Polymath A (mostly) technical weblog for Archivale.com

November 8, 2013

Oblique Convergence – the Two Roots of Modern Unmanned Aircraft

Filed under: Aeronautics,Engineering,Propulsion — piolenc @ 5:40 am

Unlike most high-tech industries, which start with a single core idea and a small coterie of self-educated practitioners before branching out into diverse applications, ours has at least two quite distinct roots  and two very different seed groups. One root is the traditional target drone – reconnaissance drone – armed drone – UAV progression based on aeronautical experts qualified in aerodynamics, structures, propulsion and control systems, starting with primitive analog automation and progressing to digital systems of ever-growing sophistication. It traces its origin to the experiments of Sperry and others as early as the 1920s.

The other root of modern UAVs is embodied in multicopters – ugly, crude, primitive-looking things designed mostly by electronics hobbyists with only the vaguest connection to aeronautics.

The former group build competent, elegant air vehicles – fixed-wing or rotorcraft – and then try to endow them with the control systems that they need to perform their missions without a human being on board. For them, the object is the aircraft and its mission; the control hardware and software are extensions of the aircraft that allow it some autonomy.

The latter group are hardware and software hackers (in the original sense of the word – meaning an expert, not a criminal) who are looking for the cheapest, simplest platform that can pick up their micro-controller board and its code and fly it around. For them, the object is the code, and the ‘copter is merely an extension of the hardware platform on which that code runs – basically a peripheral that allows them to have fun with computers outdoors and burn off all those Twinkies and potato chips.

Neither group has much regard for the other, or much interest in the other’s preoccupations, but a funny thing is happening: as the traditional UAVs tend toward cheapness and ubiquity, the digital eggbeaters of the multicopter hobbyists are becoming more capable: more payload, longer endurance, and very advanced software (because that’s their strength, don’t you know).

Pretty soon the two groups will either be collaborating on or competing for missions that are within the reach of both of them, though they’ll be approaching those tasks from very different perspectives.

What missions, for instance? Well, deliveries for one. We’ve already seen the pizza delivery demo, but I’m thinking of more sensitive deliveries – the kind you probably wouldn’t entrust to a high-school student on a motorbike under any circumstances. The kind where you lose a lot more than twenty dollars plus tips if something goes wrong.

Here’s one:

We think of the mining industry as being concentrated into huge, self-contained operations, from which a very crude, low-value raw material – the ore – is sent to be refined remotely into a valuable and compact commodity. But the reality can be different. Highly valuable resources – we might as well say gold or diamonds because that’s what we’re talking about – often occur, not in a concentrated vein, but in pockets spread over a large area. We speak of gold or diamond fields. Another characteristic of these resources is that they don’t need refining – at least not in the same sense as, say, copper ore – only extraction from a matrix. Gold occurs as the pure metal rather than as an oxide or sulfide like some other metals, and diamond is…diamond. So these resources are essentially finished products at the mining site, and are already very valuable and, because of their portability, very vulnerable.

In a typical gold field operation, small quantities are collected from various small mining sites (in the case of panned gold, there could be hundreds of pans or small dredges strung out along a river) into a more or less central location within the gold field, then transported to a permanent installation for assay, refining to .999 purity, and casting into bullion or minting into coins. On the way there, however, it is subject to theft and to hijacking.

Here’s where UAVs come in. Autonomous UAVs have the capability of taking off from a secure base, flying to a remote location under GPS guidance, and landing within a few meters of their target. There, a payload can be loaded aboard, and the machine refueled or recharged for the return journey. It then takes off and returns to base with the payload. Autonomy means that it can’t be electronically hijacked by interference with the communication link with the ground. Typically, there would be no such thing, which also carries an economic benefit, namely elimination of the ground station and its operators. Arriving at its base, the craft lands inside the secure perimeter and is safely unloaded, then serviced for the next pickup.

Obviously, we are talking about vertical takeoff and landing here. The VTOL field has many different types of craft within it, but helicopters have the most attractive characteristics for this mission because their low-disc-loading rotors allow a given load to be lifted at the lowest cost. Speed is not an issue – only security – so a helicopter’s relatively modest top speed won’t be a problem.

The avoided loss in securely delivering one typical gold shipment – twenty kilos – is nearly a million of the green pieces of paper we laughingly call “dollars.” On the other hand, the direct operating cost of shipping by autonomous UAV, with no pilot or ground crew salaries to pay, comes down to amortization of the initial cost of the vehicle and its support equipment. It follows that a significant investment in this technology can be justified. Imagining a first cost of one million dollars, that investment is almost fully recovered in one avoided hijacking. Actually, payback is quicker because conventional shipping methods involve substantial personnel costs, mostly connected with guarding the shipment, even if nothing at all goes wrong.

Converging on this opportunity are two very different technologies. The drone crowd will offer an autonomous helicopter – essentially a scaled-down version of a manned helicopter design equipped with a combustion engine and a simplified version of conventional flight-control hardware like the rotor head. From the other side will come proposals for a multicopter that will be a scaled-up version of the ones we see buzzing around on YouTube, equipped with one electric motor per rotor and a battery pack.

There will already be some technological convergence: both machines will likely be controlled by programmable micro-controller boards of purely civil, hobbyist origin running private-origin code. This will be for reasons of cost, but also because the control system that would normally have equipped the “drone” machine for, say, a military mission are not legally exportable from their countries of origin. We might see this as the drone people learning from the multicopter hobbyists.

In the present state of battery development, however, it will probably be necessary for the multicopter crowd to adopt technology from the drones, namely combustion engines. This is because storable liquid fuels have much higher specific energy storage capacity than the very best batteries. The easiest way to incorporate a combustion engine into a multicopter will be to have it drive an alternator to recharge the on-board battery through a rectifier/filter in the usual way. The battery would then drive the motors as if the combustion engine weren’t there. In essence, the multicopter would take its recharging station with it, and the payload penalty that carries with it would be partly compensated by having a much lighter battery. One operational advantage of this arrangement is that the machine can be refueled at the remote site and be instantly ready for flight. Hooking it up to a generator to gradually recharge the internal battery won’t be needed.

What else can the multicopters learn from the drone people? Well, a lot. Multicopters are pretty straightforward to control when hovering or moving slowly, but they run into trouble when trying to build up a significant cruise speed. This is the result of the trailing rotors operating in the downwash of the ones ahead. In a conventional tandem-rotor helicopter, this is compensated by increasing the collective pitch of the rear rotor, but no such option exists in a multicopter – the trailing rotors have to turn faster. This works up to a point, where the limit of speed control is reached and the multicopter pitches up abruptly, braking its forward motion. Judging from what’s on YouTube, the speed limit for multicopters looks to be about 70 km/h at present. This may actually be adequate for the mission under consideration, but some means needs to be found for improving it without sacrificing the essential mechanical simplicity of the multicopter. Ideally, that means should not involve additional control channels. That solution, whatever it may be, will likely come from people with conventional helicopter experience.

Another rotor-related problem is the vibration that occurs in a rigid rotor (propeller) in crossflow. You can hear this in the fluttery hum that multis make when moving in translation. This represents a loss of efficiency, and in the long run might lead to unpredictable rotor failure. Again, the conventional aero backgrounds of the drone people will help, with a bolt-on solution in the form of a teetering, flapping or even feathering rotor being the most likely result.

Net result – a much upgraded multicopter and/or a more economical, exportable helicopter drone…and happy miners.

November 17, 2012

Free Flight: Personal Leased Air Transportation

Filed under: Aeronautics,Personal — piolenc @ 7:33 am

“The question isn’t who is going to let me; it’s who is going to stop me.” – Ayn Rand

In this day of no-fly (and soon presumably no-train, no-ferry, no-bus, etc.) lists the question of unimpeded personal long-distance transportation needs to be taken a bit more seriously than it was in a recent Feedback Friday (http://www.DollarVigilante.com), which read in part: “Sadly, you have to have your own sailboat, motorboat or airplane in order to get outside of all this…” implying that these were hopeless aspirations for most of us. Taking it strictly at face value as meaning owning a seagoing yacht or an aircraft with decent cross-country performance, it’s probably true. But the very technological developments that make possible nude scanners are also making possible the physical liberation of travelers on a very large scale.

