Space Based Solar Power

A considerable next step for Space exploration.

Caltech Tests Space-Based Solar Power Using a satellite as testbed for wirelessly beaming power from orbit  By Ned Potter   in IEEE Spectrum

For about as long as engineers have talked about beaming solar power to Earth from space, they’ve had to caution that it was an idea unlikely to become real anytime soon. Elaborate designs for orbiting solar farms have circulated for decades—but since photovoltaic cells were inefficient, any arrays would need to be the size of cities. The plans got no closer to space than the upper shelves of libraries.

That’s beginning to change. Right now, in a sun-synchronous orbit about 525 kilometers overhead, there is a small experimental satellite called the Space Solar Power Demonstrator One (SSPD-1 for short). It was designed and built by a team at the California Institute of Technology, funded by donations from the California real estate developer Donald Bren, and launched on 3 January—among 113 other small payloads—on a SpaceX Falcon 9 rocket.

“To the best of our knowledge, this would be the first demonstration of actual power transfer in space, of wireless power transfer,” says Ali Hajimiri, a professor of electrical engineering at Caltech and a codirector of the program behind SSPD-1, the Space Solar Power Project.

The Caltech team is waiting for a go-ahead from the operators of a small space tug to which it is attached, providing guidance and attitude control. If all goes well, SSPD-1 will spend at least five to six months testing prototype components of possible future solar stations in space. In the next few weeks, the project managers hope to unfold a lightweight frame, called DOLCE (short for Deployable on-Orbit ultraLight Composite Experiment), on which parts of future solar arrays could be mounted. Another small assembly on the spacecraft contains samples of 32 different types of photovoltaic cells, intended to see which would be most efficient and robust. A third part of the vehicle contains a microwave transmitter, set up to prove that energy from the solar cells can be sent to a receiver. For this first experiment, the receivers are right there on board the spacecraft, but if it works, an obvious future step would be to send electricity via microwave to receivers on the ground.

A gold-colored square frame flying in space with Earth in background.Caltech’s Space Solar Power Demonstrator, shown orbiting Earth in this artist’s conception, was launched on 3 January.CALTECH

One can dismiss the 50-kilogram SSPD-1 as yet another nonstarter, but a growing army of engineers and policymakers take solar energy from space seriously. Airbus, the European aerospace company, has been testing its own technology on the ground, and government agencies in China, Japan, South Korea, and the United States have all mounted small projects. “Recent technology and conceptual advances have made the concept both viable and economically competitive,” said Frazer-Nash, a British engineering consultancy, in a 2021 report to the U.K. government. Engineers working on the technology say microwave power transmissions would be safe, unlike ionizing radiation, which is harmful to people or other things in its path.

No single thing has happened to start this renaissance. Instead, say engineers, several advances are coming together.

For one thing, the cost of launching hardware into orbit keeps dropping, led by SpaceX and other, smaller companies such as Rocket Lab. SpaceX has a simplified calculator on its website, showing that if you want to launch a 50-kg satellite into sun-synchronous orbit, they’ll do it for US $275,000.

Meanwhile, photovoltaic technology has improved, step by step. Lightweight electronic components keep getting better and cheaper. And there is political pressure as well: Governments and major companies have made commitments to decarbonize in the battle against global climate change, committing to renewable energy sources to replace fossil fuels.

Most solar power, at least for the foreseeable future, will be Earth-based, which will be cheaper and easier to maintain than anything anyone can launch into space. Proponents of space-based solar power say that for now, they see it as best used for specialty needs, such as remote outposts, places recovering from disasters, or even other space vehicles.

But Hajimiri says don’t underestimate the advantages of space, such as unfiltered sunlight that is far stronger than what reaches the ground and is uninterrupted by darkness or bad weather—if you can build an orbiting array light enough to be practical.

Most past designs, dictated by the technology of their times, included impossibly large truss structures to hold solar panels and wiring to route power to a central transmitter. The Caltech team would dispense with all that. An array would consist of thousands of independent tiles as small as 100 square centimeters, each with its own solar cells, transmitter, and avionics. They might be loosely connected, or they might even fly in formation.

A sped-up series of pictures shows a square frame unfolding in a lab. An engineer watches in a smock and head covering.Time-lapse images show the experimental DOLCE frame for an orbiting solar array being unfolded in a clean room.CALTECH

“The analogy I like to use is that it’s like an army of ants instead of an elephant,” says Hajimiri. Transmission to receivers on the ground could be by phased array—microwave signals from the tiles synchronized so that they can be aimed with no moving parts. And the parts—the photovoltaic cells with their electronics—could perhaps be so lightweight that they’re flexible. New algorithms could keep their signals focused.

“That’s the kind of thing we’re talking about,” said Harry Atwater, a coleader of the Caltech project, as SSPD-1 was being planned. “Really gossamer-like, ultralight, the limits of mass-density deployable systems.”

If it works out, in 30 years maybe there could be orbiting solar power fleets, adding to the world’s energy mix. In other words, as a recent report from Frazer-Nash concluded, this is “a potential game changer.” ... '

On How Not to Win a Tech Ware

Thoughtful points, more at the link

From ACM DEPARTMENTS

How Not to Win a Tech War      By Moshe Y. Vardi

Communications of the ACM, January 2023, Vol. 66 No. 1, Page 7   10.1145/3571077

CACM Senior Editor Moshe Y. Vardi

A paradox: for the U.S. to compete with China, the U.S. is using Chinese talent. But let's start from the beginning. In May 2022, I predicted a "tech war" between the U.S. and China. "If computing technology is viewed as strategic technology," I wrote, "then we may have to say goodbye to the research world in which we openly collaborated and openly published." The tech war has come faster than I personally would have predicted.

