Effect of Space Environment on Structural Diagnostics

Abstract

Space structures such as rockets, spaceships, and satellites are subject to environmental factors depending on their mission. As mankind becomes more dependent on various space assets, understanding the behavior of structural components in space grows in importance. For commercial space transportation, three environments are of the most interest: suborbital, orbital and interplanetary. Currently, commercialization priorities are focused on suborbital and orbital applications. This contribution explores potential effects of suborbital and orbital environments on structural diagnostics of spaceships. The primary concern for suborbital flight is survivability of structure during launch and re-entry. This is when most of the dynamic loads occur which may cause mechanical failure of the spacecraft. In addition, the suborbital flight is characterized by high thermal loads occurring during re-entry. Given that during suborbital flight, spaceship spends only minutes in space, the contribution of actual space environment to such flight is minor with rather low radiation doses and stable temperature range. The environmental contribution changes when a structure is placed on low earth orbit (LEO). The temperature could vary between -120 oC to +120 oC in this orbit and this thermal variation could cause thermal fatigue on structures leading to formation of cracks. Absence of atmosphere (pressure in the order of a few micropascals) affects a vibration environment. Atomic oxygen (AO) considerably affects non-metallic materials, causing their deterioration on LEO. Materials on LEO are subject to UV, particulate and ionizing radiation with each of them being responsible for different deterioration mechanisms. Micrometeorites with speeds exceeding several km/s could cause notable damage. In this contribution, we study effect of space environment on piezoelectric-based SHM. Thermal effects are considered first, which are followed by the radiation environment. Results of laboratory experiments are presented along with the theoretical developments. Recommendations are suggested for utilization of SHM on LEO.