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The Akron Class Airship: The Eyes of America’s Fleet

Now relegated to orbiting football stadiums and advertising tires, airships once served a grander, more high-stakes purpose. In fact, during and after World War I, it looked like zeppelins, the ancestors of our modern blimps, were going to become a decisive part of any global power’s war arsenal.

The US military was no exception, and their rigid airship program culminated with the Akron class and its two airships measuring a whopping 240 meters in length, about 785 feet, which is roughly the height of the Seattle space needle. They were capable of long-range reconnaissance and even carrying aircraft.

These airships pushed the limits and beliefs about airship engineering at the time and to this day remain the largest airships ever built in the United States.

Zeppelins

Rigid airships like those of the Akron class are A type of dirigible (a more technical word for airship) commonly referred to as “zeppelins.” That’s because they were invented by German aristocrat and military general Ferdinand von Zeppelin in 1900. He perfected his design by 1906, prompting the German Imperial Army to purchase the first military zeppelin, the LZ-4 in 1908. It was 136 meters long or about 446 feet.

Unlike modern semi-rigid airships, which we call blimps, and non-rigid airships, zeppelins are classified as rigid airships because they rely on a rigid metal frame structured around parallel rings running the long cylinder of the airship. These rings support separate, individual gas bags. This design allows them to be much larger than non-rigid airships, which consist of basically a single balloon.

Though modern airships exclusively use helium, access to this gas was limited at the beginning of the 20th Century, so manufacturers filled the gas bags with hydrogen instead. Hydrogen is extremely volatile and reactive, though, and led to many explosive accidents on these early models.

Despite the fiery fates of many of the early zeppelins, they still caught on quickly, especially in Germany. By the First World War, the German commercial passenger zeppelin line DELAG had flown over 3,000 total hours and transported nearly 35,000 passengers.

In World War I, the focus turned to zeppelins’ military potential. While Britain and France constructed and utilized a handful of zeppelins, the Imperial German military built a total of 95 and used them to bomb Belgium and England.

US Late to the Party

The US military showed little interest in zeppelins until they captured one, the L-49, from the German military after forcing it down over France in 1917 towards the end of World War I. The Americans suddenly wanted in and, when World War I ended in Allied victory, demanded Germany give them two as part of their reparations.

Unfortunately for the US, Germany scuttled most of its airships by the end of the war, so the two governments came to an alternate agreement. Germany would build a brand new zeppelin for the US, and the US Navy would use the same plans and expertise to build one of their own.

Apparently the German factories had less motivation to make an airship for free for another country because in 1919, the US Naval Aircraft Factory actually turned out their zeppelin first, the ZR-1, given the official designation of USS Shenandoah, based on the design of the captured German L-49.

The Shenandoah was an engineering marvel. It weighed over 32,000 kilograms or roughly 36 tons. At 207 meters long, or 680 feet, it was so large there was only one hangar in the US that could fit it. It could travel 8,000 kilometers without refueling. That’s about 5,000 miles, which is enough to cross the Atlantic from the Eastern seaboard and still reach most European cities, most likely a purposeful design.

For all its engineering magic, the Shenandoah got caught in a thunderstorm in 1925 while making city flyovers and crashed in Ohio killing 14 of its 43 crewmembers. Nevertheless, the US military was hungry for more and commissioned the Akron class ships in 1926.

Goodyear-Zeppelin Inc.

If you’ve ever wondered why the Goodyear tire company seems to own the majority of modern blimps, it’s because they actually have a long history of building airships. In fact, the US military awarded the contract for the Akron class airships to the Goodyear-Zeppelin Corporation in 1928. This company was a subsidiary of Goodyear and a joint-venture between Goodyear Inc. and Luftschiffbau Zeppelin GmbH, the primary German zeppelin manufacturer.

Through this joint venture, the US military was able to take advantage of German scientists and engineers who led the field of airship design. Specifically, Karl Arnstein, the Chief Stress Engineer at Luftschiffbau Zeppelin, went to the United States to advise Goodyear on the construction.

Arnstein was a brilliant and innovative engineer who wanted to step away from the strict traditional techniques employed back in the Luftschiffbau Zeppelin offices in Germany. Moving to Ohio to help Goodyear with the Akron class gave him just the chance to do that, and he ended up remaining in the US for the rest of his life.

Radical Design

Arnstein and Goodyear wanted to make their zeppelins even bigger and more powerful. To do this, they designed the “Deep Ring” zeppelin frame.

Previously, rigid airships had been designed with multiple parallel rings consisting of a single metal girder looped back in on itself. With the Deep Ring design, Goodyear used pairs of rings that reinforced each other with support triangles. Made of duraluminum, an aluminum alloy, this frame was much stronger, allowing for a longer and presumably tougher zeppelin.

Arnstein added several other innovations to the design as well. For instance, he put three keels on the ships instead of the traditional single keel. This added control as well as structural support and access to certain compartments and the gas bags.

More importantly, Arnstein and his Goodyear colleagues greatly increased the Akron class’s aerodynamics over past airship designs. They did this primarily by eliminating things protruding from the hull.

Most notably, they stuck the 8 Maybach VL-2 engines inside the hull itself, something that had never been done before. Plus, they decreased weight relative to engine power by some 4 tons and increased aerodynamics, speed and fuel efficiency thanks to metal propellers that replaced the old wooden ones.

