There are billions of worlds in the galaxy like ours. Do we need to send the embryos of life to them in order to spread it throughout the cosmos? Claudius Gross from Goethe University in Frankfurt, Germany, thinks it should. To do this, he suggests using ships with laser propulsion systems, which are technically quite possible to assemble now. The same Breakthrough Starshot project has ambitious goals for using such systems to send tiny light probes to Alpha Centauri. The scientists behind it want to take pictures of the star closest to us, but, according to Gross, such systems could well put a much larger load into the orbit of this very star.
Potential targets include a planetary system near TRAPPIST-1, a red dwarf star just 40 years from us. At the beginning of this year, astronomers figured out that it was home to seven solid planets, three of which orbit within the star's potentially habitable zone.
Starshot's supposed 20-year mission to the nearest star other than the Sun relies on an ultralight craft capable of accelerating to 20 percent the speed of light from giant lasers on Earth that will point to a light sail - essentially a mirror surface. Despite enormous difficulties, especially in the design of lasers and the reflectivity of the laser sail, engineers are confident that such a mission is possible.
"It's a matter of willpower to do that," says Chi Thiem Hoang of the Canadian Institute for Theoretical Astrophysics. However, unable to slow down, the single-shot Starshot would simply whistle past the target star system hours after arrival.
Genesis project
Can laser thrust put a heavy, slow-moving cargo aboard a braked ship into orbit? Gros says he can - and should.
His interest in interstellar travel is neither scientific nor exploratory. He wants to spread life.
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“These kinds of projects are useless for humanity, but life has value and should be able to develop on other planets,” he says.
Gros is filled with excitement at the thought that planets orbiting the most common types of stars in our galaxy, red dwarfs like TRAPPIST-1, may have ancient, oxygen-rich atmospheres. While this would make them potentially habitable today, they would also prevent life from forming naturally due to the oxidation of prebiotic organic chemistry.
“Our galaxy could have a billion sterile but habitable worlds,” he says.
In his proposed Genesis project, Gros sees the possibility of sending autonomous life tools into space: miniature versions of gene laboratories that scientists are trying to create on Earth. They will grow genes and cells from chemical ingredients and spread across habitable worlds.
How to slow down a heavy load upon arrival? It is proposed to use sails, but instead of a specular application, they will be magnetic fields extending for kilometers and transmitting the pulse of the probe to interstellar particles that hit it. Once the lasers used for launching stop pushing the sails, they can use the cosmic dust to slow down.
Magnetic sail
Deep space can be practically empty, containing an atom per cubic centimeter, so sails with a large surface area will be needed. According to Gross, the latest high-temperature superconducting wires are fine - they can transfer energy with little or no loss at temperatures just above absolute zero. They could be used to create magnetized sails large enough to stop a heavy craft.
Gross simulated interstellar particles hitting a magnetic sail and found that successful braking was determined by four parameters: the mass of the spacecraft, its speed, the radius of the sail, and the current flowing through the loop of the superconducting loop inside the main ship that would power the magnetic sails.
“Superconducting current can be created once before launch and it will flow forever,” says Gros. This technology could certainly last long enough for a mission to a relatively nearby star like TRAPPIST-1 to take place.
Gross estimates that a 1.5-ton vessel, carrying the superconducting infrastructure for a 50-kilometer-wide sail, could reach TRAPPIST-1 in 12,000 years if accelerated by Breakthrough lasers.
Jeff Kuhn, Starshot advisor and physicist at the University of Hawaii, endorses Gross's work but expresses concern that securing support and funding for a mission that takes 12,000 years will be more difficult than building and launching one.
Ilya Khel