Sailing to Alpha Centauri with graphene
Scientists demonstrate potential of 2D material as a light-sail Metal Tech News – October 28, 2020
Last updated 11/3/2020 at 6:15pm
From coronavirus killing facemasks, to ultra-fast charging superbatteries and high-performance headphones with "stunning" sound quality, graphene has emerged as a miracle material with qualities that are likely to change life on Earth. Now, researchers believe this high strength 2D material could unlock mankind's ability to travel to other solar systems.
Liquid fuel rockets can get humans to the most popular destinations across our home solar system in a reasonable amount of time – about three days to the Moon and about six months to Mars. Using the current rocket systems, however, it would take upwards of 75,000 years to get to Alpha Centauri, our closest solar system neighbor.
While we will make faster and more efficient combustion rockets, these will not reach the speeds needed to get us to another solar system in a human lifetime. This is because rocket fuel is heavy and the more rocket fuel added creates more weight, which requires more thrust – it's just not possible to achieve the 10% of lightspeed velocity needed to travel the 4.3 lightyears to Alpha Centauri in 43 years.
One alternative favored by scientists for achieving the speeds needed for interstellar travel is the light-sail, which is where graphene comes in.
Instead of pushing a craft through interstellar space by thrust emitting from a rocket, the light-sail concept proposes pulling the spaceship with a sail that captures light emitted by stars or lasers. While the photonic breeze is gentle, the push is constant and light travels – well, at the speed of light.
It is theorized that a light-sail could pull a spacecraft along at about 134 million miles per hour, or 20% the speed of light. So, that trip to Alpha Centauri would only take a little over 21 years. Still a long trip but it would get you there in time to take in the sights and theoretically come home to tell about your journey.
"Light sailing is the only existing in-space propulsion technology that could allow us to visit other star systems in a human lifespan," said a team of researchers from Netherlands and Estonia testing the use of graphene as a space sail.
The idea of space sailors is not a new one. While observing comets four centuries ago, famous astronomer Johannes Kepler recognized there must be some sort of solar breeze blowing the tails of comets away from the sun.
"Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void," he penned in a 1608 letter to Galileo.
In more recent times, Carl Sagan championed the idea of capturing the subtle force exerted by light to travel through the solar system and beyond.
The sail pulling this craft through the cosmos at near lightspeed, however, would need to be enormous – likely many miles across even for a modest space-faring vessel. This requires a material that is strong but lightweight.
"In order to best harness radiation pressure, light sails need to be highly reflective, lightweight and mechanically robust," said the graphene sail researchers. "This is traditionally achieved by the use of nanometer-thin reflective layers supported by a micrometer-thick substrate that endows them with the necessary sturdiness. This combination usually results in a sail mass that is too high to be efficiently used for extrasolar exploration."
In 2019, the Planetary Society, which was founded by Sagan and is now led by Bill Nye – yes, "The Science Guy" – successfully deployed a shoebox sized craft with cameras and instruments being pulled around by a very thin and highly reflective mylar sail.
"Our LightSail 2 spacecraft, launched 25 June 2019, uses sunlight alone to change its orbit, and is currently operating under an extended mission to further advance solar sailing technology," the Planetary Society penned on its website.
Back on Earth, the team of Netherlands and Estonia scientists have shown that graphene may be a far superior material for future sails. This is not surprising considering graphene's qualities. Organized in a hexagonal lattice of carbon that is just a single atom thick, graphene is truly two dimensional and the strongest material known to man.
To demonstrate this miracle material's potential for capturing heavenly breezes, the European researchers successfully propelled graphene-on-copper sails in vacuum and microgravity.
The tests showed that this propulsion was roughly 10 times more than the theoretical calculations for radiation pressure alone.
"This calls for further theoretical studies and attracts interest on graphene as light-sail material," the scientists penned in a research paper on their results.