Paris 2011: Persistence brings new rewards for airships and hybrids

 - June 19, 2011, 10:00 AM

A comeback for airships? How many times have you heard that before? However, thanks to generous funding by the Pentagon, four separate projects to develop very large buoyant air vehicles for unmanned persistent surveillance missions are under way in the U.S. Three of them are to take to the air within the next few months.

Leading the way is Northrop Grumman’s Long Endurance Multi-Intelligence Vehicle (LEMV), which the company describes as “a revolutionary concept that will shape the future of ISR.” It’s not actually an airship, although it has a nonrigid envelope that is inflated with helium. In fact, the elliptical and cambered shape gains up to 40 percent of its forward lift through aerodynamics. This is a big beast–300 feet long, 113 feet wide and 85 feet high, with an envelope volume of 1,340,000 cu ft. That is longer than a football field and taller than a seven-story building.

The LEMV is powered by four 350-horsepower supercharged diesel engines, housed in vectoring ducts with blown vanes that direct the thrust for takeoff and landing. Pneumatic tubes contained within skids on the underside of the two outer hulls facilitate the landing by “sucking” the vehicle to the ground and securing it. Unlike an airship, therefore, the LEMV has no need for a network of enormous mooring masts or winch-and-cable arrangements. British company Hybrid Air Vehicles developed this design and is the most significant subcontractor to Northrop Grumman.

The U.S. Army Space and Missile Defense Command (USASMDC) is sponsoring development of the LEMV. In June 2010, it awarded Northrop Grumman a contract worth $517 million for “up to three” systems. “This opportunity leverages our leadership positions in UAVs, C4ISR systems and integration, and moves Northrop Grumman into this rapidly emerging market space of airships for the military and homeland defense arenas,” commented Gary Ervin, president of Northrop Grumman’s Aerospace Systems sector.

The LEMV is supposed to fly at altitudes up to 22,000 feet for 21 days at a time. It can be optionally piloted for long ferry flights to the region of operation. The maximum speed is 80 knots and the loiter speed is just 30 knots, with low-speed control provided by bow thrusters. The payload is a mix of sensors, such as radar, SIGINT and full-motion video, weighing up to 2,750 pounds in total. An open-architecture design provides plug-and-play capability so that new sensors can easily be added, according to Northrop Grumman. The LEMV can be operated from the Army’s Universal Ground Control Station and its data will be fed to the Army version of the U.S. military’s standard processing and exploitation system (DCGS).

Northrop Grumman described the development schedule as “very aggressive,” but nevertheless completed the critical design review of the LEMV last February. Hybrid Air Vehicles was due to deliver the engines, propulsion ducts, bow thrusters, fuel tanks and payload module from the UK last month. The fabric and envelope are being manufactured in the U.S. Northrop Grumman said it would inflate the hull this spring, fly the LEMV by late summer and ferry it to the Yuma Proving Ground for customer trials in November. Early next year, it would deploy to Afghanistan for a Joint Military Utility Assessment. Hull inflation has apparently slipped into the summer, but Northrop Grumman was not able to provide further comment in time for this article.

Blue Devil 2

Meanwhile, the U.S. Air Force is sponsoring what looks like a very similar demonstration, at much lower cost. A contract worth $86.2 million has gone to Mav6, a three-year-old company that is now led by the Air Force’s former ISR chief, Dave Deptula. Mav6 describes itself as an “agile systems integrator” that customizes off-the-shelf equipment to rapidly equip front-line units with innovative new systems to fight an asymmetric enemy. Mav6 plans to add a suite of sensors to a conventional airship that would fly at 20,000 feet for up to seven days. It also is to be deployed to Afghanistan for trials early next year.

The project is dubbed Blue Devil 2, after the comic-book superhero. It is related to Blue Devil 1, a separate contract that was awarded to SAIC, to integrate and operate wide-area full-motion video and COMINT sensors on a King Air aircraft. The airship will be provided by TCOM, which is best known as a supplier of tethered aerostats, but which has also produced the Skyship series of airships. However, the “Polar 1000” design that TCOM is building for Blue Devil 2 is much larger–370 feet long with an envelope volume of 1,400,000 cu ft.

“It’s the biggest airship since the 1960s. Fabrication is in progress and we expect to fly in September,” said Mav6 vice president business development Dave Bithner. He told AIN that by using a traditional hull the company can focus on its specialty–customizing and integrating the wide-area sensors and the communications architecture. In particular, there will be sophisticated onboard data processing and storage so that users on the ground can “pull” the information as required down austere datalinks.

