How Starshot will get us to Alpha Centauri in 20 years

16 Aug 2016

Travelling into the darkest depths of the universe could soon be as easy as flicking on a switch, or at least a switch for a giant laser system that will fire a spacecraft at 150m kmph to Alpha Centauri.

Back in April 2016, the philanthropic research group Breakthrough Initiatives announced it was putting millions of dollars into developing a spacecraft capable of reaching Alpha Centauri in the next 20 years.

This would be some claim given that, despite it being our nearest neighbouring star, it’s located more than four light years away.

To put this into perspective, it took NASA’s New Horizons craft nine years just to travel to the outer reaches of our solar system at a record speed for human-built spacecraft.

In the amount of time it took to get from Earth to Pluto, Pluto was downgraded to a slightly less significant dwarf planet.

After all, it’s easy to forget that, since the launch of Sputnik in 1957, space agencies have been using the same method of chemical propulsion for decades now with very little change.

While a tried-and-trusted method of propelling us away from the Earth’s gravity, it does little to offer hope of us expanding outside of our solar system within a human’s lifespan.

Alpha Centauri B

An artist’s impression of a planet orbiting the star Alpha Centauri B. Image via ESO/L. Calçada/Nick Risinger

Nuclear power not an option

This, despite the fact that, during the height of the space race in the 1960s, the world was experiencing an atomic revolution where everything from cars to bomber aircraft were being designed with nuclear-powered engines in mind.

Unsurprisingly, spacecraft were no different and plans were drawn up to use nuclear power to go into space even faster.

Proposals ranged from nuclear fusion (which we still haven’t cracked), to exploding nuclear bombs over and over again to propel the craft forward, as proposed by theoretical physicist, Prof Freeman Dyson.

To overcome these challenges, from a new perspective, Breakthrough Initiatives brought together some of the best-known names in astronomy, including Prof Stephen Hawking, to put forward $100m worth of research into the design and testing of a revolutionary spacecraft programme called Starshot.

Rather than relying on the brute force of burning chemicals to get it into the depths of space, Starshot would harness the power of light itself to send thousands of miniature spacecraft at a speed of 20pc of the speed of light, or 150m kmph.

The man who stared at goats

No other spacecraft has ever achieved what Starshot aims to do with a series of focused laser beams.

Where else would such monumental first steps to bring this potentially revolutionary space technology to the world begin other than on a goat farm.

“In December 2015, I got a phone call when I was actually away from Harvard [University] visiting Israel with my wife and she said, ‘Why don’t we go to a goat farm for the weekend?’,” recalled Prof Avi Loeb, renowned theoretical physicist and chairperson of the Breakthrough Starshot Advisory Committee, who is one of the scientific leaders of this incredible technology.

Not long after they arrived, Loeb got a call from Breakthrough Starshot’s executive director, Pete Warden, asking him to file a report on the initial findings of whether such a project was feasible.

“I said okay, but at the goat farm there was only internet in the office and I sat with my back to the wall at 6am in the morning looking at the goats and making up this presentation that I later delivered,” he said with incredulity.

“It was bit surrealistic to look at the goats, and I bet the owner of the goat farm never imagined that the first realistic plan to go interstellar was contemplated at that farm!”

 Building a laser array

So, why Alpha Centauri? Well, at least according to Hawking, it presents the best challenge to humankind.

“The limit that confronts us now is the great void between us and the stars, but now we can transcend it”, he said during the mission’s announcement.

“Today, we commit to this next great leap into the cosmos. Because we are human, and our nature is to fly.”

While humans will not be flying to Alpha Centauri, the team led by Loeb concluded that the fastest way to send an ultra-light craft from Earth is to use a laser array system.

This won’t be any typical laser we see in general photonics, but rather a kilometre-wide laser array built on Earth capable of producing 100GW of energy focused on the nanocraft in space.

By generating the same power as an old NASA space shuttle during take-off, these nanocraft, which weigh just one gram, will be capable of achieving a necessary speed of around 20pc of the speed of light.

By creating such a structure here on Earth, it would quickly become one of the most challenging engineering projects ever undertaken as with such capabilities comes great challenges.

Aside from constructing and operating such a large array of powerful lasers, a number of challenges arise in trying to send the nanocraft on their long journey.

Perhaps the most challenging will be ensuring atmospheric interference does not limit the crafts’ abilities to achieve high speeds and maintain contact with the scientific crew on the ground.

The same issue will exist for the 20 years the craft will be sailing across the four light years of space that could find them heading into troublesome cosmic dust or gas that could interfere with the laser beam.

One option suggested by Loeb and the team was to build the array in space, eliminating fears of potential atmospheric disturbance.

Avi Loeb

Prof Avi Loeb speaking at the launch of the Starshot in April. Image via Bryan Bedder/Getty Images for Breakthrough Prize Foundation

Earth 2.0 lies in wait

However, the costs of doing this would be staggering, taking into account the cost of the International Space Station (ISS), which saw space agencies spend omore than €100bn on the enormous project.

In a quite timely piece of recent news, it’s expected that the European Space Observatory (ESO) is to formally announce the discovery of a new exoplanet within the Alpha Centauri system that would be ideal for supporting life.

