You should know the principle of hot air balloon! There is no flame, only hot air can be used. The simplest hot air is water (hot) steam. Find a tripod and several iron frames, put a hot water kettle under the tripod, heat it with quick heat, build a hot air balloon with the iron frame (don't hang a heavy basket under the hot air balloon, and the hot air balloon is preferably made of plastic film, and the material should be light enough), boil water, collect steam, plug the stove mouth tightly, and let the hot air balloon cling to the lid.