About time I update this
The HAB Glider project aims to return Radisondes from 100,000 feet by an autonomous glider.
Our glider, Clementine, was finally launched under a balloon and released at low altitude.
Here’s the video:
This video saw the progress from the upgrades of the last glider to the test of a low altitude release.
Total list of changes:
- Changed the aircraft to run missions by airspeed & the TECS controller
- Added redundancy to release mechanism
- Long range video, telemetry and radio control
- On/off ground killswitch & procedure for the release mechanism to avoid unwanted activations
- Different gauge & length of nichrome wire to burn release mechanism at lower temperature
- Aircraft uses RTL instead of mission waypoints
We now have 3 methods of release, they all heat up a nichrome wire and melt a fishing line tying all of the release strings together. My project log 9 goes over the first version & testing of this in more detail.
- Autonomous release by RPi
monitors altitude through dronekit. Once at altitude, sets the flight mode to RTL, activates a relay & cuts the release string. This also covers a failure mode where if the balloon were to burst before the release altitude, it would notice this, set the flight mode to RTL and cut the release string still.
- Release by switch on remote through RPi
Runs in the same loop as the above dronekit program. This doesnt offer any realistic redundancy and is mainly just used for debugging and pilot flexibility.
- Redundant release through second set of nichrome wires and relays
This release mechanism is supposed to cover if the raspberry pi were to stop working. It’s activated by a relay connected directly to the Cubepilot orange, and is activated with the remote. The set of nichrome wire on this is much shorter and a different gauge on this one, meaning that it burns hotter. This can cut through the fishing line AND the release strings as well, and if left on for a couple more seconds will burn through itself and open the circuit.
I also changed the aircraft to glide with the TECS controller prioritizing airspeed. This is a bandaid on the original issue of gliding into the wind while trying to cover ground.
The next engineering milestone is to fly to the top of class E airspace. A lot of legal milestones to hit as well.
This plane in its current state can probably pass that, but I want to see if i can:
- Change the TECS controller to work on groundspeed, or a hybrid of airspeed and groundspeed.
The idea is to prioritize movement relative to the ground (returning to home while flying into the wind) vs just trying to have a consistent airflow of X m/s over the wings.
- redesign the airframe
this airframe was selected and used simply for controls validation. thick wings are comfy in the air but arent the best at gliding
- research more into what the optimal way of trying to glide to cover distance is
talking out of my ass here but i thought it’d be fun to see if the brachistrone curve could be adapted to gliders at all:
probably not since this curve is optimized for speed vs total distance, and drag increases with square of velocity. fun thought though.