In March 2010 the US Navy initiated the Unmanned Carrier-Launched Airborne Surveillance and Strike (UCLASS) program for an unmanned combat air vehicle (UCAV) with tactical strike and intelligence capabilities, issuing for Request for Information (RFI) for the program that month. Since the early 2000s, the Navy had made efforts to develop a UCAV, beginning with the Naval Unmanned Combat Air Vehicle (UCAV-N) program initiated in mid-2000 that produced the Northrop Grumman X-47A Pegasus and the Unmanned Combat Air System Demonstrator (UCAS-D) program (a rebranding of the Joint Unmanned Combat Air Systems (J-UCAS) program after the US Air Force quit in early 2006) that led to development and flight tests of the X-47B full-scale UCAV technology demonstrator. Although the X-47B was still undergoing taxi tests and had not yet flown by the time the UCLASS program was started, the Navy was sorely lacking a purpose-built replacement for the long-retired A-6 Intruder given that the stealthy A-12 Avenger II flying wing attack aircraft which was to have replaced the A-6 ended up being canceled in January 1991 after cost overruns and developmental problems before any aircraft could ever be completed. The UCLASS concept aircraft was to be a stealthy strike platform with a weapons load comprising twenty-four 250 lb (113 kg) GBU-39 SDB bombs and able to utilize a suite of modular and/or federated ISR sensors with all weather capability as well as EO/IR, multi-mode radar, and ESM. The Navy's roadmap for the future of its combat aviation capabilities called for deployment of the UCLASS by 2018.
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| Left: Computer-generated image of the General Atomics Sea Avenger derivative of the company's MQ-20 Avenger (originally Predator C). (courtesy of General Atomics) Right: Mock-up of the Lockheed Martin Sea Ghost in early 2013. (courtesy of Lockheed Martin) |
In response to the RFI issued for the new UCLASS program, three companies in southern California conceived designs for the UCLASS program that were based on existing designs. General Atomics, which is based near San Diego and has developed unmanned aircraft since the late 1980s, proposed a navalized version of the MQ-20 Avenger (originally called Predator C) as the Sea Avenger, which had an internal weapons bay, a retractable electro-optical/infrared sensor, and folding wings along with an arrestor hook, drag devices, carrier suitable landing gear, and other carrier compatible provisions. For its part, Northrop Grumman offered a derivative of the X-47B, being well-positioned to do so because of its experience with development of the X-47A and X-47B. In July 2012, Lockheed Martin unveiled a carrier-based derivative of the RQ-170 Sentinel stealthy unmanned tactical reconnaissance flying wing, the Sea Ghost, which would have the range and flight endurance of the A-6 Intruder but carry a smaller weapons load while utilizing open architecture avionics to enable new sensors or mission systems to be carried onboard over time. Like the F-35C naval variant of the F-35 Lightning II, the Sea Ghost was to incorporate sea spray optimized stealth materials, something that Lockheed Martin was most probably mindful of when it undertook design of the unbuilt A/F-117X naval derivative of the F-117 Nighthawk in the mid-1990s.
On December 19, 2012, the Defense Department's Joint Requirements Oversight Council (JROC) had the UCLASS requirements revised to make the program heavily favor permissive airspace intelligence, surveillance, and reconnaissance (ISR) capabilities because the Pentagon expected plans for a strike capability for the UCLASS to be constrained by its planned submission of its budget for FY2014. The payload capacity specified in the original requirement was revised to 3,000 lb (1,360 kg) comprising 1,001 lb (454 kg), and stealth requirements were sharply reduced to lower costs. The US Navy initially planned to issue a Request for Proposals (RFP) for the UCLASS program in late 2012, but this was delayed to April 17, 2014 due to disagreements over the UCLASS concept aircraft's degree of stealth, in-flight refueling ability, and ability to survive in contested airspace. While the Sea Ghost and the proposed derivative of the X-47B relied on stealth, the Sea Avenger and Boeing's proposed adaptation of the Phantom Ray (itself a reincarnation of the X-45C) preferred to emphasize range and payload rather than stealth. Even before the RFP was issued, on August 14, 2013, the Navy awarded $15 million development contracts to Boeing, General Atomics, Lockheed Martin, and Northrop Grumman to develop their UCLASS airframe designs.
