I hadn't really given this much thought, but it makes sense that you don't want the weak link in the system to be refueling a stealth jet with a flying barn.To refuel the F-22 and F-35 deep in enemy territory, the Air Force is going to need something a little less obvious on a radar screen.
The U.S. Air Force Air Mobility Command recently announced the "KC-Z" program intended to develop a next-generation tanker aircraft--one that could fly into dangerous airspace to support strike fighters like the F-22 and F-35--by 2035. Lockheed Martin was the first to answer the call for ideas, and that company recently released design information about a hybrid wing-body aircraft with short take-off and landing capabilities, according to Aviation Week.
Although the new tanker wouldn't have a high level of stealth, the low profile of a blended wing-body airframe would naturally produce a smaller radar cross-section than current tankers. (The KC-10 Extender and KC-135 Stratotanker, and even the KC-36 Pegasus that is currently under development, all have large-body designs similar to commercial airliners.) Lockheed is also considering embedding the engines within the airframe to keep the KC-Z as stealthy as possible to avoid radar detection, surface-to-air missiles, and other anti-aircraft weapons.
Lockheed has already begun wind-tunnel testing on a four percent scale model of a new Hybrid Wing Body (HWB) airlifter designed for maximized aerodynamic efficiency. As Lockheed's aerospace engineers conduct flight tests on the 45-pound HWB model, they could use the data not only to develop the HWB but also to jumpstart a tanker program with a similar blended wing-body design.
The new tanker would have a few necessary design changes compared to the airlifter, though. The airlifter is designed with a "T" tail to accommodate airdrops, for example, while the tanker is more likely to have an "H" tail to keep the aircraft's radar profile low while adding stability and enhanced flight control. The external overwing nacelles on the airlifter that support large, fuel-efficient high-bypass engines might be replaced with either two or four embedded engines on the tanker for improved stealth, as Kenneth Martin, Lockheed Martin's principal engineer for advanced mobility, told Aviation Week.
Martin suggested the KC-Z could include both offensive and defensive countermeasures, such as stealth coating or even lasers defenses. He also says that automating the refueling process would reduce the amount of time needed to top off other aircraft, thereby improving survivability, since the act of refueling leaves aircraft vulnerable to detection by radar or even direct attack. Martin said to Aviation Week:
"If we believe Google and others that we'll all be operating self-driving cars, it seems to us the technology is being matured across the entire [science and technology] community to allow significantly more automation. We're committing very hard to perhaps not totally eliminating the boom operator but recreating the operator's job to be a systems monitor; it could even be a copilot who is basically monitoring the process."
The Air Force's official study on the next-generation tanker is expected to begin in the next six months. It is unclear at this point which aerospace companies other than Lockheed will submit design proposals for the KC-Z program, but with the HWB scale model prepped for flight, a tanker model could be entering Lockheed's wind tunnels sooner rather than later.