Private (i.e. non-commercial) aircraft and boats get you out of the nude scan/grope line, but not completely out of the clutches of government. Where the bureau-rats get you as a boat owner is at the shoreline – forbidding anchorage in the open bay and forcing boat owners to pay outrageous slip fees and submit to ridiculous registration procedures, stopping boats for “safety” checks and to look for drugs, etc. For aircraft it’s the airfield for “papers” and outrageous hangar fees, not to mention the ridiculous cost of the vehicle itself (due to government certification requirements) and of government-approved training to obtain a government-issued license to fly it.

But aircraft have that vital, vertical third degree of freedom that gives them the potential to eliminate contact with officialdom, if only they can get away from using government-designated landing grounds. Very short takeoff makes that possible in many places*; vertical takeoff gives an almost infinite supply of off-airport landing areas. Specific aircraft to fulfill this need may come up in a later post, but I’d like to discuss the problem of Free Flight in general terms first.

Back in the 1930s and 40s it was generally assumed that airplanes (or aircraft of some kind) would eventually become as common as the family car or “flivver,” and serious effort was put into making the perfect “air flivver” for Everyman. Much of that effort, ironically, was sponsored by government, with many NACA reports coming out during that period concentrating on shortening landing and takeoff runs, making airplanes that were stall- and spin-proof, improving pilot vision, improving fuel consumption, reducing noise and so on. Much effort also went into seaplanes, flying boats and amphibians during this period, mostly for military purposes but also to the benefit of “bush” flyers.

The emphasis in all this was on safety, but every bit of progress also held the promise of improved access to air transportation. Low stall speeds and improved low-speed maneuverability make short, unpaved fields usable. Reduced noise makes it possible to operate near homes without causing a riot. Amphibious operation makes every sheltered body of water over a certain size into a potential airstrip, and every boat ramp a terminal.

The one factor that prevented the flowering of Everyman’s Airplane was the need for skill. Make a ‘plane as safe as you like, it still takes much more skill and discipline to operate one than a car, and the penalty for error tends to be greater, too. Forgetting to check your automobile’s fuel level before departure leads to a humiliating roadside call to the Auto Club; forgetting it in your airplane can result in “catastrophic terrain intersection” in the language of modern accident analysts. These constraints cannot be blamed on the State; they are imposed by Nature. Flying an airplane from water requires additional skill and judgment. As for the helicopter, a priori the ideal “air flivver” because of its ability to take off and land vertically, even more skill is needed to fly it, to the point that not every candidate for a helicopter license is able to achieve the necessary level of skill despite the expensive instruction.

The means of overriding that obstacle didn’t exist in the 1940s, but it is ubiquitous and cheap in our day. I’m referring to the digital computer, of course. It is true that much effort has gone into analog autopilots over the years, and many airplanes are equipped with them, but they are essentially cruise controls – they allow the pilot to relax a bit in the middle portion of a long cross-country journey. The most difficult and dangerous phases of flight, namely takeoff and landing, are still the pilot’s full responsibility, and he still has to perform every detail task related to communication, information gathering and navigation, using primitive methods and in the cramped, noisy and often drafty confines of a cockpit.

More recently, digital computation and control have entered the cockpit, with the benefits that we all know so well in other phases of life, namely programmability and expandability. This has led to a vast reduction in pilot workload in commercial airplanes, because the complexity of the tasks assumed by the flight controller has enormously increased, aided by much more extensive sensor input and its ability to directly control the servomechanisms that already exist to amplify the pilot’s control effort. Certain commercial airplanes now can literally land themselves, with the pilot standing by to take over if something goes wrong with the navigation aids or the controls themselves, or some obstacle appears on the runway.

The homebuilt,  experimental or sport aircraft movement has paid attention to these developments and is already making extensive use of digital electronics in navigation and trip planning, but applying electronics to direct control of the airplane is more difficult because most homebuilt and small factory-built airplanes still have direct manual operation of the control surfaces via mechanical linkages, so all the actuators have to be retrofitted and plumbed into the airplane’s existing systems. Besides the expense, there is the question of motivation: the sport airplane crowd probably don’t especially want an airplane that flies itself. Their joy comes in exercising and improving their piloting skills, not merely in getting from point A to point B, and most sport flying originates and ends at the same airfield in any case.

Factory-built airplanes, which in a free market would quickly incorporate every technical advance making flying easier, instead lag decades behind experimental aviation. This is entirely due to the State, which requires every component of a certified aircraft, down to the last rivet, to be government-certified for use in aircraft. This makes the cost of aviation electronics astronomical, further shrinking a market that was small to begin with, and ensuring that mainstream manufacturers will never invest the development costs to bring any truly modern gear to the civil market. Barring a revolution, then, the solution to our problem will not come from the “spamcan” vendors.

Accessible personal air transportation will have to originate outside the usual civil aviation channels, even though it will draw on aviation knowledge and technology. The controls component will originate almost entirely outside of commercial, general and sport aviation because its purpose will be to take the skill out of flying and essentially make the operator of a personal cross-country aircraft a passenger who decides the destination and may make some routing decisions (“stay away from Milwaukee,” “pass Mt. Shasta to the south”), but takes no part in direct control of the aircraft’s flight path. Interestingly, this kind of autonomous control is currently in existence for one application only – unmanned aircraft, mostly used by the military. Digital autonomous and semi-autonomous controls exist for drones, including rotary-wing drones, which can be ordered to follow a certain flight path, the remote operator intervening only to order deviations and to engage targets (and even then he only designates targets, and does not have to directly control weapons). The same controls can work equally well – better, in fact, because they don’t depend on communication links – with the operator on board.

A typical trip scenario, freedom fashion:

When Mr. Freeman wants to make a business trip to a distant city, he orders an aircraft, which lands at the appointed time on his back lawn or any convenient rendezvous such as a nearby park, rooftop or sports field. He hops aboard, identifies himself to the aircraft’s computer and makes himself comfortable. The aircraft weighs itself (by reading sensors in the landing gear struts) and informs him that, although he and his luggage are within the weight limit for the trip, he will need to stow part of his luggage forward as the aircraft is currently tail-heavy. Mr. Freeman moves one of his bags to the forward bin, the computer confirms that the machine is now within its center-of-gravity range, and the aircraft takes off without further delay. During the flight, he enjoys the view, which is panoramic because the flight altitude is low to keep away from government-controlled aviation corridors. If he gets bored with the scenery, he watches a movie on the built-in displays, catches up on his electronic correspondence using the aircraft’s built-in networking facilities or reviews the presentation he will make at his destination. If the flight is too long for the aircraft’s fuel endurance, it will land itself at a suitable refueling stop – probably the back lot of a truck stop or fuel dépôt, as the aircraft will probably be burning diesel fuel or heating oil. Depending on the level of service contracted for, Mr. Freeman will either have to pump the fuel himself or an attendant will do it for him. Likewise, contractual arrangements will determine whether Mr. Freeman uses his own funds directly to buy the fuel or the fuel is paid for by the aircraft leasing service and included in its charge to Mr. Freeman. Upon arrival at destination, he will either be deposited right at his hotel, if the hotel has a pad and is willing to accommodate non-government-sanctioned transports, or at a suburban taxi stand where a taxicab contracted for by the leasing service is waiting to take him and his luggage to his final destination. If the aircraft is amphibious, landing on a convenient river or bay and using a dock or boat ramp might also be an option.

