Spy Blimps and Heavy Lifters
The latest thing in airships.
- By Ben Iannotta
- Air & Space magazine, September 2007
DURING THE PREPARATIONS for the 1996 Summer Olympics in Atlanta, local entrepreneur Mike Lawson rounded up a group of investors, pooled $1 million, and bought a one-person, helium-filled airship. His plan: Persuade Olympics officials to rent the craft for security surveillance. “That little sucker would fly about 50 miles per hour,” Lawson recalls.
On a gloomy day in October 1995, the great nemesis of all airships rose up and dashed his spirit. The remnants of Hurricane Opal blew through Atlanta, ripping Lawson’s lighter-than- air ship from its mooring and carrying it away. No one was hurt and Lawson did retrieve the craft, but it was a total loss. He says he learned an important lesson about airships: “What you put on paper does not necessarily work in the real environment.”
Lawson is now the CEO of a small Columbus, Georgia company, Techsphere Systems International, that stitches sail material into spherical airships, which are maneuvered by swamp-boat propellers. (When on the ground, they can be deflated and folded up, so bad weather is no threat and storage is not a big deal.) Now the Army is funding improvements to make them potential spy platforms.
Techsphere is one of a dozen or so companies that hope to find new applications for a technology that’s been around since the late 1700s, when the Montgolfier brothers in France made the first flights with lighter-than-air craft. Some companies are trying to develop an airship that can hover in the stratosphere for months at a time to spy on terrorist camps or spot truckloads of insurgents or cruise missiles in flight. Others are working on craft that are not quite lighter than air: They would combine the lift of helium with the control capability of heavier-than-air vehicles like airplanes. In the Arctic, where global warming is rendering ice roads unusable, the new vehicles would float drill equipment over the soggiest terrain. All these scenarios envision important new missions for aviation’s historic underachievers.
Balls in the Air
Techsphere Systems was born the day Lawson got a call from Hokan Colting, a Swedish-born hot-air balloonist famous in the airship community for advocating spherical designs. In 1988, Colting founded 21st Century Airships in New Market, Ontario, Canada. In the wake of the 9/11 attacks, Colting persuaded Lawson to set up a company to manufacture and market his spheres for use in patrolling borders and other surveillance applications.
To reduce atmospheric drag, most airships are shaped like cigars. Decades of answering the question “Why spheres?” has made Colting adept at delivering an Airship 101 lesson.
All airships, regardless of shape, get their lift by carrying a lighter-than-air gas, usually helium. As an airship rises, the helium expands, so designers must leave plenty of space in the envelope, or hull. Despite the empty space, airships like the Hindenburg kept their shapes with rigid supports. Modern airships accomplish the same thing by filling the void with air-filled bags, or ballonets, which can be adjusted in size by blowing air in or venting it out. As the craft rises, the helium around the air bags expands, pressing on the bags and causing them to vent their air and shrink; the expanding helium also keeps steady pressure on the ship’s hull.
Helium is tricky stuff, though. It collects at the top of a container like an upside-down puddle, and it has a nasty habit of sliding around like liquid mercury. In an airship shaped like a cigar, elaborate steps have to be taken to keep the helium from accumulating in the nose and pushing that end of the craft up. Because they don’t have noses, Colting’s spherical airships don’t have that problem.
In 2003, Colting sat inside one of his spheres with a pilot and took it to an altitude of 20,453 feet above Gull Lake in Alberta, Canada; it was a record for airships. “It was basically to market that we had a technology that could go to that altitude,” Lawson says. In Iraq and Afghanistan, the current threats to U.S. aircraft are shoulder-fired rockets and rifles, so getting to an altitude above 15,000 feet would put an airship out of harm’s way.
The Navy tested the spheres, and now the Army has awarded a contract to spy equipment manufacturer Sierra Nevada Corporation of Sparks, Nevada, to test a 94-foot-diameter Techsphere prototype, the SA-90. The first flight is scheduled for August.
