The Walrus HULA (Hybrid Ultra Large Aircraft) project was a DARPA-funded experiment to create an airship capable of traveling up to 12,000 nautical miles (about 22,000 km) in range, while carrying 500–1000 tons of air cargo.
DARPA said advances in envelope and hull materials, buoyancy and lift control, drag reduction and propulsion combined to make this concept feasible.
Technologies to be investigated in the initial study phase included vacuum/air buoyancy compensator tanks, which provide buoyancy control without ballast, and electrostatic atmospheric ion propulsion.
The WALRUS could potentially expand and speed the strategic airlift capability of the United States substantially while simultaneously reducing costs.
A smaller scale demonstration was scheduled for 2008, when a small scale version of the WALRUS designed to carry only the capacity of a C-130 Hercules (i.e., 18,000 kg or about 40,000 lbs) was expected to fly.