It is clear from the scenario that a very different ownership structure from that currently existing in general aviation is assumed there. One of the many reasons that private aviation is currently so expensive per mile traveled is the very low rate of utilization of the aircraft – a fewscore hours a year, usually. All the aircraft’s overhead (much of it incurred by compliance with government regulations) and debt service gets charged to those very few flying hours, and the arithmetic result does indeed make it look like a rich man’s indulgence. Of course there are rental aircraft fleets in existence today, but they consist of overpriced “certificated” aircraft which are required to be maintained by overpaid licensed Airframe & Powerplant mechanics and are only eligible for rental by government-licensed pilots, so the savings expected from our hypothetical unregulated rental fleet, serving the general public, are not realized. All that changes if the aircraft is part of an autonomous rental fleet that is rented out to multiple non-flight-qualified customers on a per-trip basis over the course of the year, spending only enough time in hangar for regular maintenance.

Where would these unlicensed aircraft come from? Not from Cessna, Piper or Beechcraft  – not for the foreseeable future, anyway – because those General Aviation manufacturers are under the thumb of government and would likely be punished if they built aircraft intended for use off the plantation. At first, production would likely be a cottage industry, with small producers specializing in various hardware components, specialized software firms providing flight control programs and data files such as digital terrain maps. Assembly and checkout would likely be carried out by the customer – the leasing service – or by a specialized assembly firm working directly under their supervision.

The rental scenario and the decentralized production scheme both imply comprehensive standardization. This tends to raise strong doubts in many freedom-lovers, who associate standardization with coercion and centralized authority. It is worth pointing out, however, that voluntary standards existed long before government stuck its oar in the water, and that even today the most effective and widely followed standards are still voluntary ones – think Internet Protocol, WiFi and USB connectors – adopted because it is in the best interests of the adopting parties to use them. Today, there are many de facto standards in effect within the homebuilt aircraft movement, administered (if at all) by membership-based organizations operating without government sanction. This is the closest thing to a free market that exists in aviation – homebuilders who want proven hardware go with the standard offerings, leaving the risk-takers and pioneers free to think and work outside the box.

Initially, somebody is going to have to take a financial risk, but it need not be a very big one – certainly not like the risk exposure of launching a new “spamcan” or factory-built personal airplane. Imprimis, there will be no up-front “compliance” costs which are a major component of cost of any new certified aircraft venture, and a disproportionate component of the cost of bringing a small aircraft to market. Secundus, the infrastructure required for promotion and administration already exists. Tertius, production tooling will likely be paid for by the individual manufacturing subcontractors, each of whom will be taking on only a small part of the project and therefore risking relatively little capital.

The biggest obstacle is, sadly but predictably, the human factor. To be commercially successful, this business must be marketable to people who have not adopted the freedom philosophy. To be a technical and production success, people who don’t necessarily share our principles have to be persuaded to participate, or people who do share our principles have to be persuaded to acquire the necessary skills. This is so because, sad to say, most people in aviation, including the sport aviation/homebuilt phase of it, are conformists when it comes to obeying government regulations, which they associate with safety and order. They are of course far from being the only ones to make this error, but it is inconvenient that a skilled workforce that would be most helpful in this project holds mostly negative views regarding the actual practice of freedom. We may have to build a skilled production and operating force entirely outside current aviation circles. We will have to market the service to travelers purely on the basis of cost and quality, and let the lesson of liberty teach itself by experience.

Fortunately, this should not be too hard. Convenience is hard to beat: pickup à domicile or nearby at a time of the traveler’s choosing, and delivery to destination, or to within a cab ride of the destination. The latter is a pretty strong selling point if the destination is other than a major hub, because the cost and the time in transit both rise drastically in that case, when flying commercial. In fact there are no direct commercial flights to smaller cities and towns; the traveler first flies to the nearest hub, then changes, not just flights but also airlines and terminals usually, retrieving and re-checking his luggage in the process, then flies on to his final destination, often after cooling his heels in a major airport, with his baggage, for hours. If the enhanced convenience, privacy and comfort of a free flight service can be accomplished at or below the price of a commercial ticket, it should be an easy sell. Even if sanity returns to commercial travel and the TSA goons are forced to seek honest work, the service should survive for decentralized travel and for feeder service to major airports. In our hypothetical trip, for example, Mr. Freeman’s autonomous air taxi ride might be the first leg of an international journey.

“Bootstrapping” is an option. The first increment of the business developed could be a franchised chain of local pinpoint aerial parcel-delivery services – the aircraft smaller, short-ranged and not man-rated. Most of the software – particularly close-quarters piloting and dispatch algorithms – developed for this phase will be applicable to later phases. This would be followed by local air taxi and airport feeder service in areas of high traffic congestion, infrastructure bottlenecks or both. Both would form the basis for development of still longer-range vehicles and for building a network of service depots across the country.

* A late and much lamented, very eccentric friend liked to go “camping” with his nimble and somewhat modified Aeronca Champ, a high-wing taildragger in the proud tradition of the Piper Cub, but larger. He would fly out into the countryside at low altitude, pick out a pleasant-looking spot – a country road, a meadow, a ridgetop – and land there. He would then conceal his Champ, which was painted a dull grey (or perhaps that was just the color it had turned over the years), and spend the night sheltering under the wing, eating whatever he’d brought with him and reading by flashlight. (His rudimentary airplane lacked an electrical system, and I had helped him rig up an external battery for his handheld VHF radio, which he would take home for recharging between flights.) If he was feeling too lazy to pack a picnic he would seek out a nice spot close to a truck stop on the Interstate and thus gain access to the truck stop’s café and rest rooms. He loved to point out that he could find clean air, tall grass, peace and quiet a short walk from a freeway that was at times jammed bumper-to-bumper with vehicles. If he felt the need for fuel he would buy some at the truck stop, having brought along a jerrycan for the purpose. When he wanted to move on he would push his machine out of its hiding place, swing the propeller of its sixty-five-horsepower engine to get it started, leap in and take off before anybody was the wiser. His arrival would not have been noticed because he would glide in with the engine barely ticking over, so his departure would come as a complete surprise to whoever was in the neighborhood. This is not a solution for Everyman – Ed could get away with it because of his intimate familiarity with his very low wing loading, balloon-tired airplane and because of the flying skill he had accumulated over decades – but it does point up the possibility of operating a nominally very noisy aircraft in places that are generally thought to be too densely populated for such an activity.

August 6, 2010

The Helium Question

Filed under: Aeronautics,Engineering,Lighter than Air,Materials — piolenc @ 11:21 pm

[This piece first appeared in the Fall/Winter 2006 issue of Aerostation magazine]

LTA: 2006 and the Helium Question

The year 2006 was much the same as any other recent year, at least as far as lighter-than-air flight is concerned. Hopes were raised, then dashed. Projects were mooted, then cancelled. Brave talk was uttered, then swallowed.

If Ought Six is remembered for anything, perhaps it will be that the first visible cracks appeared in the ever-rickety edifice of helium supply. For the first time that I can recall, some users of helium were told that they could not have any at any price, due to the fact that one of the world’s few helium extraction plants was undergoing refurbishment. Presumably extraction has since resumed—there are no panic-stricken “Brother, can you spare some gas?” posts on the LTA-related lists—but this little hiccup is a harbinger of things to come.

Those of you who have followed my rants over the years may want to skip the rest of this piece, but some points deserve to be reviewed. As commodities go, helium is extremely unusual—perhaps unique. It is a by-product of the extraction of another commodity—natural gas—whose unit value is much lower, but whose aggregate value is orders of magnitude greater. This means that the usual assumptions about supply and demand do not apply.

