WASHINGTON -- Two new studies looking at the feasibility of space-based solar power - orbiting satellites that would serve as high-tech space dams - suggest the concept shouldn't be readily dismissed and could generate both Earth-bound and space-based benefits.
These "powersats" would catch the flood of energy flowing from the Sun and then pump it to Earth via laser or microwave beam. On earth it would be converted to electricity and fed into power grids to be tapped by terrestrial customers.
The thought of beaming energy to Earth via satellite was first brought to light in the late 1960s by Peter Glaser, a technologist at Arthur D. Little in Cambridge, Massachusetts. Into the 1970s and 1980s, the challenges of Space Solar Power (SSP) were reviewed numerous times. NASA, the Department of Energy, other government, industry and private groups have given the concept the once-over.
A swarm of unknowns and criticisms always fly in tight formation around the prospect of energy-beaming satellites actually having any economic benefit to Earth.Among them: The size, complexity, and cost of an SSP undertaking are daunting challenges. International legal, political, and social acceptability issues abound. Health or environmental hazards from laser or microwave beams broadcast from space appear worrisome. Additionally, in the battle of energy market forces on Earth, any SSP constellation may prove far too costly to be worth metering.
In 1995, NASA embarked on what's tagged as a Fresh Look study. SSP feasibility, technologies, costs, markets, and international public attitudes were addressed. In general, NASA found that the march of technology and America's overall space prowess has re-energized the case for SSP. NASA did point out, however, that launch cost to orbit remains far too high - but that this problem was being attacked.
Investment strategy
For the last few years, interest in SSP has grown, not only at NASA, but also in the U.S. Congress and the White House Office of Management and Budget. For its part, the space agency has scripted a research and technology, as well as investment roadmap. This SSP stepping stone approach would enhance other space, military, and commercial applications.
A special study group of the National Research Council (NRC) has taken a new look at NASA's current SSP efforts. Their findings are in the NRC report: Laying the Foundation for Space Solar Power - An Assessment of NASA's Space Solar Power Investment Strategy.
Richard Schwartz, dean of the Schools of Engineering at Purdue University in West Lafayette, Indiana, chaired the 9-person NRC panel.
While not advocating or discouraging SSP, the advisory team said "it recognizes that significant changes have occurred since 1979 that might make it worthwhile for the United States to invest in either SSP or its component technologies." The study urges a sharper look at perceived and/or actual environmental and health risks that SSP might involve.
The NRC study group singled out several technological advances relevant to SSP:
- Improvements have been seen in efficiency of solar cells and production of lightweight, solar-cell laden panels;
- Wireless power transmission tests on Earth is progressing, specifically in Japan and Canada;
- Robotics, viewed as essential to SSP on-orbit assembly, has shown substantial improvements in manipulators, machine vision systems, hand-eye coordination, task planning, and reasoning; and
- Advanced composites are in wider use, and digital control systems are now state of the art - both developments useful in building an SSP.
ISS test platform
Overall, the NRC experts gave NASA's SSP approach a thumbs-up. The space agency's current work is directed at technical areas "that have important commercial, civil, and military applications for the nation." A top recommendation is that industry experts, academia, and officials from other government agencies -- such as the Department of Energy, Defense Department, and the National Reconnaissance Organization -- should be engaged in charting SSP activities, along with NASA.
The panel said that significant breakthroughs are required to achieve the final goal of SSP cranking out cost-competitive terrestrial power. The ultimate success of the terrestrial power application of powering-beaming satellites critically depends on "dramatic reductions" in the cost of transportation from Earth to geosynchronous orbit, the group reported.
Furthermore, the SSP reviewers call for ground demonstrations of point-to-point wireless power transmission. NASA should study the desirability of ground-to-space and space-to-space demonstrations. In this area, the International Space Station could act as a platform to test out SSP-related hardware, the study group said.
Energy as hope
In summary, the NRC panel members noted that for any SSP program to churn out commercially competitive terrestrial electric power, breakthrough technologies are required.
That being said, even if the ultimate goal of supplying competitive energy is not attained, the experts added: "…the technology investments proposed will have many collateral benefits for nearer-term, less-cost-sensitive space applications and for non-space use of technology advances."
Hubert Davis, a committee member on the NRC study, sees SSP as perhaps the right technology for today. Throughout the 1970s, he managed future programs for the NASA Johnson Space Center in Houston, Texas, and is now an independent aerospace consultant.
"In looking at our current world situation, I believe that what is most needed is hope. Power from space may be one of the best means for us to offer that hope," Davis told SPACE.com.
Davis said that an exploratory research, development and demonstration program for power from space is needed. It would be accompanied by a major international aid effort using terrestrial photovoltaics. In areas where no power exists, village "life support systems" can be established to provide potable water, lights, modern communications, refrigeration, information, and perhaps a few sewing machines, he said."These complementary steps may buy us the time we need to fulfill this new hope…for everyone," Davis said.In-orbit power plug
Following on the heels of the NRC's new look at SSP is an assessment completed by Resources for the Future (RFF) a Washington-based group that studies energy and environmental policy. It focuses on off-planet uses of an in-orbit "power plug", or as some label it, a "solar array on steroids." The idea is to have a filler-up facility for electrically hungry satellites, observatories, space platforms and the like.
That study is titled: An Economic Assessment of Space Solar Power as a Source of Electricity for Space-Based Activities. RFF's Molly Macauley and James Davis of The Aerospace Corporation authored the piece.
They observe that customers of a future SSP station could be many. Commercial telecommunications and remote sensing spacecraft, governmental research and defense satellites, space manufacturing facilities, as well as space travel and tourism industries could draw energy from such a station. There is a potentially large market that might benefit from this pay for power approach.
Another attractiveness of a space-based power station is leaving heavy solar panels back on Earth. Less massive spacecraft would be cheaper to orbit. That also means more science gear could be crammed onboard a satellite.
"Our study argues that we could do testing and demonstrations of in-space power sooner than for terrestrial power," Macauley told SPACE.com. The researcher was also a member of the NRC study on SSP.
Show me the energy
Macauley and Davis surveyed satellite designers and operators, gleaning insight about the value of having an SSP "power depot" in space. Whisking watts of power through space to run commercial geostationary satellites looks like a very lucrative and large market, they report.
On the other hand, while the willingness of potential customers to adopt a new power technology like SSP is promising, flight testing the idea would help boost adoption of the in-space energy idea. Early on, supplying power from an SSP could gain greater acceptance as a supplement, rather than a substitute for, an existing power system on a spacecraft, Macauley and Davis note.
Macauley said that in future years the space-based power market could be really big in dollar terms. Still to be determined is where to place an SSP, or whether or not there's need for a constellation of SSP satellites.
"Given our estimate of the market, can SSP designers create an SSP that's financially attractive? We also realize that other technological innovation in spacecraft power is proceeding apace with SSP," Macauley said. "So SSP advocates need to 'look over their shoulders' to stay ahead of those innovations and to capitalize on those that are complementary with SSP," she said.
"The ownership and financing of SSP may be handled as a commercial venture," Macauley and Davis report, "perhaps in partnership with government during initial operation but then becoming a commercial wholesale cooperative."
Once an SSP is fully deployed, the private sector is likely to be a far more efficient operator of the power plug in space, the researchers said.
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