What if balloon flies towards “restricted airspace” (problem: airports) or drifts towards ocean (problem: can’t be recovered) ? If this happens, can payload to detach itself from the balloon and descent to the ground, rather than keep flying in unwanted direction?
Simple: burn the rope and let balloon go.
Nichrome wire is a special wire that can quickly heat up to extreme temperatures. In only a few seconds, its temperature can reach ~1,500 degrees, enough to burn through the rope that holds the payload.
This is how nichrome wire looks (I will use the thinnest one – bottom left):
Here is a test, where I wrapped 2-inch nichrome wire around a rope and connected it to a battery. Watch what happens: