Real Time Operating Systems in Active Controlled Rockets

Modern rocketry requires sophisticated abstractions to handle complex controls and monitoring in real-time environments. Although a simple loop suffices for non-critical applications, thrust vector control (TVC) systems require simultaneous management of TVC, data acquisition, and telemetry. In a single loop, these would be handled sequentially, with the system crashing if one process fails. To mitigate this risk, a real-time operating system (RTOS) provides multithreading, scheduling, and deterministic timing. This paper presents the development and integration of an RTOS on an L2 TVC rocket and details the overall system architecture, kernel, I/O, and its application on an avionics system. The operating system features five layers: a HAL for peripherals, a hardware layer managing hardware, a kernel layer providing scheduling and memory management, a Middleware layer for file systems, and an application layer for tasking. The kernel includes a preemptive scheduler that manages context switching, state estimation, and memory. I/O is handled through a device driver framework that supports interrupts and DMA-based transfers. In its integration on an L2 rocket, the avionics system maintained consistent 3 millisecond latency on telemetry, accurate state estimation during flight, and sub-microsecond latency in context-switching. Flight testing validated the architecture’s reliability with telemetry having 0.02% packet loss and data-logging on a flash chip. A key innovation in this application is the implementation of a Linear Quadratic Regulator (LQR) within a timer interrupt, providing deterministic controls. Through the bare-metal operating system, this system provides a foundation for multithreaded rocket software that can be applied in larger scale TVC systems.