How will interstellar travel work?

We humans may dream of reaching the stars, but unfortunately for us, the stars are really, really far away. It took the New Horizons probe almost a decade to reach Pluto, but that’s nothing compared to interstellar travel. Our closest star system, Alpha Centauri, is over 4 light years away – if it were possible to reach by Space Shuttle, the journey would take more than 150,000 years. To put that into perspective, modern humans only evolved about 200,000 years ago. With our current capabilities, interstellar travel is still shelved in the science fiction section.

Alpha Centauri, star, stars, space, interstellar, closest star, telescope

It would take even our fastest current probes around 30,000 years to reach Alpha Centauri, visible here as the bright orange star on the lower right. Image credit: Y Beletsky (LCO), ESO.

However, a new project announced yesterday by Russian billionaire Yuri Milner and physicist Stephen Hawking aims to overcome this cosmic distance problem. Breakthrough Starshot is a $100 million research and engineering initiative to develop tiny probes that can travel at 20% the speed of light, capable of reaching our nearest star system within a generation. But how is this possible?

If it were possible to reach Alpha Centauri by Space Shuttle, the journey would take more than 150,000 years

Small-scale space probes

The past few decades are testament to the fact that gadgets are getting smaller: the brick-like mobile phones of the 1980s seem ridiculous compared to the super-slim smartphones of today. This trend of tinier tech is down to a relationship known as Moore’s law, which states that the number of transistors that can fit on a circuit doubles every 18 months. Essentially this means that we can build smaller and smaller devices.

Thanks to this miniaturisation of electronics, it is entirely feasible that we could create tiny probes that contain all the necessary components for them to collect, send and receive data. The Breakthrough project envisions a wafer-like probe called a StarChip, with cameras, thrusters, a power source as well as navigation and communication equipment, all packed onto a platform the size of a postage stamp.

Yuri Milner announcing Breakthrough Starshot

“We came to the conclusion it can be done: interstellar travel” announced Yuri Milner, who is investing $100 million in the project. Image credit: 2016 Getty Images, Bryan Bedder.

Star sailors

The tiny StarChip will be ferried across space by a Lightsail (also known as a solar sail), a super-thin and lightweight sheet of highly reflective material. When photons of light hit the sail and reflect back off it, they transfer some of their momentum to the sail, causing it to accelerate. Although the amount of momentum transferred by each photon is minuscule, it all adds up. Over time, lightsails can be accelerated to very high speeds – it is hoped that the Starshot probes will reach 20% the speed of light, which could theoretically cut the interstellar journey time down to just 20 years.

We could create tiny probes that contain all the necessary components for them to collect, send and receive data

Past experiments, such as the Japanese IKAROS project, have already proved that these solar sails work, but they take a long time to initially get going. Another focus of the Breakthrough project is to build an array of lasers here on Earth that can be aimed at the sail with pinpoint precision. These lasers would boost the sails with intense beams of photons, accelerating the probe to its target speed in a matter of minutes.

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Several experiments have already provided proof of concept that light sails, also called solar sails, can be an effective method of propulsion. Image credit: Josh Spradling/The Planetary Society.

The first steps of an interstellar journey

The technology to achieve all this either exists already or is realistically achievable in the near future. Although there are still significant challenges to overcome, the scientists and engineers of the Breakthrough Starshot program are already developing potential solutions.

Introducing the project on 12 April in New York, Hawking said “The limit that confronts us now is the great void between us and the stars, but now we can transcend it. With light beams, light sails and the lightest spacecraft ever built, we can launch a mission to Alpha Centauri within a generation.”

Stephen Hawking announcing Breakthrough Starshot

“Earth is a wonderful place, but it might not last forever. Sooner or later, we must look to the stars. Breakthrough Starshot is a very exciting first step on that journey” – Stephen Hawking. Image credit: 2016 Getty Images, Bryan Bedder.

“What makes human beings unique?” posed Hawking, during the announcement. “I believe that what makes us unique is transcending our limits.”

Maybe the stars won’t be out of humanity’s reach for much longer.


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And don’t forget to check out some of our other space articles:

Breakthrough Initiatives: the search for alien life 

Travelling through the universe

How LightSails work