Machine Design

Blimp to hover at 65,000 ft

Researchers from Purdue University are working on a high-altitude, helium-filled airship capable of hovering over the same spot for up to a year.

Researchers from Purdue's School of Aeronautics work with a 19-ft-long model to develop the aerodynamic design and control system for a new high-altitude airship. To keep the craft stationary it will have an automated system of electric motors to steady the airship in the windy environment. From left are graduate student Bryan Redman, Professor John Sullivan, and graduate student Seth McDonald.

About 10 researchers are involved in developing the airship, which could have applications for surveillance, homeland security, missile defense, and weather forecasting. The U.S. Air Force Research Laboratory is funding the research.

"The idea is to build an airship that flies above 65,000 ft and is geostationary, staying in the same position over the Earth," says Oleg Wasynczuk, professor of electrical and computer engineering at Purdue. Wasynczuk's team is working on solar cells and an advanced fuel cell to power the craft. Computer simulations will help determine a design and control system to steady the airship amid high winds.

The researchers are also developing mathematical models to simulate fuel-cell performance. "No such fuel cell has been developed for space applications," says Shripad Revankar, an associate professor of nuclear engineering. The fuel cell will generate 500 kW — about 10 X the electricity required for the average home.

The airship will fly well above commercial aircraft, which cruise as high as 40,000 ft (conventional blimps reach about 5,000 ft). At this altitude it will be better than orbiting satellites for surveillance. And the ship could hover over one location anywhere in the world, whereas satellites are geostationary only over the equator.

Photovoltaic cells will cover a portion of the ship's skin. Electricity from the cells will power the ship in daylight and also run equipment that turns water into hydrogen and oxygen. At night, the hydrogen and oxygen will power the regenerative fuel cell, says Revankar. As the fuel cell generates electricity, it produces water which returns to the system, repeating the cycle the next day. Researchers must simulate how the fuel cell will interact with the ship's other systems, including those for communications, surveillance, and the electric motor that provides thrust.

The airship may be as long as 300 m (about 900 ft) — roughly four times the length of the Goodyear blimp. A major challenge will be in finding materials for the airship's skin that can withstand the extreme ultraviolet radiation at high altitudes for extended periods, says Sullivan. The team must also deal with the airship's rising and falling as a result of daily temperatures changes.

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