Earlier this week a new alliance was announced to promote the exploitation of solar power from space. The Space Solar Alliance for Future Energy (SSAFE,) formed by space advocacy and research organizations, is basing its initial efforts on a just-released study by the National Space Security Office . Collecting solar power in space, where it is available 24/7 and is not attenuated by atmosphere or clouds, remains one of my favorite long-term energy solutions, on a par with nuclear fusion. It has a major advantage over fusion, however. While both offer inexhaustible sources of energy, space solar power (SSP) requires no scientific breakthroughs. Despite that, its engineering and cost challenges make it unlikely that SSP could contribute significantly to terrestrial energy much before 2020.
If you're not familiar with the concepts for capturing solar power from orbit and beaming it to earth--ideas that have been refined significantly since they were first conceived in the 1960s and '70s--I encourage you to download SSAFE's feasibility study. It provides a good overview of the technology and many of the financial, logistical, diplomatic and other factors that must be addressed. Having been personally involved in the late-1990s NASA studies referenced in the document, I must say that I don't find the update to be quite as novel as the report suggests, when compared with the concepts and constraints that we examined 10 years ago. But as it points out, the energy and security context for considering this option have changed tremendously, and that may be enough to alter the ultimate conclusions about whether to proceed with such a large-scale space endeavor.
When I served on the economic evaluation team reviewing the 1990s NASA effort, two obstacles to the commerciality of SSP loomed large. In that period, ground-based power costs were low and falling--and most of the experts and economists we consulted expected that trend to continue. The high cost of power from space appeared difficult to justify outside of a few niche applications. Compounding that challenge, the construction of a fleet of power satellites capable of producing hundreds or thousands of Megawatts of electricity each would require a launch capability far beyond that of the quartet of Space Shuttles--which ultimately proved barely adequate for the current Space Station--or of a second-generation shuttle. But SSP was the only application large enough to justify building such a capability, short of a major effort to colonize or industrialize earth-orbital space. Chicken and egg.
As NASA foresaw in the late '90s, advances in technology have made it possible to contemplate an SSP design that requires fewer, smaller payloads and relies almost entirely on robotic assembly. That will reduce the number of launches and virtually eliminate the need for a parallel ramp-up in manned space activities, thus improving the economics. It's not clear from my perusal of the report whether this new configuration could be placed in orbit by existing commercial launch capacity. Even if it could, the process would be lengthy and very expensive.
And although I'm intrigued by some of the novel applications for power from space described in the report, including chemical synthesis of carbon-neutral hydrocarbons, most encounter another hurdle we identified a decade ago. While there are certainly lots of cool things that you could do with power from space, there are very few applications that actually require it. I routinely receive comments from readers of this blog who are equally keen on hydrocarbon synthesis based on nuclear power, which would almost certainly be more economical that the SSP-driven version.
Finally, although our perspective on national security and its energy security dimensions has expanded since 9/11, the potential linkage of SSP to military applications raises the prospect of international opposition to a project that could probably only proceed as an international initiative. I appreciate the benefits of having an "anchor customer" that puts a high premium on the ability to deliver power to any point on the planet. The advantages for the military would also be significant, given the expense and risk it incurs delivering energy to the "battlespace." However, the basic architecture of SSP will inevitably raise concerns about its inherent military potential, whether that potential is real or merely perceived. This is an issue that would have to be navigated very cautiously, particularly since other nations with anti-satellite capabilities might regard an SSP beaming power to a war zone as a legitimate military target.
I will follow SSAFE's progress with great interest. Space solar power has enormous potential to provide useful increments of zero-emissions energy as either a reliable baseload or as a sequentially-shifting peak supply across the globe. SSP will also benefit from the steady improvements in photovoltaic technology that are making ground-based solar more competitive. It's not a short-term solution, however, and its development still faces many technical, political and permitting challenges. SSP is a valuable future option, and we'd be wise to invest to increase the value of that option and make it easier to exercise, should we ultimately choose to do so.