Solarufo

The principle is simple: you take a thin-thin black bag, close it on one side, wait until air penetrates and fills the bag and bind it now. In the sun the air heats up and rises upwards. A dragon that works without wind. Great! But here was the problem: we never had winds. But only with absolute wind silence you should let the Ufo rise, otherwise it tears. Other probators said it would be so fast, so far I can neither confirm nor deny it.