It would have been physically impossible for such huge, cumbersome craft to fly had they not been constructed of paper.
The specially treated paper consisted of enormous sheets of strong papyrus, made of woven reeds beaten flat, soaked in glue, stretched over hollow plaster forms, layer upon layer, and then baked dry in brick ovens and stripped from their forms, resulting in something very like sections of light, tough, molded plastic. The oven-baked, glue-impregnated paper hulls are tough, strong, durable, and lighter than balsa wood.
In addition, every opportunity to lighten the sheer weight of the craft had been assiduously followed through. Keel, beams, masts, sternpost, sternpost, bowsprit, van ribs, and so on, were mere hollow tubes. Even the figurehead was merely a hollow paper-mold. As for the outboard wing-sections, the part of the wings which flapped up and down, they were constructed on the model of bat wings, with narrow paper tubes like unsegmented bamboo rods splayed out from a center rib. Silk webbing, tightly stretched and pegged like drumheads and soaked in wax for extreme stiffness, was stretched between the ribs.
Even considering the lightweight paper construction, and all other measures taken toward conservation of weight, the sky ships would still not have been able to fly had it not been for the gas compartments. The entire bilge and lower deck was pumped full of the buoyant natural gas much like helium or hydrogen, which also filled the hollow spaces between the double hull. This natural gas, geysers of which were found among the White Mountains where the Sky Pirates dwelt, was pumped into the hollow decks and hull under high pressure, and the nozzles were then unscrewed and detached from the input hoses, which transformed them, by the addition of a simple snap-on valve, to pressure cocks, permitting some of the buoyant gas to be ejected at need so that the ship could sink to a lower level when required to do so.
Once the bilge and hollow hull were pumped full of gas, they were sealed off and calked until airtight.
The frigate had two masts amidships, set side by side, rather than fore and aft, as on a schooner. Light shrouds, stretched from mast to mast, and thence to bowsprit and sterncastle, permitted the display of signal pennants and ensign. The mastheads also were fitted with observation cupolas.
Such frigates as the Jalathadar had a crew strength of thirty-five officers and men, and a company of eighty wheel men, organized in eight gangs of ten men each, serving on staggered watches.
The Jalathadar measured eighty-five feet long. Very broad in the beam and flat-bottomed, it was almost completely weightless, and could attain a speed that might seem surprising. The average cruising speed of such a ship, with a full complement of men and supplies aboard, was such as to permit us to voyage on an average of three hundred miles per day. With a strong tailwind, that cruising speed could easily be doubled, since, unlike sea-going vessels, our prow cut empty air, not waves of heavy water, and we were as light as a balloon. When you consider that speed is attained by muscle power alone, you can begin to appreciate what a marvel of ingenuity the Jalathadar and her sister ships represented.
Koja and I had once been slaves, lashed to the wheels that powered the movable wingtips that propelled the aerial vehicles of Zanadar through the skies, and we were thoroughly acquainted with the backbreaking labor that task entailed.
The wheel gangs aboard the Jalathadar, of course, were not composed of slaves but of free men, fighting men of Shondakor. Indeed, scions of the noblest houses and princes of the highest birth manned the wheels of the galleon, for gentlemen warriors whose lineage could boast the bluest blood in the kingdom had contended jealously for a place in our crew. Thus we could hardly drive these highborn adventurers like lowly wheel slaves, groveling beneath the lash.
Fortunately, however, the Jalathadar did not require the motive power supplied by the wheel gangs to maintain her progress through the golden skies of Thanator. Steady prevailing winds blew from south to north across the Grand Kumala and the mountain country beyond, and the weightless corsair of the skies could ride before these gale-strength aerial tides while the wheel gangs rested. So, having achieved the upper levels at which the airstreams rushed northwards, the wheel gangs were released from their labors to join us in the galley, and were then liberated from further toil to stroll about the several decks, enjoying the splendors of the view.
Riding a strong tailwind, we passed the first day’s voyage without incident, making more than three hundred and twenty miles before nightfall and employing the strength of the wheel gangs only at certain intervals.
During the night, we reduced speed to lessen the possibility of straying from our course, for such aerial travel upon the jungle Moon affords certain navigational hazards unique to Callisto.
But I shall soon have reason to discuss these problems, and will pass over them here.
The second day of our voyage dawned bright and clear, and I rose from my bunk, breakfasted lightly in my cabin, and went forth to the deck, ascending to the pilot house (or control cupola, as I should call it) to check the night log. We were on course, with a strong but steady tailwind. Glancing through the broad observation windows, I saw the trackless leagues of the Grand Kumala reeling away far below our keel, and once again reflected philosophically on the fact that those jungle paths beneath us were aprowl with ferocious yathrib and savage deltagar and other monstrous predators, while here aloft in a cloudless sky we floated across the world in utter safety.
Toward late afternoon of the second day our tailwind increased and began to pose a problem. It first became apparent when a deck officer called to my attention that the Kumala below was now hidden behind thick clouds, greatly reducing our visibility. At the extreme height at which the Jalathadar now rode the winds, we were actually above the clouds and could enjoy the queer experience of looking down at a cloudy sky.
Cloud formations are rather rare on Thanator, or, to be precise, are seldom particularly visible, at least from the land surface of the jungle Moon. The reason for this lack of visibility is that the skies themselves are composed of curious golden vapors, uniformly illuminated from horizon to horizon, and against this hazy dome of golden light what clouds there are, are very difficult to see. But from our present height, clouds completely obscured the jungle country below from our view. From horizon to horizon the land below was concealed behind a thick blanket of milky vapor. The sight was curious and novel, but seemed to present no particular hazards.
Somewhat later, however, the duty officer summoned me to the control cupola. This particular officer was a nobly born gentleman of high Ku Thad rank named Haakon. He was a tall, sturdily built, serious-faced man in his forties, steady, strong, reliable, with the rare ability to keep his head in a crisis. He saluted me gravely as I entered the cupola and called to my attention yet again the dense blanket of clouds which obscured the lands below from our vision.
“I have already observed the cloud formations,” I said easily, “and, since we do not have any reason to descend to a lower altitude for some time, can see no problem.”
“The problem, sir, is one of navigation,” he said simply.
I understood his meaning at once, and cursed myself for not realizing sooner the hazard our current lack of visibility presented, for navigation through the skies of Thanator is a problem doubtless unique to this world.