DARPA is working on a sort of extremely big aircraft popularized by the Soviet Union to land on beaches in the future. The Pentagon's blue sky projects wing sees an ultra low-flying "Liberty Lifter" as a proficient transport and cargo plane for transporting products to shore effectively in locations where there are no ship-friendly ports, according to a video released on May 18.
Consider the phenomena known as the "wing-in-ground effect" to understand why this branch of the DOD is interested in such a ship.
“There is a history of attempting to develop aircraft created to fly with ‘wing-in-ground effect,’ which means the aircraft is flying no more than the length of its wingspan above ground or water,” according to the DARPA statement. The Soviet Union created "ekranoplans," which were seaplanes that could travel fast and take off and land without runways, but were limited to calm seas and couldn't maneuver very well.
There are a variety of reasons why flying near to the surface is often a terrible choice, starting with the fact that planes are more exposed to the weather and are more likely to crash. Ground-effect planes, such as ekranoplans and DARPA's proposed Liberty Lifter, take use of the advantages of being low.
“At the lateral tip of the wing, the high pressure air underneath flows around to the upper surface. This creates a vortex, a rotating airflow that robs the wing of lift. But if the aircraft is flying very close to the surface, there is no room for the vortex to develop properly and it becomes weaker,” noted Bill Sweetman for Popular Science in 2003.
From the first observations of ekranoplans, the potential of the wing-in-ground effect could be seen. The jet-powered ekranoplan was initially featured in Popular Science in 1977, with claims that it was built for anti-submarine warfare and could reach speeds of 350 miles per hour. Eight jet engines were installed on a forward canard high on the plane's fuselage, allowing their exhaust to deflect down to the sea's surface. The Russian craft, PopSci wrote, “gets lift from [an] air bubble caused by jet blast bouncing off water beneath its main wings.”
DARPA's new Liberty Lifter takes its name from World Conflict II's "Liberty Ships," freight carriers mass-produced for use in the war and afterwards as commerce boats. The firm doesn't just want its "Liberty Lifter" design to fly by unconventional methods; it also wants the plane to be built in a cost-effective and scalable manner.
Liberty Lifters are envisioned for military usage as a way to transfer troops, vehicles, and freight to ports where the infrastructure to dock and unload items is lacking. This might be to aid disaster relief efforts or to enable an assault by rolling light armored vehicles carrying marines across tidal flats to inland targets.
DARPA wants the Liberty Lifter to be able to fly over turbulent seas like a typical airplane, even reaching altitudes of 10,000 feet, in order to go beyond the constraints of Soviet ekranoplans. That should make it easier for the Liberty Lifter to access rivers further interior, maybe even allowing it to go to and operate from lakes.
Prior to the Liberty Lifter, the United States sought for a means to tailor ekranoplan invention to its own requirements. Even though the models produced had limitations, an airplane that uses ground effect to “fly on less power, using less fuel, than one at high altitude," as Sweetman put it, has a lot of potential.
In 2003, Boeing considered developing the Pelican, a massive freight plane that could fly like a regular plane but would usually fly low to the sea, powered by the wing-in-ground effect and the thrust of jets aimed towards the water's surface. With a 500-foot wingspan, 400-foot length, and 29,000 square feet of cargo hold across two decks, the Pelican design was absolutely gigantic, capable of transporting 17 M1 Abrams tanks and hundreds of cargo containers. Later, the idea was shelved.