To make it clear why this is so, imagine a commodity—say, a precious metal—that exists in a concentration of a fraction of a percent in a matrix that has no market value. If the market value of the metal justifies it, somebody will extract the tiny metal moiety from the huge mass of matrix, refine and market the metal and dispose of the now completely valueless matrix. The key fact is that, in this hypothetical but typical case, the extraction is driven solely by the market for the metal. If the market value of the metal drops below the cost of bringing it to market, extraction ceases and the metal remains in the ground, in its matrix, waiting for changing conditions to again make it profitable to exploit it.
Contrast this with what will happen if there is a significant increase in demand for helium. Helium, as we know, exists as a tiny fraction of natural gas; some deposits contain more helium than others, and gas from some of those favored deposits passes through a helium-extraction plant on its way to market. The helium in natural gas that is produced without extracting the helium is gone forever, wasted.

Now suppose that there is an increase in demand for helium. Once stored helium stock is exhausted, the only way to meet the greater helium demand is to increase the production of natural gas. This may be done, up to the point that storage capacity for natural gas awaiting delivery to consumers is completely used up. At that point, helium production is capped at a rate proportional to the current demand for natural gas, irrespective of demand for helium. Nobody is going to flare off natural gas to accommodate helium users!

Now the operation of a free market, when production of a commodity is fixed and demand for it increasing, is to raise prices until demand drops to match the supply. This gives a bidding advantage to users who are well-funded and use relatively small quantities of helium. LTA doesn’t match that description, and never will. But there’s worse.

Another effect of a free market is that rising prices of a commodity encourage capital to move into production of that commodity, leading to increased capacity, which in turn tends to put the brakes on price increases. Can we expect this to happen with helium? One can imagine that, with helium prices skyrocketing, producers of natural gas from fields less favored by Nature than those now being exploited might install helium extraction plants at their fields, thus intercepting streams of helium now going up the stack. And then again, maybe not. Helium extraction is capital-intensive—essentially, it requires that all gases except helium be liquefied, leaving only helium in gaseous form. Depending on the projected exhaustion of the field, the helium concentration in the gas and their estimate of the persistence of increased demand, the field’s exploiters may or may not feel that they can expect an adequate return on their investment in new helium plant. Even assuming that the answer is always affirmative, there is a definite physical limit to this capacity increase, which is imposed by the rate of production of natural gas. What is more, each increment of production will be smaller than the last and cost more per unit of capacity, as poorer fields are added to the helium production stream.

The best scenario that we can expect, then, in the event of a true rebirth of helium-based LTA, is a steady rise in price, possibly restrained (but not cancelled) by capacity increases. It is a safe bet, however, that any major increase in helium demand will run up against a hard capacity limit, whether imposed by the reluctance of field exploiters to install expensive helium extraction or by the finite and tiny concentration of helium present in the natural gas stream.
When such an absolute limit is reached, modern governments show a deep reluctance to let market forces operate. Instead, rationing and price controls are imposed and favored users are given priority for supply. In the USA, at least, there is no doubt of LTA’s position in the hierarchy of government favor: near bottom, perhaps just one step above party balloons, perhaps even one step below (what would a political campaign be without balloons, eh?).

In the long run, the Earth’s supply of helium will be exhausted when we run out of natural gas, regardless of the level of demand for helium. Helium is the end product of a long chain of radioactive decay, and for practical purposes “they ain’t makin’ any more of it.”

Of course, I’ve been oversimplifying, by assuming that a revival of large-scale helium LTA would occur in the first place. In fact, no prudent investor would invest in commercial helium-lift LTA without considering the prospects for gas supply, and with the certainty of price increases and the uncertainty of future supply at any price, he will put his money elsewhere.

The plain fact is that helium is already too expensive. Its 6% gross lift penalty compared to hydrogen comes directly out of useful lift, imposing a net penalty around 20% depending on payload ratio. Its cost constrains airship operations by limiting operating altitude or fullness (hence lift) to avoid valving gas and by forcing operators to operate at very low purity to delay “shooting” gas as long as possible. Both constraints further reduce the economic viability of an already marginal transport medium.

If large-scale LTA is to survive, there will have to be a transition to hydrogen as the lifting gas. The only question that is open is: when? If LTA is ever to be used for transport of goods or people, that revival will have to be based on hydrogen lift. And it must be soon.

The time to prepare the transition is now, while there are people still living who have handled hydrogen in an LTA context, and who can instruct others. Hydrogen is more dangerous than helium, but there is no alternative. There are obstacles to be overcome in using it, and the sooner we start overcoming them the sooner we will have viable commercial LTA. The principal obstacles are:

• Lack of trained personnel.  Solution: train some.

• Lack of insurance cover.  Solution: insurance companies will ensure anything for which they have reliable actuarial statistics. Only experience can produce those statistics. Until they are available, operators will have to self-insure. It has been done before, and it can be done again.

• Government regulations and statutes.  Solution: a stroke of a pen.

Hindenburg Syndrome.  Solution: education and exposure.

Priced out of the market, or forced out. Those are the only possible fates of LTA if we persist in considering only helium as a lifting gas. It is, in the current jargon, unsustainable.


February 13, 2010

Book Review: Leichter als Luft

Filed under: Aeronautics,Engineering,Lighter than Air,Propulsion,Structures — piolenc @ 5:37 pm

Leichter als Luft

Transport- und Traegersysteme
Ballone, Luftschiffe, Plattformen

by Juergen K. Bock and Berthold Knauer

reviewed for Aerostation by F. Marc de Piolenc

Hildburghausen: Verlag Frankenschwelle KG, 2003; ISBN 3-86180-139-6, price: 39.80 Euros. 21.5 x 24 cm, 504 pages, single color, many line illustrations and halftone photographs, technical term index, symbol table, figure credits, catalog of LTA transport and lifting systems.

Summary of Contents

1. General fundamentals of lighter-than-air transport and lifting systems
2. Physical fundamentals
3. Design of airships and balloons
4. Reference information for construction
5. LTA structural mechanics
6. Flight guidance
7. Ground installations
8. Economic indicators
9. Prospects


A. Time chart
B. Selective type tables of operating lighter than air flight systems
C. Development concepts of recent decades
D. Systems under development or under test
E. Author index
F. Table of abbreviations
G. Symbol table
H. Illustration credits
I. List of technical terms
J. Brief [author] biographies

In LTA, which has seen only two book-length general works appear since Burgess’ Airship Design (1927), comparisons are inevitable despite a language barrier. It is therefore quite pleasing to note that the authors of this book have consciously set themselves a task that complements the work embodied in Khoury and Gillett’s Airship Technology1. While Khoury’s work is a review of the current state of the art, the present book provides

“…a scientific, technical and economic basis for a methodical, consistent procedure in developing new lighter than air flight systems as well as a catalog and appraisal of prior solutions and achievements.”

as stated in the preface by Dr.-Ing Joachim Szodruch of the DGLR. This is amplified in the authors’ Foreword:

“The observations contained herein are future-oriented and encompass without euphoria the current state of science and technology.”

This is in contrast to Khoury and Gillett’s introduction to Airship Technology, which reads in part:

“This book is intended as a technical guide to those interested in designing, building and flying the airship of today.”

The body of the book is completely consistent with its stated purpose, looking always toward the future and emphasizing how things should be done rather than how they have been done. Where examples of actual hardware and operations are needed, they are drawn from the most recent available, and meticulously documented.

Considering the authors’ long association with the LTA Technical Branch of the DGLR, it is not surprising to find that much of the material, and many of the collaborating authors listed in the Foreword, are drawn from the many Airship Colloquia held by that Branch over the years. Yet the style is seamless; there is nothing to suggest to this admittedly non-native reader where one contribution ends and another begins; style is consistent from paragraph to paragraph, and across chapter boundaries. What is more, the authors seem to have made a conscious effort to make the text accessible to non-Germans by keeping sentence structure simple and straightforward. The three-column-inch sentences, gravid with nested subordinate clauses, so beloved of the Frankfurter Allgemeine Zeitung, for example, are not to be found here, much to this reviewer’s relief.

