Following the proof-of-concept demonstrator X-47A "Pegasus", the X-47B was born as a full-sized technology demonstrating Unmanned Combat Aerial Vehicle (UCAV) intended for carrier operations within the ranks of the United States Navy (USN). The X-47B holds roots in the DARPA-led J-UCAS (Joint-Unmanned Combat Air System) program which was developed to find a single drone solution for both US Army/Navy requirements. While the J-UCAS program ultimately fell to the budget axe in February of 2006, the US Navy persisted with a UCAV program all their own through the "X-47" initiative. Boeing and Northrop Grumman were charged with its development and, the USN eventually siding with Northrop Grumman, the X-47A was born as a smaller version (19 foot wingspan) of the full-sized X-47B to follow.
The X-47 program began in 2000 to which the Northrop prototype evolved to a completed form in mid-December of 2008 at the Air Force facility in Palmdale, California. Work continued on the complex software required of the vehicle and, in late December 2009, the aircraft underwent active towed taxiing tests at Palmdale. In early 2010, the X-47B prototype was able to accept instructions to taxi under its own power. The major challenge faced by Northrop Grumman engineers remained how to overcome the corrosive effects of the salty sea on the aircraft's exposed surfaces - a challenge faced with any waterborne design including surface ships.
As a technology demonstrator, the X-47B became a critical piece in the USN's at-sea UCAV requirement. The type currently serves to evaluate various important components tied to an ultimate end-project goal which would see production-quality aircraft closely follow the form and function of the X-47B. As such, the X-47B was deliberately evolved along the lines of a full-sized, full-weight airframe with production-quality systems included for the purpose of streamlining overall development and, if and when approved, ease serial production.
Design of the X-47B includes a very defined triangular shape which appears to be growing in popularity with drone engineers the world over. There are no obvious vertical surfaces about the aircraft making it a "true" flying wing design in the mold of the Northrop Grumman B-2 "Spirit" stealth bomber. The powerplant is buried within the fuselage and aspirated via a shallow duct along the forward fuselage spine. The engine exhausts through a specially designed port at the rear of the airframe. Lacking a pilot, more internal volume can be reserved for specialized mission equipment, armament, fuel stores, avionics and subsystems. The undercarriage is retractable and made up of two single-wheeled main legs joined by a twin-wheeled nose leg. As a carrier-based aircraft, several key qualities have been integrated into the X-47B design including folding wings for storage, corrosion resistance (to counter the effects of the salty sea) and a reinforced undercarriage with arrestor hook. Stealth is incorporated into both the aircraft's design and its operating systems. Production-quality forms will eventually be fielded with two internal weapons bays (as in the Lockheed F-22 "Raptor" and Lockheed F-35 "Lightning II") for up to 4,500lbs of ordnance (most likely guided munitions).
Power for the X-47B is being served through a single Pratt & Whitney F100-220U turbofan engine. This provides a cruising speed of 685 miles per hour with an operational range in excess of 2,100 nautical miles. The aircraft is cleared to operate at service ceilings nearing 40,000 feet. Overall dimensions include a wingspan of 62 feet with a running length of 38 feet and ground height of 10.4 feet. The folding wings allow the span to contract to 30.9 feet when folded.
On February 4, 2011, the X-47B was towed from its hanger at Edwards AFB in California and, when unhooked, taxied under its own power and into position before taking off down the runway and into the sky - it's first recorded flight. It received the designation of Air Vehicle 1 (AV-1). A month later, engineers held enough confidence that the aircraft was flown with its undercarriage fully retracted. Northrop Grumman's test crew continued to define the remote control techniques needed for routine aircraft function - flight operations over sea are some of the most extreme conditions concerning flight in an unstable environment, engineers challenged with preserving both crew and aircraft safety while attaining optimal operational efficiency. Carrier deck operations offer their own distinct brand of complexity and one of the most dangerous work environments in the world - aircraft taxiing on deck aircraft and simultaneous launching of others all the while sharing space with dangerous fuel lines and munitions. The Northrop Grumman contract required that the drone could operate every task as if a piloted aircraft - fly with safety and perform reliably. The research and development curve experienced by its engineers resembled the pioneering problems of the United States Navy decades earlier in learning complexities of launching and the recovering biplane aircraft on its first carrier - the USS Langley (CV-1) in 1922.
In January of 2012, Northrop Grumman tested equipment designed to allow ground crews to manually steer the X-47B along the carrier deck. The tailless X-47B was given a wingspan of 62 feet - making it nearly twice as wide as it is long - and 17 feet wider than the Navy's Boeing F/A-18 "Super Hornet" strike fighter. The X-47B features a maximum speed in the "high subsonic" range with an unrefueled range of six hours - over 2,100 nautical miles (3,900 km). In May of 2012, AV-1 began high intensity electromagnetic interference testing at Patuxent River to test its compatibility with electronic warfare (EW) systems (the USN aircraft carrier is perhaps the highest electromagnetic space on any surface ship when its numerous radars and warfare systems are in play).
The X-47B was lifted dock side by crane aboard the USS Harry S. Truman (CVN-75) at the Naval Station Norfolk, Virginia to begin its carrier-based assessment in December of 2012. The aircraft required compatibility testing with communication systems, movement from hangar bay to the flight deck and all related aircraft-type duties while on a carrier. The tests indicated that the X-47B was well-matched for carrier functions - as good as any manned aircraft currently in use. As of this writing (May 2013) the X-47B continues its sea trials, launching and recovering aboard the USS George H.W. Bush. Northrop Grumman and the USN will be working on inflight refueling to help increase the over-target flight time. Over the last decade, the USN has spent upwards of $1.8 billion on the two X-47B prototypes though the day will surely come when these drones will replace the piloted aircraft as we know it - for some observers a blessing to accept and, for others, a philosophical question of whether it should be allowed to happen at all.
The X-47B has met some recent notable program goals: on May 14th, 2013, the system became the first drone aircraft to be successfully catapulted from the deck of an aircraft carrier (USS George H.W. Bush (CVN-77) on the Atlantic Ocean). Soon after launch the X-47B UAV was transferred over to a second pilot who electrically flew her across the Chesapeake Bay to the drones base at the Naval Air Station Patuxent River, Maryland and landed her on a simulated carrier deck. Weeks earlier on May 4th, completed a simulated carrier landing (with arrestor hook) on the Patuxent River. On May 17, 2013 the X-47B took off from its Patuxent River base and made a number of approaches to the USS George H.W. Bush, successfully completing a number of "touch-and-go" landings and takeoffs (that is, not formally landed by arrestor cable or launched by catapult). The touch-and-go process is standard US Navy airmen training on all carriers.
Both of the X-47B prototypes will be retired by the end of 2013 having completed their testing. One example will find a permanent home at the Pensacola Naval Museum (Florida) and the other at Naval Air Station Patuxent River (Maryland).
April 2015 - It was announced that an X-47B completed aviation history's first autonomous in-flight refueling action involving an unmanned air vehicle - opening the door to very-long-range missions not limited by pilot fatigue levels.