As serendipity would have it, there is a mini-flood of sci-tech news concerning the use of light (lasers mostly) just when SciTechStory introduces a new impact area – photonics – the study of energy in the bandwidth of light. Here are the two most recent posts:

Transformation optics: The light fantastic
Optogenetics: Controlling live neurons with light

Now here’s another: Using lasers to remotely power machines. Some of this moves into territory that was exclusively science fiction only a few decades ago. For example, using laser beams to provide the energy for ‘space elevators.’ This is the idea of sending elevators up and down cables attached to the Earth at one end and to satellites in space – cables kept aloft by the centrifugal force of the rotating Earth. The original idea came from a proto-scientific crank case by the name of Konstantin Tsiolkovsky, and was made popular decades ago by Arthur Clarke (The Fountains of Paradise) and others.

The American space agency, NASA, has periodically visited the idea but there have always been technical barriers such as the weight of a cable strong enough to withstand the strain and the problem of supplying energy to move the elevator. Like any ‘out there’ technology, ideas came and went over the decades, but there has always been the sense that ‘one of these days’ the appropriate technology would arrive. Part of this technology may come from lasers.

Of course, lasers are not new technology, but with each decade there are more kinds of lasers, more powerful lasers and more controllable lasers. It’s the last two improvements that apply in this case. It’s generally been true that the more powerful the laser, the more difficult it was to control, that is, aim the laser beam with precision. In the last ten years or so lasers have improved from about 40% efficiency (use of energy) to over 60% and still climbing, which means the beam can transmit more energy – more power. At the same time techniques such as using adjustable mirrors and fiber optic strands are now used to concentrate the laser beam, which is another way of delivering more power to a specific spot.

The final piece of controlling a laser beam is the continuing evolution of computer tracking and coordinating software. This has been applied to very small (as in micro-scale) moving objects, which is what optogenetics can achieve; and it also now applied to targeting small receptor panels on objects in space. That is how, in the probably not too distant future, laser light can be used to power space elevators (or other orbiting objects).

How far in the future? The laser technology is ‘almost there,’ but the laser system still needs to deliver more power to a smaller receptor than can be achieved at the moment. The nanotechnology behind creating an appropriately strong but light cable is ‘almost there’ but tensile strength and weight are still a factor. Then there is a matter of cost. The technologies not only have to meet the required specifications, they have to be affordable. This is probably not a matter of being inexpensive, as in mass production, but – as a guess – something in the single digit billions (dollars). So, how far in the future?…A decade, maybe two – and the economics must be right.

The economics are the driving force (as usual), but in this case it isn’t just the cost of building a space elevator. This has to be weighed against the importance of lowering the cost to deliver goods and probably people into geosynchronous orbit. Halving the cost, which now pegged around $20,000 per kilo, might make all the difference to the growth of space industry and exploration. That’s something space elevators might achieve and without the environmental cost of the current rocket-based approach.