Next phase in UAV development: Autonomous Aerial Refueling - X-47B

SvenSvensonov · Dec 10, 2014

If the Navy can get the resources, it plans to test an aerial refueling capability on its experimental carrier-launched unmanned aerial vehicle, the X-47B, as early as next year, Naval Air Systems Command officials told USNI News on Tuesday.

The move follows a $64 million June 2014 contract award to Northrop Grumman that extended the testing schedule of the Navy’s two X-47Bs on carriers and continue autonomous aerial refueling (AAR) research as part of the Navy’s Unmanned Combat Air System demonstration (UCAS-D) program.

“Those efforts include additional [carrier] detachments and AAR software coding through the remainder of this calendar year,” said NAVAIR program manager Capt. Beau Duarte in a statement provided to USNI News on Tuesday.
“If resources allow, the Navy may demonstrate autonomous engagement flight testing in fiscal year 2015.”

In 2013, USNI News reported NAVAIR had tentatively scheduled an autonomous aerial refueling (AAR) in 2015.

NAVAIR has conducted AAR tests with a surrogate aircraft to test the X-47B software that allows the test plane to mimic the interaction between the tanker and the aircraft receiving the fuel but stops short of a mid-air refueling.

One of the two X-47Bs — called Salty Dog 501 and Salty Dog 502 — is equipped with an aerial refueling capability, USNI News understands.

AAR has become an issue in the ongoing debate over the Navy’s plan for a production carrier-based UAV, the Unmanned Carrier Launched Surveillance and Strike (UCLASS).

Outlines for a less expensive and more surveillance oriented UCLASS eschew the need for AAR and create an aircraft with a longer inherent endurance and a lower cost per airframe.

Advocates for a more heavily armed and stealthy UCLASS say that AAR is essential for extending the range of the aircraft for deep penetrating strikes.

“The current trajectory for the Navy program was 14-plus hours of unrefueled endurance, which then forces you to compromise on payload as well as on signature reduction,” Robert Martinage, former Department of the Navy under secretary and currently with the Center for Strategic and Budgetary assessments told National Defense Magazine on Monday.

“If the aircraft is capable of air-to-air refueling, the argument in favor of really long unrefueled organic range — 14 hours plus — is weakened.”

From Navy Could Test Aerial Refueling on X-47B in 2015 - USNI News

The concept of using a UAV as a tanker has also been tested!

The phrase "fill 'er up" is being redefined for the age of robotic aircraft.

Northrop Grumman said yesterday that in a flight test earlier this year, it took a big step closer to an eventual autonomous aerial refueling between unmanned aerial vehicles as part of the $33 million DARPA KQ-X program.

In the "risk reduction flight test," which took place January 21, a Global Hawk UAV from NASA played the role of the aerial tanker , and Northrop Grumman's Proteus test aircraft--a manned UAV surrogate, we should point out--was the one in search of the refueling boom. Among the matters being evaluated were wake turbulence between the two aircraft, which at their closest were just 45 feet apart, along with engine performance and flight control responsiveness in the stratosphere.

The interaction took place at 45,000 feet in what Northrop Grumman called a "landmark flight." The Global Hawk has a ceiling of about 65,000 feet and can reach speeds approaching 340 knots.

What didn't take place was any actual refueling. This was strictly a dry run.

"Demonstrating close formation flight of two high-altitude aircraft, whether manned or unmanned, is a notable accomplishment," said Geoffrey Sommer, KQ-X program manager in Northrop Grumman Aerospace Systems, in a statement.

The January flight was a prelude to an actual autonomous aerial refueling involving two Global Hawks, a DARPA KQ-X event that's scheduled for spring 2012. Successful refueling would allow for flights lasting up to one week. According to Northrop Grumman, the 44-foot-long, 13-ton NASA Global Hawk has a maximum endurance of 31 hours.

The broader context here is that the defense sector has its sights fixed on high-altitude, long-endurance (HALE) operations for unmanned aerial vehicles, often using more exotic energy sources, for missions such as surveillance and communications. Boeing, for instance, is working on a UAV called the Phantom Eye that is intended to use hydrogen fuel to eventually fly at 65,000 feet for up to four days. In January, Aerovironment's Global Observer made the first-ever hydrogen-powered UAV flight--just a few hours at low altitude, but the aim is to get it to fly for up to a week at a time at 55,000 to 65,000 feet.

Solar power also gets a nod in UAVs from the likes of Qinetiq, whose Zephyr last July stayed aloft for 14 days nonstop, and Boeing, whose SolarEagle has a short-term goal of flying continuously for 30 days and an extremely ambitious goal of flying without a break for five years.

Tests conducted by NASA