Not everyone is convinced that the LEMV and Blue Devil 2 demonstrations will succeed. Ed Herlik is a former U.S. Air Force pilot and engineer, who studies UAVs and lighter-than-air technology for the Market Intel Group (see box). “They will be vulnerable to attack from the ground,” he told AIN. “Remember that their advertised operating altitude is 20,000 feet above sea level. Many areas of interest in Afghanistan are well over 10,000 feet. Also, terrain masking will negate the value of their wide-area sensors,” he continued.

High-altitude Airships

Herlik’s air force career included work on the promising area of “near-space” surveillance concepts. The concept of using unmanned, electric-powered airships for surveillance and communications at very high altitudes is seductive. They offer huge cost savings over satellites and should also be much cheaper than specialized high-altitude UAVs to deploy and operate.

By floating in a geostationary position above the jetstream, an airship could survey a 600-mile diameter area and millions of cubic miles of airspace. One drawback: they must be very large, since a huge volume of helium is required to sustain lift at 70,000 feet. Conventional airships reach their “pressure height”–the altitude at which they must begin to vent helium–at about 10,000 feet.

Free-floating balloons are routinely used to loft scientific payloads to very high altitude. In 2005, a small stratospheric airship developed by balloon-maker Aerostar, together with Southwest Research Institute, reached 74,000 feet with a 60-pound payload over New Mexico. The sponsor of that effort, named HiSentinel, was the same Army organization that is funding the LEMV. In 2008, the USASMDC also took over the high-altitude airship (HAA) project that had previously been run by the U.S. Missile Defense Agency.

Lockheed Martin has worked on the HAA project for some years. The company’s Defense and Surveillance Systems unit in Akron, Ohio, has an 80-year heritage in lighter-than-air systems and is another supplier of tethered aerostats. Compared with the company’s aerostats, even the subscale high- altitude long endurance-demonstrator (HALE-D) airship that Lockheed Martin has built at Akron for the HAA program is more than twice as long–240 feet. The hull volume is 500,000 cu ft.

The first flight of the HALE-D is scheduled for July at Akron. The goal is to fly for at least two weeks at 60,000 feet, while providing 500 watts of power to a 50-pound communications relay payload. The technical challenges for stratospheric airships include developing lightweight propulsion units, solar energy capture and storage, and high-strength fabrics that can resist persistent exposure to ultraviolet radiation. The Lockheed Martin HALE-D airship is driven by two two-kilowatt electric motors and powered by thin-film solar cells and rechargeable lithium-ion batteries.    

The ultimate goal for the HAA is an airship that could station-keep at 65,000 feet for months at a time with large multi-mission payloads. The airship should also be capable of moving to other locations. It would be recoverable to the launch site so that the payloads could be changed and periodic maintenance performed.

ISIS Program

Although the HALE-D has yet to successfully demonstrate the HAA concept, another Lockheed Martin unit is already under contract to the Defense Advanced Research Projects Agency (DARPA) for an ambitious application of stratospheric airships. In April 2009, DARPA awarded a nearly $400 million contract to the Lockheed Martin Skunk Works and Raytheon to produce a radar surveillance platform. This is the Integrated Sensor Is Structure (ISIS) program in which a very large active-array dual-band radar will be part of the airship structure.

“The operational goal for ISIS is to look for airborne and ground-based targets and to communicate directly with the battlefield from a single antenna for up to ten years,” said Michael Wechsberg of Raytheon Space and Airborne Systems. From 70,000 feet, the ISIS airship “will have the ability to track the most advanced cruise missiles at 600 kilometers and dismounted enemy combatants at 300 kilometers,” according to Lockheed Martin. The early concept of integrating the active array into the airship’s surface area has been dropped. Still, the antenna must be very large to compensate for the relatively low power that will be available to it. Artists’ concepts show the radar occupying the entire central structure of a huge airship. For the ISIS demonstration, Lockheed Martin is building a one-third scale airship, which is due to fly in 2013.

Theoretically, operational airships developed from the ISIS concept could supplant and maybe even replace both the E-3 AEW and E-8 JSTARS radar surveillance aircraft. But there are major challenges, such as the further development of high strength-to-weight materials, regenerative fuel cells, lightweight antennas, calibration of the antennas and a high-bandwidth yet covert datalink.