The Army contract specifies that the SA-90 must demonstrate its usefulness by flying at 18,000 to 20,000 feet for up to 24 hours. Aluminum propellers, 18 feet in diameter, will provide maneuvering. Hovering is easy, but engineers want to see if the sphere can fly at 55 mph to keep up with special operations units on the ground. Of course the spheres will never cut through the air as easily as cigars, so engineers are working on a way to compensate. According to company program manager Rick Osmun, Sierra Nevada hopes to use a 10-foot-diameter prototype to show that a cone-shaped “aero tail” attached to the rear of the SA-90 will reduce drag the way the taper of a sailboat’s stern increases speed.
Though the sphere would evade shoulder-fired rockets, a miniature moon hovering over the battlefield could be an easy target for enemy aircraft. Plans call for camouflaging the spheres “air-superiority gray” like U.S. Air Force fighters.
Today, most airship designers have ambitions to reach the stratosphere, 60,000 feet up, which is about 10 times the current average blimp’s maximum altitude. In addition to being safely above commercial air traffic and the winds of the jetstream, the altitude would give customers the ability to stare continuously at the same patch of ground.
Satellites do that now from what is called geostationary orbit, 22,000 miles above Earth. At that altitude, the satellites’ orbit matches the speed of Earth’s rotation. (At a lower altitude, the satellite would orbit faster.) Satellites maintain their orbit around Earth through a balance of two opposing effects: Earth’s gravity and centrifugal force. An airship would balance the force of gravity with aerodynamic lift, buoyancy, or a combination of the two; it could provide 24-hour coverage of a single section of ground but, at an altitude of only 11 miles, with a much closer view than a satellite offers.
New technologies may finally bring the stratosphere within reach. To go to that altitude, airships would need to carry so much helium they’d have to be gigantic; one concept under study by the Pentagon’s Defense Advanced Research Projects Agency could hold a 15-story building. The resulting design challenge sounds like a logic problem: “If you’re bigger, you have more drag, and if you have more drag, you need more propulsion, and if you need more propulsion, you need more energy,” says Ron Browning, director of marketing at Lockheed Martin Defense and Surveillance Systems in Akron, Ohio, a rubber manufacturing center with a long history of balloon and airship fabrication.
Lockheed Martin’s Akron unit might have been a shoo-in to crack the stratosphere were it not for a matter of money. In 2005, the U.S. Missile Defense Agency awarded Lockheed $149 million for construction of a 400-foot-long prototype called the High Altitude Airship. By 2009 a demonstration version was to fly to 60,000 feet and carry a 500-pound payload. An operational version would carry thousands of pounds of sensors to spot hard-to-find cruise missiles.
This year, the Missile Defense Agency announced that budget cuts required it to “eliminate funding for the High Altitude Airship” beyond fiscal year 2007. Lockheed managers are now lobbying members of Congress to restore funding. “We don’t think this program is going to be a dead end,” Browning says. “There are too many positives with it.”
A key to the High Altitude Airship is the hull material. It has to be light so it doesn’t drag the ship down, but it also must be strong to handle the pressure of the helium. (At 60,000 feet, the density of the air is only six percent what it is at sea level, and that low pressure would produce enormous helium expansion.) And because the goal is “persistent” coverage for weeks on end, the material can’t be porous or the helium would escape.
At stratospheric altitudes, there is less wind, but keeping the airship in place will still require a propulsion system. Standard engines are no good because as they burned fuel, the craft would get lighter and slowly rise until the expanding helium split its seams.
Though the prototype will use lithium ion batteries, Lockheed decided that the operational ship should run on solar power. The top and sides of the craft would be covered with photovoltaic cells to convert sunlight into electricity. Extra energy would be stored during the day to keep the craft’s two propellers churning at night.
“The challenge is getting through that first diurnal cycle,” Browning says. “That has not been accomplished before.”
O Mighty ISIS
Under a research effort called ISIS (Integrated Sensor Is Structure), engineers at DARPA hope to build a stratospheric airship containing a giant radar antenna. The antenna will double as the interior support structure—a weight-saving design. “We’re really a radar program,” says electrical engineer Tim Clark, DARPA’s ISIS program manager. “The platform just turned out to be a stratospheric airship. And that’s because we wanted big antennas. You can’t get much more surface area than a stratospheric airship.”
