Pi Zero W used to launch glider 10km up and land it safely back to earth
Izzy Brand, a student at Brown University, USA, created a clever system to recover the data from his high-altitude balloon (HAB). Rather than use a parachute and geolocator, he instead fitted the data module to a glider set to land at preprogrammed co-ordinates.
Izzy reveals, “I had the idea a long time ago – maybe early high school (2013).” Initially the idea was just to find a way to fly a glider, dropping it from a hot-air balloon, as Izzy’s “nearby hills weren’t steep enough.”
The glider uses a Raspberry Zero W and a Pixhawk, a flight controller powered by an ARM processor. “I chose the Zero W,” Izzy explains, “because it can run MAVProxy, essentially a terminal version of the GUI-based ground station software used to control the Pixhawk.” Izzy chose the Pixhawk due to his familiarity with its predecessor, the ArduPilot.
At 10 000 m, the Zero W turned on the autopilot mode and “triggered a solid-state relay to burn the nickel-chromium wire and release the glider.”
Izzy explains that the Pixhawk module’s autopilot mode operates on a system of waypoints, so he set “only one waypoint co-ordinate at the target landing location, with an elevation of zero.”
In addition, the Pixhawk doesn’t have a glider mode, so Izzy had to “set the maximum ascent angle to zero so the glider wouldn’t try to climb without a motor and thereby stall.”
Amazingly, after launching the balloon and driving to the landing site 122 miles away, the glider was waiting just 10 m from the target location.
“We were astonished,” Izzy tells us. “This project failed miserably in 2015, [as] the glider landed in a forest about ten miles from its target.”
Izzy would like to thank his friends Luke Fisher and Nick Menz for their help “in testing the glider and on the launch day.” You can find the source code and flight logs here.