1,721,003 research outputs found
Design and control of solar radiation pressure assisted missions in the sun-earth restricted three-body problem
No full textThe scientific interest in space exploration is driven by the desire to answer fundamental questions relating to the formation of our solar system and life on Earth. Space agencies are currently pushing the boundaries of space mission design to meet scientific goals. Thus, space missions require novel trajectories to further human space exploration. A modern approach that has arisen in space mission design is to use dynamical system tools that exploit the natural dynamics of the solar system. A spacecraft's natural dynamics are affected by environmental perturbations such as Solar Radiation Pressure (SRP). Traditionally, the design of space missions requires any perturbations to be counteracted through corrective manoeuvres. However, these corrective manoeuvres require propellant and therefore the pre-storing of fuel. This thesis investigates fuel-free propulsion for harnessing SRP in the design of space missions of the Sun-Earth restricted three-body problem. SRP propulsion is applied to the spacecraft's orbit control and furthermore to create the propulsion required for the design of transfers between quasi-periodic orbits and end-of-life disposal trajectories. The advantage of SRP manoeuvres is that the spacecraft can have access to an unlimited source of propellant (the Sun's radiation) consequently extending its life and reducing the overall mission costs; where the advancement in space technology makes harnessing SRP devices possible for future missions design. SRP manoeuvres are triggered by light and extended reflective deployable structures (i.e., mirror-like surfaces). The magnitude of the SRP acceleration is a function of the spacecraft's area-to-mass ratio, its reflectivity properties, mass and orientation of the reflective surface to the Sun-line direction. This thesis demonstrates that SRP manoeuvres are an effective and an efficient approach to stabilise the natural dynamics of the spacecraft in the Sun-Earth system. The size of the required reflective deployable area and spacecraft pointing accuracy are the ultimate outcomes of this research. Along with the design of the reflective area, the definition of a new control law, a method to perform transfers between quasi-periodic orbits and a strategy for the end-of-life disposal are the major important research findings
Eddy Currents applied to de-tumbling of space debris: feasibility analysis, design and optimization aspects
No full textA feasibility study of solar radiation pressure feedback control strategy for unstable periodic orbits in the restricted three-body problem
No full textThis paper investigates a Hamiltonian structure preserving control strategy that uses, where possible, solar radiation pressure as an alternative propellant-free control acceleration. This control strategy is based on previous authors work, but it is extended to a general case in which complex and conjugate eigenvalues occur at high amplitude orbits. High amplitude orbits are currently of interest to the European Space Agency (ESA) for future Libration-points orbits space missions since a lower insertion V is required to reach these orbits by saving propellant. This control aims to stabilise the LPOs in the sense of Lyapunov by achieving simple stability, and it preserves the Hamiltonian nature of the controlled system. Based on the design of the feedback control, the purpose of this work is to verify when the use of SRP is feasible. Indeed, the order of magnitude of solar radiation pressure acceleration depends on the spacecraft’s reflective area, the area orientation angle and its reflectivity properties. Therefore, due to constraints in the orientation angle and in the deployable reflective area, it is important to identify when, along the spacecraft’s trajectory it is possible to apply SRP to stabilise the unstable periodic orbit. This limitation in the actuator causes the “windup” of the controller; thus, the use of desaturation methods are investigated
The end-of-life disposal of satellites in libration-point orbits using solar radiation pressure
Get PDFThis paper proposes an end-of-life propellant-free disposal strategy for libration-point orbits which uses solar radiation pressure to restrict the evolution of the spacecraft motion. The spacecraft is initially disposed into the unstable manifold leaving the libration-point orbit, before a reflective sun-pointing surface is deployed to enhance the effect of solar radiation pressure. Therefore, the consequent increase in energy prevents the spacecraft’s return to Earth. Three European Space Agency missions are selected as test case scenarios: Herschel, SOHO and Gaia. Guidelines for the end-of-life disposal of future libration-point orbit missions are proposed and a preliminary study on the effect of the Earth’s orbital eccentricity on the disposal strategy is shown for the Gaia mission
Libration-point orbit missions disposal at the end-of-life through solar radiation pressure
