How it could
work
The report sketches out how a space-based solar
power system could work:
 | A network of satellites would be constructed in space with arrays of lightweight mirrors extending for several miles (kilometers) on each side. |
| Those mirrors would focus sunlight on solar cells, generating electrical power. The electricity would be converted into microwaves suitable for transmitting through Earth's atmosphere, at frequencies of 2.45 or 5.8 GHz. |
| The microwaves would be directed down to antenna arrays on Earth, as a beam of radiation about one-sixth as intense as noon sunlight. The antennas would convert the radiation back into electricity for distribution via conventional grids. |
The commercial systems discussed in the past would deliver 5 to 10 gigawatts of power. In contrast, the Pentagon study calls for military systems providing 5 to 50 megawatts of continuous power é roughly a thousandth as much.
The report's roadmap calls for ground-based technology development over the next few years, leading up to a demonstration in low Earth orbit in the 2012-2013 time frame, and in geosynchronous orbit by 2017. However, the report makes no commitment for funding such a demonstration. Smith said that would be up to other agencies é such as the Pentagon's own Defense Advanced Research Projects Agency, or NASA, or the proposed Advanced Research Projects Energy.
Damphousse said the program could use an "incremental approach," starting with experiments to transmit power wirelessly between ground stations placed miles apart. "If you can do that, then you're well on your way to proving you can do it from space," he said.
A follow-up experiment could try transmitting power from the international space station to Earth. "I actually met with a bunch of folks at NASA Ames last week ... and they warmed to the idea immediately," Damphousse said.
Damphousse said the geosynchronous system would require an investment on the order of $10 billion, but would serve as a proof of concept for commercial space power systems.
Smith said such systems could eventually deliver electricity to places that lack the infrastructure for traditional power transmission grids, and turn the decades-old dream of wireless power into reality. "It's using space for an actual tradeable commodity é not for a rover on Mars, which is also necessary é but actually delivering a commodity that can be given to anybody in the world," he said.
Time for a
reality check
In conjunction with the Pentagon report's
release, 13 space advocacy and research
organizations announced the formation of the
Space
Solar Alliance for Future Energy, which
pledged to push for implementation of the space
power plan.
"While the technical challenges are real, significant investment now can build space solar Power into the ultimate energy source: clean, green, renewable, and capable of providing the vast amounts of power that the world will need. Congress, federal agencies and the business community should begin that investment immediately,é Mark Hopkins, senior vice president of the National Space Society, said in a written statement.
|
"It appears that technological challenges are closing rapidly and the business case for creating SBSP is improving with each passing year," Rouge said in his foreword to the report. "Still absent, however, is an appropriate catalyst to stimulate the various interested parties toward actually developing a SBSP capability."
The Solar Electric Power Association's Taylor, who advises utilities and other organizations on trends in terrestrial solar power, said the space option "is not something that's on the current solar industry's radar."
He told msnbc.com that putting a large power-generating system in space would pose huge technical challenges é and the potential payoff would have to be similarly huge to justify the risk and expense.
"I'm not sure there'd be a great need to move into space unless it had some exponential cost improvement," Taylor said. "It can't be just a marginal improvement."
What is to be
done?
Smith agreed
that the hurdles were high. "You put the study
out, you spend a couple of weeks getting
comments, you step back and take a breath, then
you get busy," he said. "We didn't try to candy-coat
this. This is going to be a hard, hard, hard,
hard problem."
No. 1 on his list was reducing the cost of sending payloads into geosynchronous orbit é a cost that is currently estimated at $10,000 per pound or more. "We have got to solve the reusable rocket and space plane problems immediately," Smith said. "It's time to stop just talking about it."
Constellation Services International's Miller said "the business case doesn't close by just standing aside and doing laissez-faire." He called attention to three recommendations listed in the Pentagon report:
| The Defense Department should analyze its long-term requirements for energy delivery to warfighters, and evaluate whether there's an appropriate way to sign up as an anchor customer. The report cited the example of the National Geospatial-Intelligence Agency's status as an anchor customer for the commercial NextView satellite program. |
| Government incentives for carbon-neutral energy technologies é such as carbon/pollution credits and offsets as well as loan guarantees é should be extended to space power programs as well. The loan guarantees could be modeled on the program currently provided to the nuclear power industry. |
| Legislation should be enacted to create transferable investment tax credits for private investments in reusable space transportation systems, as well as in commercial space infrastructure such as orbital fuel depots and assembly platforms. |
Miller noted that the energy market amounts to $1 trillion a year market, and said the future payoff could be at least as huge as the present challenges.
"If space solar power takes off, everything that came before é Apollo, the shuttle, the station, all together é will look like a college science project," Miller told msnbc.com. "It's that much bigger."