A recent re-assessment of space solar power credibly suggests that a realistic construction pathway and business case may be feasible for this promising technology. This could be a big deal because of space solar power's potential:

The basic idea is very straightforward: place very large solar arrays into continuously and intensely sunlit Earth orbit (1,366 watts/m2), collect gigawatts of electrical energy, electromagnetically beam it to Earth, and receive it on the surface for use either as baseload power via direct connection to the existing electrical grid, conversion into manufactured synthetic hydrocarbon fuels, or as low-intensity broadcast power beamed directly to consumers. A single kilometer-wide band of geosynchronous earth orbit experiences enough solar flux in one year to nearly equal the amount of energy contained within all known recoverable conventional oil reserves on Earth today...

Co-ordinated by the U.S. National Security Space Office Advanced Concepts Office ("Dreamworks"), the assessment is clear that major technical and economic hurdles must be overcome before a full-scale investment decision, but also makes a convincing case for doing a follow-on architecture study and proof-of-concept demonstration project. Compared to the trillion-dollar market potential, the funds required would be minuscule.

The study itself was done using an interesting collaborative format:

Without the time or funds to contract for a traditional architecture study, Dreamworks turned to an innovative solution: the creation on April 21, 2007, of an open source, internet-based, interactive collaboration forum aimed at gathering the world’s SBSP experts into one particular cyberspace. Discussion grew immediately and exponentially, such that there are now 170 active contributors as of the release of this report—this study approach was an unequivocal success and should serve as a model for DoD when considering other study topics.

...In support of the study group’s efforts, the Space Frontier Foundation also established a parallel, open‐access website at http://spacesolarpower.wordpress.com/ to solicit inputs from the public at large, many of which possessed significant credentials toward answering the question of whether the U.S. and partners can enable the development of SBSP by mid‐century.

While not a substitute for the rigor and technical depth of a full architecture study, this dual-track collaborative structure "was an unequivocal success" in tapping into a diverse range of expertise and interests to rapidly do initial feasibility assessment. What other big challenges could this approach be tried on?