It is compulsory to say something about the thoroughness of the book’s coverage. It is, however, difficult to formulate a “completeness” criterion for LTA, which is now more than ever an open-ended field, in which-as the authors correctly point out-the possible types are still far from exhausted, despite the antiquity of aerostatic flight. It is to the book’s credit that its presentation, too, is open-ended; that is, the authors have avoided presenting the usual narrow typology of LTA craft and their almost equally narrow applications. Instead, and in keeping with modern practice, they take a systems approach to LTA, situating it within the field of aeronautics and providing the tools that the reader needs to translate his own requirements into appropriate technology.

The only omission that might be considered significant concerns tethered aerostats: the authors appear to have neglected both tethered-body dynamics and cable dynamics in their technical and mathematical treatments. Tethered balloons as a type are mentioned, but that seems to be all the coverage that they get. Admittedly, long-tether applications have poor prospects because of potential operational and safety problems, but short-tether dynamics have caused problems in some applications that are relevant, including balloon logging, so coverage of that end of the scale would have been welcome. Tethers also play a role in some existing and proposed stratospheric balloon systems, including the exotic NASA Trajectory Control System or TCS.

This, however, is the only flaw in an otherwise comprehensive LTA design/analysis toolkit.

One especially notable and praiseworthy inclusion is subchapter 1.4 regarding regulation and certification. This topic, though a concomitant of any aeronautical project, is one that most techically oriented authors would prefer to avoid or to give only summary treatment, but Bock and Knauer dive into it fearlessly, setting forth in considerable detail, and with the help of flowcharts, German, Dutch, British and American certification categories and procedures, with reference to the governing documents. Not surprisingly, there is more detail about the German process, with which both authors have considerable experience. They also review the history and evolution of the European Joint Airworthiness Regulations (JAR), which are keyed to—-and sometimes based on—-corresponding Parts of the US Federal Aeronautical Regulations (FAR).

They do not flinch even from discussing certification costs and fees. Although they admit that the general policy of regulatory authorities is to require payments to government from the applicant that offset the costs incurred in administering and examining a certification application, they conclude that, compared with the cost of development of an airship, the regulatory fees charged are of only minor importance. It is not clear whether they consider here the costs incurred by idling the works while some bureaucrat makes up his mind! Perhaps it hasn’t happened to them…

Typography, binding and book design

The basic layout is in two columns, with generous leading and gutters, making the somewhat smaller than usual typeface easy to follow and to read. Equations are set in a slightly larger, bolder font and occupy the full width of the page, avoiding a common legibility problem with two-column layouts. There are no drop-outs to be found anywhere. The eggshell-white paper is thin enough to keep the book’s 500-plus pages within a thickness of less than an inch (2.5 cm), yet the paper is completely opaque, without bleedthrough and with perfect reproduction of fine-screen halftones. A color section is mentioned in the table of contents, but all pages in the review copy are single-color. The cover is paper, rather than cloth covered, printed front, spine and back in white on a dark blue background (reproduced in reverse for this review). This type of cover is less durable than the traditional cloth, but is in widespread use for textbooks and technical works despite this.

Second (English) Edition

Work is now in progress on a second edition, which will be published in English by Atlantis Productions. Note that this will not simply be a translation of the first, German edition but a new work, composed ab initio and including whatever revisions might seem appropriate considering response to the first edition. Both of the authors have a very strong command of English, so there is no reason to fear the damage that some excellent German technical works have suffered at the hands of translators (Eck’s treatise on Fans comes to mind).

A “must have” in either language.

1 While a more thorough and detailed comparison of the two books would have been desirable, it is unfortunately not possible, as Aerostation never received a review copy of Airship Technology. Such comparisons as can be made here are based on brief access to that book during a consulting stint.

This review originally appeared in Aerostation, Volume 27, No. 3, Fall 2004

January 15, 2010

Research Resources: Lighter Than (LTA) Air Flight

Return to ABAC Page

LTA Research Resources

compiled by F. Marc de Piolenc

To suggest resources not listed here, or to correct errors, please leave a comment below.

Libraries & Special Collections
Name/Collection Address/Telephone Description
Embry-Riddle University Library Daytona Beach, FL 32014
(904) 239-6931
Northrop University Library—
Pacific Aeronautical Collection
5800 W. Arbor Vitae St.
Los Angeles, CA 90045
(213) 641-3470
Documentation on West Coast aeronautical activity, including LTA. Photographs.
National Air and Space Museum Library Smithsonian Institution-A157203
Washington, DC 20560
In addition to its collection of books and documents, NASM also has an extensive graphic archive, much of it digitized.
University of Akron
Arnstein Collection
The University of Akron
University Libraries
Polsky Building
225 South Main Street, Room LL10
Akron, OH 44325-1702
Tel: (330) 972-7670
Fax: (330) 972-6170
email: jvmiller@uakron.edu
Papers of the late Dr. Karl Arnstein of Goodyear-Zeppelin Corp. Papers have been listed; the lists and some photographs are available on the University’s Web site. See Internet Resources for on-line access and use information.
University of Texas

Charles E. Rosendahl Collection

Douglas H. Robinson Collection

The University of Texas at Dallas
Special Collections Department
P.O. Box 830643
Richardson, Texas 75083-0643
Phone: 972-883-2570
Dr. Erik D. Carlson, Department Head for Special Collections (carlson@utdallas.edu)
Papers of the late VAdm Charles Rosendahl and the late author Douglas M. Robinson were donated to UT.
Zeppelin Archive

(Luftschiffbau Zeppelin GmbH)

c/o Zeppelin Museum
Seestraße 22
D-88045 Friedrichsafen
Contact: Barbara Weibel (waibel@zeppelin-museum.de)
Phone: 0049 7541 3801 70
Fax: 0049 7541 3786 249
Housed in the same building as the Zeppelin museum, this is a Zeppelin/LTA archive with about 500 linear meters of papers, 7,000 plan sheets and about 17,000 photographs. Another large collection, of books, is housed with the Zeppelin Company archives. Hours are Tuesday to Thursday 9-12 am and 1-5 pm, but an appointment is required.

Name Address Description
Zeppelin Museum Friedrichshafen Seestraße 2288045 Friedrichshafen


Tel: +49 / 7541 / 3801-0

Fax: +49 / 7541 / 3801-81


The Zeppelin museum. Open May-October Tuesday-Sunday, 10 am
to 6 pm; November-April Tuesday-Sunday, 10 am to 5 pm
Aeronauticum, Nordholz

Deutsches Luftschiff- und Marinefliegermuseum

Peter-Strasser-Platz 3, 27637 Nordholz

Postfach 68, 27633 Nordholz

Telephone: 04741-941074

Telefax 04741-941090

Email: info@aeronauticum.de,


Located at the site of a former military airship base; collaborator
of the Heinz Urban museum at Meersburg mentioned elsewhere in these pages.
Has custody of the archives of the now-defunct Marine Luftschiffer Kameradschaft.

1 March-30 June and 1 Sept-31 October: M-Sat: 1300-1700

Sun and holidays: 1000-1800

1 July-31 Aug: daily 1000-1800

26 Dec-10 Jan: daily 1100-1700

Other times: open for groups by appointment

New England Air Museum Bradley International Airport

Hartford, Connecticut


…a true gem and a little treasure of LTA stuff. They have displays
and materials on the Hindenburg, various balloons, a CM-5 engine
nacelle (French WWI airship used by US), a large model of the R-100, a
Packard engine designed for the Shenandoah, and the K-28 control car undergoing
restoration. [Airship-List]
Point Sur Lighthouse Big Sur, California


Lighthouse has a nice display of Macon material, model, diagrams
of where it lies, a short video and overall is worth the trip.
Maritime Museum of Monterey
Stanton Center
Monterey, California


..has a good little area on the Macon, including some recovered
artifacts, models, and multiple videos which include interviews with Gordon
Wiley, son of CDR Wiley. Well worth a visit if you are in the area. [Airship-List]
Moffett Field Moffett Field

(near Sunnyvale, California)


The hangar looks great. You can sometimes gain entrance through the
small museum. This museum is a real treasure. Carol Henderson and her docents
have assembled the most impressive museum I have ever seen. It truly rivals
any professionally run museum such as Smithsonian ones. [Airship-List]
Deutsches Museum Museuminsel 1

D-80538 München

Tel: (089) 2 17 91
Fax: (089) 2 17 93 24

Answering machine: (089) 2 17 94 33

Covers all fields of technology, but reported by Siegfried Geist to
have “a worthwhile section devoted to LTA.” Open daily (except holidays)
from 9:00 am to 5:00 pm.
Stadt Gersthofen Ballonmuseum Bahnhofstraße 10

86368 Gersthofen

Tel: (0821)2491 135 or 101

Five floors of ballooning history, technology and artifacts. Videos
of current aerostatics activity, and a special exhibit on balloons as a
decorative theme. Open Weds 2-6 pm; San, Sun and holidays 10 am to 6 pm.

