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Inflatable vehicles and structures are gaining ground with advances in materials and manufacturing.
By Barb Ernster
The sophisticated technology behind modern inflatable structures puts them in a category that can be almost as exciting to watch as the development of modern communications—at least for those in the specialty fabrics industry. Advertising blimps and bouncy houses are just precursors to the new generation of inflatable structures, on the ground and in the air, that are opening up new markets with low-cost alternatives to traditional structures. In areas like transportation, cargo, storage, agriculture and aerospace, inflatable structures are taking off.
Lighter than air
Hundreds of lighter-than-air (LTA) airships were used until the 1940s, when modern aircraft replaced them; by the 1970s, new technology warranted taking another look at these vehicles. Today the use of aerostats, blimps and airships is on the rise. Intelligence, surveillance and reconnaissance (ISR) missions and communications for the military are a primary market, but they’re also used commercially for advertising, camera platforms, cell signal and relay platforms, passenger transport and heavy cargo carrying, especially to remote areas other vehicles can’t reach. Their potential has captured the interest of law enforcement, disaster relief operations and border patrol forces, as well as mining, pipeline and logging companies. LTA vehicles are energy efficient and far less expensive to operate than airplanes, helicopters and even unmanned aerial vehicles.
“As budgets see more pressure in every industry, people are searching for lower cost alternatives. For instance, you can produce more ISR data per dollar spent with lighter-than-air platforms than you can with fixed-wing platforms in many instances. The ability to hover and maintain station over an area of interest for long durations is important to many military missions,” says Dave Cadogan, director of engineering at ILC Dover in Frederica, Del. The company designs and develops inflatables for space, government and industrial applications, and is the largest producer of envelopes for LTA vehicles.
One of the most valuable attributes of inflatable structures is their ability to be packaged into small volumes for transport. “It means a lot to be able to deploy something like air bags, marine floats, or even unmanned aerial vehicles (UAVs) on demand from a packed state,” adds Cadogan. “This ability can enable missions, and dramatically reduce system costs of others. They are often much simpler than their mechanical counterparts; and therefore, more reliable and often lower cost to produce.”
Advances in fabric have fueled some of the technology in modern LTA vehicles, which are flying at much higher altitudes that require added strength and durability. High tensile strength materials such as DuPont™ Kevlar® and DSM Dyneema® are often used. ILC Dover conducted much of the early research on Kuraray’s Vectran®, a liquid crystal polymer fiber that provides an excellent strength-to-weight ratio. The company first used the product in the 1990s to develop the Mars Pathfinder air bags.
“We liked it so much that we started using it in other applications, including several airships. That’s an example of how technology has matured over the years,” Cadogan says.
Beyond the blimp
Windcrafter Inc. in Port of Shelton, Wash., incorporates a new technology that relies on vertical lighter-than-air, gas-filled bladders, giving the airship vertical lifting capability. Modeled after the carangiform motion of fish, the Carangi Airship can move up and down and side-to-side, operating more like a flying sailboat than an airship. The patented design transfers the payload capacity through the outer layer of fabric from the top of the cylinders to the bottom keel where the weight is carried. The inner cylinders, or pressure envelopes, also made of fabric, give the ship its shape; it requires no inner structure.
“Customers want to pay for payload, not extra structure. The fabric is everything for us,” says inventor, co-founder and fabricator Steve Swearingen. “Originally it had a lot more structure until we started working with the fabrics and could transfer that lift, just like a sail on a sailboat. It truly does sail the skies, and that’s how we can get away with very little motor.”
The airship’s design does not require strong fabric. The company primarily uses Ripstop Dilon spinnaker fabrics for the outer skin and inner cylinders, sewn with a double seam, and ½-mil Mylar® film for the inner bladder. The system uses only a quarter of the helium that other lighter-than-air vehicles require, and can be filled with hot air or hydrogen. The company is also developing vacuum cylinders that would have even more lift than helium at less cost.
Swearingen is excited about the possibilities for this technology. The ships can be built tall and thin like a yacht or short and fat like a barge, he says, in various sizes for various applications. While still in the prototype stages for some of its larger airships, the company is closer to reaching the manned aircraft stage, and is currently developing a 200-ft. tall by 120-ft. long ship with a 40,000-lb. capacity capable of carrying trees, people and heavy cargo.Â
“I see everything from a throwaway military backpack-type mission that can lift 20 or 30 pounds and gives over-the-hill surveillance, right up to the high-quality drone materials that give years of performance, or to carry pipeline materials to Alaska and take supplies to villages in the Klondike,” Swearingen says. “This type of ship could be used to sail through these valleys and save a lot of fuel.”
Ground-breaking surface inflatables
One trend driving the temporary and permanent inflatable structures market is an increasing requirement for energy efficiency and better ‘green’ credentials. Environmental concerns are one area in which inflatable structures have a significant advantage, according to David Kelsall, co-founder of Tectoniks in Shropshire, England, a company that designs and manufactures a range of inflatable structures for events and more technically demanding applications.
