Free Astronomy Magazine May-June 2016

ASTRONAUTICS ing each miniprobe. This is explained by considering that the miniprobes will be pro- duced on an industrial scale, expected in hundreds of thousands of samples. The reason why thousands of miniprobes will be launched towards each destination can be easily guessed: the majority of them will not arrive unscathed at the end of their journey. Besides possible failures and mal- functions, many will end up destroyed by impacts with the matter present on their path. The inter- stellar space is not empty, as appear- ances would have us believe, but fil- led with dust and gas, although at a very low density. The impact of a probe with a grain of dust at 50,000 km/s relea- ses the same energy as the ex- plosion of a stick of dynamite; more than enough to destroy a manmade ob- ject weighing only a few grams. Indeed, for damaging the miniprobe is sufficient an im- pact with a hydrogen atom, that at that spe- eds has the effect of a cosmic ray, which will not certainly improve the performance of its microelectron-ic components. After having travelled 4.4 light-years (40 tril- lion km) in twenty years at a speed 4,000 times greater than that of New Horizons, and after having avoided all possible dan- gers, any surviving Starshot’s miniprobes will arrive in the Alpha Centauri system, which consists of two stars similar to the Sun, rather close to each other (Alpha Cen- tauri A and B), and of a more isolated red dwarf (Proxima Centauri). Once there, their photo cameras and various scientific instruments will go into action, ga- thering as many images and data as possible during the flyby time span (a few days). At present, there is no certainty that there are planets around these stars, but if so, one or more miniprobes may be able to photo- graph them and gather some information on their properties. All the collected scien- tific material will then be transmitted to Earth via a very compact laser communica- tions system, powered (like other devices of each miniprobe) by a radioisotope battery. The various signals will be received after a further 4.4 years by the same light beamer that nearly a quarter of a century earlier was used to accelerate the miniprobes. The Breakthrough Starshot team is aware that there will be many problems that will need to be solved before reaching the ope- rational stage and various pitfalls through- out it, but they are very optimistic, ready to overcome every obstacle and launch the first miniprobes towards the Alpha Centauri system within 20 years. Since the estimated $10 billion needed to implement the project is not coming from our pockets, it costs us nothing to go along with it. n R ight, image roughly show- ing the laser beam pushing the Light- sail. The video below summa- rizes the minipro- bes’ acceleration procedure. [Breakthrough Foundation]