Autonomous Hexacopter for Generating Brief Microgravity Windows

• Thomas Bubanj, Mechanical Engineering, University of Delaware

• Thomas Bubanj, Mechanical Engineering, University of Delaware

Microgravity has enabled research into aerospace medicine, materials science, and off-world hardware. However, avenues for producing microgravity conditions—orbital spaceflight, drop towers, parabolic flights—are prohibitively expensive and logistically difficult for undergraduate research teams. We present an autonomous multirotor programmed to fly a vertical free-fall trajectory producing seconds of microgravity for an onboard payload. By reducing thrust to follow a ballistic trajectory, a multirotor and its payload experience near-zero contact forces, and an onboard accelerometer measures near-zero apparent acceleration. This state of apparent weightlessness is commonly known as microgravity.

For hardware, the platform was constructed as a custom hexacopter built around a Pixhawk flight controller running ArduCopter, along with a Raspberry Pi companion computer. The Pi runs Python code implementing flight logic to command an accelerating downward velocity in GUIDED mode, tracing a free-fall trajectory before initiating powered recovery, while simultaneously logging data from an onboard accelerometer. Sensor measurement and logging pipelines were characterized and validated during controlled bench “drop” tests. Tests successfully logged a window of free-fall measuring 0.045 g, proving the concept before airborne experimentation. Telemetry and flight autonomy were brought up and validated on the built aircraft in autonomous flight.

This work yields both a flight-tested microgravity platform with a fully characterized accelerometer response, as well as open-source, reusable code for its flight control autonomy and data logging pipeline. With accessible consumer drone hardware producing seconds of predictable microgravity, we hope this experiment facilitates research that can be replicated by other teams who would not otherwise have access to microgravity environments.