Just consider the downside of satellites. The geostationary orbit alone now harbours thousands of new, unused and expired satellites that constitute an expensive band of clutter. Geostationary satellite channels suffer a transmission delay dictated by distance in excess of 0.3 of a second. In contrast, a North Atlantic optical fibre cable introduces a delay of only about three hundredths of a second. Large antennae and high transmitter powers and sensitive receivers are also required to overcome path loss and adverse weather.

Soon we will also have hundreds of low-cost, low-Earth orbit (LEO) non-synchronous satellites in orbits between 1,000km and 3,000km. Being low altitude they will allow the use of smaller antennae, lower power, and cruder receivers for hand-held mobile and portable applications. Of course, the much shorter transmission distances of low orbit will see delays more or less comparable to cables. But then again, they are not locked into a sustainable orbit and will fall out of the sky far more often than their geostationary counterparts. So a network of such satellites will require a continuous replacement programme.

A net result of all this should be more mobile communications capacity at the expense of an increasingly cluttered sky. Ultimately, the multi-layered orbits could constitute a threat and limitation to future space exploration, an orbital minefield in the making. But balloon technology offers an alternative and far cheaper solution.

Modern balloons are safe, reliable, inexpensive and capable of lifting substantial payloads to significant heights. A network of only four to six balloons hovering at 10km could service the whole of Britain to the extent that they could illuminate the Welsh and Scottish mountains and provide a universal service currently inaccessible to equatorial satellites. At lower altitudes more would be required of course, and perhaps 10 might be acceptable. Telephone, data, radio and TV access would be possible at low cost using microwave radio, possibly augmented by infrared optical beams. For some applications a metallised balloon might suffice as a passive reflector.

A further advantage, beyond the very low payload and launch costs, is the ease of platform access for equipment repairs and upgrades. So what are the disadvantages? There are only two: the tethering and/or positioning technology, and the threat to air traffic. A cable anchor to the ground is the most attractive as it could also act as both a signalling and a control medium. This would need to be clearly marked visually and for radar for obvious reasons.

There is, however, an alternative: tetherless positioning above the air lanes with robotic thrusters to hold a fixed position relative to the planet's surface. While this would necessitate a power plant, fuel, refuelling, and hot standby craft, it is not out of the question. All it needs is engineering.

Peter Cochrane holds the Collier Chair for the Public Understanding of Science & Technology at the University of Bristol. His home page is:
http://cochrane.org.uk