and disrupt technology on Earth and in space. A big current problem, both regarding fundamental solar-terrestrial physics and space weather, is that we do not yet understand spatial characteristics and temporal evolution of ICMEs and that the existing remote-sensing and in-situ observatories are not suited for resolving multi-layered and evolutionary structures in these massive storm drivers. Here, we propose a groundbreaking mission concept study using solar sail technology that, for the first time, will make continuous, in-situ multi-point observations along the Sun-Earth line beyond the Lagrange point L1 (sub-L1). This unique position, in combination with L1 assets, will allow distinguishing between local and global processes, spatial characteristics, temporal evolution, and particle energization mechanisms related to ICMEs. In addition, measurements of the magnetic field in earthbound ICMEs and their sub-structures from the SWIFT location will double the current forecasting lead-times from L1. This concept also paves the way for missions with increasingly longer forecasting lead-times, addressing NASA and NOAA’s space weather goals, as set forth by the Decadal Survey. The objective of this communication is to inform the community of the ongoing effort, including plans to further develop the mission concept, supported by the Heliophysics Flight Opportunities Studies (HFOS) program under NASA’s Research Opportunities in Space and Earth Sciences (ROSES).

Indirect trajectory optimization via solar sailing primer vector theory: Minimum solar-angle transfers

Building upon the recent development of solar sailing primer vector theory and its successful applications, we propose a new formulation for indirect solar-sail trajectory optimization, which minimizes solar angle (cone angle between the sail normal and sunlight vectors) over a trajectory. The minimum solar-angle objective is introduced to address a typical demand in mission design: having the ability to design trajectories with fixed time-of-flight, which is especially crucial when the mission involves time-sensitive events, such as scientific observations with specific lighting conditions, gravity assists at specific epochs, to name a few. We derive an analytical optimal control law for minimum solar-angle sail transfers by applying Pontryagin’s optimality principle. Our theoretical results illuminate that a quantity termed solar sailing primer vector characterizes the optimal solar-sail control law for both minimum-time and minimum solar-angle transfers, as is the case in Lawden’s primer vector theory for conventional low-thrust transfers. We numerically demonstrate these theoretical results by applying them to asteroid rendezvous transfers for NASA’s NEA Scout mission. The numerical examples also reveal the numerical advantage of using the minimum solar-angle objective over the minimum-time one for solar-sail trajectory design because of the smoother optimal control profile. Solar sailing primer vector theory provides a tool to characterize the optimal control law independent of particular state representations or solution methods, enabling mission designers to combine it with a wealth of techniques developed for low-thrust trajectory optimization.

LightSail 2 Solar Sail Control and Orbit Evolution

The propellantless thrust of solar sails makes them capable of entirely new classes of missions compared to conventional or electric engines. Initiated in 2010, the Planetary Society’s LightSail program sought to advance solar sail technology with the flights of LightSail 1 and 2. From launch in 2019 to deorbit in late 2022, LightSail 2 demonstrated the first controlled solar sailing in Earth’s orbit using a CubeSat. By adjusting the orientation of the sail relative to the sun twice per orbit, LightSail 2 controlled solar radiation pressure on the sail to offset losses in orbital energy from atmospheric drag. Previous papers analyzed early mission results to show the effect this had on reducing the spacecraft’s orbital decay rate. Subsequent refinements to the spacecraft’s attitude control made throughout the mission eventually enabled it to achieve sustained net increases in orbital energy. This paper presents an analysis of the orbit changes and attitude control performance over the entire mission. Methods of assessing and improving the sail control are described. Activities and attitude behavior during the final deorbit phase are also analyzed, with results relevant to future drag sails as well as solar sail missions.

Integrated attitude and shape control for OrigamiSats with variable surface reflectivity

OrigamiSats, a new concept in solar sailing, are origami spacecraft with reflective panels that, when flat, operate as a conventional solar sail. Shape reconfiguration, i.e. “folding” of the origami design, allows the OrigamiSat to change operational modes, performing different functions as per mission requirements. For example, a flat OrigamiSat could be reconfigured into the shape of a parabolic reflector, before returning to the flat configuration when required to operate again as a solar sail, providing propellant-free propulsion. The attitude dynamics and shape reconfiguration of OrigamiSats are known to be highly coupled, thus presenting a challenge from a control perspective. This paper investigates the problem of integrating attitude and shape control of a Miura-fold pattern OrigamiSat through the use of variable reflectivity, allowing differences in solar radiation pressure to be used to enact shape reconfiguration and attitude manoeuvres. A closed-loop feedback controller is presented which combines and balances the attitude and shape control requirements, and gain-scheduling is implemented to address some specific features of the system dynamics. Numerical simulations of the multibody dynamics of the system are used to test the proposed controller and simulations of some example manoeuvres are performed which demonstrate the system’s performance.

