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Unmanned Combat Aircraft Program Takes Off

July 2004
By Henry S. Kenyon

Initial operational capability for the U.S. military is on the near horizon.

A new generation of highly capable robot aircraft soon may augment and perhaps replace manned platforms in high-threat combat operations such as suppressing enemy air defenses and deep strike missions. These vehicles are part of an ambitious U.S. Defense Department program to develop and field-test an unmanned aerial combat capability by the end of the decade.

In the span of a few years, unmanned aerial vehicles (UAVs) have moved from curiosities to vital sources of battlefield reconnaissance for warfighters. In an evolution that parallels manned aircraft, these observation platforms soon were armed to strike at targets of opportunity. But this was at best a partial solution, and more capable and dedicated strike aircraft promptly were in development. Although still years away from combat deployment, unmanned combat aerial vehicles (UCAVs) offer the U.S. military the potential to conduct a variety of operations in combat environments too dangerous for manned aircraft.

The Defense Advanced Research Projects Agency (DARPA), Arlington, Virginia, through its recently launched Joint Unmanned Combat Air Systems (J-UCAS) Office, is developing several unmanned platforms and an underlying software operating system to tie them together. According to J-UCAS Director Dr. Michael S. Francis, the office is structured differently from other agency operations. While DARPA offices usually have many research programs under their jurisdictions, the J-UCAS program is devoted only to UCAVs and their support systems, he explains.

A joint effort with the U.S. Air Force and U.S. Navy, the program’s staff primarily is drawn from these services and is concentrated at facilities such as Wright-Patterson Air Force Base in Ohio, the Patuxent River Naval Air Station in Maryland, and Edwards Air Force Base in California. The organization’s leadership resides at DARPA headquarters.

Because the J-UCAS program is a large and focused effort, its operation resembles an acquisition program rather than a research and development effort. But it is more than that, Francis maintains. “We combined the scheduling and cost discipline you would find in that kind of acquisition outfit. DARPA is known for doing things on the edge, and it’s that blend of those qualities that we’re trying to achieve,” he says.

More than a technology demonstrator, the program seeks to have a UCAV capability ready for operational assessment by 2007. The services will determine the usefulness of the aircraft and provide feedback for changing the technology, altering vehicle roles or even ending the program. “The goal is to give them the capability, not a system, not a set of platforms, but a capability or set of capabilities that fits their needs,” Francis offers.

The J-UCAS program is an outgrowth of earlier DARPA UAV efforts that began in the mid-1990s. The original program was called the Uninhabited Tactical Aircraft, which was the predecessor of the UCAV initiative. Francis notes that these were not platform-based programs. The aircraft were viewed as nodes in a system—an early version of the network-centric warfare concept.

The program seeks to fill three battlefield roles in order of priority: suppression of enemy air defenses/electronic attack, persistent surveillance and deep strike. But the nature of the platforms has changed over time. UCAVs originally were envisioned as being cheaper and more expendable in combat. “We are talking about the equivalent of a styrofoam cup. It’s reusable, but if you lose it or it gets crushed, you don’t care because it didn’t cost too much,” Francis explains.

The original concept aircraft were similar to the Boeing X-45A UCAV demonstrator currently undergoing flight tests. The goal was to have a relatively inexpensive vehicle that was reliable and capable of carrying many payloads and performing a variety of missions but not very survivable. According to plans, large numbers of these networked aircraft would operate in the battlespace, allowing units to retain a high degree of operational capability despite attrition.

But this operational strategy called for aircraft to be pre-positioned at forward bases or operated near battle zones. The September 11, 2001, attacks and subsequent operations caused a shift in U.S. strategic thinking. Because basing aircraft near global trouble spots could not be guaranteed, aircraft with greater ranges were needed. “It’s no longer an in-theater system,” he says.

As a result of this change, aircraft sizes had to be increased to carry more fuel and larger payloads. The J-UCAS UCAVs also are being designed for aerial refueling and carrier deck operations.

Altering mission requirements also meant redesigning the program’s support infrastructure. Francis notes that satellite-based communications, navigation and sensing now have become more important than they were for in-theater operations.

He adds that the program is not meant to replace manned aircraft. UCAVs are intended for use in dangerous, high-threat environments where survivability is a key feature. An important aspect of this is the design of the aircraft, which makes extensive use of stealthy, low-observable design technology to reduce radar and infrared signatures.

