Spiral trajectories induced by radial thrust with applications to generalized sails

In this study, new analytical solutions to the equations of motion of a propelled spacecraft are investigated using a shape-based approach. There is an assumption that the spacecraft travels a two-dimensional spiral trajectory in which the orbital radius is proportional to an assigned power of the spacecraft angular coordinate. The exact solution to the equations of motion is obtained as a function of time in the case of a purely radial thrust, and the propulsive acceleration magnitude necessary for the spacecraft to track the prescribed spiral trajectory is found in a closed form. The analytical results are then specialized to the case of a generalized sail, that is, a propulsion system capable of providing an outward radial propulsive acceleration, the magnitude of which depends on a given power of the Sun-spacecraft distance. In particular, the conditions for an outward radial thrust and the required sail performance are quantified and thoroughly discussed. It is worth noting that these propulsion systems provide a purely radial thrust when their orientation is Sun-facing. This is an important advantage from an engineering point of view because, depending on the particular propulsion system, a Sun-facing attitude can be stable or obtainable in a passive way. A case study is finally presented, where the generalized sail is assumed to start the spiral trajectory from the Earth’s heliocentric orbit. The main outcome is that the required sail performance is in principle achievable on the basis of many results available in the literature

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

Extraplanetary Exploration Using Electric Solar Wind Sail

This doctoral research investigates the problems in the dynamics and control of extraplanetary exploration using an electric solar wind sail (E-sail). The E-sail is a novel propellantless propulsion technology that harvests energy by repelling the charged particles in solar wind. It consists of a spinning central spacecraft connected by kilometer-long and thin positively charged tethers with remote units at their tips. Three dynamic models of E-sail are developed: the high-fidelity tether dynamic model, the generalized E-sail model, and the reduced-order analytical E-sail model. The coupling effects of orbital and self-spinning motions of the E-sail, the elastic deformation of tethers, the rigid-flexible coupling effect on the attitude dynamics and spin control of E-sail, and the stability control of the flexible E-sail are thoroughly investigated based on these models. Meanwhile, the controllability of E-sail spin rate and the attitude of the E-sail are demonstrated, and the trajectory tracking problems in extraplanetary exploration missions are studied. Finally, the main contributions of this dissertation are introduced

Extraplanetary Exploration Using Electric Solar Wind Sail

This doctoral research investigates the problems in the dynamics and control of extraplanetary exploration using an electric solar wind sail (E-sail). The E-sail is a novel propellantless propulsion technology that harvests energy by repelling the charged particles in solar wind. It consists of a spinning central spacecraft connected by kilometer-long and thin positively charged tethers with remote units at their tips. Three dynamic models of E-sail are developed: the high-fidelity tether dynamic model, the generalized E-sail model, and the reduced-order analytical E-sail model. The coupling effects of orbital and self-spinning motions of the E-sail, the elastic deformation of tethers, the rigid-flexible coupling effect on the attitude dynamics and spin control of E-sail, and the stability control of the flexible E-sail are thoroughly investigated based on these models. Meanwhile, the controllability of E-sail spin rate and the attitude of the E-sail are demonstrated, and the trajectory tracking problems in extraplanetary exploration missions are studied. Finally, the main contributions of this dissertation are introduced

Solar-sail mission design for multiple near-Earth asteroid rendezvous

Solar sailing is the use of a thin and lightweight membrane to reflect sunlight and obtain a thrust force on the spacecraft. That is, a sailcraft has a potentially-infinite specific impulse and, therefore, it is an attractive solution to reach mission goals otherwise not achievable, or very expensive in terms of propellant consumption. The recent scientific interest in near-Earth asteroids (NEAs) and the classification of some of those as potentially hazardous asteroids (PHAs) for the Earth stimulated the interest in their exploration. Specifically, a multiple NEA rendezvous mission is attractive for solar-sail technology demonstration as well as for improving our knowledge about NEAs. A preliminary result in a recent study showed the possibility to rendezvous three NEAs in less than ten years. According to the NASA’s NEA database, more than 12,000 asteroids are orbiting around the Earth and more than 1,000 of them are classified as PHA. Therefore, the selection of the candidates for a multiple-rendezvous mission is firstly a combinatorial problem, with more than a trillion of possible combinations with permutations of only three objects. Moreover, for each sequence, an optimal control problem should be solved to find a feasible solar-sail trajectory. This is a mixed combinatorial/optimisation problem, notoriously complex to tackle all at once. Considering the technology constraints of the DLR/ESA Gossamer roadmap, this thesis focuses on developing a methodology for the preliminary design of a mission to visit a number of NEAs through solar sailing. This is divided into three sequential steps. First, two methods to obtain a fast and reliable trajectory model for solar sailing are studied. In particular, a shape-based approach is developed which is specific to solar-sail trajectories. As such, the shape of the trajectory that connects two points in space is designed and the control needed by the sailcraft to follow it is analytically retrieved. The second method exploits the homotopy and continuation theory to find solar-sail trajectories starting from classical low-thrust ones. Subsequently, an algorithm to search through the possible sequences of asteroids is developed. Because of the combinatorial characteristic of the problem and the tree nature of the search space, two criteria are used to reduce the computational effort needed: (a) a reduced database of asteroids is used which contains objects interesting for planetary defence and human spaceflight; and (b) a local pruning is carried out at each branch of the tree search to discard those target asteroids that are less likely to be reached by the sailcraft considered. To reduce further the computational effort needed in this step, the shape-based approach for solar sailing is used to generate preliminary trajectories within the tree search. Lastly, two algorithms are developed which numerically optimise the resulting trajectories with a refined model and ephemerides. These are designed to work with minimum input required by the user. The shape-based approach developed in the first stage is used as an initial-guess solution for the optimisation. This study provides a set of feasible mission scenarios for informing the stakeholders on future mission options. In fact, it is shown that a large number of five-NEA rendezvous missions are feasible in a ten-year launch window, if a solar sail is used. Moreover, this study shows that the mission-related technology readiness level for the available solar-sail technology is larger than it was previously thought and that such a mission can be performed with current or at least near-term solar sail technology. Numerical examples are presented which show the ability of a solar sail both to perform challenging multiple NEA rendezvous and to change the mission en-route

