Contenders for the U.S. Navy’s MQ-25 Stingray unmanned carrier-borne refueler displayed their solutions at this week’s SeaAirSpace event near Washington, D.C., organized by the Navy League. Lockheed Martin revealed its proposal, while Boeing and General Atomics Aeronautical Systems Inc (GA-ASI) also displayed models on their stands.

Unlike the other two contenders, Lockheed Martin is proposing a tail-less airframe. The company seems to be betting on the Navy's deciding that its previous requirement for a stealthy unmanned carrier-launched airborne surveillance and strike aircraft (UCLASS) should, after all, form part of the MQ-25’s eventual mission set. Lockheed Martin is also trading on the reputation for rapid delivery of its Advanced Development Programs (ADP) facility, aka The Skunk Works.

Unlike Boeing and GA-ASI, Lockheed Martin has not produced a prototype or pre-development air vehicle. “We did not want to get ahead of the Navy’s requirement,” said ADP president Rob Weiss. “We invested a lot of money in UCLASS and have demonstrated risk-reducing technologies to our satisfaction,” he continued. The Skunk Works recently revealed the first of a series of tail-less UAVs that it has developed since 2000 with company funds. At least one of these, the USAF’s RQ-170 Sentinel, has entered operational service.

Weiss said that Lockheed Martin’s proposed MQ-25 airframe would be powered by a GE F404 turbofan, the same as the F/A-18C/D Hornet, and use the same landing gear from UTAS as the company’s F-35C stealth fighter, to streamline carrier-based logistics support. Triumph Aerostructures would be another significant subcontractor, as it has been on the F-35, and on the Navy’s E-2D and Marine Corps’ V-22.

One of the many puzzling aspects of the MQ-25 iteration, is that the Navy has declared an urgent need to stop using F-18s as "buddy" refuelers to preserve airframe life, and yet the MQ-25 program of record does not foresee an operational capability until 2026. But Weiss said that the Navy “desired a rapid program” and that ADP would work with the Navy’s Maritime Accelerated Capability Office (MACO).

The MQ-25 design offered by Boeing Phantom Works is powered by a Rolls-Royce AE 3007 turbofan, as found on business and regional jets and the RQ-4/MQ-4 Global Hawk/Triton large UAVs. Having constructed a prototype for the UCLASS requirement as long ago as 2014, Boeing has been ground-testing it at St. Louis, including simulated carrier-deck handling. The company has said that if it wins the MQ-25 development contract, the resulting airframe would differ from this prototype, and the model on its stand at the Navy SeaAirSpace event showed some of these changes.

The MQ-25 must be able to deliver 14,000 pounds of fuel at distances of 500 nm from an aircraft carrier. The design offered by GA-ASI appears to be the largest of the three competitors. “We can carry substantially more fuel than the Navy’s requirement,” said GA-ASI business development manager Doug Hardison. Last week, GA-ASI said that it was flight-testing aspects of the MQ-25 requirement on its Avenger jets. GA-ASI previously described a heavyweight team for its bid, including Boeing.

Another puzzling aspect of the MQ-25 program is that, unlike for any previous U.S. military UAS program, the winning airframer will have to adapt to a control system provided by the Navy, which will act as “lead systems integrator.” Presumably, however, the contenders have been made familiar with that control system via the risk-reduction contracts that they each received in the fall of 2016.

A fourth such risk-reduction contract was awarded to Northrop Grumman. However, despite having amassed by far the most experience of carrier-borne unmanned operations during the government-funded X-47B program, Northrop Grumman declined to bid for the MQ-25 development. The tailless X-47B first flew in February 2011, performed carrier deck trials in December 2012, and subsequently made carrier launches and recoveries.

Reportedly, Northrop Grumman was not comfortable with the terms of the “fixed-price incentive, firm-target contract” that the Navy is offering. Another reason for not bidding could be that the Aerospace Systems business sector of Northrop Grumman is already working at capacity on other Pentagon programs. It has won the B-21 new stealth bomber development contract; is still developing the RQ-4/MQ-4 high-altitude UAV; and is also producing a highly-classified penetrating ISR airframe that is now entering service with the USAF.