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Modular SBSP illustration
Modular concepts like this one could reduce the costs and shorten the development schedules of space-based solar power systems, advocates argue. (credit: SpaceWorks Commercial)

Making the case, again, for space-based solar power

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Space-based solar power (SBSP) is one of those ideas that, on the surface, looks particularly attractive. Harnessing sunlight in space—where it’s not limited by the day-night cycle or weather, as on Earth—and beaming that energy to Earth could provide effectively limitless amounts of power to meet the growing needs of humanity without the resource limitations or environmental impacts of alternatives like fossil fuels. However, SBSP’s beauty may be only skin-deep: once you start to dig into the details, from the technical challenges of building massive structures in space to the costs of doing so, it’s easy to understand why the SBSP concept has made little progress since first conceived by Peter Glaser over four decades ago.

“Ultimately, it was the judgment of the Academy study that space solar power is technically feasible” and may be economically viable within 30 years, Mankins said.

However, a small element of the broader space community continues to restate the case for SBSP, seeking to leverage advances in various realms of technology to show that, with enough time and money, generating power in space will at least be feasible, and eventually economical. The latest effort to demonstrate the potential of SBSP is a new report by the International Academy of Astronautics (IAA), formally rolled out earlier this month at a press conference in Washington, DC. The report’s authors and other SBSP supporters hope that the report’s findings will trigger new interest in, and funding for, SBSP research.

“Ultimately, it was the judgment of the Academy study that space solar power is technically feasible, and there is a very reasonable prospect that it can be economically viable within the next one to three decades,” said John Mankins, who chaired the IAA study, at the November 14 press conference at the National Press Club.

Mankins hastened to add that although SBSP could be economically viable in that timeframe, the report does not guarantee that it will. “There’s still a lot of work to be done in terms of engineering research and development, and technology demonstrations, in order to validate the performance of these technologies in operational space solar power system concepts,” he said.

Those areas of technology development span a wide range of topics familiar to previous SBSP studies, from the in-space assembly of large structures to the conversion of sunlight into electrical power and its transmission to Earth. The biggest technological obstacles are not necessarily the best-known ones, though. Mankins noted that for one favored approach for an SBSP system, a “sandwich structure” of many small modular components that convert sunlight into microwave power, “the single biggest tall pole to an initial system is thermal”; that is, getting rid of the waste heat such a system would generate.

One of the biggest obstacles for SBSP has been, and remains, space transportation: the business case for these systems doesn’t close without the development of new, presumably reusable, launch systems which could launch payloads for much lower costs than existing expendable systems. The IAA report agrees that such transportation “is an enabling capability to the economic viability of space solar power” and while arguing that such systems “appear to be technically feasible during the coming 20–30 years”, admits that “the technologies required for this future space capability are not sufficiently mature for system development to begin at present.”

Mankins, though, argued that SBSP need not wait for the development of such systems before proceeding with the development of demonstration systems. A pilot SBSP system “could be done without the development of a new reusable launch system,” he said, instead using existing vehicles like the Delta IV Heavy, Falcon 9, or Falcon Heavy. Their launch costs on a per-kilogram basis “are low enough that you can do these demos successfully.” A successful pilot plant, he added, could demonstrate that there’s sufficient demand from full-scale SBSP systems to support the development of low-cost reusable launch systems required for those full-scale systems to be economically viable.

This is hardly the first report to suggest the need for additional studies of or development work on SBSP systems. So what’s different this time around?

The IAA report is vague about what a pilot plant might be like, other than it generate between about one and ten percent the power of a full-scale system. Mankins said that, in his opinion, a good pilot plant would have similar parameters to that proposed in a 2007 study on SBSP by the National Security Space Office (NSSO): it would take 10 years to develop, cost $10 billion, and generate 10 megawatts. (See “A renaissance for space solar power?”, The Space Review, August 13, 2007) “We actually feel that’s quite a tenable challenge,” he said. The power it generated would not be cheap, he admitted, but also would not be “astonishingly high”: between $1–5 per kilowatt-hour, compared to typical retail prices in the US today of about $0.10 per kilowatt-hour.

