Abstract Onboard computation of a fuel-optimal trajectory is an indispensable technology for future lunar and planetary missions with pinpoint landings. This paper proposes a throttled explicit guidance (TEG) scheme under bounded constant thrust acceleration. TEG is capable of achieving fuel-optimal large diversions with good accuracy and can find optimal solutions. Thus far, the TEG algorithm is unique as it offers an explicit and simultaneous search method for the fuel-optimal thrust direction and thrust magnitude switching in predictor-corrector iterations. Fast numerical search is realized with a straightforward computation of seven final states (position, velocity, and the Hamiltonian) from seven unknowns (six adjoint variables for position and velocity and one final time). In addition, global convergence capability is enhanced by implementing the damped Newton's method. A number of simulations of large diversions show the excellent convergence of the TEG algorithm within at most 15 iterations from a cold start. The experimental results of the runtime measurement of the TEG algorithm support its real-time feasibility on a flight processor. These features of the TEG are suitable for onboard guidance of pinpoint landings.

    Highlights Optimal guidance under bounded thrust acceleration is proposed for pinpoint landing. The proposed guidance scheme is named “throttled explicit guidance (TEG)”. TEG can find optimal thrust direction/switching and time of flight simultaneously. TEG iterates the prediction of final state errors and its correction. Excellent convergence and fast computation of TEG are verified by numerical tests.


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    Title :

    Throttled explicit guidance for pinpoint landing under bounded thrust acceleration


    Contributors:
    Ito, T. (author) / Sakai, S. (author)

    Published in:

    Acta Astronautica ; 176 ; 438-454


    Publication date :

    2020-06-07


    Size :

    17 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English





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