One day in 2016, a scientist visiting the Caltech campus in Pasadena ran into one of the professors from his old aerospace department. After the two exchanged greetings, the instructor told the former PhD student about an audacious idea: Instead of building solar power plants on Earth, what if we built them in space? Forget the desert or rooftops. Space is the best place to catch our nearest star’s energy. The sun never sets. Clouds never obscure it. No atmosphere dampens its radiation. An orbiting power plant could suck sunlight 24-7 and beam power—whoosh!—to anywhere on the planet. If successful, it could offer a perpetual source of affordable, clean energy, reducing greenhouse gas emissions and combating climate change in a major way. Oh, and if that wasn’t enough, perhaps such a power plant could refuel spacecraft near the moon or on interplanetary journeys.
These were the motivating ideas behind Caltech’s Space Solar Power Project, co-led by the professor, Sergio Pellegrino. “It sounded very, very, very futuristic,” recalls the former student, Terry Gdoutos, who at the time was applying his engineering skills to failure analysis. Missing the excitement of working on space programs, he soon joined Pellegrino’s team.
The Space Solar Power Project has since expanded that team of researchers and has been beaming forward—thanks largely to $100 million from a Golden State real estate billionaire couple. It’s in the company of a number of fledgling space-based solar power (SSP) programs underway in Japan, China, Russia, India, and the United Kingdom as well as elsewhere in the United States. But whether it, or any SSP project, has a real future is uncertain. “Proponents have portrayed [SSP] as the smartest, most comprehensive energy solution available, while detractors have seen it as an insanely expensive scheme that will never work,” reads a white paper from the Center for Space Policy and Strategy at the Aerospace Corporation, a nonprofit that provides technical guidance to the space industry and government. “As is typically the case in such arguments, the reality lies somewhere in between—but no one knows exactly where because we have yet to invest sufficient resources to find out.”
This article appears in the Summer 2022 issue of Alta Journal.
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Gdoutos soon learned that while SSP sounded like the future, the concept predates the atomic bomb. Sci-fi author Isaac Asimov first described it in his 1941 short story “Reason,” which takes place on a robotically run space station that collects solar energy and beams it to planets as microwaves. (SSP types never fail to mention this story, citing it so ubiquitously that it almost seems like they’re covering the real story up.)
In 1968, aerospace engineer Peter E. Glaser published the first related technical article, “Power from the Sun: Its Future,” in Science. Five years later, Glaser patented a way to use radio waves to send power from a satellite to a landlubbing “rectifying” antenna, or rectenna, that converts those radio waves into electricity. NASA soon teamed up with defense giant Raytheon Technologies to simulate those ideas from the ground, using satellite parts to send power across a California valley.
The Caltech undertaking traces its origins to 2013, when Donald and Brigitte Bren, two of the school’s trustees and, equally important, billionaires, funded what became known as the Space Solar Power Project. Donald’s Irvine Company owns more than 560 office buildings and 125 apartment complexes, largely in Southern California. “It’s my view that solar energy may be the ultimate solution for energy for most of the world. I believe, based on what little I know about it, that there is a possibility of a breakthrough,” he told the Los Angeles Times in 2011. “I’m on the board at Caltech, and I have a formula I’m going to propose to several Caltech scientists. I think they ought to be able to find a way to harness the power of the sun.”
Usually, scientists come to billionaires with ideas. This time, one came to them.
But the initiative wouldn’t make the news until 2015, when three Caltech professors—Pellegrino, Harry Atwater, and Ali Hajimiri—were announced as the leaders of a $17.5 million SSP research collaboration between the school and defense contractor Northrop Grumman. The Brens’ additional and earlier contributions to the Caltech R&D wouldn’t become public until last August, when it was revealed that they’d given more than $100 million over those interstitial eight years.
The Brens’ money has helped make ideas into objects. “In the beginning, it was all on paper,” says Emily Warmann, who served as one of the project’s research scientists. After that, she says, “we made prototypes painstakingly by hand.” By the end of 2017, they’d constructed two iterations that could collect the sun’s power and send it sans wires.
Here’s the basic idea: A satellite will launch folded up, origami-style, to fit into the small space a rocket requires. Once in space, its carbon fiber–based structure will unfurl, the origami essentially rewinding back into a flat, ultrathin sheet, topped with wafer-width curved mirrors to concentrate the sun’s energy. The flat sheet will comprise strips made up of smaller “tiles.” One side of each tile will hold photovoltaic cells; the other will host antennae. Sunlight will hit the mirrors, concentrate, and stream into the photovoltaics. They’ll convert it into electric current and send it to the antennae. The antennae will turn the current into radio waves, then beam those to rectennae on the ground, which will transmute the radio waves back into electricity. More tiles, more strips, and more rectennae would make the system larger and more powerful.
“It’s a dazzling vision, isn’t it?” Warmann says, portraying no amusement at the pun.
But the team’s prototypes demonstrated that at least part of its original design, the curved mirrors—which Warmann likens to “very shiny venetian blinds”—would be difficult to make to the same specifications in large quantities, owing to the extreme thinness of the material and the errors easily introduced in the manufacturing process. They would be hard, and expensive, to create consistently.
“We learned from that experience and took a step back and said, ‘Well, what if we don’t want to do this?’ ” Warmann says. They’re still thinking—and experimenting—through what they do want to do with the final, large-scale design.
