Author: Daniel Edward Gill (CAPT, USAF.)Publisher:
ISBN:
Category : Artificial satellites
Languages : en
Pages : 212
Book Description
Improved Initial Value Estimates for Minimum-fuel Orbital Transfers
Author: Daniel Edward Gill (CAPT, USAF.)Publisher:
ISBN:
Category : Artificial satellites
Languages : en
Pages : 212
Book Description
Improved Initial Value Estimates for Minimum-Fuel Orbital Transfers
Author: Daniel E. GillPublisher:
ISBN:
Category :
Languages : en
Pages : 226
Book Description
A method is developed for computing improved initial-value estimates for minimum-fuel transfer trajectories between coplanar, elliptic orbits with a thrust-limited, variable-mass rocket moving in an inverse square-law gravitational field. The initial and final orbits are specified by their eccentricities, semilateral recta and arguments of pericenter and the entire transfer consists of two finite-thrust phases. Estimates for the parameters of the optimal transfer trajectory are provided by the two-impulse solution and the techniques presented in this study provide good estimates for the unknown initial values of unspecified control, state and adjoint variables which are required to successfully compute the minimum-fuel transfer trajectory between specified orbits. (Author).
A Collection of Technical Papers
Author: MINIMUM-FUEL THRUST-LIMITED TRANSFER TRAJECTORIES BETWEEN COPLANAR ELLIPTIC ORBITS.
Author: Edward Adolph KernPublisher:
ISBN:
Category : Elliptical orbits
Languages : en
Pages : 172
Book Description
A method is developed for the efficient computation of minimum-fuel transfer trajectories between coplanar elliptic orbits with a thrust-limited variable-mass rocket moving in a central gravitation force field. Each orbit is defined through the eccentricity, semi-latus rectum, and argument of pericenter. Transfer time is left open. The minimum-fuel trajectory is assumed to consist of two thrusting phases separated by a coasting phase. Computation of the minimum-fuel transfer trajectory is accomplished by a direct integration of the rocket equations of motion and the associated adjoint equations which are developed from variational calculus techniques. This direct approach is made possible by a unique transformation of the adjoint equations into a set of equations which provide a much better understanding of the general behavior of minimum-fuel transfer trajectories. Reasonable estimates of the thrusting interval durations, initial thrust angle, and initial true anomaly are derived from the corresponding minimum-fuel, two-impulse transfer trajectory. The initial value of a newly discovered variable is used in conjunction with the initial thrust angle to obtain the thrusting interval durations specified by the two-impulse transfer. (Author).
Minimum-fuel Transfers Between Coaxial Orbits, Both Coplanar and Concoplanar
Author: Stanford University. Department of Aeronautics and AstronauticsPublisher:
ISBN:
Category :
Languages : en
Pages : 136
Book Description
Minimum Fuel Continuous Low Thrust Orbital Transfer
Author: Eugene A. SmithPublisher:
ISBN:
Category :
Languages : en
Pages : 93
Book Description
Minimum fuel continuous low thrust orbit transfer is an optimal control problem which requires the application of iterative numerical methods to solve the resulting two point boundary value problem. A combination gradient- neighboring extremal algorithm gives accurate results when both the initial and terminal orbits are coplanar. These results are then used to extend the problem to include out-of-plane transfers between orbits of widely varying inclination. Control histories, in terms of thrust direction, are plotted as a function of time for both coplanar and non-coplanar transfers. Steering programs for coplanar transfers are characterized by a rapid thrust reversal which is dependent on eccentricity for the time of its occurrence. In the latter case, out-of-plane thrusting is primarily a function of the inclination change between orbits. On the basis of these results, the particular numerical approach used provides an effective method for generating optimal low thrust orbital transfer guidance.
Master's Theses and Doctoral Dissertations in the Pure and Applied Sciences
Author: Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 172
Book Description
Fuel-Optimal Trajectories of Aeroassisted Orbital Transfer with Plane Change
Author: National Aeronautics and Space Administration (NASA)Publisher: Createspace Independent Publishing Platform
ISBN: 9781722410049
Category :
Languages : en
Pages : 64
Book Description
The problem of minimization of fuel consumption during the atmospheric portion of an aeroassisted, orbital transfer with plane change is addressed. The complete mission has required three characteristic velocities, a deorbit impulse at high earth orbit (HEO), a boost impulse at the atmospheric exit, and a reorbit impulse at low earth orbit (LEO). A performance index has been formulated as the sum of these three impulses. Application of optimal control principles has led to a nonlinear, two-point, boundary value problem which was solved by using a multiple shooting algorithm. The strategy for the atmospheric portion of the minimum-fuel transfer is to start initially with the maximum positive lift in order to recover from the downward plunge, and then to fly with a gradually decreasing lift such that the vehicle skips out of the atmosphere with a flight path angle near zero degrees. Naidu, Desineni Subbaramaiah and Hibey, Joseph L. Unspecified Center...
Optimum Low Thrust Elliptic Orbit Transfer Using Numerical Averaging
Author: Zahi Bassem TarziPublisher:
ISBN:
Category :
Languages : en
Pages : 119
Book Description
Low-thrust electric propulsion is increasingly being used for spacecraft missions primarily due to its high propellant efficiency. Since analytical solutions for general low-thrust transfers are not available, a simple and fast method for low-thrust trajectory optimization is of great value for preliminary mission planning. However, few low-thrust trajectory tools are appropriate for preliminary mission design studies. The method presented in this paper provides quick and accurate solutions for a wide range of transfers by using numerical orbital averaging to improve solution convergence and include orbital perturbations. Thus allowing preliminary trajectories to be obtained for transfers which involve many revolutions about the primary body. This method considers minimum fuel transfers using first order averaging to obtain the fuel optimum rates of change of the equinoctial orbital elements in terms of each other and the Lagrange multipliers. Constraints on thrust and power, as well as minimum periapsis, are implemented and the equations are averaged numerically using a Gaussian quadrature. The use of numerical averaging allows for more complex orbital perturbations to be added without great difficulty. Orbital perturbations due to solar radiation pressure, atmospheric drag, a non-spherical central body, and third body gravitational effects have been included. These perturbations have not ben considered by previous methods using analytical averaging. Thrust limitations due to shadowing have also been considered in this study. To allow for faster convergence of a wider range of problems, the solution to a transfer which minimizes the square of the thrust magnitude is used as a preliminary guess for the minimum fuel problem. Thus, this method can be quickly applied to many different types of transfers which may include various perturbations. Results from this model are shown to provide a reduction in propellant mass required over previous minimum fuel solutions. Minimum time transfers are also solved and compared to minimum fuel.
Author: