Determination of critical parameters for solar probe plus shielding .

摘要

A methodology to determine critical design parameters such as critical "design" particle size, and critical "design" impact speed for the shielding of the Solar Probe Plus spacecraft was developed in this thesis. Several critical components and surfaces of the spacecraft such as the Solar Array North, the Thermal Protection System, and the ISIS Instruments were analyzed in this study. The methodology determines the critical "design" particle size based on the required reliability or probability of no impact. Current NASA methods do not provide means to calculate critical "design" impact speeds for missions such as Solar Probe Plus, where the distributions of impact speeds can vary significantly from particle size to particle size and with position of the spacecraft as a function of time due to the non-circular orbital trajectory that the spacecraft will follow. Previous methodologies attempted to determine the critical "design" impact speed based on the distribution of speeds from the smallest particle size, and yielded conservative results. This thesis uses the entire distributions of impact speeds for all dust particle sizes in an attempt to reduce conservatism and thus launching and material costs for the mission. This is crucial because it accounts for the dependency of the impact speed distribution on particle size, and is achieved by normalizing the total cumulative number of impacts as a function of the normal component of impact speed for every particle size. Results from this thesis show that the critical impact speed is significantly reduced when compared to previous methodologies. As the required probability of no impact increases, the critical particle size also increases, and the critical impact decreases.