|BlueSky Business Aviation News|
As with any new infrastructure technology, from the first Roman roads to the latest in internet cloud storage, demonstrating its usefulness is crucial to generating the initial acceptance that leads to willingness to pay for its construction. In my opinion, this should be done prior to jumping into a huge international project worth billions or tens of billions of dollars. In short, I believe we need a proof-of-concept demonstrator, a pilot project, if you will.
The top-level design issue is moderately straightforward. There are places in the world that could benefit from a well-located airport in the ocean. The vast majority of aircraft in general and commercial airliners in particular are dedicated land planes, requiring smooth, hard-surfaced runways for operations. The option of using dedicated seaplanes or flying boat designs on long, over-water routes - preserving the option of a water landing in an emergency while still being economically competitive - has long since gone away. The obvious solution to accommodate highly efficient aircraft is a smooth, hard-surfaced runway anchored in deep water.
An appropriate airport for business jets and small to medium sized airliners would need a runway length of 5,000 feet to 6,000 ft, depending on a number of factors, which does not include nearby obstacles since we are well out to sea (for most applications) and neither the approach path nor the departure path need cross land for a very long time. Since our pilot project is pretty much by definition a sea level airport, we can favor the shorter runway without too many problems. If properly designed, we can start with a basic length (4,000 ft, 5,000 ft, or whatever the builder believes is appropriate) and add to it if the increased length becomes necessary due to increased traffic. Modular construction is the key to a long economically useful life.
Outline of mission
For the design to most effectively support the mission of the facility, we need to know what the mission is. The mission of this demonstrator project has a number of different parts and Im not saying this is the actual, ultimate mission we should design to, but its not a bad starting point.
With our mission more or less in hand, lets take a look at what this kind of airport should look like and what capabilities it must have.
What should it look like?
My first thought was to keep the runway width to a minimum, say 150 feet (call it 50 meters). To my eye, that looks a bit narrow. I understand that additional width usually means additional cost, but I also understand that missing the runway, or sliding off into the water because of a landing gear failure would be very expensive and is something to be avoided, if we can reasonably do so. So, I think it has to be significantly wider than 150 feet.
Another design consideration is lateral stiffness. A very long, very narrow runway has low lateral stiffness. This means that even with excellent underwater anchoring, we run the risk of the runway developing a bend or curve, particularly if the airport is deployed cross-wise to a strong current in order to align with the prevailing winds. It is very difficult to land a fast, heavy jet on a curving runway. We can improve the stiffness, and therefore resistance to deformation by a strong lateral current, by increasing the width from 150 feet to 250 feet, 300 feet, or more. To achieve the same degree of lateral stiffness at 150 feet of width as we get pretty much for free at 250 feet would require a lot more steel and concrete, so the wider runway may well be the less expensive option, as well as the safer one.
Some structural systems dont even float. Thats right; they are built up from the sea bottom, or at least piles are driven into the sea bottom and the rest of the structure attached to the pile foundation. Gravity-based structures, fixed platforms, and compliant tower systems would work in places where we knew an airport had to be and we knew it wouldnt need to be moved. For example, ETOPS airports along the New York to London route would seem to be pretty permanent as these things go.
On the other hand, we may want the option of moving the airport for various reasons, and there are several proven flotation systems that can be put to use immediately. These come from the oil industry and have a solid history of use as ocean drilling and production platforms in very deep waters, some as deep as 5,000 feet. Both tension leg and semi-submersible designs appear suitable for our project. Both systems would have little to no movement at the deck due to wave action.
Another very interesting, though untried, technology is pneumatic stabilization, which is essentially a group of cylinders closed on top, but open below, allowing the water to rise up into the cylinder, compressing the air inside until it supports the weight of the structure. This is the system that the Euphlotea group proposed for the floating San Diego International Airport.