Perfectly viable structures capable of satisfying stringent building codes can be produced using a tiny fraction of the material required to produce masonry, metal or timber structures, which is good news from an environmental point of view, Kelsall says. It also greatly reduces the weight and packed size of the structure, making it highly portable.
Tectoniks has produced portable cold rooms and structures that meet the requirements of international energy-efficiency codes such as IECC 2012, and are able to withstand higher wind, snow and other loads. The company predominantly uses PVC-coated textiles, preferring Serge Ferrari Précontraint® 402, 502 and other architectural fabrics, and combines hot-air welding, stitching, sealing and adhesives in construction.
“Inflatable structures provide a natural level of thermal insulation, and this can be further enhanced with the addition of modern, lightweight, flexible insulation materials which can be incorporated with the inflatable elements themselves,” says Kelsall. “Add this to the fact that, being virtually air-tight, our structures require very little power to maintain operating pressure, and you have a finished structure that is highly energy-efficient in all aspects of its manufacture, installation and operation.”
The global economic situation is another trend that cannot be ignored, he adds. Individuals and businesses are seeking the best value for their money, which could benefit the temporary and inflatable structures industry. Decision makers considering a substantial investment in commercial buildings might look more favorably on buildings with greater versatility—buildings that can be relocated, expanded or adapted to meet changing requirements.
Concerning permanent inflatable structures, Kelsall says it is not a question of whether it can be done, but whether people will find the money to make it happen. It is possible to live in an inflatable structure long term, he says, but it is still easier and less expensive to put up wood to survive hurricanes and tornadoes. Emergency housing for long durations is one valuable use, but there must be a budget to manufacture and store them so they’re ready when an emergency occurs.
There’s also a greater focus on safety, following recent tragedies at events in the U.S. A meeting between members of the U.S. Event Safety Alliance and politicians from the state of Indiana resulted in an agreement to adopt the U.K. Health and Safety Executive “Event Safety Guide” within the United States, and create a U.S. version which will establish a far-reaching set of industry best practices. Kelsall notes that the outcome of this will increase awareness of the importance of ensuring that temporary structures can be operated safely in adverse weather conditions, particularly high winds.
Safety first
Dynamic Air Shelters in Calgary, Alberta, Canada, has adapted its inflatable and air beam systems to be more resilient and more resistant to forces by applying features of other mechanical systems. The company uses quality fabrics from Mehler Texnologies Inc. and Naizil Inc., but a great deal of its system involves the transference of loads from the fabrics to greater load-bearing cables and straps, so nylon webbings and coated cables are critical. The results are blast-resistant buildings and air-inflated shelters that are secure and stable in conditions up to category 3 hurricanes (which Dynamic Air shelters have survived).
President Harold Warren says the resilience of an air beam system makes it more secure in conditions such as earthquakes, when the vast majority of deaths are caused by the collapse of buildings. “An inflatable is inherently safe in such environments. It is not a matter of predicting where earthquakes will be and putting the shelters there; responders and survivors experience significant aftershocks, and the facilities we give these people should be inheretntly—if not absolutely—safe.”
The company is seeing trends in advancing compliance with safety and security, which means advancing engineering while trying to hold back increased costs—not the easiest thing to do.
“There are some amazing inflatable products out there such as Vertigo (HDT Global) and others whose material science is pure mastery,” says Warren. “Still, they and we have to compete against relatively conventional frame and cover systems in an economical environment where price continues to rule the day. Advanced levels of innovation applied in specific scopes of a market will allow some of us to hold secure positions in some markets for particular times.”
The growth areas can be wherever the human imagination takes them, he adds, noting that NASA prescribes that it will be inflatable buildings we take to other planets. “They are very compact to transport and require only that there be an increase in the atmosphere contained in the inflatable regardless of what environment they are in.”
A rigid outlook
Toward that end, ILC Dover has been developing a technology called rigidization, which is not new, but is of interest for its ability to take an inflatable or soft structure and turn it into a rigid composite structure. ILC has advanced thermoplastic shape-memory polymer composites that use changes in temperature to change state, and UV/visible light thermoset polymer composites in the manufacture of inflatable rigidizable products.
“Inflatable buildings require power to run the inflation system for the time it is deployed. Rigidization is one way inflatable buildings can be made more permanent and durable, and can enable long-term remote operation,” says Cadogan.
The aerospace community is interested in this type of structure, because they need a compact size to launch antennas into space.
“You can save millions of dollars in launch costs if you can reduce the package size and fly on smaller or fewer launch vehicles. So you can see how inflatable space habitats would have some advantages over rigid cylindrical habitats,” says Cadogan. “We’re also looking at several terrestrial applications that could benefit from this rigidization technology.”
As awareness of their capabilities increases, demand for inflatable structures of all kinds will continue to grow. This is already evident in the increasing use of inflatable technology by architects in modern buildings, notes Kelsall. “To a large extent, this has been and will continue to be driven by advances in materials, design and manufacturing processes.”
The same can be said of inflatables in the air—the sky’s the limit, but eventually you’ll probably need something that will fit in your garage.