How Breakthrough Starshot will reach interstellar space
Discover the million-dollar project taking us further into space than ever before
To date, we’ve done a pretty good job of exploring the Solar System. But in our half a century or so as a space-faring species, we have not yet truly ventured to any of the 100 billion stars in our own galaxy, or beyond. In 20 years, though, that could all be set to change.
“Sooner or later, we must look to the stars” Stephen Hawking
On 12 April 2016, Russian billionaire Yuri Milner announced an ambitious project as part of the Breakthrough Initiatives to send a series of small spacecraft to the nearest stars to our own Sun, the Alpha Centauri system. And he wasn’t alone; alongside him at this announcement were respected scientists, including Stephen Hawking and Kip Thorne, who have all signed up to help with the project. “The human story is one of great leaps,” said Milner. “55 years ago, Yuri Gagarin became the first human in space. Today, we are preparing for the next great leap – to the stars.”
So, what’s it all about? The project is known as Breakthrough Starshot, and it is utilising an oft-touted – but little explored – technique known as laser sails to reach tremendous speeds, and make a trip to another star possible in as little as a generation.
“The human story is one of great leaps,” said Milner. “55 years ago, Yuri Gagarin became the first human in space. Today, we are preparing for the next great leap – to the stars.”
You’ve probably heard of solar sails before. These are sheets of thin material that expand to massive sizes in space. Like a wind sail on Earth, these sails then pick up speed not from regular wind, but solar wind, the stream of particles given off by our Sun. The rate of acceleration is very slow but over time, a spacecraft could theoretically reach a significant fraction of the speed of light.
This proposal is slightly different, though. Instead of using solar wind, the team is proposing to fire giant lasers on Earth at sail-mounted spacecraft. These spacecraft, known as a StarChips, would have several instruments packed into them, but be small enough to fit on the palm of your hand, thanks to huge advances in techology. The sail itself would be larger, spanning a metre, although just a few hundred atoms thick. Theoretically, shining a 100-gigawatt laser on one of the sails should accelerate the spacecraft to 20 per cent of the speed of light – or 216 million kilometres per hour – in minutes.
In hours, the spacecraft would reach Mars, a journey that takes several months for conventional spacecraft powered by chemical fuels.
At these speeds, traversing the Solar System would be a breeze. In hours, the spacecraft would reach Mars, a journey that takes several months for conventional spacecraft powered by chemical fuels. In three days, it would reach Pluto, which took New Horizons almost ten years to reach. Most importantly, in 20 years, the spacecraft would reach Alpha Centauri, 4.37 light years (40 trillion kilometres) away.
One of the main reasons for going to Alpha Centauri – which is actually a triple system made of three stars – is that it’s the closest star system to our Sun. We now think that almost every star plays host to at least one planet, and Alpha Centauri A, B and C should be no exception. The goal of the mission would be to study these planets, returning images and priceless data to Earth. Owing to the distance, this information – travelling at the speed of light – would take 4.37 years to make it back. But a total of less than 25 years for such data is pittance, considering the implications.
“Earth is a wonderful place, but it might not last forever,” Stephen Hawking said in a statement from Breakthrough Starshot. “Sooner or later, we must look to the stars. Breakthrough Starshot is a very exciting first step on that journey.” So far, so good. But this is just scratching the surface of the technical challenge of this hugely ambitious project. We’ve never sent a spacecraft beyond 240,000 kilometres per hour before; the StarChip would travel almost 1,000 times faster. There will be a huge number of unknowns of accelerating to and travelling at these speeds. How the spacecraft will hold itself together during the intense acceleration phase, and how it will communicate with Earth at great distances, will also need to be resolved.
“Breakthrough Starshot is a very exciting first step on that journey.” Stephen Hawking
Breakthrough Starshot, therefore, is a bid to overcome such hurdles. Milner is investing $100 million of his own money, but he readily admits that this is merely seed funding. The final cost of the mission could spiral into the billions of dollars, and he is hoping for funding from a number of sources in order to support the project. As such, there is no definitive launch date yet, although some time in the next couple of decades is not unthinkable.
One way to overcome some of the challenges facing the project will be to send not just one spacecraft, but to launch a ‘mothership’ with thousands of StarChips on board. All of them would be released in orbit, where the powerful Earth-based laser would shine upon them, firing them off in the direction of Alpha Centauri. Think of this mission not as a single man-made vehicle making a lonely journey, but an entire fleet venturing off into the cosmos.
If it works, this form of propulsion could prove invaluable. Not only would it let us reach Alpha Centauri in 20 years, but it would also let us explore destinations closer to home, such as the Moon and Mars, in a tiny fraction of the time that is currently possible. Imagine if, on a regular basis, scientific organisations from around the world could send their own prospecting spacecraft to places all over the Solar System, letting us frequently explore worlds closer to home, rather than sending a mission every few years or so.
Think of this mission not as a single man-made vehicle making a lonely journey, but an entire fleet venturing off into the cosmos.
Once the spacecraft reached Alpha Centauri, they would not stay for long. Owing to the method of travel, this would very much be a one-way trip. The spacecraft would merely fly by any worlds we discover, snapping as many images as possible and gathering data. They may also collect information on the atmospheric composition of the planets, their temperature, their rotation rate, and so on.
As for Alpha Centauri itself, the system may hold invaluable secrets. At the moment, we’re not actually sure if any of the three stars host planets. Previous detections have since been ruled uncertain. But it’s fair to assume there are probably some planets in orbit, considering two of the stars are similar to our Sun. We know all stars form in a debris of dust and gas, a planetary disc, which often gives rise to planets. It’s hoped the same would be true of Alpha Centauri.
Initially, astronomers had thought that there was a planet orbiting in the desirable habitable zone of one of the stars, Alpha Centauri B, an orbital position that is not too hot nor too cold, where liquid water is able to form on the surface. The nature of whatever planets are there still remains uncertain, but the chances that one might be habitable are indeed fascinating.
For decades now, we have been looking for worlds beyond our own that are Earth-like; that is, they have the necessary conditions to host life. After all, we are just one planet orbiting one of 100 billion stars in one of 100 billion galaxies. It seems unlikely that ours is the only planet teeming with life. But so far, finding planets exactly like our own has been difficult, owing to the limited methods of detection we currently employ. However, if we could send probes to a potentially habitable world around Alpha Centauri, we may be able to discover if our planet really is unique – or if there are many others like it. Imagine images being returned of a glorious alien world abundant in water, clouds or perhaps even vegetation. Such a discovery would no doubt change life on Earth forever, with untold money being pumped into missions to find more worlds like our own – and even visit them. For now, the project is in its infancy, and these dreams are at least 40 years away. But perhaps we’ll soon make the first steps to becoming a truly interstellar species, and discover our place among the stars.
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