Experiment design of a payload for a sub-orbital rocket to study spacecraft repair after space debris impacts

This paper proposes the investigation of the cold-welding phenomenon for use in spacecraft hull repair following a hypervelocity impact by space debris. An experimental test rig, custom repair patch design and the actuation methods described can be tested and qualified, at TRL 4, onboard a sub-orbital sounding rocket flight. It has been shown that similar metallic materials can fuse or weld at ambient temperatures provided that there are sufficiently high contact forces. In the Space environment, this fusion is aided by the fact that the joint surfaces do not re-oxide after wear and, as a consequence, atomic diffusion of the metal occurs at lower contact forces. It has also been demonstrated that, even under terrestrial conditions, the action of a low fretting load can nearly double this adhesion force. Cold-welding in the Space environment was first analysed in the 1960s as an adverse reaction from wear and it was attributed to be the cause of failure of certain mechanisms. This research, however, will investigate the potential of cold-welding for use in spacecraft hull perforation repair. Spacecraft shield and hull perforation may occur after a hypervelocity impact due to Micrometeoroids and Orbital Debris (MMOD). In-situ repair from inside the vehicle is preferable due to the pressure differences. Evaluating a paradigm shift in cold-welding adhesion, this project aims at developing a test apparatus to apply custom repair patches (Indium, SS17-7PH and AL AA2024) and will investigate its adhesion properties during re-entry for a range of mechanical application conditions. For evaluation purposes, four different types of chambers can be tested and monitored using pressure sensors. The recovery of the payload will allow further metallurgical analysis of the cold-welded joint. After the terrestrial development and validation using a vacuum chamber (first phase), the core activity is the design and testing of the experimental setup and its integration as a sounding rocket payload. The test rig will be able to simulate the hull breach in terms of crack and opening and will be capable of applying the repair patch and monitoring its performance during re-entry after the sub-orbital flight (second phase). The Aerospace, Mechanical and Electronic Department at South East Technological University (SETU), Ireland, and the Department of Aviation at the Malta College of Arts, Science & Technology (MCAST), Malta, are collaborating with the Centre of Studies and Activities for Space (CISAS) “G. Colombo” of the University of Padova, Italy for the second phase of this research project.