But who would have thought that zeppelins were a sacred cow? When I compared winged spaceplanes with rigid airships in a recent column, some zeppelin fans were outraged and sent me long essays defending their beloved gasbags against the shame of being mentioned in the same breath with Dyna-Soar or Space Shuttle! Is nothing non-sacred these days?

Actually, I am a closet zeppelin fan too. The "fascinating obsolete technology" section of my home library has a shelf of airship books crammed in between steam locomotives and sailing ships. I constantly scan used bookstores and the Internet for new theories of the Hindenburg disaster, or more hard data on the management structure of the British Empire Passenger Airship Program.

Why? For one reason, the great rigid airships have a lot of lessons to teach us about how technologies rise and fall. In particular, the problems that eventually killed the large airship are almost exactly the same as the ones that currently bedevil our space launch vehicles -- especially the Shuttle. (All numbers are from Zeppelin: Rigid Airships 1893-1940 by Peter W. Brooks, the most complete and balanced treatment of this subject.)

High Unit Cost -- The low lift/volume ratio of hydrogen and helium meant that airship designers had to make their craft very large to get useful amounts of lift. Even an X-zeppelin had to be large and expensive. In sharp contrast, the winged aircraft of the same era were so cheap that X-planes were thrown together by bicycle mechanics in barns and garages. Rocketships, like zeppelins, require years of sustained investment from a government agency or mega-corporation with extremely deep pockets.

Narrow Design Base -- There were never more than four independent airship design teams active at one time, and most of them were heavily dependent on Zeppelin Corporation design data acquired by purchase, espionage, or reverse-engineering of crash wreckage. (During this Golden Age of Aviation, there were dozens of airplane design teams at work, exploring every possible idea for improved performance.) The USA is now down to two major players in the launch vehicle market, with the Ariane team the only active overseas group not dependent on old US or Soviet technology transferred during the Cold War.

Narrow Contractor Base -- The shipbuilding, automobile, and airplane industries were able to develop a massive infrastructure of small private firms which developed and supplied the basic components. These markets were so big that intense competition between many suppliers fostered rapid technical development. In contrast, the Zeppelin firm had to form subsidiaries to develop such major subsystems as gas cells, engines, and gearboxes. The limited numbers of these specialized items needed by the airship community did not inspire venture capitalists to invest in them since it seemed unlikely that future sales would ever return the development costs. Airship designers not associated with the Zeppelin firm found themselves using components intended for airplanes or even railway locomotives.

Mammoth Ground Support Equipment -- Even one or two X-zeppelins required a huge investment in civil engineering: giant hangars, railroad lines, mooring masts, and gas handling plants. There were never more than a dozen fully equipped zeppelin bases in the entire world. And once finished, the hangars represented a huge sunk cost that forced future designs into the straightjacket of their fixed dimensions. Even today, maintenance of the surviving hangars are a financial burden for the unfortunate organizations that have inherited them -- just like the old Saturn launch facilities are for NASA.

Inappropriate Traditions -- The airship perpetuated the command & control style of the 19th-century steamship. A "watch officer" gave verbal commands to two "helmsmen" turning miniature steering wheels, and passed power settings by mechanical telegraph to "stokers" attending each engine. "Sailmakers" and "riggers" clambered over the interior of the aircraft checking its fragile structure for damage. A "sailing master" tried to keep track of the ship's position on a vestigial chart table. All these people stood up during their entire watches without a chair in sight, even in the strongest storms! "Ships of Aluminum -- Men of Iron!" This army of specialists was unneeded. The airplane community was able to consolidate all these control functions into the hands (and feet) of one comfortably seated pilot. Today, we insist on perpetuating the airplane model in a medium where no manual control is possible. The Shuttle's windshields, control sticks, and rudder pedals are as anachronistic as the ornate wooden steering wheels of the zeppelins.

Low Safety Factors -- The low lift/volume ratio of airships placed a premium on light weight in all components. The normal strength safety factors used in bridge or ship engineering were cut back to dangerously low levels by airship designers. This led to a number of crashes were airships simply broke apart when they encountered conditions not foreseen in strength calculations. NASA has followed this dismal tradition by using a safety factor of only 1.4 in most elements of the Shuttle. The CAIB discovered a case in which this had been arbitrarily reduced to an unbelievable 1.25, without any engineering analysis to justify the change!

Uncomfortable Safety Trade-Offs -- The use of hydrogen as the lifting gas in the early airships was the main source of danger and caused most of the fatalities in crashes. It is customary to regard the US Navy's adoption of helium as a great step forward in safety. But more detailed analysis suggests that it was not. A helium airship had to be about 20% larger for similar performance, and the extremely high cost of helium in that era required many risky operating procedures to avoid losing any of the precious gas. Like most proposed Shuttle escape systems, helium may have caused as many problems as it solved.

