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“Lighter-than-air” airships were once a promising breed, providing an inexpensive way to move large amounts of people and cargo for long distances. But after the Hindenburg disaster in 1937, flight-by-buoyancy was all but abandoned by the aeronautics industry. Hot air balloons and blimps have seen occasional use, but the giant, rigid-airship zeppelins were all dismantled by 1940, and have hardly been seen since.

Now the U.S. Army is taking another look at the technology, with plans to develop a vehicle which harks back to the buoyant days of the zeppelins; however this new design is not intended to be “lighter-than-air,” rather it is a hybrid combining aerodynamics, thrust vectoring and gas buoyancy. Combining these three forces, the Army hopes to develop a cargo vehicle which can haul more than five hundred tons over very long distances, and land almost anywhere. The concept is called the “Walrus.”

Zeppelins were briefly used by the German military during the First World War, primarily for bombing and reconnaissance missions. But their vulnerability to gunfire from the Earth and from other aircraft made them impractical, and they were quickly abandoned as a military vehicle. The rigid airships which followed were used to transport people and cargo, and until the Hindenburg took the entire zeppelin industry down in flames, the reliability and endurance of lighter-than-air vehicles was very promising.

Some new technologies should make this latest foray into buoyant airships a bit more practical for the military. This design will still be vulnerable to gunfire due to its relatively large size and low speed, but its use will be limited to missions where the area in question is already under control, even if only temporarily. The Army envisions a vehicle which can transport an entire Unit of Action⁠— including 1,800 infantry plus armor support⁠— from its operational base in the U.S. to the theater of combat… wherever that may be. This factors into the military’s “10-30-30” objective: deploy to a distant theater in 10 days, defeat an enemy within 30 days, and be ready for an additional fight within another 30 days.

By way of comparison, the military’s current cargo workhorse⁠— the C-130 Hercules⁠— holds about 22 tons the C-5 Galaxy⁠— holds about 150 tons (thanks Avenger). In order to lift the 500-1,000 tons as required in the specifications, it is estimated that the Walrus will be about 1,000 feet long, with a size roughly comparable to an aircraft carrier. Despite its size, it does have one large advantage over cargo planes such as the C-5: the Walrus’ design allows the vessel to land practically anywhere, with no need for a landing strip … or even land, for that matter. The Army’s requirements call for a craft which can land on “unimproved terrain” or on water.

If the design proves viable and cost-effective, the peacetime benefits of this technology are potentially great as well. The Walrus is planned to have a range of 6,000 miles which it can travel within four days, providing an inexpensive means of hauling large amounts of cargo great distances through the air.

The Defense Advanced Research Projects Agency (DARPA) has awarded funding to two contractors for the first phase of the Walrus program. If the design phase goes well, phase two should produce a smaller 30-ton-capacity prototype by 2007.

Further reading:
DARPA draft document on the Walrus concept (PDF)
Millenium Airship site (developers of a similar concept)