Self-Healing Polymers for Space: a Study on Autonomous Repair Performance and Response to Space Radiation

One of the main challenges of space exploration is to design novel light, initially packed structures that both make the best use of the reduced transport capacity of the available launchers and ensure safety and reliability levels comparable to those of classical solutions. For this reason, space inflatable structures have recently gained interest: initially folded in stowed configuration to fit in the launcher's space dedicated to the payload, they can be then inflated and deployed to reach the required volume. In addition, these structures are much lighter than traditional ones and would significantly reduce the related mission costs. However, these solutions are currently unable to withstand damage after, for example, impacts with micrometeoroids and orbital debris (MMOD), and they would depressurise and collapse if punctured, with catastrophic consequences for devices and astronauts in case of crewed missions. In this context, the possibility of integrating self-healing materials into inflatable and deployable space structures has drawn the attention of the scientific community, as it would lead to autonomous damage restoration and subsequently increased spacecraft safety, operational life, and autonomy. Nevertheless, the effects of space environment on these materials are still to be determined and could lead to a significant decrease of their overall performance. The here presented study analyses the healing performance of a set of candidate self-healing polymers for space applications (either studied as matrices into nanocomposites or inserted into multilayers) as well as its variation after irradiation under simulated space radiation. The self-healing response is assessed through in-situ flow rate measurements after puncture damage. Maximum and minimum flow rate, the time between them and the air volume lost within the 3 minutes following puncture are collected as healing performance parameters. The same tests are then repeated on gamma-ray irradiated samples to study the variation in self-repairing performance after exposure to simulated space radiation. Results show that the healing performance is higher in systems with lower viscous response, and that this performance decreases in the irradiated samples. A further analysis of the effects of space environment on the presented materials is hence required. The NASA HZETRN2015 (High Z and Energy TRaNsport, 2015 version) software is also used to simulate galactic cosmic rays. The materials are compared to identify the most promising candidates, and possible solutions to increase their shielding performance are considered.