The Variable Drag System (VDS) is an air-braking system designed to deliver a high-powered rocket to precisely one mile AGL. It actuates three aluminum drag blades into the airstream, actively changing the vehicle drag profile on ascent.
The system responds to sensor data in real time to maintain the proper balance of kinetic and potential energy through flight. In NASA Student Launch competition flight, the VDS delivered the vehicle to 5,303 ft, only 23 ft from target.
Design Overview
With blade faces perpendicular to airflow, VDS increases projected area by a factor of 1.28 and drag coefficient by an estimated factor of 1.35.
Simulation
To predict mission performance, I developed a Simulink simulation with customizable weather, 6DOF equations of motion, and launch animation support.
Key Components
A single DC motor drives all three drag blades, with precise position feedback from a rotary encoder. A Teensy 3.6 microcontroller controls actuation and reads a 9DOF sensor plus barometric pressure sensor to estimate flight state and command corrective braking.
Embedded Software
The embedded stack is written in C and C++, organized across five classes, and ran at around 90 Hz. It integrates pressure, accelerometer, gyroscope, and magnetometer data through a Kalman filter to estimate state and actuate blades.
Mission Success
The VDS was demonstrated to deliver one mile AGL within +/- 33 ft. System documentation, simulation rigor, and performance all contributed to the team receiving NASA Student Launch Vehicle Design Award.