In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi...In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi-body dynamics, considering the gravitational forces of the Sun, Earth, and Moon. It is proposed that an electric-propulsion spacecraft initially parking in a circular 200-kin-altitude low Earth orbit is expected to rendezvous with an asteroid and carry as much sample as possible back to the Earth in a 10-year time frame. The team from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences has reported a solution with an asteroid sample mass of 328 tons, which is ranked first in the competition. In this article, we will present our design and optimization methods, primarily including overall analysis, target selection, escape from and capture by the Earth-Moon system, and optimization of impulsive and low-thrust trajectories that are modeled in multi-body dynamics. The orbital resonance concept and lunar gravity assists are considered key techniques employed for trajectory design. The reported solution, preliminarily revealing the feasibility of returning a hundreds-of-tons asteroid or asteroid sample, envisions future space missions relating to near-Earth asteroid exploration.展开更多
为充分利用广域测量系统WAMS(wide area measurement system)信息实现电力系统暂态稳定性快速在线识别,提出一种基于实测响应轨迹稳定边界的暂态不稳定识别方法.根据单机"位能脊"推导了单机-无穷大系统在相平面上的暂态稳定边...为充分利用广域测量系统WAMS(wide area measurement system)信息实现电力系统暂态稳定性快速在线识别,提出一种基于实测响应轨迹稳定边界的暂态不稳定识别方法.根据单机"位能脊"推导了单机-无穷大系统在相平面上的暂态稳定边界;证明单机无穷大系统任意比例剖分点处,由扰动能与电压相角构成的平面上的轨迹与相平面轨迹具有相似的几何特征,为间接利用发电机端口外网络测量信息识别电力系统暂态不稳定性提供了依据;证明了临界机组对的相轨迹上二阶导数等于零的点构成了系统的不返回边界,提出用临界机组对的相轨迹几何特征来识别系统暂态稳定性.为避免判据在线应用时受参数及不确定性干扰可能造成误判,对判据进行了实用性改进.利用PSASP 6.28 WEPRI 36节点仿真算例验证了所提判据的有效性.展开更多
基金supported by the National Natural Science Foundation of China(Grant11372311)the grant from the State key Laboratory of Astronautic Dynamics(2014-ADL-DW0201)
文摘In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi-body dynamics, considering the gravitational forces of the Sun, Earth, and Moon. It is proposed that an electric-propulsion spacecraft initially parking in a circular 200-kin-altitude low Earth orbit is expected to rendezvous with an asteroid and carry as much sample as possible back to the Earth in a 10-year time frame. The team from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences has reported a solution with an asteroid sample mass of 328 tons, which is ranked first in the competition. In this article, we will present our design and optimization methods, primarily including overall analysis, target selection, escape from and capture by the Earth-Moon system, and optimization of impulsive and low-thrust trajectories that are modeled in multi-body dynamics. The orbital resonance concept and lunar gravity assists are considered key techniques employed for trajectory design. The reported solution, preliminarily revealing the feasibility of returning a hundreds-of-tons asteroid or asteroid sample, envisions future space missions relating to near-Earth asteroid exploration.
