Sisyphus — Subsystem
Two-axis gimbal mount driven by dual servo actuators provides real-time attitude correction during powered ascent. The mount is built for fast iteration and tightening control authority as flight loads change.
Iteration
First iteration integrated an overly complex rocket motor reloading mechanism, which used a bolt-action locking mechanism and a spring system that pushed the ascent motor forward into the TVC mount. While the system successfully demonstrated thrust vectoring, the design's complexity made it too unreliable for flight.
Iteration
The Mark 2 iteration simplified the motor reloading mechanism, removing the bolt-action lock and spring system in favor of a more straightforward friction-fit motor staging. This change improved reliability and greatly reduced the chances of mechanical failure during flight. Despite the greater vectoring inertia, it still demonstrated effective thrust vectoring performance.
Characterization
A static fire run to measure the gimbal under real thrust rather than on the bench: how far it can move, how quickly it moves, and how long it takes to start moving. Those measurements went into the simulation, and they also explained why the previous flight failed.
Conversion and scaling errors left the TVC producing about 60% of its intended control authority. With the landing legs removed, the lighter rocket flew faster, and near the end of the burn the aerodynamic moment outgrew the restoring moment the gimbal could make. It tumbled.
It wasn't a single catastrophic fault, but a compounding of multiple weaknesses that only became detrimental in the regime where they overlapped.