Near Earth Asteroids have a possibility of impacting with the Earth and always have a thread on the Earth. This paper proposes a way of changing the trajectory of the asteroid to avoid the impaction. Solar sail evolving in a H-reversal trajectory is utilized for asteroid deflection. Firstly, the dynamics of solar sail and the characteristics of the H-reversal trajectory are analyzed. Then, the attitude of the solar sail is optimized to guide the sail to impact with the object asteroid along a H-reversal trajectory. The impact velocity depends on two important parameters: the minimum solar distance along the trajectory and lightness number. A larger lightness number and a smaller solar distance lead to a higher impact velocity. Finally, the deflection capability of a solar sail impacting with the asteroid along the H-reversal is discussed. The results show that a 10 kg solar sail with a lead-time of one year can move Apophis out of a 600-m keyhole area in 2029 to eliminate the possibility of its resonant return in 2036.
Asteroid Disruption and Deflection Simulations for Multi-Modal Planetary Defense
University of California - Santa Barbara（加州大学圣塔芭芭拉分校）；NASA Ames Research Center（美国国家航空航天局艾姆斯研究中心）；University of New Mexico（新墨西哥大学）；New Mexico Institute of Mining and Technology（新墨西哥矿业理工学院）；Johns Hopkins University Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）；Sandia National Laboratories（桑迪亚国家实验室）
Exoplanetary Tour Design with Solar Sails: TheAntipodes Results in the GTOC13 Problem
Te Pūnaha Ātea – Space Institute, University of Auckland（奥克兰大学太空研究所）；Beijing Institute of Technology（北京理工大学）；University of Illinois Urbana-Champaign（伊利诺伊大学厄巴纳-香槟分校）
彗星撞击对地球上的生命构成长期危害。对撞击减缓技术进行了广泛的研究，但这些技术往往侧重于小行星转向。典型的小行星拦截计划包括航天器物理拦截目标，这一任务只适用于提前几十年确定的目标，并且在狭窄的轨道范围内-威胁彗星不太可能满足的标准。然而，彗星自然会受到纯粹引力轨道的扰动，这是通过太阳对其表面的加热来激活升华驱动的喷流。对彗星的人工加热，例如激光，可以补充太阳的自然加热，以有目的地操纵其路径，从而避免撞击。偏转的有效性取决于彗星的加热反应，这取决于包括核大小，轨道和动力学历史在内的因素。这些因素被纳入一个数值轨道模型，以评估在地球轨道和地面使用高功率激光阵列进行彗星偏转的有效性和可行性。模拟结果表明，一个衍射受限的500 m轨道或地面激光器阵列在1年内每天1%的时间以10 GW的速度运行，足以完全避免一颗典型的直径为500 m、主要非引力参数A1 = 2 x 10^-8 au d^-2的彗星的撞击。还讨论了在偏转过程中避免彗星碎裂的策略。
Enabling tomorrow's planetary defence and space resource economy: Autonomous fleet-based asteroid rendezvous missions
University of Liverpool（利物浦大学）；NASA（美国国家航空航天局）；Colorado Center for Astrodynamics, University of Colorado（科罗拉多大学轨道动力学中心）；Institute of Space and Astronautical Science (ISAS), JAXA（宇宙科学研究所 (ISAS)，日本宇宙航空研究开发机构）