Meersburg am Bodensee

Schloßplatz 8

D-88709 Meersburg am Bodensee


Tel: 07532 7909

After hours: 07532 41042

Small private museum run by Heinz Urban, specializing in technical
Zeppelin artifacts. Collection includes a spark transmitter from a naval
Zeppelin, the complete bomb-release panel of LZ6 and many other technical
items. Open March through mid-November daily, 10 am to 6 pm. Guided tours
by appointment.
Albert-Sammt-Zeppelin-Museum Hauptstraße

D-97996 Niederstetten


Small museum honoring a commercial Zeppelin officer of local birth
who rose from helmsman in 1924 to command of LZ130. Multimedia presentation
on Zeps.

Zeppelinheim (near Frankfurt/Main)

Zeppelin-Museum Zeppelinheim
Kapitän-Lehmann-Straße 2

63263 Zeppelinheim


A small Zeppelin museum housed in a municipal building in a Frankfurt
suburb, near the airport. When I was there in ’80, the Curator was an old
Zeppelin-Reederei Maschinist.
Zeppelin Museum
Manfred Petersen

Museerne iTønder

Kongevej 55,

DK-6270 Tønder

Tel:. (0045) 74 72 26 57 * (0045) 40 59 62 41

This is the old “Tondern” Zeppelin base.
Central Museum of Aviation & Cosmonautics Krasnoarmeyskaya 14



NAS Richmond Museum

c/o Ford U. Ross

11020 SW 15th Manor

Davie, FL 33324


Display commemorating Navy blimp ASW activity in World War II
Soukup &
Thomas Balloon Museum
700 N. Main St.

Mitchell, SD 57301

Tel: (605) 996-2311

Fax: (605) 996-2218

Museum Director, Becky Pope : beckyp@btigate.com

Museum of Flight East Fortune Airfield

North Berwick

East Lothian. EH39 5LF


Tel: 062 088308 or

0131 225 7534

Models of the R100 and R34, plus the Lion Rampant Standard which adorned
the front of the R34.  There is also a plaque commemorating R34’s
[transatlantic] flight  to be seen [East Lothian was the point of
departure]. Several other LTA items are featured, including film excerpts,
handouts and bits of Zeppelin frame. [Ian Paterson]

Name Address Description
of Balloon & Airship Constructors
P.O. Box 3841

City of Industry, California 91744

email: abac@archivale.com

Publishes quarterly Aerostation (now part of LTAI’s Airshipworld


Airship Heritage Trust c/o Shuttleworth College

Old Warden Park

Biggleswade, Bedfordshire SG 18 9EA


Tel: +44 (0)1767 627195

Charitable organisation with a large collection of airship artefacts
and photographs relating to the

British Airship Programme from its early days at
the turn of the century to the Skyships of the


The Airship Association
The SecretaryThe Airship Association

6 Kings Road,

Cheriton Folkestone, Kent CT20 3LG England.

Email: info@airship-association.org

Premier UK-based LTA association. Publishes the quarterly magazine
Balloon Federation of America Box 400

Indianola, IA 50125

Tel: (515) 961-8809

Fax: (515) 961-3537

Publishes bimonthly Balloon Life
The Bombard Society 6727 Currant Street

McLean, VA 22101

Association of upmarket hot-air ballon operators.
Experimental Balloon
and Airship Association
Brian Boland

PO Box 51

Post Mills Airport

Post Mills, VT 05058

Free membership for anyone interested in experimental balloons or airships
Fédération Française de l’Aérostation 3 bis, square Antoine Arnauld
75016 Paris


LTA Society Box 6191


2000 Republic of South Africa

Japan Bouyant Flight Association

Kyoritsu Kenkyru

402 Hitotsumatsu Bldg 1

2-3-14 Shiba Daimon, Minato-ku




The Lighter Than Air Society 1436 Triplett Blvd

Akron, OH 44306

Tel: (847) 384-0215 (Robert Hunter)

fax: (330) 668-1105 (Attn: E. Brothers)

Publishes Buoyant Flight
National Balloon Racing Association Rt 11, Box 97

Statesville, NC 28677

(740) 876-1237

Naval Airship Association 901 Pillow Drive
Virginia Beach, VA 23454

(757) 481-1563

Publishes newsletter The Noon Balloon
Scandinavian LTA Society Drevkarlsstigen 2-4


S-191 53 Sweden

Zeppelin Kameradschaft Kapitän-Lehmann Str. 2

Zeppelinheim 6078


Internet Resources
World Wide Web (WWW) Sites
Name Description
of Balloon and Airship Constructors
Direct access to the 1600+ item Library List of LTA technical documents
available as reprints. LL can also be downloaded in ASCII or PDF format.
Links to other LTA organizations.
Home Page for Lighter-Than-Air Craft
Hosted at the University of Colorado’s Web server by John Dziadecki,
this is truly the central reference for LTA on the Web.
The Airship Association
Announces AA meetings and other LTA activities, esp. in Britain, plus
membership and subscription information. It has many links to other LTA
Airship & Blimp
Maintained by a young Swiss studying in the USA, it has many links
to other LTA resources, including photo archives.
Balloon Technology Database NASA-funded database of balloon technology, with 2300 documents indexed
as of 1997. Check the “Balloon Technology” box before beginning your search.
Promotions Dirigeables Web site of Paris-based LTA organization. Pages are bilingual (English/French).
Technical Committee

American Institute of Aeronautics and Astronautics

Announces LTA TC activities. Note that permission may be required for
attendance by other than TC members; email first.
Society [USA]
LTA organization with a primary emphasis on LTA history. Web page has
membership information, announcements and an email link.
Naval Airship Association Organization of former US Navy airshipmen dedicated to preserving the
memory of USN airship anti-submarine activity in WW II. Helps maintain
the LTA exhibits at the Naval Aviation Museum, Pensacola, Florida. Page
has announcements and membership information.
University of Akron
Archival Services
Information on how to use the University’s archival services. U. of
Akron is the custodian of the Karl Arnstein Papers.
Alan Gross (Airship Al) Independent consultant and lighter-than-air archivist.
Email Lists


World-wide discussion group about airships sponsored by the [UK] Airship
Association. To subscribe, send email to the address at left with the words
in the message body.


The emphasis in this list is on airships. To subscribe, send an email
message with the word


in the subject line

Balloon Mailing List


Hosts discussion of balloons, both gas and hot-air. To subscribe, send
a message to the address at left with

subscribe balloon [your email address]

in the body of the message.

