Earth-to-Moon missions with low thrust-to-weight ratios present unique challenges for exoatmospheric guidance,and the existing algorithms are ineffective for the unprecedentedly long burn arcs and high orbital eccentr...Earth-to-Moon missions with low thrust-to-weight ratios present unique challenges for exoatmospheric guidance,and the existing algorithms are ineffective for the unprecedentedly long burn arcs and high orbital eccentricities.To address these challenges,a Long Burn Arc Powered Explicit Guidance(LBA-PEG)algorithm is developed and compared with the existing algorithms.In the proposed LBA-PEG algorithm,a fully numerical thrust prediction method is developed to accurately predict the highly nonlinear thrust effects over long burn arcs.Moreover,a real-time Newton correction method is proposed to correct the orbit injection point,remedying the position-velocity coupling induced by high orbital eccentricities.The comparison between the proposed algorithm and the existing algorithm shows that the proposed algorithm surpasses the existing ones by significantly enhancing fuel efficiency and improving tolerance to thrust decrease.The proposed LBA-PEG algorithm can adapt to a 65%thrust decrease,which is 12%–22%larger than that of the existing algorithms,and it can still reliably converge and complete the guidance mission even when the length of the burn arc exceeds 90°.The proposed LBA-PEG highlights the algorithm's adaptability for long burn arc missions,especially in critical scenarios such as manned Earth-to-Moon missions.展开更多
In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmosphe...In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmospheric interception, because the proposed guidance laws give full consideration to the effect of gravity, they consume much less fuel than the traditional guidance laws while requiring a light computational load. In the development of the guidance laws, a unified optimal guidance problem is put forward, where the final velocity vector constraint can be considered or neglected by properly adjusting a parameter in the cost function. To make this problem analytically solvable, a linear model is used to approximate the gravity difference, the difference of the gravitational accelerations of the target and interceptor. Additionally, an example is provided to show that some achievements of this study can be used to significantly improve the fuel efficiency of the pulsed guidance employed by the interceptor whose divert thrust level is fixed. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.展开更多
文摘Earth-to-Moon missions with low thrust-to-weight ratios present unique challenges for exoatmospheric guidance,and the existing algorithms are ineffective for the unprecedentedly long burn arcs and high orbital eccentricities.To address these challenges,a Long Burn Arc Powered Explicit Guidance(LBA-PEG)algorithm is developed and compared with the existing algorithms.In the proposed LBA-PEG algorithm,a fully numerical thrust prediction method is developed to accurately predict the highly nonlinear thrust effects over long burn arcs.Moreover,a real-time Newton correction method is proposed to correct the orbit injection point,remedying the position-velocity coupling induced by high orbital eccentricities.The comparison between the proposed algorithm and the existing algorithm shows that the proposed algorithm surpasses the existing ones by significantly enhancing fuel efficiency and improving tolerance to thrust decrease.The proposed LBA-PEG algorithm can adapt to a 65%thrust decrease,which is 12%–22%larger than that of the existing algorithms,and it can still reliably converge and complete the guidance mission even when the length of the burn arc exceeds 90°.The proposed LBA-PEG highlights the algorithm's adaptability for long burn arc missions,especially in critical scenarios such as manned Earth-to-Moon missions.
文摘In this study, two optimal terminal guidance (OTG) laws, one of which takes into account the final velocity vector constraint, are developed for exoatmospheric interception using optimal control theory. In exoatmospheric interception, because the proposed guidance laws give full consideration to the effect of gravity, they consume much less fuel than the traditional guidance laws while requiring a light computational load. In the development of the guidance laws, a unified optimal guidance problem is put forward, where the final velocity vector constraint can be considered or neglected by properly adjusting a parameter in the cost function. To make this problem analytically solvable, a linear model is used to approximate the gravity difference, the difference of the gravitational accelerations of the target and interceptor. Additionally, an example is provided to show that some achievements of this study can be used to significantly improve the fuel efficiency of the pulsed guidance employed by the interceptor whose divert thrust level is fixed. (C) 2016 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.
