A breakthrough method for fabricating nanotechnology-based lightsails that use laser-powered radiation to reach as much as 20% of the speed of light, developed by researchers from the Netherlands’ Delft University of Technology and Brown University, could theoretically reduce manufacturing from years to hours.
The researchers behind the technological leap believe their method is also scalable enough to function as a critical leap toward designing and building the massive sails needed to explore distant planets and nearby stars. Their approach also opens the door to a new type of nanoscale manufacturing that could have several practical applications.
“This is not just another step in making things smaller; it’s an entirely new way of thinking about nanotechnology,” explained Delft University Associate Professor and research team leader Richard Norte in a statement. “We’re creating high-aspect-ratio devices that are thinner than anything previously engineered but span dimensions akin to massive structures.”
How Lasers and Lightsails Can Achieve Over 20% of the Speed of Light
Since the Soviet Union launched humanity’s first satellite into space nearly seven decades ago, scientists have been looking for better, more efficient, and more powerful ways to propel a spacecraft. Some exotic propulsion designers have made claims, ranging from drives that could tap into a hidden force or other quantum fields to various nuclear fusion-based or nuclear fusion-enhanced pulsed plasma propulsion concepts.
quantum drive, lightsails
IVO Ltd.’s controversial Quantum Drive may use an unknown force to generate propulsion. Image credit: IVO Ltd.
Even more exotic concepts include an emerging group of warp drive theories that could theoretically break the speed of light. One seemingly more viable theory researchers call a “constant velocity” warp drive that might reach 99% light speeds also appears unattainable with current technologies.
More practical exotic propulsion concepts have begun to emerge, including a drive that uses liquid metal as a propellant and a rotating detonation rocket engine. A design similar to a lightsail is a solar sail, which uses the radiative pressure from sunlight to accelerate to speeds capable of multi-year missions that cross the solar system. Another concept, known as Wind Rider, involves using a plasma magnet to create a magnetic field around a spacecraft that can “sail” the high-energy particles expelled by the Sun, called the solar wind, to incredibly high speeds.
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Artist’s rendering of a Wind Rider plasma magnet concept sailing the solar wind to achieve extreme speeds. Image: Michel Lamontagne.
Still, to achieve the extreme speeds necessary to plan a mission to one of Earth’s nearby stars requires propulsion concepts that are significantly more speculative than any of those more practical designs. According to the Delft and Brown researchers behind the nanotechnology breakthrough, their process offers a seemingly viable approach to bringing lightsails capable of 20% of the speed of light to real-world use.
The Breakthrough Starshot Initiative and the Advantages of Lightsails
When scientists introduced the Breakthrough Starshot Initiative, which was designed to advance research supporting sending a lightsail-propelled spacecraft to Earth’s nearest stellar neighbor in 2016, the technology to produce even the smallest segment of a viable light sail was in its infancy.
According to a statement from the Delphi and Brown research team, initial estimates to construct the proposed lightsail reflector using the technology available at the time reached as much as 15 years “mainly because it is covered in billions of nanoscale holes.”. Still, the potential benefits of a technologically viable propulsion system capable of reaching a significant fraction of light speed made the possibility of a lightsail worth pursuing.
In a story about the future of exotic propulsion, Harvard Scientist Avi Loeb described how a lightsail could accomplish such a feat, noting that “a gram-mass payload on a human-size sail is pushed by a 100-giga-Watt laser over a few minutes to a fraction of the speed of light across a distance that is five times farther than the Moon.”
In another story for The Debrief, Loeb, a member of the Breakthrough Starshot team, offered a comparison between a lightsail-propelled spacecraft and humanity’s most distant probes, the oldest of which was launched in the 1970s.
“The five probes that NASA launched to interstellar space, namely Voyager 1, Voyager 2, Pioneer 10, Pioneer 11, and New Horizons, are still making their way through the Solar system,” Loeb wrote. “Over the past half-century, they traversed less than a tenth of a percent of the distance to the nearest star. A light sail moving near the speed of light could surpass their distance a day after launch.”
Using Nanotechnology to Print Enormous Sails
In their published study, the research team outlined the process they used to increase the size of lightsails while reducing the time to create this delicate material. According to team leader Norte, the team also employed a new gas-based etching process to remove the support materials underneath their nanofabricated sails, “leaving behind only the sail.”
lightsails, 20% of the speed of light
Associate Professor Richard Norte in his lab in Delft (The Netherlands) (Credit: Delft University of Technology).
“If the sails break, it’s most likely during manufacturing,” Norte said. “Once the sails are suspended, they are actually quite robust.”
When comparing their results to those from other research institutes trying to perfect the nanofabrication of lightsails, the team highlighted work by CalTech scientists that demonstrated the ability to exert nanoscale control over sail structures “at micrometer scales.” Conversely, Norte says his team’s approach can scale this production up to centimeter-sized structures without losing their nanoscale manufacturing ability.
International Space Station
The team’s proof-of-concept prototype measures 60mm x 60mm and is 200 nanometres thick. Critically, the lightsail material is covered in billions of nanosized holes like light sails produced by conventional methods.
lightsails, 20% of the speed of light
A side-by-side comparison between the team’s produced nanomaterial and the largest lightsail available at Breakthrough Starshot’s announcement in 2016. Credit: Richard Norte.
By combining the same quality and engineering specifications with the ability to print the material at the nanoscale, the team says their technology, if scaled up, could reduce the 15-year manufacturing projection to a single day. They also say their scaled-up prototype would extend over seven football fields long while maintaining a millimeter thickness.
“It’s not just its high aspect ratio that makes this material special; it’s the simultaneous combination of large scale and nanoscale in the same material that makes it lightweight and reflective,” Norte said.
Upcoming Experiments and Potential New Avenues of Research
The research team is now designing experiments using laser power to push their prototype lightsails across centimeters of distance against Earth’s gravity. While short distance compared to interstellar travel, Norte notes that this distance “would be 10 billion times farther than anything pushed with lasers so far.”
Beyond manufacturing lightsails, Norte says their nanotechnology-based approach to manufacturing can open new opportunities for several industries. He also believes his team’s method could open up avenues of research around fundamental questions of physics, including how fast human-made technologies can ultimately accelerate an object.
“Now that we can make these lightsails as large as semiconductors can make wafers, we are exploring what we can do with today’s capabilities in nanofabrication, lasers, and design,” he said. “In some ways, I think it might be just as exciting as missions beyond the solar system.”
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him onX,learn about his books atplainfiction.com, or email him directly atchristopher@thedebrief.org.