NASA too down on space-based solar power?
Agency report finds orbiting power stations more expensive than renewables on Earth, but advocates say it overlooks cost breakthroughs
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This month, NASA cast a shadow on one of the most visionary prospects for freeing the world from fossil fuels: collecting solar energy in space and beaming it to Earth. An agency report found the scheme is feasible by 2050 but would cost between 12 and 80 times as much as ground-based renewable energy sources. Undaunted, many government agencies and companies are pushing ahead with demonstration plans. Some researchers say NASA’s analysis is too pessimistic.
“There are assumptions that are just wrong and others that are incredibly conservative,” says Martin Soltau, co-CEO of Space Solar, a development company funded by the U.K. government and industry. “There’s no imagination.” He and others note that NASA itself says slightly rosier assumptions—including a drop in launch costs that many think is within reach—would suddenly make the technology competitive with ground-based renewable energy.
Space-based solar power has many charms. For one, there are no clouds in space, and, in the right location, no night. In geostationary orbit, arrays of solar panels can track the Sun and gather energy 24/7, sending it to Earth in microwave beams gentle enough to avoid frying birds and airplanes. With free real estate, the orbiting structures can be made big enough to produce a few gigawatts (GW), rivaling the output of a nuclear or coal-fired power plant. Lifting thousands of tons of material into orbit is the main problem. NASA studied the idea in the 1970s but found that with space shuttle launches and astronaut assembly it was prohibitively expensive.
This month, NASA cast a shadow on one of the most visionary prospects for freeing the world from fossil fuels: collecting solar energy in space and beaming it to Earth. An agency report found the scheme is feasible by 2050 but would cost between 12 and 80 times as much as ground-based renewable energy sources. Undaunted, many government agencies and companies are pushing ahead with demonstration plans. Some researchers say NASA’s analysis is too pessimistic.
“There are assumptions that are just wrong and others that are incredibly conservative,” says Martin Soltau, co-CEO of Space Solar, a development company funded by the U.K. government and industry. “There’s no imagination.” He and others note that NASA itself says slightly rosier assumptions—including a drop in launch costs that many think is within reach—would suddenly make the technology competitive with ground-based renewable energy.
Space-based solar power has many charms. For one, there are no clouds in space, and, in the right location, no night. In geostationary orbit, arrays of solar panels can track the Sun and gather energy 24/7, sending it to Earth in microwave beams gentle enough to avoid frying birds and airplanes. With free real estate, the orbiting structures can be made big enough to produce a few gigawatts (GW), rivaling the output of a nuclear or coal-fired power plant. Lifting thousands of tons of material into orbit is the main problem. NASA studied the idea in the 1970s but found that with space shuttle launches and astronaut assembly it was prohibitively expensive.
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Advances in automated assembly and sharp drops in the costs of solar panels and rocket launches are prompting governments and space agencies to take another look. NASA, for instance, examined the life cycle cost of electricity for a 2-GW orbiting power station, in two configurations: one that uses steerable mirrors to concentrate light onto photovoltaic cells and converts the energy into microwaves for beaming to Earth, and another that uses a multitude of “sandwich panels,” with solar cells on one side and a microwave transmitter on the other. Whereas the more flexible mirror system can beam power 99% of the time, the flat panels are limited to 60% by the need to face the Sun.
The report found the mirror configuration was more cost-effective. But even it would require lifting 5900 tons to orbit and more than 2300 rocket launches. These launch costs account for 71% of the total price tag of $276 billion.
NASA is counting on Starship, a fully reusable giant rocket under development by SpaceX. It will be capable of lofting up to 150 tons at a time to low-Earth orbit, once it gets over the teething problems that doomed the first two test launches. The company’s partially reusable Falcon 9 rocket has already revolutionized the launch business since its debut in 2010, lowering launch costs from upward of $7000 per kilogram of payload to less than $3000 per kilogram. “Once Starship is operational, it’s all going to change again,” says Laura Forczyk of Astralytical, a space industry consultancy
Advances in automated assembly and sharp drops in the costs of solar panels and rocket launches are prompting governments and space agencies to take another look. NASA, for instance, examined the life cycle cost of electricity for a 2-GW orbiting power station, in two configurations: one that uses steerable mirrors to concentrate light onto photovoltaic cells and converts the energy into microwaves for beaming to Earth, and another that uses a multitude of “sandwich panels,” with solar cells on one side and a microwave transmitter on the other. Whereas the more flexible mirror system can beam power 99% of the time, the flat panels are limited to 60% by the need to face the Sun.
