FeedsBringing zeppelins down to Earth: Q&A with an airship engineer
The discussion over airships is growing, promoted partly by new zeppelin tourist flights in Tokyo, Wolfgang von Zeppelin's (yes, THAT Zeppelin - grandson of the Count) staunch advocacy, and an effort to discover alternative modes of transportation. Even the Ron Paul kids are getting on board with airships. However, much of the discussion about airships is fueled by amateur speculation. In an effort to spark more helpful and realistic thought and discussion, I asked Ron Hochstetler, a lighter-than-air engineer, a few questions that have come up in many of my conversations about airships. I have just begun to touch the surface of the debate, so please add your own questions to the comments section.
For another question and answer session with Ron, be sure to check this article out.
First, a bit about Ron:
Mr. Ron Hochstetler has over 20 years experience in the operational analysis, and technical marketing of LTA vehicles. Ron began his LTA career in 1984 as a mechanic/assembler on the Piasecki Helistat program, which developed a hybrid airship/helicopter for heavy lift applications. In 1985 he joined Airship Industries, providing technical support on the US Naval Airship Program. He also flew as an airship flight test engineer, and supervised a commercial airship on tour. He joined Veda Inc., in 1990 to support the US Navy Airship Program office, and in 1998 joined CargoLifter as a Senior Project Analyst. For the past 7 years Ron has worked for Science Applications International Corporation in northern Virginia where he continues to develop technical concepts for manned and unmanned airships. Mr. Hochstetler has a Masters degree in Technology Management from the University of Maryland and a Bachelor of Science degree in Aviation Technology from Purdue University. Ron is the former Chairman of the FAA Airship Working Group, a former Chairman of the AIAA LTA Technical Committee, and a current member of the Airship Association Council.
And now, the questions!
MR| Weather was historically a problem for airships; is there a way around this, or are airships always going to be subject to storms, and will they be as dangerous as they historically have been? | |
| RH | Weather has been and continues to be perhaps the biggest operational challenge for all aircraft. Airships have weather limitations that are particular to them. The principal issues (in order of priority) are: headwinds, convective winds, temperature changes, and snow accretion, but by far the most serious weather phenomena for airships are the head winds. Most civil airplanes deal with inclement weather by flying above most of it, or in other words by avoiding it as much as possible. They have the advantage of rising vertically to much higher altitudes than is possible with airships, so the airships must move horizontally to make similar avoidance maneuvers. Traditionally the airship pilot and flight crew would study the weather maps and make their best guess as to how they would route their airship to avoid or minimize the impact of the strong head winds that can dramatically slow down the airship in flight. With modern weather data gathering systems and sophisticated weather prediction models it is only now possible to create “weather optimized” airship flight routes. Computers are far more capable when it comes to providing the airship pilot with a flight route tailored to fly away from head winds, but also be able to take full advantage of tail winds, all with the purpose of minimizing flight time, reducing fuel consumption, and maximizing airship operational safety. We are now; for the first time in airship history able to create these exquisitely designed fight routes that tell the airship pilot what the best heading and altitude is at any given moment, and when to change to a new heading and altitude. We are confident that this new modeling capability is an enabling, and even essential technology which will at long last give the airship the operational performance necessary to carry out reliable and predictable flights in the kinds of weather that historically were too dangerous to fly airships in. |
| MR | There are many proposed designs for modern airships, yet none of them are rigid - has the traditional hard-shelled zeppelin gone the way of the dodo, or is there a potential place for it in the future? |
| RH | Historically airship designers generally prefer to employ a non-rigid airship concept when possible because it tends to be easier and less expensive to build. The non-rigid airships however, have a size limit that’s based on the strength of the envelope fabric that holds the lifting gas. As the diameter of the non-rigid airship increases so too do the stresses on the fabric; until you reach a size where the best fabric available just can’t handle the loads. At that point the designer starts looking for ways to spread the stresses and loads by employing rigid structural members. The modern Zeppelin N 07 is a good example of this approach. It uses a conventional helium filled gas envelope but also has an internal rigid frame made of just three longitudinal composite fiber frames. As an airship goes up further in size the number of rigid components required to distribute the loads increases. At some point you reach a size where the classic, fully rigid airship design is required to handle the greater loads. With continuing advances in modern fabric development the airship size thresholds at which you must begin employing more rigid components has increased steadily. It’s now generally accepted that fabric technologies will soon permit non-rigid airships to be designed to sizes that equal or perhaps even exceed the size of some of the larger rigid airships. Research in rigid structural technology developments has likewise given us the ability to build fully rigid airships that would exceed the size of the 800 foot long Hindenburg.
