X-Prize Implications
You might well ask why a blog devoted to energy issues would even mention something like the winning of the X-Prize, a $10 million dollar award put up by the X-Prize Foundation for the first privately built and run spacecraft to fly to an altitude of 100 kilometers above the earth twice within a set period. What could this possibly have to do with energy, even in the most far out sense? The answer relates to a technology that might be the best long-term alternative to fossil fuels or nuclear power: space-based solar power.

Solar power developers routinely confront two major hurdles. The first is overcoming the intermittent nature of their energy source, with its diurnal and weather-based fluctuations. The second is, to put it bluntly, the NIMBY factor. But there is an unspoken third hurdle that underlies both of the others, in the atmospheric attenuation of sunlight.

Because surface-based solar collectors sit under a blanket of atmosphere, with shifting sun angles, cloud cover and night, the amount of energy hitting a sqare meter of solar collector is roughly 1/10th of what is available in space. That necessitates building collectors that are much larger, or trying to improve the efficiency of the collector, to turn more of the energy it does receive into electricity. It also forces developers to provide for some form of backup power, either from the grid, or from batteries or other storage. A solar collector sitting in orbit can be positioned to receive essentially 100% of the available solar radiation, 24/7.

I don’t mean to trivialize the task of building orbital solar power satellites and transmitting power to the surface of the earth. NASA and private industry have spent a lot of time and effort understanding what this would entail, and creating design studies and computer models. But in the studies in which I was involved a few years ago, one of the central issues was always the cost of getting a kilogram of material into orbit. If you had a space launch capability that could routinely put large payloads in orbit at low cost (several orders of magnitude lower than today’s cost), then a solar power satellite might start to make commercial sense.

Of course, the Space Shuttle, as we have learned so painfully, cannot function as a low-cost, reliable space truck. Nor will its successor, which will probably be merely a personnel shuttle to serve the Space Station. That is why Spaceship One is so important. Even though it is only a sub-orbital craft—incapable of entering orbit around the earth—it represents a major milestone on the path toward a privately-financed, low-cost, routine launch capability, and thus towards the day when a solar power satellite can be considered on its own economic and technical merits.