I'm going to present my idea about this Balloon Drone, which should work in real life. Unfortunately, due to the lack of material, I couldn't make it in real life so I thought you people can make this if I give you my idea. I will be demonstrating with pictures, drawings and animation which are not good but still I'll try my best that you understand the concept of this drone. That is why I recommend "Go through the full instructions first before you start making, to get the idea of this drone." It is really simple.It works with motor attached to a propeller, which is then attached to a Clock's minute hand and it's uplifted by the Hydrogen/Helium balloon. The concept is that a minute hand move's a complete circle and reaches its final position above the hour hand. Now if you attach a motor with a propeller to it, it should move forward and take a full circle around your locality and return to it's final position because it's being pushed forward and upward at the same time (The radius of the circle depends on the speed of your motor). But when it will return, it will be in a higher position due to the uplift of the Balloon. So we will make a timed parachute drop-off system with it.Since Drones are supposed to be autonomous spying or guarding units, this was a simple Idea I could think off. Now, the real disadvantage of this Drone is that, If it's pushed by wind, then it's returning position might get displaced, for which, I recommend a tracking system, so that you can track it and retrieve it. Now, on to the build-up.
IMPORTANT MESSAGE BEFORE YOU START : This is a conceptual Idea so it can differ heavily from the real life thing as there's a heaven and hell difference between Theoretical and Practical things. That's why I suggest this for those who have experience in making RC/Miniature Aero Vehicles. You can make improvements by yourself to make it working. Also don't forget to post your improved idea or the real working vehicle in the comments so that I and others can see it.