Download or read book Low Earth Orbit Trajectory Optimization in the Presence of Atmospheric Uncertainty written by Aaron Jay Brown and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The previous 20 to 25 years have seen a tremendous increase in space exploration, and with that an increase in the level of logistics planning needed to ensure mission success. For spacecraft that are designed to be periodically re-supplied, a key logistics consumable is propellant, as it constitutes the greatest up-mass on re-supply vehicles. A trajectory design strategy is therefore desired that minimizes propellant usage in order to ease the demand for propellant re-supply missions. This thesis develops such a strategy in three stages, and uses the International Space Station (ISS) as its testbed, as no other LEO spacecraft is more challenging from a space logistics standpoint. First, the ISS trajectory planning problem is formulated as a constrained burn optimization problem assuming a deterministic atmosphere. The cost function is total ∆v, with constraints imposed on longitude of ascending node (LAN) and semi-major axis (SMA) altitude. Analytic derivatives are constructed for both the cost and constraints, which are necessary given the 6-week to 2-year time frames being considered. A gradient-based optimizer is then utilized to find locally-optimal solutions to real-world ISS trajectory planning problems. Second, atmospheric uncertainty is addressed by constructing a probabilistic model of space weather data using Gaussian Processes (GPs). Bayesian inference is performed using the GP model to generate mean and covariance estimates for space weather predictions, whose pedigree is assessed against test data. The predictions are then mapped into atmospheric density via the analytic Jacchia-Roberts density model, and the effect of space weather uncertainty on orbital lifetime is examined. Third, an ISS burn execution uncertainty model is developed. This model, along with the space weather uncertainty model, are deployed in a linear covariance analysis to ascertain their combined effect on LAN and SMA altitude dispersions. The deterministic constraints from the original problem are re-formulated as stochastic constraints, where now the constraint uncertainty interval is required to fall within specified bounds. An updated optimization framework is constructed using the original ∆v cost function along with the stochastic constraints to solve the trajectory optimization problem under atmospheric uncertainty. Finally, the complete architecture is summarized for deployment in an operational setting

Download or read book Gamma Guidance of Trajectories for Coplanar Aeroassisted Orbital Transfer written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-11-07 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: The optimization and guidance of trajectories for coplaner, aeroassisted orbital transfer (AOT) from high Earth orbit (HEO) to low Earth orbit (LEO) are examined. In particular, HEO can be a geosynchronous Earth orbit (GEO). It is assumed that the initial and final orbits are circular, that the gravitational field is central and is governed by the inverse square law, and that at most three impulses are employed: one at HEO exit, one at atmospheric exit, and one at LEO entry. It is also assumed that, during the atmospheric pass, the trajectory is controlled via the lift coefficient. The presence of upper and lower bounds on the lift coefficient is considered. First, optimal trajectories are computed by minimizing the total velocity impulse (hence, the propellant consumption) required for AOT transfer. The sequential gradient-restoration algorithm (SGRA) is used for optimal control problems. The optimal trajectory is shown to include two branches: a relatively short descending flight branch (branch 1) and a long ascending flight branch (branch 2). Next, attention is focused on guidance trajectories capable of approximating the optimal trajectories in real time, while retaining the essential characteristics of simplicity, ease of implementation, and reliability. For the atmospheric pass, a feedback control scheme is employed and the lift coefficient is adjusted according to a two-stage gamma guidance law. Further improvements are possible via a modified gamma guidance which is more stable with respect to dispersion effects arising from navigation errors, variations of the atmospheric density, and uncertainties in the aerodynamic coefficients than gamma guidance trajectory. A byproduct of the studies on dispersion effects is the following design concept. For coplaner aeroassisted orbital transfer, the lift-range-to-weight ratio appears to play a more important role than the lift-to-drag ratio. This is because the lift-range-to-weight ratio controls mainly the minimum al...

