Dynamic Materials Testing for Ultrahigh-Speed Spaceflight

最近的技术发展标志着一个非常高速航天飞行的新时代正在出现，有可能实现快速的行星际运输和最终星际飞行的路线图。以这种速度进行的航天飞行开辟了新的动力学领域，因为航天器会遇到微流星体撞击和高发射加速度。例如，帕克太阳探测器将遇到速度为300公里/秒的尘埃颗粒撞击，比实验室测试微米级撞击所能模拟的速度快30倍以上。在这些条件下发生的撞击将进入以前未探索的高能量密度区域;未来几年将看到更大的航天器速度。目前，最有前途的快速太空旅行技术似乎是定向能量，其中地面激光相控阵作为一个单一的，衍射限制的光学能够施加能量到数百万公里的距离的目标。这项技术已经通过光子学革命实现，光子学革命已经看到基于光纤的激光放大器的成本的摩尔定律式降低，这允许以模块化方式开发射束器。这些能量可用于为航天器上的大推力电力推进提供动力，或者可以将光子压力直接施加到薄膜上。前一个概念是NASA资助的快速深空运输革命性推进研究所的主题，而后一种方法是突破性Starshot的基础。在直接驱动方法中，动态光子加载到薄（亚微米）膜上可以导致100，000 g的加速度。目前还没有测试方法来测试薄膜对动态载荷的响应。这项研究计划将率先开发测试能力，以完整地模拟这种高速状态下的动态，包括尘埃颗粒的冲击问题和薄膜对高动态载荷的响应。气体动力学技术能够将瞬态负载施加到薄膜上，这些薄膜与驱动激光器的条件定量匹配，但不必使用10 MW级激光器阵列。具体地说，激波管导致施加到帆上的动态载荷与直接激光驱动光帆遇到的载荷基本相同。使用在我的实验室开创的技术，包括光子多普勒测速，将使薄膜材料的动态响应下的代表性负载进行实验研究。使用高能材料内爆薄壁真空圆柱体有可能驱动壁材料射流以大于100 km/s的速度前进。该方案将利用现代诊断工具和计算机模拟系统地研究这一现象，目的是能够利用这些喷流在实验室中以感兴趣的速度再现撞击事件。

Recent technological developments have signaled that a new era of very high velocity spaceflight is emerging, with the potential to enable rapid interplanetary transport and a roadmap to eventual interstellar flight. Spaceflight at these speeds opens up new regimes of dynamics as the spacecraft encounters micrometeoroid impacts and high launch accelerations. For example, the Parker Solar Probe will encounter dust grain impacts at speeds of 300 km/s, more than 30 times faster than laboratory testing of micron-sized impacts is capable of simulating. The impacts occurring under these conditions will enter previously unexplored regimes of high energy density; the coming years will see even greater spacecraft velocities. At present, the most promising technology for rapid space travel appears to be directed energy, wherein a ground-based phased-array of lasers act as a single, diffraction-limited optic capable of applying energy to a target out to distances of millions of kilometers. This technology has been enabled by the photonics revolution that has seen a Moore's Law-like decrease in the cost of fiber-optic-based laser amplifiers, which permits the beamer to be developed in a modular fashion. The energy can be used to power high-thrust electric propulsion on-board the spacecraft or can apply direct photon pressure onto a thin film. The former concept is the subject of a proposed NASA-funded institute for Revolutionary Propulsion for Rapid Deep Space Transit, while the latter approach is the basis of Breakthrough Starshot. In the direct drive approach, dynamic photon loading onto thin (sub-um) films can result in accelerations of 100,000 g. At present no testing methodologies exist to test the response of the thin films to dynamic loading that would be used. This research program will pioneer the development of testing capabilities for the complete simulation of dynamics in this ultrahigh velocity regime, including the dust grain impact problem and the response of thin films to high dynamic loading. Gasdynamic techniques enable transient loads to be applied to thin films that are quantitatively matched to the conditions of the driving laser, but without having to use a 10 MW-class laser array. Specifically, a shock tube results in dynamic loads being applied to the sail that are essentially identical to those encountered with a direct laser-driven lightsail. Using techniques pioneered in my lab, including Photonic Doppler Velocimetry, would enable the dynamic response of thin film materials under representative loading to be investigated experimentally. The use of energetic materials to implode a thin-walled evacuated cylinder has the potential to drive a jet of wall material forward at velocities greater than 100 km/s. This program will systematically study this phenomenon using modern diagnostic tools and computer simulation, with the goal of being able to use these jets to reproduce impact events at velocities of interest in the laboratory.