Oct 01, 2022
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Since the 1950s, missions to space were always planned, financed and carried out by governmental agencies. In recent years, however, private companies have looked toward the heavens as a potential for making money and having a claim to fame. 

In 2002, Elon Musk, founder of SpaceX (Space Exploration Technologies Corporation), established his  aerospace manufacturer and space transportation services company in Hawthorne, California with the goal of reducing space transportation costs to enable the colonization of Mars.

A cutaway drawing of the prototype, comprising the micro-cells, the molded reflective solar concentrator, and the thin protective glass. (courtesy: BGU)

In 2010, his company was the only private firm capable of returning a spacecraft from low Earth orbit, and SpaceX again made history two years later when its Dragon spacecraft became the first commercial spacecraft to deliver cargo to and from the International Space Station.

Because the private space market is already a rapidly-growing billion-dollar industry with dozens of corporate players, an urgent need has arisen to invent and demonstrate feasible innovative solar solutions. An Israeli academic institution is now getting involved. 

Ben-Gurion University of the Negev Prof. (Emeritus) Jeffrey Gordon and his US colleagues have designed a miniaturized solar-power prototype that offers a major step forward for private commercial space missions. 

NASA is set to send a prototype to the international space station with their first launch next year. Their design and experimental verification were just published in the leading journal Optics Express

For military and government space initiatives, cost basically is no object. But for private missions, cost is a key factor, intensified by the fact that private space corporations have markedly reduced launch costs, so the solar power systems now represent a larger fraction than ever of total system cost. 

Realizing ultra-compact solar devices that can affordably enhance specific power (watts per kilogram) is the key ingredient. The prototype of the university in Beersheba consists of a compact, low-mass, molded-glass solar concentrator bonded to a monolithic integration of transfer-printed micro-scale solar cells each of which comprises several different materials that, together, can efficiently exploit most of the solar spectrum. 

A special feature of the invention is its liberal optical tolerance for accommodating errors in pointing at the sun, structural vibration and thermal distortion, while providing unprecedented specific power. NASA has scheduled a prototype to be included in its first launch of 2020 to the International Space Station for testing under cosmic radiation and the enormous temperature swings in extraterrestrial operation. 

The first-generation prototype is less than 1.7 mm thick, with solar cells that are only 0.65 mm on a side; but a second generation that can increase specific power even further is now being designed by the same team, predicated on more efficient solar cells (now being put together at US Naval Research Labs) that are only 0.17 mm on a side (for perspective, the thickness of a standard sheet of paper is 0.10 mm). 

Because solar concentrator dimensions scale with cell size, the entire second-generation assembly will be less than 1.0 mm thick. Following confirmation of material integrity and robustness under the exacting conditions in outer space, future arrays of these inventions are being planned not only for private space initiatives, but also for space agencies pursuing new missions that require high power for electric propulsion and for operation in deep space (such as missions to Jupiter and Saturn). 

Gordon’s research is funded by a grant from the Israel Ministry of Science, Technology & Space. The research was conducted with colleagues from the Pennsylvania State University, University of Illinois, George Washington University, U.S. Naval Research Laboratory, H-NU Systems, and Northwestern University.