1879: Air Travel (GM’s Guide Preview)

Air Travel

Toward the end of the American War of Secession, the Confederacy obtained the designs of Henri Giffard, the first person to successfully fly a powered air vehicle. Desperate for a way to deal with the Union naval blockade, the Confederacy threw its limited resources at Giffard’s design. The resulting airship, known as a Giffard (accent on the second syllable, it’s French) in honor of the inventor, gave the Confederacy the ability to drop bombs on the Union blockade ships from an altitude where naval guns could not reach, and to move bales of cotton out of the country and critical supplies, such as medicines and rare elements, in. The decade since the end of the war has seen some advancement in Giffard design, and a few attempts at other approaches to powered flight. This section discusses both the Giffard and the alternatives.

Giffard Design and a Quick Lesson in Chemistry

Thus far, no one has produced a functional rigid frame gasbag. Most materials that would stand up to the wind and the pressure are too heavy, or present a danger of sparks, or are prohibitively expensive. Thus, the Giffard continues to use a flexible gasbag, generally shaped somewhat like a fat cigar. A rope net over the gasbag keeps it contained, and provides cables from which to suspend the gondola.

Generally made from the lightest materials available, airship gondolas range from a single deck somewhat resembling an open-top narrowboat to multiple-deck affairs requiring dual gasbags for support. Regardless of the number of decks, some parts of the design cannot vary, including the placement of the Kipp and the engine.

The Kipp apparatus generates hydrogen to fill the gasbag. This must be done not only before flight, but sometimes during, in order to boost the lift of the airship, or to compensate for the inevitable slow leakage of hydrogen through the gasbag’s fabric. Nothing has yet been found that hydrogen cannot permeate. Consisting of three squat cylindrical tanks stacked one atop the other, the Kipp creates hydrogen through a simple chemical reaction. The top tank contains hydrochloric acid, in a strength sufficient to dissolve human flesh in a matter of seconds. Any solution more dilute would just add water weight to the airship. The middle tank contains zinc chips, squares of nearly pure zinc about the size of a sovereign. The operator opens a valve and allows acid to pour down onto the zinc. The chemical reaction between the two releases large quantities of hydrogen, which is then sent through a flexible tube up into the gasbag. Another valve allows the effluent to drain down into the bottom tank. A skilled operator can control the reaction by opening and closing the valves, halting the flow of acid into the zinc chamber and leaving the effluent drain closed in order to keep the hydrogen pressure up and force the gas up into the gasbag, then closing the gas valve and opening the effluent drain and the pressure release to take the Kipp back down to inactive. Do it wrong and there’s at least five ways for the Kipp to explode, taking the entire ship with it. Customarily, the Kipp is kept inside an armored enclosure, one of the few uses of steel plating aboard the ship. A rope ladder, hardly more than ship’s rigging, extends up the side of the Kipp and beyond to the upper gas hose connection. Anyone other than the ship’s engineer attempting to climb the ladder under any but the most dire circumstances will be hauled roughly down, and should count themselves fortunate if all they receive is a thrashing.

Giffards use microsteam engines for weight issues and efficiency. Having no boiler, just a water supply tank, and using powdered coke cartridges, the microsteam engine takes up less room aboard the ship as well. The engine must be located aft, and on a multiple-deck gondola is put below. Wherever the engine is located, aluminium cooling fins protrude from the water recirculator through the hull. The fuel bunker, with its stacks of powdered coke cartridges, must be located next to the engine, usually on the far side of a fireproof bulkhead. The stack goes directly out astern from the engine, a long pipe with a conical spark suppressor at the end like one sees on American wood-burning locomotives, and with the blast-pipe routed into the stack as usual. The water tank for the recirculator tends to be the size of the engine or larger, taking up half the engine compartment all on its own. The engine turns a shaft that in turn drives a flywheel, with a transmission gearbox between it and the propeller shaft or shafts allowing the propeller(s) to be reversed without having to reverse the engine itself.

Giffard Operation

Flying a Giffard requires a pilot and an engineer at the very least. Having a captain who can direct the efforts of the crew and navigate helps considerably. Some airship captains are themselves pilots and will take the helm depending on circumstances. Larger Giffards need a few deckhands to see to general operation, assist the engineer with swapping out the coke cartridges and engine maintenance, and perhaps a gunner or two if the ship has weaponry. Given the criticality of the lift ratio, the lifting power of the gasbag to the weight of the gondola and its contents, no person serves aboard a Giffard in only one capacity, with the possible exception of the pilot.