The question hanging over this build is a classic one: can a first rocket get away with no GPS at all? The maker wants to skip it for two stated reasons, and both sound sensible to me. A GPS unit would add weight to an already compact airframe, and tracking from the ground would mean extra designing, buying and setup work. The recovery plan instead leans on a buzzer that fires when the rocket touches down to help with finding it.
The rocket itself, drawn up as R77M_final in OpenRocket, runs on an F-35-8 motor and carries an electronics bay with a parachute for recovery. The flight computer is an Arduino Pro Micro paired with a BMP280 barometric sensor, an MPU6050, and a micro SD card module handling the data logging, all fed by a 3.7V 1000mAh LiPo through a DC-DC voltage regulator. Sizing looks tidy to me: 631mm long, about 34mm across, 248g loaded with motors, with the center of gravity at 402mm sitting ahead of the center of pressure at 455mm.
The simulation predicts an apogee near 863 meters, a peak velocity of 205 m/s, and a descent lasting roughly 170 seconds at about 5 m/s, for a total flight near 180 seconds. Logging g-force and altitude at 20 to 50 Hz on an Arduino seems like a genuinely interesting target for a first avionics stack. Choosing the Pro Micro over an ESP32 for being cheaper, simpler and lighter reads to me as a sensible call.
One constraint stands out: the motor already carries a -8 delay, so there is no room to push main parachute deployment any later. And whether the buzzer alone is enough to find a rocket after a 170-second drift down remains the open question at the heart of this project.