The bigger the antenna, the more detail it can see. “If the wind blows a tree and it sways, you’ve got to be able to separate out the tree movements from a vehicle’s movement,” explains Clark. “It’s easier to do if your resolution on the ground or near the ground is small. You have [fewer] things competing.” The 17,200-square-foot antenna would park itself over areas of interest and transmit and receive radar signals that enable it to spot moving trucks, cars, airplanes, and cruise missiles.
Northrop Grumman Electronic Systems of Baltimore, Maryland, and Lockheed Martin’s fabled Skunk Works unit in Palmdale, California, are working on competing ISIS architectures. Lockheed’s Akron unit is developing the lightweight hull materials. If the technology passes a series of reviews, DARPA will shoot for a flight in 2010 or 2011.
21st Century Sampsons
An airship is built to generate lift. Could that lift be harnessed to haul heavy equipment?
Other air freighters have limitations: Cargo planes need runways, and helicopters are expensive—$25,000 an hour or more. And even the most powerful lifter, Russia’s Mil Mi-26 helicopter (see “We Haul It All,” June/July 2006), has limits: Its maximum payload capacity is 30.5 tons, whereas oil companies need to lift objects weighing up to 40 tons.
What makes using an airship as a hauler tricky is that when the craft drops off its load, the sudden loss of weight would make it shoot up in the air, in turn making the helium inside expand until it blew the hull apart. Keeping tons of ballast—dead weight—on hand to counteract the bounce is an “incredibly awkward” solution, Hokan Colting says.
The answer is to build a craft that doesn’t need ballast, or can create its own.
This was one of the goals of a now-defunct DARPA program called Walrus, which aimed to develop a test airship that would match the C-130’s 30-ton lift capacity. Phil Hunt, DARPA’s Walrus program manager, recounts that engineers explored several concepts for generating ballast on the craft. In one, exhaust from combustion engines would be captured and treated with nitrogen gleaned from the air and bottled hydrogen, a process that would produce water and ammonium—liquid ballast that would keep the craft controllable. Once the ship had landed, says Hunt, you could wheel the payload off and the ballast would be sufficient to keep the craft from wafting away.
Though Congress did not fund the Walrus program in 2006, several companies continue to work on such concepts. Hokan Colting won’t discuss 21st Century Airships’ proprietary approach. For the most part, neither will Worldwide Aeros, which is promising a vehicle called Aeroscraft, scheduled to fly in 24 to 36 months. Edward Pevzner, Aeroscraft marketing manager, will say that buoyancy would be managed in part through the compression of helium.
Officials at the SkyCat Group of Cardington, Great Britain, are more open. When viewed from the side, their SkyCat airship will look like the cross-section of an airplane wing. From the front it will look like a flattened cigar. The inside will consist of three chambers filled with helium and ballonets. The helium will provide 60 percent of the lift necessary to take off with a heavy load. For a full load, blowers will push air downward through two hover pads, keeping the craft above water, ice, or rocks. The SkyCat will use propellers to move itself forward.
After landing, the hover pads will be reversed to “suck” mode to keep the craft on the ground while its payload is wheeled off. No ballast will be necessary.
Since DARPA did not prohibit foreign proposals, the SkyCat Group had hoped to get Walrus program money to build a small SkyCat. But the agency turned that proposal down, and will not comment publicly on its decision, says spokeswoman Jan Walker. The company is presently in bankruptcy, but is hoping to claw its way out with two demo vehicles, which it calls SkyKittens. The 40-foot SkyKitten 1 earned a visit from Pentagon officials after it flew in 2000. Says Gordon Taylor, the company’s marketing director, a 50-foot SkyKitten is planned, followed within 30 months by the first operational SkyCat vehicle. That craft will carry either 20 or 50 tons of equipment; Taylor says managers haven’t decided whether to go straight to the larger version.
Competing companies have come up with designs that resemble the SkyKittens—to a suspicious degree, say the SkyCat developers.
It’s probably not going to be easy to nudge any of these concepts into the real world. A technology as simple-sounding as airships—fabric, helium, maybe a propeller or two—turns out to be surprisingly complicated. “I’ve heard—seriously—people say ‘Well, we shouldn’t have much problem doing something like that; you just take a gas bag and put a couple of engines on,’ ” Hokan Colting says, laughing. But if the design challenges can be mastered, the decidedly low-tech aircraft could become a critical part of the 21st century fleet.