The following table will show the range of sizes:
Rigid Airships: Hindenburg (German) 7,070,000 cubic feet Akron-Macon (U. S.) 6,500,000 cubic feet R-100, 101 (British) 5,000,000 cubic feet Graf Zeppelin (German) 3,700,000 cubic feet Los Angeles (U. S.) 2,500,000 cubic feet R-34 (British) 2,000,000 cubic feet Semi-Rigids: Norge (Italian) 670,000 cubic feet RS-1 (U. S.) 719,000 cubic feet Non-Rigids: Navy K type (Patrol) 416,000 cubic feet Navy G type (Advanced Training) 180,000 cubic feet Navy L type (Trainer) 123,000 cubic feet Goodyear (Passenger) 123,000 cubic feet Pilgrim (Goodyear) 51,000 cubic feet
The Akron and Macon were 785 feet in length, the K type non-rigid, 250 feet long, the Navy "L's" 150 feet long.
Let's cut back now to the Montgolfiers. Progress was disappointingly slow. The simple balloon would only go up and down, and in the direction of the wind. Before it could be practical, men must be able to drive it wherever they liked, make it dirigible, or directable.
Ingenious men, Meusnier, Giffard, Tissandier, Renard, Krebs, many others worked over that problem through the entire nineteenth century. They devised ballonets or air compartments to keep the pressure up. They built airships of cylinder shape, spindle shape, torpedo shape, airships shaped like a cigar, like a string bean, like a whale. But the stumbling block remained, the need of an efficient power plant.
The steam engine was dependable, but once you had installed firebox, boiler and cord wood aboard, there was little if any lift remaining for crew or cargo. Giffard in 1852 built an ingenious small engine using steam but it still weighed 100 pounds per horsepower, drove the ship at a speed of only three miles an hour. Automobile engines today weigh as little as six pounds per horsepower, modern airplane engines one pound per horsepower.
Man experimented with feather-bladed oars, with a screw propeller, turned by hand, using a crew of eight men. Haenlein, German, built a motor that would use the lifting gas from the ship--coal gas or hydrogen. Rennard in 1884 built an electric motor, taking power from a storage battery.
But real progress would have to wait for the discovery of petroleum in Pennsylvania and the invention of the internal combustion engine. When the gasoline engine came in, in the 90's, the dirigible builders saw the long sought key to their problem.