Hokan Colting, founder of 21st Century Airships Inc., (check out the main page picture) is interviewed by New Scientist magazine about his spherical airship design and high altitude record for lighter-than-air manned airship operation.

What's the highest you've flown in it?

We took it up to 6234 metres (20,450 feet), which is the world record for airships. Traditional airships can only go up to about 1540 metres. After that, we descended, and sat in the cabin with the door open and had lunch.

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Who's going to want these airships?

High-altitude airships will be used for wireless telecommunications. For a signal to go from the ground to a geostationary satellite and down again, it's a round trip of 70,000 kilometres. Even at the speed of light, that still creates a delay. Or else you put up all these telephone towers everywhere.

A Georgia-based company, Techsphere Systems International LLC, has licensed the 21 Century Airships technology to build unmanned airships and expects to begin production in July 2004.. The spherical approach is seen as having advantages for high altitude loitering applications.

At sea level, the spherical airship will always have more drag than a traditional, cigar-shaped airship. However, for high altitude flying in an air density of approximately 6% that at sea level, the difference in drag between a spherical and a cigar-shaped airship is negligible. At an altitude of 65,000 ft., the spherical airship can achieve speeds exceeding 90 knots.

The AeroSphere has a dual envelope system. The outer envelope is load bearing and the inner envelope contains the lifting gas. When the inner envelope is fully expanded, the airship is at pressure altitude; meaning it cannot climb higher without valving some lifting gas. The air inside the envelope is slightly pressurized by electric blowers to maintain the airship's shape and resist deformation from wind loads.

For a high altitude airship, operating at 60 - 70,000 ft., the envelope must be sufficiently large enough to accommodate the 1,600 - 1,700 % lifting gas expansion. At lift-off, the inner envelope is only filled to 6% of its total volume (Fig. 2). The remaining 94% is filled with air at a slight (over) pressure.

During the climb to altitude, the lifting gas will expand, eventually occupying approximately 85% of the total volume (Fig. 3). At the designed operational altitude, the platform will have enough space to expand with temperature increase during daytime sun exposure.

The spherical airship has no balancing problems at any stage of “fullness”. The weight of the payload is at the center/bottom and the lift vector is directly above this with all the forces acting on the central vertical axis.

The AeroSphere is powered by a hybrid electric system. Thin film solar cells provide power during the daytime with turbo diesel engines that power back-up generators and a small compressor (engine is started with compressed air) for night time power. Very large, lightweight propellers provide sufficient thrust to keep the airship on station.

What is not clear is just how much energy do they think the airship will have to expend to maintain a fairly fixed position at high altitude. Can they move it up and down in altitude to catch winds blowing in different directions? Or can the solar cells power a propulsion system to maintain a stationary position?

Border surveillance and wireless communications are among the expected applications of this approach.

Our High Altitude Spherical Airship, the AeroSphere, is designed as a platform with significant payload capacity suitable for stationary, long endurance, unmanned operations at an altitude between 60,000’ and 70,000’MSL. This places them above the highest winds and weather systems and out of the way of commercial air traffic. And unlike satellites, these platforms can easily be retrieved and payload packages can be recovered and upgraded for further use.

Low and Mid Altitude Airships operate below 35,000'MSL. Depending on payload and application, these AeroSpheres will range in size from 60' to 140' in diameter. These lower level airships are ideal for military applications ranging from surveillance to troop support and homeland security applications such as border patrol and port security. These airships are designed for both manned and unmanned modes of operation.

The key attribute to effectively providing support for these applications is Long Endurance. The ability to loiter for days, weeks or even months at a time in an assigned position or "box". This is the advantage of Lighter Than Air (LTA) technology. To efficiently provide wireless communications to a very large geography. To provide the "unblinking stare" for surveillance and reconnaissance. To know when a suspected mobile chemical lab has moved from one area to another. This is the unique ability of the AeroSphere.

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The solution is AeroSphere High Altitude Airships. A single AeroSphere at an altitude of 20km can provide effective wireless coverage to an area the size of Virginia, Washington, D.C., West Virginia and Maryland. (see diagram to the left). This is the effective wireless foot print at a 5 to 90 degree angle of elevation. Attenuation from weather is also a major consideration in building tower based networks. Due to the angle of elevation to the AeroSphere, signals will experience far less rain attenuation as compared to terrestrial networks.

If this type of airship can put an end to cell phone cut-offs I for one will be very grateful. I am currently averaging one cut-off phone conversation a day from someone on a cell phone who is either moving or in an area with poor coverage.