Low Flight Rate -- Due to their high unit cost, only 162 rigid airships were built. Furthermore, that small fleet spent a large fraction of its time floating in huge expensive hangars, waiting for enough good weather, helium or funding for the next flight. In 40 years of operation, a total of only 76,500 hours of flight time was accumulated (divided between 50 different designs). The lack of accumulated experience (in both crews and designers) contributed to the high rate of airship accidents. As late as 1934 the captain of USS Macon wrote: "Due account must be taken of the fact that the most experienced of us [airship officers] are novices compared with surface ship officers in terms of time in our respective elements... The Commanding Officer is constantly confronted with new problems of operation." Any Shuttle astronaut or engineer will certainly sympathize with him.

High Accident Rate -- Rigid airships suffered a non-combat crash every 1275 flying hours. Even though only about one-third of these crashes caused fatalities, they were a serious burden on the small lighter-than-air community. And the airship crash rate remained high right up to the end, while the mean time between fatal civil airplane crashes increased from a mere 100 hours around 1910 to 125,000 hours in 1940. An increasingly safety-conscious society was no longer willing to accept the inherent level of risk in lighter-than-air flight -- just like they now reject the risks involved in the Space Shuttle.

Inadequate Research Investment -- In some photos of the Hindenburg crash, one can see a DC-3 that was waiting to ferry the airship's passengers on to New York City. This image emphasizes the contrasting development history of the competing technologies: the airplane had evolved tremendously between 1903 and 1937, while the airship was still a creature of fabric and wire. After an initial decade of creativity, the Zeppelin Corporation became extremely conservative and opposed to technical innovation. During WWI, there was a short period during which the German government forced Zeppelin's management to adopt many advanced features from their arch-rivals the Schutte-Lanz company. But after the war, the Zeppelin firm was headed by Dr. Hugo Eckener, a former journalist who proved to be a formidable publicist and fund-raiser, but not a technical innovator. Similarly, we are still in 2003 using rocket technology developed in the 1950s.

The Publicity Spotlight -- When not restricted by military security, airships operated in a blaze of publicity and hype that seriously compromised their operations. The sight of these huge silver craft floating effortlessly in the air was as emotive as a rocket launch. Politicians at every level from Kaiser Wilhelm II down to Ohio county fair promoters demanded that the great ships show themselves to the masses at remote sites, on rigid schedules, without regard to weather or technical defects. And the airship managers, knowing that these politicians paid the bills, were happy to oblige them with risky "ballyhoo cruises" that frequently ended in disaster. The analogy with the idiotic politician-in-space, prince-in-space, and teacher-in-space programs that plague the Shuttle program is specific and painful.

Public Outcry -- The great size and expense of each airship, combined with their high public profile, insured that each accident was regarded as a major national tragedy. The heavy losses of trained crewmen aboard R-101, Akron, and Hindenburg were damaging enough to their respective programs. But it was the intense reaction in the news media and the general public to these losses that stopped further airship development. We have not quite reached this level yet in the Shuttle program -- but the statements of Shuttle critics are very reminiscent of the growing anti-airship clamor in the 1930s.

Fanatical Promoters -- The rigid airship was essentially created by a single wealthy German aristocrat, Count Ferdinand von Zeppelin. Many people had the idea, but only the Count had the wealth, political influence and sheer dogged persistence to get the thing started. When his own money was exhausted, he stooped to such non-aristocratic gimmicks as lotteries and public appeals to national pride to raise money for his experiments. The parallel with Wernher von Braun is almost spooky. Even the later period of airship operation produced many slick promoters like Eckener, Moffet, and Rosendahl who are similar to -- well, you can fill in your own favorite Space Cadets here.

There is, however, one big difference between the airships of the 1930s and the rocketships of the 2000s. Back then, the rapidly improving airplane existed as an alternative means of performing all the airship's missions. But today there is no analogous technology waiting in the wings to take over from rockets. Even if we scrapped the Shuttle, we would still be stuck with some kind of fragile, explosive-filled, expensive, overlarge rocket-powered vehicle that would fail on 1-2% of its flights. If we want to continue with manned space flight, we must continue to fly on the 21st-century equivalent of Count Zeppelin's gasbags. Until that elusive "space DC-3" comes along, space travel will be inherently expensive and dangerous. That is the most unpleasant truth of all.

Jeffrey F. Bell is Adjunct Professor of Planetology at the University of Hawai'i at Manoa. The opinions expressed in this article are his own, and do not represent the views of the University.

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