Much of the IAA report looks at more general and less controversial issues, including making the case that global society will require more energy over the next century and that existing energy sources, in particular fossil fuels like petroleum and coal, have environmental impacts, including climate change, that may become increasingly unacceptable. And its recommendations are not particularly controversial: additional technical and economic studies of SBSP concepts by commercial and government entities, including participation by non-space agencies and companies; work on policy and regulatory issues, such as the spectrum needed for wireless power transmission; and modestly suggesting that there was a role in future SBSP studies by international organizations like the IAA.

However, this is hardly the first report to suggest the need for additional studies of or development work on SBSP systems. When Mankins was at NASA in the late 1990s, he led the so-called “Fresh Look” studies of SBSP, the most thorough look at the concept since some of the original studies in the 1970s. The NSSO study in 2007 examined the potential use of SBSP to serve military needs, like powering remote bases, where cost was far less of a concern than for conventional commercial power application. Yet, NASA’s follow-up to the Fresh Look study, done in concert with the NSF, sputtered out after a few years, and the NSSO report’s call for Defense Department support for SBSP development has not been heeded (and, in fact, the NSSO itself no longer exists.) So what’s different this time around?

A big difference, Mankins argued, is the concept of modularity, which did not exist in previous architectures. In the Fresh Look study, he said, they could not get around, as systems were scaled up, the need to “fundamentally rearchitecture” the system. The use of modular architectures means that a single module could be developed and tested for on the order of tens of millions of dollars, then built in volume for pilot plants and, later, full-scale systems. “You don’t end up having to reengineer the whole thing just because you’re adding more modules,” he said. “These networked approaches really suggest a breakthrough is possible in terms of the schedule and, if the architecture is sufficiently modular, in terms of the cost.”

“I think it’s irrational to spend $300–400 million a year on fusion and nothing on space solar power,” said Hopkins.

While modularity may be a technical breakthrough, SBSP advocates have yet to find a policy or fiscal breakthrough: support from a government agency to fund some of the technology development work and other studies identified in the IAA report. As others have noted, SBSP rarely, if ever, enters the broader conversation about alternative energy technologies either in the public or private sectors, even in closely-related areas like terrestrial solar (see “Blinded by the light”, The Space Review, June 7, 2010).

That lack of support grates on some SBSP advocates. “I think it’s irrational to spend $300–400 million a year on fusion and nothing on space solar power,” said Mark Hopkins, CEO of the National Space Society (NSS), which organized the press conference. He was referring to the Department of Energy’s Fusion Energy Sciences program, which supports various fusion research projects, including US participation in the ITER experimental fusion reactor. “Space solar power is much closer in a technical sense to being realized than fusion,” he claimed. He suggested starting SBSP research at about $10 million a year, gradually increasing spending on it over time to at least the same levels as fusion.

Hopkins and Mankins both discussed at the press conference considerable international interest in SBSP, including work in Japan and, more recently, China. However, Mankins noted that future Japanese funding for SBSP may be uncertain as the country grapples with the cost of the cleanup of the nuclear reactor accident at Fukushima after March’s earthquake and tsunami, while Hopkins said that Chinese funding for SBSP work remains “under the radar”.

Missing from the rollout of the report was any strategy by the NSS or other organizations to raise awareness of SBSP and to win support for it from NASA, the DOE, or other agencies. It’s a task that, through no fault of their own, has become harder in recent weeks, both because of the prospects of significant automatic cuts in discretionary spending after the failure of the “supercommittee” to develop a deficit reduction plan, and the greater political scrutiny of solar and other DOE alternative energy programs in the wake of the bankruptcy of Solyndra, the terrestrial solar power company that was supported by over $500 million in federal loan guarantees. If it was tough raising support and funding before, it will be even harder in the near future with decreased budgets and increased skepticism.

The IAA report makes the case that space-based solar power remains a good idea, at least on paper. If it’s ever to be more than that, though, it will require not just technical and economic breakthroughs, but political ones as well.