The two biggest challenges to building large airships (whether rigid or non-rigid) are: scale and cost. As airships increase in size, their complexity and difficulty of construction also increase. A task that is simple on a small airship can become a Herculean engineering challenge just because everything has become so much bigger. As construction challenges increase, you also find the costs increasing. There is a place for the rigid airship but because of their great size, cost to construct and operate, they require a utilization that can be best accomplished by a very large airship. |
| MR | The large ground crew has historically been a problem for large airships, especially the massive zeppelins. Is that still true today? |
| RH | Ground handling remains the greatest operational challenge of fully buoyant airships, and the problem increases as the airship becomes bigger. When the airship slows to zero airspeed it begins to act more like a soap bubble, and is at the mercy of the wind. Large ground crews will never be employed as they were with past airships because the manpower is too expensive, unwieldy to coordinate, and not very effective. Modern airship ground handling techniques could benefit significantly from current computer controlled robotic technologies, but no one has yet adopted robotic systems to the ground handling issue. One technique to minimize this challenge is to keep the airship in flight as long as possible and only bring it down for occasional scheduled maintenance. Another effort to side step this ground handling difficulty is to design an airship that is slightly heavy when it lands. The “hybrid” airship obtains up to 80% of its lift from the helium gas, and the remainder from dynamic lift which is generated by flying forward through the air just as a conventional airplane does. This airship concept would enable a landed hybrid airship to sit on the ground as an airplane does, and would therefore be less susceptible to the wind blowing it around. The hybrid airship would also probably not require the kind of ground handing equipment that fully buoyant airships need. |
| MR | In general... what would a modern airship look like? What could it do? |
| RH | This is the fun part of the airship business because we have yet to see what a fully modern airship would look like. The most high tech airship at the moment is the Zeppelin N 07, and yet it does not employ all the engineering possibilities that could be incorporated into an advanced, modern airship. I like to say that the airship is the last unexploited air transportation system, and for this reason it offers young designers and engineers a creative adventure that has not existed in aviation since the 1930’s and 40’s. But to get back to your question, a modern airship would perform more like a ship in the sky than it would an aircraft. The first things you’d notice is that it would have stability, and it would have space, lots of space! Because airships fly slower than jets, more cabin space can be made available for passengers and cargo. In most transport aircraft you run out of payload volume long before you ever reach the payload weight limit of the aircraft, but a large airship would offer cavernous amounts of deck space in addition to a payload lift that could range from 25 tons up to several hundred tons. The other benefit of a large modern airship would be its near independence of operation. You can’t take a jet airplane trip unless there are two big and expensive airports to support your flight. A large airship (whether fully buoyant or hybrid) would need so little equipment on the ground for passenger or payload transfers that you could actually consider creating “just-in-time” airfields for airship operations almost anywhere (up to about 6,000 to 8,000 ft. above sea level). This quality, in addition to their very low fuel consumption makes modern airships quite Earth friendly and an attractive transport for use in developing countries that can’t afford highways, railroads, or large airports. Such an airship would turn the world into a giant “archipelago” of communities that could be interconnected, independent of the conventional transportation infrastructures. For my final comments I want to challenge any young designers or engineers to consider the airship as the last aviation adventure where almost anyone can make a significant impact and advancement on the technology. Only the airship offers the last, best chance to create an air transportation system that is not a substantial contributor to Global Warming. It is also the only one that is not a hostage to the politics and economic control of those who would influence societies through the control of essential ground transport infrastructures. The large, modern transport airship offers the best chance for realizing the ambitions of aviations early pioneers who dreamed of using air travel to connect all the peoples of the world. I think it’s the airship that can finally turn that vision into a reality. |
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