Non-Intrusive Multidimensional Investigation of Spallation Phenomena in Ablating Materials

本研究是对航天器热防护材料热膨胀现象的多维实验研究。溅射是烧蚀过程的一个重要组成部分，但人们对其了解甚少，它为进入行星大气层的航天器提供热保护，确保飞行和使命的成功。到目前为止，只有非常有限的实验spectrum的数据在文献中，这是可用的数据不是特别详细的，这项工作的目的是，第一次，整理广泛的实验测量targeting spectrum和量化的spectrum对航天器的热负荷的影响。这分为两个部分，第一部分是材料的表面状态和从表面喷出的颗粒，第二部分是这些颗粒对整个流场的影响。将使用双色比高温测量，摄影测量，层析成像和高速成像进行详细的调查表面状态。这将导致对散裂的颗粒数量以及颗粒尺寸、温度和速度的测量。表面状态测量对于理解材料响应至关重要，因为这受到表面温度和从表面物理剥离的材料量的严重影响。这些测量将允许评估溅射过程对整体消融和材料反应的影响。此外，喷射粒子的特性是模拟剥落粒子对流场影响的关键。本研究的第二个组成部分是剥落粒子对整个流场影响的实验测定。粒子被喷射过程喷射出来，并将新的辐射和反应成分引入流场，这些成分在烧蚀建模中历来被忽略。利用光谱学，高速过滤成像和层析成像，这项调查将量化这些注入粒子的流场的影响。这些实验将测量粒子引起的辐射强度变化，包括绝对辐射强度和辐射的空间分布。从这次调查中获得的数据集将是第一次广泛和详细的测量空间现象。这些数据可用于材料响应代码和耦合烧蚀流场计算分析的验证和确认。这可以改善航天器热防护材料的数值模型，确保更高的确定性和效率，在未来的航天器热防热设计。

This study is a multidimensional experimental investigation into the spallation phenomena for spacecraft thermal protection materials. Spallation is an important, yet poorly understood, component of the ablation process which provides thermal protection for a spacecraft entering a planetary atmosphere ensuring flight and mission success. Thus far there is only a very limited amount of experimental spallation data available in the literature, and the data which is available is not particularly detailed.The objective of this work is to, for the first time, collate extensive experimental measurements targetting spallation and to quantify the effects of spallation on spacecraft thermal loading. This is split into two components, firstly the surface state of the material and the spallation particles ejected from the surface will be characterised, and secondly, the effect of these particles on the overall flow field will be evaluated.A detailed investigation of the surface state will be conducted using two-colour ratio pyrometry, photogrammetry, tomography and high-speed imaging. This will result in the measurement of the number of particles spallated and the particle sizes, temperatures and velocities. The surface state measurements are critical for understanding the material response as this is heavily influenced by the surface temperature and the amount of material physically stripped from the surface. These measurements will allow the effect of the spallation process on the overall ablation and material response to be evaluated. Additionally, the ejected particle characteristics are key to the modelling of the effect of the spalled particles on the flow-field.The second component of this investigation is the experimental determination of the effect of the spalled particles on the overall flow-field. The particles are ejected by the spallation process and introduce new radiating and reacting components into the flow-field which have been historically ignored in ablation modelling. Utilising spectroscopy, high-speed filtered imaging and tomography this investigation will quantify the effect of these injected particles on the flow-field. The experiments will measure the radiation intensity modifications caused by the particles, both in terms of absolute radiation intensity and spatial distribution of the radiation.The data sets resulting from this investigation will be the first extensive and detailed measurements of the spallation phenomena. These data can then be used for verification and validation of material response codes and coupled ablation flow-field computational analyses. This can then improve the numerical models of spacecraft thermal protection materials ensuring higher certainty and efficiency in future spacecraft thermal heat shield design.