Not an issue that jumps out at you when discussing deep ocean floating airports, right? However, I am not talking about parking for automobiles, but rather for parking of an aircraft after landing. It cannot sit on the runway until it is time to leave again; this blocks the safety function of the airport for transiting flights. We need a place to safely park the aircraft after it lands so that it can be unloaded and loaded, refueled (and de-fueled, if necessary for maintenance), repaired, and inspected prior to take off. These are crucial operations and cannot be safely performed in the middle of an active runway.
Aircraft carrier methods
One method is to follow the usage of the large aircraft carrier warships, and push the landed aircraft to the edge of the flight deck, allowing operating aircraft as much width as possible. Given a 250' or 300' wide runway, you might think it a pretty reasonable option. After giving this some thought, I do not really care for this option. With wingspans and overall lengths approaching (and in some cases, exceeding) 100', it is too easy for a damaged or malfunctioning aircraft to veer off the centerline of the runway into a parked aircraft. I've seen footage of World War II carrier operations where this happened and it wasn't pretty. Having concrete barriers in the center of the runway seems to rather defeat the purpose of having a wide runway to begin with.
Another option from the aircraft carrier world is a big elevator down to the hangar deck. The cool factor is huge, I agree. However, it takes a lot to move an 80,000 lb (or heavier) aircraft with a wingspan of over 100', to say nothing of the requirement for a hangar deck, which also has an enormous cool factor.
To accommodate the current generation of single-aisle transports, the 737s and the Airbus A320 family, our hangar deck would need to have a minimum of 42 feet of clearance and 120 feet of free span. To have anything at all in the overhead other than lights, such as a traveling crane or even ceiling fans, we need at least 50 feet. To be able to walk past the wingtips, it would also be nice to have about 150 feet of free span, which again, argues against the minimum width runway.
In my mind, if we cant have a hangar deck, then the best remaining option would be a long structure parallel to the runway, much like a taxiway, but with a rounded, semi-cylindrical hangar structure in the middle much like the older World War II aircraft hangars. The low, rounded shape would create a minimum of drag during a passing tropical storm, hurricane or typhoon, and still provide the vertical clearance for the empennage of small jet liners.
One far less exciting option is to have a large platform off one end--connected by taxiway or directly - to accommodate parking of aircraft. Something roughly 200 feet square would safely accommodate a single heavy jet like a G650, a Q-400, or a 737 with enough room around it for safe servicing and loading.
Of course, if money is no object, then a separate 300 foot wide taxiway and ramp parallel to the main runway would be very nice since it would safely separate parked aircraft from aircraft landing or taking off. I envision it separated from the main runway by some distance, perhaps a hundred feet or so.
Air traffic control and navigation aids
For efficient air navigation, we need local radio navigation aids. The usual ILS installation coupled with an on board VOR and DME would seem appropriate, perhaps with an ADF beacon as a back-up. Over time, of course, a non-precision GPS approach can be published. The air traffic controller, assuming we have one, would undoubtedly want a modest air search radar, perhaps something with height-finding capability. While we arent designing for a heavy traffic environment, we should keep in mind that the effects of bad weather or on board malfunction. What aid we can provide to the air crews would be deeply appreciated, Im sure.
As a safety airport, we must have the ability to refuel aircraft, probably multiple aircraft between refills of the main jet fuel tank system. We must also have the ability to de-fuel the aircraft in order to repair damage inside the tanks and that fuel has to be stored somewhere separate from the main tanks. Fortunately, any kind of decently stable deep water structure comes fully equipped with a number of different options for storing fuel. These are well understood. Mostly, I am pointing out the obvious here.
To my mind, one of the most important design questions for the fuel storage facility is how are we going to make sure we do not spill fuel into the water? How can we recapture a spill? I like the idea of a fuel dock equipped with gutters and drains that lead directly to a spill containment and fuel re-filtration system. To minimize the fuel piping, I would want the fuel storage tanks in the legs that support the fuel dock. This is an area I think we would want to have exceptionally capable fire suppression equipment as well as water spill containment equipment.