In early August 2022, the U.S. authorized USD280B in taxpayer money to subsidize American computer-chip companies and invest in technology research for the sake of "keeping America strong and innovative." Following that, in early October 2022, the U.S. imposed limits on semi-conductor exports to China, aimed at limiting China's ability to make advanced semiconductors. The White House issued sweeping restrictions on selling semiconductors and chip-making equipment to China, in an attempt to curb the country's access to critical technologies.

Critics have questioned both legs of this strategy. On one hand, an investment of USD52B is considered relatively small, considering that a single major Taiwanese semiconductor manufacturer—TSMC—announced in 2022 new capital investments of more than USD40B. On the other hand, China has been a major market for the U.S. tech industry, and the growing separation between American and Chinese tech markets will also hurt U.S. companies.

But tech wars are ultimately won by innovation, which requires both financial and human capital. The U.S. benefited tremendously by being a magnet for worldwide talent. According to the 2021 Taulbee Surveyb of the Computing Research Association, approximately 65% of doctoral students in computing in North America are international students. My estimate is that this pool of international students is dominated by Chinese students. My own research program has been greatly enriched by my Chinese students. This means the technological competition with China is aided, to a significant degree, by Chinese students. Hence, the opening sentence of this column.

But while American universities are still eager to attract Chinese talent, several U.S. actions imply otherwise. In 2018, the U.S. Department of Justice launched the "China Initiative," reflecting the strategic priority of the U.S. in "countering Chinese national security threats." Yet several prosecution cases under the China Initiative have ended in acquittals. Chinese-origin and Chinese-descent scientists and students studying and working in the U.S. bore and continue to bear the brunt of the suspicion. A September 2022c report by the Asian-American Scholars Forum (AASF) pointed out that feeling the pressure of potential federal investigations since the launch of the China Initiative, Chinese-origin scientists in the U.S. now face higher incentives to leave the U.S. and lower incentives to apply for federal grants. Furthermore, it has recently been reportedd that the number of new Chinese students at U.S. colleges has plummeted from pre-pandemic levels.

A week after the AASF report was published, the U.S. National Academies issued a report entitled "Protecting U.S. Technological Advantage." The main point of that report is that maintaining U.S. global leadership in science and technology requires a greater focus on strengthening innovation, and not solely on restricting access to specific technologies, calling on the U.S. to strive to maximize the amount of work that can be appropriately performed in an open research environment.

The National Academies' report also called on the U.S. to develop policies and programs aimed at developing domestic research talent. But the domestic doctoral talent pipeline has been shriveling for decades. In the mid-1990s, David Goodstein, a CalTech physicist, wrote in a blog: "The best American students have proved their superior abilities by reading the handwriting on the wall and going into other lines of work instead of choosing graduate school … The humming machinery kept right on going, fed by ore imported from across the oceans … Foreign graduate students have, temporarily at least, rescued our way of life."  ... ' 

Photonic Chips

 New developments in Photonic Chips

Caltech's Nanophotonic Chip 'Squeezes' More Out of Light

By Caltech, October 18, 2022

The photonic chip can generate and measure quantum states of light in ways previously only possible with bulky and expensive laboratory equipment.

Credit: Natasha Mutch and Nicolle R. Fuller, Sayo Studio

Electronic computing and communications have advanced significantly since the days of radio telegraphy and vacuum tubes. In fact, consumer devices now contain levels of processing power and memory that would be unimaginable just a few decades ago.

But as computing and information processing microdevices get ever smaller and more powerful, they are running into some fundamental limits imposed by the laws of quantum physics. Because of this, the future of the field may lie in photonics—the light-based parallel to electronics. Photonics is theoretically similar to electronics but substitutes photons for electrons. They have a huge potential advantage in that photonic devices may be capable of processing data much faster than their electronic counterparts, including for quantum computers.

Currently, the field is still very active in fundamental research and lacks crucial devices that are needed to become practical. However, a new photonic chip developed at Caltech may represent a critical breakthrough for the field, especially for enabling photonic quantum information processors. It can generate and measure quantum states of light in ways that were previously only possible with bulky and expensive laboratory equipment.

From Caltech  View Full Article     

Consider the Chip Sandwich

Chip Sandwiches improve Data Transmission

Chip Sandwich Pushes Boundaries of Computing, Data Transmission Efficiency  By California Institute of Technology, November 22, 2022

An electronics chip (the smaller chip on the top) integrated with a photonics chip, sitting atop a penny for scale.

The Caltech/Southampton team designed both an electronics chip and a photonics chip from the ground up, then co-optimized them to work together.

Engineers at the California Institute of Technology (Caltech) and the U.K.'s University of Southampton have developed an ultrafast electronic/photonic chip sandwich that generates minimal heat.

Created over four years, "These two chips are literally made for each other, integrated into one another in three dimensions," said Caltech's Arian Hashemi Talkhooncheh.

The chips employ an optimized interface to transmit 100 gigabits of data per second while generating 2.4 pico-Joules per transmitted bit, boosting the transmission's electro-optical power efficiency 3.6 times over the current state of the art ... 

"As the world becomes more and more connected, and every device generates more data, it is exciting to show that we can achieve such high data rates while burning a fraction of power compared to the traditional techniques," said Caltech's Azita Emami.

From California Institute of Technology

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