Bigger than the blimp
‘The concept is to have an airship that flies above 65,000 feet and is geostationary, which means it stays in the same position over the Earth,’ said Oleg Wasynczuk, a professor of electrical and computer engineering at Purdue who is leading the project with John Sullivan, a professor of aeronautics and astronautics.
Engineers are not yet certain how large the airship might be, but it may be as long as 300 metres, or around 900 feet - roughly four times the length of the Goodyear blimp. The airship will be powered by solar cells and an advanced fuel cell, and a customised control system will help keep it steady in high winds.
Because the unmanned ship might have to remain in flight for as long as a year at a time, it will be equipped with innovative power systems to provide electricity. The researchers plan to cover a portion of its skin with photovoltaic cells, which will provide electricity during the day to power the ship and also run equipment that turns water into hydrogen and oxygen. During the night, the hydrogen and oxygen would then be used to run a ‘regenerative fuel cell’, said Revankar. As the fuel cell generated electricity, it would produce water, which would be returned to the system to begin the cycle over again during daytime hours.
The researchers are also developing mathematical models to simulate the fuel cell's performance. ‘The fuel cell is going to be a very large system. It will generate 500 kilowatts, which is about 10 times as much electricity required for the average home,’ said Shripad Revankar, an associate professor of nuclear engineering who is heading the fuel cell portion of the work.
Researchers must simulate how the fuel cell would interact with the ship's various systems, including those for communications, surveillance and the electric motors for thrust. To do so, they are creating mathematical models so that they can predict the fuel cell's behaviour while it is interacting with the rest of the systems on the ship.
A major challenge will be finding materials for the airship's skin that are capable of withstanding the extreme ultraviolet radiation at such high altitudes for extended periods, Sullivan said. Another important factor is determining how the airship would react to changing temperatures as the sun rises and sets every day, heating and cooling the helium. The cyclic temperature changes will cause the ship to rise and fall in altitude.
The Purdue researchers are working with PC Krause and Associates, a company specializing in controls and simulations, located in the