Rain impact retrospective and vision for the future

Abstract Rain impact effects on aerospace vehicle components have presented challenging problems for investigation in experimental physics, analytical and computational mechanics, fracture mechanics, and systems analysis. The term “rain impact” is used in preference to the more common term “rain erosion”, since the resulting damage is not always an erosion process. The significant advances made by the author over the past 25 years in understanding the damaging aspects of liquid drop impingement are described. The perspective is subjective based on the author's view of what was required and what was done to satisfy the need. This background is used to introduce the work that still needs to be done, in the author's view, to provide meaningful estimates of the response of materials during flights through hydrometeor environments. The purpose of this discourse is to appreciate the lessons learned and to stimulate interest in making further progress in a fascinating area of research. How realistic is our understanding of the sequence of events that takes place in the flight environment? How well can the physical concepts of raindrop impacts be represented in a computational form for predicting rain impact damage? What experimentation (simulation or material property evaluation) is required to establish a component's rain impact damage response? Do the existing testing capabilities provide data that is relevant to the flight environment? These are the issues considered based on the author's past experience.