A Lightsail Powered By Millions of Lasers Could Reach Alpha Centauri in 20 Years

We're edging closer to interstellar reality.
Chris Young

Interstellar exploration might not be lightyears away.

That's because international research project Breakthrough Starshot just provided an update on its plans to send a probe to Alpha Centauri, our closest neighboring star system.

Before getting there, it will have to develop and test a new type of spacecraft propulsion system that utilizes a lightsail and a laser beam array to reach the immense speeds required for interstellar travel within our lifetimes, a press statement from the Australian National University (ANU) explains.

A 40 trillion kilometer journey through space

Breakthrough Starshot's ultra-lightweight spacecraft will have to travel four light-years to reach Alpha Centauri. To put it another way, our nearest neighboring star system is a mind-shattering 40,208,000,000,000 (40 trillion) km away from Earth.

As a point of reference, our fastest and most reliable technology today for long-range space travel is the ion thruster, which is powering NASA's DART mission to a nearby asteroid at speeds of 15,000 mph (24,000 km/h). However, according to NASA, with the ion thruster, it would take 18,000 years, or approximately 2,700 human generations, to get to Alpha Centauri.

Impressively, the Breakthrough Starshot team believes its spacecraft, with the help of lasers located on Earth, will be able to reach unprecedented speeds, allowing it to travel the distance to Alpha Centauri in only 20 years. If it does reach its destination, the probe spacecraft will then send back the first-ever images taken from another solar system, allowing a never-before-seen window to distant planets that may or may not resemble Earth

In a new research paper, the ANU team outlined their concept, which is designed to make travel to Alpha Centauri a feasible proposition. The team is developing a tiny probe with a lightsail that will be powered by a powerful laser array from Earth. That laser array will concentrate millions of beams on the sail throughout its interstellar journey, allowing it to reach incredible speeds.

"To cover the vast distances between Alpha Centauri and our own solar system, we must think outside the box and forge a new way for interstellar space travel," Dr. Bandutunga, from the Applied Metrology Laboratories at the ANU Centre for Gravitational Astrophysics, explains.

"Once on its way, the sail will fly through the vacuum of space for 20 years before reaching its destination. During its flyby of Alpha Centauri, it will record images and scientific measurements which it will broadcast back to Earth." 

Interstellar spaceflight powered by 100 million lasers

To develop their spacecraft, Breakthrough Starshot and the ANU team rely on the advancement of several key technologies. Lightsails, for example, were only recently proved as a viable form of space travel. In 2019, a Carl Sagan-inspired project called LightSail 2 was able to successfully lift its orbital trajectory around Earth by 3.2 kilometers using a lightsail, or solarsail, propelled by photons from the Sun.

The main challenge, however, will come in the form of the ANU team's state-of-the-art laser array proposal, which will have to precisely train millions of lasers to work in unison. "The Breakthrough Starshot program estimates the total required optical power to be about 100 GW — about 100 times the capacity of the world's largest battery today," Dr. Ward, from the ANU Research School of Physics, says. "To achieve this, we estimate the number of lasers required to be approximately 100 million."  

A Lightsail Powered By Millions of Lasers Could Reach Alpha Centauri in 20 Years
One of the first images released by the 2019 LightSail2 mission. Source: The Planetary Society

To keep their lasers pointing precisely at the lightsail for the duration of the journey, the ANU team proposes using a 'guide laser' satellite in Earth's orbit, which will act as the conductor, making sure the entire laser array is pointing at the right coordinates. This, alongside an algorithm designed to pre-correct the light from the array, will help to account for the atmosphere distortion the rest of the Earth-bound lasers will suffer. 

According to Dr. Bandutunga, "the next step is to start testing some of the basic building blocks in a controlled laboratory setting. This includes the concepts for combining small arrays to make larger arrays and the atmospheric correction algorithms." The ANU team also emphasizes the fact that it is part of a global collaboration and that it is only working on one facet of the ambitious project.

Breakthrough Starshot is one of the Breakthrough Initiatives, a series of scientific and technological programs founded by Yuri Milner, designed to search for life outside of our solar system. If the lightsail prototype does become a reality, it could achieve interstellar travel in our lifetimes by reaching the planets surrounding our second nearest star, Alpha Centauri, which gives its name to its star system. Success for the project, therefore, would elevate human beings to the lofty category of interstellar species. The question is, how many others, if any, are out there?

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