Download or read book Spacecraft Trajectory Optimization written by Bruce A. Conway and published by Cambridge University Press. This book was released on 2010-08-23 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a long-overdue volume dedicated to space trajectory optimization. Interest in the subject has grown, as space missions of increasing levels of sophistication, complexity, and scientific return - hardly imaginable in the 1960s - have been designed and flown. Although the basic tools of optimization theory remain an accepted canon, there has been a revolution in the manner in which they are applied and in the development of numerical optimization. This volume purposely includes a variety of both analytical and numerical approaches to trajectory optimization. The choice of authors has been guided by the editor's intention to assemble the most expert and active researchers in the various specialities presented. The authors were given considerable freedom to choose their subjects, and although this may yield a somewhat eclectic volume, it also yields chapters written with palpable enthusiasm and relevance to contemporary problems.

Download or read book An Iterative LQR Method for Addressing Model Uncertainty in the Mars Entry Problem written by Allegra Farrar and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the moon landing in 1969 sounded the proverbial shotgun inciting efforts to expand the frontiers of space exploration, there has been unparalleled effort to enhance the technologies for doing so. While human presence in Earth orbit has boomed over the past decade, crewed planetary missions have yet to reach desired goals. Set by NASA as the future destinations beyond Earth orbit, Mars presents significant challenges to the entry, landing and descent sequence. Missions including sample return and human exploration require precise landing accuracy. Additionally, entry vehicle dynamics and atmospheric parameters at time of flight are hard to predict. This along with the advancement of mission objectives invoke the need for a reliable, robust, and computationally reasonable method with certifiable guarantees of safe landing. Therefore, this paper presents a closed-loop trajectory optimizer capable of incorporating the atmospheric models and navigational data uncertainty for the nonlinear dynamics of hypersonic entry by applying an iterative Linear-Quadradic-Regulator (iLQR). iLQR is an efficient and powerful method for trajectory optimization derived from Differential Dynamic Programming (DDP) principles, which have been applied successfully in cases of robotic movement to locally improve upon a single trajectory through second-order convergence for a local optimal trajectory. iLQR takes this method a step further by iteratively linearizing the system dynamics, converging to determine an optimal trajectory by minimizing the performance cost and the uncertainty in the dynamics model. To demonstrate its effectiveness, the algorithm will be tested against a series of realistic simulations to test the model performance against mission requirements, such as high altitude and precision landing. Results show an efficient data-driven algorithm capable of learning how to successfully control a 40 ton crewed-scale spacecraft for Mars entry under dynamical uncertainties in the state model. Additionally, given system performance parameters, the covariance, or landing accuracy, of the final position can be determined from the algorithm and the results can be used to determine safe parameter ranges that achieve the desired accuracy

Download or read book Trajectory Optimization for Spacecraft Collision Avoidance written by Air Force Institute of Technology and published by CreateSpace. This book was released on 2014-08-21 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last several decades have resulted in an unfortunate byproduct of space exploration and development: orbital debris. Satellites in Low Earth Orbit have been required to make an ever increasing number of course corrections in order to avoid collisions. Despite efforts to the contrary, collisions continue to occur, each time creating additional debris and increasing the requirement for the remaining satellites to maneuver. Every required maneuver decreases a satellite's service life. The purpose of this study is to develop a minimum thrust profile to maneuver an orbiting satellite out of its projected error ellipse before a collision occurs. For comparison, both the impulsive and continuous thrust cases were considered as well as in-plane versus out-of plane maneuvering. This study made use of the Radau Pseudospectral Method to develop this minimum thrust profile. This method was run in MATLAB(r) using General Pseudospectral Optimal Control Software (GPOPS-II). Once the optimal solution was obtained, Systems Tool Kit(r) was used to simulate the resulting calculated trajectories and confirm avoidance of the error ellipse.

Download or read book Design of Trajectory Optimization Approach for Space Maneuver Vehicle Skip Entry Problems written by Runqi Chai and published by Springer. This book was released on 2019-07-30 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores the design of optimal trajectories for space maneuver vehicles (SMVs) using optimal control-based techniques. It begins with a comprehensive introduction to and overview of three main approaches to trajectory optimization, and subsequently focuses on the design of a novel hybrid optimization strategy that combines an initial guess generator with an improved gradient-based inner optimizer. Further, it highlights the development of multi-objective spacecraft trajectory optimization problems, with a particular focus on multi-objective transcription methods and multi-objective evolutionary algorithms. In its final sections, the book studies spacecraft flight scenarios with noise-perturbed dynamics and probabilistic constraints, and designs and validates new chance-constrained optimal control frameworks. The comprehensive and systematic treatment of practical issues in spacecraft trajectory optimization is one of the book’s major features, making it particularly suited for readers who are seeking practical solutions in spacecraft trajectory optimization. It offers a valuable asset for researchers, engineers, and graduate students in GNC systems, engineering optimization, applied optimal control theory, etc.