AirshipList To subscribe, send a blank message to AirshipList-subscribe@yahoogroups.com

Indexes and Bibliographies
Source/Order Number Title & Description
Kent O’Grady

36 Martinglen Way NE

Calgary, Alberta T3J 3H9


email: kogrady@cadvision.com

Index of Buoyant Flight Bulletin – Lighter Than Air Society
260 pp. Cost:

$23.00 US for orders from the USA

$28.00 CDN for orders within Canada

$30.00 CDN for orders from any other country-surface

$45.00 CDN for orders from any other country-airmail

Index of Dirigible – Airship Heritage Trust

23 pp. Cost:

$4.50 US for orders from the USA
$6.00 CDN for orders within Canada

$8.00 CDN for orders from any other country-surface

$14.00 CDN for orders from any other country-airmail

ABAC – Acq. #126 Index of Daniel Guggenheim Airship Institute Report file. This is a different body of work from the papers that appeared in the DGAI’s three Publications. Now if we only knew where to get our hands on the reports themselves…
ABAC – Acq. #301 LTA Society Preliminary Inventory [this is a list of what LTAS donated to the University of Akron, which appears to have retained the Arnstein papers and donated the books to a county library]
ABAC – Acq. #439 Index of LTA Articles in Military Review
ABAC—Acq. #1427 Bibliography of LTA Articles in the US Naval Institute Proceedings 1912-60
ABAC – Acq. #463 David Taylor Model Basin tests of airship models
ABAC – Acq. #713 BuAer Technical Notes, 1916-1924. Another obscure report series.
ABAC – Acq. #802 Index of Aerostation through Volume 7 Number 3 [current volume is 22]. Kent O’Grady (see above) is preparing an up-to-date index.
ABAC – Acq. #946 Index of Airship #s 51-65 (Mar 81-Sep 84)
ABAC – Acq. #1409 Index of US Army Air Corps LTA Information Circulars

Return to ABAC Page

December 22, 2009

Early "Seabasing" Concepts – Still Relevant

Filed under: Aeronautics,Engineering,Floating Structures,Materials,Structures — piolenc @ 6:25 pm

Recently, thanks to the efforts of a friend in the States, a report collection that was formerly available only on 35mm microfilm has been scanned into PDF files. While entering the 400 or so reports into my catalog I came across a 1934 critique, by Charles P. Burgess of the US Navy’s Bureau of Aeronautics, of a proposal by Edward R. Armstrong for a chain of floating airstrips called “seadromes.” These were to consist of an overhead deck and a submerged ballast tank, connected by a double row of vertical cylinders. If that sounds familiar, it should – it’s more or less the standard configuration for modern Very Large Floating Structures (VLFS), including the US Navy’s proposed SeaBase platforms. That was a bit of a surprise to me, because none of the articles on VLFS or sea basing that I’ve seen has acknowledged Armstrong’s much earlier work, which began during WW1 and continued until his death in 1955.

But it gets more interesting, because Burgess’ critique and alternative are just as applicable to the modern proposals as they were to Armstrong’s. Noting that a small waterplane area is the ultimate reason for the stability under wave action of Armstrong’s seadromes, Burgess proposed a more shiplike unitary hull with an anvil-shaped cross section – swollen at the bottom to accomodate ballast, spreading at the top into a wide flight deck – giving a small and very fine waterplane area and much lower resistance to forward movement than the multiple prisms of Armstrong’s concept. In the process, he created a configuration now known by the acronym SWASH – Small Waterplane Area Single Hull – about thirty years before its time. Burgess seems to have been more conscious than Armstrong of the difficulties of deep-ocean anchorage; his concept emphasizes powered station-keeping, which is facilitated by the hydrodynamically favorable hull. Burgess also anticipates modern seabasing proposals, emphasizing the value of a shiplike configuration in getting out of harm’s way if the area starts to “heat up.” I’ve uploaded Burgess’ report to the Files area of the Nation-Builders group on Yahoogroups (file name is BA157.pdf).

A good article on Armstrong and his platform proposals:

The back-issue archive at Popular Science magazine’s http://www.popsci.com also has many articles and news items about Armstrong’s work.

The main difference between Armstrong’s proposal (and Burgess’ counterproposal) and what is mooted now is the current emphasis on modularity. Both Armstrong and Burgess proposed unitary platforms, while nowadays the ability to assemble large units from small, identical components is highly prized – one VLFS concept even involves dynamic assembly and disassembly in situ to suit changing conditions! Armstrong’s configuration is implicitly modular – it consists largely of identical units repeating at equal intervals – which explains its prevalence in modern proposals. Burgess the naval architect, on the other hand, gives his SWASH a beautiful continuously-curved waterline in plan, so his hull could only be built as a single unit. It turns out, though, that minor changes would make Burgess’ configuration “modularizable,” and at the same time cheapen its construction considerably, without compromising its main advantages.

The main change is redesigning the load waterline to consist of a long parallel section, tapered abruptly and symmetrically at both ends. This allows the hull to consist of a variable number of identical “center” units capped with identical “end” units at bow and stern. The end units would have identical propulsion units built in, each capable of giving the whole shebang steerage way and not much more. You end up with the SWASH equivalent of a double-ended ferry, but with only enough installed power for station-keeping. Substituting waterjets with orientable nozzles for conventional screw propellers would allow even very large assemblies to be maneuvered without tugboats. The center units, containing no machinery, could be manufactured in very summary facilities much less well-equipped than standard shipyards. It might be advantageous to make the end units in regular shipbuilders’ yards.

Taking the whole idea one step further, the individual units could be built with double hulls, providing enough reserve flotation to allow them to float, albeit with little reserve buoyancy and with decks awash, even when fully flooded. This would allow them to be assembled into complete vessels or platforms on the water. End units would even be navigable under their own power when unmated and fully flooded – the machinery spaces, located in the ballast tank area, would be sealed and connected with the deck by a narrow trunk like the conning tower of an old-style submarine. This in turn would allow end units and center units to be assembled in separate areas, the end units, mated in pairs, being driven under their own power to where their center units awaited them. The mating operation itself could be carried out in open water, with the end units connecting, independently, with center units one by one until they had enough between them; then the two half-vessels would maneuver to join up.

When newly assembled, the new platform would look like a monitor without the gun-turret, deck flush with the water, but with the hull complete it would gradually be pumped dry inside, ready for fitting-out. It might even be possible to equip the propulsion units to serve as high volume, low pressure pumps, at least in the initial stages of pumping-out.

Materials and manufacturing technology are pretty much ad lib. – steel or aluminum, riveted or welded are feasible, but my favorite is of course ferrocement, which if properly executed can be longer-lived than any other material. Joining method for mating the sections is also up in the air. If the sections are made of steel and they were intended to remain assembled, welding would be the obvious method of choice; bolts are the obvious reversible method, but they are very expensive and would have to be fitted, in our hypothetical open-water assembly method, by divers working underwater and in very poor visibility. One technique that appeals to me is adapted from a system developed for assembling buildings from prefabricated panels in earthquake-prone areas, namely lacing the structure together with steel cables. For permanent assembly, the cables can be grouted into their channels; otherwise they can be secured with cable thimbles at their ends. Post-tensioning would then be possible, which would relieve bending loads on very long assemblies.

Armstrong’s patents:



Burgess’ critique: US Navy Bureau of Aeronautics, Lighter than Air Section, Design Memorandum No. 157, February 1934, “A Proposal for a Single Hulled Seadrome,” by C. P. Burgess. Available from the Files section of the Nation-Builders group on Yahoogroups (see link above).

December 5, 2009

Muscle Powered Blimps

Filed under: Aeronautics,Lighter than Air — piolenc @ 4:44 pm

An Introduction to

Muscle Powered Ultralight Gas Blimps

by Robert (“Rex”) Rechs

Rex is a long-time member of the Association of Balloon and Airship Constructors (ABAC), a contributor to Aerostation magazine and an experienced LTA builder, rigger and pilot. This is in addition to his lifelong work in every phase of aviation as both pilot and mechanic.

This volume is intended to be a companion to his Building Small Gas Blimps, but can be read alone if you do not plan to build this kind of machine, but only want to learn about it.


