A Hard Real-Time Flight Control System for an Unstable Rocket. I coded the guidance, navigation, and control (GNC) software for a physically unstable rocket (like a vector-thrust model or a full-scale aerospace vehicle) that must run on a bare-metal microcontroller with no operating system. If my code takes even 1 millisecond too long to calculate a matrix multiplication because of a cache miss or a bad loop, the timing loop slips, the engine over-corrects, and the rocket physically explodes in mid-air. My debugger is an actual explosion.