The communications-satellite industry, arguably the only space industry that actually makes any money, may find itself usurped by an unlikely technology that is a lot more down to earth.
Next month Sanswire Networks, a company based in Atlanta, Georgia, is planning to launch the first airship satellite, or “stratellite”. Floating in the stratosphere at an altitude of about 20km (13 miles), the airship will behave just like a geostationary satellite, hovering over a particular spot and relaying radio signals to and from the ground. Such airships will, however, be much cheaper to launch and maintain than satellites—and can do things that satellites cannot.
Each 75-metre-long airship will be controlled autonomously, and will contain nearly 37,000 cubic metres of helium to keep it and its 1.4-tonne payload aloft, says Michael Molen, Sanswire’s chief executive. At such high altitude, above the jet stream, the reduced air density means that the wind will be about 20 times weaker than at ground level, enabling the airship’s solar-powered electric motors to keep it stationary with very little effort. The craft’s aerodynamic shape not only reduces drag but also generates lift when facing into the wind, says Mr Molen.
Like satellites, these airships will be able to provide wide-area mobile-telephone coverage, paging and other communications services. The company is most excited by the prospect of being able to provide wireless broadband coverage, akin to Wi-Fi, over large areas. A single airship could, says Mr Molen, potentially provide coverage over an area of nearly 800,000 square kilometres, or about the size of Texas. It should thus be possible to create “hotzones” of coverage encapsulating entire cities and their surrounding countryside, rather than the smaller “hotspots” of Wi-Fi coverage found in airports and coffee shops.
Standard Wi-Fi technology is, however, intended only for short-range communications. Beaming signals to and from an airship requires a special antenna. But the stratellite could be used to provide a high-speed connection to an access point for a home or office, which could then connect to nearby devices using Wi-Fi. The stratellite service would, in short, offer an alternative to cable and digital subscriber-line (DSL) broadband links. It would also be useful in countries with little or no network infrastructure, notes Ron Hochstetler, the chairman of the Airship Working Group at America’s Federal Aviation Administration.
Airships are, he says, the only aviation technology that has not been fully exploited, which is why America’s military is evaluating them for heavy-lifting and transport duties.
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