The report found the mirror configuration was more cost-effective. But even it would require lifting 5900 tons to orbit and more than 2300 rocket launches. These launch costs account for 71% of the total price tag of $276 billion.
NASA is counting on Starship, a fully reusable giant rocket under development by SpaceX. It will be capable of lofting up to 150 tons at a time to low-Earth orbit, once it gets over the teething problems that doomed the first two test launches. The company’s partially reusable Falcon 9 rocket has already revolutionized the launch business since its debut in 2010, lowering launch costs from upward of $7000 per kilogram of payload to less than $3000 per kilogram. “Once Starship is operational, it’s all going to change again,” says Laura Forczyk of Astralytical, a space industry consultancy
NASA also assumed that for every launch of hardware into low orbit another 12 would be needed to supply fuel for rockets to transfer the hardware to much higher geostationary orbits. Soltau says this has “a massive multiplying effect” on cost and that solar-powered space tugs could transfer the hardware much more cheaply—although more slowly. He also points out that NASA compared the cost of first-of-a-kind space hardware against mature wind and solar technologies on Earth. When NASA adopted rosier assumptions—$500 per kilogram launch costs, electric space tugs to boost orbits, and cheaper hardware—it found that space-based solar power was not only just as cheap as ground-based renewable energy, but also just as green, in terms of its life-cycle greenhouse gas emissions.
Given its pessimistic bottom line, the NASA report recommended proceeding cautiously. But others are pushing ahead. Last week, researchers at the California Institute of Technology announced the completion of a yearlong space mission, funded by $100 million from philanthropists Donald and Brigitte Bren, which tested, among other things, transmitting power using a microwave beam. “It’s a great first step,” Vijendran says.
In 2025, the U.S. Air Force Research Laboratory and Japan’s space agency will each test beaming microwave power from a spacecraft in orbit to the ground. ESA has studied possible architectures and is seeking funding from its member states for technology development. Space Solar is asking the U.K. government to fund a 6-year, $800 million development program that would put a 1-megawatt end-to-end demonstrator in orbit. “Space has a huge role to play in achieving net-zero emissions,” Soltau says. “NASA should absolutely be at the forefront of this.”
NASA also assumed that for every launch of hardware into low orbit another 12 would be needed to supply fuel for rockets to transfer the hardware to much higher geostationary orbits. Soltau says this has “a massive multiplying effect” on cost and that solar-powered space tugs could transfer the hardware much more cheaply—although more slowly. He also points out that NASA compared the cost of first-of-a-kind space hardware against mature wind and solar technologies on Earth. When NASA adopted rosier assumptions—$500 per kilogram launch costs, electric space tugs to boost orbits, and cheaper hardware—it found that space-based solar power was not only just as cheap as ground-based renewable energy, but also just as green, in terms of its life-cycle greenhouse gas emissions.
Given its pessimistic bottom line, the NASA report recommended proceeding cautiously. But others are pushing ahead. Last week, researchers at the California Institute of Technology announced the completion of a yearlong space mission, funded by $100 million from philanthropists Donald and Brigitte Bren, which tested, among other things, transmitting power using a microwave beam. “It’s a great first step,” Vijendran says.
In 2025, the U.S. Air Force Research Laboratory and Japan’s space agency will each test beaming microwave power from a spacecraft in orbit to the ground. ESA has studied possible architectures and is seeking funding from its member states for technology development. Space Solar is asking the U.K. government to fund a 6-year, $800 million development program that would put a 1-megawatt end-to-end demonstrator in orbit. “Space has a huge role to play in achieving net-zero emissions,” Soltau says. “NASA should absolutely be at the forefront of this.”
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