Earlier this week we heard the announcement of a new project from the “Breakthrough Initiatives”. The group is led by Yuri Milner, a Russian entrepreneur apparently named after Yuri Gagarin, along with Stephen Hawking and Mark Zuckerberg, and with support of an advisory panel of astronomers, theoretical physicists, space scientists, engineers and business leaders. The new initiative, Breakthrough Starshot, has the goal of sending a fleet of tiny spacecraft to the nearest star system. It gathered a fair bit of attention, at least for 24 hours—BBC Radio Wales even asked me to chat to them about it on Good Evening Wales.
They are quite clear that their goal is to develop the technology required for interstellar travel, not simply a mission to Alpha Centauri. It was commented in the launch press conference (which you can rewatch here) that targeting a single mission is one mistake the Apollo Programme made—after landing on the Moon there was nowhere to go.
Another major problem the Apollo Programme made was the dependency on political will, which changes with the wind, typically on a timescale of less than a decade. That is something that should be surmountable with significant private investment. But it isn’t cheap. The estimate they put on it is $5-10 billion over a 20 year development programme. Compared with Apollo, which cost the equivalent of $110bn in today’s money, that’s not a lot, but given that they have about $100m so far (from Yuri Milner), they have a long way to go.
The mission concept
The mission concept is to send many (possibly thousands) of tiny spacecraft to another star system – probably Alpha Centauri, since that’s the closest one to ours. It’s still a long way away, though, at around 4 light years. It would take a conventional spacecraft (e.g. one of the Voyager spacecraft), launched on a conventional (chemical) rocket, tens of thousands of years to get there. Breakthrough Starshot has three mechanisms for overcoming these problems.
The tiny spacecraft itself would be truly tiny – basically just a tiny chip around a centimetre across and weighing about a gram. The project claims to have a prototype, containing a computer, camera and communications – though whether it’s space qualified I’m not sure. One reason spacecraft have relatively slow computers and low-res cameras compared to consumer products here on Earth is that they have to be resilient to all sorts of harsh conditions, such as large temperature variations and – most importantly– high energy cosmic rays which can hit a chip and either corrupt its memory or damage it irreversibly. That’s one argument for sending thousands of these things — many would fail en route, but some would make it.
Rather than using a chemical rocket to accelerate, these spacecraft would carry small light sails. These are very thin, lightweight sails of reflective fabric, which work by the principle of conservation of momentum. When a photon of light is reflected off the sail, it imparts a small amount of momentum. A lot of photons means a lot of momentum, and if the sail (and attached SpaceChip) is small enough, they can accelerate up to high speeds. This technology has been tested by a number of space agencies, including NASA and JAXA (the Japanese space agency), with the sails using sunlight for propulsion. These have been much larger, so there will need to be development in making much smaller versions.
The Light Beamer
Rather than using the sunlight, which would accelerate the spacecraft relatively slowly, Breakthrough StarShot plans to use a hugely powerful laser here on Earth to propel it. They calculate that a 100 GW laser could propel the StarShips and their LightSails to 20% of the speed of light (60,000 km/s, or 130 million mph!) in just a couple of minutes. That speed reduces the journey time to Alpha Centauri to just 20 years—considerably shorter than the tens of thousands of years it would take with current technology. The huge power also means that the LightSails have to be completely reflective, as if they absorb even a tiny fraction of the power the heat would destroy them.
I have to admit that I’m not 100% convinced by their calculations—I work out that a 1 gram spacecraft would need to absorb the full 100GW for 2 minutes to reach around 20% the speed of light – if the laser were propelling a lot of spacecraft then this speed would be reduced considerably. Maybe I’ve misunderstood something about what they’re proposing
This seems to be the area that needs most development. Lasers this powerful do exist, but tend to be on for a tiny fraction of a second. There are other industries that need powerful lasers, though, so the technology is constantly improving. It probably wouldn’t be a single laser, but several combined lasers—not unlike the Death Star in principle, but very unlike the Death Star in practice (light doesn’t bend corners like that without some sort of optics!). Presumably lots of lasers converging on a large telescope mirror to beam them through space.
To get the lasers through the Earth’s atmosphere would need some serious adaptive optics technology, way beyond that used in ground-based telescopes today. Again, that technology is being delivered by other industries (and probably the military) so it might get there.
The LightBeamer is also meant to be the means of communicating with the Earth, as the same focussing optics would act as a telescope.
Will they succeed?
I’m not sure whether this is feasible, certainly on the timescales involved. If the goal is to push people into thinking about the technology development, then I guess that’s an achievable (if vague) goal. I’m not convinced it’s achievable on a 20 year timescale, but it’s technology that it’s almost inevitable we’ll get at some point. I’m also not convinced that it all points to a 20 year mission to Alpha Centauri, possibly by a factor of a few thousand in duration!. The corollary to the argument that Apollo stalled because there was no long-term programme is that it succeeded because of a clear goal. The project is also has a much longer lifetime than the careers (and probably lives) of most of the advisory board, most of whom are past, or nearing, retirement age. Maybe that’s why Mark Zuckerberg is on board (young blood!)…
The cynic in me also says that this could all be a publicity stunt. On the other hand, it’s exciting to be able to think about this near-future technology.