空间碎片发动机加速机理研究

We present a design concept for a space engine that can continuously remove orbital debris by using the debris powder as a propellant. Space debris represents a great potential threat to operational satellites, especially certain high-value spaceships. With the increasing risk of debris, researches reveal that it would reach a phenomenon named the Kessler syndrome that numerous operational satellites being destroyed in a chain reaction in low orbit in the not-far distant future. Initiative removing enough of the debris for the safety of space flight is an inevitable problem for human. Major space organizations are monitoring debris constantly with space debris environment models. At the same time, researchers have proposed a series of methods for removing the debris, such as using electrically conductive tethers to deorbit the debris, using robots with claws, nets or gecko-like suction cups to capture the debris and deploying ground-based or space-based laser to deorbit the debris. Nevertheless, large consumption of fuel for orbital transfer especially noncoplanar, chasing and rendezvousing with the debris is the leading restricting factor. In the concept of debris engine, a robotic space cleaner is used to capture the targeted debris and transfer it to the engine. Large debris is firstly disintegrated into small pieces with diameters smaller than one centimeter using a mechanical method. A planetary ball mill is used to grind the pieces into a powder with diameters of one micrometer or less. The energy required for this process is obtained from solar power or nuclear. The debris powder is then charged by electron beam. This charged condition can be used to accelerate the movement of the powder in a tandem electrostatic particle accelerator. Continuous thrust is generated by ejecting charged powder from the nozzle of the engine because of momentum transfer. This thrust can be used to allow the spacecraft and robotic cleaner to perform orbital maneuvers and to rendezvous with other debris. The ejected charged particles will be blown away from the circumterrestrial orbit by the solar wind and the effect of Earth magnetic field. Thus, digesting the space debris not only removes the orbital debris but also provides the necessary thrust to propel the cleaner. Numerical simulation reveals the specific impulse of debris engine is determined by the accelerating electrostatic potential, charging potential and the charge-to-mass ratio of the powder. In addition, the thrust of the engine is largely dependent on the mass flow rate of the charged powder at the nozzle and nozzle jet velocity of the powder. With the optimal regulation of the specific impulse and thrust, spacecraft can follow an optimal trajectory. In addition, this approach provides a new concept for asteroid exploration and interplanetary flight using a sustainable fuel supplement.

本项目提出空间碎片发动机的新概念和一种空间碎片清理的新方式。立足于尺度小于10cm的空间碎片清理工作。将捕获到的空间碎片通过机械方式分解后，使用球磨等物理方式将碎片粉碎到一定细度，并通过电子束充电方式使粉末带电。带电粉末在串列式静电粉末加速器中加速后高速喷出，为空间碎片清理轨道器变轨飞行提供足够动力。这些带电粉末将在太阳风及地球磁场的作用下飘离地球周围。一方面，清理了地球周围的空间碎片，为人类可持续地利用空间环境提供了保障，另一方面，为航天器获得动力提供了足够的工质，延长了清理器的在轨寿命和飞行距离，提高了单次发射的工作效率。此外，由于航天器不需要携带大量的燃料，可持续的空间燃料供应，也将为小行星探测和行星际航行提供更好的思路。

由于人类日益频繁的空间活动，空间碎片数量日益增多，对在轨航天器安全构成了严重的威胁。如果放任其发展，空间中将有可能发生灾难性的凯斯勒效应，多数在轨航天器将在空间碎片的链式破坏中损毁，给各国经济，军事，民用等各领域造成极大的灾难。目前，各国航天机构都建立起了地基监测网络，对可能的空间碎片碰撞事件进行预警。.本项目所提出的空间碎片发动机，立足于使用捕获到的空间碎片，转化为发动机可用的推进剂。在完成碎片清理目标的同时，获得可持续的动力来源，延长了清理器的工作寿命。本报告是空间碎片发动机的预研报告，主要针对空间碎片制粉的方法进行研究，提出使用球磨仪对金属样本进行研磨。使用转刀式粉碎机对非金属材料进行粉碎。通过实验发现，大部分金属样品在球磨机的研磨作用下，多数粉末粒径达到微米量级，少数大颗粒需经过筛分再研磨来实现粉末大小的均一性。.本项目同时研究了粉末推进的三种方式，即静电推进，带电磁推进和激光推进。详细分析了三种推进方式的优缺点，并进行了比较。激光推进是一种结构简单，设计简便，对于物料品相要求不高的推进方式，符合空间碎片发动机的工作环境要求。因此，我们在项目中通过实验详细研究了粉末激光推进的可行性，初步量化地测量了空间碎片粉末激光推进比冲的大小，并分析了空间碎片粉末种类和粒径大小对比冲的影响。.空间碎片发动机虽然起源于空间碎片清理任务，但是可持续，低标准的推进剂供应，也将为小行星探测，行星际航行等任务提供更好的思路。