FINsight: Strain-Sensing Fins for Aerodynamic Data Collection

Why it mattered

Problem

Traditional rocket flight data often relies on simulations, onboard cameras, or indirect measurements. Those tools are useful, but they do not directly capture how each fin behaves under real aerodynamic loading. FINsight was created to close that gap by measuring strain at the fin level during flight.

As part of Duke AERO's Pitchfork rocket project, I led development of a system that integrates strain gauges into the fins themselves. The goal was to produce high-resolution data that could reveal how aerodynamic loads, vibration, and temperature changes affect fin behavior during launch.

Electronics and sensing

System Architecture

FINsight uses custom-designed printed circuit boards where copper-trace strain gauges are placed according to modal analysis of the first three fin vibration modes. The strain gauges are arranged as part of a Wheatstone bridge circuit, allowing small fin deformations to be converted into measurable voltage changes.

Those voltage fluctuations are captured by NAU7802 24-bit analog-to-digital converters and processed by a Teensy 4.1 microcontroller. The full electronics stack is housed in a 3D-printed Strain Measurement Module inside the rocket body, which keeps sensitive components away from the high-temperature region near the motor casing.

• Copper-trace gauges were integrated into custom fin PCBs rather than added as external sensors.
• Dual lithium-ion batteries were used to support reliable operation through launch.
• Thermal measurement was included so temperature effects could be separated from structural strain.

Composite fin design

Mechanical Integration

The fins use a sandwich composite structure: a G-10 fiberglass core, the PCB on one side, and carbon fiber reinforcement on the other. This maintained strength while giving FINsight access to the fin strain field. To keep the fin structurally balanced and reduce electrical interference, the PCB was coated with UV-cured solder mask.

Because the PCBs were only 0.4 mm thick, the sensing layer could be added without heavily disturbing the fin's aerodynamic or structural profile. Wiring passed through small slits that were sealed with a carbon-epoxy mix to preserve airframe integrity.

Validation loop

Testing and Results

The system was tested through wind tunnel runs and thermal calibration. In wind tunnel testing, the rocket was exposed to airspeeds up to 35 m/s at high angles of attack to simulate demanding aerodynamic conditions. The strain gauge readings showed a clear relationship between voltage and airspeed, validating that the system was capturing fin loading.

Thermal calibration helped identify how temperature fluctuations could bias the measurements. With the thermocouple integrated into the fin system, FINsight could separate thermal effects from aerodynamic strain more effectively.

What the data enables

Impact

The value of FINsight is not only the measurement system itself, but the design feedback it creates. The data can inform future fin geometry, mounting procedures, mass distribution, and vibration mitigation strategies. It also creates a path toward actively controlled fins that respond to flutter or aerodynamic loading in real time.

As the system matures, future work includes improving calibration, reducing thermal noise, and refining the electronics for better sensitivity and robustness. The long-term goal is to make FINsight a standard part of Duke AERO's design and validation process for future rockets.