Reaching for the stars: Using light to sail through space

The word “liftoff” will come up a lot between now and the end of September. NASA’s Nancy Grace Roman Space Telescope is slated to launch Aug. 30, followed by a Roscosmos Progress resupply mission to the International Space Station (ISS), targeted for Sept. 9. Then, NASA’s SpaceX Crew-13 mission, which rotate the ISS crew, is scheduled to launch no earlier than Sept. 12.

At the School of Engineering and Applied Science, mechanical engineer Igor Bargatin’s lab has spent the last decade building toward its own launches. A few weeks ago, the team proposed a new light sail prototype, an ultrathin, hexagon-patterned film that reflects more than half the laser light hitting it while absorbing almost none. Their findings are published in Nature Communications.

It’s the latest and most concrete step in an idea he’s chased for years: using light alone to hurl objects through space, at scales from a few square inches to interstellar distances.
No fuel needed

It started with nanocardboard, a corrugated, nanometer-thin material that Bargatin’s group showed could levitate on the heat of a light beam. Those results were published in Nature Communications in 2018. Years later, in a study published in Science Advances, they pushed the trick further, edging toward real payloads with a more stable version of their prototype— sturdier discs with carbon nanotubes on their underside.

Both studies targeted the mesosphere, the band of atmosphere between about 30 and 50 miles up, too thin for planes and too low for satellites. “It’s a region of the atmosphere that is almost empty,” Bargatin says—and, until recently, entirely unused.

Bargatin calls it the only regime where people can fly on sunlight alone, with no propellant and no moving parts.

Read the full story at Penn Today.