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If Aurora's concept passes preliminary design review by 2025, it is expected to float and fly by late 2027 or early 2028 and then demonstrate the Liberty Lifter.
After General Atomics terminated the Liberty Lifter program under the Defense Advanced Research Projects Agency (DARPA), Aurora Flight Sciences (AFS) will continue designing an experimental large cargo seaplane. After General Atomics' design of the aircraft, the project's vision of carrying a payload similar to that of the C-17 Globemaster III could not be met.
The Pentagon announced last week that AFS, a Boeing subsidiary, had received “an $8.3 million modification to continue its mobility seaplane design,” according to Defense News. In February 2023, DARPA announced the selection of a team from General Atomics and AFS to develop a concept design for the Liberty Lifter seaplane Wing-in-Ground effects “full-scale demonstrator.”
General Atomics' design proposed an unusual double hull for the Liberty Lifter to make the aircraft more stable on the water. Concept art showed that the plane's nose would have been raised like a C-5 Galaxy to position cargo and allow the vehicle to roll onto a beach or shore.
Aurora's design is closer to a traditional large seaplane or flying boat aircraft, with a single-hull, high-wing configuration powered by eight turboprop engines. Another concept illustration shows a wing falling down with a float at the tip of the wing.
By February 2024, AFS announced that it had been selected for Phase 1 of the program. The concept aircraft operates on the unique scientific principle of being able to hover and move just above the water without actually touching the surface. These are known as 'ground effect' vehicles (explained later). The full name of DARPA's project is “Liberty Lifter Seaplane Wing-in-Ground Effect.”
At the time, AFS said the goal of Phase 1 was to “design, build, float, and fly an affordable X-plane that demonstrates innovative heavy-lift capabilities at sea.” The company will receive funding for six months to “review the conceptual design of a winged ground-effect seaplane.”
'General Atomics design is not suitable'
The report came from DARPA's Liberty Lifter program manager, Dr. Christopher Kent's statement is quoted: The General Atomics design could not meet the project's requirements “to create transformational change.” “When we realized that only one performer was meeting our aggressive schedule and technology goals, we streamlined the program to continue to deliver innovation.”
General Atomics Aeronautical Systems spokesman Mark Brinkley said in an email to Defense News that the company hopes to continue working with DARPA on other programs and wishes the Liberty Lifter program success.
“We all recognize that the Liberty Lifter concept represents a real technology change for future combat operations, and we have made a compelling proposal based on our significant experience and expertise,” Brinkley said. “You always want to win and keep doing these things, but more than that, we want to see the program thrive and deliver unique capabilities for the warfighter and the nation.”
What is a wing-ground effect vehicle?
Wing-in-Ground Effect vehicles, also called Ekranoplans, are hybrids between airplanes and ships. They move over the water without actually touching the water.
The International Maritime Organization classifies it as a vessel. However, the working principle is completely different.
They achieve their unique high speeds as they skim through water 1 to 5 meters (3 to 16 feet) high. Therefore, we can say that it shares some characteristics with seaplanes, hovercraft, and hydrofoils.
This aerodynamic principle is called “ground effect”. The formation of wingtip vortices increases the efficiency of the wing. However, this effect does not occur at high altitudes. This low-altitude flight makes you invisible to aircraft radar. Because of its water operations, there is no need for docks or runways, and its payload capacity is greater than that of a conventional aircraft of the same size.
While flying, they are close to the surface, making them difficult to detect by radar. However, 'sea skimming' is still unlikely to completely protect them from detection, as their large size makes them large radar targets visible to coastal radar. But U.S. planners continue to see relevance as a confrontation with China emerges in the Indo-Pacific region, where the logistics capacity to sustain a conflict is a key concern.
Design by Aurora Flight Sciences
The Aurora concept will employ a “robust and adaptable control system designed to meet the challenges of operations to and from sea level and at lower altitudes around waves and obstacles,” the statement added.
Operating on unusual aerodynamic principles, it requires a variety of sensors, avionics and electronics to control flight maneuvers. The company recognized the challenge in dealing with the complex engineering and physics involved.
For the “half-ship, half-plane concept,” AFS partnered with leading marine engineering firm, Gibbs & Cox.
It “combines aeronautics and naval design expertise to propose a flying modern Liberty ship.” It has also partnered with ReconCraft, an Oregon-based shipyard that specializes in marine engineering.
According to DARPA, the Liberty Lifter is currently in “Phase 1b,” set for preliminary design review in early 2025. If successful, AFS will continue to improve the design and then build the aircraft. AFS will then float and fly a demonstration of the Liberty Lifter, with first flight scheduled for late 2027 or early 2028.
DARPA’s vision
DARPA has specified a ferry range of more than 6,500 nautical miles (nm), capable of ‘hovering’ in ‘ground effect flight’ in up to 5 sea states (or waves up to 13 feet high). It can carry two United States Marine Corps (USMC) Amphibious Combat Vehicles (ACVs) or six 20-foot container units.
“Goals include takeoff and landing in sea state 4, sustained underwater operations down to sea state 5, and extended flight from ground effect close to the water, with the ability to fly out of ground effect at altitudes up to 10,000 feet above sea level. level,” DARPA said.
Defense News added that DARPA originally envisioned the Liberty Lifter to be roughly the same size and capacity as the C-17 Globemaster, but has since “scaled the demonstration program down to the size of the C-130 Hercules.” However, DARPA's fiscal year 2025 budget document states that once there is evidence that the concept works, future Liberty Lifter aircraft could be built at roughly C-17 scale.
The Globemaster has a wingspan of over 169 feet, a length of 174 feet, and a height of approximately 55 feet. It can carry 77,518 kg of cargo. By comparison, Hercules has a wingspan of more than 132 feet, and its longest variant is about 97 feet long and has a maximum height of 38 feet. One variant can carry a payload of almost 20,000 kg.