There are major technical challenges, but transformational technology backed by substantial US funding is bringing the day of the unmanned fighter aircraft ever closer

The recent destruction of a car carrying al-Qaeda operatives on a remote desert road in Yemen by a missile-armed Predator, operating hundreds of kilometres from friendly territory, has given the world a sneak preview of the potential of armed UAVs. With a new generation of purpose-built UCAVs now on the drawing board, there is the promise of an even bigger leap in capability - indeed, some military observers are predicting the demise of the manned fighter.

With testing of the first UCAV demonstrator very much in the early stages, however, the world is still a long way from realising the full potential of robotic weapons. The US military, emboldened by talk of transformational technology, is pouring increasingly larger amounts of money into a series of demonstration efforts once regarded as little more than science projects conducted in obscure laboratories. The US Department of Defense (DoD), in return, is demanding better oversight and co-ordination to ensure these endeavours remain grounded in operational reality.

The Office of the Secretary of Defense is pushing for the establishment of a joint programme office to take charge, and ultimately fuse, the different UCAV demonstration and development efforts. There are three separate technology demonstrations being pursued by the US Army, US Air Force and US Navy, and although the US Defense Advanced Research Projects Agency (DARPA) is participating in each, they are in different phases of development, and very much tailored to meet the individual needs of each service.

The Boeing/DARPA/USAF X-45 UCAV programme is the longest running of three demonstrations, having been launched in 1998, and is the closest to reaching fruition with its goal of fielding a UCAV operational system (UOS) in 2008. There are two X-45A Spiral 0 demonstrators already flying, and Boeing was recently awarded a $460 million follow-on contract to further mature the system and produce two larger X-45B Spiral 1 vehicles. They will closely resemble the planned A-45 Spiral 2 UOS, and act as transition from demonstration to acquisition.

"We want to complete the effort by 2005 and deliver by 2008," says Col Earl Wyatt, DARPA UCAV programme manager. "To do that, we want to minimise the amount of redesign between the X-45B and A-45. I would say that by that time we'll have a limited operational capability, but typically the warfighter designates what is meant by initial operational capability. We are going to give them something that has operational utility, but something they can also be learning with."

Trailing X-45

Trailing the X-45 programme by almost three years is the DARPA/US Office of Naval Research (ONR) UCAV-N science and technology programme. Around $30 million has been spent to date on a Phase 1 study and the Phase 2A preliminary design of two competing systems by Boeing and Northrop Grumman. It had originally been planned to downselect one for a follow-on $100 million flight demonstration in 2005-06. The USN wants to begin full-scale development of an operational system around 2007, with the goal of delivering the system to the fleet by 2015.

Phase 2B has been stalled for almost a year, however, over navy concerns that choosing between the Boeing X-46 and Northrop Grumman X-47B demonstrator at this stage could compromise the industry's ability to bid competitively for the follow-on system demonstration and development (SDD) contract. "What we do in the navy could have some impact on the competitive environment [US] DoD-wide. There is fear of an inadvertent downselect to single contractor," says Cdr Ralph Alderson, USN UCAV-N requirements officer.

The US Army and DARPA in contrast have mapped out a seamless path for the UCAR, which, if successful, in the demonstration phase, would become an acquisition programme around 2009. Four teams comprising Boeing, Bell/Lockheed Martin, Northrop Grumman and Sikorsky/Raytheon are competing for two places in the next preliminary design round due to begin this May. A final downselection will be made next year to produce two flying demonstrators by 2006.

To further reduce risk, there will follow a third operationally more mature "B" vehicle around 2008 before the UCAR programme moves from DARPA to US Army leadership to begin SDD. "What the army has asked DARPA to do with the programme is unique in that we'll continue to work with them to mature the system capability to a point where it will make it into the acquisition environment without further maturation by the service," says Don Woodbury, DARPA UCAR programme manager.

The objectives of the three demonstration programmes vary according to the requirements of the different services. The USAF views A-45 UCAV as a "first-day-of-war" system augmenting manned fighters and bombers. Its initial Spiral 2 capability will be to use both kinetic weapons and electronic attack for suppression of enemy air defences (SEAD). It is envisioned that latter versions, which have been loosely designated Block N, will play a more robust role in the USAF's Global Strike Task Force, employing a broader range of conventional and even energy weapons.


DARPA and the USAF have laid out a schedule of progressively more complex demonstrations and exercises during Spiral 1 to prove the UCAV concept. A second flying demonstrator joined the programme in November, opening the door to multi-vehicle, single-controller operations, including co-ordinated taxiing and flight, inter-vehicle communications, dropping inert weapons and performing missions against simulated threats. The degree of single- and multi-vehicle autonomy will be steadily increased with the introduction of onboard decision-aiding systems.

The X-45A's final Block 4 software load will serve as the building block for the Spiral 1 vehicles due to fly 2005. The two X-45Bs will be larger and more capable than the initial vehicles, with an empty weight of 6,360kg (14,000lb) compared to the X-45A's 3,640kg, and equipped with the more powerful General Electric F404-102D turbofan in place of the current Honeywell F124-100. The X-45B will be built to a stealth design to demonstrate production affordability, and include the integration of low observable avionic and sensor apertures.

