A trick used by missionaries to drop and retrieve supplies to remote native villages in Ecuador more than 50 years ago is now the centrepiece of an innovative idea by Aurora Flight Sciences.
As suggested by the title of a 2011 patent application (#20120048996 published on 1 March), "System and method for the retrieval of a smaller unmanned aerial vehicle by a larger unmanned aerial vehicle", Aurora has proposed a method for a larger UAV to capture and potentially deploy a smaller, slower UAV in flight, allowing a holistic mix of the two in remote areas. Big UAVs are good for long-term stationkeeping and persistent surveillance while small, or micro, UAVs (MAVs) are best for short-term up-close-and-personal contacts.
"A system or method that synergistically combines the advantages of both MAVs and larger UAVs will yield a truly revolutionary capability," says Aurora, adding that a larger UAV that would deploy and capture MAVs would "create the capability of rapidly deploying MAVs at much farther distances than ever before".
But how to dock and undock the two given a large difference in flying speeds of the two?
That's where Aurora took the cue from the missionaries. In Operation Auca in Ecaudor (an endeavour that did not go all that well, as you'll note from the Wiki site), a pilot would fly a Piper PA-14 in a tight spiral over the drop point while an assistant would lower a basket to the ground below. The rope and bucket follow a helical shape, and when the bank angle is right and the rope long enough, the bucket, in theory, lands at a stationary position on the ground, allowing the transfer of goods.
A cartoon in the Aurora patent shows the principle in action:
What Aurora noted was that different locations along the helical have lower speeds than the main aircraft, which in this case is the larger UAV, which could allow the lower-speed MAV to link up with the rope at essentially zero forward speed, completing the capture or deploy.