Solar Sail Optimal Transfer Between Heliostationary Points

This Note analyzes the transfer between two heliostationary points that are the same distance from the sun. The problem is addressed within an optimal framework in which a constraint is enforced on the minimum sun–spacecraft distance along the transfer trajectory

Electric sail phasing maneuvers for constellation deployment

The aim of this work is to investigate heliocentric phasing maneuvers performed by a spacecraft propelled by an Electric Solar Wind Sail, that is, an innovative propellantless propulsion system that consists of a spinning grid of charged tethers that uses solar wind momentum to produce thrust. It is assumed that the Electric Solar Wind Sail may be controlled by varying its attitude with respect to a classical orbital reference frame, and by switching the tether grid off to obtain Keplerian arcs along its phasing trajectory. The analysis is conducted within an optimal framework, the aim of which is to find both the optimal control law and the minimum-time phasing trajectory for a given angular drift along the (assigned) working orbit. A typical phasing scenario is analyzed, by considering either a drift ahead or a drift behind maneuver on a circular, heliocentric orbit of given radius. The paper also investigates the possibility of using an Electric Solar Wind Sail-based deployer to place a constellation of satellites on the same working orbit. In that case, the optimal flight time is obtained in a compact, semianalytical form as a function of both the propulsion system performance and the number of the sail-deployed satellites

Solar Sail Simplified Optimal Control Law for Reaching High Heliocentric Distances

The aim of this paper is to analyze optimal trajectories of a solar sail-based spacecraft in missions towards the outer Solar System region. The paper proposes a simplified approach able to estimate the minimum flight time required to reach a given (sufficiently high) heliocentric distance. In particular, the effect of a set of solar photonic assists on the overall mission performance is analyzed with a simplified numerical approach. A comparison with results taken from the existing literature show the soundness of the proposed approach

Artificial Collinear Lagrangian Point Maintenance With Electric Solar Wind Sail

This article discusses the maintenance of an L-1-type artificial equilibrium point in the Sun-[Earth+Moon] circular restricted three-body problem by means of an electric solar wind sail. The reference configuration instability is compensated for with a feedback control law that adjusts the grid voltage as a function of the distance from the natural L-1 point. Two different control strategies are analyzed assuming the solar wind fluctuations to be modeled through a statistical approach

Logarithmic spiral trajectories generated by Solar sails

Analytic solutions to continuous thrust-propelled trajectories are available in a few cases only. An interesting case is offered by the logarithmic spiral, that is, a trajectory characterized by a constant flight path angle and a fixed thrust vector direction in an orbital reference frame. The logarithmic spiral is important from a practical point of view, because it may be passively maintained by a Solar sail-based spacecraft. The aim of this paper is to provide a systematic study concerning the possibility of inserting a Solar sail-based spacecraft into a heliocentric logarithmic spiral trajectory without using any impulsive maneuver. The required conditions to be met by the sail in terms of attitude angle, propulsive performance, parking orbit characteristics, and initial position are thoroughly investigated. The closed-form variations of the osculating orbital parameters are analyzed, and the obtained analytical results are used for investigating the phasing maneuver of a Solar sail along an elliptic heliocentric orbit. In this mission scenario, the phasing orbit is composed of two symmetric logarithmic spiral trajectories connected with a coasting arc

Electric sail static structural analysis with finite element approach

The propulsive characteristics of an Electric Solar Wind Sail are usually evaluated using a simplified model in which all the sail tethers are coplanar and form a sort of rigid disk. However, the three-dimensional arrangement of the tethers is fundamental information in the study of the spacecraft performance, and must be accounted for in refined mission analyses. In this paper, a Finite Element approach is chosen to estimate the deflected shape of the tethers, thus allowing important information on the structural response of the sail to be obtained. A parametric code is developed to perform a static analysis of an Electric Solar Wind Sail, whose requirements are given in terms of payload mass and spacecraft characteristic acceleration. In particular, the tether structural response is investigated using three different beam models, which are compared in terms of accuracy and computational efficiency. The analysis is specialized to the noteworthy case of a Sun-facing sail that is placed at a distance of one astronomical unit from the Sun. The numerical results, which concern a set of possible sail configurations, are compared with those taken from analytical models

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

Electric Sail Phasing Maneuvers for Constellation Deployment

The aim of this work is to investigate heliocentric phasing maneuvers performed by a spacecraft propelled by an Electric Solar Wind Sail, an innovative propellantless propulsion system. It is assumed that the sail may be controlled by varying its attitude, and by switching the tether grid off to obtain Keplerian arcs in the trajectory. The analysis is conducted within an optimal framework, whose aim is to find the minimum-time phasing trajectory for a given angular drift, and the corresponding time variation of the control variables. A typical phasing scenario is analyzed, by considering either a drift ahead or a drift behind maneuver option. We also investigate the possibility of using an Electric Solar Wind Sail-based deployer to place a constellation of satellites on the same heliocentric circular orbit. The corresponding flight times are obtained as a function of the sail performance and the number of satellites

Management of cutaneous discomfort in patients with scleroderma: a clinical trial.

Systemic sclerosis (scleroderma) is a disease of unknown cause, the hallmark of which is induration of the skin. This bad condition of the skin influences negatively the quality of life of patients with scleroderma. The aim of the study was to verify the efficacy of two formulations, specifically designed to wash, moisturize and soothe the scleroderma skin. An independent, randomized, double blind, controlled trial was conducted in the Department of Rheumatology of "A. Galateo" Hospital in San Cesario di Lecce. Forty-six women affected by scleroderma, and treated with Iloprost every month, were divided into two groups: group 1 followed a specific treatment with cleansing formulation only, group 2 followed a combined treatment with the cleansing solution and the moisturizing solution. In addition, a third group was evaluated: 14 women, who did not undergo intravenous Iloprost therapy, were treated simultaneously with the cleansing formulation and the moisturizing formulation. The three treatments lasted for 4 weeks. Reduction in trans epidermal water loss (TEWL), increase in moisturization of the stratum corneum, reduction in Skin Score and improvement in quality of life were assessed. Very significant improvement in quality of life occurred in each group. Group 2 obtained very significant improvement in hydration and reduction in skin score and TEWL. The study showed that the daily use of both formulations proved to be effective in washing, hydrating and soothing the skin of patients with scleroderma, especially in association with Iloprost therapy