Boldly going to Alpha Centauri?
A theoretical physicist, the creator of Facebook, and a Russian Billionaire walk into a press conference. Next thing you know, the internet is abuzz with the talk of an interstellar mission, wherein we puny humans will attempt to fly a teeny-tiny space craft roughly 25 trillion miles to our nearest stellar neighbour, Alpha Centauri.
This ambitious project is the latest to be funded by the new Breakthrough Initiatives scheme, funded by Mark Zuckerburg and Yuri Milner. Last year, they announced $100 million in funding to listen for signs and messages from extra-terrestrial life, by conducting a radio survey of 1,000,000 stars and 100 nearby galaxies. This year, they lined up in New York alongside Cambridge Physicist, Stephen Hawking, to announce their latest venture: a $100 million project to send a space probe to the Alpha Centauri star system inside of a generation. The project is named Starshot, and in a nutshell (which is approriate, given the size of the space probe), it will fire a huge array of powerful, Earth-based lasers at a tiny space probe attached to metre-wide light sails, accelerating the teaspoon-sized nanocraft to a speed of 100 million miles per hour. This relativistic velocity means we could see Starshot arriving at our interstellar neighbour within 20 years of launch.
Once Starshot arrives, it's onboard cameras and scientific equipment would snap a bunch of pictures, and take a bunch of data, and send it back to us (a process which will take 5 years) all while whizzing past the system at 100 million miles per hour (there's no slowing it down once it gets there). In that respect, it's something like an interstellar New Horizons mission. That Pluto fly-by mission only had to travel 3 billion miles, but even that took 9 years. At the size of a baby grand piano, New Horizons is much more massive than the proposed Starshot probe, which will only weigh a couple of grams, making it 'simpler' to accelerate to the ridiculously large velocities required for a beyond-the-solar-system mission.
So far, so very exciting! But, how feasible is this in practice? I mean, we're talking about making huge leaps and bounds in current technology if this interstellar dream is to become a reality. There have been a few nice articles written that scrutinise some of these issues, such as this Forbes piece, and Rachel Feltman's WaPo article. The main issues? Well, for a start, it's going to cost significantly more than $100 million to bring such an ambitious project to fruition. But, that's ok. The Breakthrough Initiative is largely aiming to fund the research into making the technological leaps necessary. And the main challenges faced are:
1) Building a BIG ASS LASER ARRAY, capable of pumping out a burst of energy equivalent to 100 gigawatts in 2 minutes, to propel the nanocraft to the necessary, record breaking speeds required. As the Forbes article points out, that's about 10% of the U.S. midday total energy demand. In the event that these lasers go ahead, you might want to power down your computer while they're being fired, in case of a blackout :)
2) Making a TINY ASS NANOCRAFT. The little wafer-craft that Breakthrough are planning on building will require that Moore's Law (the idea that computer processing power doubles every year) continues to remain true for another decade, at which point fitting everything you need for an awesome space mission into a craft that weighs only a few grams becomes plausible. As Feltman points out in WaPo, it's not certain that this continued improvement in processor power is sustainable. In which case, the nanocraft may yet be decades away.
3) Planning a fly-by to a star 4.76 lightyears away is going to be difficult. At that distance, you basically can't communicate efficiently with your spacecraft. Round-trip communication will take ~ 10 years, which is ~ half your mission. So, unlike New Horizons, you won't be able to change any of your data collecting plans on the fly. Everything will either need to be meticulously pre-planned, or you're going to want some kind of onboard AI that can scan Alpha-Centauri as it approaches the system, and decide what the best way to study it is. So... yeah. TRICKY.
So, realistically, how excited should we be about getting sent images taken around another star within our lifetimes? Forbes reckons it will be at least 2060 before such an ambitous mission delivers the goods, by which time I'll be approaching 80. But, even if it takes longer, and I never get to see a bunch of pictures of smiley-faced (or pitch-fork-wielding) Alpha-Centurians, I'm still excited. This kind of blue-sky-thinking, exploration-minded initiative is bound to push forward a bunch of different technologies that will change our everyday lives, and probably help us do more amazing science within our own little solar system. So, I look forward to seeing what comes from Starshot. It could be anything... ;)