Artist's depiction of the proposed Japanese IKAROS space-probe using a solar sail powered by a powerful ground-based laser.
(Image Sources: Wikipedia.org, By Andrzej Mirecki - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14656159)
By Glenn A. Walsh
Reporting for SpaceWatchtower
Solar sails which could propel spacecraft to other planets, or possibly even to distant stars, have been a dream of scientists since the 19th century. A light-sail design would accelerate a spacecraft slowly, but it would speed-up to high speeds over a longer period of time.
Particularly for possible interstellar travel, our current use of rockets with chemical propellants would not be efficient or effective. And, a large part of the thrust has to be used just to transport the heavy fuel needed for later in the mission.
Originally conceived to take advantage of the solar wind of our Sun (and, perhaps, that of other stars), today light-sail spacecraft are more likely to use strong ground-based (and, perhaps, some day space-based) lasers for such spacecraft propulsion.
However, when using a ground-based laser, one potential problem has been to keep the laser-sail spacecraft from straying away from the laser beam and veering off-course. Optical scientists from the Chester F. Carlson Center for Imaging Science at the Rochester Institute of Technology and the BEAM Engineering for Advanced Measurements are experimenting with solutions to this problem.
While previous light-sail designs simply acted like mirrors to reflect the laser-light back to the source, the new design uses liquid crystals in diffraction gratings to better stabilize the spacecraft. If the spacecraft starts drifting toward the left, the new sail deflects light to the right and visa-versa. Hence, the spacecraft is forced to position itself back to where the laser beam falls on the center of the sail.
Today, diffraction gratings are used to help encode music and other information on compact disks and digital video disks. One of the effects of diffraction, which some people may be familiar with, is the rainbow effect seen when light is reflected from a CD or DVD.
The original experiment, which was successful, simply used diffraction gratings on the left and right sides of the sail. Now, the researchers are beginning experiments to test diffraction gratings that could center a spacecraft, no-matter which direction it drifts (not just to the right or to the left). They hope that future experiments could be conducted in Earth orbit, on the International Space Station or a separate satellite.
This research was published by researchers Ying-Ju Lucy Chu, Nelson V. Tabiryan, and Grover A. Swartzlander, Jr. in the 2019 December 13 issue of the journal Physical Review Letters.
In 2016, Breakthrough Starshot Initiative announced a plan to launch swarms of micro-chip-sized spacecraft toward the Alpha Centauri star system, the closest multi-star system to the Earth. Proposed to cost up to $100 million, the very small spacecraft would include thin, reflective, and very light-weight laser-light sails, propelled by incredibly powerful lasers based on Earth. The project proponents hope each spacecraft could reach speeds close to 20 per-cent of the speed of light, reaching the Alpha Centauri system 20 years after launch.
Internet Links to Additional Information ---
Solar Sail: Link >>> https://en.wikipedia.org/wiki/Solar_sail
Link 1 >>> http://breakthroughinitiatives.org/initiative/3
Link 2 >>> https://en.wikipedia.org/wiki/Breakthrough_Starshot
Abstract: Research Paper -
"Experimental Verification of a Bigrating Beam Rider."
Ying-Ju Lucy Chu, Nelson V. Tabiryan, and Grover A. Swartzlander, Jr.
Phys. Rev. Lett. 123, 244302 - Published 2019 Dec. 13.
Link >>> https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.244302
Related Blog Posts ---
"Nano-Space Probes to Star Alpha Centauri by Laser-Sail ?" Thur., 2017 Dec. 7.
"Laser-Propelled Nano-Space Probe to Reach Alpha Centauri in 20 Years?." Thur., 2016 April 14.
"Solar Sail Spacecraft Test in 2016." Thur., 2014 July 17.
Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
Monday, 2020 January 27.
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