David Brin - Existence

Meanwhile, the voice in her ear took on a strange, lilting quality. The next contribution must have come from an individual member. Someone generally appreciated.

“Come with me, higher than high,

Dropping burdensome things.

Lighter than clouds, we can fly,

Thoughts spread wider than wings.

Be like the whale, behemoth,

Enormous, yet weightless beings,

Soundlessly floating, the sky

Beckons a mammal that sings.”

Tor liked the offering. You almost wanted to earn it, by coming up with a tune…

… only the “hatch” was now just ahead, or above, almost pressing against her face. A throbbing iris of polyorganic membranes, much like the quasiliving external skin of the Spirit. Coming this close, inhaling the exudate aromas, made Tor feel queasy.

“Relax.” The voice was back to business. Probably led by the zep mechanic.

“You’ll need a command word. Touch that nub in the middle to get attention and say ‘Cinnamon.’”

“Cinnamon?”

It was only a query, but the barrier reacted instantly. With a faintly squishy sound, it dilated and the stringy stepladder resumed its programmed journey, carrying her upward.

Aboard old-time zeps, like the Hindenburg, the underslung gondola had been devoted mainly to engines and crew, while paying passengers occupied two broad decks at the base of the giant dirigible’s main body. The Spirit of Chula Vista had a similar layout, except that the gondola was mainly for show. Having climbed above all the sections designed for people and cargo, Tor now rode the throbbing ladder into a cathedral of lifter cells, each of them a vast chamber in its own right, filled with gas that was much lighter than air.

Hundreds of transparent, filmy balloons-cylindrical and tall like Sequoia trunks-crowded together, stretching from the web-floor where she stood all the way up to the arched ceiling of the Spirit ’s rounded skin. Tor could only move among these towering columns along four narrow paths leading port or starboard… fore or aft. The arrow in her specs suggested port, without pulsing insistence. Most members of the smart-mob had never been in a place like this. Curiosity-the strongest modern craving-formed more of these ad hoc groups than any other passion.

Heading in the suggested direction, Tor could not resist reaching out, touching some of the tall cells, their polymer surfaces quivering like the giant bubbles that she used to create with toy wands, at birthday parties. They appeared so light, so delicate…

“Half of the cells contain helium,” explained the voice, now so individualized that it had to be a specific person-perhaps the zep mechanic or else a dirigible aficionado. “See how those membranes are made with a faintly greenish tint? They surround the larger hydrogen cells.”

Tor blinked.

“Hydrogen. Isn’t that dangerous?”

Her spec supplied pics of the Hindenburg -or LZ 129-that greatest and most ill-fated ancient zeppelin, whose fiery immolation at Lakehurst, New Jersey, marked the sudden end of the First Zep Era, in May 1937. (Facts scrolled along the bottom, lured in by attention cues.) Once ignited- how remained controversial-flames had engulfed the mighty airship from mooring tip to gondola, to its swastika-emblazoned rudder, in little more than a minute. To this day, journalists envied the news crew that had been on-hand that day, with primitive movie cameras, capturing onto acetate some of the most stunning footage and memorable imagery ever to accompany a technological disaster.

Nowadays, what reff or terr group wouldn’t just love to claim credit for an event so resplendent? So attention-grabbing?

As if reading her mind, the voice lectured.

“Hydrogen is much lighter and more buoyant than helium. Hydrogen is also cheap and readily available. Using it improves the economics of zep travel. Though of course, care must be taken…”

As Tor approached the end of her narrow corridor, she encountered the trusswork that kept Spirit rigid-a dirigible-instead of a floppy, balloonlike blimp. One girder made of carbon tubes, woven into an open latticework of triangles, stretched and curved both forward and aft. Nearby, it joined another tensegrity strut at right angles. That one would form a girdle, encircling the Spirit ’s widest girth.

Tracking Tor’s interest, her spec spun out statistics and schematics. At eight hundred feet in length, Hindenburg had been just 10 percent shorter than the Titanic. In contrast, the Spirit of Chula Vista stretched twice that distance. Yet, its shell and trusswork weighed half as much.

“Naturally, there are precautions,” the voice continued. “Take the shape of the gas cells. They are vertical columns. Any failure in a hydrogen cell triggers a pulse, bursting open the top, pushing the contents up and out of the ship, skyward, away from passengers, cargo, or people below. It’s been extensively tested.

“Also, the surrounding helium cells provide a buffer, keeping oxygen-rich air away from those containing hydrogen. Passenger ships like this one carry double the ratio of helium to hydrogen.”

“They can replenish hydrogen en route if they have to, right? By cracking water from onboard ballast?”

“Or even from humidity in the air, using solar power.

“And yes, the readouts show unusual levels of hydrogen production, in order to keep several cells filled aboard the Spirit . That’s why we asked you to come up here. There must be some leakage. One scenario suggested that it might be accumulating in here, between the cells.”

She pulled the omnisniffer-a phone attachment-from her purse and began scanning. Chemical sensors were all over the place, naturally, getting cheaper and more acute all the time-just when the public seemed to want them. For reassurance, if nothing else.

“I’m not detecting very much,” she said. Tor wasn’t sure how to feel-relieved or disappointed-upon reading that hydrogen levels were only slightly elevated in the companionway.

“That confirms what onboard monitors have already shown. Hardly any hydrogen buildup in the cabins or walkways. It must be leaking into the sky-”

“Even so-” Tor began, envisioning gouts of flame erupting toward the heavens from atop the great airship.

“-at rates that offer no danger of ignition. The stuff dissipates very fast, Tor, and the Spirit is moving, on a windy day. Anyway, hydrogen isn’t dangerous-or even toxic-unless it’s held within a confined space.”

Tor kept scanning while moving along the spongy path. But hydrogen readings never spiked enough to cause concern, let alone alarm. The smart-mob had wanted her to come up here for this purpose-to verify that onboard detectors hadn’t been tampered with by clever saboteurs. Now that her independent readings confirmed the company’s story, some people were already starting to lose interest. Ad hoc membership totals began to fall.

“Any leakage must be into the air,” continued the voice of the group mind, still authoritative. “We’ve put out a notice for amateur scientists, asking for volunteers to aim spectranalysis equipment along the Spirit ’s route. They’ll measure parts-per-million, so we can get a handle on leakage rates. But it’s mathematically impossible for the amounts to be dangerous. Humidity may go up a percent or two in neighborhoods that lie directly below Spirit . That’s about it.”

Tor had reached the end of the walkway. Her hand pressed against the outer envelope-the quasiliving skin that enclosed everything, from gas cells and trusses to the passenger cabin below. Up close, it was nearly transparent, offering a breathtaking view outside.