Download or read book Ithaca N Y written by and published by . This book was released on 1916* with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atmospheric and Near Planet Trajectory Optimization by the Variational Steepest Descent Method written by and published by . This book was released on 1970 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Trajectory Optimization of Low Thrust Interplanetary and Earth Orbit Transfers written by Brittanny Victoria Holden and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: multi-domain Legendre-Gauss-Radau quadrature collocation is used. Key results obtained in this study include not only the number of switches in the optimized thrust, but also the total impulse. In particular, as the maximum allowable thrust acceleration decreases, it is found that the total impulse is lower when compared with a previous study where a burn-off-burn thrusting structure was assumed a priori. For each type of transfer, a particular value of maximum allowable thrust acceleration is chosen to highlight in more detail the key features of the optimal solutions. The results of this study provide improved insight into the optimal thrusting structure required in order to achieve each type of orbital transfer relative to a previous study on a similar problem.

Download or read book Trajectory Optimization with Earth Orbit Prediction and Re entry Considerations written by M. A. Connor and published by . This book was released on 1966 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1985 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimal Space Trajectories written by Jean Pierre Marec and published by . This book was released on 1979 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimization of Low thrust Spacecraft Trajectories by Direct Shooting Methods microform written by Christopher Rampersad and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: The direct approach for trajectory optimization was found to be very robust. For most problems, solutions were obtained even with poor initial guesses for the controls. The direct approach was also found to be only slightly less accurate than the indirect methods found in the literature (within 0.7%). The present study investigates minimum-time and minimum-fuel low-thrust trajectory problems via a single shooting direct method. Various Earth-based and interplanetary case studies have been examined and have yielded good agreement with similar cases in the literature. Furthermore, new near-optimal trajectory problems have been successfully solved. A multiple-orbit thrust parameterization strategy was also developed to solve near-optimal very-low-thrust Earth-based transfers. Lastly, this thesis examines the use of the high-accuracy complex-step derivative approximation method for solving low-thrust transfer problems. For certain very nonlinear transfer problems, the complex-step derivative approximation was found to increase the robustness of the single shooting direct method.

Download or read book 30th Aerospace Sciences Meeting and Exhibit 92 0720 92 0758 written by and published by . This book was released on 1992 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reduced order Atmospheric Density Modeling for LEO Satellite Orbital Reentry Prediction written by Nicolette LeAnn Clark and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric density modeling and uncertainty quantification for fast and accurate orbit propagation are vital to drag force estimation for satellite reentry prediction and conjunction assessment in today's increasingly cluttered Low Earth Orbit (LEO) environment. Current density models can be computationally expensive, and often contain large errors, which make density modeling a leading cause of uncertainty in drag estimation. Reduced-order atmospheric density Models (ROMs) have shown potential to provide good predictive performance at a significantly lower computational cost, by propagating a low-dimensional representation of the atmospheric density state instead of the entire density state. In this thesis, ROMs were implemented in a high-fidelity orbital propagator and tested on the problem of reentry modeling for LEO objects. First, uncertainty quantification was performed on a test case for three significant sources of uncertainty in reentry modeling to compare the impact of uncertainty from initial state, ballistic coefficient, and space weather indices on residual lifetime estimation. These results highlighted features of interest in ROM behavior relative to empirical models. Second, ROMs were used to predict reentry of three LEO object test cases. ROMs were found to provide residual lifetime estimation performance comparable to current empirical models such as JB2008 and NRLMSISE-00, with a run time reduction of up to 70\% compared to the empirical models. ROMs were especially effective for longer predictions starting two or more days prior to LEO object reentry, where in some cases ROMs outperformed both empirical models while saving hours of run time. These findings validate the utility of ROMs for orbit propagation applications such as reentry prediction.

Download or read book Fuel Optimal Trajectories of Aeroassisted Orbital Transfer with Plane Change written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-07 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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...