Now, rather than sending craft out to prove we can travel to our nearest star, we can also send them to help us photograph and analyse a potential ‘Earth 2.0’.

One of Loeb’s colleagues on the Starshot project, Prof Phillip Lubin, described the potential discovery as “very exciting”.

“It makes the case of visiting nearby stellar systems even more compelling, though we know there are many exoplanets around other nearby stars and it is very likely that the Alpha Centauri system will also have planets,” he said.

A craft that costs less than an iPhone

Once the laser array conundrum has been solved, it will then come down to actually building these nanocraft and, more importantly, what will turn each of them into a miniature lab.

This is where StarChip comes in; the gram-scale nanocraft that carries a camera, photon thrusters, power supply, navigation and communication equipment and nuclear power supply, all for the price of an iPhone.

Whereas astrophysicists of old debated and debunked the thought of a nuclear-powered craft decades ago, they likely never thought nuclear power would one day provide the energy for such a low-energy craft.

“The cost of an iPhone is nothing [in terms of space travel], so if one of these things burns, who cares? It’s not much money and you didn’t risk human life. This was not feasible more than a decade ago,” Loeb said.

This risking of human life is something Loeb and many scientific thinkers have quickly concluded is not in the best interests of humanity.

Starshot sail

An illustration of Starshot in action. Image via Breakthrough Initiatives

Whereas NASA and other space agencies go to extreme lengths to make sure human missions to Mars and elsewhere are planned to absolute perfection, Loeb’s counterpoint is that it’s simply illogical to send us to the stars.

Citing the Starshot mission, Loeb points out that if we were to send a human mission to Alpha Centauri at a comfortable level of G-force – in our case 1G – it would take one full year to accelerate to a fraction of the speed of light.

In comparison, the lifeless Starshot nanocraft would take just a few minutes to reach a similar speed, but would be travelling at 60,000G, far more than a human can handle.

There is also the issue of keeping a human crew populated for decades and, as Loeb points out with a dash of humour: “How many times can you watch a movie?”

Icarus and the melting sail

That’s not to say that sending miniature spacecraft will be an easier challenge.

Loeb believes that the StarChip’s greatest challenge is its sail, which will be on the end of one of the powerful laser beams transmitted from Earth.

If it’s to withstand a 20-year journey, the sail will need to be made from the strongest of materials, otherwise, the mission will be a complete disaster.

“I’m worried about the sail melting, just like the wax melted on the wings of Icarus,” said Loeb. “You just need to absorb a very small fraction of the laser light for this to happen.”

Thankfully, there’s a potential solution to this problem.

“One [potential solution] is to use materials that either reflect extremely well or that have low absorption, coefficient for what the laser is operating,” Loeb said.

“One also needs to make the sail very sturdy and stiff so that it won’t bend in the solar wind.”

As touched on before, communication with the nanocrafts will also be crucial to the success of the mission, with it taking an estimated four years for scientific data and images to return to Earth.

Milky Way at night

The Milky Way captured at twilight from the Atacama Desert. On the plain of the Milky Way, toward left, the Southern Cross with the Coal Sack can also be spotted, followed by two bright stars, respectively Beta and Alpha Centauri. Image via G. Hüdepohl (

First stop: solar system

While still very much at concept stage, $100m has already been spent on a feasibility study of the Starshot programme, with help from one of its largest philanthropic funders, billionaire Yuri Milner.

If the idea is to, literally, take off, it’s envisioned that it will cost in the region of $10bn, putting it in the same league as other major space projects like the James Webb Space Telescope, which is expected to launch in 2018.

But before Breakthrough Initiatives can begin its mission to Alpha Centauri, Loeb agreed that, in the meantime, the solar system offers a much more achievable testbed.

If it can travel over four light years in 20 years, surely a flight to Jupiter, Neptune or even Pluto would take a fraction of the time it currently takes?

“I actually think that a search within the solar system would be an intermediate step and this could revolutionise [near-Earth] studies,” Loeb said.

“So, for example, going through the plumes of Enceladus, we could analyse the jets or geysers coming out from the surface of Enceladus, one of Saturn’s moons.”


A powerful plume on Enceladus captured by NASA’s Cassini spacecraft. Image via NASA/JPL/Space Science Institute

More craft means more chance of discovery

These nanocraft are durable – but disposable enough – that flying them into these gas plumes could determine the moon’s molecular composition and possibly find the lingering fingerprints of molecular life.

Loeb added that the fact multiple craft are launched at one time means that multiple scientific missions can be conducted at one time in our solar system, resulting in a much-faster turnaround, never before seen in astronomy and astrobiology.

Concluding on a high note, Loeb said that this scattergun approach of launching thousands of craft in the universe will ultimately offer us the best chance of finding intelligent life out there in the universe.

Not due to the chances of one of the craft picking up a signal or evidence of extraterrestrials, but rather that something in the vastness of space would have a much better chance of finding us.

“I think if we just wait a few centuries, our civilisation would send so many devices into space that [Earth’s] biggest [celestial] signature would be those devices.”

Let’s hope someone, or something, out there is listening.

Colm Gorey was a senior journalist with Silicon Republic