Assessment of damage to thermal protection systems due to micrometeoroid and orbital debris impacts

Thermal protection systems for hypersonic vehicles are low- to zero-fault-tolerant. In order to understand the fault tolerance of this system, the number of impacts that cause mission failure due to micro-meteoroid and orbital debris damage is presented. This number differs based on the mission, so a methodology is presented to solve for this number. The methodology is comprised of two branches, the first branch solves for the critical depth and the second branch solves the debris environment. These two branches are then combined to generate the number of impacts. The critical depth is the minimum depth at which impact damage will cause mission failure. A method of calculating the critical depth is presented over mission and vehicle parameters of interest. The debris environment is the mean flux of particles that will impact the vehicle during its anticipated orbital lifetime, and the resulting penetration depths from these impacts. Combing these two values gives the number of impacts that cause mission failure and the maximum allowable size and speed of impacting particles before mission failure. Results indicate that the critical depth is a strong function of the entry environment as well as mission and vehicle parameters, including orbital lifetime, vehicle surface area, and thermal protection system margin