The intermediate semi-rigid was largely Italian and French in war use, though United States bought one ship after the war from the Italians, built one itself. The Germans also built smaller Parseval semi-rigids. The rigid airships are the largest, the non-rigids smallest. The rigid has to be large to hold enough gas to lift its metal frame along with the load of fuel, oil, crew, supplies, passengers and cargo. The blimps can be much smaller. The Army’s first airship, built by Major Tom Baldwin, old time balloonist, had 19,500 cubic feet capacity. Goodyear’s pioneer helium ship “Pilgrim” had 51,000 cubic feet. These contrast with the seven million feet capacity of the Hindenburg, and the ten million cubic feet of ships projected for the future. 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.