23 research outputs found
Low-Thrust Earth-Venus Trajectories
No full textChapter 6, by Alessandro A. Quarta, Giovanni Mengali and Generoso Aliasi, discusses the simulation results involving the minimum-time trajectories for an Earth-Venus mission transfer using a spacecraft with an electric propulsion system, with both a nuclear and a solar electric power source. The analysis has been performed in a parametric way as a function of some design parameters, such as the available thruster electric power and the initial in-flight mass. Various models have been considered to describe the propulsion system behavior with different levels of
approximations and obtain increasingly refined information about the mission performance. Some simplifying assumptions have been introduced in order to make the mathematical problem tractable, to reduce the simulation time and guarantee a thorough parametric investigation of the mission performance. The analysis performed in this chapter is useful to obtain a first order estimate of the mission requirements as a function of the specific thruster characteristics
Special Orbits for Mercury Observation
No full textChapter 5, by Generoso Aliasi, Giovanni Mengali and Alessandro A. Quarta, deals with an advanced scientific mission concept in which the existence of suitable positions for the observation and the measurement of the Mercury’s magnetotail are investigated. The scientific mission is based on the use of artificial equilibrium points in the elliptic three-body system, constituted by the Sun, Mercury, and a spacecraft, which is modeled as a massless point. The spacecraft motion in the Sun–Mercury system is first discussed under the assumption that the propulsion
system provides a radial continuous thrust with respect to the Sun. In particular, the spacecraft is assumed to have a generalized sail as its primary propulsion system. A generalized sail models the performance of different types of advanced propulsion systems, including a (photonic) solar sail, an electric solar wind sail and an electric thruster, by simply modifying the value of a thrusting parameter. The location of the artificial equilibrium points is derived, and their stability is also investigated. It is shown that that collinear artificial equilibrium points are always
unstable, except for a range of L2-type points which are placed far away from Mercury. A similar result is obtained for triangular equilibrium points. A control strategy is introduced to maintain the spacecraft in the neighborhood of an artificial equilibrium point. In this context, a simple and effective way to actively control the spacecraft dynamics is by means of a Proportional-Integral-Derivative feedback control law. The latter control law is finally employed in the magnetotail mission scenario, whose fundamental idea is to continuously and slowly displacing the
artificial equilibrium point along the Sun–Mercury direction. Numerical simulations show the effectiveness of the proposed mission strategy
Electric Solar Wind Sail Optimal Transit in the Circular Restricted Three Body Problem
No full textThis paper analyzes the transfer orbits within a Sun-[Earth+Moon] system for a spacecraft whose primary propulsion system is an Electric Solar Wind Sail. The planetary system is approximated
through the Circular Restricted Three Body Problem and the spacecraft motion is studied in an optimal framework in which the performance index is the flight time. Minimum time transfers are studied using an indirect approach, and the optimal control law is found in analytical form as a function of the problem parameters. Optimal transfers between equilibrium points are discussed and interesting symmetries in the spacecraft trajectories are pointed out along with an analytical proof of their existence. A mission scenario consistent with the Geostorm concept is analyzed and the effectiveness of the propulsion system is emphasized for missions involving a tour through a subset of the classical Lagrangian points
Artificial Equilibrium Points for Electric Sail with Constant Attitude
No full textCreating and maintaining Artificial Equilibrium Points (AEPs) in the restricted threebody problem is a challenging mission scenario in which a propellantless propulsion system exploits its natural potential. Indeed, in such a problem the acceleration resulting from the sum of centrifugal and gravitational forces can be balanced, for a theoretically unlimited time period, by means of a suitable continuous propulsive thrust.
A thorough analysis involving the location and stability of AEPs has been addressed in a recent paper, under the assumption that the propulsion system provides a purely radial thrust with respect to the Sun, and the thrust modulus is a function of the Sun-spacecraft distance only . In that way, with a unified mathematical model, it is possible to analyze the performance of different propulsion systems, as, for example, a photonic solar sail and an
Electric Solar Wind Sail (E-Sail). In particular, an E-Sail is known to be able to provide a continuous propulsive acceleration by means of Coulomb’s interaction of a number of positively charged tethers with the solar wind plasma stream
Optimal Control Laws for Heliocentric Transfers with a Magnetic Sail
No full textA magnetic sail is an advanced propellantless propulsion system that uses the interaction between the solar wind and an artificial magnetic field generated by the spacecraft, to produce a propulsive thrust in interplanetary space. The aim of this paper is to collect the available experimental data, and the simulation results, to develop a simplified mathematical model that describes the propulsive acceleration of a magnetic sail, in an analytical form, for mission analysis purposes. Such a mathematical model is then used for estimating the performance of a magnetic sail-based spacecraft in a two-dimensional, minimum time, deep space mission scenario. In particular, optimal and locally optimal steering laws are derived using an indirect approach. The obtained results are then applied to a mission analysis involving both an optimal Earth-Venus (circle-to-circle) interplanetary transfer, and a locally optimal Solar System escape trajectory. For example, assuming a characteristic acceleration of 1 mm/s(2), an optimal Earth-Venus transfer may be completed within about 380 days
Artificial Periodic Orbits Around L1-Type Equilibrium Points for a Generalized Sail
No full textThe contribution of this note is to extend the available results for APOs maintained by a propellantless propulsion system to the case of purely radial (continuous) propulsive acceleration, whose modulus depends on a given power of the Sun–spacecraft distance
A Graphical Approach to Electric Sail Mission Design with Radial Thrust
No full textThis paper describes a semi-analytical approach to electric sail mission analysis under the assumption that the spacecraft experiences a purely radial, outward, propulsive acceleration. The problem is tackled by means of the potential well concept, a very effective idea that was originally introduced by Prussing and Coverstone in 1998. Unlike a classical procedure that requires the numerical integration of the equations of motion, the proposed method provides an estimate of the main spacecraft trajectory parameters, as its maximum and minimum attainable distance from the Sun, with the simple use of analytical relationships and elementary graphs. A number of mission scenarios clearly show the effectiveness of the proposed approach. In particular, when the spacecraft parking orbit is either circular or elliptic it is possible to find the optimal performances required to reach an escape condition or a given distance from the Sun. Another example is given by the optimal strategy required to reach a heliocentric Keplerian orbit of prescribed orbital period. Finally the graphical approach is applied to the preliminary design of a nodal mission toward a Near Earth Asteroid
Artificial Lagrange Points for Solar Sail with Electrochromic Material Panels
No full textThe aim of this Note is to explore the capabilities of the emerging EMP technology for the active stabilization of L1-type AEPs using a square solar sail with a fixed attitude. The problem is addressed within an elliptic restricted framework, which is a more realistic model with respect to the classical circular case [4]. The main spacecraft parameters, including the sail side and the total spacecraft mass, are defined, by means of a simplified mathematical model, as a function of the main mission requirements in terms of maximum allowed sail lightness number variation and AEP position
