DARPA Performs World's First Hands-Off Autonomous Air Refueling Engagement
NASA pilot Dick Ewers and Flight Test Engineer Marty Trout fly hands-off
during the first-ever fully autonomous air refueling demonstration.
The Defense Advanced Research Projects Agency (DARPA), in a joint effort
with NASA Dryden Flight Research Center, performed the first-ever autonomous
probe-and-drogue airborne refueling operation August 30, at Edwards Air
Force Base, Calif. The demonstration was conducted with a NASA F/A-18
configured to operate as an unmanned test bed.
The Autonomous Airborne Refueling Demonstration (AARD) system used GPS-based
relative navigation, coupled with an optical tracker, to provide the precise
positioning required to put a refueling probe into the center of a 32-inch
basket dangling in the air stream behind an airborne tanker. The tanker was
equipped with a small relative navigation pallet, but production refueling
equipment was not modified in any way. Pilots were on board the F/A-18 for
Autonomous in-flight refueling is a critical enabler for affordable,
persistent, unmanned strike systems. "This flight is a significant
milestone - it demonstrates that autonomous systems can employ the benefits
of air-refueling that have proven so valuable to military aviation," said
Lt. Col. Jim McCormick, DARPA program manager.
"We chose to demonstrate the probe and drogue refueling method because it is
the most challenging for autonomous systems. The precise station-keeping
capability we've demonstrated applies equally to the boom and receptacle
method used by most Air Force aircraft," noted McCormick. The same
technology also promises to enhance reliability, safety and the range of
operating conditions for air refueling manned aircraft.
The flight was the seventh of eight planned for the 15-month AARD proof of
concept program. For this particular test, the pilot provided approval to
proceed at several stages of the maneuver, but was otherwise hands-off.
Operationally, unmanned systems are expected to locate the tanker, form up,
accept clearances, refuel, and disengage without any human intervention.
System performance fully met expectations for the flight. "The end-game
movement of the autonomous system had none of the last-second, high-gain
stabs at the basket that we often see with human pilots. This computer
approach was unbelievably stable and smooth, with deliberate movements
throughout. And when it missed, it was just as smooth when backing up to a
restart point," said NASA test pilot Dick Ewers.
The AARD system was operating in benign flight conditions when it
successfully engaged the basket in two out of six attempts. As important as
the successful engagements, the system safely recovered from each missed
attempt. Miss tolerances were tight for this first attempt. During one of
the missed attempts, the pilot observed the probe was actually inside the
basket when the system pulled back. More robust tracking algorithms and
relaxed miss tolerances are planned to be demonstrated on a final flight
later this month.
DARPA initiated AARD under the former Joint Unmanned Combat Air Systems
program. The AARD system was developed by Sierra Nevada Corp., with team
member OCTEC Ltd. providing the optical tracking system. Omega Air Refueling
Services operated the modified 707-300 tanker used for the tests.
Successful demonstration of the AARD capability will allow unmanned air
system developers and planners to leverage, with confidence, the operational
advantages of in-flight refueling.
Source / Credit: DARPA (Defense Advanced Research Projects Agency)