The Alpha Centauri system is made of three stars and at least two planets orbiting the smaller of the three stars, Proxima. This is also the closest star system to Earth, and for a while, researchers have been seriously considering sending a mission there.
The most famous mission proposal is the Breakthrough Starshot. A nanocraft thinner and lighter than a credit card would be attached to a light and sturdy solar sail. A powerful laser blast would be shot at the sail, accelerating the sail and the spacecraft to one-fifth of the speed of light.
Thanks to that initial push, the nanocraft could complete the 4.37 light-year journey to the Alpha Centauri system in just 20 years. For comparison, a chemical rocket would take more than 30,000 years to make it all the way there.
The Breakthrough Initiatives are not just planning an interstellar mission. Every year, around the anniversary of Yuri Gagarin's first flight into space they organize a conference known as Breakthrough Discuss. The 2021 conference had a very interesting title: “The Alpha Centauri System: A Beckoning Neighbor.” And we have heard some fascinating talks and some bold proposals for a mission to Proxima Centauri.
The first day focused on the incredible observations that are being done on our closest stellar neighbor. This included discussions on life on the planets orbiting Proxima Centauri as well as the peculiar radio signal detected from the system by the Search For Extraterrestrial Intelligence (SETI).
On the second day of Breakthrough Discuss, the conversation focused more on technology. The focus was on how to send a probe to the Alpha Centauri system and how a probe 4.37 light-years away would communicate its findings back to Earth.
One of the mission designs was presented by Professor Artur Davoyan from UCLA. He discussed the current challenges to make Breakthrough Starshot work: you need a very powerful laser array, a working nanocraft and light sail, and a way to communicate back to Earth from deep space. Each is a work in progress with many challenges involved.
But there is excitement in taking those challenges on, and he discussed an ingenious design for a spacecraft that might not reach Alpha Centauri but would allow the exploration of the solar system faster than we have ever done before.
Instead of having a nanocraft attached to a light sail, he put forward a design where the light-sail and the nanocraft are the same thing and weigh just 1 gram (0.035 ounces). This design is doable with current technology, and with a 100 Megawatt laser (powerful yes but nothing out of sci-fi), the 1 gram wafer-thin craft can be accelerated to really high velocities. It would get to Mars in just one month, and to Pluto in about two years.
This approach could be an important stepping stone for the Breakthrough Starshot, but it could also become a way to explores some of the worlds of the Solar System like Uranus and Neptune, which has only been visited once.
Another interesting design came from Michael Paluszek, who discussed a longer-term mission to Alpha Centauri. This would embrace the power of nuclear fusion – something that humanity is inching closer and closer to mastering. Such design won’t be the light and slick nanocraft but a bulkier van-sized spacecraft.
While not capable of reaching 20 percent of the speed of light, this propulsion method could still achieve impressive speed. A flyby of Alpha Centauri would happen in only 400 years – but the spacecraft could be designed to enter orbit around the planet Proxima Centauri b in 500 years. Sure, many human lifetimes, but not the 30,000 years of chemical rockets.
The mission to Alpha Centauri is not quite ready yet, but the technology investigations are certainly fascinating and will have an impact far beyond the goal of visiting another star.