Minimum-time low thrust orbit transfers using the method of particular solutions

Robyn M. Woollands, Julie L. Read, John L. Junkins

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We have developed a method for solving the minimum-time, constant, continuous low thrust, near circular-to-circular transfers using the method of particular solutions and collocation. The first step is to compute a sub-optimal solution by iteratively solving for the coefficients of the Chebyshev polynomials that parameterize the steering angle of the control vector. This unique implementation of minimum norm direct optimization is attractive in that it does not require partial derivatives, yet we have shown that we can accommodate a relatively high dimensional parameterization of the control variables. Once the sub-optimal solution has been obtained it is used as an initial guess to "warm start" a collocation algorithm. The collocation algorithm is simply used to generate a low fidelity solution for the costates (about 4 digit accuracy) that is fed as an initial guess to start the method of particular solutions shooting method. This low fidelity collocation solution is computed using finite difference derivatives and only a few iterations (and expensive matrix inversions) are required to produce an adequate initial guess. The method of particular solutions, which does not require partial derivatives to be computed or propagated, is extremely efficient and is used to solve the state/costate two-point boundary value problem by iterating on the initial costates that converge to a solution that satisfies the final boundary conditions in the minimum time-of-flight. One approach for solving a minimum-time problem is to map time onto the fixed domain from 0 to 1, and append a trivial differential equation to the set of state equations that integrates to give an unknown free constant (final time). Since our basis functions are the orthogonal Chebyshev polynomials, we map time onto the domain from -1 to 1 where Chebyshev polynomials exist, and thus our algorithm minimizes time-of-flight while converging to the optimal minimum-time solution. We demonstrate the capability of our algorithm by computing an example orbit transfer from a medium Earth orbit (a = 26,000 km) to rendezvous with a piece of debris in a geostationary orbit.

Original languageEnglish (US)
Title of host publicationSpaceflight Mechanics 2017
EditorsJon A. Sims, Frederick A. Leve, Jay W. McMahon, Yanping Guo
PublisherUnivelt Inc.
Pages675-686
Number of pages12
ISBN (Print)9780877036371
StatePublished - 2017
Externally publishedYes
Event27th AAS/AIAA Space Flight Mechanics Meeting, 2017 - San Antonio, United States
Duration: Feb 5 2017Feb 9 2017

Publication series

NameAdvances in the Astronautical Sciences
Volume160
ISSN (Print)0065-3438

Other

Other27th AAS/AIAA Space Flight Mechanics Meeting, 2017
Country/TerritoryUnited States
CitySan Antonio
Period2/5/172/9/17

ASJC Scopus subject areas

  • Aerospace Engineering
  • Space and Planetary Science

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