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By Dan Goure - Vice President at The Lexington Institute
Next Generation Air Warfare Will Require New Aerial Refueling Capabilities
Air-to-air refueling is the capability that allows airpower to achieve both reach and persistence. From the early days of flight, clever engineers worked on ways to refuel aircraft in flight. The dominant airpower nations are those that invested in aerial refueling capabilities, not only specially configured aircraft and the systems to transfer fuel, but the techniques that allow refueling operations to be integrated into air mobility and strike missions. The U.S. military has been a pioneer in the field of refueling and today possesses the largest and most capable fleet of tanker aircraft. The role of modern military tanker aircraft has expanded to encompass the transport of cargo and personnel and even conduct aeromedical evacuations. The challenge for both military planners and aerospace engineers is to develop advanced refueling capabilities that can address the threats and requirements of a changing air operations environment.
Aerospace and defense companies have been working on the technologies for aerial refueling for almost a century. The first air-to-air refueling was achieved in 1923 using a simple gravity flow hose. In 1948, Sir Alan Cobham demonstrated a probe-and-drogue fuel transfer system that proved so successful it has been deployed on most aerial tankers for the last seventy years. This was shortly followed by Boeing’s development of boom technology that has been central to the operations of U.S. Air Force aerial refuelers from the KC-97 Stratotanker to today’s KC-46A Pegasus.
Today, the United States is the dominant global airpower nation due, in large measure, to the military’s investments in aerial refueling capabilities. The U.S. Air Force operates the world’s largest fleet of tankers consisting of approximately 400 KC-135s and 59 KC-10s. The former relies primarily on a boom for fuel delivery although a special probe-and-drogue can be attached to the end of the boom, while the latter has both a centerline boom and a single probe-and-drogue. The U.S. Marine Corps and Air Force Special Operations Command operate variants of the KC-130 which use two underwing probe-and-drogue pods to refuel both fixed wing aircraft and helicopters. Currently, the U.S. Navy currently employs F/A-18 E/Fs as “buddy” refuelers for other F/A-18s.
The Air Force has a contract with Boeing to acquire 179 KC-46As to replace the oldest KC-135s. The KC-46A incorporates multiple new refueling technologies including a digital, fly-by-wire boom and a similarly controlled centerline probe-and-drogue system. It also will operate two wing-mounted probe-and-drogue refueling pods that are self-powered and digitally controlled.
Changes in the threat environment and the evolution of aerospace technologies are likely to have a profound impact on the way air-to-air refueling will need to be conducted in the future. Prospective U.S. great power and regional adversaries have invested in so-called anti-access/area denial (A2/AD) systems designed to counter U.S. power projection capabilities and to force air and sea forces to launch from greater distances from enemy territory. Even limited conflicts such as those in Southwest Asia place great demands on air-to-air refueling fleets not only to supply fuel, but to move cargo and personnel. In a future conflict against an adversary protected by A2/AD systems the activity levels of these fleets is certain to grow dramatically. Because they are so central to the ability of U.S. airpower to operate at long ranges and defeat A2/AD capabilities, refueling aircraft are likely to be targeted by enemy aircraft and long range surface-to-air missiles.
The next generation of air warfare will require new U.S. aerial refueling capabilities. Existing air-to-air refuelers will need advanced threat warning and self-defense systems. Because of the need to operate in contested airspace, some fraction of the future U.S. tanker fleet will have to be stealthy and could also be unmanned. The Air Force is looking for advanced, even revolutionary, aircraft designs for its future KC-Z tanker.
New tanker platforms will require similarly innovative aerial refueling systems. These systems will need to speed refueling maneuvers and allow refueling operations to be conducted in adverse weather conditions. They will have to be able to refuel unmanned platforms. Actively stabilized drogue systems such as those being developed by Cobham are critical to improving refueling operations at night and in inclement weather. Such a system is also on the path to fully autonomous refueling operations by unmanned platforms. The Defense Advanced Research Projects Agency (DARPA) has been working with industry for more than a decade to develop the basic technologies to support fully autonomous refueling.
The first of the next generation of aerial refueling systems is already in procurement. This is the Navy’s carrier-based, unmanned and stealthy MQ-25A Stingray drone. The MQ-25A is intended to provide 14,000 pounds of fuel at distances of 500 nautical miles from an aircraft carrier, dramatically extending the operating range of the carrier’s air wing. The Stingray will use the same Cobham aerial refueling system used by Super Hornets when operating in tanker mode. The introduction of the MQ-25A will mark a turning point in military aviation. The Chief of Naval Operations, Admiral John Richardson, observed: “We will look back on this day and recognize that this event represents a dramatic shift in the way we define warfighting requirements, work with industry, integrate unmanned and manned aircraft, and improve the lethality of the air wing, all at relevant speed.”
The ability of the U.S. military to retain its preeminence in airpower will depend in no small part on how wisely it invests in aerial refueling capabilities. First, the Air Force must move forward with it procurement of the KC-46A to replace the aging KC-135s. Second, R&D on advanced technologies suitable for the futuristic KC-Z tanker must be adequately funded. Third, DARPA and the Services must support industry’s efforts to do the modeling, simulation, design and testing necessary to achieve autonomous refueling.
Dan Gouré*, Ph.D., is a vice president at the public-policy research think tank Lexington Institute. Goure has a background in the public sector and U.S. federal government, most recently serving as a member of the 2001 Department of Defense Transition Team. You can follow him on Twitter at @dgoure and the Lexington Institute @LexNextDC. Read his full bio* here.
By Dan Goure - Vice President at The Lexington Institute
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