August 14, 2013
Credit: Photo: Amy Butler
A debate over stealth is defining the future of the U.S. Navy’s Unmanned Carrier-Launched Airborne Surveillance and Strike (Uclass) program, as well as drawing battle lines among the four likely contenders, according to industry sources speaking at the Association for Unmanned Vehicle Systems International conference and show in Washington this week.
Because stealth is at the center of the argument, secrecy limits what participants can say, at least in public. Moreover, there is a larger question involved: should Uclass be designed to survive against high-end threats, or should penetrating intelligence, surveillance and reconnaissance against the toughest defenses be the job of the classified unmanned air system being developed by Northrop Grumman for the Air Force?
In one respect, the Uclass contenders — Northrop Grumman, Lockheed Martin, Boeing and General Atomics-Aeronautical Systems Inc. — are converging: they appear to be looking at roughly the same size and weight. All will probably be working at the upper wingspan limit (about 65 ft.) imposed by carrier operations. (The high-wing E-2 Hawkeye is a special case.) Carrier approach handling requirements set upper and lower bounds to wing loading. Videos and models at the AUVSI show suggest that the Navy is looking for the ability to carry two weapons in the size class of a 1,000-lb. Joint Direct Attack Munition or a 500-lb. laser-guided bomb. Overall, Uclass appears to be lighter than the 45,000-lb.-class X-47B but much heavier than either the GA-ASI Reaper or the Lockheed Martin RQ-170 Sentinel.
However, the contenders differ on stealth. Over the years, engineers and planners have concurred that tailless blended-wing-body designs offer better radar cross-section reduction than tailed designs, particularly over a large bandwidth and all aspect angles. But incorporating weapon bays, propulsion systems and electronic and optical apertures (Uclass requires an estimated 30 separate apertures, one industry source says) into a relatively small flying wing is not easy. It can cause weight and cost penalties that offset the theoretical aerodynamic advantages of a flying wing.
Lockheed Martin’s notional Uclass design is a flying wing that resembles an enlarged RQ-170, with a sensor fairing below the centerline, and weapon bays inboard of the landing gear. Artists’ concepts show a grilled inlet similar to the type used on the RQ-170 and F-117.
Northrop Grumman engineers confirm that the company’s Uclass will resemble the X-47B, with a version of the demonstrator’s cranked-kite configuration. GA-ASI is understood to be looking at a vehicle with a similar layout to its Predator C/Avenger demonstrator, but considerably heavier and more powerful. Boeing is saying much less about its design, but artwork on display at AUVSI (and used in company-to-government presentations) points to an Avenger-like tail-and-wing design.
But as another industry source points out, stealth itself is not immune to countermeasures over the planned lifetime of the Uclass system. In that case, it might be more valuable to provide the space, weight and power needed for electronic attack systems than to push for the last degree of stealth.
Industry people at AUVSI suggested that a Navy move toward greater stealth could favor Northrop Grumman, because of its X-47B experience and because the Navy aircraft could share technology with its land-based black-world sibling. On the other hand, it would be a high-end solution that might price Northrop Grumman out of the competition if stealth requirements were not increased. Boeing, meanwhile, is unique in that it’s not flying a direct precursor to its offering, since its Uclass seems only distantly related to its Phantom Ray stealth UAV design.