All-metal steam-powered zeppelin: Could it work?

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By Finn J.D. John
February 21, 2016

IRONICALLY ENOUGH, IT was on the first day of winter — the winter after the 1929 stock-market crash that kicked off the Great Depression — that Oregon inventor Thomas B. Slate’s dream of a business empire built on shiny silver steam-powered airships received its death blow.

Slate had left his native state several years earlier and made a fortune by inventing and commercializing the production of “dry ice” — frozen carbon dioxide. Then he’d left, sold his company, and moved to Glendale, Calif., to launch a new venture: A nationwide line of passenger airships based on a revolutionary design he had worked out.

An artist’s sketch of what the City of Glendale and its future sister ships might look like in service. (Image: Benton County Historical Society)

At first glance, the design looked ridiculous — like a piece of science-fiction hopefulness sketched out by an amateur without the benefit of any scientific or engineering knowledge. This initial appearance — together with the fact that Slate was best known for his innovations in dry-ice manufacture rather than for his aeronautical work during the First World War — has fooled more than one observer into assuming its inventor was just another rich guy with too much money and not enough knowledge, trying to force the laws of physics to conform to his dreams.

He wasn't. Thomas B. Slate was the real thing. And so was his crazy airship.

A coverage map showing the anticipated airship service which Thomas B. Slate hoped would soon be provided by Slate Aircraft Co. dirigibles. (Image: Benton County Historical Society)

The Slate dirigible was shaped like a colossal teardrop, with a big blunt front and a tapering-away tail. A long, streamlined cabin stretched along the bottom, with room for about three dozen passengers and crew to dwell in comfort and luxury during the anticipated 36-hour transcontinental journeys the airship would make.

Its hull was made entirely of aluminum, built in strips that were folded together in a specially patented gas-tight manner and riveted in place, with deep symmetrical grooves leading from the nose back to the tail. At the front of the hull, on the tip of the nose, could be seen an improbably tiny, odd-shaped fan or propeller of sorts; at the tail, an equally improbably tiny set of control surfaces — rudder and horizontal stablizers.

These elements were at the heart of the revolutionary design that Slate had created. The fan on the front was an impeller — a steam-powered blower that sucked great volumes of air out of the space just ahead of the airship and blasted it out to the sides in a great sheet of wind. This sheet of wind would be drawn to curve around the front of the airship by the venturi effect, creating a cushion of moving, partially-evacuated air that would suck the hull forward even as it buffered the big airship from atmospheric turbulence. This artificial wind would have abated considerably by the time it reached the tail surfaces, but would still be quite strong enough that only very small ailerons and rudders would be needed.

Pipe-dreamy as this plan sounded, it apparently worked fantastically well — at least, it worked fantastically well on the scale models Slate had tested in the wind tunnel at New York University. If the models scaled, Slate reckoned the full-size dirigible would require just 400 horsepower to transport 21,000 pounds of airship, passengers, crew and luggage through the air at up to 100 miles per hour.

This propulsion system would make Slate’s design ridiculously cheap to operate. In addition, the system of offloading passengers via an elevator car traveling up and down a cable hanging beneath would make it possible to operate with complete independence of airfields and other expensive ground infrastructure — except for hangars to park the big things in when not in use.

Slate envisioned a nationwide airline network served with his big silver-teardrop airships shuttling passengers anywhere and everywhere in comfort, luxury, and profitability. And the first step toward that goal was to get his first prototype model into the air, so that all the doubters could see that his revolutionary propulsion system would work.

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Thomas B. Slate inspects a couple of scale models in the hangar with the City of Glendale. The model he is handling appears to be a prototype of a more conventional design. (Image: Slate Aircraft Co.)

So the inventor got busy in his giant blimp shed, working on construction of the first model — which, with an eye toward public relations, he dubbed the “City of Glendale.”

Throughout the spring, summer and fall of 1929, the City of Glendale took shape. City residents flocked to the airfield on each of the days when it was taken out and tested. Slate worked tirelessly to get the big airship ready for its maiden voyage.

As the ship neared its launch date, Slate made a few changes here and there; the high-pressure boiler was giving him trouble, so he left it out and purchased a big radial aircraft engine. It’s not clear whether this was a temporary measure for testing, or if he’d actually given up on steam as a power distribution system.

Workers assemble the aluminum hull of the City of Glendale. (Image: Slate Aircraft Co.)

Finally, the big day came. In what would later seem a bitterly ironic twist, it was the first day of winter. But it was a warm day, and a beautiful one. Out came the City of Glendale, ready to show what it could do.

But as the Slate Aircraft Company crews busied themselves getting the big airship ready, the warm Southern California sun was beating down directly on the aluminum hull, and it was warming up. Soon the hydrogen inside was expanding … and it soon became clear that the pressure-release valve had gotten stuck.

A sharp, explosive pop rang out. Bystanders ducked; it sounded like a gunshot. And then came another, and another. Rivets were being torn out of the big dirigible’s hull.

And then, with a sigh of escaping gas, the City of Glendale settled wearily down onto the tarmac and lay over on its side.

The hangar and offices of the Slate Aircraft Co. in Glendale, Calif. (Image: Slate Aircraft Co.)

Slate was, of course, dismayed. But as yet he had no idea that his dream had just been destroyed. That came when the big dirigible was back in the shop, a week or two later, when he and his construction crews came to a horrible realization:

The envelope was not fixable. Because of the way each piece of aluminum interlocked with every other piece, the only way to replace the missing rivets and torn strips of aluminum would be to disassemble the whole thing, like a jigsaw puzzle, and start from scratch.

Had Slate used screws instead of rivets, that would have been do-able, although hardly pleasant. But when he’d engineered the big dirigible, he hadn’t even considered the need to periodically repair pieces of the hull.

Slate got busy immediately, trying to raise the funds he’d need to build a second model. But the world had changed radically just two months before, on Oct. 29, 1929. The country was just plunging into what would become the Great Depression. Investors had stopped investing and started trying to salvage as much of their nest eggs as they could. There was no money available.

Some attempts were made to restart the project after the disaster. Nothing worked out, though. Finally, in 1931, the Slate Aircraft Company filed for bankruptcy.

After the company failed, Slate’s son Claude took the lead in trying to interest others in picking up where his father had left off, even sending a proposal to the U.S. Congress with an eye toward earning a grant. Nothing came of this at the time, probably partly because of the counterintuitive nature of the engineering systems Slate developed. After 1937, reviving the idea became almost an impossibility, as the Hindenberg disaster had soured nearly everyone on the very idea of airship travel.

Eventually, Thomas Slate and his family found their way back to Oregon, and settled back into life in Slate’s old home town of Alsea. He continued to invent things, and his patent filings continued to show a Tesla-like ability to reimagine and innovate. They included a cyclone-generating device for removing smog from the air and a radically reimagined flying-boat design.  He died a week before his 100th birthday, on Nov. 26, 1980.

(Sources: Slate Aircraft Co. Website,; Benton County Historical Society,; Flight Magazine, Feb. 7, 1929; Radecki, Alan. “Slate’s Strange Dirigible,”, 20 Aug 2013)

TAGS: #PEOPLE: #doers #inventors #promoters #largerThanLife :: #MYS: #alternateHistory :: # #aviation #fail #unluckyBreak #badTiming :: LOC: #benton

Background photo is a hand-tinted image of the Conde McCullouch-designed bridge over the Willamette at Oregon City, published circa 1930 on a picture postcard.
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