Issue 32

I. Telichev, Frattura ed Integrità Strutturale, 32 (2015) 24-34; DOI: 10.3221/IGF-ESIS.32.03 24 Development of an engineering methodology for non-linear fracture analysis of impact-damaged pressurized spacecraft structures Igor Telichev University of Manitoba, Department of Mechanical Engineering, 75A Chancellors Circle, E2-327 EITC, Winnipeg, Manitoba R3T 5V6, Canada. igor.telichev@umanitoba.ca A BSTRACT . Motivated by the dramatic worsening and uncertainty of orbital debris situation, the present paper is focused on the structural integrity of the spacecraft pressurized modules/pressure vessels. The objective is to develop an engineering methodology for non-linear fracture analysis of pressure wall damaged by orbital debris impact. This methodology is viewed as a key element in the survivability-driven spacecraft design procedure providing that under no circumstances will the “unzipping” occur. The analysis employs the method of singular integral equation to study the burst conditions of habitable modules, although smaller vessels containing gases at higher pressures can also be analyzed. K EYWORDS . Orbital debris; Impact damage; Pressurized structure; Singular integral equation method. I NTRODUCTION he hazard from orbital debris is a growing international concern for the safety of space-based infrastructure. The series of incidents happened in last six years demonstrated that only one or two collisions can drastically change the orbital debris population. With space activity continuously running and expanding, the rate of collisions in space also increases, leading in turn to a new reality for the orbital debris environment where all functioning spacecraft are under higher risk than they were designed for. Because of the very high impact velocities and possibility to fail catastrophically when impacted, the pressurized modules and pressure vessels play a crucial role in spacecraft survivability. They are identified as the most critical components on-board spacecraft [1-3]. Historically, considerable amounts of resources have been used to developing anti-orbital-debris shielding for such structures to avoid the pressure wall damage. However, the shielding cannot protect the spacecraft from all types of debris. Nowadays, the pressurized modules and high pressure tanks of the most heavily shielded spacecrafts are able to withstand the impact of debris up to one centimeter in diameter. The orbital debris between 1 and 10 cm in size which is too small to be tracked but large enough to cause the shielded pressure wall perforation, poses the highest risk for the spacecraft mission. As it was demonstrated experimentally, the case of both shield and pressurized wall perforation presents a potential for the pressure wall failure in an abrupt fashion [1-4]. The answer to the question whether the spacecraft pressurized structure would undergo “unzipping” due to the impact of undetectable debris is crucial for the mission success or failure. Essentially, it quantifies the spacecraft survivability. Fig. 1 illustrates the survivability-driven design logic where it is assumed that impact of undetectable debris between 1 and 10 cm in size has occurred and the pressure wall is damaged. This design concept requires that when developing spacecraft, all attempts be made to prevent the accidental spacecraft breakups. The mitigation and protection measures are assessed for effectiveness through the fracture analysis (Fig. 1, T