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Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
High-altitude airship concept design nears completion
Keywords Lockheed Martin, Airships
Airship enthusiasts will be interested to hear that Lockheed Martin Naval Electronics & Surveillance Systems-Akron, a unit of Lockheed Martin (NYSE: UCT), with its partners - Stratcom International and others - have developed an unmanned lighter-than-air vehicle that would operate above the jet stream and above severe weather in a geostationary position to serve as a telecommunications relay, a weather observer, or a peace keeper from its over-the-horizon perch.
This updated concept of a tried and proven technology takes lighter-than air vehicles beyond the surface exclamations of: "Look, there's the Goodyear blimp." As a matter of fact, the Akron, Ohio, Lockheed Martin business unit supports the tire company's blimp fleet as the FAA certificated manufacturer and maintenance provider.
Now, though, things have changed. Lighter-than-air vehicles operating at altitudes of 21 kilometers (70,000 feet) are nearing a reality thanks in large measure to the technical know-how of Lockheed Martin Naval Electronics & Surveillance Systems-Akron and the convictions of Stratcom President Lt.-Gen. James A. Abrahamson, USAF (retired), and other members of its stratospheric airship industrial team.
All vital technologies have been evaluated individually during the recently concluded concept feasibility phase, which began in October 1998, and are ready for integration into a demonstration vehicle. "The evolution of the design over this period has illustrated a host of design, operational, and manufacturing issues that are significantly different than the issues resulting from development of fixed-wing aircraft or even a conventional LTA vehicle", Business Development director Ron G.E. Browning said.
"We have tackled and solved some of the more significant issues that deal with maintaining on-station position, and operation over very long times (months rather than days or hours). We are currently developing the operational procedures necessary in this upper atmospheric region," Browning added.
Maintaining geostationary position over long periods requires a detailed understanding of the environment at 21km. This altitude was chosen because of its minimal wind conditions during a significant part of the year. Wind profiles tend to reduce to a minimum a short distance above the jet stream. However, long-term, reliable and continuous data on winds and turbulence at this altitude are not available for the entire earth's surface. Therefore, variable winds and turbulence, even though the air density is only 5 percent of that at the surface, could still place severe demands on propulsion, control and navigation systems.
Buoyant vehicles require periodic checks on the helium purity. This is done frequently with blinks. For the vehicle operating at 21km, the design has taken into account leakage of helium as well as migration of air and water vapour into the helium enclosure. Degradation of buoyant lift will be minimised by envelope design.
Since it is not practical to carry fuel aloft in a long-endurance buoyant vehicle, all power must be generated on station. This includes payload and propulsive power. A combination of photovoltaic (PV) and fuel cell systems probably will be used to provide the multiple kilowatts of power necessary for these functions. The PV and regenerative fuel cell technologies required by the vehicle are being developed based on work at NASA-Glenn in Cleveland and NASA-Dryden at Edwards AFB.
Lockheed Martin believes that its experience with the certification of the GZ-22 airship with the FAA allows it to understand and address the concerns of flight through controlled airspace, especially with an unmanned airship. Safety of flight issues, operation of an unmanned vehicle, and operation over populated areas are all concerns that it has addressed during the design evolution.
While most of the issues noted are not unique to special aircraft designers, it is the combination of these factors along with the long endurance that makes the design problem a difficult one.
"We are confident that our design concept meets or exceeds all requirements, both environmental and operational. The next task - and the real challenge - is to fabricate a prototype and to fly it to prove that the detailed engineering design is viable," Browning said.
The vehicle might be built in the company's Akron Airdock, which is 1,175 feet long, 325 feet wide and 211 feet high. Its height is said to be equal to a 22-storey building.
Lockheed Martin NE&SS-Akron received its first production contract for a lighter-than-air vehicle, the rigid USS Akron airship, in 1928 from the US Navy. Since that time, the Lockheed Martin unit has built more than 300 airships and several thousand aerostats.
Details available from: Lockheed Martin Naval Electronics & Surveillance Systems-Akron. Tel: +1 330 796 8458.