This morning we launched Soli Deo Gloria 7, a towed solar Montgolfiere, from my suburban backyard. This flight ended suddenly over Lake St. Clair, with the last data being transmitted at an altitude of approximately 22,000 feet. The flight was intended to last all day - the latex balloon should have reached a peak altitude of about 90,000 feet before burst and then the solar Montgolfiere should have ram-inflated during descent, eventually reaching a stable float at around 70,000 feet.
Unfortunately, I made a last minute change to the payload - replacing a 1.5 pound battery pack with one that weighed only a few ounces - and this made the solar Montgolfiere unstable. More specifically, the payload actually weighed less than the remains of the latex balloon after burst (which happened prematurely), so the solar Montgolfiere inverted and spiralled into the lake instead of inflating.
The launch was still fun, though - my son, Ryan, helped with all stages of the inflation and launch and took the video below.