Free Astronomy Magazine May-June 2016

ASTRONAUTICS through Starshot, in- volves the construc- tion of large fleets of super lightweight miniprobes to be sent towards nearby stars. The individual mini- probes, accelerated by the radiation pres- sure of a highly in- tense laser source, could reach in a few minutes the incredi- ble speed of 50,000- 60,000 km/s (200 mil- lion km/h), i.e. a sub- stantial fraction of the speed of light. With such a speed, these miniprobes could pass the orbit of Neptune in just one day! As incredible as all of this might appear at first sight, the technology on which Break- through Starshot intends to rely on is already available or will be available within a few years, if technological development will pro- ceed at the expected pace. Thanks to the adoption of increasingly miniaturized elec- tronic components and extremely light- weight and resistant materials produced through nanotechnologies, each probe will weigh no more than a few grams and will be comprised of two main parts. The first, called StarChip, is wafer-bonded and it will have the size of a postage stamp, and it will contain everything that typically goes into an in- terplanetary probe, including recording cameras, obviously miniaturized in this specific case. The second part, called Lightsail, will basically be a sail a few meters across, with a thickness of a few hundred atoms (thus made with meta- materials) and with a reflec- tance close to 100%. The lat- ter property will be crucial for rapidly accelerating the mini- probes through a laser beam. In fact, if the incident ener- gy on the sails were to be ab- sorbed above a critical limit, the miniprobes would end up vaporized. Their design does not however seem to worry the several engineers involv- ed in the Starshot project. More challenging is instead the construction of the propulsion system, i.e. a large array (kilometres) formed by thousands of optical elements (lasers) of one or more metres each in diameter, necessary to produce the laser M ilner shows to the au- dience the size that the minipro- bes’ StarChip com- ponent will have. [Bryan Bedder/ Getty Images]