If you are going to launch a photon ultracompact spacecraft through the entire galaxy, capable of developing 1/5 of the speed of light, then, of course, you should think about how this device can be stopped when it reaches its destination. Approximately such thoughts now revolve in the brightest minds of modern astrophysics. Scientists are pondering over how the project of Breakthrough Starshot, which was announced last year by Yuri Milner and Stephen Hawking, could be implemented.
If you forget, we will briefly recall: the Russian billionaire Milner and the American theoretical physicist suggest sending a tiny spacecraft the size of an ordinary brand to the nearest star system, Alpha Centauri, located at 4.37 light-years on the Earth. The launch is proposed to be carried out with the help of a powerful laser beam, which will accelerate the device to 1/5 the speed of light.
However, astrophysicist Renee Heller of the German Max Planck Institute for the Study of the Solar System believes that despite the fact that Alpha Centauri is the closest star system to us, it is not at all necessary that the journey to it will be the fastest. Heller and his colleagues suggest instead of Alpha Centauri to visit Sirius – the brightest star in the night sky – and they say that in fact the flight there will be much faster, even though Sirius is almost twice as far away from us (about 8.6 Light year) than Alpha Centauri.
But how can such a flight be faster if Sirius is further away? The answer lies in various hypotheses about how to accelerate, and then slow down the speed of this tiny (and still only hypothetical) spacecraft.
Within the framework of the project Breakthrough Starshot in the direction of Alpha Centauri with a speed of up to 20 percent of the speed of light is planned to send a miniature space probe. In theory, this speed will achieve the desired destination in just 20 years. However, the main problem in all this extremely ambitious project is that at such a crazy speed the possibility of stopping the device seems extremely unlikely. In other words, now the mission to Alfa Centauri is considered exclusively as a “fly-through”, with the lack of the possibility to conduct any really important research from the scientific point of view of this system.
Of course, with this scenario, the candleworm is not worth it, especially if you consider that Alpha Centauri is home to the closest exoplanet Proxima b. Despite the fact that scientists are still fervently arguing about its habitability potential, the planet really is of great interest to science.
Heller and his colleagues earlier this year proposed an alternative option for the mission to Alfa Centauri, saying that instead of lasers that would accelerate the spacecraft to the desired speed, it is better to use a different type of spacecraft. The researchers proposed to pay attention to the concept of their spacecraft using a solar sail. To accelerate such a space probe in the direction of Alpha Centauri will be the energy of sunlight.
Upon reaching the destination, the sail will allow the vehicle to be braked using the emission of Alpha Centauri stars. The idea is actually quite interesting, but it has one serious drawback – speed. When using a solar sail, under no circumstances will it be possible to accelerate the device to 1/5 the speed of light, and therefore the total time of its flight to the desired star will increase several times. According to preliminary calculations, the flight and exit into the orbit of the star Proxima Centauri (the native star of the planet Proxima b) will take about 140 years. It sounds, you will agree, less impressively against the background of the promised 20 years.
“One of the most important pre-defining motivators of the Starshot project is that a visit to Alpha Centauri will be possible during our lifetime,” commented in February this year Avi Loeb, astrophysicist at Harvard University and chief scientific consultant of the concept of Breakthrough Starshot.
However, Heller’s team revised its original hypothesis and now says that the “optimization” of the mission can significantly increase the efficiency of acceleration and speed reduction when using a solar sail. True, this idea does not work with Alpha Centauri, but on the sight you can take a brighter star Sirius – it is 16 times brighter than Alpha Centauri – and in the end, according to their calculations, reduce travel time to about 69 years. The new idea of the Heller group has not yet been published for critical analysis, but the same Loeb considered it “very innovative and interesting,” while noting that to implement this plan will seriously revise the technology of solar sail.
“To work, that is to achieve the necessary speeds, this concept will require the use of a very thin sail,” – commented Loeb.
Heller and his team agree with this opinion, but at the same time explain that if scientists manage to find a way to create the right version of a huge, but ultra-thin sail, then humanity can enter the era of interstellar flights.
“We need a very light, very strong, resistant to extreme temperatures and very reflective material for the production of a sail, which can be opened on an area of several hundred square meters,” explains Heller.
“If we find such, humanity will become an interstellar species.”