A tool developed by two members of the NESC team assessing improved International Space Station (ISS) micrometeoroid and orbital debris (MMOD) damage shielding designs will provide more accurate prediction of damage produced by MMOD impacts. Older equations used for MMOD damage prediction are based on limited data and are applicable only to a narrow range of shield materials and configurations. A new damage prediction tool was developed that more accurately predicts the hole size and crack length caused by a hypervelocity impact (HVI) on a pressurized spacecraft cabin or module. This tool, called the W-S hole/crack prediction model, was designed to be used within the application that calculates the risk of an MMOD-caused catastrophic failure. Like earlier models, the W-S model will provide results based on a given particle size, impact obliquity, and velocity. However, the new model also uses parameters associated with the shield configuration as independent variables. Typical MMOD shielding includes an outer shield called a bumper, an inner shield called the rear wall, and a space between the two called the standoff. There may also be intermediate shields or thermal insulation blankets between the bumper and the rear wall. The shield parameters that are included in the W-S model are those related to the material and geometry of the rear wall and bumper, the standoff distance from the bumper to the rear wall, and the mass and placement of any intermediate bumpers. The result is a generic damage predictor that can be universally applied to different shield configurations.
W-S model damage predictions compared to the results using older models show that while the newer predictions tend to predict larger hole sizes than previous models, HVI test data correlate more closely to the W-S predictions. The W-S equation is now being used for the ISS in calculating the risk of catastrophic MMOD damage to ISS modules, but in the future can be applied to other spacecraft with different MMOD shield configurations.
For more information, contact Dr. Joel Williamsen (jwilliam@ida.org) or Dr. William Schonberg (wschon@mst.edu)