No full textThis paper investigates an end-of-life propellant-free disposal strategy for Libration-point orbits that allows the zero-velocity curves to be closed by exploiting solar radiation pressure. The spacecraft is initially disposed into the unstable manifold leaving the Libration-point orbit, before a reflective sun-pointing surface is deployed to enhance the effect of solar radiation pressure. Therefore, the consequent increase in energy prevents the spacecraft's return to Earth. An energetic approach is used to compute the required area for the Hill's curve closure at the pseudo Libration-point SL2, via numerical optimisation. Three European Space Agency missions are selected as test case scenarios: Herschel, SOHO and Gaia. Finally, guidelines for the end-of-life disposal of future Libration-point orbit missions are proposed
Solar Radiation Pressure Hamiltonian Feedback Control for Unstable Libration-Point Orbits
Get PDFThis work investigates a Hamiltonian structure-preserving control that uses the acceleration of solar radiation pressure for the stabilization of unstable periodic orbits in the circular restricted three-body problem. This control aims to stabilize the libration-point orbits in the sense of Lyapunov by achieving simple stability. It also preserves the Hamiltonian nature of the controlled system. The Hamiltonian structure-preserving control is then extended to a general case in which complex and conjugate eigenvalues occur at high-amplitude orbits. High-amplitude orbits are currently of interest to the European Space Agency for future libration-point orbit missions because they require a lower insertion Δv compared to low-amplitude orbits. Based on the design of the feedback control, the purpose of this work is to verify when the use of solar radiation pressure is feasible and to determine the structural requirements and the spacecraft’s pointing accuracy
Ejecta Formation, Early Collisional Processes, and Dynamical Evolution after the DART Impact on Dimorphos
Get PDFNASA’s DART spacecraft is planned to reach and impact asteroid Dimorphos, the small moon of binary asteroid (65803) Didymos, at a velocity of 6 km s−1 in late 2022 September. DART will be the first mission to test the “kinetic impactor” technique, aimed at deflecting the orbital path of a potentially hazardous asteroid. The success and effectiveness of this technique resides in the efficiency of momentum exchange between the spacecraft and the impacted target. This depends on many factors, including the cratering process, the formation of ejecta, and their fate, as they remain in the system or escape from it, carrying momentum away. Here we provide an overview of the cratering process, including ejecta formation and their subsequent dynamical evolution. We use different methodologies to model the physics of the problem, including smoothed particle hydrodynamics to model the cratering and ejecta formation process after the hypervelocity impact, N-body granular simulations to model early collisional processes between ejecta fragments right after cratering, and high-fidelity planetary propagation to model the dynamical evolution of ejecta during their purely ballistic phase. We highlight the key features of each phase and their role in defining the dynamical fate of ejecta. We investigate the effect of surface cohesion in the impacted target and identify the qualitative behavior of ejecta particles as a function of the key parameters of the problem. We provide quantitative estimates for the specific case study related to the DART–Dimorphos scenario and a selected range of target properties
Solar radiation pressure end-of-life disposal for Libration-point orbits in the elliptic restricted three-body problem
No full textThis paper proposes an end-of-life propellant-free disposal strategy for Libration-point orbits in the elliptic restricted three-body problem as an extension of a preliminary study performed in the circular problem. The spacecraft is initially disposed into the unstable manifold leaving the Libration-point orbit, before a reflective sun-pointing surface is deployed to enhance the effect of solar radiation pressure. This allows closing the pulsating zero-velocity curves at the pseudo Libration-point, SL2 such that, the consequent increase in energy prevents the spacecraft returning to Earth. An energy approach is used to compute the required area for the Hill’s curves closure at the pseudo Libration-point SL2, via numerical optimisation. The Gaia mission is selected as an example scenario since a low deployable area is required in the circular case. Guidelines for the end-of-life disposal of future Libration-point orbit missions are proposed
Comparison of Hamiltonian structure-preserving and Floquét mode station-keeping for Libration-point orbits
No full textLibration-point orbit (LPO) missions are often selected for study the Sun and our Universe. The effect of perturbations such as the gravitational effect of other planets and Solar Radiation Pressure (SRP) makes the LPO's environment highly unstable. Thus, station-keeping manoeuvre are required to keep the spacecraft close to its nominal trajectory and a novel idea is to use perturbations such as SRP for a propellant-free control system. A Hamiltonian-Structure Preserving (HSP) control, which exploits the natural dynamics, is selected since it requires low acceleration. The focus of this paper is to investigate the robustness of HSP; thus, a comparison with a similar approach such as the Floquét Mode (FM) is analysed to identify their main features. A sensitivity analysis by changing the HSP and FM controllers' parameter is done for SOHO's mission; while, an extension of the HSP control enhanced with SRP is investigated for high amplitude planar-Lyapunov and distant prograde orbits
- …