Not too long after Boeing, General Atomics, Lockheed Martin, Northrop Grumman received contracts to refine their UCLASS airframe designs, in December 2013, the UCLASS concept aircraft evolved into a "heavy-end" strike/ISR aircraft with a length of 68 feet (21 meters), a weight of 70,000 to 80,000 lb (32,000 to 36,000 kg), an endurance of up to 14 hours, and greater room for weapons and sensors, making it comparable in size to the F-14 Tomcat and bigger than the X-47B and F/A-18E/F Super Hornet. The original UCLASS requirement parameter calling for providing daily ISR coverage from an aircraft carrier remained fixed, and one role explored for this revised UCLASS concept aircraft was an aerial refueling platform to refuel fighter aircraft. These revisions to the UCLASS concept aircraft were again due to cost constraints, but the four companies which had proposed designs for the UCLASS program pushed back against the revised requirements on the grounds that they required a drone far more capable than the Sea Ghost, Sea Avenger, and operational derivatives of the X-47B and Phantom Ray. The UCLASS concept was changed again on July 17, 2014, this time focusing on an unmanned aircraft whose missions initially were to include permissive airspace ISR and strike before eventually expanding to contested littoral and coastal ISR and strike missions and attacking enemy surface ships, and the designation ZRAQ-25A was allocated to the UCLASS program. The US Navy in December 2014 stipulated that E-2 Hawkeye squadrons would be given control over the ZRAQ-25A during aerial operations, and the Navy's FY 2016 budget request had the planned operational deployment of the UCLASS further delayed to 2022-2023 and an RFP for the revised UCLASS concept aircraft originally scheduled to be issued in September 2014 postponed due to an ongoing review of what roles would be performed by the ZRAQ-25A.
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| Left: Computer-generated image of the Lockheed Martin Sea Ghost refueling an F-35C (courtesy of Lockheed Martin) Right: Computer-generated image of the proposed adaptation of the General Atomics Sea Avenger submission for the CBARS competition (courtesy of General Atomics) |
On February 1, 2016, the US Navy shelved the UCLASS program in favor of the Carrier-Based Aerial Refueling System (CBARS) for an unmanned aerial refueling tanker the size of the Super Hornet and with minimal ISR capabilities, deferring the strike capability and some communications roles long envisioned for the UCLASS to a future variant of the CBARS, and in July of that year, the CBARS was officially christened the MQ-25A Stingray. The three companies from southern California which had proposed designs for the UCLASS program now adapted those proposals for the MQ-25 competition after an RFP for the MQ-25 program was issued in October 2017. While Northrop Grumman offered an X-47B derivative with reduced stealth and aerial refueling capability, General Atomics envisaged a slightly enlarged Sea Avenger iteration for aerial refueling while Lockheed Martin unveiled a revised Sea Ghost design with greatly reduced stealth. On October 25, Northrop Grumman withdrew from the contest after saying that it would be not able to properly manage development of its X-47B derived design if it aimed to win the MQ-25 contract.
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| The Boeing MQ-25 Stingray, which won the CBARS competition in August 2018. |
On August 30, 2018, the US Navy declared Boeing the winner of the MQ-25 Stingray competition. Back in 2014, Boeing had built in secret a wing-body-tail unmanned aircraft that incorporated lessons learned from the Phantom Ray and its other UAV programs when the UCLASS requirements were drastically revised, but it was not until December 2017 that this aircraft was unveiled as the Boeing submission for the MQ-25 contest. On September 19, 2019, the MQ-25 Stingray made its first flight, and 2021, it became the first UAV in history to refuel manned aircraft when it conducted refueling tests of an F/A-18F, F-35C, and E-2. Although the MQ-25 is mainly designed for aerial refueling, in April 2024 Boeing unveiled a strike/ISR variant of the MQ-25 armed with two AGM-158C LRASM stealthy cruise missiles below two underwing hardpoints, indicating that the Navy is keenly contemplating plans to give the Stingray the strike and ISR capabilities envisioned for the canceled UCLASS program. In this way, if the proposal for a strike/ISR variant of the MQ-25 does get built, it will not only fulfill the operational roles which the Sea Avenger, Sea Ghost, and Northrop Grumman's operational derivative of the X-47B were designed when first conceived but also function as a true successor to the A-6 Intruder in terms of providing the Navy with a purpose-built attack aircraft after the cancellation of the A-12 Avenger II program in 1991, the abortive A/F-117X and A/F-X programs of the mid-1990s, and the shelving of the UCLASS program in 2016.
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