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.
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.
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.
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.”
“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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