German astronomers talked about the possibility of flying to Alpha Centauri, the closest star to us, in just 140 years and returning back in about the same time using a giant light sail with an area of two pyramids of Cheops, according to an article published in the Astrophysical Journal.
“This sail can be made from graphene - an extremely thin, lightweight and yet very strong carbon film. It has yet to be made and coated with reflective material, but many of the greatest accomplishments in human history have been made possible by overcoming insurmountable obstacles. In the near future, we may enter an era when humanity will leave its star system and begin to study exoplanets using such probes,”said Rene Heller of the Institute for the Study of the Solar System in Göttingen, Germany.
Star Cloak vs. Star Sling
In April 2016, renowned British cosmologist Stephen Hawking and Russian billionaire Yuri Milner spoke about their next "space" initiative within the Breakthrough Initiatives series - Breakthrough Starshot. As part of it, the oligarch allocated $ 100 million to create a spacecraft based on an idea outlined by Californian physicists led by Philip Lubin last year.
Its essence is to send not classic spaceships to distant planets, but extremely light and flat structures made of reflective material, which will be accelerated to near-light speeds using a powerful orbital laser.
Such an interstellar "sailing ship", according to the calculations of American physicists, will be able to reach Alpha Centauri in 20 years, and will fly between Mars and Earth in just three days without a payload and in a month with a load of 10 tons. The main problem in both cases will be the deceleration of the probe - while the team that came up with it has no idea how to make the stop of the laser "sailboat" safe.
For this reason, the participants in the Breakthrough Starshot project plan to carry out this mission similarly to the approach of the New Horizons probe with Pluto: a fleet of microscopic star "sailboats" launched by lasers will simply fly past Alpha Centauri and try to send its photographs to Earth.
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German alternative
Two famous German astronomers, Heller and Michael Hippke, offer an alternative travel option to Alpha Centauri, which will take longer, but will allow 10 times more cargo to be sent, to orbit this triple star system and, if desired, go back to Earth.
The key to this task is a giant solar sail with an area of about 100 thousand square meters, made of ultra-light material - graphene, nanotube fibers or other "flat" substances. According to the calculations of Hippke and Heller, a similar structure, equivalent in area to two Cheops pyramids or a dozen football stadiums, can accelerate a microprobe weighing 10 grams to a speed of about 20% of the speed of light.
Such a sail could reach Alpha Centauri in about 90 years, approaching Alpha Centauri A, the largest star in the system, at a distance of about 4.4 million kilometers. At this moment, as scientists explain, the probe must reduce its speed of movement to 4.6% of the speed of light, otherwise it will fly past the star and cannot use its attraction and light to slow down its movement and turn towards the other two inhabitants of the system.
How to implement such inhibition? To do this, you just need to turn the solar sail in such a way that it is not pressed by the light of the Sun, but of the Alpha Centauri. After the maneuver is complete, the scientists plan to deploy the sail and use the light from Alpha Centauri B to travel to Proxima b, the planet near Proxima Centauri. This process, according to scientists' calculations, will take about 46 more years, and 140 years after the launch from Earth, the probe will enter the planet's orbit.
The main question of space
Why is all this necessary, given the super-long travel times of such "sailing ships"? As noted by Hippke, in fact, such mission periods are not something particularly long and atypical for earthly astronautics - for example, Voyager probes in total spent only half the time of this expedition to Alpha Centauri in space.
Unlike Breakthrough Starshot, these 10-gram probes will contain much more scientific instruments and have a much higher chance of success than a swarm of laser-launched nanoprobes, he said. Therefore, German scientists propose to consider their project as a fallback or "supplement" to the mission of Hawking and Milner, if it fails or, conversely, gives extremely interesting results.
Today, Hippke and Heller, according to the University of Puerto Rico in Arecibo, are negotiating with representatives of Breakthrough Starshot about the possible integration of their project into the long-term plans of the Milner Foundation. As an alternative, they propose to accelerate Breakthrough Starshot nanoprobes using the Sun, launching them into space at a short distance from the star, rather than using an expensive and potentially dangerous for probes phased laser.
