In August 2021, Darpa, ie the Pentagon’s agency dedicated to innovation, issued a request for information from industry with a view to developing a “new class” of aircraft capable of “s ‘break free from the operational limitations of traditional air and maritime transport platforms’ in order to transport a payload of 100 tonnes. All with an “extended out of ground effect to avoid obstacles” flight capability.
Ten months later, Darpa was able to unveil the “Liberty Lifter” concept, based on an aircraft combining the advantages of the seaplane with those of the Ekranoplan. Called to “revolutionize” air transport, this aircraft was also to be able to carry out search and rescue missions as well as amphibious operations.
Clearly, Darpa’s idea was to go beyond the concept of the Ekranoplan, which the Soviets developed during the Cold War. As a reminder, the principle of such a device is based on an aerodynamic phenomenon called “ground effect”. This results in an increase in lift and a decrease in drag at very low altitude.
An Ekranoplan has several advantages: by flying below radar coverage [entre 3 à 15 mètres d’altitude], it can operate in so-called “contested” environments and therefore thwart an adversary’s denial and access denial capabilities. Its large transport capacity allows [potentiellement] to free itself from maritime transport, vulnerable to mines and other submarines. Only, unwieldy, such a device can only be used in calm seas. And that’s why the “Liberty Lifter” will have to be able to fly at an altitude of about 10,000 feet, which will also make it a seaplane.
“The focus will be on using this aircraft in rough seas, providing it with high lift capacity at low speeds to reduce the impact of waves during take-off and landing,” said further explained the Pentagon agency.
Less than a year after specifying its expectations, Darpa has just selected two industrialists as part of this program, including Aurora Flight Sciences [filiale de Boeing] and General Atomics. And, according to the leader of the project, Christopher Kent, two radically different approaches will oppose each other.
Thus, General Atomics defends a design with double fuselage [inaugurée par l’avion expérimental allemand Messerschmitt Bf 109 Z Zwilling, ndlr], with distributed propulsion based on twelve turbine engines. As for the approach of Aurora Flight Sciences, which has partnered with Gibbs & Cox, a subsidiary of Leidos, it is more traditional. [photo ci-dessus]. It is reminiscent of that of the Boeing “Pelican ULTRA”, a 152-meter-wide device capable of carrying 1,270 tonnes which could have been created if the credits intended for its development had not been cut in 2003.
From now on, the two industrialists have fifteen months to refine their work… and three months will be given to them to manufacture a demonstrator for the launch of the second phase, i.e. in mid-2024.
That said, it is not certain that this program will go to the end… Everything will depend on its cost, the Pentagon having insisted on “affordable production” of the Liberty Lifter on a large scale. Hence Darpa’s request to use materials that are less expensive than “those used in traditional aircraft construction” and “available for purchase in large quantities”.
