According to Aviation Week, U.S. engineers will soon demonstrate the first in-flight docking of two unmanned aerial vehicles (UAVs) while continuing the development of an autonomous aerial refueling system. Two specially designed UAVs, a tanker and a receiver, will perform their first test flights next month. 'One of the six-foot wingspan UAVs is equipped with an extendable refueling boom with drogue, or basket, and the other with a retractable probe.' These tests will check the autonomous rendezvous and docking processes, but will not involve actual fuel transfer, according to one of the companies involved. But read more...
This concept of autonomous air refueling of unmanned air vehicles has been developed at Texas A&M in partnership with StarVision Technologies and Cobham's subsidiary Sargent Fletcher. You can see above a photo of the two UAVs on the ground. The tanker is on the left and the receiver on the right. (Credit: Texas A&M, link to the original version)
You can see above a simulation of the two UAVs approach in the sky. Here, they have already established contact and are now checking the docking status before starting to refuel. (Credit: StarVision Technologies, Inc.) This image has been extracted from a short video (1 minute, 7.97 MB) available from StarVision.
Here is how Aviation Week describes the future autonomous aerial refueling system. "The sequence will begin with the tanker and receiver UAV in parallel orbits. On command from the ground, the receiver will move into the same orbit and chase down the tanker using its transmitted Global Positioning System position for guidance. Once it has closed to within 30 feet of the tanker using GPS, a sensor on the receiver’s nose will pick up a ring of infrared beacons on the refueling drogue and generate commands for the autopilot to guide the probe into contact with the basket."
In "Robots to engage in mid-air couplings," The Register provides additional details -- with its very personal tone. "The two six-foot airdroids concerned will apparently use the more common probe-and-drogue refueling system favoured by the US Navy and most NATO nations, rather than the boom method employed by the US Air Force. Under probe-and-drogue, the tanker flies steadily along, trailing a basket-like socket on the end of a fuel line. The aircraft wishing to take fuel then flies its probe into the basket. This procedure is traditionally said by human pilots as being rather like 'taking a running fuck at a rolling doughnut.' Cobham subsidiary Sargent Fletcher says that its 'powered weapon' retractable probe-o-bots are quite capable of this. They will steer themselves in on final approach by tracking a glowing infrared ring on the offered receptacle."
Here is the conclusion of The Register article. "Successful testing will open up prospects for autonomous skydroids to carry out very long duration missions, sustained by similarly unmanned, unpiloted refuelling tankers. Endurance will be limited only by maintenance requirements -- or by eventual mechanical failures if these were ignored due to operational imperatives."
Sources: Graham Warwick, Aviation Week, September 18, 2008; Lewis Page, The Register, September 18, 2008; and various websites
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