(Photo: Y. Beletsky (LCO)/ESO, CC BY 4.0
A new study suggests that tiny spaceships the size of cellphones could travel across the solar system using laser-powered sails, allowing them to reach far quicker speeds - and, possibly, much farther destinations - than conventionally fueled rockets.
In principle, it would take thousands of years for a spacecraft to travel between the stars using conventional rockets. Alpha Centauri, for example, is around 4.37 light-years away from Earth, or more than 25.6 trillion miles (41.2 trillion kilometers), or more than 276,000 times the distance between Earth and the sun.
Even if NASA's Voyager 1 spacecraft, which launched in 1977 and reached interstellar space in 2012, were heading in the proper direction, which it isn't, it would take nearly 75,000 years to reach Alpha Centauri, according to Space.com.
The issue with all rocket thrusters is that the propellant they use has mass. Long journeys necessitate a lot of propellant, which makes spaceships heavy, which necessitates more propellant, which makes them heavier, and so on.
Previous research has suggested that "light sailing" may be one of the only theoretically conceivable ways to send a spacecraft to another star within the lifetime of a person.
For example, the $100 million Breakthrough Starshot project, unveiled in 2016, aims to send swarms of microchip-sized spacecraft to Alpha Centauri, each with ultra-thin, ultra-reflective sails propelled by the most powerful lasers ever produced. According to the concept, they will travel at up to 20% the speed of light, arriving at Alpha Centauri in around 20 years.
The construction of the lasers required for propulsion is a key problem for Starshot. It asks for a ground-based laser array measuring 0.4 square miles (1 square kilometer) in size and capable of producing 100 gigawatts of power, making it the most powerful laser ever built on Earth.
According to the new study, a more modest ground-based laser array - one 3.3 to 33 feet (1 to 10 meters) broad and 100 kilowatts to 10 megawatts in power - might nevertheless be effective for launching tiny probes beyond the solar system, propelling them to considerably faster speeds than rocket engines could.
"Such lasers can be built already today with a relatively small investment," study senior author Artur Davoyan, a materials scientist at the University of California, Los Angeles, told Space.com. "We do not need to wait till a 100-gigawatt laser becomes available."
Researchers say a 0.035-ounce laser sail with a 4-inch sail traveling at 112,000 mph (180,000 km/h) could reach Mars in 20 days, compared to 200 days for NASA's Perseverance rover; Jupiter in 120 days, compared to five years for NASA's Juno probe; Pluto in less than three years, compared to 10 years for NASA's New Horizons craft; and 100 times the distance between Earth and the sun in ten years, compared
The scientists are now hoping to put their theories to the test and prototype them. They detailed their findings online Jan. 31 in the journal Nano Letters.
