Upwardly mobile

Two hundred airships will be launched into the stratosphere by 2000, the
Japanese government announced last month. Floating 20 kilometres above the
Earth, the 260-metre-long airships will be used like communications satellites,
principally for mobile phones
(Technology, 7 June 1997, p 22). They will be
one-tenth the price of satellites, and longer-lived. Their relatively low
altitude—the orbits of the lowest satellites are at least thirty times as
high—means that ground transmitters can be smaller.