Optimal interplanetary trajectories for Sun-facing ideal diffractive sails

A diffractive sail is a solar sail whose exposed surface is covered by an advanced diffractive metamaterial film with engineered optical properties. This study examines the optimal performance of a diffractive solar sail with a Sun-facing attitude in a typical orbit-to-orbit heliocentric transfer. A Sun-facing attitude, which can be passively maintained through the suitable design of the sail shape, is obtained when the sail nominal plane is perpendicular to the Sun–spacecraft line. Unlike an ideal reflective sail, a Sun-facing diffractive sail generates a large transverse thrust component that can be effectively exploited to change the orbital angular momentum. Using a recent thrust model, this study determines the optimal control law of a Sun-facing ideal diffractive sail and simulates the minimum transfer times for a set of interplanetary mission scenarios. It also quantifies the performance difference between Sun-facing diffractive sail and reflective sail. A case study presents the results of a potential mission to the asteroid 16 Psyche.

Solar Sail Orbit Raising with Electro-Optically Controlled Diffractive Film

The aim of this paper is to analyze the transfer performance of a spacecraft whose primary propulsion system is a diffractive solar sail with active, switchable panels. The spacecraft uses a propellantless thruster that converts the solar radiation pressure into propulsive acceleration by taking advantage of the diffractive property of an electro-optically controlled (binary) metamaterial. The proposed analysis considers a heliocentric mission scenario where the spacecraft is required to perform a two-dimensional transfer between two concentric and coplanar circular orbits. The sail attitude is assumed to be Sun-facing, that is, with its sail nominal plane perpendicular to the incoming sunlight. This is possible since, unlike a more conventional solar sail concept that uses metalized highly reflective thin films to reflect the photons, a diffractive sail is theoretically able to generate a component of the thrust vector along the sail nominal plane also in a Sun-facing configuration. The electro-optically controlled sail film is used to change the in-plane component of the thrust vector to accomplish the transfer by minimizing the total flight time without changing the sail attitude with respect to an orbital reference frame. This work extends the mathematical model recently proposed by the authors by including the potential offered by an active control of the diffractive sail film. The paper also thoroughly analyzes the diffractive sail-based spacecraft performance in a set of classical circle-to-circle heliocentric trajectories that model transfers from Earth to Mars, Venus and Jupiter.

Influence of Chemical Treatment of Natural Fibre using Shape Memory Alloy for Aeronautics

This article offers a thorough review of shape memory alloys' (SMAs') uses in the Space research field. The utility of SMAs in a variety of applications, including morphing wings (using both experimental and modelling methods), customising orientation and inlet shapes for various propulsion systems, implementing flexible chevrons to improve thrust while lowering noise, and reducing overall power consumption, is the main topic of this paper. The use of SMAs in applications in space is also covered in the paper, including how they may be used to create low-shock launchers, isolate micro-vibrations, and enable self-deployable solar sails. The essay also emphasises the novel structures and tools made possible by SMAs. One noteworthy method covered in the article is putting SMA wires in the laminate's midplane and embedding them into the fabric a layer of composite laminates. When compared to traditional composite constructions, the incorporation of SMAs into composite has shown better damage resistance and ductility. The reaction of a bright hybrid plastic composite plates to a very low-velocity impact is examined experimentally and numerically in this paper, which highlights the benefits of inserting SMA wires. Among these benefits are improved damage resistance, better ductility, higher composite hardness, and increased energy absorption before failure. Shape memory alloy (SMA) are the subject of extensive industrial applications and ongoing study in the field of materials. Its two distinguishing qualities, the shape memory impact and superelasticity, are mostly to blame for this. A composition's structure that suffered a phase transition as a result of temperatures, pressures, mechanical forces, and other factors is implies to as having a "shape memory effect". The composition, despite the very significant plastic deformation to which its surface is susceptible to, may recover to its original form under the influence of temperature as well as other factors.