The US Defense Advanced Research Projects Agency (DARPA) unveiled a concept on May 18 for a new heavy airlift seaplane dubbed the Liberty Lifter. DARPA says it has launched the Liberty Lifter project to demonstrate a leap in operational logistics capabilities by designing, building and flying a long-range, low-cost X-plane capable of seaborne strategic and tactical lift. The new vehicle concept seeks to expand upon existing cargo aircraft by proving revolutionary heavy airlift abilities from the sea, says DARPA.
The envisioned seaplane will combine fast and flexible strategic lift of very large, heavy loads with the ability to take off/land in water. Its structure will enable both highly controlled flight close to turbulent water surfaces and sustained flight at mid-altitudes. Although designed to take advantage of the benefits of wing-in-ground effect, DARPA says it will also be capable of flying at altitudes of up to 10,000ft. In addition, the aircraft will be built with a low-cost design and construction philosophy.
There has been a long 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. The most well-known examples are the Soviet ekranoplans. These vehicles were high speed and runway- independent but were restricted to calm waters and had limited manoeuvrability.
Alexander Walan, a programme manager in DARPA’s Tactical Technology Office, said: “This first phase of the Liberty Lifter programme will define the unique seaplane’s range, payloads and other parameters. Innovative advances envisioned by this new DARPA program will showcase an X-plane demonstrator that offers warfighters new capabilities during extended maritime operations.”
To address the shortcomings of existing vehicles and operational concepts, the Liberty Lifter programme focuses on addressing three main challenges:
Extended Maritime Operations: Emphasis will be placed on operating in turbulent sea states by creating high-lift abilities at low speeds to reduce wave impact load during take-off/landing and innovative design solutions to absorb wave forces. In addition, the project will address risks of vehicle collision during high-speed operation in congested environments. Finally, the aim is for the vehicle to operate at sea for weeks at a time without land-based maintenance activities.
Full-Scale Affordable Production: Construction will prioritize low-cost, easy-to-fabricate designs over exquisite, low-weight concepts. Materials should be more affordable than those in traditional aircraft manufacturing and available to be purchased in large quantities.
Complex Flight and Sea Surface Controls: Advanced sensors and control schemes will be developed to avoid large waves and to handle aero/hydro-dynamic interactions during take-off/landing.