Streamlining Verification & Validation of GNC Subsystems using NeXosim: an Open-Source, Rust-Based Discrete Event Simulator.

Over the past decades, the complexity of both commercial and scientific space missions has steadily increased. As new classes of space missions are undertaken, and their technical and programmatic objectives become increasingly ambitious, more advanced spacecraft architectures are developed to support them. In-Orbit Servicing (IOS) missions constitute a particularly relevant example of space endeavors that stimulate the development of novel spacecraft subsystem technologies. Those technologies include highly sophisticated Guidance, Navigation & Control (GNC) systems with growing levels of autonomy. Unfortunately, considering that on a typical spacecraft project, a substantial amount of time can be attributed to Verification & Validation (V&V) activities, advanced GNC systems are at elevated risk of not being thoroughly verified. As a result, increasingly complex GNC systems can suffer from verification gaps – differences between ground-based system behaviour observed during V&V activities, and the actual in-flight behaviour. The following paper describes how NeXosim – an open-source, Rust-based Discrete Event Simulation (DES) framework – can help address this issue in the context of preflight validation of future GNC systems. To illustrate this process, a demonstration case study featuring a Hardware-in-the-Loop (HIL) demonstration stand is introduced. This is followed by the discussion of how enabling Digital Twinning of GNC hardware by NeXosim can facilitate launching hardware-centric V&V activities, even before physical components are available for testing. Finally, to outline how NeXosim is utilized in the context of the upcoming IOS missions, its role in the development of the Infinite Orbits’ Endurance and Orbit Guard 3 vehicles is briefly summarized.