Part of the reason for existence of a safety airport is to allow a malfunctioning or damaged aircraft to land safely, offload the passengers, and repair the damage. This leads inevitably to some kind of maintenance and repair capability. When we talk about maintenance capability we are talking both floor space sufficient to work on the airplane (like the hangar deck or a separate, though attached, facility - preferably with cover and a controlled climate as salt air, while bracing for human beings, is not the best for aluminum aircraft). This ties back in to not parking aircraft on the active runway, for if we do, there is no way to fly in the necessary replacement parts or specialized personnel. On board maintenance capability could become critical in the event of an engine failure of another series of volcanic eruptions.
Fire and rescue
As at any airport, we must have a fire and rescue capability. This is common sense. However, the at sea part complicates things considerably. If an aircraft catches fire or crashes on the runway or taxiway or on the hangar deck, we already know how to cope. However, if the airplane skids off the runway into the water, or ditches before it gets to us, we still need to be able to pick up the survivors, mark the location of the wreckage, and possibly even haul it out of the water. This implies relatively large, fast seaworthy rescue boats, crews to operate them, and on board accommodations, or possibly larger hovercraft or even an ekranoplane - something with range and speed to get to a downed airliner before it sinks. This is a new area; Im not aware of anyone doing this sort of thing.
Hotel & restaurant
Those hundred or so passengers and crew have to stay somewhere. Lets not be trying to figure out where to put them after the first aircraft arrives. With this large a structure, creating a medium sized hotel with a couple hundred rooms is not a problem. In fact, it is a potential profit center. There is no reason why the same company that runs the hotel cant operate a section of long-term stay apartments for permanent staff and operate a resort of sorts for incoming VIPs and vacationers. For the second generation of floating airports, there is no reason at all that a convention center cant be added to the basic package, allowing the airport the same sort of flexibility.
If the local fishing is at all decent, the local restaurant could build quite a reputation on the quality of the seafood. I am not advocating enormous trawlers here, but a couple of charter boat fishermen could supply quite a bit of fish to the restaurant, which could not only serve as a place to eat, but also as a place to put the finishing touches on gourmet chefs who specialize in seafood. If we are sheltering local fish farmers, it becomes even easier.
Having a large floating structure in the deep ocean leads me to think that not only would it be a safety port for aircraft, its primary function, but also for boats. In fact, just having a large airport in the ocean means that boats will naturally seek us out. There is nothing wrong with this, regardless of the terra terra terra mindset that is so prevalent these days with the Security At All Costs No Matter What set. Boaters have money. Boaters will often want to sleep out of the boat a night or two while enjoying a meal that didnt come from a can. Sometimes they need to swap out personnel and sometimes they need medical attention.
Pleasure boaters to one side, our floating airport also needs our own boats to handle water rescues in case a damaged aircraft has to ditch before it can land, plus our primary connection to the nearest land is likely to be by boat. So, we must have a marina anyway simply to function properly. Building it large enough to have some extra slips to lease at an overnight rate only makes good business sense.
Now, you may think that incorporating a marina into the basic design is not particularly challenging. And maybe it is for those structures designed for in-shore operation in protected waters. Piece of cake, really. However, it does get quite interesting when we consider the problems of open ocean docking and how the marinas need for relatively placid water conflicts with the basic flow-through strategy for minimizing wave-generated motion of the main structure. Plus, this has to be done in a cost-effective manner; we arent talking infinite money like some kind of defense contract. This has to make economic sense. My best thought so far is to combine the marina with a wave-energy generation station in a separate structure off of, but connected to, the main structure. I still favor a way to bring the hovercraft on board the main structure, perhaps a floating ramp. Its an interesting problem.
An unpleasant necessity, if we think of it only in terms of plane crashes or aero-medical emergencies. However, an on board hospital can serve multiple purposes such as health care for the permanent staff and potentially really importantly, as a health care outreach for the local peoples. Our primary mission is, after all, to provide access to air transport for people in remote areas. Ive been to quite a number of remote places and never yet has the health care been up to standard. An on board hospital could provide a base for Doctors Without Borders/Mιdecins Sans Frontiθres, for example, or World Health Organization doctors. If there are serious disease issues on land, we might also host some researchers. I dont think we can pass up this kind of opportunity to do good in the world.
