Mecha Slam Flight Computer

FINAL PROJECT BREAKDOWN: https://www.youtube.com/watch?v=E6nz4wVNLdM

The Final Vehicle was completed, including the intergration of the PCB within the rocket airframe as seen below. It featured a thrust vector control mechanism, but was unfortunately unable to fly due to a pad failure on launch day. I hope to reattempt a flight in the near future.

Pictured Above: Thrust vectoring gimbal.

Thankfully, despite the failure of the launch vehicle, the flight computer was flown on a seperate rocket in a limited capability, primarly for datalogging and testing attitude estimation alogrithms rather than active attitude control. The launch video is linked here:https://www.youtube.com/shorts/99yDGJM8t2c

The flight was successful, with good deployment and safe recovery. However, the rocket flight computer did not contribute to this and was only used in a limited capacity. 

Furthermore, a breakdown video on design choices, areas of improvement and structure of the flight computer can be found here:

The MechaSlam rocket flight computer is an innovative PCB that runs Guidance Navigation and Control (GNC) onboard my latest TVC rocket- ZeroLock. The aim of this rocket is to achieve a soft landing, but not just anywhere. Precision landing on the launch tower is the ultimate goal, inspired by SpaceX's Falcon 9 heavy.

This is an early-stage, custom-designed flight computer developed to build a vertically landing model rocket. This board implements advanced real time non linear model predictive control with real-time sensor data and is designed for thrust vectoring actuation for stable flight. It represents the first phase of a long-term R&D effort toward a full precision-guided reusable rocket, inspired by Falcon 9 but scaled for educational access.

The current stage in development will integrate computer vision, and nonlinear model predictive control (NMPC), all handled onboard, something never seen before at an amateur rocketry scale. The PCB will use a 6-layer SMD layout, offering excellent performance and creating a highly complex PCB that is able to facilitate rocket landing anywhere. 

1. Power Delivery Unit

The PCB includes onboard power regulation using multiple LMR16030 buck converters to step down LiPo battery voltage to regulated 5V, 3.3V, 6V and 1.8V rails. These power critical subsystems like the STM32 microcontroller, Raspberry Pi CM4 and Zero 2, servos, and sensors. Decoupling capacitors and ferrite beads are used for noise suppression. High-current traces are routed and thermal reliefs are included. Test points are provided for live debugging.

2. Main Flight Control Unit (MCU Core)

The core of the board is an STM32H753ZIT6, a 400MHz high-performance ARM Cortex-M7 MCU, used for real-time flight control tasks including Thrust Vector Control (TVC), fin guidance, and sensor fusion. It features:

- Dual SPI buses with dedicated chip-select lines for time-synchronized sensor reads

- SD card logging via SDIO

- Hardware timers for precise PWM signal generation to 6 servos (TVC and airbrake actuators)

- Built-in watchdogs and brownout detection for robustness

3. Inertial and Environmental Sensing Suite

A dual-IMU setup is used for high-reliability inertial measurement:

BNO085 (sensor fusion with 9-axis output)

ICM-42688-P (high-performance raw gyro/accel)

These are complemented by a BMP390L barometric pressure sensor for altitude data. Redundant I²C and SPI buses are used for sensor isolation and fault tolerance.

4. Proximity and Terrain Awareness

The PCB integrates four Acconeer A121 pulse radar sensors over two SPI buses. These enable high-resolution proximity sensing for vertical terrain mapping during landing phases, assisting the vision system and airbrake deployment. The pulse radar modules also allow the rocket to fuse velocity data for extremely accurate height detection and speed detection, critical in landing systems. 

5. Compute Vision Subsystems

Two Raspberry Pi modules are integrated:

CM4 for running a nonlinear model predictive controller (NMPC) in real-time

Zero 2 W for handling stereo vision and ArUco tag detection for precision landing

The PCB features 2 2x20 connectors to effectively mount the nano wave share A carrier boards which then attaches onto the cm4, allowing the main PCB to communicate with the CM4.

6. Wireless Communication

The PCB includes footprints and UART connections for:

LoRa module (900 MHz telemetry to ground station)

An external antenna U.FL Connector is attached to the PCB rather than impendance controlled lines to offer ease of reproduction to other individuals without any loss in performance. 

7. Debugging & Expandability

Multiple test points for SDA, SCL, 5V, GND, and UART lines

JTAG/SWD port for flashing and debugging the STM32

Breakout headers for future additions (GNSS, pyro channels, CAN bus)

2.54mm pin pads for servo connections

8. Mechanical & Thermal Design

6-layer PCB with separate analog and digital ground planes

Four mounting holes for structural integration inside a 74-100mm diameter rocket airframe

Strategic component placement to reduce EMI and thermal coupling

Overall, while this PCB is certainly complex and requires a 6 layer board design for maximum redundancy and minimal risk of failure in flight, it can be reproduced quite easily be others looking to take the next step in the amateur rocketry journey.