May 1, 2009 The idea of replacing very expensive space based satellites and Aircraft mounted Airborne Warning And Control Systems (AWACS) with stationary platforms inside Earth's atmosphere has been floated for decades. Despite the fact that lighter-than-air vehicles or airships that could fulfill this role have been flying for over 300 years, the idea is only now getting off the ground. U.S. Defense contractor Lockheed Martin has been chosen by the Defense Advanced Research Projects Agency (DARPA) for a US$400 million contract to to design, build, test and fly a 1:3 scale model of an airship surveillance and telecommunications platform called the High Altitude Airship (HAA).

The HAA is an un-tethered, unmanned lighter-than-air vehicle that will operate above the jet stream (more than 70,000 feet / 21 km high) in a geostationary position. From that position, the autonomous flight test system will operate on station for 90 days and the airship will be able to survey a 600-mile (970 km) diameter area and millions of cubic miles of airspace to deliver telecommunications relay, weather data or surveillance. The full scale HAA will be able to stay aloft for up to 10 years.

A geostationary airship offers the same capabilities as a satellites but at a fraction of the cost (1 to 2 orders of magnitude less) and is also significantly less costly to deploy and operate and other airborne platforms such as AWACS and Joint Surveillance Target Attack Radar System (JSTARS).

The Airship operates in the stratosphere just barely within the outer limits of the earth's atmosphere. The geostationary position of 70,000 feet (21 km) has been selected because there are minimal wind conditions during a significant part of the year at this altitude and the air density is only five percent of that at the surface.

The HAA will be built using high-strength fabrics to minimize hull weight. Lift is provided by helium and leakage, as well as migration of air and water vapor into the helium enclosure, will be minimized by the envelope design. A 15kW thin-film solar array will generate all power required on-station and store it in a 40 kWh Li-ion battery for use by the payload (up to 50lbs) and the 2kW lightweight all-electric propulsion units.

The 500,000 ft³ (14,158.4 m³) airship will measure 240 ft long by 70 ft in diameter (73 x 21 meter) and will be built in the company’s Akron Airdock, which is 1,175 feet long, 325 feet wide and 211 feet high (358 x 99x 64 m). The building's height is equal to a 22-story building.

Paul Evans

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