While there will be provision for SAR, the X-45B demonstration will focus on integrating data from remote offboard sensors. "There will be provision for things that are not actually in the demonstration, such as fuel in the wing, but which will not actually be carried until the A-45," says Wyatt. "We're also designing for air-to-air refuelling, but until its demonstrated in a parallel [US] Air Force Research Laboratory effort, it will not actually be on board the aircraft."

The USAF is planning to evolve an iterative operation requirements document in parallel with the programme, rather than issuing a definitive set of specifications at the outset. The initial weapon of choice for the UCAV is the 110kg Small Diameter Bomb, up to 12 of which will fit inside the A-45's two internal weapon bays. In time, this will expand to include the larger 225kg and 450kg members of the GPS-guided JDAM family, as well as air- launched decoys, external and internal auxiliary fuel tanks and electronic warfare packages.

The navy's initial interest in UCAV-N will be in the surveillance and reconnaissance role, expanding around 2020 to take in strike and SEAD missions. The USN's unique operating environment presents designers with challenges quite distinct from that of the USAF's land-based UCAV.

Developing a system for autonomous launch and recovery from the pitching deck of an aircraft carrier is made even more difficult by the need to design UCAV-N around a tailless configuration for LO, something that has never been achieved before even by a manned naval aircraft.

This will be the principal objective of the UCAV-N flight demonstration, which the USN is now hoping to achieve using the X-46 and X-47B, providing it can secure the extra funds to test both machines in Phase 2B. "We really need to demonstrate this vehicle can go on and come off a carrier. That's the long pole in the tent as to whether we can do this kind of multi-mission and have a very capable and survivable UCAV. No one has ever done it before with this shape - manned or unmanned," says Alderson.

Simulated-deck landing

DARPA/ONR planning calls for this to be conducted ashore using a simulated aircraft carrier deck complete with arrestor wires and catapults at either NAS Patuxent River, Maryland, or Lakehurst, New Jersey. For precision glidescope control, the navy plans to use the ship-relative GPS variant of the Raytheon JPALS already tested using a Boeing F/A-18. Money permitting, the USN would like to undertake a sea trial, which would also enable it to test for electromagnetic shipboard compatibility and interference.

The USN views UCAV-N primarily as an asset providing the carrier air group (CAG) with a persistent reconnaissance capability over enemy territory during off-cycle periods. This requires the vehicle to be designed for extended range and LE.

"Typically a carrier cycle runs 12h before we reset for maintenance and to bring up ordnance. What we want is to keep the battle group's eyes open and keep targets at risk even during the period the CAG is shut down," says Alderson.

Accordingly, the UCAV-N will have to operate at the opposite end of a normal carrier launch and recovery schedule, meaning it will need to remain in the air for upwards of 15h. This points to a vehicle with an empty weight of between 5,000-6,800kg, gross weight in the range of 11,800-18,200kg and occupying a deck spot comparable to that of a Boeing F/A-18C or Lockheed Martin F-35 JSF.

For greater flexibility the navy would like the UCAV to include an air refuellable capability, which brings with it the added complexity of tanking an unmanned vehicle using the probe-and-drogue method.

Another major design distinction for the UCAV-N will be the need to make it a fully used member of the CAG. Limited deck and hangar space will restrict the number of UCAV-Ns on board a ship if the navy is to avoid displacing some of its manned fighters and there will not be the luxury of an A-45-type containerised storage system. In addition, with the design of the navy's next-generation CVNX carrier already under way, design decisions are having to made well in advance of UCAV-N planned fielding. "If you're 15 years out on an aircraft programme, you've still got plenty of time - but if you're 15 years out on a carrier you're late," says Alderson.

The DARPA/US Army UCAR programme faces its own unique challenges, with the need to take armed UAVs into a whole new realm of operations. UCAR is intended to work alongside the Boeing AH-64D Apache and Boeing Sikorsky RAH-66 Comanche attack helicopters, which dictates a VTOL capability, although not necessarily a rotary-wing solution. There is also the requirement to perform collaborative autonomous operations at tree-top height for battlefield survivability.

"UCAR goes to the next level in that it will have to operate in an environment that is much more complex than either [Northrop Grumman] Global Hawks or UCAVs in that we envisage them operating in the low-altitude environment typical to the army," says Woodbury.

In addition to this is the UCAR's need to operate on its own or co-operatively with other manned and unmanned platforms, exchanging data, deciding how best to execute a mission, and replanning when an asset is lost or with new tactical data, while still remaining affordable. UCARs, like UCAVs, face big cost challenges, with the goal of capping the fly-away cost at 20-40% of that of a $20 million Boeing Sikorsky Comanche, and achieving a 50-80% cut in operating and support (O&S) costs over that of the Boeing Apache.

The USAF is aiming for an A-45 price one-third that of a $50 million JSF, and a 75% reduction in O&S costs compared to the latest Lockheed Martin F-16C/D Block 60. The USN is being slightly less ambitious, with the goal of 50% lower O&S costs than for an F/A-18C/D.

According to Wyatt, the real value of armed UAVs will be proving that they are capable of performing missions without putting pilots in harm's way. "It's my hope that, by the year 2020, we will have transitioned a lot of the dirty, dangerous and dull missions over to UAVs. If we can demonstrate they work, people will come and get them. If we fail, it doesn't make any difference, and no one is going to buy them," he says.

Source: Flight International