Design Study of Laser Fusion Rocket

本研究的主要目的是设计一种能够载人火星任务的激光聚变火箭，有效载荷为100吨。结果总结如下：(1)首先对DT靶进行内爆/燃烧模拟，评估靶增益和所需激光驱动能量；阐明了聚变产生的中子和α粒子在点火和燃烧阶段的作用。(2)开发了二维无碰撞粒子池（PC）代码，用于分析DT球团微爆炸产生的等离子体碎片与推力室外加磁场的相互作用。推力转换效率（以动量表示）是由从中心轴到磁线圈的夹角的函数给出的。结果表明，在<平方根> / h时，效率达到-60%。(3)在推力室设计中选择的磁喷嘴中有可能出现瑞利-泰勒等等离子体不稳定性。等离子体在膨胀过程中不应在磁场中扩散。为了研究这一问题，开发了三维PIC代码。对这个问题的调查正在进行中。(4)为了比较，对D-^3He燃料/反场结构（FRC）火箭进行了等离子体设计研究。结果表明，D-^3He/FRC火箭也是载人火星任务中很有前途的推进系统之一。此外，还对核聚变火箭进行了相关研究。这些问题包括使用自旋极化燃料的可能性、火箭系统的结构设计、燃料方案和氚在太空中的处理。

The main purpose of the present study is to design a laser fusion rocket that is capable of manned Mars missions with a payload of 100 tons. The results are summarized as follows.(1)First, implosion/burn simulations were made for DT targets to evaluate the target gain and required laser driver energy. The roles of fusion-produced neutrons and alpha-particles in the ignition and burn phases were clarified. It was found that with the laser driver energy of <greater than or equal>3MJ,we can achieve the target gain as hig(2)A two-dimensional collisionless particle-in-cell (PC) code was developed to analyze the interaction between plasma debris derived from the DT pellet microexplosion and magnetic field applied in the thrust chamber. The thrust conversion efficiency (in terms of momentum) is given as a function of rheta, the angle subtended from the central axis to the magnetic coil. It was shown that the efficiency has a broad maximum at rheta<square root>0ﾟ and reaches -60%.(3)There is a possibility that plasma instabilities such as Rayleigh-Taylor one occur in the magnetic nozzleadopted here in the thrust chamber design. The plasma should not be diffused out across the magnetic field duringits expansion. In order to investigate this problem, a three-dimensional PIC code was developed. The examination of the problem is in progress.(4)For the sake of comparison, plasma design study was carried out for a D-^3He fueled/field-reversed configuration (FRC) rocket. It was shown that the D-^3He/FRC rocekt is also one of the promising propulsion systems for manned Mars missions.In addition, some studies relevant to fusion rocket were also made. These include the possibility of using spin-polarized fuels, structural design of rocket system, fueling scheme, and tritium handling in space.