Autonomous return from a High Altitude Balloon
Our project is about returning a glider autonomously from a weather or high altitude balloon from 100,000 feet. Project logs aim to produce a clear, concise and focused weekly update to this project.
Next weeks project log will have me rebuilding the airframe since this one is worn out. During that time I'll explain design choices and will also have time for a Q&A so drop any questions you have about the project!
Project Log 2
The video
Project Log 2:
This week goal was to get the airframe ready for testing with a motor. Rather than launching from a balloon at 400, or 1000 feet, it's financially smarter to just bring it up there with a motor and cut the throttle to test autonomy/glide performance. After gluing on a motor, I ran into multiple problems.
Problem 1: Lack of control
I already ran to this problem when conducting glide tests. I increased the surface area of the gliders elevons and the problem was definitely fixed, but seeing this problem arise again after that meant that the glider was definitely capable of rolling and pitching properly. To start off, an easy way to tackle this problem is the center of gravity. The optimal CoG point definitely changes based on what you want the aircraft to do, and the aircrafts design itself, so it's a good idea to experimentally figure it out. I had a battery weighing 50 grams less with me so I swapped the batteries out and slid it to the most aft position i could. That solved the maneuverability problem.
Problem 2: Loss of control at certain times in flight
This was different than the first problem in the sense that the aircraft wouldnt struggle to pitch up or down, but would completely refuse to do so. After a flight i brought the aircraft down to test the servos and all were working fine. I flew it once more and closely observed the elevons when the aircraft lost control. The elevons wouldnt respond to the commands from the controller. I flew the aircraft one more time and kept the airspeed down, which allowed me to have full control over the aircraft. So, the problem was that either the servo, or the servo connections couldnt handle too much air pressure on the elevons. To spot if the problem was with the servos or with the linkages, I lightly put my finger over the servo arm and tested it. It wouldnt budge - a problem I never had with my nylon gear 9g servos. I took the aricraft home and swapped the servos out with my other turnigy metal gear servos. That did the trick and the aircraft definitely flew fine after that.
Problem 3: Wings flapping
The structural aircraft is definitely ruined since I cut multiple rectangles into the center of the body to reach the electronics and batteries, but the aircraft still had a wing spar that worked well with aircrafts with the same wingspan and thicker wing chords. This didnt pose a huge issue during flight but is certainly undesired. This issue feels less of a problem with the wing spar but more of the rigidity of the actual design. The body/"fuselage" of the aircraft is too far forward, and to repair it I'll first change the chevron wing extenders sweep from 45 degrees to 35 degrees. This would decrease lateral span, thus decreasing the torsional force from the rear of the aircraft to the front. The flap feels less of a lengthwise issue but more of a lateral issue. Still isnt fixed, the second revision will test if this worked.
Project Log 3
Again, the third project log will be of me rebuilding the aircraft and prepping it with the pixhawk. During this time i'll be explaining design choices on the aircraft, and hopefully running a Q&A about the project and the team, so if you have any questions, or statements, please drop them :).
Thanks for all of the support!
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