The Idea
After making Sprite 1 at my works hackathon I decided to continue the project and make a new version on my own. There were two major lessons learned from Sprite 1 that I wanted to address in the next design iteration. The first was that the stepper motors used were just too slow. The second was the difficulty of finding a suitable location in the Los Angeles area for dropping and flying an experimental robotic paraglider. My solution was to replace the stepper motors with servos and to add an electrically ducted fan, enabling it to fly up to altitude instead of requiring a drop.
Since this version was going to be self-funded, I faced more constraints in terms of budget and resources. Although I would have preferred to design and machine a structure, I opted for 3D printing for this iteration, as it was more feasible to execute in my apartment.
Trying New Things
One lesson I learned from designing CubeSats at work was the importance of considering the assembly process during design. Previously, for 3D-printed parts requiring threads, I had always used heat-set or threaded inserts. While effective, these required clearance on one side of the hole for a soldering iron or tool. However, as evident in the picture, this design did not allow for easy access. Consequently, I started incorporating captured nuts into my designs. Having used them in this project, I don't think I'll ever revert to inserts for 3D printing; captured nuts offer greater design flexibility, strength, and ease of assembly.
System Breakdown
Flight & Lessons Learned
The first flight was highly successful. The electrically ducted fan provided ample thrust to inflate the paraglider and generate lift. The brake lines offered some control over steering. However, the initial testing highlighted several areas for improvement:
Line Trimming:
It became clear that a jig is needed for line trimming. Currently, I trim the lines by hanging the paraglider and adjusting them until they appear even. During the flights, one side consistently had more control, likely due to uneven trimming.
Angle of Attack:
With traditional paragliders, pulling the brake lines deforms the trailing edge, affecting steering and speed. In my design, pulling both brakes in one direction significantly increased lift, while the opposite direction caused an instant stall. This effect might be due to the altered angle of attack, combined with the EDF's thrust, causing the vehicle to climb. In future designs, I might revert to using spools or create a loop near the control lines to align the brake lines with the center of gravity through the center axis. Another option is to rig the lines for a better angle of attack in their neutral position.
Mass & Aerodynamics:
The vehicle demonstrated its climbing ability during testing, prompting thoughts of how performance could potentially improve with mass optimization and reduced drag. In future iterations, I will consider this more in the design and manufacturing process.
