The Design and Construction of a Rotary Drone Battery Hot-Swapping System to Increase Flight Time

Overview

Drone swarms enable multiple drones to coordinate and cooperate, increasing system robustness and scalability compared with single drones. These systems show strong potential across applications, including military and search-and-rescue operations (Phadke, 2023). However, current batteries support only around 20 minutes of flight time, significantly limiting mission endurance (Chunwu Xiao, 2023). Current approaches to extending flight time provide limited improvements. For example, a rocket-staging-inspired technique yields only a 16.7% endurance improvement with three batteries (Hyojun Kim, 2025). Inspired by mid-air aircraft refueling, this project constructed a mechanism intended for installation on a larger “mother drone” capable of swapping batteries for swarm drones during flight. The device consists of a rotating battery bank and a piston-driven transfer mechanism that rapidly exchanges batteries. Compared with existing ground-based swapping stations, the design is simpler and more modular while maintaining horizontal weight distribution and a low center of gravity, supporting future aerial implementation. Current ground-based battery swapping stations require 40–60 seconds on average, with the fastest device claiming 30 seconds per swap (Spielman, n.d.), from the start of operation to being ready to take off. This project established a benchmark of achieving 70% of attempted swaps successfully and in under 20 seconds. Testing shows that while operating in the optimal speed mode, the prototype achieves 6.05 ± 0.58 (2σ) seconds per swap, with a 100% success rate across 24 attempted swaps, exceeding our benchmark. Future improvements may include enhanced docking geometry, increased battery capacity, and structural optimization for aerial deployment.

Competition history

• CSEF 2026 Applied Mechanics (Senior Division) · Entry S-02-11

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