Section Title Page
Foreword 1
Introduction 2
Acknowledgments 2
Ultralights 3
History 5
Design Considerations 35
Details and Compromises 47
Ergonomics 87
Rocket Science for Pedal Power 87
The White Dwarf man-powered blimp 140
The Brazilian Dirigible Caloi 179
Vintage Designs 186
Shimano Bicycle Parts Catalog 190
Contacts 210
Bibliography 211
Related Books 212
Organizations 213
Conclusion 214
About the Author 215

Softbound – price: $40 (US currency).


Order on-line

Build Your Own Gas Blimp – really!

Filed under: Aeronautics,Lighter than Air — piolenc @ 4:21 pm

Building Small Gas Blimps


by Robert (“Rex”) Rechs

Rex is a long-time member of the Association of Balloon and Airship Constructors (ABAC), a contributor to Aerostation magazine and an experienced LTA builder, rigger and pilot. This is in addition to his lifelong work in every phase of aviation as both pilot and mechanic. There is probably not another individual on the planet who could have put together such a complex and comprehensive book project.  First published in the late 70’s and extensively revised in 1997, this book was published and promoted exclusively by its author until recently, when he kindly offered the publishing rights to ABAC (copyright remains with the author and ABAC’s use is nonexclusive; for permissions, contact the author directly at r.recks@juno.com).  The book includes detailed lists of materials, parts and suppliers. It is extensively illustrated.

Building a blimp – any manned aircraft, for that matter – is a non-trivial undertaking. What is remarkable about this book is that it actually puts the task within the reach of a determined and patient amateur builder.

ABAC’s edition has essentially the same contents as the 1997 revision. Changes made by ABAC are primarily cosmetic: we’ve numbered the pages, added a table of contents and corrected some typographical errors. The new edition is re-published through CreateSpace, an Amazon affiliate. Only soft covers are available.


Section Title Page
Foreword 1
Preface 2
Outline. 3
Glossary 4
Blimp History 6
Design Criteria 7
Ultralights 9
Standard Type Certification 10
Standard Sizes 11
Materials 13
Workmanship 16
Ground Support 22
Masts 29
Hangars 43
Gondola/Airframe 48
Instruments 70
Instruments &
Engines 82
Ducted Fans 86
2-Stroke Engines—-Suppliers 88
4-Stroke Engines—-Suppliers 89
Propellers—-Suppliers 90
Valves and Pressure System 91
Fins 102
Envelopes 125
Fabric & Webbing—-Suppliers 138
Assembly Procedure 145
Bibliography 153
Airship Fin & Rudder Loads
(BuAer LTA Design Memorandum
No. 169)
Gas Airship Parts—-Suppliers 160
Catalog Section. 161
Airship Technical Notes. 185

Soft cover – price: $40 (US currency).


Order on-line

Model Hot-Air Blimps, a cheap intro to LTA

Filed under: Aeronautics,Lighter than Air — piolenc @ 2:43 pm

Model Hot-Air Blimps: How to Build and Fly Them

by Don James

The ABAC gets many inquiries about plans, kits and books for building model hot-air balloons and airships; some even want to build gas free-flight or RC balloon or airship models. On the gas blimp side of things, we don’t hesitate to recommend the excellent Peck Polymers products (nope, we’re not stockholders!), but for our mostly young inquirers on limited budgets we have not had much to offer.

Enter Don James, founding member of ABAC, graphic artist and perennial LTA enthusiast. In 1980 he and ABAC’s then-President George Wright prepared a 20-page booklet for publication by ABAC. Urgent personal business forced the book to be shelved. The master was misfiled in a folder marked “Promo Pamphlets, etc.” and that was that until Yours Truly, trying to put order in the files, stumbled across it.

Don had set out to provide his own children with a cheap and safe pastime that would teach skills and provide instruction, along with hours of fun. The result was an extensive series of free-flight hot-air blimps made of cheap, commonly-available materials and requiring only ordinary tools for construction. The manual that he prepared based on his experiments is extensively illustrated and provides step-by-step instructions not only for building, but also for designing model blimps. For those who don’t want to design their first project, plans for Don’s “Alpha Blimp” are provided in a tabloid-size centerspread. Instructions for building the “firepot” or heat source, which burns old newspaper, are also included. Inflation and flying directions are copiously illustrated, and the final section diagrams modifications for adding a small model-airplane engine for powered flight.

The book has been re-typeset using the desktop publishing technology that was more or less a dream in 1980. Don’s excellent line drawings and well-exposed b&w photos of his own ships have come through in fine shape and have simply been scanned and incorporated as is. Thirty pages, 6″ x 9″ softcover book, dwgs, photos. US $14 postpaid.


  • Order on-line, through Amazon/CreateSpace, using your credit card.

Can You Really Build a Hot-Air Balloon?

Filed under: Aeronautics,Lighter than Air — piolenc @ 2:12 pm

The answer is a qualified “yes.” Here’s what the rigger who literally wrote the book on this subject has to say in the Foreword to his three-and-a-half-volume compendium Build Your Own Balloon:

“This book has been prepared as a guide for the aspiring balloon owner who does not realize the many considerations and details that go into its construction. This book has not been written to encourage individuals to undertake such a  project, but by explaining engineering details it is hoped that you will consult a commercial manufacturer of FAA Type Certificated sport balloons for quality made equipment.

It is realized that many readers will give serious consideration to homebuilt construction; which is, of course, a noble undertaking. Not however without the pitfalls of high cost and poor balloon life; or worse yet, unsafe equipment that the FAA may not let you fly, or may subject to severe operating limitations.

So yes, it can be done, but not just anybody should do it. The author quoted above makes it clear that most of the people who read his book should probably NOT undertake the construction of a balloon. Traits required to do the job successfully are persistence, patience and above all the ability to critically evaluate one’s own work, or at least to listen with an open mind to constructive criticism by others.

Few things look simpler than a hot-air balloon. There’s this big bag filled with hot air, a basket underneath, something to provide heat (where did I put that old camp stove…?). No problem, right? All that’s left to procure is the sandwiches and Champagne.

In fact, a thermal balloon draws on a wide range of skills, from harness-work to welding, and an equally wide range of knowledge from trigonometry to aerostatics to navigation. No matter how much you already know, there will be skills to be acquired and tasks to be contracted out, and you had better be prepared to ruthlessly throw away your own first efforts and start over, because your life will depend on your unwillingness to compromise quality.

Yet even the majority who take things no further than buying the book will learn much that is helpful about the sport of thermal ballooning and about the critical design points of balloons and their support equipment. Balloons are not cheap – that’s the motive for considering building one yourself – and the ability to critically evaluate somebody else’s work could save hundreds, perhaps thousands of dollars, and maybe a life or two.

“Balloon Books”

Build Your Own Balloon Vols I-III + Appendices

Copyright 1996 A.B.A.C.

Compiled by a member of the Association of Balloon and Airship Constructors (ABAC), a licensed balloon and airship pilot, rigger and constructor, these books assemble in one three-volume set the information essential to any amateur considering the construction of a hot-air balloon. They include detailed lists of materials, parts and suppliers. The Appendices contain a brief discussion of gas balloons.


Volume I – Design Criteria contains engineering and safety data. Includes international standards, a review of the state of the art and many time-saving ideas and techniques. (180 pages)

Volume II – Materials & Suppliers contains a comprehensive list of components, specifications and prices [note: prices will be out-of-date], plus information on how and where to order. (206 pages)

Volume III – Plans & Construction contains detailed production drawings, assembly instructions and pictures of most components. (175 pages)

Appendix I – Notes on ultralight hot-air balloon construction.

Appendix II – Notes on spherical gas balloon construction.
[Appendices are bound together in one thin volume, 64 pages]

A word of warning: these books are crudely produced. They are sold for their information content, not their beauty!


Order on-lineOrder on-line through Amazon/CreateSpace

Volume 1 ($30): https://www.createspace.com/5854671

Volume 2 ($30): https://www.createspace.com/5875635

Volume 3 ($30): https://www.createspace.com/6393966

Appendices ($20): https://www.createspace.com/6396032

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