The Defense Advanced Research Projects Agency (DARPA) in the US is hoping to revive the concept of wing-in-ground effect (WIG) and has selected two teams to develop designs for its ‘Liberty Lifter X-Plane Programme.’
In the first phase of the programme, two teams – General Atomics working with Maritime Applied Physics Corporation, and Aurora Flight Sciences working with Gibbs & Cox and ReconCraft – will define the craft’s design and capabilities for a potential full-scale demonstrator. DARPA says the aim of the Liberty Lifter is to demonstrate a ‘leap-ahead’ in operational capability for seaborne strategic and tactical heavy lift.
The Liberty Lifter demonstrator will, effectively, be a large flying boat similar in size and capacity to the C-17 Globemaster III transport aircraft. Goals include take-off and land in sea state 4, sustained on-water operation in up to sea state 5, and extended flight close to the water in ground effect with the capability to fly out of ground effect at altitudes up to 10,000 feet above sea level.
The two teams have distinctly different design approaches that will enable DARPA to explore a relatively large design space during Phase 1 of the programme. The General Atomics team has selected a twin-hull, mid-wing design to optimise on-water stability and seakeeping. It employs distributed propulsion using 12 turboshaft engines. Aurora Flight Sciences’ point-of-departure more closely resembles a conventional flying boat, with a single hull, high wing and eight turboprops for primary propulsion.
During Phase 1, DARPA will work with both teams and Department of Defense stakeholders to refine the Liberty Lifter designs with particular attention to operational needs and operating concepts. The Phase 1 contract awards are for an 18-month period with six months of conceptual design work and nine months of design maturation culminating in a preliminary design review. There will be an additional three months for manufacturing planning and test/demonstration planning reviews.
As currently scheduled, Phase 1 will transition into Phase 2 in mid-2024 with continued detailed design, manufacturing, and demonstration of a full-scale Liberty Lifter X-Plane. DARPA anticipates teaming with one or more Department of Defense and international partners for those activities and for the further development of the Liberty Lifter concept into an operational unit.
