I am part of a JPL team studying the upper atmosphere. Our plan is to take our test apparatus up in a helium balloon to 15 km and then, after it does its thing, we want to drop it in some kind of a UAV and have it return to us. The vehicle has to be able to carry a payload of 7 kg. What might be a good strategy for this? What types of UAV's would be best? If we use a fixed wing plane, will it be able to pull out of the free fall? Basically, we are seeking the advice of those more knowledgeable than us. If you could design this system as best as possible without any concern about cost, what might you do?