I never thought I'd live to see this.
The Russian billionaire Yuri Milner, who last summer committed $100 million to boost SETI searches to a new level (Breakthrough Listen is now busily underway), announced on April 12th, along with a lineup of distinguished scientists, a new, far more ambitions $100 million project. Breakthrough Starshot will conduct research and development toward accelerating insect-size interstellar probes to 20% of the speed of light, driven by a 100-gigawatt laser array on Earth. The tiny probes would scout exoplanets up close — and report back across the light-years.
The "nanoprobes" would take only 20 years to get to Alpha Centauri, at least the ones that survive (a dust particle along the way would be fatal). As each zips through the system, a tiny camera and atmosphere analyzer are to grab pictures and data on any planets there. Then — hold on now — it would transmit this data the 4.4 light-years back to Earth using a "compact laser." The total mass of each probe, including power supply, camera, sensors, processors, fine-navigation thrusters, and that amazing transmitter, is to be just a few grams.
The laser array would boost this delicate snowflake of a thing out of Earth orbit with an acceleration of 25,000 gs, delivering the force to a lightsail purely as radiation pressure. It will have to do this without vaporizing the lightsail and the probe, which will have to be incredibly super-reflective. Such intense power is required to push the probe to its cruising speed in just two minutes, before it gets beyond good laser range. The lasers would then take a day to recharge their batteries (from a dedicated power plant), before sending off the next probe, and the next.
For years now, blue-sky engineering analyses of the sort that I've seen presented at science-fiction conventions have concluded that while this technology is rather beyond us at present, it could come into reach if Moore's Law continues and if materials science and ultra-micro manufacturing develop as hoped. And if lasers keep getting more powerful and cheap. Milner's $100 million will go toward investigating whether all of this can be made to happen.
Milner says his team has looked into “20 challenges” facing engineers. “Each one could have been a deal breaker, but it looks like we found a reasonable path forward for each.”
If such a system becomes possible it might cost $10 billion to build, suggests Breakthrough Starshot's impressive roster of experts. That's in line with the biggest big-science projects today. Once everything is up and running, the launches themselves would be cheap: maybe $100,000 each.
At this point there's really nothing more I think I should say. You can read heaps of news coverage; start with the New York Times, which was super-quick off the mark, and continue with The Atlantic's interview with Milner. For technical information to geek out over, and the case for plausibility, you want the Breakthrough Starshot website.
Milner says such a system might be ready to fire off its first interstellar probes in 20 years (I'd multiply that by 10, myself). Considering the travel time for the probes and for the returning data, Milner says he hopes to see the first closeups of any Alpha Centauri exoworlds in his lifetime. He's 54.