Light industrial activities
Because the airport will be totally self-sufficient in terms of power, water, and waste processing (thats right, no pumping overboard without processing first) and because we have a direct air connection (FedEx? UPS?) back to the Rest Of The World, it becomes a natural location for all the usual light industrial tasks that human settlements would need. Machine shops, light metal fabrication, appliance repair, metal plating, and who knows what else. Some, of course, will be directly related to aircraft and airport maintenance, some related to boats, and others strictly oriented toward the land. Should be interesting to see what makes sense.
This is quite an exciting area of development and really, it is our main focus for technology development in our role as a real-world laboratory. Our airport should be, and can be, entirely self-sufficient in terms of electrical power. Properly designed, we should also have power to sell to the on shore establishment. The airport structure can be the focus of a fairly wide array of power generating technologies.
Solar panels are an obvious baseline solution for our initial power requirements. However, solar is complicated by energy storage requirements to compensate for nighttime and cloudy or stormy days. It does make for a handy, reliable back up system. I am trying to avoid huge banks of lead-acid batteries because of their environmental impacts as well as their expense and requirements for regular maintenance.
If the wind is generally reliable in the deep ocean, waves are no less so. The technology surrounding wave energy conversion appears to be struggling. The energy is there (Ill spare you the math) and freely available. The market appears to be filled with a wide range of competitors from around the world. I think that a real-world laboratory like our pilot project airport, would help push along development of this technology. The potential is quite exciting.
Ocean thermal electric conversion (OTEC) is the dark horse in all this. It can operate around the clock, unlike solar. It can operate at the same level in a dead calm as in a storm. The cold water brought up from the depths can be used to cool a facility located in the tropics (the place with the largest temperature differencecrucial to the operation of an OTEC plant). The nutrient-rich cold water discharge can be used to nourish the kelp forest or the fish farms. Desalinated water from the plant can be used for drinking water, or irrigating an on board farm. There are challenges aplenty, though. Currently, we need a plant that can operate reliably and efficiently with smaller temperature differences. There are issues to be solved with microbial fouling of heat exchanger surfaces as well as seals that can hold up over time in a not terribly friendly environment. And there is the long-term environmental issue of dissolved CO2 in the cold water that comes out of solution when it gets to the surface (can we run that through an on board greenhouse?). There is quite a bit of work that can be done with this technology.
Other potential activities
With a large structure required simply to support the runway, we get the bonus of a lot of extra indoor space, if we choose. With that space we have the option of doing some other interesting activities such as a seaborne university, local shopping center with access to goods from around the world (no, I dont expect Wal-Mart would be interested), local emergency preparedness, scuba diving, and deep sea research. In the area of eco-habilitation, we could support fish farming, kelp farming, algae farming, and marine habitat restoration.
Fish farming? Really? Really. And with a ready-made air-link back to The Rest Of The World which functions as our market. So, really, we arent talking catfish here. This could potentially be an entirely new kind of commercial fish farming. Can cod be farmed? Yes. The University of Maine recently spent two years exploring that very issue. One of the things holding back commercial cod farming is the poor water quality inland. Out in the deep ocean, water quality wouldnt be a problem, leading to healthier stock with higher survival rates, and potentially higher feed conversion rates. If combined with the nutrient rich cold water discharge of an OTEC plant, the possibilities become really exciting.
In short, the airport functions in part as a sort of business incubator. We do not yet know what kinds of businesses will do well on this kind of environment, but there is no question that we should be structured in such a way as to support the start up of new kinds of enterprises.
Connections to the land
A really interesting design issue is how we connect the airport to the land. I think that the floating underwater railway tunnel the San Diego people proposed is fascinating, but probably not cost efficient for this pilot program. More reasonable alternatives appear to be a floating causeway, which is terribly expensive, or boats. I think we can also add seaplanes to serve the more distant, outlying areas, but really, the most cost efficient method would be boat service, whether a swarm of small boats, or dedicated ferries or (my personal favorite) over-the-beach hovercraft. I think the hovercraft, while expensive to operate compared to a boat, needs no shore-side infrastructure, which may be an issue. And, being an airport, we can always support the use of helicopters.
