What sets the Liberty Lifter apart is its innovative design as a seaplane, intended to have a ferry range of 6,500 nautical miles (7,500 miles or 12,000 km). This range is substantial enough to cover the distance from the North Pole to the Equator, with a bit of reserve capacity. The Liberty Lifter represents a groundbreaking advancement in heavy cargo logistics, promising to revolutionize the transportation of large payloads over vast global distances.
The Liberty Lifter is engineered to transport substantial payloads across extensive distances.
In 2022, DARPA announced its ambitious project to develop an aircraft, the Liberty Lifter, which shares the size and capacity of a C-17 Globemaster III transport aircraft but can lift over 100 tonnes of payload. This is a remarkable feat, especially considering that a C-17 can manage about 77 tonnes on its best day.
What makes the Liberty Lifter stand out is its unique design as a seaplane, intended to have a ferry range of 6,500 nautical miles (7,500 miles or 12,000 km). This range is sufficient to fly from the North Pole to the Equator with a bit of spare capacity. The Liberty Lifter represents a significant advancement in heavy cargo logistics, promising to revolutionize the transportation of large payloads over vast global distances.
The ѕeсгet of this performaпce is what is called “groυпd effect” or “wiпg-iп-groυпd effect,” which is aп esoteric aerodyпamic pheпomeпoп that was at the ceпter of oпe of the great mysteries of the Cold wаг.
In the late 1960s, American spy satellites observing the Soviet Union witnessed an intriguing sight over the Caspian Sea. A massive aircraft, later dubbed the Caspian Sea Monster by the intelligence community, was tearing through the skies. Analysts were perplexed as this behemoth, weighing over 500 tonnes, sported thick, stubby wings that seemed inadequate to support its weight in flight.
This mysterious craft turned out to be an ekranoplan, part of a series of ground-effect vehicles developed by the Soviet military. These vehicles were designed to evade radar detection while carrying a substantial missile load, utilizing the concept of ground effect by flying at very low altitudes.
The critical element was the extremely low altitude. Ground effect occurs when an aircraft is flying very close to the ground or, preferably, water. Without delving into excessive technical details, when an airplane is moving forward at low altitude, it creates a cushion of air trapped between itself and the ground. Consequently, drag is reduced, and lift is increased, allowing the aircraft to either have smaller wings, carry a heavier load, or a combination of both.
This explains why the Caspian Sea Monster could be so large and fly with such stubby wings. Unfortunately, such ground-effect craft have severe limitations. One of the biggest drawbacks is that they work best flying over a surface of flat calm water and they definitely don’t like rough seas.
DARPA’s Liberty Lifter project aims to not only overcome some of these shortcomings but also to advance the technology further. The goal is to create an aircraft capable of ferrying heavy loads over a great distance, capable of landing and taking off on water to eliminate the need for runways. Moreover, it should be assembled using inexpensive boat-building techniques and operate for weeks without maintenance.
Additionally, it must be able to take off and land in Sea State 4, where waves reach as high as 8.4 ft (2.5 m), and operate on water in Sea State 5 with waves up to 13.1 ft (4 m). It must also function as a low-altitude aircraft that can fly out of ground effect to an altitude of 10,000 ft (3,000 m) above sea level.
For Phase 1 of the project, Aurora Flight Sciences, leading Gibbs & Cox and RecorCraft, is developing a craft resembling a traditional flying boat, with a single hull, high wing, and eight turboprop engines. Meanwhile, General Atomics and Maritime Applied Physics Corporation are working on a more exotic twin-hull, mid-wing design for better water stability and seakeeping, with propulsion provided by 12 turboshaft engines.
Phase 1 is expected to last 18 months, with six months of conceptual design work and nine months of design maturation before the results are submitted for a preliminary design review and test/demonstration planning reviews three months later. This will be followed by Phase 2 in 2024, where the successful design will move forward to design, manufacture, and demonstrate a full-scale Liberty Lifter X-Plane.
“We are excited to kick off this program and looking forward to working closely with both performer teams as they mature their point-of-departure design concepts through Phase 1,” said DARPA Liberty Lifter Program Manager Christopher Kent. “The two teams have taken distinctly different design approaches that will enable us to explore a relatively large design space during Phase 1.”