In a report looking at options for strategic lift, the Congressional Budget Office says airships, such as the Walrus program that is in its initial development stages, “would be virtually independent of air bases and would be well suited to deliver combat-ready troops, along with their vehicles and other equipment, directly to their destinations.”

The Defense Advanced Research Projects Agency, DARPA, awarded two contracts in August for the first phase of Walrus development. The idea, if it works, is to have a hybrid airship capable of carrying 500 tons over 6,000 miles within a week, without refueling.

The Walrus is not a traditional blimp. It would use a combination of lighter-than-air or almost lighter-than-air characteristics, along with an airfoil-shaped hull that would provide additional lift. The aircraft also could have wings.

CBO, a nonpartisan analytical arm of Congress, likes the heavy-lift airship concept because it could do more than the airlift aircraft and surge sealift capabilities currently used when U.S. forces deploy.

“Delivering fully equipped units straight to their destination would reduce the time that units typically spend between arriving in a theater and beginning operations,” the report says. “Although not as prompt as conventional aircraft, hybrid airships could still begin arriving in the Persian Gulf region from the United States in about five days, assuming that the units they transported were ready for loading immediately.”

Fifteen airships could deliver 1,000 tons of cargo a day, three times as much as a fleet of 21 C-17 Globemasters, the report says.

Developing and buying 14 to 16 airships and operating them for 30 years would cost about $11.3 billion, the report says.

There are downsides to heavy airships, the report says. A big disadvantage is that they are vulnerable to antiaircraft fire because they fly lower and slower than traditional cargo aircraft.