Solar Power Satellite

Artist's rendition of a proposed Boeing Sun Tower satellite

Throughout the ages the light of the sun has fueled photosynthesis, freeing oxygen and providing food for the animal kingdom. It supplies the light to grow trees -- bringing us wood. Its heat evaporates the oceans to bring the rains that form our rivers and lakes. It causes the winds to blow and brings us warmth and comfort. It took uncounted millions of years for the sun working with the earth to create the coal, oil, and gas we are burning so recklessly today.
-- Ralph Nansen (retired Boeing scientist), SUN POWER: The Global Solution for the Coming Energy Crisis, Copyright 1995.

During 1982, Boeing designed a solar power satellite system that could supply most of the country at the time with electricity. The energy crisis of the late 1970s had inspired scientists at U.S. Department of Energy and NASA to re-examine the feasibility of solar power satellites based on the Space Solar Power concept, developed in the late 1960s by Dr. Peter Glaser. DOE and NASA subsequently organized the Satellite Power System Concept Development and Evaluation Program, and The Boeing Company and its heritage company, Rockwell International, led these early efforts. Rockwell won the study contract issued by the Marshall Space Flight Center, and Boeing won the contract with the Johnson Space Center.

In 1977, the Air Force Concentrating Photovoltaic Array study program conducted by Rockwell International concluded that solar concentrator arrays can survive the tough environments of outer space. Rockwell developed a preliminary design for a hardened solar concentrator. Rockwell also studied a way to use mirrors that concentrated the sunlight in a solar furnace to heat fluid, powering electricity-generating turbine engines. Involved in the Rockwell studies were engineers who carried their expertise with them when the company's space systems became part of Boeing in 1996. Later studies showed that silicon solar cells had a higher life expectancy than the thermal engine system, so the Boeing solar power satellite became the system of choice.

The Boeing solar power satellite would be a space platform the size of a small city. Deployed some 22,000 miles above the equator in geosynchronous Earth orbit (GEO), these satellite platforms would carry billions of silicon solar cells that would transform sunlight directly into electrical energy transmitted to Earth as microwaves through antennas. Rectifying antennas on the ground would convert the microwaves to direct-current electricity, which would be fed into the nation's power lines. A three-year evaluation study conducted by the DOE and NASA concluded that there were no known insurmountable technical, environmental or economic issues that should stop the development of the solar power satellite. Boeing had already developed solar power technology for the Lunar Orbiter, the flying photographic laboratory that encircled the moon in 1966 and took pictures of 90 percent of the lunar surface.

The Boeing solar power satellites could be constructed either in low Earth orbit for later shipment to the higher geosynchronous orbit or constructed directly at the higher orbit. Large space freighters, known as heavy-lift launch vehicles, would carry out-sized cargo pallets into low Earth orbit, where these pallets would be deposited and directed to docking stations at a space construction base. A modified Space Shuttle Orbiter could carry the personnel needed on the orbiting construction site (much as the International Space Station is constructed today).

The early studies indicated that the revenue from one solar power satellite, producing 10,000 megawatts of electricity sold at a rate of 40 mills per kilowatt hour, would produce $105 billion in 30 years. Forty-five satellites would produce more than $4.7 trillion, less than the cost of electricity generated by the oil-burning electricity generation plants. Solar power satellites, a Boeing press release pointed out in 1982, might be expensive to bring on line but would not be dependent on fuel costs. The sun's rays are free.

Boeing asked Congress to embark on a carefully phased plan that would progress from concept definition to technology verification to subscale demonstration. At the time, the greatest apparent stumbling block seemed to be political rather than technological. NASA's first priority was space rather than energy. The Department of Energy was not involved with research involving space. By the 1990s, when the continued conflicts around the world's oil-producing countries highlighted the need for new sources of energy, strong advocates for solar power satellites were in the Department of Defense. Using fossil fuels to power military bases and power trucks and airplanes was becoming increasingly expensive, so reducing DOD energy costs would contribute to national security.

In 1995, NASA began a "Fresh Look" study of space solar power techniques and concepts; in 1998, Congress authorized modest funding for further concept definition and technology development. The future of sun power brightened again during the energy crisis of 2007, when the National Security Space Office of the U.S. Department of Defense formed a study group of 13 leading research organizations and space advocacy groups. The group recommended that space-based solar power receive substantial national investment as a way to meet the country's future energy needs. The Space Solar Alliance for Future Energy formed to advocate investment in space-based solar power technologies to address the planet's future energy needs. In October 2008, the Air Force Research Laboratory sponsored a workshop on "The State of Space Solar Power Technology" to examine ongoing research into a space-centric, beamed-power energy system.

By 2008, the Boeing team working on solar power satellites had 30 years experience. Boeing scientists proposed and managed a half-dozen related contracts for NASA and produced about a dozen related publications. These activities included a conceptual design of a robotically constructed GEO satellite and work on smaller-scale, laser-photovoltaic satellites and transmission systems, which used receivers on Earth to produce solar-photovoltaic power. They reworked the Lunar Rover still on Earth to see if a laser-powered Lunar Rover, using wireless power transmission, could reach permanently shadowed lunar polar areas that may contain ice, and they studied the construction of a large solar power satellite to produce cryogenic propellants from water. Boeing scientists also looked at ways a space colony on the moon could find, shape and transport the materials to build the huge satellites more economically than by building them in space, which required launching space solar power satellite components from Earth. They led a study on solar power satellites presented to the National Security Space Office, and they participated in a NASA/DOD study of options for a near-term demonstration of space solar power technology in low Earth orbit. Other Boeing research and development projects also include a range of applications for beamed power technology, including microwave technology for space solar power.

In November 2008, Spectrolab Inc., a wholly owned Boeing subsidiary, received the 2008 SpotBeam Award for Space Innovation from the California Space Authority in recognition of its 50 years of advancements in photovoltaic solar cell technology, solar panels and related products. Spectrolab was the world's leading supplier of photovoltaic solar cells, solar panels, searchlights and solar simulators, and Spectrolab cells powered 60 percent of all satellites orbiting the Earth, as well as the International Space Station.

Frontiers article, "Harnessing the sun"