航天器交会快速接近机动策略

对航天器交会接近段V-bar上保持点间的转移,单向(轨道径向或周向)推力机动的最短转移时间为半个轨道周期(对应双径向推力冲量)。若要求转移时间小于半个轨道周期,须采用双向(径向与周向联合)推力。为此,提出5种机动方案:1)起点双向冲量与终点双向冲量机动;2)途中双向连续推力机动;3)起点双向冲量与途中双向连续推力机动;4)途中双向连续推力与终点双向冲量机动;5)起点切向冲量与途中径向连续推力及终点切向冲量机动(即直线路径转移)。其中,方案1)(冲量机动)的速度增量最小,但轨迹视界角最大;方案5)(直线路径)的视界角最小(近似为零),但当转移时间T>0.292P(P为轨道周期)时,所需的速度增量较大。机动方案的选择应全面考虑转移轨迹安全性、速度增量需求、转移轨迹视界角,以及机动复杂程度等多方面因素。若视界角可满足总体设计要求,宜选择方案1);当T<0.292P时,也可考虑方案5)。

Fast Transfer Maneuvers between Holding Points in the Closing Phase of Spacecraft Rendezvous

Fast transfer strategies between V-bar holding points for the closing phase of spacecraft rendezvous were investigated in terms of C-W solutions.Bidirectional thrusters have to be used to execute transfer between V-bar holding points within half of the orbital period.For this reason,five bidirectional-thrust maneuvers were presented: 1) bidirectional impulses at the beginning and end points,2) bidirectional continuous thrusts during the transfer,3) bidirectional impulses at the beginning point and bidirectional continuous thrusts during the transfer,4) bidirectional continuous thrusts during the transfer and bidirectional impulses at the end-point,5) tangential impulses at the beginning and end points and radial continuous thrust during the transfer(straight line transfer).All the five maneuvers have good safety.Their free-flight trajectories can not enter into the safety area centered at the mass center of the target vehicle in case that any maneuver thruster has failure.The bidirectional-impulse maneuver has the lowest velocity increment and the maximum visual angle.The straight line transfer has the visual angle equal to zero,but it consumes more propulsion when the transfer time T>0.292P(P is the orbital period).Thus,it's better to choose the bidirectional-impulse maneuver,if the visual angle can meet system design requirements.When the transfer time T<0.292P,the straight line transfer can be considered as an alternative.