On shore airports have terrible issues with conflicting land use, noise pollution,
Move airport off-shore, minimize disturbance of sensitive habitat, minimize impact of jet noise, provide a habitat for marine lifekelp forest, shellfish, barnacles, possibly even coral if sea temperature is low enough.
We must consider the potential adverse impacts on pelagic fish migrations, whale migrations, and turtle migrations. An open structure like the semi-submersibles, tension-leg structures, and compliant towers all offer an open pathway for migratory creatures. Whales can surface inside to breath, and schools of fish can flow through without let or hindrance - unless we are fish farming underneath, of course. Thats a different set of questions, though.
The design must also address potential pollution runoff - jet fuel and other hydrocarbons, unprocessed human waste, etc. I do not believe these are terribly difficult problems. I suspect that most of them have already been solved, one way or another, for off-shore oil platforms. That said, we simply cannot use the time-honored navy method of simply dumping it overboard. Those days are gone and the sooner we recognize that and design accordingly, the better for everyone and everything.
Will our airport shade out a vibrant underwater ecology? This is an excellent question. Light in the ocean can penetrate as deep as 200 meters (660 feet). Below that depth, it is entirely dark, shadowed by the water column above it. If we anchor the airport in water deeper than 700 feet, we are shadowing nothing. In fact, simply by being there, the structure offers a substrate to the local marine life at a depth where light does still penetrate. This allows us the opportunity to create new marine habitats, perhaps a new kelp forest, which itself would help moderate wave action and provide a complex habitat for other marine life.
A joint venture
The fundamental idea here is that this pilot project should be something that the industry creates for itself, a real world laboratory to resolve a lot of the open questions about very large floating structures and the best design practices. However, this project embodies a lot of risk for a single firm, if there is a single firm actually capable of encompassing an assignment of this magnitude. I suspect a number of firms, both competitors and allies from other industries, would need to pool their expertise and resources to maximize the chances of success and minimize the risk, the classic argument for a joint venture. Who knows? We might even be able to get a favorable tax treatment out of this.
Another solid argument in favor of a group effort is that zero very large floating structures have been built to date. And yet, they are a subject of much discussion among those who would like to see floating cities, floating factories (we could literally have a floating factory that produced modules for other very large floating structures), and yes, even large floating international airports next door to thriving metropolitan areas. For the various players to move into this market in a bigger, more profitable way, we need some experience designing, building, operating, and maintaining very large floating structures. The only way to get this experience is to do it.
Much that will be learned in the various design studies should be widely available to those who are interested in this kind of construction and all the ancillary issues that go along with it. In short, we are exploring a whole new industry, and the best way to ramp up our world wide industrial capability is to look at a lot of different options and explore their potential impact on the design. We used to call those trade studies back in my day. To extend it as far as I can, I would love to see crowd-sourcing used resolving some of these design issues. A number of for-profit companies do exactly that, yes, even the corporate bad-boys of the pharmaceutical industry are moving this direction.
It seems obvious that the first movers here will garner the big wins. Those who have a track record are obviously far more likely to be chosen to design and build the next generation of very large floating structures, whether they be airports or cities or factories or something else entirely.
The potential is vast. Who will move first?
Terry Drinkard is currently consulting on an aviation start-up. His interests and desire are being involved in cool developments around airplanes and in the aviation industry. Usually working as a contract heavy structures engineer, he has held positions with Boeing and Gulfstream Aerospace and has years of experience in the MRO world. Terrys areas of specialty are aircraft design, development, manufacturing, maintenance, and modification; lean manufacturing; Six-sigma; worker-directed teams; project management; organization development and start-ups.
Terry welcomes your comments, questions or feedback. You may contact him via firstname.lastname@example.org
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