meetings - Space Flight Mechanics Committee

in inclination and non-zero eccentricity. In this paper we examine the morphology of Earthto-Mars
porkchop plots as they vary from opportunity to opportunity and its implications on
trajectory design. These results are then compared to idealistic and optimized transfers.
Conclusions are drawn about “good” opportunities versus “bad” opportunities for different
mission applications.
10:45 AAS Derivative Analysis and Algorithm Modification of the Transverse-
13-227 Eccentricity-Based Lambert's Problem
Wen Changxuan, Beijing University of Aeronautics and Astronautics; Zhao Yushan,
Beijing University of Aeronautics and Astronautics; Shi Peng, Beijing University of
Aeronautics and Astronautics
Classical Lambert's problem can be parameterized and solved through the transverseeccentricity
component. A further study was conducted to analyze the problem
differentially and to modify the algorithms. Results show that the derivative of a direct
transfer is positive and continuous, which verifies the monotonically increasing relationship
between the transfer-time and the transverse eccentricity; however, the derivative of a
multi-revolution case increases from negative to positive, indicating that the transfer-time
decreases to the minimum firstly, and then increases to infinity. Simulations demonstrated
the better computational efficiency and faster convergence of our modified algorithm.
11:05 AAS Homotopy Method for Solving Minimum Consumption Orbit Transfer
13-228 Problem
Hao Huang, Beihang University; Chao Han, Beihang University
Minimum consumption orbit transfer problem always leads to bang-bang opti-mal control
problem, and difficult to solve with shooting methods. A homotopy approach is proposed to
deal with these difficulties. Scaling techniques, global search for initial costates and
modified RKF45 are combined with homotopy approach to reduce the searching space of
costates, increase the possibility to get the global solution, and improve the precision of
integration with discontinuous differential equations. A numerical example is solved to
illustrate the effective of the method.
11:25 AAS On-line Entry Trajectory Planning and Combined Prediction Guidance for
13-229 Lunar Return
Biao Zhao, Harbin Institute of Technology; Naigang Cui, Harbin Institute of
Technology; Jifeng Cuo, Harbin Institute of Technology; Ping Wang, China
Academy of Space Technology (CAST)
For the lunar return mission, a concern of the entry guidance requirement is the full flight
envelope applicability and landing accuracy control. The NPC method is not limited by the
validity of the approximations, simplifications and empirical assumptions necessary for any
analytical treatment, thus it holds greater potential to be more accurate and adaptive.
However, the NPC algorithms in the literatures which merely predict based on the terminal
condition cannot guarantee to meet the process constraints. To solve this problem, we
combine NPC method with an analytical constant drag acceleration method, and propose a
simple and effective integrated guidance.
23 rd AAS / AIAA Space Flight Mechanics Meeting Page 25