Minimum-Fuel Low-Thrust Trajectory Optimization Via a Direct Adaptive Evolutionary Approach

Space missions with low-thrust propulsion systems are of appreciable interest to space agencies because of their practicality due to higher specific impulses. This research proposes a technique to the solution of minimum-fuel non-coplanar orbit transfer problem. A direct adaptive method via Fitness Landscape Analysis (FLA) is coupled with a constrained evolutionary technique to explore the solution space for designing low-thrust orbit transfer trajectories. Taking advantage of the solution for multi-impulse orbit transfer problem, and parameterization of thrust vector, the orbital maneuver is transformed into a constrained continuous optimization problem. A constrained Estimation of Distribution Algorithms (EDA) is utilized to discover optimal transfer trajectories, while maintaining feasibility of the solutions. The low-thrust trajectory optimization problem is characterized via three parameters, referred to as problem identifiers, and the dispersion metric is utilized for analyzing the complexity of the solution domain. Two adaptive operators including the kernel density and outlier detection distance threshold within the framework of the employed EDA are developed, which work based on the landscape feature of the orbit transfer problem. Simulations are proposed to validate the efficacy of the proposed methodology in comparison to the non-adaptive approach. Results indicate that the adaptive approach possesses more feasibility ratio and higher optimality of the obtained solutions.BEAZ Bizkaia, 3/12/DP/2021/00150; SPRI Group, Ekintzaile Program EK-00112-202

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Length Scaling In Spacecraft Dynamics

This research evaluates the length-dependence of a number of space environmental accelerations, both orbital and angular. Many non-gravitational effects accelerate a smaller body more than a larger body, thanks to ratios such as area-to-mass that vary inversely with characteristic length. This research studies these accelerations, and the corresponding dynamics, with an interest in applying the results to methods of propellant-free spacecraft propulsion. After surveying space environmental accelerations, the analysis focuses on three particular cases: solar radiation pressure, aerodynamic drag, and the Lorentz force. Each of these accelerations has an explicit dependence on length-scaling, such that millimeter-scale bodies experience characteristically larger magnitudes of acceleration than typical spacecraft. For the case of solar-radiation pressure, a flat integrated circuit is considered as a low-cost, feasible solar sail with passive, locally and/or globally stable attitude control. The modified orbital and attitude dynamics are considered for heliocentric, geocentric, and three-body orbits. For aerodynamic drag, a similar thin-plate integrated circuit bus is considered for atmospheric re-entry. Here, the spacecraft's cross-sectional area-to-mass ratio drives the magnitude of drag. So, small bodies can remove orbital kinetic energy very efficiently. Further, length-scaling laws for thermodynamics and fluid mechanics show that a very small spacecraft can even survive the intense re-entry thermal environment without burning-up or requiring active control. Research on the Lorentz force has found that an orbiting body with an electrostatic charge can interact with a planetary magnetic field and experience a force. In this case, the driving parameter is the electrostatic charge-to-mass ratio, a quantity that depends on the inverse square of characteristic length. This analysis presents a proposal for a small spacecraft that can demonstrate the Lorentz force in Earth orbit. A sample low charge-to-mass mission is proposed, wherein the Lorentz force is considered for Jovian capture and orbit circularization. The Lorentz force is also evaluated in relation to the so-called Earth Flyby Anomaly, in which an unknown acceleration affected the orbit of six spacecraft as they were executing Earth gravity assists. This research finds that the Lorentz force cannot be associated with the unknown acceleration, in spite of having similar characteristics

Marshall Space Flight Center Research and Technology Report 2017

This report features over 60 technology development and scientific research efforts that collectively aim to enable new capabilities in spaceflight, expand the reach of human exploration, and reveal new knowledge about the universe in which we live. These efforts include a wide array of strategic developments: launch propulsion technologies that facilitate more reliable, routine, and cost effective access to space; in-space propulsion developments that provide new solutions to space transportation requirements; autonomous systems designed to increase our utilization of robotics to accomplish critical missions; life support technologies that target our ability to implement closed-loop environmental resource utilization; science instruments that enable terrestrial, solar, planetary and deep space observations and discovery; and manufacturing technologies that will change the way we fabricate everything from rocket engines to in situ generated fuel and consumables

2020 NASA Technology Taxonomy

This document is an update (new photos used) of the PDF version of the 2020 NASA Technology Taxonomy that will be available to download on the OCT Public Website. The updated 2020 NASA Technology Taxonomy, or "technology dictionary", uses a technology discipline based approach that realigns like-technologies independent of their application within the NASA mission portfolio. This tool is meant to serve as a common technology discipline-based communication tool across the agency and with its partners in other government agencies, academia, industry, and across the world