The U.S. Navy may have passed over Lockheed Martin’s submission for its MQ-25 Stingray drone tanker program, but the company is still looking to make its mark in the aerial refueling sector with the U.S. Air Force’s KC-Z tanker project. The firm’s legendary Skunk Works special projects office is crafting various proposals, including stealthy hybrid wing body and flying wing designs, as well as a concept based around a fleet of smaller unmanned aircraft. The Maryland-headquartered contractor prominently displayed a model of one Advanced Tanker Concept, the hybrid wing type, below artwork depicting a different aircraft concept in action paired with the text “Rapid Global Mobility,” at the Air Force Association’s annual Air, Space, and Cyber conference earlier in September 2018. Lockheed Martin first unveiled this particular design concept in 2016, which was itself an outgrowth of earlier work the company had done as part of the joint Air Force-NASA Speed Agile project. On the show floor, a representative from Skunk Works told The War Zone that the goal was to provide the Air Force with a set of tiered options as the service continues to iron out its requirements for the future KC-Z. They added that the USAF had not yet indicated to them what type of aircraft or operating concept it might be leaning toward at present. That being said, earlier in 2018, the Air Force Research Laboratory showed off its own model of a stealth tanker concept with the title “Advanced Aerial Refueling.” Stealthy or low-observable features that reduce the aircraft’s radar and infrared signatures will be core components of any final design. Traditional airliner-based tankers, such as the Air Force’s forthcoming Boeing KC-46A Pegasus, will only become more vulnerable to steadily improving ground-based air defenses, advanced combat aircraft, and associated radars and sensors, as time goes on. At the same time, U.S. military combat aircraft, especially fuel-hungry stealth combat jets that cannot carry typical range-extending external drop tanks without losing their low-observable edge, are going to continue needing tanker support in these high-risk areas. The War Zone made a detailed case for this exact capability on multiple occasions in the past, which you can read in full here and here. The Air Force intends to fill this emerging stealth tanker gap with KC-Z, but it remains to be seen what else it might expect these aircraft to do. The Skunk Works representative said that those secondary requirements may be among the biggest drivers in the in the configuration of the final design. The Advanced Tanker Concept model that Lockheed Martin has publicly shown features a conventional wing-and-tail configuration with hybrid wing body planform. This is specifically to provide the internal space and allow for other features, such as rear loading ramp, necessary for the notional aircraft to adequately fill the “C” role, or cargo carrying function, in KC-Z. Though it doesn’t get nearly as much attention as the tanking aspect, the Air Force’s existing KC-135s and KC-10s, as well as the new KC-46A, are all set up to move cargo and personnel as necessary and do so routinely. If the Air Force were to replace any significant portion of them with an aircraft that cannot perform this mission, the service could find itself creating a new gap in logistical capabilities. If the Air Force did decide to turn KC-Z, at least in part, into simply K-Z, Lockheed Martin says a flying wing design could be more efficient and potentially stealthier. Though the company did not bring a model of this concept to the Air Force Association gathering, the representative from Skunk Works described it as akin to a scaled up version of the firm's pitch for the Navy’s MQ-25 competition. KC-Z requirements that allow for a flying wing design could open the door to a submission from Northrop Grumman, as well, which could leverage its extensive experience in this arena and continuing work on the B-21 stealth bomber to create a "KB-21" tanker derivative. The Air Force actually investigated what it might take to transform the B-2 stealth bomber, another Northrop Grumman product, into an aerial refueling platform, though it decided not to pursue that plan and has never made details about that study public. “Imagine MQ-25 with that [improved stealthy] signature ability and perhaps longer legs,” Jack O’Banion, Vice President of Strategy at Skunk Works told Aviation Week in a separate interview. “Most tankers carry fuel in the wing to distribute the weight of the fuel with the lift of the wing, and since that is what the majority of the payload is, we’re doing an all-wing design,” John Vinson, who had led Lockheed’s Stingray program, had told this same outlet when talking about the Stingray back in March 2018.
Lockheed Martin is providing the US Air Force (USAF) with proposals for a large number of unmanned refuelling aircraft. In designs for the KC-Z project, a stealth tanker to refuel military stealth jets, one concept is to provide smaller unmanned aircraft, to be used in conjunction with traditional tankers, delivering fuel in high risk areas. The idea behind this approach is that it will allow more stealthy aircraft and tankers to operate at lower altitudes, which could reduce their radar cross section (RCS) or increase their ability to detect enemy radars. This means military opponents, such as Russia and China, would have to spend more resources in hunting down these smaller aircraft.