A smaller demo, though, is moving forward: this October, the team plans to launch a two-meter-square prototype aboard a SpaceX Falcon 9. Once above Earth, the prototype will be shuttled to its correct orbit by a “space tug” made by a company called Momentus. (For the record, SpaceX’s founder, Elon Musk, has been a vocal critic of SSP in the past, and Momentus recently faced fraud charges for characterizing a failed demonstration of its technology as a successful one.)
Assuming things remain on track, Caltech’s experiment will test out the origami aspects, the photovoltaic cells, and the wireless power transfer. That last step will shoot power from one end of an enclosure to the other, about a meter.
A meter is a far cry from the hundreds or tens of thousands of miles, depending on the satellites’ orbits, that power-rich radio waves must travel to reach Earth, but the short distance shows that the project has already journeyed pretty far. “When I started, none of the technology that we have right now that works—and we’re getting ready to send to space—existed,” says Gdoutos.
Gdoutos’s favorite use case for SSP, however, doesn’t involve sending power back to Earth: he’d like to see the antennae direct energy to spacecraft on other planets or moons.
Space-to-space cases are actually some of the most compelling in the near term, says Karen L. Jones, a coauthor of that Aerospace Corporation paper—perhaps even to the Caltech project’s main funders. “It’s no coincidence that the Bren family is involved in real estate development,” she says. Companies and countries want to put infrastructure near and on the moon, striking up a “cislunar economy.” “Mining, developing habitats, harvesting ice deposits—this is all energy-intensive work,” Jones says. “And space-based solar power systems could provide the cislunar community with a way forward.” Solar power stations could also send power to other satellites.
On Earth, meanwhile, energy usage is expected to increase by 50 percent by 2050, the same year by which many countries have pledged to reach net-zero carbon emissions. Solar power straight from the sun could help achieve that energy need, without greenhousing the planet. But it’ll take a while, if it happens at all, and, at least initially, it would be more expensive than what exists today. “You can’t compete with cheap solar power here on Earth,” says Jones. SSP is more likely to pop up where grid power isn’t an option, like during a disaster, in a refugee crisis, or in remote regions without access to the grid.
The most interested party, though, is perhaps the military. SSP could supply defense and intelligence satellites as well as terrestrial forward operating bases, those located in the field without infrastructure. That’s why the U.S. Naval Research Laboratory sent an SSP experiment to space aboard its autonomous shuttle, the X-37B, in 2020.
“It was kind of an internal experiment just to show that this technology is viable,” says Melody Martinez of the Air Force Research Laboratory. Once it appeared workable, Martinez’s lab was tapped to take the idea further, spurring, in 2018, a program called SSPIDR, or Space Solar Power Incremental Demonstrations and Research, with a first launch scheduled for 2025.
SSPIDR has paid Northrop Grumman—yes, the same Northrop that partnered with Caltech—more than $150 million since 2019, beating the Brens’ average cash-per-year rate.
The program recently reached a new milestone: in late 2021, in a room in Maryland, Northrop Grumman used powerful LEDs to simulate sunlight and shone them at the photovoltaic part of its own “tile,” which converted the light into radio waves, which were then beamed to the other side of the room, where a rectenna detected them.
Martinez watched over Zoom, from a room in New Mexico. “We’re able to do what we said we were going to do,” she says, beaming.
I’ve been speaking over Zoom with Gdoutos, who is seated on the outdoor patio of a San Diego hotel. With the blue sky behind him, Gdoutos proclaims that his laptop battery is running out. Fiddling with the computer, he notes that SSP could send power to individual devices. Someday, he muses, he might be able to charge his laptop from space instead of an outlet. “That would be really cool,” he says. “Notwithstanding the specific challenges.”
He switches to an iPad and logs into our conversation, which remains mirrored on his computer until he closes it. The specific challenges for Caltech, he says, are hard enough: scaling up to an actually useful size, getting the parts to work together, and finding the right photovoltaic material.
The hard part, in other words, is pretty much the whole thing.
And then, of course, there are the hard parts that don’t involve whether the technology works: the cost-benefit equation, satellite hackers, kinetic attacks, space debris smashing into the system. Oh, and the restrictions and PR problems involved in beaming a bunch of radio waves from space.
Maybe, in this case, a Latin phrase space-farers throw around, Ad astra per aspera, or “To the stars through hardship,” should be retooled to Iungite astra per aspera, or “Harness the stars through hardship.”
The Space Solar Power Project plans to do just that: In 2024, it’ll complete work on an integrated system. It hopes to send a 7-by-7-meter power plant up a couple of years later, then a 25-by-25-meter one in the 2030s. That’s assuming the team doesn’t have to call on Gdoutos’s old bailiwick: failure analysis.
It’s also assuming things don’t go in real life as they do in Asimov’s “Reason.” When SSP advocates speak of their literary origin story, they never mention much of the actual plot. In the tale, the station-running robot decides that Earth is an illusion and stars aren’t real. “Globes of energy millions of miles across! Worlds with three billion humans on them! Infinite emptiness!” the bot says. “Sorry…but I don’t believe it.”
More key, the robot decides that puny humans couldn’t possibly have built such a sophisticated object as itself. “For you to make me seems,” it says, “improbable.” And yet, of course, they had.•