The J-UCAS office is developing two advanced UCAV designs: the Boeing X-45C for the Air Force and the Northrop Grumman X-47B for the Navy. The aircraft have been under development for nearly 18 months. Francis explains that the original program had three spirals that began with the X-45A and X-47A, which were pure flight demonstrators to prove the technology. The latest versions of the aircraft can carry modular sensor and weapons payloads, allowing them to be reconfigured quickly for specific missions. Francis notes that the next step in the program is to make the UCAVs ready for operational testing.

The basic service requirements for both UCAV designs are an operational range of 1,300 nautical miles with a 4,500-pound payload, a loiter time of 2 hours to 3.5 hours, and an ability to carry a variety of sensor and weapons systems. The X-47 being developed for the Navy must be able to land and launch from an aircraft carrier. Both aircraft must be air refuelable and capable of operating in civilian airspace.

Because of the stealthy shape of the UCAV designs, sensor placement is a challenge. The program is applying existing sensors to the aircraft, but the difficulty is shaping sensor apertures to the vehicles’ low observable silhouettes. “We are trying to leverage programs that are designing similar systems. In some cases, we’re putting one sensor ahead of another based on the user’s priorities,” Francis says.

The 2007 operational assessment not only will demonstrate the UCAVs’ capabilities, but it also will generate feedback from warfighters about technological improvements and tactical applications. Another important lesson that will come from the assessment is understanding how an adversary may counter UCAV systems. Francis notes that the main threat is not an individual missile battery or radar system, but rather a fully integrated modern air defense system operated by foes that can exploit a known weakness.

Communications issues such as bandwidth management and secure messaging remain vital to the program. “It’s the most precious thing out there. If energy is like gold, bandwidth is like diamonds—there’s only so much of it,” Francis says.

To manage bandwidth and provide accurate and timely sensor information, the aircraft must process as much data as possible onboard before transmitting it. This is currently difficult to do on smaller aircraft because of space limitations and the processing demands placed on onboard computers, but Francis believes that within four to eight years technological advances will significantly lower this hurdle.

Strides have been made in reducing the amount of bandwidth used to share information between platforms, but because UCAVs will interoperate with a variety of vehicles and systems, keeping communications pipes open continues to be a challenge. “I don’t have the luxury to double my bandwidth by laying a piece of fiber next to the old one. That’s the problem with the Internet thought process. This is a purely wireless environment. It may not be radio frequency, but it’s wireless,” he says.

Autonomy is another major part of the J-UCAS program. Unlike current UAVs, such as Predators that operate at low altitudes or Global Hawks that fly high above civilian airspace, the X-45 and X-47 are designed to fly at altitudes of 35,000 to 40,000 feet—normal cruising altitudes for commercial airliners. Francis explains that DARPA is currently working with the U.S. Federal Aviation Administration on a means to permit UCAVs to operate at these altitudes. A major challenge is to extend this capability for global missions, he says.

The UCAVs’ software operating system will permit a greater degree of autonomy than current UAVs. This is an important feature in situations where an enemy may jam communications. In addition, autonomy is important to speed the decision time to deploy weapons. However, Francis stresses that the final decision to commit lethal actions will remain with human operators for the foreseeable future. “That flexibility is what prevents your adversary from having the ability to move his target or to drive a school bus next to it,” he says.

The program also will create a common standard for UAV software development. Francis explains that his office views the underlying information technology architecture as more important than the individual platforms. Noting that any computer platform can operate on the Internet, he adds that a goal of the J-UCAS effort is to create a software system that will run on any UAV.

To achieve this level of interoperability, the information technology component of the program has been separated from the platform development group. Francis plans to create a separate business vehicle for managing this venture. He predicts that it probably will resemble a consortium. This arrangement not only will allow the two prime contractors to collaborate, but also will provide a third party to act as a broker to mediate any conflicts between them. The goal is to have the participants become very involved in the process. “They need to be part owners. I think of the operating system development as a time-share where you get fractional ownership based on what you contribute,” he says.

Coordination between the participants is vital because the operating system is the glue that holds the program together. “You can think of these things [the UCAVs] as peripherals. The operating system is responsible for everything from the ability to provide battlespace awareness for interplatform collaboration to maintaining the quality of service on the network,” Francis explains.


Additional information on the Defense Advanced Research Projects Agency’s Joint Unmanned Combat Air Systems Office is available on the World Wide Web at