Future spacecraft can use black holes as powerful launch platforms for studying stars. A new study involves the launch of laser beams from a ship around the edge of a black hole that will bend around the latter due to its powerful gravity and return with added energy. After this, the ship will "catch" such rays and thereby obtain free energy that can be spent on its acceleration up to the speed of light. Astronomers could search for signals that alien civilizations such as & # 39; n & # 39; halo drive & # 39; use, as the researchers call it, by observing how pairs of black holes merge faster than expected through calculations.
The author of the study, David Kipping, an astrophysicist at Columbia University in New York, has suggested the idea of a halo drive with what he & # 39; player-thinking & # 39; calls.
"Sometimes you discover an exploit in a computer game, a hack with which you can do something extra-standard, which under normal circumstances is impossible according to the rules of the game," Kipping said. "In this case, the game is the physical world, and I tried to think about concepts that would allow civilizations to make a relativistic flight back and forth through the galaxy without the huge amount of energy needed to do this now to do."
The biggest problem with using rockets to fly into space is that the fuel they carry has mass. On long journeys you need a lot of fuel, making the rockets heavy, which in turn requires even more fuel, making the rockets even heavier and so on. This problem decreases exponentially, the bigger the rocket gets.
Instead of accelerating fuel, a spacecraft equipped with mirror sails could count on lasers to get ahead. The $ 100 million breakthrough Starshot initiative, announced in 2016, plans to use high-power lasers to deliver a large number of small spacecraft to the Alpha Centauri star located on the nearest star system on 4 light years away, up to 20% the speed of light.
Each spaceship launched as part of the Breakthrough Starshot project is comparable in size to a microchip. To accelerate large spaceships to relativistic speeds – to a significant part of the speed of light – Kipping seeks help with gravity.
An example of a gravitational maneuver using the moon (gray circle). The yellow arrow indicates the direction of the sun.
Spaceships now regularly use "space catapults" maneuvers in which those who fly along a certain trajectory near massive space objects, such as planets, get extra acceleration due to the latter's enormous gravity. In 1963, the famous physicist Freeman Dyson (the one who invented the Dyson sphere – the mega-structure in which the star is enclosed, providing maximum energy for the needs of a developed civilization) suggested that spacecraft of all sizes could rely on catapults around compact pairs of white dwarfs or neutron stars to fly at relative speeds.
Dyson & Slingshot, however, risks damaging the spacecraft through extreme gravitational forces and dangerous radiation from these pairs of dead stars. Instead, Kipping suggests that gravity can help spacecraft by increasing the energy of laser beams fired at the edges of black holes.
Black holes have gravitational fields that are so powerful that nothing can escape from them, even light. Their gravitational fields can also distort the paths of the photons of light that fly next to it. In 1993, physicist Mark Stakey suggested that a black hole can in principle act as a "gravity mirror", because the gravity of a black hole can rotate a photon around itself, so that it flies back to its source. Kipping estimated that if a black hole moves to the source of photons, the "boomerang photon" will receive some of the energy from the black hole.
He calculated the physics of what he called a & # 39; halo drive & # 39; named – the name comes from the light ring, the halo that would make a laser beam around a black hole – Kipping discovered that even spacecraft with the mass of Jupiter can achieve relativistic speeds. "Civilization can use black holes as galactic waypoints," he wrote in a study that was accepted by the British Interplanetary Society.
The faster the black hole moves, the more energy can be extracted from it. So Kipping focused primarily on the use of pairs of black holes that turned towards each other until they fused together.
Astronomers can look for signals that alien civilizations use pairs of black holes to travel with such a motor. Halo motors, for example, would effectively "steal" energy from black hole binary systems, making the merging speed faster than what one would naturally expect, Kipping said.
His conclusions were based on impulses from pairs of black holes circling around each other at relativistic speeds. Although there are around 10 million pairs of black holes in the Milky Way, Kipping noted that only a few of them are likely to rotate at relativistic speeds for a long time, because at such speeds the merging usually occurs fairly quickly.
However, he noted that isolated rotating black holes can also speed a ship with a halo drive to relativistic speeds, "and we already know about countless examples of super-heavy black holes rotating at a relativistic speed."
The main disadvantage of the halo drive is that "you have to go to the nearest black hole," said Kipping. "It looks like a one-off rate for a toll road. You have to spend some energy to get to the nearest access point, but after that you can drive for free as long as you want."
The halo drive only works in the vicinity of a black hole, at a distance of about five to fifty times its diameter. "That's why you first have to go to the nearest black hole, and [почему вы] you can't just do it for the light years of hair, "Kipping said." To begin with, we still need the resources to get to the nearest black hole. "
"If we want to make a relativistic flight, huge energy costs are required regardless of the propulsion system that you use," he added. "One of the ways to get around this is to use astronomical objects as energy sources, because they literally have astronomical energy supplies. In this case, a few black holes are actually a giant battery, waiting for us to use it. The idea is to work with nature, not against it. "
Kipping is exploring ways to use other astronomical systems for relativistic flights. Such methods "may not be as efficient or as fast as flying with a halo drive, but these systems need large energy reserves for these journeys," Kipping said.