The engineers also decided to use helium instead of hydrogen, which was certainly safer but also drove up the price to fill the gas bags, a pretty big deal since the Akron class was designed to be bigger. As a result, they couldn’t rely on venting gas from the bags for buoyancy and had to include considerable condensers to collect water vapor from the air.

The collected water would compensate for the lost fuel, keeping the airship level. To rise, the Akron airships could release water, or they could condense more to drop.

Akron and Macon

Goodyear began construction on the first Akron class airship in 1929 in Akron, Ohio. They finished it in 1931 and designated it ZRS-4, or officially the USS Akron, named after its hometown. It then went to the Carolinas to start a mission with the US Navy Scouting Fleet.

Goodyear started building Akron’s sister ship Macon, or ZRS-5, immediately thereafter and finished it in 1933. It took part in several training operations and maneuvers before heading for its permanent home in California.

The two Akron class airships outdid all their predecessors. Besides their increased length and size that provided quarters for a crew of 60, the zeppelins’ 8 Maybach VL-2 engines were V-12 4-stroke-piston systems that produced 560 horsepower per engine.

The result: a max speed of nearly 130 kilometers per hour or 80 miles per hour, enough to break the highway speed limit in most places. At their cruising speed of about 20 kilometers per hour or 12 mph, they could travel 11,000 kilometers. That’s almost 7,000 miles, enough for Akron and Macon to cross the Pacific Ocean from California to Tokyo and keep on going.

The primary military purpose of the Akron airships was reconnaissance. The US Navy wanted one of each to cover each coast as part of the Scouting Fleet, a subdivision of the navy created in 1922 to provide reconnaissance to assist the main Battle Fleet, whose role was direct combat. The navy saw zeppelins as ideal for the Scouting Fleet because, well, they could see a lot farther from their high altitudes.

That isn’t to say Akron and Macon weren’t ready for battle, though. Each flew with 8 M1919 Browning .30-caliber machine guns. More impressively, the zeppelins actually carried up to five of their own aircraft. The aircraft of choice was the Curtiss F9C Sparrowhawk, a single-propeller biplane with its own pair of machine guns.

The planes could be lowered out the bottom of the Akron airships’ hulls on an “aircraft trapeze,” which would then basically throw them into action. These planes were supposed to increase the reconnaissance range, but it proved to be a poor use of their agile, fighter-plane design.

The Navy began to consider ways to use the zeppelins as aircraft carriers in battle and even refitted the Sparrowhawks to facilitate this, but disaster struck before this plan could come to fruition.

Live Fast, Die Young

Neither the Akron nor the Macon lived to see the combat they were so innovatively designed to take part in.

The Akron was the first to go in April of 1933 when it crashed into the North Atlantic. After battling storms over New Jersey, heavy rains and intense pressure changes over the ocean pushed the airship down until its tailfin hit the water.

william adger moffett
William Adger Moffett

The engine stalled out, and the Akron broke up in the waves. Of the 76 crew, 73 died including Rear Admiral Willian A. Moffet, one of the main proponents of the US rigid airship program.

Macon crashed in a surprisingly similar way. Strong winds from a storm near Point Sur, California, broke one of the tailfins. A piece of material flew off and punctured a gas bag causing a chain reaction of structural failures that caused the airship to lower into the Pacific Ocean. Having learned from the Akron accident, the crew had life vests this time. Only two men died in the crash while the other 81 servicemen survived.

Still, it was the end of rigid airships in the US military. Even the USS Los Angeles, sister to the Shenandoah and the only US military airship that didn’t meet a tragic end, was dismantled for scrap in 1939 before the beginning of World War II.

While many think of the Hindenburg disaster as the end of widespread zeppelin use and interest, the crashes of the Akron class airships was arguably just as significant. Since then the US military has hardly used airships at all, and those they do use have been non-rigid or semi-rigid. With the end of military investment in rigid airships, innovations in zeppelin technology stalled out and they became old news.

Recently, though, there’s been a resurgence in interest, mostly because, since they float, airships don’t require energy for lift, cutting down on fuel costs. Additionally, their large surfaces can be easily solarized to provide energy for the propellers.

Major investors including Google’s Sergey Brin as well as important aerospace companies like Lockheed-Martin are exploring ways to use zeppelins primarily for cargo transport and heavy lifting, especially in areas where the lack of paved roads makes other shipping modes inaccessible.

While any mass industrial or passenger use of airships still seems a long way off, it may just be the case that the Akron class zeppelins and the technological innovations that went into their limit-pushing design will have a legacy yet.

Sources:

“18 September 1928.” This Day In Aviation. https://www.thisdayinaviation.com/tag/maybach-vl-2/

“Hybrid Airship.” Lockheed-Martin. https://www.lockheedmartin.com/en-us/products/hybrid-airship.html

“Is Sergey Brin really building the world’s biggest aircraft? Here’s everything we know.” SFGate. https://www.sfgate.com/travel/article/Sergey-Brin-Google-airship-blimp-zeppelin-LTA-16030652.php

“Karl Arnstein.” Remarkable Ohio.org. Ohio History Collection. https://remarkableohio.org/index.php?/category/1371

“U.S.S. Akron (ZRS-4) and U.S.S. Macon (ZRS-5).” Airships.net. https://www.airships.net/us-navy-rigid-airships/uss-akron-macon/

“USS Los Angeles ZR-3.” Airships.net. https://www.airships.net/us-navy-rigid-airships/uss-los-angeles/

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