This study outlines the design and optimization processes for the development of a multipurpose urban firefighting and disaster relief unmanned aerial vehicle (UAV). The design strives to attack and suppress fires that occur in high rise structures at heights greater than can be reached by ladder truck. The design also strives to deliver a payload of disaster relief supplies to affected areas, reducing risk to ground transport efforts.
The study outlines the design and optimization of design components utilizing SolidWorks and testing of these components using SolidWorks Simulation and Flow Simulation packages. This study details the development of the final propeller and frame design, and the range of tests performed within SolidWorks to ensure the design can perform to the required standards.
Given the dimensional advantages and torque cancellation capabilities a coaxial octocopter frame is developed. In designing and testing a propeller the proposed design is capable of producing a maximum thrust of 118 lbf. with a minimum factor of safety of 2.238. The propeller spacings are optimized to produce maximum thrust in both the coaxial and in-plane directions which are 23.6 inches and 25.6 inches respectively. For urban firefighting the selected hose and nozzle combination are capable of supplying 60 GPM of water at a height of 150 ft. from the ground. At this loading the minimum factors of safety of the frame and propeller are determined to be 2.238 and 3.034 respectively. The corresponding fatigue lives under prescribed number of cycles are determined to be infinite for both frame and propeller. Using rotorcraft theory, the theoretical hover time that the UAV can maintain in firefighting is determined to be 1.7 hours. Using a combination of SolidWorks Flow Simulation and aerodynamics theory the maximum velocity of the UAV at a pitch of 30 degrees from vertical, hauling a box with dimensions capable of carrying 200 lbs. of relief goods, is determined to be 85 mph. At disaster relief payload capacity the designed frame and propeller are capable of maintaining factors of safety of 3.226 and 3.034 respectively. These factors of safety correlate to fatigue lives of the frame and propeller of 15.98 years and 19.12 years respectively, under prescribed loading. The theoretical flight time the UAV can maintain for disaster relief is determined to be 1.618 hours.
This study provides optimized propeller and frame designs along with selections of engines and other important components for building a multipurpose UAV.